CSI (CHANNEL STATE INFORMATION)-RS (REFERENCE SIGNAL) TECHNIQUES FOR CHANNEL ESTIMATION AND BEAM REFINEMENT

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Applications No.

62/381 ,669 filed August 31 , 2016, entitled "CHANNEL STATE INFORMATION

REFERENCE SIGNAL DESIGN FOR HIGH BAND CELLULAR SYSTEM"; No.

62/382,108 filed August 31 , 2016, entitled "REFINE REFERENCE SIGNAL (RRS) FOR MID-HIGH BAND SYSTEMS USING GI-DFT-S-OFDM WAVEFORM"; and No.

62/402,857 filed September 30, 2016, entitled "CHANNEL STATE INFORMATION REFERENCE SIGNAL (CSI-RS) DESIGN FOR NR", the contents of each of which are herein incorporated by reference in their entirety.

FIELD

[0002] The present disclosure relates to wireless technology, and more specifically to techniques that can facilitate channel estimation and beam refinement in 5G (Fifth Generation) systems based on CSI (Channel State lnformation)-RS (Reference

Signals).

BACKGROUND

[0003] Channel estimation channel state information (CSI) reference signal (RS) can be employed to obtain channel state feedback to assist a base station (BS, e.g., eNodeB, etc.) in its precoding or digital beam forming operation in multiple transmit antenna modes, which can assist the BS in scheduling as well as transmit precoding operation in various MIMO (Multiple Input Multiple Output) transmission modes.

[0004] Additionally, beam-forming at both the user equipment (UE) and the BS (Base Station, for example, gNB (next generation NodeB), eNB (evolved NodeB), etc.) is a technology that can enable millimeter wave (mmWave) small cell implementation.

Advanced beam-forming techniques can be employed to overcome large path-loss experienced by a millimeter wave channel. Beamforming procedures and the reference signals used for achieving it can vary for different physical control and data channels. For mmWave cellular systems, Hybrid antenna architectures (HAA), which have a smaller number of Radio Frequency (RF) chains than the number of physical antennas, are popular due to their hardware complexity as well as economic efficiencies. [0005] A beam-forming procedure for HAA compromises two aspects that can be tracked either independently or jointly or iteratively depending on the resources and the constraints: (a) analog beam forming or tracking, and (b) digital beam forming or tracking. The analog beam-forming part can be mostly a wideband operation due to the hardware limitations of HAA, while the digital beamforming part can be selected to be narrowband.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a block diagram illustrating an example user equipment (UE) useable in connection with various aspects described herein.

[0007] FIG. 2 is a diagram illustrating example components of a device that can be employed in accordance with various aspects discussed herein.

[0008] FIG. 3 is a diagram illustrating example interfaces of baseband circuitry that can be employed in accordance with various aspects discussed herein.

[0009] FIG. 4 is a block diagram illustrating a system employable at a UE (User

Equipment) that facilitates channel estimation and/or beam management based on received CSI (Channel State lnformation)-RS (Reference Signals), according to various aspects described herein.

[0010] FIG. 5 is a block diagram illustrating a system employable at a BS (Base Station) that facilitates transmission of CSI-RS for beam management and/or channel estimation by a receiving UE, according to various aspects described herein.

[0011] FIG. 6 is a diagram illustrating an example scenario of beam management CSI-RS transmission by a BS according to various aspects discussed herein.

[0012] FIG. 7 is a diagram illustrating an example scenario of beam management CSI-RS transmission with a shortened Gl (Guard Interval) sequence in each repetition, according to various aspects discussed herein.

[0013] FIG. 8 is a diagram illustrating an example scenario wherein beam management CSI-RS is transmitted via a Gl, according to various aspects discussed herein.

[0014] FIG. 9 is a diagram illustrating an example scenario involving two repetitions of beam management CSI-RS configured within one Gl interval, with the beam management CSI-RS of two adjacent Gl symbols are grouped, according to various aspects discussed herein. [0015] FIG. 10 is a flow diagram of an example method employable at a UE that facilitates refinement of a receive beam based on beam management CSI-RS, according to various aspects discussed herein.

[0016] FIG. 11 is a flow diagram of an example method employable at a BS that facilitates refinement of a receive beam at a UE based on beam management CSI-RS, according to various aspects discussed herein.

[0017] FIG. 12 is a pair of diagrams illustrating two types of self-contained subframe (or slot) structures that can be employed in connection with various aspects discussed herein.

[0018] FIG. 13 is a diagram illustrating a map of CSI-RS resource within one physical resource block (PRB), in connection with various aspects discussed herein.

[0019] FIG. 14 is a diagram illustrating an example of generation of a GI-DFT (Discrete Fourier Transform)-s (spread)-OFDM (Orthogonal Frequency Division

Multiplexing) channel estimation CSI-RS symbol for one beam/antenna port using an interpolated ZC (Zadoff-Chu) sequence, according to various aspects discussed herein.

[0020] FIG. 15 is a diagram illustrating an example of multiplexing channel estimation CSI-RS of two ports using different cyclic shifts of a ZC sequence, according to various aspects discussed herein.

[0021] FIG. 16 is a diagram illustrating an example of multiplexing channel estimation CSI-RS of 4 beam/antenna ports using a combination of CDM (e.g., cyclic shifts of ZC sequence) and FDM, according to various aspects discussed herein.

[0022] FIG. 17 is a diagram illustrating an example alternative architecture for multiplexing channel estimation CSI-RS of two ports with addition of the Gl sequence before the DFT spread, according to various aspects discussed herein.

[0023] FIG. 18 is a diagram illustrating an example of another alternative architecture for multiplexing channel estimation CSI-RS of two ports with the Gl sequence added to only one port (port 0), according to various aspects discussed herein.

[0024] FIG. 19 is a flow diagram of an example method employable at a UE that facilitates generation of CSI based on channel estimation CSI-RS in connection with a

DFT spread waveform, according to various aspects discussed herein.

[0025] FIG. 20 is a flow diagram of an example method employable at a BS that facilitates generation of channel estimation CSI-RS for a DFT spread waveform, according to various aspects discussed herein.

[0026] FIG. 21 is a diagram illustrating an example of multiplexing CSI-RS of 16 antenna ports in two CSI-RS OFDM symbols using different cyclic shifts of the same ZC sequence and symbol-wise spreading using an OCC (Orthogonal Cover Code) of length 2, according to various aspects discussed herein.

[0027] FIG. 22 is a diagram illustrating an example of IFDM comprising two combs with 8 antenna ports multiplexed on each comb, according to various aspects discussed herein.

[0028] FIG. 23 is a flow diagram of an example method employable at a UE that facilitates generation of CSI based on channel estimation CSI-RS transmitted via one or more dedicated symbols, according to various aspects discussed herein.

[0029] FIG. 24 is a flow diagram of an example method employable at a BS that facilitates generation of channel estimation CSI-RS for transmission via one or more dedicated symbols, according to various aspects discussed herein.

DETAILED DESCRIPTION

[0030] The present disclosure will now be described with reference to the attached drawing figures, wherein like reference numerals are used to refer to like elements throughout, and wherein the illustrated structures and devices are not necessarily drawn to scale. As utilized herein, terms "component," "system," "interface," and the like are intended to refer to a computer-related entity, hardware, software (e.g., in execution), and/or firmware. For example, a component can be a processor (e.g., a microprocessor, a controller, or other processing device), a process running on a processor, a controller, an object, an executable, a program, a storage device, a computer, a tablet PC and/or a user equipment (e.g., mobile phone, etc.) with a processing device. By way of illustration, an application running on a server and the server can also be a component. One or more components can reside within a process, and a component can be localized on one computer and/or distributed between two or more computers. A set of elements or a set of other components can be described herein, in which the term "set" can be interpreted as "one or more."

[0031] Further, these components can execute from various computer readable storage media having various data structures stored thereon such as with a module, for example. The components can communicate via local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network, such as, the Internet, a local area network, a wide area network, or similar network with other systems via the signal). [0032] As another example, a component can be an apparatus with specific functionality provided by mechanical parts operated by electric or electronic circuitry, in which the electric or electronic circuitry can be operated by a software application or a firmware application executed by one or more processors. The one or more processors can be internal or external to the apparatus and can execute at least a part of the software or firmware application. As yet another example, a component can be an apparatus that provides specific functionality through electronic components without mechanical parts; the electronic components can include one or more processors therein to execute software and/or firmware that confer(s), at least in part, the functionality of the electronic components.

[0033] Use of the word exemplary is intended to present concepts in a concrete fashion. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless specified otherwise, or clear from context, "X employs A or B" is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then "X employs A or B" is satisfied under any of the foregoing instances. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from context to be directed to a singular form. Furthermore, to the extent that the terms "including", "includes", "having", "has", "with", or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term

"comprising." Additionally, in situations wherein one or more numbered items are discussed (e.g., a "first X", a "second X", etc.), in general the one or more numbered items may be distinct or they may be the same, although in some situations the context may indicate that they are distinct or that they are the same.

[0034] As used herein, the term "circuitry" may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable hardware components that provide the described functionality. In some embodiments, the circuitry may be implemented in, or functions associated with the circuitry may be implemented by, one or more software or firmware modules. In some embodiments, circuitry may include logic, at least partially operable in hardware.

[0035] Embodiments described herein may be implemented into a system using any suitably configured hardware and/or software. FIG. 1 illustrates an architecture of a system 1 00 of a network in accordance with some embodiments. The system 100 is shown to include a user equipment (UE) 101 and a UE 102. The UEs 101 and 102 are illustrated as smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks), but may also comprise any mobile or non-mobile computing device, such as Personal Data Assistants (PDAs), pagers, laptop computers, desktop computers, wireless handsets, or any computing device including a wireless communications interface.

[0036] In some embodiments, any of the UEs 101 and 102 can comprise an Internet of Things (loT) UE, which can comprise a network access layer designed for low-power loT applications utilizing short-lived UE connections. An loT UE can utilize technologies such as machine-to-machine (M2M) or machine-type communications (MTC) for exchanging data with an MTC server or device via a public land mobile network (PLMN), Proximity-Based Service (ProSe) or device-to-device (D2D) communication, sensor networks, or loT networks. The M2M or MTC exchange of data may be a machine-initiated exchange of data. An loT network describes interconnecting loT UEs, which may include uniquely identifiable embedded computing devices (within the Internet infrastructure), with short-lived connections. The loT UEs may execute background applications (e.g., keep-alive messages, status updates, etc.) to facilitate the connections of the loT network.

[0037] The UEs 101 and 102 may be configured to connect, e.g., communicatively couple, with a radio access network (RAN) 1 10— the RAN 1 10 may be, for example, an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN), a NextGen RAN (NG RAN), or some other type of RAN. The UEs 101 and 102 utilize connections 103 and 104, respectively, each of which comprises a physical communications interface or layer (discussed in further detail below); in this example, the connections 103 and 104 are illustrated as an air interface to enable communicative coupling, and can be consistent with cellular communications protocols, such as a Global System for Mobile Communications (GSM) protocol, a code-division multiple access (CDMA) network protocol, a Push-to-Talk (PTT) protocol, a PTT over Cellular (POC) protocol, a Universal Mobile Telecommunications System (UMTS) protocol, a 3GPP Long Term Evolution (LTE) protocol, a fifth generation (5G) protocol, a New Radio (NR) protocol, and the like.

[0038] In this embodiment, the UEs 101 and 1 02 may further directly exchange communication data via a ProSe interface 105. The ProSe interface 105 may alternatively be referred to as a sidelink interface comprising one or more logical channels, including but not limited to a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH).

