CROSS REFERENCE

[0001] The present Application for Patent claims the benefit of Greece Provisional Patent Application No. 20190100534 by MANOLAKOS et al., entitled “DEMODULATION REFERENCE SIGNAL BUNDLING,” filed November 26, 2019, assigned to the assignee hereof, and expressly incorporated by reference herein.

FIELD OF TECHNOLOGY

[0002] The present disclosure relates generally to wireless communications and more specifically to demodulation reference signal bundling.

BACKGROUND

[0003] Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple- access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM). A wireless multiple-access communications system may include one or more base stations or one or more network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).

[0004] In some wireless communications systems, data transmissions from a transmitting device may be demodulated at a receiving device based on reference signals (e.g., demodulation reference signals) that accompany the data transmissions. In some cases, receiving or decoding demodulation reference signals may be associated with overhead at the transmitting device or the receiving device, or may be associated with some degree of inaccuracy or uncertainty at the receiving device.

SUMMARY

[0005] The described techniques relate to improved methods, systems, devices, and apparatuses that support demodulation reference signal bundling. In some wireless communications systems, data transmissions by a transmitting device may be accompanied by demodulation reference signals, which may be used by a receiving device to support demodulating or otherwise decoding the data transmissions. The transmitting device and the receiving device may each use a precoding configuration, which may be negotiated or otherwise communicated between the transmitting device and the receiving device. Aspects of the precoding configuration may support encoding the data transmission by the transmitting device and decoding the encoded data transmission by the receiving device. In some cases, techniques for bundling of demodulation reference signals may be supported, and the receiving device may assume (e.g., be configured to assume) that the same precoder is used by the transmitting device across the data channels of different scheduling units. For example, when demodulation reference signals are coherently transmitted over different time intervals, or via different antenna ports, demodulation reference signals over different time instants or antenna ports can be coherently filtered or otherwise processed by the receiving device to enhance the accuracy or efficiency of channel estimation for physical channel transmissions.

[0006] In some examples, a receiving device may be configured to assume that a phase rotation (e.g., shift) relationship, an amplitude scaling relationship, or both, exist between reference signals (e.g., of different scheduling units). In one example, the receiving device may be configured to assume that, for a given antenna port, a phase rotation or amplitude scaling (e.g., as applied by a transmitting device for a given transmission) is the same between transmission time intervals (TTIs), or is within a threshold difference from one TTI to another. In another example, a receiving device may assume that, between transmission time intervals, a phase rotation or amplitude scaling between two antenna ports is the same, or is within a threshold difference. A configuration to apply such assumptions may improve channel estimation by the receiving device, such as improving a fidelity of channel estimation, or reducing computational or signaling overhead to support channel estimation, among other benefits.

[0007] A method for wireless communication at a UE is described. The method may include receiving, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval, receiving, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval, identifying that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval, and performing a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port.

[0008] An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval, receive, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval, identify that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval, and perform a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port.

[0009] Another apparatus for wireless communication at a UE is described. The apparatus may include means for receiving, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval, means for receiving, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval, means for identifying that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval, and means for performing a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port.

[0010] A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to receive, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval, receive, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval, identify that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval, and perform a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port.

[0011] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, may be the phase rotation relationship.

[0012] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, may be the amplitude scaling relationship.

[0013] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, performing the channel estimation for the antenna port may include operations, features, means, or instructions for scaling a received signal of the second transmission time interval by a first amplitude relative to the first transmission time interval, and rotating the received signal of the second transmission time interval by a first phase rotation relative to the first transmission time interval. [0014] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the first amplitude and the first phase rotation may be unknown to a transmitter of the first demodulation reference signal and the second demodulation reference signal.

[0015] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for scaling, for the second antenna port, the received signal of the second transmission time interval by a second amplitude relative to the first transmission time interval, and rotating, for the second antenna port, the received signal of the second transmission time interval by a second phase rotation relative to the first transmission time interval.

[0016] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, an absolute value of a difference between the first phase rotation and the second phase rotation may be assumed by the UE to be constant to perform the channel estimation for the antenna port and perform the second channel estimation for the second antenna port.

[0017] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, an absolute value of a difference between the first phase rotation and the second phase rotation may be assumed by the UE to be less than or equal to a threshold value to perform the channel estimation for the antenna port and performing the second channel estimation for the second antenna port.

[0018] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving an indication of a configuration for reference signal bundling, and identifying that the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval may be based on the indicated configuration for reference signal bundling.

[0019] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting an indication that reference signal bundling may be supported by the UE, where the configuration for reference signal bundling may be responsive to the indication that reference signal bundling may be supported.

[0020] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, via a second antenna port, a third demodulation reference signal of a third transmission on the physical channel during the first transmission time interval, identifying that a second phase rotation relationship, or a second amplitude scaling relationship, or a combination thereof, exists between the antenna port of the physical channel and the second antenna port of the physical channel, and performing a second channel estimation for the second antenna port of the physical channel for the second transmission time interval based on the received second demodulation reference signal and the second phase rotation relationship, or the second amplitude scaling relationship, or the combination thereof, between the antenna port of the physical channel and the second antenna port of the physical channel.

[0021] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the second phase rotation relationship, or the second amplitude scaling relationship, or the combination thereof, may be the second phase rotation relationship.

[0022] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the second phase rotation relationship, or the second amplitude scaling relationship, or the combination thereof, may be the second amplitude scaling relationship.

[0023] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the phase rotation relationship for the antenna port of the physical channel and the second phase rotation relationship for the second antenna port of the physical channel indicates a same phase rotation and a same amplitude scaling for all antenna ports between the first transmission time interval and the second transmission time interval.

[0024] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, via the second antenna port, a fourth demodulation reference signal of a fourth transmission on the physical channel during the second transmission time interval, and performing the channel estimation for the antenna port of the physical channel for the second transmission time interval based on the received fourth demodulation reference signal and the second phase rotation relationship between the antenna port of the physical channel and the second antenna port of the physical channel.

[0025] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, identifying that the phase rotation relationship exists may include operations, features, means, or instructions for determining that a duration between the first transmission time interval and the second transmission time interval satisfies a threshold.

[0026] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, identifying that the phase rotation relationship exists may include operations, features, means, or instructions for determining that transmission time intervals between the first transmission time interval and the second transmission time interval may be not configured for uplink transmission.

[0027] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, identifying that the phase rotation relationship exists may include operations, features, means, or instructions for determining that the first transmission time interval and the second transmission time interval may be associated with a same on duration or active time of a discontinuous reception configuration.

[0028] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, identifying that the phase rotation relationship exists may include operations, features, means, or instructions for determining that an uplink transmission may have not been transmitted between the first transmission time interval and the second transmission time interval.

[0029] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, identifying that the phase rotation relationship exists may include operations, features, means, or instructions for determining that the first transmission and the second transmission may be associated with a same component carrier, or different component carriers of a same frequency band. [0030] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for decoding the second transmission based on performing the channel estimation for the physical channel for the second transmission time interval.

[0031] A method for wireless communication is described. The method may include receiving, from a UE, an indication that the UE supports reference signal bundling, transmitting, to the UE and based on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals, and transmitting, to the UE on the physical channel and based on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval.

[0032] An apparatus for wireless communication is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive, from a UE, an indication that the UE supports reference signal bundling, transmit, to the UE and based on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals, and transmit, to the UE on the physical channel and based on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval.

[0033] Another apparatus for wireless communication is described. The apparatus may include means for receiving, from a UE, an indication that the UE supports reference signal bundling, means for transmitting, to the UE and based on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals, and means for transmitting, to the UE on the physical channel and based on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval.

[0034] A non-transitory computer-readable medium storing code for wireless communication is described. The code may include instructions executable by a processor to receive, from a UE, an indication that the UE supports reference signal bundling, transmit, to the UE and based on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals, and transmit, to the UE on the physical channel and based on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval.

[0035] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, transmitting the first demodulation reference signal and the second demodulation reference signal may include operations, features, means, or instructions for transmitting the first demodulation reference signal via the antenna port during the first transmission time interval, and transmitting the second demodulation reference signal via the antenna port during the second transmission time interval.

[0036] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the indication that the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, indicates that the phase rotation relationship exists between antenna ports, the method further including transmitting, to the UE on the physical channel and based on the received indication, the first demodulation reference signal via the antenna port and a third demodulation reference signal via a second antenna port during the first transmission time interval.

[0037] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that a duration between the first transmission time interval and the second transmission time interval satisfies a threshold, where transmitting the second demodulation reference signal may be based on the determining. [0038] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that one or more transmission time intervals between the first transmission time interval and the second transmission time interval may be not configured for uplink transmission, where transmitting the second demodulation reference signal may be based on the determining.

[0039] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the first transmission time interval and the second transmission time interval may be associated with a same on duration or active time of a discontinuous reception configuration of the UE, where transmitting the second demodulation reference signal may be based on the determining.

[0040] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that the UE may have not transmitted an uplink transmission between the first transmission time interval and the second transmission time interval, where transmitting the second demodulation reference signal may be based on the determining.

[0041] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the first transmission and the second transmission may be associated with a same component carrier, or different component carriers of a same frequency band.

[0042] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the physical channel is a downlink channel. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the physical channel is a sidelink channel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 illustrates an example of a system for wireless communications that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. [0044] FIG. 2 illustrates an example of a wireless communications system that supports demodulation reference signal bundling in accordance with aspects of the present disclosure.

[0045] FIG. 3 illustrates an example of a wireless communications system and corresponding operations that support demodulation reference signal bundling in accordance with aspects of the present disclosure.

[0046] FIGs. 4 and 5 show block diagrams of devices that support demodulation reference signal bundling in accordance with aspects of the present disclosure.

[0047] FIG. 6 shows a block diagram of a communication manager that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. [0048] FIG. 7 shows a diagram of a system including a device that supports demodulation reference signal bundling in accordance with aspects of the present disclosure.

[0049] FIGs. 8 and 9 show block diagrams of devices that support demodulation reference signal bundling in accordance with aspects of the present disclosure.

[0050] FIG. 10 shows a block diagram of a communication manager that supports demodulation reference signal bundling in accordance with aspects of the present disclosure.

[0051] FIG. 11 shows a diagram of a system including a user equipment (UE) that supports demodulation reference signal bundling in accordance with aspects of the present disclosure.

[0052] FIG. 12 shows a diagram of a system including a base station that supports demodulation reference signal bundling in accordance with aspects of the present disclosure.

[0053] FIGs. 13 through 16 show flowcharts illustrating methods that support demodulation reference signal bundling in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

[0054] The described techniques relate to improved methods, systems, devices, and apparatuses that support demodulation reference signal bundling. In some wireless communications systems, data transmissions by a transmitting device may be accompanied by demodulation reference signals, which may be used by a receiving device to support demodulating or otherwise decoding the data transmissions. The transmitting device and the receiving device may each use a precoding configuration, which may be negotiated or otherwise communicated between the transmitting device and the receiving device. Aspects of the precoding configuration may support encoding the data transmission by the transmitting device and decoding the encoded data transmission by the receiving device. In some cases, techniques for bundling of demodulation reference signals may be supported, and the receiving device may assume (e.g., be configured to assume) that the same precoder is used by a transmitting device across the data channels of different scheduling units. For example, when demodulation reference signals are coherently transmitted over different time intervals or different antenna ports, demodulation reference signals over different time instants or antenna ports can be coherently filtered or otherwise processed by a receiving device to enhance the accuracy or efficiency of channel estimation for physical channel transmissions.

