WO2024073992A1

WO2024073992A1 - User equipment handover in a wireless network using a medium access control control element

Info

Publication number: WO2024073992A1
Application number: PCT/CN2023/074162
Authority: WO
Inventors: Chenxi Zhu; Bingchao LIU; Lianhai WU; Yi Zhang; Wei Ling; Lingling Xiao
Original assignee: Lenovo (Beijing) Ltd.
Priority date: 2023-02-01
Filing date: 2023-02-01
Publication date: 2024-04-11
Also published as: WO2024073992A9

Abstract

Various aspects of the present disclosure relate to user equipment handover in a wireless network using a medium access control control element. A network entity, such as a gNB, generates a MAC-CE that includes a handover command to handover a user equipment (UE) from a serving cell to a target cell with a different physical cell identifier. The handover command includes a trigger indicating to the UE to perform one or both of an aperiodic channel state information (CSI) process in the target cell or track a tracking reference signal (TRS) in the target cell. The network entity transmits the MAC-CE to the UE, which performs, in response to the trigger included in the handover command, the aperiodic CSI process in the target cell or tracks, in response to the trigger included in the handover command, a TRS in the target cell.

Description

USER EQUIPMENT HANDOVER IN A WIRELESS NETWORK USING A MEDIUM ACCESS CONTROL CONTROL ELEMENT

TECHNICAL FIELD

The present disclosure relates to wireless communications, and more specifically to a handover mechanism in a wireless network based on a medium access control control element (MAC-CE) .

BACKGROUND

A wireless communications system may include one or multiple network communication devices, such as base stations, which may be otherwise known as an eNodeB (eNB) , a next-generation NodeB (gNB) , or other suitable terminology. Each network communication devices, such as a base station may support wireless communications for one or multiple user communication devices, which may be otherwise known as user equipment (UE) , or other suitable terminology. The wireless communications system may support wireless communications with one or multiple user communication devices by utilizing resources of the wireless communication system (e.g., time resources (e.g., symbols, slots, subframes, frames, or the like) or frequency resources (e.g., subcarriers, carriers) . Additionally, the wireless communications system may support wireless communications across various radio access technologies including third generation (3G) radio access technology, fourth generation (4G) radio access technology, fifth generation (5G) radio access technology, among other suitable radio access technologies beyond 5G (e.g., sixth generation (6G) ) .

The base stations of the wireless communications system create a network of cells with each base station corresponding to a cell. Many UEs are mobile devices, such as mobile phones, so their locations can change. When the location of a UE changes the UE may change from being managed or served by a different cell, and a handover process is performed to hand over the UE from a current serving cell to a target cell.

SUMMARY

The present disclosure relates to methods, apparatuses, and systems that support user equipment handover in a wireless network using a MAC-CE. A network entity, such as a gNB, generates a MAC-CE that includes a handover command to handover a UE from a serving cell to a target cell with a different physical cell identifier (PCI) . The handover command includes a trigger indicating to the UE to perform one or both of an aperiodic channel state information (CSI) process in the target cell or track a tracking reference signal (TRS) in the target cell. The network entity transmits the MAC-CE to the UE, which performs, in response to the trigger included in the handover command, the aperiodic CSI process in the target cell or tracks, in response to the trigger included in the handover command, a TRS in the target cell. By transmitting the handover command including the trigger to perform the aperiodic CSI process in the target cell or track a TRS in the target cell, the UE is able to quickly begin performing the aperiodic CSI process or tracking of the TRS in the target cell after the handover of the UE to the target cell is completed.

Some implementations of the method and apparatuses described herein may further include to: generate a MAC-CE that includes a handover command to hand over a UE from a serving cell to a target cell with a different PCI, wherein the handover command includes a trigger indicating to the UE to perform one or both of an aperiodic CSI process in the target cell or track a TRS in the target cell; transmit, to the UE, the MAC-CE.