[0039] The UE 102 is shown to be configured to access an access point (AP) 106 via connection 107. The connection 107 can comprise a local wireless connection, such as a connection consistent with any IEEE 802.1 1 protocol, wherein the AP 106 would comprise a wireless fidelity (WiFi®) router. In this example, the AP 1 06 is shown to be connected to the Internet without connecting to the core network of the wireless system (described in further detail below).

[0040] The RAN 1 1 0 can include one or more access nodes that enable the connections 1 03 and 104. These access nodes (ANs) can be referred to as base stations (BSs), NodeBs, evolved NodeBs (eNBs), next Generation NodeBs (gNB), RAN nodes, and so forth, and can comprise ground stations (e.g., terrestrial access points) or satellite stations providing coverage within a geographic area (e.g., a cell). The RAN 1 1 0 may include one or more RAN nodes for providing macrocells, e.g., macro RAN node 1 1 1 , and one or more RAN nodes for providing femtocells or picocells (e.g., cells having smaller coverage areas, smaller user capacity, or higher bandwidth compared to macrocells), e.g., low power (LP) RAN node 1 12.

[0041] Any of the RAN nodes 1 1 1 and 1 12 can terminate the air interface protocol and can be the first point of contact for the UEs 101 and 102. In some embodiments, any of the RAN nodes 1 1 1 and 1 12 can fulfill various logical functions for the RAN 1 1 0 including, but not limited to, radio network controller (RNC) functions such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management.

[0042] In accordance with some embodiments, the UEs 101 and 102 can be configured to communicate using Orthogonal Frequency-Division Multiplexing (OFDM) communication signals with each other or with any of the RAN nodes 1 1 1 and 1 1 2 over a multicarrier communication channel in accordance various communication techniques, such as, but not limited to, an Orthogonal Frequency-Division Multiple Access (OFDMA) communication technique (e.g., for downlink communications) or a Single Carrier Frequency Division Multiple Access (SC-FDMA) communication technique (e.g., for uplink and ProSe or sidelink communications), although the scope of the embodiments is not limited in this respect. The OFDM signals can comprise a plurality of orthogonal subcarriers. [0043] In some embodiments, a downlink resource grid can be used for downlink transmissions from any of the RAN nodes 1 1 1 and 1 12 to the UEs 101 and 1 02, while uplink transmissions can utilize similar techniques. The grid can be a time-frequency grid, called a resource grid or time-frequency resource grid, which is the physical resource in the downlink in each slot. Such a time-frequency plane representation is a common practice for OFDM systems, which makes it intuitive for radio resource allocation. Each column and each row of the resource grid corresponds to one OFDM symbol and one OFDM subcarrier, respectively. The duration of the resource grid in the time domain corresponds to one slot in a radio frame. The smallest time-frequency unit in a resource grid is denoted as a resource element. Each resource grid comprises a number of resource blocks, which describe the mapping of certain physical channels to resource elements. Each resource block comprises a collection of resource elements; in the frequency domain, this may represent the smallest quantity of resources that currently can be allocated. There are several different physical downlink channels that are conveyed using such resource blocks.

[0044] The physical downlink shared channel (PDSCH) may carry user data and higher-layer signaling to the UEs 101 and 102. The physical downlink control channel (PDCCH) may carry information about the transport format and resource allocations related to the PDSCH channel, among other things. It may also inform the UEs 101 and 102 about the transport format, resource allocation, and H-ARQ (Hybrid Automatic Repeat Request) information related to the uplink shared channel. Typically, downlink scheduling (assigning control and shared channel resource blocks to the UE 102 within a cell) may be performed at any of the RAN nodes 1 1 1 and 1 12 based on channel quality information fed back from any of the UEs 101 and 102. The downlink resource assignment information may be sent on the PDCCH used for (e.g., assigned to) each of the UEs 101 and 1 02.

[0045] The PDCCH may use control channel elements (CCEs) to convey the control information. Before being mapped to resource elements, the PDCCH complex-valued symbols may first be organized into quadruplets, which may then be permuted using a sub-block interleaver for rate matching. Each PDCCH may be transmitted using one or more of these CCEs, where each CCE may correspond to nine sets of four physical resource elements known as resource element groups (REGs). Four Quadrature Phase Shift Keying (QPSK) symbols may be mapped to each REG. The PDCCH can be transmitted using one or more CCEs, depending on the size of the downlink control information (DCI) and the channel condition. There can be four or more different PDCCH formats defined in LTE with different numbers of CCEs (e.g., aggregation level, L=1 , 2, 4, or 8).

[0046] Some embodiments may use concepts for resource allocation for control channel information that are an extension of the above-described concepts. For example, some embodiments may utilize an enhanced physical downlink control channel (EPDCCH) that uses PDSCH resources for control information transmission. The EPDCCH may be transmitted using one or more enhanced the control channel elements (ECCEs). Similar to above, each ECCE may correspond to nine sets of four physical resource elements known as an enhanced resource element groups (EREGs). An ECCE may have other numbers of EREGs in some situations.

[0047] The RAN 1 1 0 is shown to be communicatively coupled to a core network (CN) 1 20— via an S1 interface 1 1 3. In embodiments, the CN 120 may be an evolved packet core (EPC) network, a NextGen Packet Core (NPC) network, or some other type of CN. In this embodiment the S1 interface 1 13 is split into two parts: the S1 -U interface 1 14, which carries traffic data between the RAN nodes 1 1 1 and 1 12 and the serving gateway (S-GW) 122, and the S1 -mobility management entity (MME) interface 1 15, which is a signaling interface between the RAN nodes 1 1 1 and 1 12 and MMEs 121 .

[0048] In this embodiment, the CN 1 20 comprises the MMEs 1 21 , the S-GW 122, the Packet Data Network (PDN) Gateway (P-GW) 123, and a home subscriber server (HSS) 124. The MMEs 121 may be similar in function to the control plane of legacy Serving General Packet Radio Service (GPRS) Support Nodes (SGSN). The MMEs 121 may manage mobility aspects in access such as gateway selection and tracking area list management. The HSS 124 may comprise a database for network users, including subscription-related information to support the network entities' handling of

communication sessions. The CN 120 may comprise one or several HSSs 124, depending on the number of mobile subscribers, on the capacity of the equipment, on the organization of the network, etc. For example, the HSS 124 can provide support for routing/roaming, authentication, authorization, naming/addressing resolution, location dependencies, etc.

[0049] The S-GW 122 may terminate the S1 interface 1 13 towards the RAN 1 10, and routes data packets between the RAN 1 10 and the CN 120. In addition, the S-GW 122 may be a local mobility anchor point for inter-RAN node handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities may include lawful intercept, charging, and some policy enforcement. [0050] The P-GW 123 may terminate an SGi interface toward a PDN. The P-GW 123 may route data packets between the EPC network 123 and external networks such as a network including the application server 130 (alternatively referred to as application function (AF)) via an Internet Protocol (IP) interface 125. Generally, the application server 130 may be an element offering applications that use IP bearer resources with the core network (e.g., UMTS Packet Services (PS) domain, LTE PS data services, etc.). In this embodiment, the P-GW 123 is shown to be communicatively coupled to an application server 130 via an IP communications interface 125. The application server 130 can also be configured to support one or more communication services (e.g., Voice-over-Internet Protocol (VoIP) sessions, PTT sessions, group communication sessions, social networking services, etc.) for the UEs 1 01 and 102 via the CN 120.

[0051] The P-GW 123 may further be a node for policy enforcement and charging data collection. Policy and Charging Enforcement Function (PCRF) 126 is the policy and charging control element of the CN 120. In a non-roaming scenario, there may be a single PCRF in the Home Public Land Mobile Network (HPLMN) associated with a UE's Internet Protocol Connectivity Access Network (IP-CAN) session. In a roaming scenario with local breakout of traffic, there may be two PCRFs associated with a UE's IP-CAN session: a Home PCRF (H-PCRF) within a HPLMN and a Visited PCRF (V-PCRF) within a Visited Public Land Mobile Network (VPLMN). The PCRF 126 may be communicatively coupled to the application server 130 via the P-GW 123. The application server 130 may signal the PCRF 126 to indicate a new service flow and select the appropriate Quality of Service (QoS) and charging parameters. The PCRF 126 may provision this rule into a Policy and Charging Enforcement Function (PCEF) (not shown) with the appropriate traffic flow template (TFT) and QoS class of identifier (QCI), which commences the QoS and charging as specified by the application server 130.

[0052] FIG. 2 illustrates example components of a device 200 in accordance with some embodiments. In some embodiments, the device 200 may include application circuitry 202, baseband circuitry 204, Radio Frequency (RF) circuitry 206, front-end module (FEM) circuitry 208, one or more antennas 21 0, and power management circuitry (PMC) 21 2 coupled together at least as shown. The components of the illustrated device 200 may be included in a UE or a RAN node. In some embodiments, the device 200 may include less elements (e.g., a RAN node may not utilize application circuitry 202, and instead include a processor/controller to process IP data received from an EPC). In some embodiments, the device 200 may include additional elements such as, for example, memory/storage, display, camera, sensor, or input/output (I/O) interface. In other embodiments, the components described below may be included in more than one device (e.g., said circuitries may be separately included in more than one device for Cloud-RAN (C-RAN) implementations).

[0053] The application circuitry 202 may include one or more application processors. For example, the application circuitry 202 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.). The processors may be coupled with or may include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications or operating systems to run on the device 200. In some embodiments, processors of application circuitry 202 may process IP data packets received from an EPC.

[0054] The baseband circuitry 204 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 204 may include one or more baseband processors or control logic to process baseband signals received from a receive signal path of the RF circuitry 206 and to generate baseband signals for a transmit signal path of the RF circuitry 206. Baseband processing circuity 204 may interface with the application circuitry 202 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 206. For example, in some embodiments, the baseband circuitry 204 may include a third generation (3G) baseband processor 204A, a fourth generation (4G) baseband processor 204B, a fifth generation (5G) baseband processor 204C, or other baseband processor(s) 204D for other existing generations, generations in development or to be developed in the future (e.g., second generation (2G), sixth generation (6G), etc.). The baseband circuitry 204 (e.g., one or more of baseband processors 204A-D) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 206. In other embodiments, some or all of the functionality of baseband processors 204A-D may be included in modules stored in the memory 204G and executed via a Central Processing Unit (CPU) 204E. The radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency shifting, etc. In some embodiments, modulation/demodulation circuitry of the baseband circuitry 204 may include Fast-Fourier Transform (FFT), precoding, or constellation mapping/demapping functionality. In some embodiments,

encoding/decoding circuitry of the baseband circuitry 204 may include convolution, tail- biting convolution, turbo, Viterbi, or Low Density Parity Check (LDPC) encoder/decoder functionality. Embodiments of modulation/demodulation and encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments.

[0055] In some embodiments, the baseband circuitry 204 may include one or more audio digital signal processor(s) (DSP) 204F. The audio DSP(s) 204F may be include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuitry 204 and the application circuitry 202 may be implemented together such as, for example, on a system on a chip (SOC).

[0056] In some embodiments, the baseband circuitry 204 may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 204 may support communication with an evolved universal terrestrial radio access network (EUTRAN) or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry 204 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.

[0057] RF circuitry 206 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 206 may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 206 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 208 and provide baseband signals to the baseband circuitry 204. RF circuitry 206 may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry 204 and provide RF output signals to the FEM circuitry 208 for transmission.