[0055] In some examples, a receiving device may be configured to assume that a phase shift relationship, an amplitude scaling relationship, or both, exist between reference signals (e.g., of different scheduling units). In one example, the receiving device may be configured to assume that, for a given antenna port, a phase rotation or amplitude scaling is the same between transmission time intervals (TTIs), or is within a threshold difference from one TTI to another. In another example, a receiving device may assume that, between transmission time intervals, a phase rotation or amplitude scaling between two antenna ports is the same, or is within a threshold difference. A configuration to apply such assumptions may improve channel estimation by the receiving device, such as improving a fidelity of channel estimation, or reducing computational or signaling overhead to support channel estimation, among other benefits.

[0056] Aspects of the disclosure are initially described in the context of wireless communications systems and corresponding operations that support demodulation reference signal bundling. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to demodulation reference signal bundling.

[0057] FIG. 1 illustrates an example of a wireless communications system 100 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The wireless communications system 100 may include one or more base stations 105, one or more UEs 115, and a core network 130. In some examples, the wireless communications system 100 may be a Long Term Evolution (LTE) network, an LTE- Advanced (LTE- A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communications system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof.

[0058] The base stations 105 may be dispersed throughout a geographic area to form the wireless communications system 100 and may be devices in different forms or having different capabilities. The base stations 105 and the UEs 115 may wirelessly communicate via one or more communication links 125. Each base station 105 may provide a coverage area 110 over which the UEs 115 and the base station 105 may establish one or more communication links 125. The coverage area 110 may be an example of a geographic area over which a base station 105 and a UE 115 may support the communication of signals according to one or more radio access technologies.

[0059] The UEs 115 may be dispersed throughout a coverage area 110 of the wireless communications system 100, and each UE 115 may be stationary, or mobile, or both at different times. The UEs 115 may be devices in different forms or having different capabilities. Some example UEs 115 are illustrated in FIG. 1. The UEs 115 described herein may be able to communicate with various types of devices, such as other UEs 115, the base stations 105, or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment), as shown in FIG. 1.

[0060] The base stations 105 may communicate with the core network 130, or with one another, or both. For example, the base stations 105 may interface with the core network 130 through one or more backhaul links 120 (e.g., via an SI, N2, N3, or other interface). The base stations 105 may communicate with one another over the backhaul links 120 (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations 105), or indirectly (e.g., via core network 130), or both. In some examples, the backhaul links 120 may be or include one or more wireless links.

[0061] One or more of the base stations 105 described herein may include or may be referred to by a person having ordinary skill in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next- generation NodeB or a giga-NodeB (either of which may be referred to as a gNB), a Home NodeB, a Home eNodeB, or other suitable terminology.

[0062] A UE 115 may include or may be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client, among other examples. A UE 115 may also include or may be referred to as a personal electronic device such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, a UE 115 may include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communications (MTC) device, among other examples, which may be implemented in various objects such as appliances, or vehicles, meters, among other examples.

[0063] The UEs 115 described herein may be able to communicate with various types of devices, such as other UEs 115 that may sometimes act as relays as well as the base stations 105 and the network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, among other examples, as shown in FIG. 1.

[0064] The UEs 115 and the base stations 105 may wirelessly communicate with one another via one or more communication links 125 over one or more carriers. The term “carrier” may refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting the communication links 125. For example, a carrier used for a communication link 125 may include a portion of a radio frequency spectrum band (e.g., a bandwidth part (BWP)) that is operated according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel may carry acquisition signaling (e.g., synchronization signals, system information), control signaling that coordinates operation for the carrier, user data, or other signaling. The wireless communications system 100 may support communication with a UE 115 using carrier aggregation or multi-carrier operation. A UE 115 may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers. [0065] In some examples (e.g., in a carrier aggregation configuration), a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers.

A carrier may be associated with a frequency channel (e.g., an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute radio frequency channel number (EARFCN)) and may be positioned according to a channel raster for discovery by the UEs 115. A carrier may be operated in a standalone mode where initial acquisition and connection may be conducted by the UEs 115 via the carrier, or the carrier may be operated in a non- standalone mode where a connection is anchored using a different carrier (e.g., of the same or a different radio access technology).

[0066] The communication links 125 shown in the wireless communications system 100 may include uplink transmissions from a UE 115 to a base station 105, or downlink transmissions from a base station 105 to a UE 115. Carriers may carry downlink or uplink communications (e.g., in an FDD mode) or may be configured to carry downlink and uplink communications (e.g., in a TDD mode).

[0067] A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system 100. For example, the carrier bandwidth may be one of a number of determined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz (MHz)). Devices of the wireless communications system 100 (e.g., the base stations 105, the UEs 115, or both) may have hardware configurations that support communications over a particular carrier bandwidth or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system 100 may include base stations 105 or UEs 115 that support simultaneous communications via carriers associated with multiple carrier bandwidths. In some examples, each served UE 115 may be configured for operating over portions (e.g., a sub-band, a BWP) or all of a carrier bandwidth.

[0068] Signal waveforms transmitted over a carrier may be made up of multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT- S-OFDM)). In a system employing MCM techniques, a resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both). Thus, the more resource elements that a UE 115 receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE 115. A wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers or beams), and the use of multiple spatial layers may further increase the data rate or data integrity for communications with a UE 115.

[0069] One or more numerologies for a carrier may be supported, where a numerology may include a subcarrier spacing (D/) and a cyclic prefix. A carrier may be divided into one or more BWPs having the same or different numerologies. In some examples, a UE 115 may be configured with multiple BWPs. In some examples, a single BWP for a carrier may be active at a given time and communications for the UE 115 may be restricted to one or more active BWPs.

[0070] The time intervals for the base stations 105 or the UEs 115 may be expressed in multiples of a basic time unit which may, for example, refer to a sampling period of T _s =

1 /{ f _{max '} Nf) seconds, where A/ _ma may represent the maximum supported subcarrier spacing, and JV- may represent the maximum supported discrete Fourier transform (DFT) size. Time intervals of a communications resource may be organized according to radio frames each having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023).

[0071] Each frame may include multiple consecutively numbered subframes or slots, and each subframe or slot may have the same duration. In some examples, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into a number of slots. Alternatively, each frame may include a variable number of slots, and the number of slots may depend on subcarrier spacing. Each slot may include a number of symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period). In some wireless communications systems 100, a slot may further be divided into multiple mini-slots containing one or more symbols. Excluding the cyclic prefix, each symbol period may contain one or more (e.g., Nf) sampling periods. The duration of a symbol period may depend on the subcarrier spacing or frequency band of operation. [0072] A subframe, a slot, a mini-slot, or a symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system 100 and may be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system 100 may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)).

[0073] Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may be multiplexed on a downlink carrier, for example, using one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET)) for a physical control channel may be defined by a number of symbol periods and may extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESETs) may be configured for a set of the UEs 115. For example, one or more of the UEs 115 may monitor or search control regions for control information according to one or more search space sets, and each search space set may include one or multiple control channel candidates in one or more aggregation levels arranged in a cascaded manner. An aggregation level for a control channel candidate may refer to a number of control channel resources (e.g., control channel elements (CCEs)) associated with encoded information for a control information format having a given payload size. Search space sets may include common search space sets configured for sending control information to multiple UEs 115 and UE-specific search space sets for sending control information to a specific UE 115.

[0074] Each base station 105 may provide communication coverage via one or more cells, for example a macro cell, a small cell, a hot spot, or other types of cells, or any combination thereof. The term “cell” may refer to a logical communication entity used for communication with a base station 105 (e.g., over a carrier) and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID), or others). In some examples, a cell may also refer to a geographic coverage area 110 or a portion of a geographic coverage area 110 (e.g., a sector) over which the logical communication entity operates. Such cells may range from smaller areas (e.g., a structure, a subset of structure) to larger areas depending on various factors such as the capabilities of the base station 105. For example, a cell may be or include a building, a subset of a building, or exterior spaces between or overlapping with geographic coverage areas 110, among other examples.

[0075] In some examples, a base station 105 may be movable and therefore provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, but the different geographic coverage areas 110 may be supported by the same base station 105. In other examples, the overlapping geographic coverage areas 110 associated with different technologies may be supported by different base stations 105. The wireless communications system 100 may include, for example, a heterogeneous network in which different types of the base stations 105 provide coverage for various geographic coverage areas 110 using the same or different radio access technologies.

[0076] The wireless communications system 100 may be configured to support ultra reliable communications or low-latency communications, or various combinations thereof. For example, the wireless communications system 100 may be configured to support ultra reliable low-latency communications (URLLC) or mission critical communications. The UEs 115 may be designed to support ultra-reliable, low-latency, or critical functions (e.g., mission critical functions). Ultra-reliable communications may include private communication or group communication and may be supported by one or more mission critical services such as mission critical push-to-talk (MCPTT), mission critical video (MCVideo), or mission critical data (MCData). Support for mission critical functions may include prioritization of services, and mission critical services may be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, mission critical, and ultra-reliable low- latency may be used interchangeably herein.

[0077] In some examples, a UE 115 may also be able to communicate directly with other UEs 115 over a device-to-device (D2D) communication link 135 (e.g., using a peer-to-peer (P2P) or D2D protocol). One or more UEs 115 utilizing D2D communications may be within the geographic coverage area 110 of a base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of a base station 105 or be otherwise unable to receive transmissions from a base station 105. In some examples, groups of the UEs 115 communicating via D2D communications may utilize a one-to-many (1 :M) system in which each UE 115 transmits to every other UE 115 in the group. In some examples, a base station 105 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between the UEs 115 without the involvement of a base station 105.

[0078] In some systems, the D2D communication link 135 may be an example of a communication channel, such as a sidelink communication channel, between vehicles (e.g., UEs 115). In some examples, vehicles may communicate using vehicle-to-everything (V2X) communications, vehicle-to-vehicle (V2V) communications, or some combination of these. A vehicle may signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information relevant to a V2X system. In some examples, vehicles in a V2X system may communicate with roadside infrastructure, such as roadside units, or with the network via one or more network nodes (e.g., base stations 105) using vehicle-to-network (V2N) communications, or with both.

[0079] The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC) or 5G core (5GC), which may include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), or a user plane function (UPF)). The control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management for the UEs 115 served by the base stations 105 associated with the core network 130. User IP packets may be transferred through the user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to the network operators IP services 150. The operators IP services 150 may include access to the Internet, Intranet(s), an IP Multimedia Subsystem (IMS), or a Packet- Switched Streaming Service.

[0080] Some of the network devices, such as a base station 105, may include subcomponents such as an access network entity 140, which may be an example of an access node controller (ANC). Each access network entity 140 may communicate with the UEs 115 through one or more other access network transmission entities 145, which may be referred to as radio heads, smart radio heads, or transmission/reception points (TRPs). Each access network transmission entity 145 may include one or more antenna panels. In some configurations, various functions of each access network entity 140 or base station 105 may be distributed across various network devices (e.g., radio heads and ANCs) or consolidated into a single network device (e.g., a base station 105).

