PRIORITY CLAIM

[0001] This application claims the benefit of priority to U.S. Provisional

Patent Application Serial No. 62/417,926, filed November 4, 2016, entitled "MOBILITY SUPPORT FOR 5G NR," which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] Embodiments pertain to radio access networks. Some embodiments relate to handover in cellular and wireless local area network (WLAN) networks, including Third Generation Partnership Project Long Term Evolution (3GPP LTE) networks and LTE advanced (LTE-A) networks as well as 4 ^th generation (4G) networks and 5 ^th generation (5G) networks.

BACKGROUND

[0003] The use of 3 GPP LTE systems (including both LTE and LTE-A systems) has increased due to both an increase in the types of devices user equipment (UEs) using network resources as well as the amount of data and bandwidth being used by various applications, such as video streaming, operating on these UEs. The latest generation (5G - also called new radio or NR) system may extend current multi-connectivity architecture to permit a UE to simultaneously connect to multiple 5G NR small cells. Due to the extended wavelengths used in NR, in particular in the high frequency (mmWave) band, handover may occur between a source evolved NodeB (eNB) (or gNB in 5G NR system) and target gNB relatively quickly. The rapid handover may result in a large amount of time that communications are interrupted.

BRIEF DESCRIPTION OF THE FIGURES

[0004] In the figures, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The figures illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

[0005] FIG. 1 illustrates an architecture of a system of a network in accordance with some embodiments.

[0006] FIG. 2 illustrates example components of a device in accordance with some embodiments.

[0007] FIG. 3 illustrates example interfaces of baseband circuitry in accordance with some embodiments.

[0008] FIG. 4 is an illustration of a control plane protocol stack in accordance with some embodiments.

[0009] FIG. 5 is an illustration of a user plane protocol stack in accordance with some embodiments.

[0010] FIG. 6 is a block diagram illustrating components, according to some example embodiments, able to read instructions from a machine -readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and perform any one or more of the methodologies discussed herein.

[0011] FIG. 7 illustrates an gNB to gNB change procedure in accordance with some embodiments.

[0012] FIG. 8 illustrates a 5G gNB to gNB change procedure in accordance with some embodiments.

DETAILED DESCRIPTION

[0013] The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims.

[0014] FIG. 1 illustrates an architecture of a system 100 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.

[0015] In some embodiments, any of the UEs 101 and 102 can comprise an Internet of Things (IoT) UE, which can comprise a network access layer designed for low-power IoT applications utilizing short-lived UE connections. An IoT 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 IoT networks. The M2M or MTC exchange of data may be a machine-initiated exchange of data. An IoT network describes interconnecting IoT UEs, which may include uniquely identifiable embedded computing devices (within the Internet infrastructure), with short-lived connections. The IoT UEs may execute background applications (e.g., keep-alive messages, status updates, etc.) to facilitate the connections of the IoT network.

[0016] The UEs 101 and 102 may be configured to connect, e.g., communicatively couple, with a radio access network (RAN) 110 - the RAN 110 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 5G protocol, a New Radio (NR) protocol, and the like. [0017] In this embodiment, the UEs 101 and 102 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).

[0018] 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 802.11 protocol, wherein the AP 106 would comprise a wireless fidelity (WiFi®) router. In this example, the AP 106 is shown to be connected to the Internet without connecting to the core network of the wireless system (described in further detail below).

[0019] The RAN 110 can include one or more access nodes that enable the connections 103 and 104. These access nodes (ANs) can be referred to as base stations (BSs), NodeBs, evolved NodeBs (eNBs), next Generation NodeBs (gigabit NodeBs - geNBs), 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 110 may include one or more RAN nodes for providing macrocells, e.g., macro RAN node 111, 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 112.

[0020] Any of the RAN nodes 111 and 112 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 111 and 112 can fulfill various logical functions for the RAN 110 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.

[0021] 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 111 and 112 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.

[0022] In some embodiments, a downlink resource grid can be used for downlink transmissions from any of the RAN nodes 111 and 112 to the UEs 101 and 102, 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.

[0023] 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 111 and 112 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 102.

[0024] 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=l, 2, 4, or 8).

[0025] 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.

[0026] The RAN 110 is shown to be communicatively coupled to a core network (CN) 120— via an S I interface 113. 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 S 1 interface 113 is split into two parts: the Sl-U interface 114, which carries traffic data between the RAN nodes 111 and 112 and the serving gateway (S-GW) 122, and the Sl- mobility management entity (MME) interface 115, which is a signaling interface between the RAN nodes 111 and 112 and MMEs 121.

[0027] In this embodiment, the CN 120 comprises the MMEs 121, 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.

[0028] The S-GW 122 may terminate the S I interface 113 towards the

RAN 110, and routes data packets between the RAN 110 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.

[0029] 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 101 and 102 via the CN 120.

[0030] 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.

[0031] 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 210, and power management circuitry (PMC) 212 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). [0032] 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.

[0033] 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 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.

[0034] 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).

[0035] 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.

[0036] 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.

[0037] 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 band-pass 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 lookup table based on a channel indicated by the applications processor 202. [0045] 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+l (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.

[0046] 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.

[0047] 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 210. 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. [0048] 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 210).

[0049] In some embodiments, the PMC 212 may manage power provided to the baseband circuitry 204. In particular, the PMC 212 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 212 may increase the power conversion efficiency while providing desirable implementation size and heat dissipation characteristics.

[0050] 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.

[0051] 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.

[0052] If there is no data traffic activity for an extended period of time, then the device 200 may transition to an RRC Idle state. In the RRC Idle state, the device 200 may disconnect from the network and avoid performing operations such as channel quality feedback, handover, etc. The device 200 may enter a very low power state and perform paging in which the device 200 may periodically wake up to listen to the network and then power down again. To receive data, the device 200 may transition back to the RRC_Connected state.