[0058] In some embodiments, the receive signal path of the RF circuitry 206 may include mixer circuitry 206a, amplifier circuitry 206b and filter circuitry 206c. In some embodiments, the transmit signal path of the RF circuitry 206 may include filter circuitry 206c and mixer circuitry 206a. RF circuitry 206 may also include synthesizer circuitry 206d for synthesizing a frequency for use by the mixer circuitry 206a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry 206a of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry 208 based on the synthesized frequency provided by synthesizer circuitry 206d. The amplifier circuitry 206b may be configured to amplify the down- converted signals and the filter circuitry 206c may be a low-pass filter (LPF) or bandpass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry 204 for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry 206a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect.

[0059] In some embodiments, the mixer circuitry 206a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 206d to generate RF output signals for the FEM circuitry 208. The baseband signals may be provided by the baseband circuitry 204 and may be filtered by filter circuitry 206c.

[0060] In some embodiments, the mixer circuitry 206a of the receive signal path and the mixer circuitry 206a of the transmit signal path may include two or more mixers and may be arranged for quadrature downconversion and upconversion, respectively. In some embodiments, the mixer circuitry 206a of the receive signal path and the mixer circuitry 206a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuitry 206a of the receive signal path and the mixer circuitry 206a may be arranged for direct downconversion and direct upconversion, respectively. In some embodiments, the mixer circuitry 206a of the receive signal path and the mixer circuitry 206a of the transmit signal path may be configured for super-heterodyne operation.

[0061] In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry 206 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 204 may include a digital baseband interface to communicate with the RF circuitry 206. [0062] In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the

embodiments is not limited in this respect.

[0063] In some embodiments, the synthesizer circuitry 206d may be a fractional-N synthesizer or a fractional N/N+1 synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry 206d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider.

[0064] The synthesizer circuitry 206d may be configured to synthesize an output frequency for use by the mixer circuitry 206a of the RF circuitry 206 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 206d may be a fractional N/N+1 synthesizer.

[0065] In some embodiments, frequency input may be provided by a voltage controlled oscillator (VCO), although that is not a requirement. Divider control input may be provided by either the baseband circuitry 204 or the applications processor 202 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a look-up table based on a channel indicated by the applications processor 202.

[0066] Synthesizer circuitry 206d of the RF circuitry 206 may include a divider, a delay-locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by either N or N+1 (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip- flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

[0067] In some embodiments, synthesizer circuitry 206d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fLO). In some embodiments, the RF circuitry 206 may include an IQ/polar converter.

[0068] FEM circuitry 208 may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas 210, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 206 for further processing. FEM circuitry 208 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 206 for transmission by one or more of the one or more antennas 21 0. In various embodiments, the amplification through the transmit or receive signal paths may be done solely in the RF circuitry 206, solely in the FEM 208, or in both the RF circuitry 206 and the FEM 208.

[0069] In some embodiments, the FEM circuitry 208 may include a TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include an LNA to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 206). The transmit signal path of the FEM circuitry 208 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 206), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 21 0).

[0070] In some embodiments, the PMC 212 may manage power provided to the baseband circuitry 204. In particular, the PMC 21 2 may control power-source selection, voltage scaling, battery charging, or DC-to-DC conversion. The PMC 212 may often be included when the device 200 is capable of being powered by a battery, for example, when the device is included in a UE. The PMC 21 2 may increase the power conversion efficiency while providing desirable implementation size and heat dissipation

characteristics.

[0071] While FIG. 2 shows the PMC 212 coupled only with the baseband circuitry 204. However, in other embodiments, the PMC 2 12 may be additionally or alternatively coupled with, and perform similar power management operations for, other components such as, but not limited to, application circuitry 202, RF circuitry 206, or FEM 208.

[0072] In some embodiments, the PMC 212 may control, or otherwise be part of, various power saving mechanisms of the device 200. For example, if the device 200 is in an RRC_Connected state, where it is still connected to the RAN node as it expects to receive traffic shortly, then it may enter a state known as Discontinuous Reception Mode (DRX) after a period of inactivity. During this state, the device 200 may power down for brief intervals of time and thus save power.

[0073] If there is no data traffic activity for an extended period of time, then the device 200 may transition off to an RRCJdle state, where it disconnects from the network and does not perform operations such as channel quality feedback, handover, etc. The device 200 goes into a very low power state and it performs paging where again it periodically wakes up to listen to the network and then powers down again. The device 200 may not receive data in this state, in order to receive data, it must transition back to RRC_Connected state.

[0074] An additional power saving mode may allow a device to be unavailable to the network for periods longer than a paging interval (ranging from seconds to a few hours). During this time, the device is totally unreachable to the network and may power down completely. Any data sent during this time incurs a large delay and it is assumed the delay is acceptable.

[0075] Processors of the application circuitry 202 and processors of the baseband circuitry 204 may be used to execute elements of one or more instances of a protocol stack. For example, processors of the baseband circuitry 204, alone or in combination, may be used execute Layer 3, Layer 2, or Layer 1 functionality, while processors of the application circuitry 204 may utilize data (e.g., packet data) received from these layers and further execute Layer 4 functionality (e.g., transmission communication protocol (TCP) and user datagram protocol (UDP) layers). As referred to herein, Layer 3 may comprise a radio resource control (RRC) layer, described in further detail below. As referred to herein, Layer 2 may comprise a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer, described in further detail below. As referred to herein, Layer 1 may comprise a physical (PHY) layer of a UE/RAN node, described in further detail below.

[0076] FIG. 3 illustrates example interfaces of baseband circuitry in accordance with some embodiments. As discussed above, the baseband circuitry 204 of FIG. 2 may comprise processors 204A-204E and a memory 204G utilized by said processors. Each of the processors 204A-204E may include a memory interface, 304A-304E,

respectively, to send/receive data to/from the memory 204G.

[0077] The baseband circuitry 204 may further include one or more interfaces to communicatively couple to other circuitries/devices, such as a memory interface 312 (e.g., an interface to send/receive data to/from memory external to the baseband circuitry 204), an application circuitry interface 314 (e.g., an interface to send/receive data to/from the application circuitry 202 of FIG. 2), an RF circuitry interface 316 (e.g., an interface to send/receive data to/from RF circuitry 206 of FIG. 2), a wireless hardware connectivity interface 31 8 (e.g., an interface to send/receive data to/from Near Field Communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components), and a power management interface 320 (e.g., an interface to send/receive power or control signals to/from the PMC 212).

[0078] Referring to FIG. 4, illustrated is a block diagram of a system 400 employable at a UE (User Equipment) that facilitates channel estimation and/or beam management based on received CSI-RS, according to various aspects described herein. System 400 can include one or more processors 410 (e.g., one or more baseband processors such as one or more of the baseband processors discussed in connection with FIG. 2 and/or FIG. 3) comprising processing circuitry and associated memory interface(s) (e.g., memory interface(s) discussed in connection with FIG. 3), transceiver circuitry 420 (e.g., comprising one or more of transmitter circuitry or receiver circuitry, which can employ common circuit elements, distinct circuit elements, or a combination thereof), and a memory 430 (which can comprise any of a variety of storage mediums and can store instructions and/or data associated with one or more of processor(s) 410 or transceiver circuitry 420). In various aspects, system 400 can be included within a user equipment (UE), for example, a MTC UE. As described in greater detail below, system 400 can facilitate channel estimation and/or beam management based on CSI-RS according to one or more of the sets of techniques discussed herein.

[0079] Referring to FIG. 5, illustrated is a block diagram of a system 500 employable at a BS (Base Station) that facilitates transmission of CSI-RS for beam management and/or channel estimation by a receiving UE, according to various aspects described herein. System 500 can include one or more processors 510 (e.g., one or more baseband processors such as one or more of the baseband processors discussed in connection with FIG. 2 and/or FIG. 3) comprising processing circuitry and associated memory interface(s) (e.g., memory interface(s) discussed in connection with FIG. 3), communication circuitry 520 (e.g., which can comprise circuitry for one or more wired (e.g., X2, etc.) connections and/or transceiver circuitry that can comprise one or more of transmitter circuitry (e.g., associated with one or more transmit chains) or receiver circuitry (e.g., associated with one or more receive chains), wherein the transmitter circuitry and receiver circuitry can employ common circuit elements, distinct circuit elements, or a combination thereof), and memory 530 (which can comprise any of a variety of storage mediums and can store instructions and/or data associated with one or more of processor(s) 510 or communication circuitry 520). In various aspects, system 500 can be included within an Evolved Universal Terrestrial Radio Access Network (E- UTRAN) Node B (Evolved Node B, eNodeB, or eNB), next generation Node B (gNodeB or gNB) or other base station in a wireless communications network. In some aspects, the processor(s) 510, communication circuitry 520, and the memory 530 can be included in a single device, while in other aspects, they can be included in different devices, such as part of a distributed architecture. As described in greater detail below, system 500 can facilitate UE channel estimation and/or beam management based on CSI-RS according to one or more of the sets of techniques discussed herein.

Beam Management CSI-RS design for mid-high band systems using DFT-s- OFDM-based waveform

[0080] In various aspects of a first set of techniques discussed herein, designs are discussed for a beam refinement reference signal (RRS, e.g., beam management CSI (Channel State lnformation)-RS (Reference Signal), etc., which can be generated by processor(s) 510) that can be transmitted (e.g., via communication circuitry 520) from a BS (e.g., gNB, eNB, etc.) to assist analog beam refinement or tracking at the UE (e.g., via processor(s) 410 and transceiver circuitry 420). A coarser UE receive (Rx) analog beamforming can be achieved using the downlink synchronization signals (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410) such as primary synchronization signal (PSS), but the accuracy of such tracking is limited by the frequency of PSS transmissions. Thus, a special reference signal such as beam management CSI-RS can be employed (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410) if any additional refinement or update of UE Rx beam is to be performed (e.g., via processor(s) 410 and transceiver circuitry 420).

[0081] In various aspects, a beam management CSI-RS design is discussed herein that can be employed (e.g., by system 400 and system 500) for mid-high band mmWave systems that use a DFT-s-OFDM (discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing)-based waveform for the air interface, such as a ZT (Zero Tail)-DFT-s-OFDM waveform or a Gl (Guard lnterval)-DFT-s-OFDM waveform. [0082] The beam management CSI-RS can primarily be employed (e.g. , by system 400 and system 500) to train or update the wideband analog Rx

beamforming at a UE (e.g., via beamforming weights selected by processor(s) 41 0 and applied by transceiver circuitry 420) for a fixed BS (e.g., gNB, eNB, etc.) transmit (Tx) beam (e.g., transmitted via communication circuitry 420 based on beamforming weights selected by processor(s) 41 0). One possible way to train or update the UE Rx beam is through Rx beam sweeping that performs reference signal reception (e.g. , via transceiver circuitry 420 for measurement by

processor(s) 41 0) at UE using multiple Rx beams (e.g., based on distinct sets of beamforming weights selected by processor(s) 41 0 and applied by transceiver circuitry 420, wherein each distinct set of beamforming weights is associated with a distinct beam of the Rx beams swept through). In accordance with design options discussed herein, the RRS (e.g., beam management CSI-RS, etc. , generated by processor(s) 41 0) can be transmitted (e.g., via communication circuitry 420) from the BS (e.g., gNB, eNB, etc.) based on time-domain repetition of the beam management CSI-RS symbols using sub-carrier sub-sampling (e.g. , processor(s) 41 0 loading periodic sub-carriers with the reference signal (e.g., beam

management CSI-RS)). The frequency domain subsampling can result in a replicated time-domain signal within one symbol duration, enabling multiple UE Rx beam trials (e.g., via distinct sets of beamforming selected by processor(s) 41 0 and applied by transceiver circuitry 420) in one symbol duration. The number of repetitions of beam management CSI-RS within one symbol as well as the number of consecutive symbols carrying beam management CSI-RS can be configured by the BS (e.g., gNB, eNB, etc.) from a set of predetermined values (e.g., via higher layer signaling generated by processor(s) 51 0, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 41 0).