[0081] The wireless communications system 100 may operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band because the wavelengths range from approximately one decimeter to one meter in length. The UHF waves may be blocked or redirected by buildings and environmental features, but the waves may penetrate structures sufficiently for a macro cell to provide service to the UEs 115 located indoors. The transmission of UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz.

[0082] The wireless communications system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communications system 100 may employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz industrial, scientific, and medical (ISM) band. When operating in unlicensed radio frequency spectrum bands, devices such as the base stations 105 and the UEs 115 may employ carrier sensing for collision detection and avoidance. In some examples, operations in unlicensed bands may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (e.g., LAA). Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among other examples.

[0083] A base station 105 or a UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of a base station 105 or a UE 115 may be located within one or more antenna arrays or antenna panels, which may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some examples, antennas or antenna arrays associated with a base station 105 may be located in diverse geographic locations. A base station 105 may have an antenna array with a number of rows and columns of antenna ports that the base station 105 may use to support beamforming of communications with a UE 115. Likewise, a UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations. Additionally or alternatively, an antenna panel may support radio frequency beamforming for a signal transmitted via an antenna port.

[0084] The base stations 105 or the UEs 115 may use MIMO communications to exploit multipath signal propagation and increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas, either of which may be referred to as, or otherwise associated with, antenna ports. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas, either of which may be also be referred to as, or otherwise associated with, antenna ports. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords). Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single- user MIMO (SU-MIMO), where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO), where multiple spatial layers are transmitted to multiple devices.

[0085] Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station 105, a UE 115) to shape or steer an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that some signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying amplitude offsets, phase offsets, or both to signals carried via the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation).

[0086] Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station 105 in a single beam direction (e.g., a direction associated with the receiving device, such as a UE 115). In some examples, the beam direction associated with transmissions along a single beam direction may be determined based on a signal that was transmitted in one or more beam directions. For example, a UE 115 may receive one or more of the signals transmitted by the base station 105 in different directions and may report to the base station 105 an indication of the signal that the UE 115 received with a highest signal quality or an otherwise acceptable signal quality.

[0087] In some examples, transmissions by a device (e.g., by a base station 105 or a UE 115) may be performed using multiple beam directions, and the device may use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmission (e.g., from a base station 105 to a UE 115). The UE 115 may report feedback that indicates precoding weights for one or more beam directions, and the feedback may correspond to a configured number of beams across a system bandwidth or one or more sub-bands. The base station 105 may transmit a reference signal (e.g., a cell-specific reference signal (CRS), a channel state information reference signal (CSI-RS)), which may be precoded or unprecoded. The UE 115 may provide feedback for beam selection, which may be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, a port selection type codebook). Although these techniques are described with reference to signals transmitted in one or more directions by a base station 105, a UE 115 may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE 115) or for transmitting a signal in a single direction (e.g., for transmitting data to a receiving device).

[0088] A receiving device (e.g., a UE 115) may try multiple receive configurations (e.g., directional listening) when receiving various signals from the base station 105, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive configurations or receive directions. In some examples, a receiving device may use a single receive configuration to receive along a single beam direction (e.g., when receiving a data signal). The single receive configuration may be aligned in a beam direction determined based on listening according to different receive configuration directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio (SNR), or otherwise acceptable signal quality based on listening according to multiple beam directions).

[0089] The wireless communications system 100 may be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP -based. A Radio Link Control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use error detection techniques, error correction techniques, or both to support retransmissions at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or a core network 130 supporting radio bearers for user plane data. At the physical layer, transport channels may be mapped to physical channels.

[0090] Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). A wireless network, for example a wireless local area network (WLAN), such as a Wi-Fi (i.e., Institute of Electrical and Electronics Engineers (IEEE) 802.11) network may include an access point (AP) that may communicate with one or more wireless or mobile devices. The AP may be coupled to a network, such as the Internet, and may enable a mobile device to communicate via the network (or communicate with other devices coupled to the access point). A wireless device may communicate with a network device bi-directionally. For example, in a WLAN, a device may communicate with an associated AP via downlink (e.g., the communication link from the AP to the device) and uplink (e.g., the communication link from the device to the AP). A wireless personal area network (PAN), which may include a Bluetooth connection, may provide for short range wireless connections between two or more paired wireless devices. For example, wireless devices such as cellular phones may utilize wireless PAN communications to exchange information such as audio signals with wireless headsets.

[0091] An antenna port may be a logical entity (e.g., rather than a physical antenna) and may be defined such that the channel over which a symbol on the antenna port is conveyed can be inferred from the channel over which another symbol on the same antenna port is conveyed. Generally, there may be one resource grid per antenna port, and the set of antenna ports supported may depend on the reference signal configuration in the cell.

[0092] A receiver (e.g., a UE 115 receiving downlink data or control signals) may need to know which assumptions the UE 115 can make on the channel corresponding to different transmissions. For example, the receiver needs to know which reference signal transmission the receiver can use to estimate the channel in order to decode a transmitted signal.

Generally, a receiver can assume that two transmissions correspond to the same radio channel if they use the same antenna port.

[0093] An antenna port may be defined by a transmitted reference signal (e.g., a demodulation reference signal for downlink transmissions). The reference signal could have been transmitted from a single physical antenna element or using a beam-former applied on a subarray of elements. In some examples, two signals may be transmitted using the same physical antennas but correspond to different antenna ports if the two signals are beam- formed with different weights, for example because the corresponding effective channels are different. The receiver can use a reference signal (e.g., the demodulation reference signal) transmitted on an antenna port to estimate the channel for this antenna port. This channel estimate can subsequently be used for decoding data transmitted on the same antenna port. For example, the demodulation reference signal may be used for channel estimation to decode data transmitted on the same antenna port.

[0094] Two antenna ports are said to be quasi-co-located (QCLed) if properties of the channel over which a symbol on one antenna port is conveyed can be inferred from the channel over which a symbol on the other antenna port is conveyed. For example, an antenna port relates to the channel, while the QCL refers to the properties of the channel. As such, QCL may be a less stringent requirement than an antenna port since the properties of the channel and not the channel itself need to be the same for quasi-co-located antenna ports. If two signals have been transmitted on two closely spaced, but different, antennas, they could experience different channels due to fading but the large-scale properties of the two channels may be the same. Thus, the two antennas may be different antenna ports but they would be quasi-collocated. Large-scale properties include, for example, second-order statistics of the channel such as delay or Doppler spread, average channel gain, and so on. Such information may be useful to the UE for performing channel estimation.

[0095] In some examples, data transmissions (e.g., downlink or sidelink data transmissions, for example on a downlink or sidelink physical channel) by a transmitting device of the wireless communications system 100 may be accompanied by demodulation reference signals, which may be used by a receiving device of the wireless communications system 100 to support demodulating or otherwise decoding the data transmissions. In some cases, techniques for bundling of demodulation reference signals may be supported, and the receiving device may assume (e.g., be configured to assume) that the same precoder is used by a transmitting device across the data channels of different scheduling units (e.g., different TTIs, different antenna ports). Thus, when demodulation reference signals are coherently transmitted over different time intervals or via different antenna ports, demodulation reference signals over different time instants or antenna ports can be coherently filtered by the receiving device to enhance the accuracy of channel estimation for physical channel transmissions (e.g., data transmissions).

[0096] FIG. 2 illustrates an example of a wireless communications system 200 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. In some examples, the wireless communications system 200 may implement aspects of the wireless communications system 100 The wireless communications system 200 may include a transmitting device, illustrated as a base station 105-a, and a receiving device, illustrated as a UE 115-a. However, in some examples, a transmitting device may include another UE 115, such as when the described operations relate to D2D or sidelink communications between UEs 115. Moreover, in some examples, a receiving device may include a base station 105, such as when the described operations relate to uplink communications from a UE 115 to a base station 105.

[0097] The wireless communications system 200 illustrates an example of communications that may be supported by multiple antenna ports, such as transmission by the base station 105-a via multiple antenna ports, and reception by the UE 115-a via multiple antenna ports. Each antenna port may support communicating an orthogonal data stream over a different spatial resource, which may correspond to different antennas, different combinations of antennas, different transmission or reception beams, different signal propagation paths, and other definitions or descriptions of different spatial resources. For example, the base station 105-a may be configured to transmit a first transmission over a first antenna port (e.g., a first antenna, a first combination of antennas, a first beam direction, a first spatial resource), which may include a demodulation reference signal 205-a and a corresponding data transmission 210-a. The base station 105-a may also be configured to transmit a second transmission over a second antenna port (e.g., a second antenna, a second combination of antennas, a second beam direction, a second spatial resource), which may include a demodulation reference signal 205-b and a corresponding data transmission 210-b. In some examples, the data transmissions 210 may refer to physical transmissions (e.g., different physical channel transmissions, different instances of physical transmissions), and the data transmission 210-a may or may not be a same physical channel, or type of physical channel, as the data transmission 210-b. In some examples, the data transmission 210-a and the data transmission 210-b may be a PDSCH transmission.

[0098] The use of different spatial resources may support an orthogonality of the first transmission and the second transmission, such that the UE 115-a may separately receive and decode the first transmission and the second transmission, even when the first transmission and the second transmission use communication resources that overlap in the time domain (e.g., a same TTI, a same symbol period) and overlap in the frequency domain (e.g., a same component carrier). For example, the UE 115-a may receive the demodulation reference signal 205-a, and identify a phase rotation and amplitude scaling for demodulating or decoding the data transmission 210-a based on the demodulation reference signal 205-a. The UE 115-a may receive the demodulation reference signal 205-b, and identify a phase rotation and amplitude scaling for demodulating or decoding the data transmission 210-b based on the demodulation reference signal 205-b. Such calculations may be included in a process described as a channel estimation process, or estimating a channel (e.g., a physical channel) corresponding to a respective data transmission 210.

[0099] In some examples, an antenna port may be defined such that the physical channel over which a modulation symbol on the antenna port is conveyed can be inferred from the physical channel over which another modulation symbol on the same antenna port is conveyed. In one example, for a demodulation reference signal associated with a physical channel transmission, such as a PDSCH, the physical channel over which a PDSCH modulation symbol on one antenna port is conveyed can be inferred from the physical channel over which a demodulation reference signal symbol on the same antenna port is conveyed if the two modulation symbols are within the same resource as the scheduled PDSCH, in the same slot period, and in the same physical resource group. However, other techniques related to reference signal bundling and channel estimation may be employed to improve channel estimation efficiency and accuracy.