[0053] 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.

[0054] 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 (R C) 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.

[0055] 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-XT04E and a memory 204G utilized by said processors. Each of the processors 204A-XT04E may include a memory interface, 304A-XU04E, respectively, to send/receive data to/from the memory 204G.

[0056] 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 318 (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).

[0057] FIG. 4 is an illustration of a control plane protocol stack in accordance with some embodiments. In this embodiment, a control plane 400 is shown as a communications protocol stack between the UE 101 (or alternatively, the UE 102), the RAN node 111 (or alternatively, the RAN node 112), and the MME 121.

[0058] The PHY layer 401 may transmit or receive information used by the MAC layer 402 over one or more air interfaces. The PHY layer 401 may further perform link adaptation or adaptive modulation and coding (AMC), power control, cell search (e.g., for initial synchronization and handover purposes), and other measurements used by higher layers, such as the RRC layer 405. The PHY layer 401 may still further perform error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, modulation/demodulation of physical channels, interleaving, rate matching, mapping onto physical channels, and Multiple Input Multiple Output (MIMO) antenna processing.

[0059] The MAC layer 402 may perform mapping between logical channels and transport channels, multiplexing of MAC service data units (SDUs) from one or more logical channels onto transport blocks (TB) to be delivered to PHY via transport channels, de-multiplexing MAC SDUs to one or more logical channels from transport blocks (TB) delivered from the PHY via transport channels, multiplexing MAC SDUs onto TBs, scheduling information reporting, error correction through hybrid automatic repeat request (HARQ), and logical channel prioritization. [0060] The RLC layer 403 may operate in a plurality of modes of operation, including: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). The RLC layer 403 may execute transfer of upper layer protocol data units (PDUs), error correction through automatic repeat request (ARQ) for AM data transfers, and concatenation, segmentation and reassembly of RLC SDUs for UM and AM data transfers. The RLC layer 403 may also execute re-segmentation of RLC data PDUs for AM data transfers, reorder RLC data PDUs for UM and AM data transfers, detect duplicate data for UM and AM data transfers, discard RLC SDUs for UM and AM data transfers, detect protocol errors for AM data transfers, and perform RLC re-establishment.

[0061] The PDCP layer 404 may execute header compression and decompression of IP data, maintain PDCP Sequence Numbers (SNs), perform in-sequence delivery of upper layer PDUs at re-establishment of lower layers, eliminate duplicates of lower layer SDUs at re-establishment of lower layers for radio bearers mapped on RLC AM, cipher and decipher control plane data, perform integrity protection and integrity verification of control plane data, control timer-based discard of data, and perform security operations (e.g., ciphering, deciphering, integrity protection, integrity verification, etc.).

[0062] The main services and functions of the RRC layer 405 may include broadcast of system information (e.g., included in Master Information Blocks (MIBs) or System Information Blocks (SIBs) related to the non-access stratum (NAS)), broadcast of system information related to the access stratum (AS), paging, establishment, maintenance and release of an RRC connection between the UE and E-UTRAN (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), establishment, configuration, maintenance and release of point to point Radio Bearers, security functions including key management, inter radio access technology (RAT) mobility, and measurement configuration for UE

measurement reporting. The MIBs and SIBs may comprise one or more information elements (IEs), which may each comprise individual data fields or data structures. [0063] The UE 101 and the RAN node 111 may utilize a Uu interface

(e.g., an LTE-Uu interface) to exchange control plane data via a protocol stack comprising the PHY layer 401, the MAC layer 402, the RLC layer 403, the PDCP layer 404, and the RRC layer 405.

[0064] The non-access stratum (NAS) protocols 406 form the highest stratum of the control plane between the UE 101 and the MME 121. The NAS protocols 406 support the mobility of the UE 101 and the session management procedures to establish and maintain IP connectivity between the UE 101 and the P-GW 123.

[0065] The S 1 Application Protocol (S 1 -AP) layer 415 may support the functions of the SI interface and comprise Elementary Procedures (EPs). An EP is a unit of interaction between the RAN node 111 and the CN 120. The S 1-AP layer services may comprise two groups: UE-associated services and non UE- associated services. These services perform functions including, but not limited to: E-UTRAN Radio Access Bearer (E-RAB) management, UE capability indication, mobility, NAS signaling transport, RAN Information Management (RIM), and configuration transfer.

[0066] The Stream Control Transmission Protocol (SCTP) layer

(alternatively referred to as the SCTP/IP layer) 414 may ensure reliable delivery of signaling messages between the RAN node 111 and the MME 121 based, in part, on the IP protocol, supported by the IP layer 413. The L2 layer 412 and the LI layer 411 may refer to communication links (e.g., wired or wireless) used by the RAN node and the MME to exchange information.

[0067] The RAN node 111 and the MME 121 may utilize an S 1 -MME interface to exchange control plane data via a protocol stack comprising the LI layer 411, the L2 layer 412, the IP layer 413, the SCTP layer 414, and the Sl-AP layer 415.

[0068] FIG. 5 is an illustration of a user plane protocol stack in accordance with some embodiments. In this embodiment, a user plane 500 is shown as a communications protocol stack between the UE 101 (or alternatively, the UE 102), the RAN node 111 (or alternatively, the RAN node 112), the S-GW 122, and the P-GW 123. The user plane 500 may utilize at least some of the same protocol layers as the control plane 400. For example, the UE 101 and the RAN node 111 may utilize a Uu interface (e.g., an LTE-Uu interface) to exchange user plane data via a protocol stack comprising the PHY layer 401, the MAC layer 402, the RLC layer 403, the PDCP layer 404.