[0083] In various aspects, techniques are discussed herein for employing beam management CSI-RS in connection with a high band cellular system using a DFT- s-OFDM-based (e.g., ZT/GI-DFT-s-OFDM) access waveform. In mmWave cellular communications systems, beam-forming at both the BS (e.g., gNB, eNB, etc.) and the UE can be employed to overcome large path-loss experienced by the millimeter wave channel. The BS can transmit (e.g. , via communication circuitry 520) beam management CSI-RS (e.g., generated by processor(s) 51 0) in a beamformed manner to a particular user or a group of users (e.g., each of which can employ a system 400). Each receiving UE can train or update its Rx beam by performing multiple beam reception of the beam management CSI-RS using beam sweeping (e.g., based on distinct sets of beamforming weights selected by processor(s) 41 0 and applied by transceiver circuitry 420, wherein each distinct set of beamforming weights is associated with a distinct beam of the Rx beams swept through). The Rx beams (e.g., formed via transceiver circuitry 420 applying associated sets of beamforming weights) tried during the beam sweep can be from a set of

predetermined beams, for example, a codebook. In order to facilitate beam sweep reception at the UE (e.g., via transceiver circuitry 420 based on beamforming weights selected (e.g., from a codebook) by processor(s) 41 0), the BS can transmit (e.g., via communication circuitry 520) multiple copies of the beam management CSI-RS (e.g., generated by processor(s) 51 0). The BS can achieve time-domain repetition of the beam management CSI-RS symbols using sub-carrier sub- sampling, for example, via processor(s) 41 0 loading periodic sub-carriers with the reference signals (e.g., beam management CSI-RS). The frequency domain subsampling results in a replicated time-domain signal within one symbol duration, enabling multiple UE Rx beam trials in one symbol duration. The number of repetitions of beam management CSI-RS within one symbol (e.g. , the subcarrier sampling factor) as well as the number of consecutive symbols that contain beam management CSI-RS can be configured by BS from a set of predetermined values (e.g., via a DCI message or higher layer signaling generated by processor(s) 51 0, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 41 0). The total number of beams a U E can attempt (e.g., by transceiver circuitry 420 applying beamforming weights selected by processor(s) 41 0) in one transmission opportunity of beam management CSI-RS (e.g., generated by processor(s) 51 0 and transmitted by communication circuitry 520) is product of these two numbers. In various aspects, Zadoff-Chu (ZC) sequences (or other sequences, e.g., PN (pseudo-noise), Gold, Kasami, etc.) can be employed by processor(s) 51 0 for generating beam management CSI-RS for transmission by communication circuitry 520.

[0084] Referring to FIG. 6, illustrated is a diagram showing an example scenario of beam management CSI-RS transmission by a BS according to various aspects discussed herein. In the example scenario of FIG. 6, the BS uses an N _Z c length ZC (etc.) sequence (e.g., generated by processor(s) 51 0) to transmit (e.g., via

communication circuitry 520) beam management CSI-RS. The total of number of sub- carriers are N _sc > N _Z c- The ZC (etc.) symbols can be loaded (e.g., by processor(s) 510) on every nth (e.g., 4th in FIG. 6), sub-carrier (sub-sampling) to achieve 'n' repetitions of a beam management CSI-RS signal in one symbol duration. For a DFT-s-OFDM-based (e.g., GI-DFT-s-OFDM, ZT-DFT-s-OFDM, etc.) waveform, no further modifications are needed. The UE can then attempt 'n' different Rx beams (e.g., via processor(s) 410 selecting n sets of beamforming weights that can be consecutively applied by transceiver circuitry 420) to detect the beam management CSI-RS. A BS can further modulate the ZC (etc.) sequence (e.g., via processor(s) 510) with a transmitting point identification information.

[0085] In various aspects, the sub-carrier sampling factor 'n' can be configured through high layer signaling or DCI (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410), or can be pre-defined.

[0086] In various aspects, each repeat of beam management CSI-RS can be generated (e.g., by processor(s) 51 0) with a shortened Gl sequence. Referring to FIG. 7, illustrated is a diagram showing an example scenario of beam management CSI-RS transmission with a shortened Gl sequence in each repetition, according to various aspects discussed herein. To accommodate a Gl sequence in each RRS, the ZC (etc.) sequence that forms the beam management CSI-RS can be DFT spread. N can be the total number of samples in a GI-DFT-s-OFDM symbol, and N _G i can be the length of the Gl (or zero tail) sequence. Additionally, M can be the DFT spread size, where M < N. Then the length N _zc of the used ZC (etc.) sequence used for beam management CSI- RS can be a largest prime such that, \N. N _ZC /M]≤ (JV - N _GI )/4. In FIG. 7, the length of the shortened Gl sequence in the beam management CSI-RS symbols is N _G i/4.

[0087] In various aspects, the Gl can be utilized to transmit beam management CSI- RS (e.g., via processor(s) 510 generating the beam management CSI-RS in the Gl of the GI-DFT-s-OFDM symbols via techniques discussed herein, which can be transmitted by communication circuitry 520). Referring to FIG. 8, illustrated is a diagram showing an example scenario wherein beam management CSI-RS is transmitted via a Gl, according to various aspects discussed herein.

[0088] In various aspects, the length of the Gl for beam management CSI-RS can be configured by higher layer signaling (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 41 0). [0089] In various aspects, whether a given subframe (or slot) contains beam management CSI-RS or not can be indicated by an associated indicator in DCI (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410), for example, "0" for normal GI-DFT-s-OFDM (or ZT-DFT-s-OFDM, etc.), "1 " for special GI-DFT-s-OFDM (or ZT-DFT-s-OFDM, etc.) symbols with beam refinement CSI-RS.

[0090] In various aspects, for a short Gl configuration, that the Gls of N- _\ consecutive symbols can be associated as a group (e.g., via DCI or higher layer signaling generated by processor(s) 51 0, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410), and can be transmitted by the same Tx beam (e.g., via communication circuitry 520). Referring to FIG. 9, illustrated is a diagram of an example scenario involving two repetitions of beam management CSI-RS configured within one Gl interval, with the beam management CSI-RS of two adjacent Gl symbols are grouped, according to various aspects discussed herein.

[0091] In various aspects, the starting subframe/slot can be explicitly indicated within DCI (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410), or can be implicitly associated to the subframe/slot numbering.

[0092] In various aspects, the grouped DFT-s-OFDM-based (e.g., GI-DFT-s-OFDM, ZT-DFT-s-OFDM, etc.) symbols can be configured by DCI or high layer signaling (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410).

[0093] In various aspects, the beam management CSI-RS signal (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410) can be non-UE specific targeting a group of UE, or alternatively can be specific to a particular UE. Such information (e.g., associating beam management CSI-RS to a group of UEs or a particular UE) can be explicitly indicated within the DCI (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410) in various aspects. In general, the sub-carriers used for transmission (e.g., via communication circuitry 520) of the beam management CSI-RS (e.g., generated by processor(s) 510) can be from any portion of the system bandwidth (e.g., they need not be at the edge of the system bandwidth). An offset in the occupied sub- carrier's for beam management CSI-RS transmission results in a known phase ramp in the time-domain signal that can be compensated by the UE (e.g., by processor(s) 410) appropriately. Likewise, the subcarrier sampling factor (which was 4 in the example of FIG. 6), the number of times the beam management CSI-RS signal repeats per symbol, etc., can be configured by the BS using control messaging (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410) or can be based on UE feedback.

[0094] In various aspects, beam management CSI-RS from different BSs (e.g., gNBs, eNBs, etc.) can be multiplexed. Neighboring BSs can use either different sets of sub-sampled sub-carriers (e.g., FDM (Frequency Division Multiplexing) of the reference signals from different BSs) and/or ZC (etc.) sequences with different roots (e.g., CDM (Code Division Multiplexing) of the reference signals from different BSs) to transmit beam management CSI-RS. Multiplexing beam management CSI-RS from multiple BSs can minimize interference, as well as allow UE(s) to perform beam refinement (e.g., via processor(s) 410 and transceiver circuitry 420) with respect to multiple BSs

simultaneously.

[0095] A first example embodiment of the first set of techniques can be employed (e.g., by system 400 and system 500) to facilitate Rx beam refinement at a UE (e.g., employing system 400) communicating with a high band (mmWave) base station (BS) (e.g., employing system 500), wherein the first example embodiment can comprise a BS generating (e.g., via processor(s) 510, for transmission by communication circuitry 520) beam management CSI-RS for assisting UE in refining a receive beam (e.g., via processor(s) 410 and transceiver circuitry 420).

[0096] In various aspects of the first example embodiment of the first set of techniques, the generated beam management CSI-RS can be repeated in the time- domain (e.g., by processor(s) 510 and communication circuitry 520) to facilitate performance receive beam-scanning at the UE (e.g., by processor(s) 41 0 and transceiver circuitry 420) to update the Rx beam.

[0097] In various aspects of the first example embodiment of the first set of techniques, the time-domain repetitions of RRS can be generated using sub-sampling of sub-carriers (e.g., by processor(s) 510 for generation by communication circuitry 520).

[0098] In various aspects of the first example embodiment of the first set of techniques, the BS can employ (e.g., via processor(s) 510) a Zadoff-Chu (ZC) (etc.) sequence to generate the beam management CSI-RS. In various such aspects, the BS can modulate the ZC (etc.) sequence with a TRP (Tx (Transmit)/Rx (Receive) Point)- related ID (e.g., via processor(s) 510) to generate the beam management CSI-RS. In various such aspects, each BS of a plurality of BSs can use a disjoint set of sub- sampled sub-carriers (which can be referred to herein as a cosset) to generate beam management CSI-RS (e.g., via processor(s) 510 mapping the beam management CSI- RS to the disjoint set of sub-sampled sub-carriers for transmission by communication circuitry 520). In various such aspects, each BS of the plurality of BSs can employ distinct roots of ZC sequence to generate (e.g., via processor(s) 510) beam

management CSI-RS.

[0099] In various aspects of the first example embodiment of the first set of techniques, an apparatus (e.g., system 500) can be employed at a BS to construct and transmit the beam management CSI-RS according to any of the above aspects of the first example embodiment of the first set of techniques, wherein the apparatus can (e.g., via processor(s) 510): (a) identify an appropriate subcarrier sampling factor and subset (e.g., cosset) of sub-carriers for loading the beam management CSI-RS signal; (b) load an appropriately assigned ZC (etc.) sequence or modulated ZC (etc.) sequence on the assigned cosset of sub-carriers; and (c) perform occupied cosset hopping as

appropriate.

[00100] In various aspects of the first example embodiment of the first set of techniques, an apparatus (e.g., system 400) can be employed at a UE to receive the beam management CSI-RS generated according to any of the above aspects of the first example embodiment of the first set of techniques, wherein the apparatus can (e.g., via processor(s) 410): (a) perform receive beam scanning to identify the best receive beam for a BS and (b) perform time/frequency filtering and correlations to distinguish beam management CSI-RS signals from multiple BSs.