[0100] In one example, a matrix may be an example of an unprecoded channel matrix (e.g., on the downlink) for a resource element where the dimensions of matrix Hi may be given by a number of antenna ports at a receiving device, such as the UE 115-a (e.g., N _UE ) by a number of antenna ports at a transmitting device, such as the base station 105-a (e.g., N _BS ). In other words, the matrix may be an N _UE -by-N _BS channel matrix, which may be understood by both the base station 105-a and the UE 115-a. For two PDSCH transmissions (e.g., data transmission 210-a and data transmission 210-b) with a rank i^, transmit precoders may be given as respectively with u _± < min ( N _UE ,N _BS ). In some cases (e.g., related to signaling calibration issues at the base station 105-a), the base station 105-a may not be able to ensure that the transmit precoders P^ and are equal, or that the transmit precoders reasonably similar, for the UE 115-a to directly exploit bundling of demodulation reference signals (e.g., joint decoding using the demodulation reference signal 205-a and the demodulation reference signal 205-b) across the two PDSCH transmissions. [0101] For example, a diagonal matrix, D _j , referring to signal amplitudes, a, and phase angles, ø, on different antenna ports may be given by the following:

To denote unknown amplitude and phase differences between two precoded channels, the following relationships may be considered: y = H x + v y = H _t PPx + v, (2) such that PP = D, P [0102] In some cases, if the matrix D _t does not have a suitable structure, the UE 115-a may not be able to infer one PDSCH transmission from the demodulation reference signal of another PDSCH transmission (e.g., inferring the data transmission 210-b from the demodulation reference signal 205-a, inferring the data transmission 210-a from the demodulation reference signal 205-b, inferring a data transmission of one TTI from a demodulation reference signal of a different TTI). For example, according to certain bundling techniques (e.g., strong bundling techniques), the diagonal matrix D _j may be a unit diagonal matrix (e.g., D _L = 1), or may be otherwise ignored or not configured, corresponding to a relationship of PP = Pp . However, such an approach may limit inferences that could be made by the UE 115-a to support other bundling techniques, such as bundling across different scheduling units, which may not be associated with a unity relationship or otherwise preconfigured relationship (e.g., where PP ¹ Pp).

[0103] In accordance with the described techniques, other configurations for the diagonal matrix, D such as a non-unity configuration, may be used by the UE 115-a, which may support the UE 115-a inferring a physical channel from a demodulation reference signal from another physical channel (e.g., performing channel estimation for, or otherwise inferring, a second PDSCH from a demodulation reference signal of a first PDSCH). For example, referring to bundling across antenna ports, the UE 115-a may infer the physical channel of the data transmission 210-b from the demodulation reference signal 205-a, or infer the physical channel of the data transmission 210-b from both the demodulation reference signal 205-a and the demodulation reference signal 205-b. In another example, referring to bundling across TTIs, the UE 115-a may infer the physical channel of one TTI from a demodulation reference signal of another TTI.

[0104] To support the described techniques for reference signal bundling, antenna ports of different physical channels (e.g., different physical channel transmissions, different instances of PDSCH transmissions) may have a same modulo unknown phase shift, a same modulo unknown amplitude scaling, or both, and the base station 105-a may inform the UE 115-a of a relationship between antenna ports. For example, the base station 105-a may inform the UE 115-a (e.g., via configuration signaling, via control signaling) that transmissions on different antenna ports are transmitted with a same phase angle, such as a same phase angle from one antenna port to the other, or a same phase angle for a given antenna port from one TTI to another TTI, or both. Additionally or alternatively, the base station 105-a may inform the UE 115-a that transmissions on different antenna ports are transmitted with a same amplitude, such as a same amplitude from one antenna port to the other, or a same amplitude for a given antenna port from one TTI to another TTI, or both. Although described with reference to a same phase angle or amplitude from one scheduling unit to another, in some examples, the base station 105-a may inform the UE 115-a that differences in phase angle or amplitude may vary between scheduling units within a threshold amount.

[0105] In one example, the base station 105-a may inform or configure the UE 115-b with a bundling relationship given by H _j or H _j · D where D _j may refer to a scaling of the unprecoded channel matrix given by Equation (1). Using such a relationship, the UE 115-a may use demodulation reference signals corresponding to different physical channel transmissions (e.g., different PDSCH transmissions) on different scheduling units, along with a parameterized relationship between the different scheduling units, to jointly estimate the channel for the different physical transmissions.

[0106] When the different scheduling units correspond to different antenna ports, for example, the UE 115-a may use demodulation reference signals (e.g., demodulation reference signals 205) for different PDSCH transmissions (e.g., different data transmissions 210), as received on different antenna ports, along with the knowledge of the parameterized relationship between the antenna ports, to jointly estimate the physical channel in the respective PDSCH transmissions. For example, the UE 115-a may be informed by the base station 105-a that there is a common phase angle or common phase shift (e.g., rotation) of all transmission antennas with no amplitude change (e.g., corresponding to transmissions by the base station 105-a, such as demodulation reference signals 205 and data transmissions 210). Accordingly, the UE 115-a may only need to estimate one more additional parameter between the two PDSCH transmissions to support channel estimation and demodulation for the PDSCH transmissions.

[0107] In one example, a relationship for demodulation reference signal bundling may include a definition or configuration where a phase difference between the same antenna port index across physical channel transmissions remains constant, or remains constant for some duration such as a configured bundling duration. Referring to an example with two antenna ports (e.g., Port 1 and Port 2), Port 1 of a first physical channel transmission (e.g., PDSCH 1) and Port 1 of a second physical channel transmission (e.g., PDSCH 2) may have an unknown but constant phase shift f ₁ for all resource elements (e.g., as transmitted by the base station 105-a). Likewise, Port 2 of a first physical channel transmission (e.g., PDSCH 1) and Port 2 of a second physical channel transmission (e.g., PDSCH 2) may have an unknown but constant phase shift <p ₂ for all resource elements. In an example of a two-port PDSCH transmission, the transmission may be described by the following:

Yl - H - Pi - _D MRS1 + H · p ₂ ^{■ r} DMRS2

(3) where Y ₁ and Y ₁ may refer to signals carried on two different TTIs or resource elements, and each r _DMRS may refer to a different demodulation reference signal (e.g., with modulo power of one).

[0108] Additionally or alternatively, in another example, a relationship for demodulation reference signal bundling may include a definition or configuration where the relative phase difference (e.g., a difference, D, between phase angles, f ) of antenna ports across physical channel transmissions remains constant or smaller than a threshold, or remains constant or smaller than a threshold for some duration such as a configured bundling duration. Referring again to an example with two antenna ports (e.g., Port 1 and Port 2), an example of a two-port PDSCH transmission may be described by the following: Yl - H - Pi - _D MRS 1 + H · p ₂ ^r DMRS2 with 1 _! — ₂ 1 < D or |0 _! — 0 ₂ | = D

[0109] The base station 105-a may configure transmissions with a structure between the precoders of two physical transmissions, which may use a diagonal matrix such as the one described with reference to Equation (1). The base station 105-a may inform the UE 115-a of such a configuration (e.g., via RRC configuration or signaling, via control signaling), which may indicate that a bundling for reference signals is strong (e.g., configuring transmission and reception according to a unity or identity matrix D _j ), or that the bundling reference is weak (e.g., configuring transmission and reception according to a non-unity or non-identity matrix Di that accounts for, or supports inference of, phase and amplitude scaling between antenna ports), or some other level of demodulation reference signal bundling.

[0110] When demodulation reference signal bundling is signaled, activated, or configured between any two or more physical transmissions, the TIE 115-a may interpret or process demodulation reference signals according to the configured interpretation. In some examples, such configuration may be provided by the base station 105-a in response to capability signaling received from the UE 115-a, such as when the UE 115-a reports that it can exploit a configured structure for an enhanced demodulation reference signal channel estimation (e.g., a joint decoding of a physical channel using demodulation reference signals of different scheduling units). Otherwise, the UE 115-a may proceed with channel estimation performed on a per-transmission basis (e.g., a per-PDSCH channel estimation, a channel estimation that uses the demodulation reference signal corresponding to a given physical channel transmission, but not others).

[0111] In some examples, the base station 105-a may configure reference signal bundling as being relatively weak or relatively strong according to various factors. Additionally or alternatively, the UE 115-a may interpret reference signal bundling as being relatively weak or relatively strong according to various factors. For example, reference signal bundling may be characterized as being relatively strong when physical channel transmissions with bundled reference signals are transmitted back-to-back (e.g., in adjacent TTIs), or when there is not a TTI configured for communications in an opposite direction between bundled TTIs (e.g., when there is not a TTI configured for uplink communications between downlink TTIs with bundled reference signals). In another example, reference signal bundling may be characterized as being relatively strong when physical channel transmissions with bundled reference signals are within a threshold duration, such as being within some quantity of symbols, some quantity of slots, or some quantity of frames (e.g., within a same radio frame). In another example, reference signal bundling may be characterized as being relatively strong when physical channel transmissions with bundled reference signals are within a same on duration or active time of a discontinuous reception (DRX) configuration. In another example, reference signal bundling may be characterized as being relatively strong (e.g., from the perspective of the UE 115-a) when the UE 115-a has not transmitted an uplink symbol between downlink TTIs with bundled reference signals. In another example, reference signal bundling may be characterized as being relatively strong when the corresponding transmissions (e.g., PDSCH transmissions) are transmitted on a same component carrier, or different component carriers of a same frequency band.

[0112] FIG. 3 illustrates an example of a wireless communications system 300 and corresponding operations that support demodulation reference signal bundling in accordance with aspects of the present disclosure. In some examples, the wireless communications system 300 may implement aspects of wireless communications systems 100 or 200 described with reference to FIGs. 1 or 2. The wireless communications system 300 may include a transmitting device, illustrated as a base station 105-b, and a receiving device, illustrated as a UE 115-b. However, in some examples, a transmitting device may be or include another UE 115, such as when the described operations relate to D2D or sidelink communications between UEs 115. Moreover, in some examples, a receiving device may be or include a base station 105, such as when the described operations relate to uplink communications from a UE 115 to a base station 105.

[0113] At 310, the UE 115-b may, in some examples, transmit an indication that reference signal bundling is supported by the UE 115-b (e.g., in a capability indication), which may be received by the base station 105-b. For example, the UE 115-b may indicate to the base station 105-b that one or more techniques for weak reference signal bundling are supported. The signaling of 310 may be included in connection establishment or configuration signaling, such as an information element conveyed as part of RRC signaling.

In some examples, the signaling of reference signal bundling capability at 310 may be modified or omitted. For example, the base station 105-b may assume or otherwise infer that the UE 115-b supports reference signal bundling. In other examples, signaling related to reference signal bundling capability may be transmitted by the UE 115-b in response to a request or polling of the UE 115-b (e.g., by the base station 105-b).

[0114] At 320, the base station 105-b may, in some examples, transmit an indication of a configuration for reference signal bundling, which may be received by the UE 115-b. In some examples, the signaling of 320 may be included in connection establishment or configuration signaling, such as an information element conveyed as part of RRC signaling (e.g., to support a semi-static configuration for reference signal bundling). In some examples, the signaling of 320 may be included in downlink control signaling, such as downlink control information conveyed in a PDCCH transmission (e.g., to support a dynamic configuration for reference signal bundling)

[0115] The transmission by the base station 105-b may indicate that a bundling relationship exists between different scheduling units. For example, the transmission of 320 may indicate that a bundling relationship exists for an antenna port of a physical channel between TTIs, such as a phase shift or amplitude scaling relationship for an antenna port between TTIs, or a phase shift or amplitude scaling relationship between antenna ports. In some examples, the reference signal bundling configuration may indicate that the base station 105-b will apply a same precoder across different TTIs, which may include applying a same phase angle or a same amplitude scaling (e.g., for respective antenna ports) from one TTI to another TTI, or a same phase angle or a same amplitude scaling between different ports. In some examples, the configuration for reference signal bundling of 320 may be responsive to an indication that reference signal bundling is supported, as signaled at 310. In other examples, the configuration for reference signal bundling of 320 may be transmitted without receiving an indication that reference signal bundling is supported (e.g., where operations of 310 may be omitted).