[0069] The General Packet Radio Service (GPRS) Tunneling Protocol for the user plane (GTP-U) layer 504 may be used for carrying user data within the GPRS core network and between the radio access network and the core network. The user data transported can be packets in any of IPv4, IPv6, or PPP formats, for example. The UDP and IP security (UDP/IP) layer 503 may provide checksums for data integrity, port numbers for addressing different functions at the source and destination, and encryption and authentication on the selected data flows. The RAN node 111 and the S-GW 122 may utilize an Sl-U interface to exchange user plane data via a protocol stack comprising the L 1 layer 411, the L2 layer 412, the UDP/IP layer 503, and the GTP-U layer 504. The S-GW 122 and the P-GW 123 may utilize an S5/S8a interface to exchange user plane data via a protocol stack comprising the LI layer 411, the L2 layer 412, the UDP/IP layer 503, and the GTP-U layer 504. As discussed above with respect to FIG. 4, NAS protocols support the mobility of the UE 101 and the session management procedures to establish and maintain IP connectivity between the UE 101 and the P-GW 123.

[0070] FIG. 6 is a block diagram illustrating components, according to some example embodiments, able to read instructions from a machine -readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and perform any one or more of the methodologies discussed herein. Specifically, FIG. 6 shows a diagrammatic representation of hardware resources 600 including one or more processors (or processor cores) 610, one or more memory/storage devices 620, and one or more communication resources 630, each of which may be communicatively coupled via a bus 640. For embodiments where node virtualization (e.g., NFV) is utilized, a hypervisor 602 may be executed to provide an execution environment for one or more network slices/sub-slices to utilize the hardware resources 600 [0071] The processors 610 (e.g., a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a complex instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP) such as a baseband processor, an application specific integrated circuit (ASIC), a radio-frequency integrated circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, a processor 612 and a processor 614.

[0072] The memory/storage devices 620 may include main memory, disk storage, or any suitable combination thereof. The memory /storage devices 620 may include, but are not limited to any type of volatile or non-volatile memory such as dynamic random access memory (DRAM), static random-access memory (SRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), Flash memory, solid-state storage, etc.

[0073] The communication resources 630 may include interconnection or network interface components or other suitable devices to communicate with one or more peripheral devices 604 or one or more databases 606 via a network 608. For example, the communication resources 630 may include wired communication components (e.g., for coupling via a Universal Serial Bus (USB)), cellular communication components, NFC components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components.

[0074] Instructions 650 may comprise software, a program, an application, an applet, an app, or other executable code for causing at least any of the processors 610 to perform any one or more of the methodologies discussed herein. The instructions 650 may reside, completely or partially, within at least one of the processors 610 (e.g., within the processor's cache memory), the memory /storage devices 620, or any suitable combination thereof. In some embodiments, the instructions 650 may reside on a tangible, non- volatile communication device readable medium, which may include a single medium or multiple media. Furthermore, any portion of the instructions 650 may be transferred to the hardware resources 600 from any combination of the peripheral devices 604 or the databases 606. Accordingly, the memory of processors 610, the memory/storage devices 620, the peripheral devices 604, and the databases 606 are examples of computer-readable and machine-readable media.

[0075] As above, some LTE systems may provide a dual-connectivity

(DC) framework permit a UE to simultaneously connect to a master gNB (MgNB) and a secondary gNB (SgNB) in the RRC_Connected state. This permits the use of radio resources provided by two distinct schedulers in a non- ideal backhaul environment in which a relatively large delay is present between the cells. In some embodiments, the MgNB may be a macro cell and the SgNB may be a small cell (e.g., micro or nano cell); in other embodiments, the MgNB and the SgNB may be micro cells. The MgNB may terminate at least the Sl- MME interface, and only one Sl-MME connection may be used for a UE. Control plane signaling between the MgNB and SgNB may be provided via the X2 interface. All SgNB -related RRC configuration information may thus be transmitted to the MgNB, which may then transmit the RRC message to the UE. The configurations (e.g. bandwidth, number of component carriers, frame structure of each carrier (FDD or TDD)), of the MgNB and SgNB may be independent. The use of multiple connections may increase UE throughput, especially for cell edge UEs, enhance the robustness of communications, and reduce signaling towards the core network (CN) due to frequent handover between SgNBs.

[0076] The MgNB and SgNB may be associated with a Master Cell

Group (MCG) and one or more Secondary Cell Groups (SCGs), respectively. The MCG may be a group of serving cells associated with the MgNB, and may comprise the primary cell (PCell) and one or more secondary cells (SCells). The SCG may be a group of serving cells associated with the SgNB, and may comprise the primary secondary cell (PSCell) and one or more Scells. At least one cell in SCG may have one or more uplink component carrier (CCs) used in carrier aggregation (CA), at least one of which may be configured with PUCCH resources. At least one SCG bearer or split bearer may be present when the SCG is configured; the MCG bearer provides data and control signaling and the SCG or split bearer provides only data signaling. One difference between the SCG and split bearer is that for split bearer the S 1-U interface terminates in the MgNB whereas for SCG bearer the S 1-U interface terminates at the SgNB. A DC UE may have two identities: one cell radio network temporary identity (C-RNTI) in the MCG and another C-RNTI in the SCG.

[0077] The MgNB may maintain thus context information and the RRM measurement configuration of the UE. For UE capability coordination, the MgNB may provide the AS-configuration and the UE capabilities to the SgNB. The MgNB may determine whether to route a DL packet via the MgNB or SgNB when split bearers are used, dependent on various measurement reports, traffic conditions, and cell load among others. The SgNB may decide which cell is the PSCell within the SCG. The MgNB may avoid changing the content of the RRC configuration provided by the SgNB. When adding a new SCG SCell, dedicated RRC signaling may be used for sending system information of the cell.