[00101 ] Referring to FIG. 10, illustrated is a flow diagram of an example method 1 000 employable at a UE that facilitates refinement of a receive beam based on beam management CSI-RS, according to various aspects discussed herein. In other aspects, a machine readable medium can store instructions associated with method 1 000 that, when executed, can cause a UE to perform the acts of method 1000.

[00102] At 1010, beam management CSI-RS can be received via a plurality of Rx beams for a plurality of repetitions for each of one or more symbols.

[00103] At 1020, the beam management CSI-RS received via the plurality of Rx beams can be measured.

[00104] At 1030, a best Rx beam can be selected based on the measured beam management CSI-RS. [00105] Additionally or alternatively, method 1000 can include one or more other acts described herein in connection with system 400 and the first set of techniques.

[00106] Referring to FIG. 11 , illustrated is a flow diagram of an example method 1 100 employable at a BS that facilitates refinement of a receive beam at a UE based on beam management CSI-RS, according to various aspects discussed herein. In other aspects, a machine readable medium can store instructions associated with method 1 1 00 that, when executed, can cause a BS to perform the acts of method 1 100.

[00107] At 1 1 10, a subcarrier sampling factor and associated subset of subcarriers can be selected for beam management CSI-RS.

[00108] At 1 120, the beam management CSI-RS can be generated based on a ZC, PN, or other sequence.

[00109] At 1 130, the beam management CSI-RS can be mapped to the identified subset of subcarriers.

[00110] Additionally or alternatively, method 1 100 can include one or more other acts described herein in connection with system 500 and the first set of techniques.

CSI-RS design for high band cellular system using DFT spread waveform

[00111 ] In various aspects, a second set of techniques can employ CSI-RS (e.g., channel estimation CSI-RS) for estimating channel quality in connection with beamforming in a cellular system operating in high band (e.g., millimeter wave), for example, in a system employing discrete Fourier transform (DFT) spread waveforms such as cyclic prefix (CP) discrete Fourier transform (DFT) spread OFDM (CP-DFT-s- OFDM) and Guard interval (Gl) or zero tail (ZT) discrete Fourier transform (DFT) spread OFDM (GI-DFT-s-OFDM or ZT-DFT-s-OFDM, respectively) waveform as an air- interface.

[00112] In high band in general, and millimeter wave band in particular, hybrid antenna architectures (HAA), which have smaller number of Radio Frequency (RF) chains than the number of antennas, can be deployed at the BS (e.g., employing system 500) and UE (e.g., employing system 400) due to both component cost as well as complexity considerations. In such scenarios, the CSI-RS feedback (e.g., via a CSI report generated by processor(s) 410, transmitted via transceiver circuitry 420, received via communication circuitry 520, and processed by processor(s) 510, wherein the CSI report can indicate one or more CSI parameters measured by processor(s) 410, such as CQI (Channel Quality Indicator), PMI (Precoding Matrix Indicator), Rl (Rank

Indicator), PTI (Precoding Type Indicator), and/or CRI (CSI Resource Indicator)) can be used for both the analog as well as the digital beam tracking/training at the high band BS.

[00113] In high band, due to hardware constraints, the transmit analog beam forming operation (e.g., as implemented by processor(s) 51 0 and communication circuitry 520) can be wide-band. In various aspects of the second set of techniques, a wideband beamformed CSI-RS (e.g., channel estimation CSI-RS) signal (e.g., generated by processor(s) 510) can be transmitted (e.g., by communication circuitry 520) occupying one or two symbols in a subframe (e.g., or slot). The beamformed transmission can be to a particular user or a group of users. For the ZT/GI-DFT-s-OFDM waveform, there is an additional constraint on the tail part of each transmitted symbol to be zero. As a result, for the GI/ZT-DFT-s-OFDM waveform, a carefully designed interpolated Zadoff- chu (ZC) sequence can be employed for channel estimation CSI-RS (e.g., generated by processor(s) 510 and transmitted by communication circuitry 520) in accordance with the second set of techniques. A carefully designed "interpolated" ZC sequence in the frequency domain can have a zero-tail in the time domain. Also, while such interpolated sequences do not directly have all the desired properties of the original sequence, a good receiver can exploit the underlying good properties of the ZC sequence from the interpolated version to achieve better estimation performance of the channel state information.

[00114] In various aspects, the second set of techniques can be employed for determining channel state information based on channel estimation CSI-RS (e.g., generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410) for a high band cellular system using CP-DFT-s-OFDM or ZT/GI-DFT-s-OFDM access waveform. The CSI-RS design of the second set of techniques can be employed to support up to 16 antenna/beam ports.

[00115] Referring to FIG. 12, illustrated is a pair of diagrams showing two types of self-contained subframe (or slot) structures that can be employed in connection with various aspects discussed herein. As shown in FIG. 12, a wideband channel estimation CSI-RS (e.g., generated by processor(s) 510) can be placed at one of the two possible positions in Type-1 subframe (or slot) and at one position in Type-2 subframe (or slot) (e.g., as mapped to resources by processor(s) 510 and transmitted by communication circuitry 520). A channel estimation CSI-RS following DCI (Downlink Control lnformation)/PDCCH (Physical Downlink Control Channel) can be more suitable for periodical scheduling or CSI reporting (e.g., generated by processor(s) 410, transmitted via transceiver circuitry 420, received via communication circuitry 520, and processed by processor(s) 51 0), while the one following PDSCH (Physical Downlink Shared Channel) in the type-1 subframe (or slot) can be more suitable for aperiodic scheduling and reporting of CSI (e.g., generated by processor(s) 410, transmitted via transceiver circuitry 420, received via communication circuitry 520, and processed by processor(s) 51 0).

[00116] In various aspects, channel estimation CSI-RS (e.g., generated by

processor(s) 510) when transmitted (e.g., by communication circuitry 520), can occupy either one or two symbols, with each symbol supporting up to 8 antenna/beam ports.

[00117] Channel Estimation CSI-RS for high band system using CP-DFT-s-OFDM waveform: Various aspects of the second set of techniques can facilitate generation of CSI (e.g., by processor(s) 410) based on channel estimation CSI-RS (e.g., generated by processor(s) 51 0, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410) in high band systems using a CP (Cyclic Prefix)-DFT-s-OFDM waveform. Each CSI-RS symbol can support up to 8 antenna/beam ports. Referring to FIG. 13, illustrated is a map of CSI-RS resource within one physical resource block (PRB), in connection with various aspects discussed herein.

[00118] A pair of consecutive sub-carriers can form a CRG (CSI-RS Resource Group) that can support two distinct polarizations (e.g., vertical (V) and horizontal (H) polarizations) of a single beam. Further code division multiplexing across V/H polarizations of a beam can be supported using a length two orthogonal cover code (OCC). If there is a second channel estimation channel estimation CSI-RS symbol, a length 4 OCC can be used (e.g., for encoding by processor(s) 510 and decoding by processor(s) 410) to spread a beam port across 4 resource elements (RE).

[00119] In various aspects, ZC-sequences of an appropriate length (e.g., equal to the number of PRB's used for channel estimation CSI-RS) can be employed (e.g., by processor(s) 510) for channel estimation CSI-RS of each port. V-polarization and H- polarization ports of the same beam can use ZC sequences with an identical root but with different cyclic shifts (e.g., as selected by processor(s) 510 and applied by communication circuitry 520).

[00120] Channel Estimation CSI-RS for high band system using ZT/GI-DFT-s- OFDM waveform: Various aspects of the second set of techniques can facilitate generation of CSI (e.g., by processor(s) 410) based on channel estimation CSI-RS (e.g., generated by processor(s) 51 0, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410) in high band systems using a ZT-DFT-s-OFDM waveform or a GI-DFT-s-OFDM waveform. The Gl- DFT-s-OFDM (or ZT-DFT-s-OFDM) symbol structure imposes a constraint that the tail samples of each symbol comprise a predetermined fixed GI (or a zero) sequence. Such a constraint on time-domain samples implies that the frequency domain of the GI-DFT- s-OFDM symbol cannot take arbitrary desired values. This limits the frequency division multiplexing (FDM) options of the channel estimation CSI-RS of different beam/antenna ports. In various aspects, an interpolated ZC sequence as discussed herein can be employed in the frequency domain for channel estimation CSI-RS.

[00121 ] Referring to FIG. 14, illustrated is a diagram showing an example of generation of a GI-DFT-s-OFDM channel estimation CSI-RS symbol for one

beam/antenna port using an interpolated ZC sequence, according to various aspects discussed herein. When N is the total number of samples in a GI-DFT-s-OFDM symbol; NGI is the length of the GI (or zero tail) sequence; M is the DFT spread size (where M < N), then the length N _zc of the used ZC sequence is a largest prime satisfying equation (1 ):

\N. N _ZC /M]≤N - N _GI

[00122] In various aspects, channel estimation CSI-RS of multiple ports for a GI-DFT- s-OFDM (or ZT-DFT-s-OFDM) waveform can be multiplexed (e.g., by processor(s) 510 and communication circuitry 520). Referring to FIG. 15, illustrated is an example of multiplexing channel estimation CSI-RS of two ports using different cyclic shifts of a ZC sequence, according to various aspects discussed herein.

[00123] Cyclic shifts of ZC sequences: In various aspects, according to one option for multiplexing channel estimation CSI-RS of different beam/antenna ports, different cyclic shifts of the same ZC sequence can be employed (e.g., by processor(s) 510 and communication circuitry 520). For example, in FIG. 15, beam/antenna port-0 can use (e.g., as generated by processor(s) 510 and transmitted by communication circuitry 520) a ZC sequence with root 'u' and a cyclic shift of n ₀ , while beam/antenna port-2 can use (e.g., as generated by processor(s) 510 and transmitted by communication circuitry 520) a ZC sequence with root 'u' and cyclic shift of rii . In various aspects, these techniques can be extended for multiplexing more than two ports. The number and amount of cyclic shifts can be provisioned based on a delay spread profile in the system (e.g., by one or more systems 500, by other network elements, etc.). The channel estimation CSI-RS of neighboring cells can use a base ZC sequence with different root indices than a given cell (e.g., employing system 500).

[00124] Combination of cyclic shift of ZC sequences and frequency division multiplexing: Referring to FIG. 16, illustrated is a diagram showing an example of multiplexing channel estimation CSI-RS of 4 beam/antenna ports using a combination of CDM (e.g., cyclic shifts of ZC sequence) and FDM, according to various aspects discussed herein. As an example, referring again to FIG. 16, channel estimation CSI-RS of ports 0 and 2 can be multiplexed (e.g., by processor(s) 510 and communication circuitry 520) using CDM (using distinct cyclic shifts of a ZC sequence) and can be loaded on even sub-carriers (e.g., via mapping by processor(s) 510 and transmission by communication circuitry 520), while ports 1 and 3 can be loaded on odd sub-carriers (e.g., via mapping by processor(s) 51 0 and transmission by communication circuitry 520) and again multiplexed using CDM (e.g., by processor(s) 510 and communication circuitry 520).