[0116] At 330, the base station 105-b may transmit a transmission during a first TTI, which may be received by the UE 115-b. The transmission of 330 may correspond to a physical channel, or otherwise refer to a physical transmission, such as a PDSCH. The first TTI may refer to a first symbol or first symbol period, or a first set of symbols or symbol periods (e.g., of a slot, mini-slot, subframe, etc., or other time unit configured or otherwise allocated for PDSCH transmissions) which may be referred to as a first PDSCH. The transmission of 330 may include the base station 105-b encoding signals in accordance with a reference signal bundling configuration (e.g., as indicated at 320), such as using a precoder that satisfies the indicated reference signal bundling configuration.

[0117] The transmission of 330 may include a first demodulation reference signal (e.g., demodulation reference signal la) which may be associated with a first data transmission (e.g., Data Transmission la). In some examples, Data Transmission la may refer to a first instance of a PDSCH transmission during the first TTI. The first demodulation reference signal and the first data transmission of 330 may be transmitted by the base station 105-b via a first antenna port, and the first demodulation reference signal and the first data transmission of 330 may be received at the UE 115-b at a corresponding first antenna port.

[0118] In some examples, the transmission of 330 may also include a second demodulation reference signal (e.g., demodulation reference signal lb) which may be associated with a second data transmission (e.g., Data Transmission lb). In some examples, Data Transmission lb may refer to a second instance of a PDSCH transmission during the first TTI (e.g., during a same TTI as Data Transmission la). When included in the transmission of 330, the second demodulation reference signal and the second data transmission of 330 may be transmitted by the base station 105-b via a second antenna port (e.g., different than the first antenna port), and the second demodulation reference signal and the second data transmission of 330 may be received at the UE 115-b at a corresponding second antenna port.

[0119] At 340, the base station 105-b may transmit a transmission during a second TTI (e.g., following the first TTI), which may be received by the UE 115-b. The transmission of 340 may correspond to a physical channel (e.g., a same physical channel as the transmission of 340), or otherwise refer to a physical transmission, such as a PDSCH. The second TTI may refer to a second symbol or second symbol period, or a first set of symbols or symbol periods (e.g., of a slot, mini-slot, subframe, etc., or other time unit configured or otherwise allocated for PDSCH transmissions), which may be referred to as a second PDSCH. In some examples, transmissions of the second TTI of 340 may be conveyed with a same or otherwise related resource as transmissions of the first TTI of 330, such as one or more of a same frame (e.g., a same frame duration), a same slot (e.g., a same slot duration), a same physical resource group, a same carrier, a same component carrier, or other related resource, as the transmissions of the first TTI of 330. The transmission of 340 may also include the base station 105-b encoding signals in accordance with a reference signal bundling configuration (e.g., as indicated at 320), such as using a precoder that satisfies the indicated reference signal bundling configuration. In some examples, the transmission or corresponding reception of 340 may include using a same precoder (e.g., by the base station 105-b, by the UE 115-b) as was used for the transmission or corresponding reception of 330.

[0120] The transmission of 340 may include a first demodulation reference signal (e.g., demodulation reference signal 2a) which may be associated with a first data transmission (e.g., Data Transmission 2a). In some examples, Data Transmission 2a may refer to a first instance of a PDSCH transmission during the second TTI. The first demodulation reference signal and the first data transmission of 340 may be transmitted by the base station 105-b via the first antenna port (e.g., a same antenna port as the first demodulation reference signal and the first data transmission of 330), and the first demodulation reference signal and the first data transmission of 330 may be received at the UE 115-b at the corresponding first antenna port.

[0121] In some examples, the transmission of 340 may also include a second demodulation reference signal (e.g., demodulation reference signal 2b) which may be associated with a second data transmission (e.g., Data Transmission 2b). In some examples, Data Transmission 2b may refer to a second instance of a PDSCH transmission during the second TTI (e.g., during a same symbol period or set of symbol periods as Data Transmission 2a). When included in the transmission of 340, the second demodulation reference signal and the second data transmission of 330 may be transmitted by the base station 105-b via the second antenna port (e.g., a same antenna port as the second demodulation reference signal and the second data transmission of 340), and the second demodulation reference signal and the second data transmission of 330 may be received at the UE 115-b at a corresponding second antenna port.

[0122] In various examples, the transmission by the base station 105-b of demodulation reference signals 2a, 2b, or both, may be based on various configurations or assumptions related to the described reference signal bundling. For example, the transmission of demodulation reference signals 2a, 2b, or both may be based on or configured according to a duration or other aspect of transmission configuration relative to transmissions of 330 (e.g., validity conditions for transmitting reference signals in accordance with the indicated reference signal bundling configuration). In one example, the base station 105-b may perform or configure one or more of the transmissions of 340 based on determining that a duration between the first TTI of 330 and the second TTI of 340 satisfies a threshold (e.g., is less than or equal to a threshold duration). In another example, the base station 105-b may perform or configure one or more of the transmissions of 340 based on determining that TTIs between the first TTI of 330 and the second TTI of 340 are not configured for uplink transmission. In another example, the base station 105-b may perform or configure one or more of the transmissions of 340 based on determining that the first TTI of 330 and the second TTI of 340 are associated with a same on duration or active time of a discontinuous reception configuration of the UE 115-b. In another example, the base station 105-b may perform or configure one or more of the transmissions of 340 based on determining that the UE 115-b has not transmitted an uplink transmission between the first TTI of 330 and the second TTI of 340. In another example, the base station 105-b may perform or configure one or more of the transmissions of 340 based on the data transmissions of 330 (e.g., Data Transmission la, Data Transmission lb) being associated with a same component carrier as data transmissions of 340 (e.g., Data Transmission 2a, Data Transmission 2b), or different component carriers of a same frequency band.

[0123] At 350, the UE 115-b may identify a bundling relationship for one or both of the first antenna port or the second antenna port. In some examples, the UE 115-b may identify that the bundling relationship applies to demodulation reference signals of different scheduling units, such as different TTIs and/or different antenna ports. The bundling relationship may refer to one or more assumptions that may be made by the UE 115-b regarding transmission parameters used by the base station 105-b across different scheduling units, such as between different TTIs or different antenna ports, which may support improvements to channel estimation fidelity or efficiency.

[0124] In some examples, at 350, the UE 115-b may identify that a phase shift or rotation relationship exists, for the first antenna port or the second antenna port, between the first TTI of 330 and the second TTI of 340. In some examples, at 350, the UE 115-b may identify that an amplitude scaling relationship exists, for the first antenna port or the second antenna port, between the first TTI of 330 and the second TTI of 340. In some examples, at 350, the UE 115-b may identify that phase shift or rotation relationship exists between the first antenna port and the second antenna port, or that an amplitude scaling relationship exists between the first antenna port and the second antenna port.

[0125] In various examples, the identification of a bundling relationship at 350 by the UE 115-b may be based on various configurations or assumptions related to the described reference signal bundling. For example, the identification of a bundling relationship may be based on or configured according to a duration or other aspect of transmission configuration relative to the transmissions of 330 and 340 (e.g., validity conditions for processing received reference signals in accordance with the indicated reference signal bundling configuration).

In one example, the UE 115-b may identify a bundling relationship, or determine that the bundling relationship is valid, based on determining that a duration between the first TTI of 330 and the second TTI of 340 satisfies a threshold (e.g., is less than or equal to a threshold duration). In another example, the UE 115-b may identify a bundling relationship, or determine that the bundling relationship is valid, based on determining that TTIs between the first TTI of 330 and the second TTI of 340 are not configured for uplink transmission. In another example, the UE 115-b may identify a bundling relationship, or determine that the bundling relationship is valid, based on determining that the first TTI of 330 and the second TTI of 340 are associated with a same on duration or active time of a discontinuous reception configuration of the UE 115-b. In another example, the UE 115-b may identify a bundling relationship, or determine that the bundling relationship is valid, based on determining that the UE 115-b has not transmitted an uplink transmission between the first TTI of 330 and the second TTI of 340. In another example, the UE 115-b may identify a bundling relationship, or determine that the bundling relationship is valid, based on the data transmissions of 330 (e.g., Data Transmission la, Data Transmission lb) are associated with a same component carrier as data transmissions of 340 (e.g., Data Transmission 2a, Data Transmission 2b), or different component carriers of a same frequency band.

[0126] At 360, the UE 115-b may perform a channel estimation for one or both of the first antenna port or the second antenna port, for the first TTI or for the second TTI, based on one or more of the demodulation reference signals and the identified reference signal bundling relationship. In some examples, the channel estimation of 360 may support (e.g., may include or be followed by) demodulating or decoding one or more of the data transmissions of 330 or 340. [0127] In a first example, at 360, the UE 115-b may perform a channel estimation for the first antenna port for the second TTI of 340 (e.g., for the data transmission 2a) based at least in part on the demodulation reference signal 2a and an identified reference signal bundling relationship between the first TTI and the second TTI (e.g., for the first antenna port). For the first antenna port, the UE 115-b may scale signaling of the second TTI (e.g., signaling of Data Transmission 2a) by a first amplitude relative to the first TTI, and rotate the signaling of the second TTI by a first phase rotation relative to the first TTI. In some examples, such a scaling or rotation may be further based at least in part on the demodulation reference signal la, as received on the first antenna port during the first TTI of 330, which may be enabled by aspects of the indicated reference signal bundling configuration. In some examples, the first amplitude and first phase rotation for the first antenna port may be determined by the UE 115-b (e.g., based at least in part on the demodulation reference signal 2a), and may be unknown to the base station 105-b.

[0128] In another example, at 360, the UE 115-b may perform a channel estimation for the second antenna port for the second TTI of 340 (e.g., for the data transmission 2b) based at least in part on the demodulation reference signal 2b and an identified reference signal bundling relationship between the first TTI and the second TTI (e.g., for the second antenna port). For the second antenna port, the UE 115-b may scale signaling of the second TTI (e.g., signaling of Data Transmission 2b) by a second amplitude relative to the first TTI, and rotate the signaling of the second TTI by a second phase rotation relative to the first TTI. In some examples, such a scaling or rotation may be based at least in part on the demodulation reference signal lb, as received on the second antenna port during the first TTI of 330, which may be enabled by aspects of the indicated reference signal bundling configuration. In some examples, the second amplitude and second phase rotation for the second antenna port may be determined by the UE 115-b (e.g., based at least in part on the demodulation reference signal 2b), and may be unknown to the base station 105-b.