[0078] In standalone NR deployment, in which the 5G network and LTE networks are isolated, the UE may simultaneously connect to multiple 5G NR small cells. The coverage areas of the small cells may be independent. Thus, in some embodiments, the coverage areas of the small cells may be similar (e.g., both micro cells); in other embodiments, the coverage area of at least one of the small cells may be different from the coverage area of at least another of the small cells.

[0079] From time to time, especially in high mobility situations, the

MgNB may handover from a source MgNB to a target gNB. The target gNB may be a macro or micro cell. The handover may entail switching not only the MgNB but the connection between the MgNB and SgNB. In some cases, a

MgNB-SgNB switching procedure may switch the MgNB and SgNB between a source gNB and target gNB during handover, and reduce or eliminate the interruption time associated with the handover. This may be accomplished by at least one of postponing SCG release to after the handover and/or avoiding the random access procedure associated with handover, among other messaging.

[0080] FIG. 7 illustrates an gNB to gNB change procedure in accordance with some embodiments. In particular, FIG. 7 shows an LTE MgNB to gNB change procedure 700. One or more of the components shown in FIG. 7, the UE 710, source MgNB (S-MgNB) 720, source SgNB (S-SgNB) 730, target gNB (T- gNB) 740, S-GW 750, and MME 760 may be shown in FIGS. 1-6.

[0081] As shown in FIG. 7, at operation 1, the S-MgNB 720 may initiate the MgNB-to-gNB change procedure by initiating an X2 handover preparation procedure. The handover may be triggered at operation 0 by measurement reports (e.g., RSRP or RSRQ data of the S-MgNB and/or neighboring cells). The X2 handover preparation procedure may start with the S-MgNB 720 transmitting a handover request to the T-gNB 740. The handover request may include a HandoverPreparationlnformation IE. The source MgNB may include the SCG configuration in the HandoverPreparationlnformation IE.

[0082] At operation 2, the T-gNB 740 may transmit a handover request acknowledgment to the S-MgNB 720. The handover request acknowledgment may be an ACK/NACK to indicate whether the handover request was successfully received by the T-gNB 740. The T-gNB 740 may include the HandoverPreparationlnformation field in the handover command that releases the SCG configuration. The handover command may also provide forwarding addresses to the S-MgNB 720. The addition of an SgNB can be initiated only after completing handover.

[0083] After reception of a handover request acknowledgment indicating successful allocation of target gNB resources, the S-MgNB 720 may initiate the release of the S-SgNB resources towards the S-SgNB 730. The release may be indicated by transmission of an SgNB Release Request from the S-MgNB 720 to the S-SgNB 730 at operation 3. The S-MgNB 720 may provide data forwarding addresses to the S-SgNB 730 for data forwarding purposes, for example. Either direct data forwarding or indirect data forwarding may be used for the SCG bearer; only indirect data forwarding may be used for the split bearer. Reception of the SgNB Release Request message may trigger the S-SgNB 730 to stop providing user data to the UE and, if applicable, to start data forwarding.

[0084] In addition to transmission of the SgNB Release Request message, the S-MgNB 720 may trigger the UE to apply the new SCG configuration. In particular, the S-MgNB 720 may transmit the new SCG configuration in an RRCConnectionReconfiguration message at operation 4. At this point, no data transmissions may occur until after operation 6.

[0085] The UE 710, upon receiving the new SCG configuration, may release the entire SCG configuration. The UE 710 may then synchronize to the T-gNB 740 through a RACH procedure at operation 5.

[0086] Once the RACH procedure is completed, the UE 710 may communicate completion of the process through an

RRCConnectionReconfigurationComplete message at operation 6. The RRCConnectionReconfigurationComplete message may be transmitted from the UE 710 to the T-gNB 740 rather than to the S-MgNB 720.

[0087] At operations 7 and 8, data forwarding may occur from the S-

SgNB 730. In particular, data from the S-SgNB 730 may be transmitted to the S-MgNB 720, and subsequently from the S-MgNB 720 to the T-gNB 740. Data forwarding may start as early as when the S-SgNB 730 receives the SgNB Release Request message from the S-MgNB 720.

[0088] At operations 9-13, the T-gNB 740 may initiate the SI Path

Switch procedure. The S I Path Switch procedure may include transmission of a Path Switch Request message from the T-gNB 740 to the MME 760 at operation 9. The MME 760 may subsequently modify the bearer in communication with the S-GW 750. The S-GW 750 may send one or more end marker packets to the S-SgNB 730 before releasing the user plane resources of the UE 710 that are associated with the S-SgNB 730. The S-SgNB 730 may supply the end marker to the T-gNB 740 through the S-MgNB 720. The MME 760 may subsequently confirm the update to the T-gNB 740 in a response to the Path Switch Request.

[0089] At operation 14, the T-gNB 740 may initiate the UE Context

Release procedure towards the S-MgNB 720. The T-gNB 740 may thus transmit a UE Context Release message to the S-MgNB 720.