[00125] Alternative transmitter architecture for GI-DFT-s-OFDM waveform: FIGS. 15 and 16 show transmitter architectures where the Gl sequence can be added in the time- domain. In various aspects, an alternative transmitter architecture can be employed, which can add the Gl sequence before the DFT spread. Referring to FIG. 17, illustrated is an example alternative architecture for multiplexing channel estimation CSI-RS of two ports with addition of the Gl sequence before the DFT spread, according to various aspects discussed herein. In the example of FIG. 17, since the Gl sequence is added in both the chains, it is scaled appropriately. Similar techniques can be employed for multiplexing other numbers of ports.

[00126] Referring to FIG. 18, illustrated is an example of another alternative architecture for multiplexing channel estimation CSI-RS of two ports with the Gl sequence added to only one port (port 0), according to various aspects discussed herein. Similar techniques can be employed for multiplexing other numbers of ports.

[00127] In various aspects, the number of CSI-RS ports can be configured in a cell- specific manner by a BS through higher layer signaling (e.g., generated by processor(s) 51 0, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410).

[00128] Power boosting: In various aspects, in scenarios wherein ports are multiplexed using FDM in connection with any variations or aspects of the second set of techniques, appropriate power boosting (e.g., as selected by processor(s) 510) can be applied (e.g., by communication circuitry 520) to improve the coverage or CSI estimation performance.

[00129] A first example embodiment of the second set of techniques can be employed (e.g., by system 400 and system 500) by a UE (e.g., employing system 400) communicating with a high band (mmWave) base station (BS) (e.g., employing system 500), wherein the BS can generate (e.g., via processor(s) 510) channel estimation CSI- RS that can be employed for CSI estimation (e.g., based on measurements by processor(s) 410 of the channel estimation CSI-RS received via transceiver circuitry 420) at a UE.

[00130] In various aspects of the first example embodiment of the second set of techniques, TDD communications can be employed between the BS and UE, at high frequency bands using one of a CP-DFT-s-OFDM or ZT/GI-DFT-s-OFDM waveform for radio access link (e.g., with signals/messages generated and/or processed at processor(s) 410 and processor(s) 510, and transmitted and/or received at transceiver circuitry 420 and communication circuitry 520).

[00131 ] In various aspects of the first example embodiment of the second set of techniques, each CSI-RS symbol (e.g., generated by processor(s) 510) can support up to 8 ports. In various such aspects, for a CP-DFT-s-OFDM waveform, generating the channel estimation CSI-RS can comprise using (e.g., via processor(s) 51 0 and communication circuitry 520) ZC-sequences with optional orthogonal cover codes across frequency and/or time. In various such aspects, generating the channel estimation CSI-RS for V and H polarized ports of the same beam can comprise using (e.g., via processor(s) 510 and communication circuitry 520) ZC sequences with identical root but different cyclic shifts. In various such aspects, for a ZT/GI-DFT-s- OFDM waveform, generating the channel estimation CSI-RS can comprise using (e.g., via processor(s) 510 and communication circuitry 520) an interpolated ZC sequence generated by DFT spreading zero padded ZC sequence. In various such aspects, the multiplexing of multiple ports can comprise using the same ZC sequence with distinct cyclic shifts for each port prior to DFT spreading (e.g., via processor(s) 510 and communication circuitry 520). In various such aspects, channel estimation CSI-RS corresponding to different ports can also be multiplexed (e.g., by processor(s) 510) in a frequency division manner, for example, to occupy disjoint sets of sub-sampled sub- carriers. In various such aspects, additional ports of channel estimation CSI-RS can be multiplexed (e.g., by processor(s) 510) using cyclic shifts of ZC sequences. [00132] In a second example embodiment of the second set of techniques, an apparatus (e.g., comprising system 500) can be employed by a BS to construct (e.g., via processor(s) 510) and transmit (e.g., via communication circuitry 520) the channel estimation CSI-RS of various aspects of the first example embodiment of the second set of techniques associated with ZT/GI-DFT-s-OFDM waveforms, wherein the apparatus can (e.g., via processor(s) 510 and/or communication circuitry 520): (a) generate the appropriate ZC sequence and inserts the correct number of zeros or a Gl sequence equivalent, (b) implement DFT-spreading to form an interpolated ZC sequence in the frequency domain, and (c) apply IDFT to form a time-domain signal.

[00133] Referring to FIG. 19, illustrated is a flow diagram of an example method 1 900 employable at a UE that facilitates generation of CSI based on channel estimation CSI- RS in connection with a DFT spread waveform, according to various aspects discussed herein. In other aspects, a machine readable medium can store instructions associated with method 1900 that, when executed, can cause a UE to perform the acts of method 1900.

[00134] At 1910, channel estimation CSI-RS based on a ZC sequence can be received via one or more DFT spread symbols.

[00135] At 1920, one or more CSI parameters can be measured based on the channel estimation CSI-RS.

[00136] At 1930, a CSI report can be transmitted indicating the one or more CSI parameters.

[00137] Additionally or alternatively, method 1900 can include one or more other acts described herein in connection with system 400 and the second set of techniques.

[00138] Referring to FIG. 20, illustrated is a flow diagram of an example method 2000 employable at a BS that facilitates generation of channel estimation CSI-RS for a DFT spread waveform, according to various aspects discussed herein. In other aspects, a machine readable medium can store instructions associated with method 2000 that, when executed, can cause a BS to perform the acts of method 2000.

[00139] At 2010, channel estimation CSI-RS based on a ZC sequence can be transmitted via one or more DFT spread symbols.

[00140] At 2020, a CSI report can be received indicating one or more CSI parameters as measured by a UE based on the received channel estimation CSI-RS.

[00141 ] Additionally or alternatively, method 2000 can include one or more other acts described herein in connection with system 500 and the second set of techniques. CSI-RS design for NR (New Radio) systems

[00142] The third set of techniques, in various aspects, can comprise a design for non-precoded channel estimation CSI-RS, along with the resource mapping and various options for multiplexing channel estimation CSI-RS of multiple antenna ports for 5G (Fifth Generation) wireless systems using new radio access technology (NR). The 5G wireless systems using NR are expected to operate in both low (sub 6GHz) and high (above 6GHz) frequency bands.

[00143] In 5G NR systems, operating at high band, Hybrid Antenna Architectures (HAA) can be employed due to their cost-performance benefit. Hybrid antenna architectures have a higher number of antenna elements than the number of RF-chains and the Ml MO beam-forming can be split between analog and digital domain. The analog component of beam forming is affected by phase only and hence is wide-band operation. Thus, if an antenna port is used (e.g., by processor(s) 510 and

communication circuitry 520) for transmission of channel estimation CSI-RS in a certain beam direction, that antenna port cannot transmit other information or channel in a different beam direction. This limits the multiplexing capabilities of transmission (e.g., via communication circuitry 520) of channel estimation CSI-RS (e.g., generated by processor(s) 510) with other channels. Also, at higher frequencies, low peak-to- average-power-ratio (PAPR) of the transmitted signal can be advantageous to support enhanced coverage. In order to solve both these issues simultaneously, in various aspects of the third set of techniques, non-precoded channel estimation CSI-RS in NR using Zadoff-Chu (ZC) sequences (e.g., generated by processor(s) 510 and

communication circuitry 520) can be mapped on dedicated symbols (e.g., OFDM, DFT- spread, etc.) with no other channels multiplexed (e.g., by processor(s) 51 0 and communication circuitry 520).

[00144] Various aspects of the third set of techniques can be employed to generated non-precoded channel estimation CSI-RS for high band 5G systems using NR.

[00145] Dedicated OFDM symbol for CSI-RS transmission: The Ml MO

beamforming operation of a HAA (e.g., employed by system 500, etc.), used in 5G NR systems, comprises both analog and digital components. The analog component of beam forming is affected by phase only and hence is a wide-band operation. Thus, if an antenna port is used for transmission (e.g., via communication circuitry 520) of channel estimation CSI-RS (e.g., generated by processor(s) 510) in a certain beam direction (e.g., associated with beamforming weights selected by processor(s) 510 and applied by communication circuitry 520), that port cannot transmit other information or channel in a different beam direction. As a result, in various aspects of the third set of techniques, non precoded channel estimation CSI-RS (e.g., generated by processor(s) 51 0) can be transmitted (e.g., via communication circuitry 520) via multiple antenna ports in NR using one or more dedicated symbols (e.g., dedicated to channel estimation CSI-RS, such that no other (e.g., non-CSI-RS) channels are multiplexed).

[00146] Number of OFDM symbols used for CSI-RS transmission and position within a subframe: In various aspects of the third set of techniques, dedicated OFDM symbols used for the transmission (e.g., via communication circuitry 520) channel estimation CSI-RS of multiple antenna ports can be co-located (e.g., in one or more sets that can each comprise channel estimation CSI-RS of two or more antenna ports, for example, a pair, two pairs, a set of four, etc.). The number of symbols (e.g., OFDM, DFT spread, etc.) used for the transmission (e.g., via communication circuitry 520) of channel estimation CSI-RS (e.g., generated by processor(s) 510) and the offset (in terms of number of OFDM symbols from the beginning of the sub-frame) of the first OFDM symbol carrying the CSI-RS can be configured dynamically based on the use case scenario (e.g., via DCI generated by processor(s) 510, transmitted via

communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410).

[00147] CSI reference signal, resource mapping and antenna port multiplexing:

In various aspects, channel estimation CSI-RS (e.g., generated by processor(s) 510) and resource mapping (e.g., by processor(s) 510) can follow the common reference signal design principles such as constant modulus and uniform spacing in frequency domain, full power utilization, inter-cell interference measurement and management capability, and can support additional features based on NR constraints, such as uniform design for low and high band, support for flexible bandwidth allocation and multiple numerology. Additionally, for coverage enhancement, especially at high band, CSI-RS with low PAPR and full power utilization can be employed. Thus, in various aspects, Zadoff-Chu (ZC) sequences can be employed (e.g., by processor(s) 51 0) for channel estimation CSI-RS (e.g., generated by processor(s) 510) in NR systems.

[00148] In addition to satisfying the basic reference signal properties mentioned above, ZC sequences have zero-auto correlation and the best cross correlation for prime lengths. ZC sequences also have low PAPR. One concern in constructing ZC sequences is the relative inflexibility in the terms of sequence lengths. So in order to support flexible bandwidth assignments for NR CSI-RS, in various aspects, a BS can employ block-wise ZC sequences and/or ZC sequences with cyclic extensions (e.g., via generation of such sequences by processor(s) 510).

[00149] In various aspects, channel estimation CSI-RS of multiple ports from the same BS/gNB/eNB/TRP can be multiplexed (e.g., by processor(s) 510), for example based on cyclic shift of ZC sequences, interleaved FDM (IFDM) as discussed herein, or both.

[00150] Cyclic shifts of ZC sequences: One option for multiplexing (e.g., via processor(s) 510) channel estimation CSI-RS (e.g., generated by processor(s) 510) of different antenna ports is using different cyclic shifts of ZC sequences. The channel estimation CSI-RS of neighboring cells can use different root values and/or can be scheduled in different sub-frames, slots, or symbols to avoid or minimize the channel estimation CSI-RS interference. Further, if more than one symbol is used for CSI-RS transmission in a sub-frame/slot/etc. (e.g., by processor(s) 510 and communication circuitry 520), symbol-wise OCC-2 spreading across time can be applied (e.g., by processor(s) 510 and communication circuitry 520) for full power utilization.

[00151 ] Referring to FIG. 21 , illustrated is a diagram of an example of multiplexing CSI-RS of 16 antenna ports in 2 CSI-RS OFDM symbols using different cyclic shifts (e.g., n0,..., n15) of the same ZC sequence 'X' and symbol-wise spreading using OCC- 2, according to various aspects discussed herein. The total allocated bandwidth can be such that the length of the sequence X is greater than 16.