[0129] In some examples, to support performing channel estimation for the first antenna port or the second antenna port, the UE 115-b may assume that an absolute value of a difference between the first phase rotation and the second phase rotation is constant. In some examples, to support performing channel estimation for the first antenna port or the second antenna port, the UE 115-b may assume that an absolute value of a difference between the first phase rotation and the second phase rotation is less than or equal to a threshold value. [0130] For example, when performing channel estimation for the second TTI, the UE 115-b may scale signaling of Data Transmission 2a and Data Transmission 2b by a same amplitude (e.g., relative to the first TTI). Additionally or alternatively, when performing channel estimation for the second TTI, the UE 115-b may rotate signaling of Data Transmission 2a and Data Transmission 2b by a same phase rotation (e.g., relative to the first TTI). Either of these techniques may be enabled or supported by a reference signal bundling configuration where the base station 105-b applies a common phase shift rotation among transmission ports without a change in amplitude.

[0131] In some examples, such bundling techniques (e.g., reference signal bundling between antenna ports) may enable the UE 115-b to perform joint channel estimation for the second TTI, for both the first antenna port and the second antenna port, based at least in part on the demodulation reference signal 2a and the demodulation reference signal 2b. Moreover, in some examples, such bundling techniques (e.g., reference signal bundling between TTIs) may enable the UE 115-b to perform joint channel estimation for the second TTI, for both the first antenna port and the second antenna port, that is further based at least in part on the demodulation reference signal la and the demodulation reference signal lb. Likewise, bundling techniques may enable the UE 115-b to perform joint channel estimation for the first TTI, for both the first antenna port and the second antenna port, based at least in part on two or more of the demodulation reference signal la, the demodulation reference signal lb, the demodulation reference signal 2a, and the demodulation reference signal 2b.

[0132] At 370, the UE 115-b may decode one or more of the data transmissions of 330 or 340, which may be based at least in part on one or more channel estimations of 360 for an associated TTI. For example, the UE 115-b may determine a value of demodulation symbols of Data Transmission 2a based at least in part on a phase rotation or an amplitude scaling of a physical channel for the second TTI as determined at 360 (e.g., identifying a symbol value of Data Transmission 2a from a modulation constellation based at least in part on an angular rotation or amplitude scaling of signaling associated with Data Transmission 2a).

[0133] FIG. 4 shows a block diagram 400 of a device 405 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The device 405 may be an example of aspects of a UE 115 as described herein. The device 405 may include a receiver 410, a communication manager 415, and a transmitter 420. The device 405 may also include one or more processors, memory coupled with the one or more processors, and instructions stored in the memory that are executable by the one or more processors to enable the one or more processors to perform the reference signal bundling features discussed herein. Each of these components may be in communication with one another (e.g., via one or more buses).

[0134] The receiver 410 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to demodulation reference signal bundling, etc.). Information may be passed on to other components of the device 405. The receiver 410 may be an example of aspects of the transceiver 715 described with reference to FIG. 7. The receiver 410 may utilize a single antenna or a set of antennas.

[0135] The communication manager 415 may receive, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval, receive, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval, identify that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval, and perform a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port. The communication manager 415 may be an example of aspects of the communication manager 710 described herein.

[0136] The actions performed by the communication manager 415 as described herein may be implemented to realize one or more potential advantages. One implementation may allow a UE 115 to provide improved quality and reliability of service at the UE 115, as the accuracy or efficiency of channel estimation for physical channel transmissions is enhanced as demodulation reference signals over different time instants or antenna ports can be coherently filtered.

[0137] The communication manager 415, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communication manager 415, or its sub-components may be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC), a FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

[0138] The communication manager 415, or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some examples, the communication manager 415, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the communication manager 415, or its sub-components, may be combined with one or more other hardware components, including but not limited to an input/output (I/O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

[0139] The transmitter 420 may transmit signals generated by other components of the device 405. In some examples, the transmitter 420 may be collocated with a receiver 410 in a transceiver module. For example, the transmitter 420 may be an example of aspects of the transceiver 715 described with reference to FIG. 7. The transmitter 420 may utilize a single antenna or a set of antennas.

[0140] FIG. 5 shows a block diagram 500 of a device 505 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The device 505 may be an example of aspects of a device 405, or a UE 115 as described herein. The device 505 may include a receiver 510, a communication manager 515, and a transmitter 535. The device 505 may also include one or more processors, memory coupled with the one or more processors, and instructions stored in the memory that are executable by the one or more processors to enable the one or more processors to perform the reference signal bundling features discussed herein. Each of these components may be in communication with one another (e.g., via one or more buses).

[0141] The receiver 510 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to demodulation reference signal bundling, etc.). Information may be passed on to other components of the device 505. The receiver 510 may be an example of aspects of the transceiver 715 described with reference to FIG. 7. The receiver 510 may utilize a single antenna or a set of antennas.

[0142] The communication manager 515 may be an example of aspects of the communication manager 415 as described herein. The communication manager 515 may include a first reception port 520, a reference signal bundling component 525, and a channel estimation component 530. The communication manager 515 may be an example of aspects of the communication manager 710 described herein.

[0143] The first reception port 520 may receive, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval and receive, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval.

[0144] The reference signal bundling component 525 may identify that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval.

[0145] The channel estimation component 530 may perform a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port.

[0146] The transmitter 535 may transmit signals generated by other components of the device 505. In some examples, the transmitter 535 may be collocated with a receiver 510 in a transceiver module. For example, the transmitter 535 may be an example of aspects of the transceiver 715 described with reference to FIG. 7. The transmitter 535 may utilize a single antenna or a set of antennas.

[0147] FIG. 6 shows a block diagram 600 of a communication manager 605 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The communication manager 605 may be an example of aspects of a communication manager 415, a communication manager 515, or a communication manager 710 described herein. The communication manager 605 may include a first reception port 610, a reference signal bundling component 615, a channel estimation component 620, a configuration component 625, a capability component 630, a second reception port 635, a bundling validity component 640, and a channel decoding component 645. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

[0148] The first reception port 610 may receive, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval.

[0149] In some examples, the first reception port 610 may receive, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval.

[0150] In some examples, the second reception port 635 may receive, via a second antenna port, a third demodulation reference signal of a third transmission on the physical channel during the first transmission time interval.

[0151] In some examples, the second reception port 635 may receive, via the second antenna port, a fourth demodulation reference signal of a fourth transmission on the physical channel during the second transmission time interval.

[0152] The reference signal bundling component 615 may identify that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval.

[0153] In some examples, the reference signal bundling component 615 may identify that a second phase rotation relationship, or a second amplitude scaling relationship, or a combination thereof, exists between the antenna port of the physical channel and the second antenna port of the physical channel.

[0154] The channel estimation component 620 may perform a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port. [0155] In some examples, the channel estimation component 620 may scale a received signal of the second transmission time interval by a first amplitude relative to the first transmission time interval.

[0156] In some examples, the channel estimation component 620 may rotate the received signal of the second transmission time interval by a first phase rotation relative to the first transmission time interval.

[0157] In some examples, the channel estimation component 620 may scale, for the second antenna port, the received signal of the second transmission time interval by a second amplitude relative to the first transmission time interval.

[0158] In some examples, the channel estimation component 620 may rotate, for the second antenna port, the received signal of the second transmission time interval by a second phase rotation relative to the first transmission time interval.

[0159] In some examples, the channel estimation component 620 may perform a second channel estimation for the second antenna port of the physical channel for the second transmission time interval based on the received second demodulation reference signal and the second phase rotation relationship, or the second amplitude scaling relationship, or the combination thereof, between the antenna port of the physical channel and the second antenna port of the physical channel.

[0160] In some examples, the channel estimation component 620 may perform the channel estimation for the antenna port of the physical channel for the second transmission time interval based on the received fourth demodulation reference signal and the second phase rotation relationship between the antenna port of the physical channel and the second antenna port of the physical channel.

[0161] In some examples, the capability component 630 may transmit an indication that reference signal bundling is supported by the UE.

[0162] In some examples, the configuration component 625 may receive an indication of a configuration for reference signal bundling, where identifying that the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval is based on the indicated configuration for reference signal bundling. In some examples, the configuration for reference signal bundling may responsive to the indication that reference signal bundling is supported.

[0163] In some examples, the bundling validity component 640 may determine that a duration between the first transmission time interval and the second transmission time interval satisfies a threshold.

[0164] In some examples, the bundling validity component 640 may determine that transmission time intervals between the first transmission time interval and the second transmission time interval are not configured for uplink transmission.

[0165] In some examples, the bundling validity component 640 may determine that the first transmission time interval and the second transmission time interval are associated with a same on duration or active time of a discontinuous reception configuration.

[0166] In some examples, the bundling validity component 640 may determine that an uplink transmission has not been transmitted between the first transmission time interval and the second transmission time interval.

[0167] In some examples, the bundling validity component 640 may determine that the first transmission and the second transmission are associated with a same component carrier, or different component carriers of a same frequency band.

[0168] The channel decoding component 645 may decode the second transmission based on performing the channel estimation for the physical channel for the second transmission time interval.

[0169] FIG. 7 shows a diagram of a system 700 including a device 705 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The device 705 may be an example of or include the components of device 405, device 505, or a UE 115 as described herein. The device 705 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communication manager 710, a transceiver 715, an antenna 720, memory 725, and a processor 735. These components may be in electronic communication or otherwise coupled via one or more buses (e.g., bus 740).

[0170] The communication manager 710 may receive, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval, receive, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval, identify that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval, and perform a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port.

[0171] The transceiver 715 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 715 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 715 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

[0172] In some cases, the wireless device may include a single antenna 720. However, in some cases the device may have more than one antenna 720, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

[0173] The memory 725 may include RAM and ROM. The memory 725 may store computer-readable, computer-executable code 730 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 725 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

[0174] The code 730 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 730 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 730 may not be directly executable by the processor 735 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

[0175] The processor 735 may include an intelligent hardware device, (e.g., a general- purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor 735 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 735. The processor 735 may be configured to execute computer- readable instructions stored in a memory (e.g., the memory 725) to cause the device 705 to perform various functions (e.g., functions or tasks supporting demodulation reference signal bundling).

[0176] FIG. 8 shows a block diagram 800 of a device 805 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The device 805 may be an example of aspects of a UE 115 or base station 105 as described herein. The device 805 may include a receiver 810, a communication manager 815, and a transmitter 820. The device 805 may also include one or more processors, memory coupled with the one or more processors, and instructions stored in the memory that are executable by the one or more processors to enable the one or more processors to perform the reference signal bundling features discussed herein. Each of these components may be in communication with one another (e.g., via one or more buses).

[0177] The receiver 810 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to demodulation reference signal bundling, etc.). Information may be passed on to other components of the device 805. The receiver 810 may be an example of aspects of the transceiver 1115 described with reference to FIG. 11. The receiver 810 may utilize a single antenna or a set of antennas.

[0178] The communication manager 815 may receive, from a UE, an indication that the UE supports reference signal bundling, transmit, to the UE and based on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals, and transmit, to the UE on the physical channel and based on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval. The communication manager 815 may be an example of aspects of the communication manager 1110 or 1210 as described herein.

[0179] The actions performed by the communication manager 815 as described herein may be implemented to realize one or more potential advantages. One implementation may allow a base station 105 to provide improved quality and reliability of service at the base station 105, as the accuracy or efficiency of channel estimation for physical channel transmissions is enhanced as demodulation reference signals over different time instants or antenna ports can be coherently filtered.