[0090] At operation 15, the S-MgNB 720 may relay the UE Context

Release message to the S-SgNB 730. Upon reception of the UE Context Release message, from the S-MgNB 720, the S-SgNB 730 can release radio- and control- plane related resources associated with the UE context. Ongoing data forwarding may continue. [0091] FIG. 8 illustrates a 5G NR gNB to gNB change procedure in accordance with some embodiments. In particular, FIG. 8 shows a 5G NR MgNB to gNB change procedure 800. One or more of the components shown in FIG. 8, the UE 810, S-MgNB 820, S-SgNB/T-gNB 830, S-GW 850, and MME 860 may be shown in FIGS. 1-6. As in FIG. 7, the various messages in FIG. 8 that are transmitted between entities may be encoded for transmission by the transmitting entity and decoded by the receiving entity before being further processed by the receiving entity. In some embodiments, as above, the S-MgNB 820 and S-SgNB/T-gNB 830 may both be small cells. In other embodiments, the S-MgNB 820 macro cell that wishes to no longer retain the UE context information (e.g., because of the load on the S-MgNB 820) and S-SgNB/T-gNB 830 may be a small cell.

[0092] One difference between the LTE procedure shown in FIG. 7 and the 5G NR procedure shown in FIG. 8 is that the T-gNB and S-SgNB may be the same node in 5G NR DC/MC-based mobility /handover. As a result, the procedure of FIG. 7 can be simplified. In particular, message exchange between the S-SgNB and T-gNB may be avoided. If the UE 810 is already (UL) connected to the S-SgNB/T-gNB 830, the RACH procedure may also be skipped.

[0093] Moreover, in some embodiments, the S-MgNB 820 and S-

SgNB/T-gNB 830 may negotiate or otherwise indicate to each other the timing of release of the S-SgNB resource. The timing may indicate, for example, whether to release the S-SgNB resource immediately or postpone the release until after handover. Alternatively, or in addition, the S-MgNB 820 and S- SgNB/T-gNB 830 may negotiate or otherwise indicate to each other whether to switch the MgNB/SgNB roles. After a role switch, the original S-MgNB 820 may become the new SgNB and the original S-SgNB 830 may become the new MgNB.

[0094] As shown in FIG. 8, at operation 1, the S-MgNB 820 may initiate the MgNB-to-gNB change procedure by initiating an X2 handover preparation procedure. The X2 handover preparation procedure may start with the S-MgNB 820 transmitting a handover request to the S-SgNB/T-gNB 830. The handover request may include a HandoverPreparationlnformation IE. The S-MgNB 820 may include the SCG configuration in the HandoverPreparationlnformation IE. Accordingly, the T-gNB knows from the SCG configuration that the T-gNB is also the S-SgNB.

[0095] The S-MgNB 820 may include a "Postponing S-SgNB Release

Indicator" field in the Handover Request message. The Postponing S-SgNB Release Indicator field may request postponing of release of the S-SgNB resource until after handover. In some embodiments, the Postponing S-SgNB Release Indicator field may be a single bit, indicating either to release the S- SgNB resource immediately or to postpone the release until after handover, the latter of which may indicate a "make before break" handover. In other embodiments, the Postponing S-SgNB Release Indicator field may comprise multiple bits that indicate the release timing, either in terms of when a particular message is transmitted or received (such as the RRCConfigurationComplete message), or a timer - in terms of ms (or another time measurement) after reception of the handover request.

[0096] In addition, the S-MgNB 820 may include another new field, the

"MgNB/SgNB Switching Indicator" field, in the

HandoverPreparationlnformation IE of the handover request. The MgNB/SgNB Switching Indicator field may request adding the S-MgNB 820 as the SgNB after handover is successfully completed.

[0097] At operation 2, the S-SgNB/T-gNB 830 may transmit a Handover

Request ACK to the S-MgNB 820. The Handover Request ACK may comprise an ACK NACK indication that indicates whether the handover request was successfully received by the S-SgNB/T-gNB 830. The S-SgNB/T-gNB 830 may include the HandoverPreparationlnformation field in the handover command.

[0098] The S-SgNB/T-gNB 830 may include a "Postponing Successful" field in the Handover Request ACK message. The Postponing Successful field may be a single bit that indicates whether the release of the S-SgNB resource was successfully postponed. If the Postponing Successful field indicates that postponement of the S-SgNB resource was successful, the S-MgNB 820 can continue deliver data to the UE 810 via the S-SgNB/T-gNB 830 until the time indicates by the Postponing Successful field. This is to say that the S-SgNB/T- gNB 830 may retain the S-SgNB resource until handover completion and the S- MgNB 820 may continue to send data and/or RRC messages to the UE 810 via the S-SgNB/T-gNB 830 during handover. In some embodiments, the

Postponing Successful field may be a multibit field that indicates postponement similar to the times indicated by the multibit Postponing S-SgNB Release Indicator.

[0099] In addition, the Handover Request ACK message may include the

MgNB/SgNB Switching Indicator field if the MgNB/SgNB Switching Indicator field is included in the Handover Request message. The inclusion of the MgNB/SgNB Switching Indicator field (or the MgNB/SgNB Switching

Indicator field being set to a predetermined value) in the Handover Request ACK message may initiate activation of activate MgNB/SgNB switching.

[00100] Different from FIG. 7, in FIG. 8 transmission of the SgNB Release Request between the SgNB and T-gNB may be skipped. In other words, as the SgNB and T-gNB are the same entity, the SgNB Release Request may not be transmitted. As above, the SgNB Release Request, like other information exchanged between MgNB and SgNB, may use an RRC container via the X2 interface.

[00101] The S-MgNB 820 may trigger the UE 810 to apply the new SCG configuration at operation 4. In particular, the S-MgNB 820 may transmit the new SCG configuration to the UE 810 in an RRCConnectionReconfiguration message. If MgNB/SgNB switching is activated, as indicated by the

MgNB/SgNB Switching Indicator field in the Handover Request ACK message, the RRCConnectionReconfiguration message may include the MgNB/SgNB Switching Indicator field (or the MgNB/SgNB Switching Indicator field may be set to a predetermined value). In some embodiments, the

RRCConnectionReconfiguration message may in addition or instead include the Postponing S-SgNB Release Indicator field or the Postponing Successful field. This may cause the UE to reconfigure itself accordingly for communication with the gNBs. Similarly, the S-MgNB 820 may reconfigure itself to operate as the SgNB. If MgNB/SgNB switching is not activated, the UE 810 may release the entire SCG configuration.