[00152] Combination of interleaved frequency division multiplexing (IFDM) and cyclic shifts of ZC sequences: Another option for multiplexing (e.g., by processor(s) 510) channel estimation CSI-RS (e.g., generated by processor(s) 510) of different antenna ports from the same BS/gNB/eNB/TRP is to employ IFDM (e.g., via resource mapping by processor(s) 51 0 and transmission by communication circuitry 520) alone or in addition to cyclic shifts of ZC sequences. Referring to FIG. 22, illustrated is a diagram showing an example of IFDM comprising two combs with 8 antenna ports multiplexed on each comb, according to various aspects discussed herein. On the comb indicated in FIG. 22 via diagonal hatching, 8 antenna ports can be multiplexed (e.g., by processor(s) 51 0) using different cyclic shifts n0,...,n7 of a ZC sequence X. The other comb can also be used to multiplex (e.g., by processor(s) 510) and transmit (e.g., via communication circuitry 520) channel estimation CSI-RS for 8 more antenna ports (using different cyclic shifts n0, ...,n7 of the ZC sequence X). The sub-sampled structure of channel estimation CSI-RS in the frequency domain results in two repeated copies of the time-domain signal. The time-domain repeated copies can be potentially used by UE (e.g., employing system 400) to measure CSI (e.g., by processor(s) 410 of channel estimation CSI-RS received via transceiver circuitry 420) using two different Rx directions.

[00153] A first example embodiment of the third set of techniques can be employed (e.g., by system 400 and system 500) by a UE (e.g., employing system 400)

communicating with a high band (mmWave) base station (BS) (e.g., employing system 500), wherein the BS (e.g., gNB, eNB, TRP, etc.) can generate (e.g., via processor(s) 51 0) channel estimation CSI-RS for CSI estimation (e.g., via processor(s) 410) at the UE. In various aspects, the BS and UE can communicate via one of a wide range (below and above 6GHz up to 70GHz) of frequency bands using either OFDM or DFT-s- OFDM waveform for radio access link.

[00154] In various aspects of the first example embodiment of the third set of techniques, one or more symbols can be dedicated for transmission (e.g., via

communication circuitry 520) of channel estimation CSI-RS (e.g., generated by processor(s) 510) corresponding to multiple antenna ports. In various such aspects, the symbols carrying channel estimation CSI-RS can be co-located within a sub-frame (e.g., one or more sets of adjacent symbols, with each set comprising two or more symbols). In various such aspects, the number and the position (within the sub-frame) of the channel estimation CSI-RS symbols (e.g., generated by processor(s) 510) and the subcarriers used for channel estimation CSI-RS transmission (e.g., by communication circuitry 520) in a sub-frame can be configured dynamically (e.g., via DCI (Downlink Control Information) generated by processor(s) 510, transmitted via communication circuitry 520, received via transceiver circuitry 420, and processed by processor(s) 410). In various such aspects, the Zadoff-Chu sequences can be used (e.g., by processor(s) 51 0 for measurement by processor(s) 410) as channel estimation CSI-RS for the antenna ports. In various such aspects, the Zadoff-Chu sequences can be either cyclically extended or used in a block wise fashion (e.g., by processor(s) 510) to accommodate a wide range of sub-band transmissions (e.g., via communication circuitry 520). In various such aspects, multiple antenna ports of the BS (e.g., employing system 500) can be multiplexed using different cyclic shifts of the same Zadoff-Chu sequence (e.g., by processor(s) 51 0). In various such aspects, multiple antenna ports of the BS can be multiplexed (e.g., by processor(s) 510) using interleaved frequency division multiplexing (IFDM) using a comb structure (e.g., as discussed above). In various such aspects, multiple antenna ports of the BS can be multiplexed (e.g., by processor(s) 510) using a combination of the cyclic shifts and IFDM. In various such aspects, when multiple symbols (e.g., OFDM, DFT spread, etc.) are used for transmission (e.g., by communication circuitry 520) of channel estimation CSI-RS (e.g., by processor(s) 51 0) in a subframe or slot, they can be further spread in the time domain (e.g., by processor(s) 510) using orthogonal overlap codes of lengths 2, 4 or 8.

[00155] Referring to FIG. 23, illustrated is a flow diagram of an example method 2300 employable at a UE that facilitates generation of CSI based on channel estimation CSI- RS transmitted via one or more dedicated symbols, according to various aspects discussed herein. In other aspects, a machine readable medium can store instructions associated with method 2300 that, when executed, can cause a UE to perform the acts of method 2300.

[00156] At 2310, channel estimation CSI-RS based on a ZC sequence can be received via one or more dedicated CSI-RS symbols.

[00157] At 2320, one or more CSI parameters can be measured based on the channel estimation CSI-RS.

[00158] At 2330, a CSI report can be transmitted indicating the one or more CSI parameters.

[00159] Additionally or alternatively, method 2300 can include one or more other acts described herein in connection with system 400 and the third set of techniques.

[00160] Referring to FIG. 24, illustrated is a flow diagram of an example method 2400 employable at a BS that facilitates generation of channel estimation CSI-RS for transmission via one or more dedicated symbols, according to various aspects discussed herein. In other aspects, a machine readable medium can store instructions associated with method 2400 that, when executed, can cause a BS to perform the acts of method 2400.

[00161 ] At 2410, channel estimation CSI-RS based on a ZC sequence can be transmitted via one or more dedicated CSI-RS symbols.

[00162] At 2420, a CSI report can be received indicating one or more CSI parameters as measured by a UE based on the received channel estimation CSI-RS.

[00163] Additionally or alternatively, method 2400 can include one or more other acts described herein in connection with system 500 and the third set of techniques.

[00164] Although, for ease of illustration, the first, second, and third sets of techniques discussed herein are discussed separately, in various embodiments, aspects of two or more of these sets of techniques can be employed together. As one example, in various embodiments, various aspects of the second set of techniques can be employed in connection with the dedicated channel estimation CSI-RS symbols discussed in connection with the third set of techniques, for example, via two or more dedicated symbols co-located in one or more pairs of symbols.

[00165] Examples herein can include subject matter such as a method, means for performing acts or blocks of the method, at least one machine-readable medium including executable instructions that, when performed by a machine (e.g., a processor with memory, an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like) cause the machine to perform acts of the method or of an apparatus or system for concurrent communication using multiple communication technologies according to embodiments and examples described.

[00166] Example 1 is an apparatus configured to be employed in a UE (User

Equipment), comprising: a memory interface; and processing circuitry configured to: process a set of channel estimation CSI (Channel State lnformation)-RS (Reference Signal) from one or more symbols of an OFDM (Orthogonal Frequency Division)-based waveform, wherein the set of channel estimation CSI-RS is based at least in part on a ZC (Zadoff-Chu) sequence; measure one or more CSI parameters based on the set of channel estimation CSI-RS; generate a CSI report that indicates the one or more CSI parameters; and send the measured one or more CSI parameters to a memory via the memory interface.

[00167] Example 2 comprises the subject matter of any variation of any of example(s) 1 , wherein the OFDM-based waveform is an OFDM waveform or a CP (Cyclic Prefix)- DFT (Discrete Fourier Transform)-s (spread)-OFDM waveform.

[00168] Example 3 comprises the subject matter of any variation of any of example(s) 1 , wherein the OFDM-based waveform is a ZT (Zero Tail)-DFT-s-OFDM waveform, or a Gl (Guard lnterval)-DFT-s-OFDM waveform.

[00169] Example 4 comprises the subject matter of any variation of any of example(s) 3, wherein the channel estimation CSI-RS comprises an interpolated ZC sequence based on the ZC sequence.

[00170] Example 5 comprises the subject matter of any variation of any of example(s) 1 -4, wherein the one or more symbols are one or more dedicated symbols for channel estimation CSI-RS.

[00171 ] Example 6 comprises the subject matter of any variation of any of example(s) 1 -4, wherein the one or more symbols comprise two or more co-located symbols.

[00172] Example 7 comprises the subject matter of any variation of any of example(s) 6, wherein the one or more symbols comprise one of: a pair of co-located symbols, three co-located symbols, four co-located symbols, or two pairs of co-located symbols. [00173] Example 8 comprises the subject matter of any variation of any of example(s) 1 -4, wherein the processing circuitry is further configured to decode a DCI (Downlink Control Information) message that indicates a number and positioning of the one or more symbols.

[00174] Example 9 comprises the subject matter of any variation of any of example(s) 1 -5, wherein the one or more symbols comprise two or more co-located symbols.

[00175] Example 10 comprises the subject matter of any variation of any of example(s) 1 -7, wherein the processing circuitry is further configured to decode a DCI (Downlink Control Information) message that indicates a number and positioning of the one or more symbols.

[00176] Example 1 1 comprises the subject matter of any variation of any of example(s) 1 , wherein the set of channel estimation CSI-RS one of comprise a cyclic extension of the ZC sequence or employ the ZC sequence in a block-wise manner.

[00177] Example 12 comprises the subject matter of any variation of any of example(s) 1 , wherein the set of channel estimation CSI-RS comprise a first channel estimation CSI-RS based on a first cyclic shift of the ZC sequence that is associated with a first antenna port and a second channel estimation CSI-RS based on a second cyclic shift of the ZC sequence that is associated with a second antenna port.

[00178] Example 13 comprises the subject matter of any variation of any of example(s) 12, wherein the first antenna port and the second antenna port are associated with distinct polarizations of a common beam, and wherein both the first channel estimation CSI-RS and the second channel estimation CSI-RS are based on a common root of the ZC sequence.

[00179] Example 14 comprises the subject matter of any variation of any of example(s) 1 , wherein the set of channel estimation CSI-RS comprises a first subset of channel estimation CSI-RS from a first comb comprising a first set of subcarriers multiplexed via IFDM (Interleaved Frequency Division Multiplexing) with a second subset of channel estimation CSI-RS from a second comb comprising a disjoint second set of subcarriers, wherein the first subset of channel estimation CSI-RS is associated with a first set of antenna ports and the second subset of channel estimation CSI-RS is associated with a second set of antenna ports.

[00180] Example 15 comprises the subject matter of any variation of any of example(s) 1 , wherein the one or more symbols comprise two or more symbols spread in the time domain via OCCs (Orthogonal Cover Codes) of length 2, 4, or 8. [00181 ] Example 16 comprises the subject matter of any variation of any of example(s) 1 , wherein each symbol of the one or more symbols comprises channel estimation CSI-RS for eight or fewer antenna ports associated with that symbol.

[00182] Example 17 is an apparatus configured to be employed in a gNB (next Generation Node B), comprising: a memory interface; and processing circuitry configured to: generate a set of channel estimation CSI (Channel State lnformation)-RS (Reference Signal) based at least in part on a ZC (Zadoff-Chu) sequence; map the set of channel estimation CSI-RS to one or more symbols, wherein each of the one or more symbols has an OFDM (Orthogonal Frequency Division)-based waveform; and send one or more characteristics of the ZC sequence to a memory via the memory interface.

[00183] Example 18 comprises the subject matter of any variation of any of example(s) 17, wherein the one or more symbols comprise two or more co-located symbols.

[00184] Example 19 comprises the subject matter of any variation of any of example(s) 18, wherein the one or more symbols comprise one of: a pair of co-located symbols, three co-located symbols, four co-located symbols, or two pairs of co-located symbols.