[0180] The communication manager 815, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communication manager 815, or its sub-components may be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC), a FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

[0181] The communication manager 815, or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some examples, the communication manager 815, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the communication manager 815, or its sub-components, may be combined with one or more other hardware components, including but not limited to an input/output (I/O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

[0182] The transmitter 820 may transmit signals generated by other components of the device 805. In some examples, the transmitter 820 may be collocated with a receiver 810 in a transceiver module. For example, the transmitter 820 may be an example of aspects of the transceiver 1115 described with reference to FIG. 11. The transmitter 820 may utilize a single antenna or a set of antennas. [0183] FIG. 9 shows a block diagram 900 of a device 905 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The device 905 may be an example of aspects of a device 805, a UE 115, or a base station 105 as described herein. The device 905 may include a receiver 910, a communication manager 915, and a transmitter 935. The device 905 may also include one or more processors, memory coupled with the one or more processors, and instructions stored in the memory that are executable by the one or more processors to enable the one or more processors to perform the reference signal bundling features discussed herein. Each of these components may be in communication with one another (e.g., via one or more buses).

[0184] The receiver 910 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to demodulation reference signal bundling, etc.). Information may be passed on to other components of the device 905. The receiver 910 may be an example of aspects of the transceiver 1115 described with reference to FIG. 11. The receiver 910 may utilize a single antenna or a set of antennas.

[0185] The communication manager 915 may be an example of aspects of the communication manager 815 as described herein. The communication manager 915 may include a capability identification component 920, a bundling configuration component 925, and a reference signal bundling component 930. The communication manager 915 may be an example of aspects of the communication manager 1110 or 1210 as described herein.

[0186] The capability identification component 920 may receive, from a UE, an indication that the UE supports reference signal bundling.

[0187] The bundling configuration component 925 may transmit, to the UE and based on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals.

[0188] The reference signal bundling component 930 may transmit, to the UE on the physical channel and based on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval. [0189] The transmitter 935 may transmit signals generated by other components of the device 905. In some examples, the transmitter 935 may be collocated with a receiver 910 in a transceiver module. For example, the transmitter 935 may be an example of aspects of the transceiver 1115 described with reference to FIG. 11. The transmitter 935 may utilize a single antenna or a set of antennas.

[0190] FIG. 10 shows a block diagram 1000 of a communication manager 1005 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The communication manager 1005 may be an example of aspects of a communication manager 815, a communication manager 915, or a communication manager 1110 described herein. The communication manager 1005 may include a capability identification component 1010, a bundling configuration component 1015, a reference signal bundling component 1020, a first transmission port 1025, and a second transmission port 1030. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

[0191] The capability identification component 1010 may receive, from a UE, an indication that the UE supports reference signal bundling.

[0192] The bundling configuration component 1015 may transmit, to the UE and based on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals.

[0193] The reference signal bundling component 1020 may transmit, to the UE on the physical channel and based on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval. In some examples, the physical channel may be a downlink channel. In some examples, the physical channel may be a sidelink channel.

[0194] In some examples, the reference signal bundling component 1020 may determine that one or more transmission time intervals between the first transmission time interval and the second transmission time interval are not configured for uplink transmission, and transmitting the second demodulation reference signal may be based on the determining. [0195] In some examples, the reference signal bundling component 1020 may determine that the first transmission time interval and the second transmission time interval are associated with a same on duration or active time of a discontinuous reception configuration of the UE, and transmitting the second demodulation reference signal may be based on the determining.

[0196] In some examples, the reference signal bundling component 1020 may determine that the UE has not transmitted an uplink transmission between the first transmission time interval and the second transmission time interval, and transmitting the second demodulation reference signal may be based on the determining.

[0197] In some examples, the reference signal bundling component 1020 may determine that a duration between the first transmission time interval and the second transmission time interval satisfies a threshold, where transmitting the second demodulation reference signal is based on the determining.

[0198] In some examples, the first transmission port 1025 may transmit the first demodulation reference signal via the antenna port during the first transmission time interval.

[0199] In some examples, the second transmission port 1030 may transmit the second demodulation reference signal via the antenna port during the second transmission time interval.

[0200] FIG. 11 shows a diagram of a system 1100 including a device 1105 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The device 1105 may be an example of or include the components of device 805, device 905, or a UE 115 as described herein. The device 1105 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communication manager 1110, a transceiver 1115, an antenna 1120, memory 1125, and a processor 1135. These components may be in electronic communication or otherwise coupled via one or more buses (e.g., bus 1140).

[0201] The communication manager 1110 may receive, from a UE, an indication that the UE supports reference signal bundling, transmit, to the UE and based on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals, and transmit, to the UE on the physical channel and based on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval.

[0202] The transceiver 1115 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1115 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1115 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

[0203] In some cases, the wireless device may include a single antenna 1120. However, in some cases the device may have more than one antenna 1120, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

[0204] The memory 1125 may include RAM and ROM. The memory 1125 may store computer-readable, computer-executable code 1130 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 1125 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

[0205] The code 1130 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 1130 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 1130 may not be directly executable by the processor 1135 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

[0206] The processor 1135 may include an intelligent hardware device, (e.g., a general- purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor 1135 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 1135. The processor 1135 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1125) to cause the device 1105 to perform various functions (e.g., functions or tasks supporting demodulation reference signal bundling).

[0207] FIG. 12 shows a diagram of a system 1200 including a device 1205 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The device 1205 may be an example of or include the components of device 805, device 905, or a base station 105 as described herein. The device 1205 may include components for bi directional voice and data communications including components for transmitting and receiving communications, including a communication manager 1210, a transceiver 1215, an antenna 1220, memory 1225, and a processor 1235. These components may be in electronic communication or otherwise coupled via one or more buses (e.g., bus 1240).

[0208] The communication manager 1210 may receive, from a UE, an indication that the UE supports reference signal bundling, transmit, to the UE and based on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals, and transmit, to the UE on the physical channel and based on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval.

[0209] The transceiver 1215 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1215 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1215 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

[0210] In some cases, the wireless device may include a single antenna 1220. However, in some cases the device may have more than one antenna 1220, which may be capable of concurrently transmitting or receiving multiple wireless transmissions. [0211] The memory 1225 may include RAM and ROM. The memory 1225 may store computer-readable, computer-executable code 1230 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 1225 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

[0212] The code 1230 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 1230 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 1230 may not be directly executable by the processor 1235 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

[0213] The processor 1235 may include an intelligent hardware device, (e.g., a general- purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor 1235 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 1235. The processor 1235 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1225) to cause the device 1205 to perform various functions (e.g., functions or tasks supporting demodulation reference signal bundling).

[0214] FIG. 13 shows a flowchart illustrating a method 1300 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The operations of method 1300 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1300 may be performed by a communication manager as described with reference to FIGs. 4 through 7. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, a UE may perform aspects of the described functions using special-purpose hardware.

[0215] At 1305, the UE may receive, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval. The operations of 1305 may be performed according to the methods described herein. In some examples, aspects of the operations of 1305 may be performed by a first reception port as described with reference to FIGs. 4 through 7.

[0216] At 1310, the UE may receive, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval. The operations of 1310 may be performed according to the methods described herein. In some examples, aspects of the operations of 1310 may be performed by a first reception port as described with reference to FIGs. 4 through 7.

[0217] At 1315, the UE may identify that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval. The operations of 1315 may be performed according to the methods described herein. In some examples, aspects of the operations of 1315 may be performed by a reference signal bundling component as described with reference to FIGs. 4 through 7.

[0218] At 1320, the UE may perform a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port. The operations of 1320 may be performed according to the methods described herein. In some examples, aspects of the operations of 1320 may be performed by a channel estimation component as described with reference to FIGs. 4 through 7.

[0219] FIG. 14 shows a flowchart illustrating a method 1400 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The operations of method 1400 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1400 may be performed by a communication manager as described with reference to FIGs. 4 through 7. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, a UE may perform aspects of the described functions using special-purpose hardware.

[0220] At 1405, the UE may transmit an indication that reference signal bundling is supported by the UE, where the configuration for reference signal bundling is responsive to the indication that reference signal bundling is supported. The operations of 1405 may be performed according to the methods described herein. In some examples, aspects of the operations of 1405 may be performed by a capability component as described with reference to FIGs. 4 through 7.

[0221] At 1410, the UE may receive an indication of a configuration for reference signal bundling. In some examples, the configuration for reference signal bundling may be responsive to the indication that reference signal bundling is supported. The operations of 1410 may be performed according to the methods described herein. In some examples, aspects of the operations of 1410 may be performed by a configuration component as described with reference to FIGs. 4 through 7.

[0222] At 1415, the UE may receive, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval. The operations of 1415 may be performed according to the methods described herein. In some examples, aspects of the operations of 1415 may be performed by a first reception port as described with reference to FIGs. 4 through 7.

[0223] At 1420, the UE may receive, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval. The operations of 1420 may be performed according to the methods described herein. In some examples, aspects of the operations of 1420 may be performed by a first reception port as described with reference to FIGs. 4 through 7.

[0224] At 1425, the UE may identify that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval. In some examples, the identifying may be based on the indicated configuration for reference signal bundling. The operations of 1425 may be performed according to the methods described herein. In some examples, aspects of the operations of 1425 may be performed by a reference signal bundling component as described with reference to FIGs. 4 through 7.

[0225] At 1430, the UE may perform a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port. The operations of 1430 may be performed according to the methods described herein. In some examples, aspects of the operations of 1430 may be performed by a channel estimation component as described with reference to FIGs. 4 through 7.

[0226] FIG. 15 shows a flowchart illustrating a method 1500 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The operations of method 1500 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1500 may be performed by a communication manager as described with reference to FIGs. 4 through 7. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. Additionally or alternatively, a UE may perform aspects of the described functions using special-purpose hardware.

[0227] At 1505, the UE may receive, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval. The operations of 1505 may be performed according to the methods described herein. In some examples, aspects of the operations of 1505 may be performed by a first reception port as described with reference to FIGs. 4 through 7.

[0228] At 1510, the UE may receive, via a second antenna port, a third demodulation reference signal of a third transmission on the physical channel during the first transmission time interval. The operations of 1510 may be performed according to the methods described herein. In some examples, aspects of the operations of 1510 may be performed by a second reception port as described with reference to FIGs. 4 through 7.

[0229] At 1515, the UE may receive, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval. The operations of 1515 may be performed according to the methods described herein. In some examples, aspects of the operations of 1515 may be performed by a first reception port as described with reference to FIGs. 4 through 7.

[0230] At 1520, the UE may identify that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval. The operations of 1520 may be performed according to the methods described herein. In some examples, aspects of the operations of 1520 may be performed by a reference signal bundling component as described with reference to FIGs. 4 through 7.

[0231] At 1525, the UE may perform a channel estimation for the antenna port for the physical channel for the second transmission time interval based on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port. The operations of 1525 may be performed according to the methods described herein. In some examples, aspects of the operations of 1525 may be performed by a channel estimation component as described with reference to FIGs. 4 through 7.