[00102] As noted above, because the SgNB and T-gNB are the same entity, other messaging in addition to the SgNB Release Request may be skipped as well. For example, as the UE 810 is already synchronized to the S-SgNB/T- gNB 830, the entire RACH procedure, whether contention-based or contention- free, may be skipped and the UE 810 continue to communicate with the S- SgNB/T-gNB 830 without engaging in the RACH procedure during handover. The RACH procedure that is skipped may, for example, include transmission of a RACH preamble sequence by the UE 810, reception by the UE 810 of a

Random Access Response that include timing advance, UL grant and Temporary C-RNTI, a RRC connection request message transmitted by the UE 810, and a contention resolution message (for a contention-based RACH procedure).

[00103] After applying the new SCG configuration, the UE 810 may confirm successful handover with the target gNB (SgNB/T-gNB 830). If

MgNB/SgNB switching is activated, the UE 810 may include the MgNB/SgNB Switching Indicator field in the RRCConnectionReconfigurationCompletion message at operation 6. The inclusion of the MgNB/SgNB Switching Indicator field (or the use of a particular value) may indicate whether the UE 810 has successfully reconfigured itself for MgNB/SgNB switching. If successful, the S- SgNB/T-gNB 830 may reconfigure itself to operate as the new MgNB. In addition, the S-SgNB/T-gNB 830 may (if it has not yet) release the S-SgNB resource.

[00104] In addition, if applicable, data forwarding from the S-MgNB 820 to the S-SgNB/T-gNB 830 may occur at operation 8. The data forwarding may be initiated, for example, immediately after operation 4. The S-SgNB/T-gNB 830 may release (if it has not yet) the S-SgNB resource after receiving the SN Status Transfer message at operation 7. Note that operations 7 and 8 (data forwarding) may occur before operation 6, but will occur after operation 4.

[00105] At operations 9-13, the S-SgNB/T-gNB 830 may initiate the S 1

Path Switch procedure. The S I Path Switch procedure may include transmission of a Path Switch Request message from the S-SgNB/T-gNB 830 to the MME 860 at operation 9. The MME 860 may subsequently modify the bearer in communication with the S-GW 850. The S-GW 850 may send one or more end marker packets to the S-MgNB 820 before releasing the user plane resources of the UE 810 that are associated with the S-SgNB 830. The S-MgNB 820 may supply the end marker to the S-SgNB/T-gNB 830. The MME 860 may subsequently confirm the update to the S-SgNB/T-gNB 830 in a Path Switch Request ACK response to the Path Switch Request.

[00106] At operation 14, the S-SgNB/T-gNB 830 may initiate the UE

Context Release procedure towards the S-MgNB 820. The S-SgNB/T-gNB 830 may thus transmit a UE Context Release message to the S-MgNB 820.

However, if MgNB/SgNB switching is successful, operation 14 may be skipped; the S-MgNB 820 may begin communication with the UE 810 as the new SgNB without receiving the UE Context Release. Even if operation 14 is not skipped, however, transmission of the UE Context Release message from the S-MgNB 820 (to the S-SgNB) may be avoided as the S-SgNB and T-gNB are the same entity.

[00107] Note that although gNBs are referred to above, the above can be applied to eNBs as well. [00108] Examples

[00109] Example 1 is an apparatus of a source master evolved NodeB (S- MgNB), the apparatus comprising: a memory; and processing circuitry arranged to: encode downlink data stored in the memory for delivery directly to a user equipment (UE) configured for dual connectivity with the S-MgNB and a source secondary gNB (S-SgNB); determine that handover to a target gNB (T-gNB) is to occur based on a measurement report from the UE; determine that the T-gNB is the S-SgNB; and initiate handover via a Handover Request message to the T- gNB, the Handover Request message comprising a Secondary Cell Group (SCG) configuration in a HandoverPreparationlnformation information element (IE), the SCG configuration indicating to the T-gNB that the T-gNB is the S-SgNB; and in response to a determination that the T-gNB is the S-SgNB, during the handover refrain from transmitting a SgNB Release Request from the S-MgNB to the T-gNB.

[00110] In Example 2, the subject matter of Example 1 includes, wherein: the Handover Request message comprises a Postponing S-SgNB Release Indicator field that indicates timing of release by the T-gNB of a S-SgNB resource for the UE.

[00111] In Example 3, the subject matter of Example 2 includes, wherein: the Postponing S-SgNB Release Indicator field requests postponement of release of the S-SgNB resource until after handover completion.

[00112] In Example 4, the subject matter of Example 3 includes, wherein: the Postponing S-SgNB Release Indicator field is a single bit.

[00113] In Example 5, the subject matter of Examples 2-4 includes, wherein the processing circuitry is further arranged to: decode a Handover Request Acknowledgement (ACK) message from the T-gNB, the Handover Request ACK message comprising a Postponing Successful field that indicates whether release of the S-SgNB resource was successfully postponed.

[00114] In Example 6, the subject matter of Example 5 includes, wherein the processing circuitry is further arranged to: continue to deliver data to the UE via the S-SgNB in response to the Postponing Successful field indicating that release of the S-SgNB resource was successfully postponed.

[00115] In Example 7, the subject matter of Examples 1-6 includes, wherein: the Handover Request message comprises a MgNB/SgNB Switching Indicator field that requests that the T-gNB add the S-MgNB as a new S-SgNB after handover completion.