[00185] Example 20 comprises the subject matter of any variation of any of example(s) 17-19, wherein the processing circuitry is further configured to encode a DCI (Downlink Control Information) message that indicates a number and positioning of the one or more symbols.

[00186] Example 21 comprises the subject matter of any variation of any of example(s) 17-19, wherein the processing circuitry is configured to generate the set of channel estimation CSI-RS based on one of a cyclic extension of the ZC sequence or via employing the ZC sequence in a block-wise manner.

[00187] Example 22 comprises the subject matter of any variation of any of example(s) 17-19, wherein the processing circuitry is configured to generate a first channel estimation CSI-RS of the set of channel estimation CSI-RS based on a first cyclic shift of the ZC sequence and to generate a second channel estimation CSI-RS of the set of channel estimation CSI-RS based on a second cyclic shift of the ZC sequence, wherein the first channel estimation CSI-RS is associated with a first antenna port and the second channel estimation CSI-RS is associated with a second antenna port.

[00188] Example 23 comprises the subject matter of any variation of any of example(s) 22, wherein the first antenna port and the second antenna port are associated with distinct polarizations of a common beam, and wherein the processing circuitry is configured to generate both the first channel estimation CSI-RS and the second channel estimation CSI-RS based on a common root of the ZC sequence.

[00189] Example 24 comprises the subject matter of any variation of any of example(s) 17-19, wherein the processing circuitry is further configured to multiplex a first subset of the set of channel estimation CSI-RS with a second subset of the set of channel estimation CSI-RS via IFDM (Interleaved Frequency Division Multiplexing) by mapping the first subset to a first comb comprising a first set of subcarriers and mapping the second subset to a second comb comprising a disjoint second set of subcarriers, wherein the first subset of channel estimation CSI-RS is associated with a first set of antenna ports and the second subset of channel estimation CSI-RS is associated with a second set of antenna ports.

[00190] Example 25 comprises the subject matter of any variation of any of example(s) 17-19, wherein the one or more symbols comprise two or more symbols, and wherein the processing circuitry is further configured to spread the two or more symbols in the time domain via OCCs (Orthogonal Cover Codes) of length 2, 4, or 8.

[00191 ] Example 26 comprises the subject matter of any variation of any of example(s) 17-19, wherein each symbol of the one or more symbols comprises channel estimation CSI-RS for eight or fewer antenna ports associated with that symbol.

[00192] Example 27 comprises the subject matter of any variation of any of example(s) 17-20, wherein the processing circuitry is configured to generate the set of channel estimation CSI-RS based on one of a cyclic extension of the ZC sequence or via employing the ZC sequence in a block-wise manner.

[00193] Example 28 comprises the subject matter of any variation of any of example(s) 17-21 , wherein the processing circuitry is configured to generate a first channel estimation CSI-RS of the set of channel estimation CSI-RS based on a first cyclic shift of the ZC sequence and to generate a second channel estimation CSI-RS of the set of channel estimation CSI-RS based on a second cyclic shift of the ZC sequence, wherein the first channel estimation CSI-RS is associated with a first antenna port and the second channel estimation CSI-RS is associated with a second antenna port.

[00194] Example 29 comprises the subject matter of any variation of any of example(s) 17, wherein the OFDM-based waveform is an OFDM waveform or a CP (Cyclic Prefix)-DFT (Discrete Fourier Transform)-s (spread)-OFDM waveform. [00195] Example 30 comprises the subject matter of any variation of any of example(s) 17, wherein the OFDM-based a ZT (Zero Tail)-DFT-s-OFDM waveform, or a Gl (Guard lnterval)-DFT-s-OFDM waveform.

[00196] Example 31 comprises the subject matter of any variation of any of example(s) 30, wherein the channel estimation CSI-RS comprises an interpolated ZC sequence, and wherein the processing circuitry is further configured to generate the interpolated ZC sequence by zero padding and DFT spreading the ZC sequence.

[00197] Example 32 comprises the subject matter of any variation of any of example(s) 30, wherein the set of channel estimation CSI-RS comprises a first channel estimation CSI-RS associated with a first antenna port and a first cyclic shift of the ZC sequence and a second channel estimation CSI-RS associated with a second antenna port and a second cyclic shift of the ZC sequence, wherein the processing circuitry is further configured to apply DFT spreading to the ZC sequence.

[00198] Example 33 comprises the subject matter of any variation of any of example(s) 17, wherein the one or more symbols are one or more dedicated symbols for channel estimation CSI-RS.

[00199] Example 34 is an apparatus configured to be employed in a UE (User Equipment), comprising: a memory interface; and processing circuitry configured to: select a distinct set of beamforming weights for each of a plurality of repetitions of beam management CSI (Channel State lnformation)-RS (Reference Signals) for each of one or more symbols; measure the beam management CSI-RS for each of the selected distinct sets of beamforming weights; select a first set of the distinct sets of

beamforming weights for DL (Downlink) beamforming based on the measured beam management CSI-RS for each of the selected distinct sets of beamforming weights; and send the first set of beamforming weights to a memory via the memory interface.

[00200] Example 35 comprises the subject matter of any variation of any of example(s) 34, wherein the beam management CSI-RS is based at least in part on a selected sequence, wherein the selected sequence is one of a ZC (Zadoff-Chu) sequence or a PN (Pseudo-Noise) sequence.

[00201 ] Example 36 comprises the subject matter of any variation of any of example(s) 34, wherein the beam management CSI-RS is associated with a first BS (Base Station), and wherein the processing circuitry is further configured to apply at least one of time filtering, frequency filtering, or correlation to distinguish additional beam management CSI-RS associated with one or more additional BSs. [00202] Example 37 comprises the subject matter of any variation of any of example(s) 34-36, wherein the one or more symbols comprise one or more ZT (Zero Tail)-DFT (Discrete Fourier Transform)-s (spread)-OFDM (Orthogonal Frequency Division Multiplexing) symbols.

[00203] Example 38 comprises the subject matter of any variation of any of example(s) 34-36, wherein the one or more symbols comprise one or more Gl (Guard lnterval)-DFT (Discrete Fourier Transform)-s (spread)-OFDM (Orthogonal Frequency Division Multiplexing) symbols.

[00204] Example 39 comprises the subject matter of any variation of any of example(s) 38, wherein the one or more GI-DFT-s-OFDM symbols comprise a shortened Gl.

[00205] Example 40 comprises the subject matter of any variation of any of example(s) 38, wherein a Gl of each of the one or more symbols comprises the plurality of repetitions of beam management CSI-RS for that symbol.

[00206] Example 41 comprises the subject matter of any variation of any of example(s) 40, wherein the processing circuitry is configured to decode a first DCI (Downlink Control Information) message that indicates that the Gl of each of the one or more symbols comprises the plurality of repetitions of beam management CSI-RS for that symbol.

[00207] Example 42 comprises the subject matter of any variation of any of example(s) 34, wherein the processing circuitry is further configured to process signaling that indicates a subcarrier sampling factor that is equal to the plurality of repetitions of beam management CSI-RS for each of the one or more symbols, wherein the signaling comprises one of higher layer signaling or a second DCI (Downlink Control Information) message that the processing circuitry is configured to decode.

[00208] Example 43 comprises the subject matter of any variation of any of example(s) 34, wherein the processing circuitry is configured to decode a third DCI (Downlink Control Information) message that indicates whether the beam management CSI-RS is UE-specific or is associated with a group of UEs.

[00209] Example 44 is an apparatus configured to be employed in a gNB (next Generation Node B), comprising: a memory interface; and processing circuitry configured to: identify a subcarrier sampling factor and an associated subset of subcarriers; generate a plurality of beam management CSI (Channel State Information)- RS (Reference Signals) based on a selected sequence, wherein the selected sequence is one of a ZC (Zadoff-Chu) sequence or a PN (Pseudo-Noise) sequence; map the plurality of beam management CSI-RS to the associated subset of subcarriers; and send the subcarrier sampling factor to a memory via the memory interface.

[00210] Example 45 comprises the subject matter of any variation of any of example(s) 44, wherein the processing circuitry is further configured to modulate the selected sequence based on an identifier of the gNB.

[00211 ] Example 46 comprises the subject matter of any variation of any of example(s) 44-45, wherein the processing circuitry is further configured to generate signaling that indicates the subcarrier sampling factor, wherein the signaling comprises one of higher layer signaling or a first DCI (Downlink Control Information) message that the processing circuitry is configured to encode.

[00212] Example 47 comprises the subject matter of any variation of any of example(s) 44-45, wherein the processing circuitry is configured to encode a second DCI (Downlink Control Information) message that indicates whether the beam management CSI-RS is UE (User Equipment)-specific or is associated with a group of UEs.

[00213] Example 48 comprises the subject matter of any variation of any of example(s) 44, wherein the processing circuitry is configured to identify the associated subset of subcarriers from a plurality of disjoint subsets of subcarriers.

[00214] Example 49 comprises the subject matter of any variation of any of example(s) 44, wherein the processing circuitry is further configured to select a root for the selected sequence based on an identifier of the gNB.

[00215] Example 50 comprises the subject matter of any variation of any of example(s) 44, wherein the one or more symbols comprise one or more ZT (Zero Tail)- DFT (Discrete Fourier Transform)-s (spread)-OFDM (Orthogonal Frequency Division Multiplexing) symbols.

[00216] Example 51 comprises the subject matter of any variation of any of example(s) 44, wherein the one or more symbols comprise one or more Gl (Guard lnterval)-DFT (Discrete Fourier Transform)-s (spread)-OFDM (Orthogonal Frequency Division Multiplexing) symbols.

[00217] Example 52 comprises the subject matter of any variation of any of example(s) 51 , wherein the one or more GI-DFT-s-OFDM symbols comprise a shortened Gl.

[00218] Example 53 comprises the subject matter of any variation of any of example(s) 51 , wherein a Gl of each of the one or more symbols comprises the plurality of repetitions of beam management CSI-RS for that symbol. [00219] Example 54 comprises the subject matter of any variation of any of example(s) 53, wherein the processing circuitry is configured to encode a third DCI (Downlink Control Information) message that indicates that the Gl of each of the one or more symbols comprises the plurality of repetitions of beam management CSI-RS for that symbol.

[00220] Example 55 comprises an apparatus comprising means for executing any of the described operations of examples 1 -54.

[00221 ] Example 56 comprises a machine readable medium that stores instructions for execution by a processor to perform any of the described operations of examples 1 - 54.

[00222] Example 57 comprises an apparatus comprising: a memory interface; and processing circuitry configured to: perform any of the described operations of examples 1 -54.

[00223] The above description of illustrated embodiments of the subject disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosed embodiments to the precise forms disclosed. While specific embodiments and examples are described herein for illustrative purposes, various modifications are possible that are considered within the scope of such embodiments and examples, as those skilled in the relevant art can recognize.

[00224] In this regard, while the disclosed subject matter has been described in connection with various embodiments and corresponding Figures, where applicable, it is to be understood that other similar embodiments can be used or modifications and additions can be made to the described embodiments for performing the same, similar, alternative, or substitute function of the disclosed subject matter without deviating therefrom. Therefore, the disclosed subject matter should not be limited to any single embodiment described herein, but rather should be construed in breadth and scope in accordance with the appended claims below.

[00225] In particular regard to the various functions performed by the above described components or structures (assemblies, devices, circuits, systems, etc.), the terms (including a reference to a "means") used to describe such components are intended to correspond, unless otherwise indicated, to any component or structure which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary implementations. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.