[0232] At 1530, the UE may identify that a second phase rotation relationship, or a second amplitude scaling relationship, or a combination thereof, exists between the antenna port of the physical channel and the second antenna port of the physical channel. The operations of 1530 may be performed according to the methods described herein. In some examples, aspects of the operations of 1530 may be performed by a reference signal bundling component as described with reference to FIGs. 4 through 7.

[0233] At 1535, the UE may perform a second channel estimation for the second antenna port of the physical channel for the second transmission time interval based on the received second demodulation reference signal and the second phase rotation relationship, or the second amplitude scaling relationship, or the combination thereof, between the antenna port of the physical channel and the second antenna port of the physical channel. The operations of 1535 may be performed according to the methods described herein. In some examples, aspects of the operations of 1535 may be performed by a channel estimation component as described with reference to FIGs. 4 through 7.

[0234] FIG. 16 shows a flowchart illustrating a method 1600 that supports demodulation reference signal bundling in accordance with aspects of the present disclosure. The operations of method 1600 may be implemented by a UE 115 or base station 105 or its components as described herein. For example, the operations of method 1600 may be performed by a communication manager as described with reference to FIGs. 8 through 12. In some examples, a UE or base station may execute a set of instructions to control the functional elements of the UE or base station to perform the described functions. Additionally or alternatively, a UE or base station may perform aspects of the described functions using special-purpose hardware.

[0235] At 1605, the UE or base station may receive, from a UE, an indication that the UE supports reference signal bundling. The operations of 1605 may be performed according to the methods described herein. In some examples, aspects of the operations of 1605 may be performed by a capability identification component as described with reference to FIGs. 8 through 12.

[0236] At 1610, the UE or base station may transmit, to the UE and based on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals. The operations of 1610 may be performed according to the methods described herein. In some examples, aspects of the operations of 1610 may be performed by a bundling configuration component as described with reference to FIGs. 8 through 12.

[0237] At 1615, the UE or base station may transmit, to the UE on the physical channel and based on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval. The operations of 1615 may be performed according to the methods described herein. In some examples, aspects of the operations of 1615 may be performed by a reference signal bundling component as described with reference to FIGs. 8 through 12.

[0238] It should be noted that the methods described herein describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined.

[0239] The following provides an overview of aspects of the present disclosure:

[0240] Aspect 1 : A method for wireless communication at a UE, comprising: receiving, via an antenna port, a first demodulation reference signal of a first transmission on a physical channel during a first transmission time interval; receiving, via the antenna port, a second demodulation reference signal of a second transmission on the physical channel during a second transmission time interval; identifying that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval; and performing a channel estimation for the antenna port for the physical channel for the second transmission time interval based at least in part on the received second demodulation reference signal and the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, for the antenna port.

[0241] Aspect 2: The method of aspect 1, wherein the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, is the phase rotation relationship.

[0242] Aspect 3 : The method of any of aspects 1 through 2, wherein the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, is the amplitude scaling relationship.

[0243] Aspect 4: The method of any of aspects 1 through 3, wherein performing the channel estimation for the antenna port comprises: scaling a received signal of the second transmission time interval by a first amplitude relative to the first transmission time interval; and rotating the received signal of the second transmission time interval by a first phase rotation relative to the first transmission time interval.

[0244] Aspect 5 : The method of aspect 4, wherein the first amplitude and the first phase rotation are unknown to a transmitter of the first demodulation reference signal and the second demodulation reference signal.

[0245] Aspect 6: The method of any of aspects 4 through 5, further comprising performing a second channel estimation for a second antenna port, comprising: scaling, for the second antenna port, the received signal of the second transmission time interval by a second amplitude relative to the first transmission time interval; and rotating, for the second antenna port, the received signal of the second transmission time interval by a second phase rotation relative to the first transmission time interval.

[0246] Aspect 7: The method of aspect 6, wherein an absolute value of a difference between the first phase rotation and the second phase rotation is assumed by the UE to be constant to perform the channel estimation for the antenna port and perform the second channel estimation for the second antenna port. [0247] Aspect 8: The method of any of aspects 6 through 7, wherein an absolute value of a difference between the first phase rotation and the second phase rotation is assumed by the UE to be less than or equal to a threshold value to perform the channel estimation for the antenna port and performing the second channel estimation for the second antenna port.

[0248] Aspect 9: The method of any of aspects 1 through 8, further comprising: receiving an indication of a configuration for reference signal bundling, wherein identifying that the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, exists for the antenna port of the physical channel between the first transmission time interval and the second transmission time interval is based at least in part on the indicated configuration for reference signal bundling.

[0249] Aspect 10: The method of aspect 9, further comprising: transmitting an indication that reference signal bundling is supported by the UE, wherein the configuration for reference signal bundling is responsive to the indication that reference signal bundling is supported.

[0250] Aspect 11 : The method of any of aspects 1 through 10, further comprising: receiving, via a second antenna port, a third demodulation reference signal of a third transmission on the physical channel during the first transmission time interval; identifying that a second phase rotation relationship, or a second amplitude scaling relationship, or a combination thereof, exists between the antenna port of the physical channel and the second antenna port of the physical channel; and performing a second channel estimation for the second antenna port of the physical channel for the second transmission time interval based at least in part on the received second demodulation reference signal and the second phase rotation relationship, or the second amplitude scaling relationship, or the combination thereof, between the antenna port of the physical channel and the second antenna port of the physical channel.

[0251] Aspect 12: The method of aspect 11, wherein the second phase rotation relationship, or the second amplitude scaling relationship, or the combination thereof, is the second phase rotation relationship.

[0252] Aspect 13: The method of any of aspects 11 through 12, wherein the second phase rotation relationship, or the second amplitude scaling relationship, or the combination thereof, is the second amplitude scaling relationship. [0253] Aspect 14: The method of any of aspects 11 through 13, wherein the phase rotation relationship for the antenna port of the physical channel and the second phase rotation relationship for the second antenna port of the physical channel indicates a same phase rotation and a same amplitude scaling for all antenna ports between the first transmission time interval and the second transmission time interval.

[0254] Aspect 15: The method of any of aspects 11 through 14, further comprising: receiving, via the second antenna port, a fourth demodulation reference signal of a fourth data transmission on the physical channel during the second transmission time interval; and performing the channel estimation for the antenna port of the physical channel for the second transmission time interval based at least in part on the received fourth demodulation reference signal and the second phase rotation relationship between the antenna port of the physical channel and the second antenna port of the physical channel.

[0255] Aspect 16: The method of any of aspects 1 through 15, wherein identifying that the phase rotation relationship exists comprises: determining that a duration between the first transmission time interval and the second transmission time interval satisfies a threshold.

[0256] Aspect 17: The method of any of aspects 1 through 16, wherein identifying that the phase rotation relationship exists comprises: determining that transmission time intervals between the first transmission time interval and the second transmission time interval are not configured for uplink transmission. [0257] Aspect 18: The method of any of aspects 1 through 17, wherein identifying that the phase rotation relationship exists comprises: determining that the first transmission time interval and the second transmission time interval are associated with a same on duration or active time of a discontinuous reception configuration.

[0258] Aspect 19: The method of any of aspects 1 through 18, wherein identifying that the phase rotation relationship exists comprises: determining that an uplink transmission has not been transmitted between the first transmission time interval and the second transmission time interval.

[0259] Aspect 20: The method of any of aspects 1 through 19, wherein identifying that the phase rotation relationship exists comprises: determining that the first transmission and the second transmission are associated with a same component carrier, or different component carriers of a same frequency band.

[0260] Aspect 21 : The method of any of aspects 1 through 20, further comprising: decoding the second data transmission based at least in part on performing the channel estimation for the physical channel for the second transmission time interval.

[0261] Aspect 22: A method for wireless communication, comprising: receiving, from a UE, an indication that the UE supports reference signal bundling; transmitting, to the UE and based at least in part on receiving the indication that the UE supports reference signal bundling, an indication that a phase rotation relationship, or an amplitude scaling relationship, or a combination thereof, exists for an antenna port of a physical channel between transmission time intervals; and transmitting, to the UE on the physical channel and based at least in part on transmitting the indication, a first demodulation reference signal for a first transmission during a first transmission time interval and a second demodulation reference signal for a second transmission during a second transmission time interval.

[0262] Aspect 23 : The method of aspect 22, wherein transmitting the first demodulation reference signal and the second demodulation reference signal comprises: transmitting the first demodulation reference signal via the antenna port during the first transmission time interval; and transmitting the second demodulation reference signal via the antenna port during the second transmission time interval.

[0263] Aspect 24: The method of any of aspects 22 through 23, wherein the indication that the phase rotation relationship, or the amplitude scaling relationship, or the combination thereof, indicates that the phase rotation relationship exists between antenna ports, the method further comprising: transmitting, to the UE on the physical channel and based at least in part on the received indication, the first demodulation reference signal via the antenna port and a third demodulation reference signal via a second antenna port during the first transmission time interval.

[0264] Aspect 25: The method of any of aspects 22 through 24, further comprising: determining that a duration between the first transmission time interval and the second transmission time interval satisfies a threshold, wherein transmitting the second demodulation reference signal is based at least in part on the determining. [0265] Aspect 26: The method of any of aspects 22 through 25, further comprising: determining that one or more transmission time intervals between the first transmission time interval and the second transmission time interval are not configured for uplink transmission, wherein transmitting the second demodulation reference signal is based at least in part on the determining.

[0266] Aspect 27: The method of any of aspects 22 through 26, further comprising: determining that the first transmission time interval and the second transmission time interval are associated with a same on duration or active time of a discontinuous reception configuration of the UE, wherein transmitting the second demodulation reference signal is based at least in part on the determining.

[0267] Aspect 28: The method of any of aspects 22 through 27, further comprising: determining that the UE has not transmitted an uplink transmission between the first transmission time interval and the second transmission time interval, wherein transmitting the second demodulation reference signal is based at least in part on the determining.

[0268] Aspect 29: The method of any of aspects 22 through 28, wherein the first transmission and the second transmission are associated with a same component carrier, or different component carriers of a same frequency band.

[0269] Aspect 30: The method of any of aspects 22 through 29, wherein the physical channel is a downlink channel.

[0270] Aspect 31 : The method of any of aspects 22 through 30, wherein the physical channel is a sidelink channel.

[0271] Aspect 32: An apparatus for wireless communication at a UE, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 1 through 21.

[0272] Aspect 33 : An apparatus for wireless communication at a UE, comprising at least one means for performing a method of any of aspects 1 through 21.

[0273] Aspect 34: A non-transitory computer-readable medium storing code for wireless communication at a UE, the code comprising instructions executable by a processor to perform a method of any of aspects 1 through 21. [0274] Aspect 35: An apparatus for wireless communication, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method of any of aspects 22 through 31.

[0275] Aspect 36: An apparatus for wireless communication, comprising at least one means for performing a method of any of aspects 22 through 31.

[0276] Aspect 37: A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform a method of any of aspects 22 through 31.

[0277] Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques may be applicable to various other wireless communications systems such as Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, as well as other systems and radio technologies not explicitly mentioned herein.

[0278] Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0279] The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). [0280] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

[0281] Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include random- access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

[0282] As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of’ or “one or more of’) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on.”

[0283] In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label.

[0284] The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “example” used herein means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

[0285] The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.