[00116] In Example 8, the subject matter of Example 7 includes, wherein the processing circuitry is further arranged to: decode a Handover Request Acknowledgement (ACK) message from the T-gNB, the Handover Request ACK message comprising the MgNB/SgNB Switching Indicator field to indicate MgNB/SgNB switching is activated; reconfigure the S-MgNB to operate as the new S-SgNB; and transmit an RRCConnectionReconfiguration message to the UE, the RRCConnectionReconfiguration message comprising the MgNB/SgNB Switching Indicator field to cause the UE to reconfigure to the S-MgNB as the new S-SgNB after handover completion.

[00117] In Example 9, the subject matter of Example 8 includes, wherein the processing circuitry is further arranged to: in response to a determination that MgNB/SgNB switching is activated, begin communication with the UE as the new SgNB free from reception of a UE Context Release message from the T- gNB.

[00118] In Example 10, the subject matter of Examples 1-9 includes, wherein the processing circuitry is further arranged to: complete the handover free from transmission of a UE Context Release message to the T-gNB.

[00119] In Example 11, the subject matter of Examples 1-10 includes, wherein: the processing circuitry comprises a baseband processor configured to encode transmissions to, and decode transmissions from, the UE and the T-gNB.

[00120] Example 12 is an apparatus of a user equipment (UE), the apparatus comprising: a memory; and processing circuitry arranged to: decode downlink data from a source master evolved NodeB (S-MgNB) and a source secondary gNB (S-SgNB), the data stored in the memory; decode an

RRCConnectionReconfiguration message that indicates handover between the S- SgNB and target gNB (T-gNB) and that the S-SgNB is the T-gNB; and after reception of the RRCConnectionReconfiguration message, reconfigure the UE for communication with the T-gNB as a new MgNB and avoid engagement in a random access channel procedure (RACH) during the handover to communicate with the T-gNB.

[00121] In Example 13, the subject matter of Example 12 includes, wherein: the RRCConnectionReconfiguration message comprises a

MgNB/SgNB Switching Indicator field to indicate that the T-gNB is the new MgNB and the S-MgNB is a new SgNB after handover completion.

[00122] In Example 14, the subject matter of Example 13 includes, wherein the processing circuitry is further arranged to: in response to reception of the RRCConnectionReconfiguration message, encode, for transmission to the T-gNB, an RRCConnectionReconfigurationCompetion message that comprises the MgNB/SgNB Switching Indicator field to indicate that reconfiguration of the UE is successful.

[00123] In Example 15, the subject matter of Examples 12-14 includes, wherein the processing circuitry is further arranged to: continue to communicate with the S-MgNB via the S-SgNB during handover as before handover as release of a S-SgNB resource for the UE is postponed until after handover completion.

[00124] Example 16 is (New) A computer-readable storage medium that stores instructions for execution by one or more processors of a fifth generation (5G) new radio (NR) source secondary gNB (S-gNBSgNB), the one or more processors to configure the S-SgNB to, when the instructions are executed: transmit downlink data for delivery to a 5G NR user equipment (UE) and, when a split bearer configuration is used, select other downlink data from a 5G NR source master gNodeB (S-MgNB) for delivery to the UE; determine that handover is to occur between the S-MgNB and a 5G NR target gNB (T-gNB); determine that the S-SgNB and the T-gNB are the same gNB; in response to a determination that the S-SgNB and the T-gNB are the same gNB, complete handover free from reception from the S-MgNB of a SgNB Release Request after reception of a Handover Request Acknowledgment (ACK) message and free from transmission of a UE Context Release message to the S-MgNB after reception of a Path Switch Request ACK from a Mobility Management Entity (MME).

[00125] In Example 17, the subject matter of Example 16 includes, wherein: the instructions further configure the one or more processors to configure the S-SgNB to receive a Handover Request message from the S- MgNB, the Handover Request message comprising a Secondary Cell Group

(SCG) configuration in a HandoverPreparationlnformation information element (IE), the SCG configuration indicating that the S-SgNB is the T-gNB, and the Handover Request message comprises at least one of: a Postponing S-SgNB Release Indicator field that indicates timing of release by the S-SgNB of a S- SgNB resource for the UE, or a MgNB/SgNB Switching Indicator field that requests that the S-SgNB add the S-MgNB as a new SgNB after handover completion. [00126] In Example 18, the subject matter of Example 17 includes, wherein: the Postponing S-SgNB Release Indicator field requests postponement of release of the S-SgNB resource until after handover completion.

[00127] In Example 19, the subject matter of Examples 17-18 includes, wherein: the Handover Request ACK message comprises a Postponing

Successful field that indicates whether release of the S-SgNB resource was successfully postponed.

[00128] In Example 20, the subject matter of Examples 16-19 includes, wherein: a Handover Request message received from the S-MgNB comprises the MgNB/SgNB Switching Indicator field.

[00129] In Example 21, the subject matter of Example 20 includes, wherein the instructions further configure the one or more processors to configure the S-SgNB to: skip transmission to the S-MgNB of a UE Context Release message in response to the Handover Request comprising the

MgNB/SgNB Switching Indicator field.

[00130] In Example 22, the subject matter of Examples 16-21 includes, wherein the instructions further configure the one or more processors to configure the S-SgNB to: complete the handover free from reception of a UE Context Release message from the S-MgNB.

[00131] Example 23 is (New) A method of a simplifying handover in fifth generation (5G) new radio (NR) source secondary gNB (S-SgNB), the method comprising: transmitting downlink data for delivery to a 5G NR user equipment (UE) and, when a split bearer configuration is used, select other downlink data from a 5G NR source master gNodeB (S-MgNB) for delivery to the UE;

determining that handover is to occur between the S-MgNB and a 5G NR target gNB (T-gNB); determining that the S-SgNB and the T-gNB are the same gNB; in response to a determination that the S-SgNB and the T-gNB are the same gNB, completing handover free from reception from the S-MgNB of a SgNB Release Request after reception of a Handover Request Acknowledgment (ACK) message and free from transmission of a UE Context Release message to the S- MgNB after reception of a Path Switch Request ACK from a Mobility

Management Entity (MME). [00132] In Example 24, the subject matter of Example 23 includes, wherein: the method further comprises receiving a Handover Request message from the S-MgNB, the Handover Request message comprising a Secondary Cell Group (SCG) configuration in a HandoverPreparationlnformation information element (IE), the SCG configuration indicating that the S-SgNB is the T-gNB, and the Handover Request message comprises at least one of: a Postponing S- SgNB Release Indicator field that indicates timing of release by the S-SgNB of a S-SgNB resource for the UE, or a MgNB/SgNB Switching Indicator field that requests that the S-SgNB add the S-MgNB as a new SgNB after handover completion.

[00133] In Example 25, the subject matter of Examples 23-24 includes, wherein: the Postponing S-SgNB Release Indicator field requests postponement of release of the S-SgNB resource until after handover completion.

[00134] In Example 26, the subject matter of Examples 23-25 includes, wherein: the Handover Request ACK message comprises a Postponing

Successful field that indicates whether release of the S-SgNB resource was successfully postponed.

[00135] In Example 27, the subject matter of Examples 23-26 includes, wherein: a Handover Request message received from the S-MgNB comprises the MgNB/SgNB Switching Indicator field.

[00136] In Example 28, the subject matter of Example 27 includes, skipping transmission to the S-MgNB of a UE Context Release message in response to the Handover Request comprising the MgNB/SgNB Switching Indicator field.

[00137] In Example 29, the subject matter of Examples 23-28 includes, completing the handover free from reception of a UE Context Release message from the S-MgNB.

[00138] Example 30 is (New) An apparatus of a fifth generation (5G) new radio (NR) source secondary gNB (S-SgNB), the apparatus comprising: means for transmitting downlink data for delivery to a 5G NR user equipment (UE) and, when a split bearer configuration is used, select other downlink data from a 5G NR source master gNodeB (S-MgNB) for delivery to the UE; means for determining that handover is to occur between the S-MgNB and a 5G NR target gNB (T-gNB); means for determining that the S-SgNB and the T-gNB are the same gNB; in response to a determination that the S-SgNB and the T-gNB are the same gNB, means for completing handover free from reception from the S- MgNB of a SgNB Release Request after reception of a Handover Request

Acknowledgment (ACK) message and free from transmission of a UE Context Release message to the S-MgNB after reception of a Path Switch Request ACK from a Mobility Management Entity (MME).

[00139] In Example 31, the subject matter of Example 30 includes, wherein: the apparatus further comprises means for receiving a Handover

Request message from the S-MgNB, the Handover Request message comprising a Secondary Cell Group (SCG) configuration in a

HandoverPreparationlnformation information element (IE), the SCG

configuration indicating that the S-SgNB is the T-gNB, and the Handover Request message comprises at least one of: a Postponing S-SgNB Release Indicator field that indicates timing of release by the S-SgNB of a S-SgNB resource for the UE, or a MgNB/SgNB Switching Indicator field that requests that the S-SgNB add the S-MgNB as a new SgNB after handover completion.

[00140] In Example 32, the subject matter of Examples 30-31 includes, wherein: the Postponing S-SgNB Release Indicator field requests postponement of release of the S-SgNB resource until after handover completion.

[00141] In Example 33, the subject matter of Examples 30-32 includes, wherein: the Handover Request ACK message comprises a Postponing

Successful field that indicates whether release of the S-SgNB resource was successfully postponed.

[00142] In Example 34, the subject matter of Examples 30-33 includes, wherein: a Handover Request message received from the S-MgNB comprises the MgNB/SgNB Switching Indicator field.

[00143] In Example 35, the subject matter of Example 34 includes, means for skipping transmission to the S-MgNB of a UE Context Release message in response to the Handover Request comprising the MgNB/SgNB Switching Indicator field. [00144] In Example 36, the subject matter of Examples 30-35 includes, means for completing the handover free from reception of a UE Context Release message from the S-MgNB.

[00145] Example 37 is at least one machine-readable medium including instructions that, when executed by processing circuitry, cause the processing circuitry to perform operations to implement of any of Examples 1-36.

[00146] Example 38 is an apparatus comprising means to implement of any of Examples 1-36.

[00147] Example 39 is a system to implement of any of Examples 1-36.

[00148] Example 40 is a method to implement of any of Examples 1-36.

[00149] Although an embodiment has been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader scope of the present disclosure. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. The

accompanying drawings that form a part hereof show, by way of illustration, and not of limitation, specific embodiments in which the subject matter may be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.

[00150] The subject matter may be referred to herein, individually and/or collectively, by the term "embodiment" merely for convenience and without intending to voluntarily limit the scope of this application to any single inventive concept if more than one is in fact disclosed. Thus, although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.

[00151] In this document, the terms "a" or "an" are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of "at least one" or "one or more." In this document, the term "or" is used to refer to a nonexclusive or, such that "A or B" includes "A but not B," "B but not A," and "A and B," unless otherwise indicated. In this document, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein." Also, in the following claims, the terms "including" and "comprising" are open-ended, that is, a system, UE, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

[00152] The Abstract of the Disclosure is provided to comply with 37

C.F.R. § 1.72(b), requiring an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.