In some implementations of the method and apparatuses described herein, the method and apparatuses further include to transmit, to the UE, radio resource control (RRC) signaling indicating CSI reference signal resources for channel measurement with PCIs different from the PCI of the serving cell. Additionally or alternatively, the method and apparatuses described herein, the method and apparatuses further include to transmit, to the UE, RRC signaling indicating aperiodic CSI trigger state in cells with PCIs different from the PCI of the serving cell. Additionally or alternatively, the method and apparatuses described herein, the method and apparatuses further include to transmit, to the UE, RRC signaling indicating CSI-reference signal (RS) resources for TRS in cells with PCIs different from the PCI of the serving cell. Additionally or alternatively, wherein the handover command including a trigger indicating to perform an aperiodic CSI process in the target cell indicates a CSI-AperiodicTriggerState explicitly. Additionally or alternatively, the handover command including a trigger indicating to perform an aperiodic CSI process in the target cell indicates an only CSI-AperiodicTriggerState in the target cell implicitly. Additionally or alternatively, the MAC-CE including the handover command also includes a scheduling information of a physical uplink shared channel in the target cell for the UE to send aperiodic CSI feedback. Additionally or alternatively, the scheduling information in the MAC-CE follows a random-access response uplink grant in a random-access procedure. Additionally or alternatively, the handover command including a trigger indicating to track the TRS in the target cell indicates a TRS resource explicitly. Additionally or alternatively, the handover command including a trigger indicating to track the TRS in the target cell indicates an only TRS resource configured in the target cell implicitly. Additionally or alternatively, the MAC-CE including the handover command also includes scheduling information of a physical uplink shared channel in the target cell for CSI feedback, the scheduling information including at least a time and a frequency resource. Additionally or alternatively, the method and apparatuses described herein, the method and apparatuses further include to coordinate with the target cell through centralized units and distributed units of the apparatus and a network entity in the target cell.

Some implementations of the method and apparatuses described herein may further include to: receive, from a first network entity, a MAC-CE that includes a handover command for handover of a UE from a serving cell to a target cell with a different PCI; perform, in response to the handover command, an aperiodic CSI process in the target cell or track, in response to the handover command, a TRS in the target cell.

In some implementations of the method and apparatuses described herein, the apparatus is configured with CSI reference signal resources for channel measurement with PCIs different from the PCI of the serving cell. Additionally or alternatively, the apparatus is configured with aperiodic CSI trigger states in cells with PCIs different from the PCI of the serving cell. Additionally or alternatively, the apparatus is configured with TRS in cells with PCIs different from the PCI of the serving cell. Additionally or alternatively, the method and apparatuses further include to measure a channel from an aperiodic CSI reference signal resource in the target cell following a CSI-AperiodicTriggerState signaled by the handover command explicitly. Additionally or alternatively, the method and apparatuses further include to measure a channel from an aperiodic CSI reference signal resource in the target cell following an only CSI-AperiodicTriggerState configured in the target cell. Additionally or alternatively, the method and apparatuses further include to track the TRS in the target cell on a CSI reference signal resource for tracking signaled by the MAC-CE that includes the handover command explicitly after handover to the target cell. Additionally or alternatively, the method and apparatuses further include to track the TRS in the target cell on an only CSI reference signal resource for tracking configured in the target cell after handover to the target cell. Additionally or alternatively, the method and apparatuses further include to: measure a channel from an aperiodic CSI reference signal resource; and transmit, to a second network entity in the target cell, CSI feedback following an only CSI-AperiodicTriggerState configured in the target cell. Additionally or alternatively, wherein T_g is a gap to allow the apparatus to switch to a new transmission configuration indicator (TCI) state in the target cell, k is a fixed value, μ is a subcarrier spacing of a carrier wherein the apparatus transmitted to the first network entity an acknowledgment of the handover command, is a time of k subframes in μ, and the apparatus is handed over to the target cell afterAdditionally or alternatively, the apparatus comprises a UE and the first network entity comprises a base station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communications system that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure.

FIG. 2 illustrates an example information element that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example handover timeline that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure.

FIG. 4 illustrates an example message that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure.

FIGs. 5 and 6 illustrate examples of block diagrams of devices that support user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure.

FIGs. 7 through 12 illustrate flowcharts of methods that support user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

When the location of a UE changes the cell serving or managing the UE may change, and a handover process is performed to hand over the UE from a current serving cell to a target cell. A handover interruption time for layer 1 (L1) or layer 2 (L2) based inter-cell mobility is, for example, the time from the UE receiving the cell switch command (e.g., a handover command) to the UE performing the first downlink (DL) reception or uplink (UL) transmission on the indicated beam of the target cell. Longer handover interruption times result in poorer performance of the UE due to the delay in performing the first DL reception or UL transmission after receiving the cell switch command.

Using the techniques discussed herein, a network entity, such as a gNB, generates a MAC-CE that includes a handover command to hand over a UE from a serving cell to a target cell with a different PCI. The handover command includes a trigger indicating to the UE to perform one or both of an aperiodic CSI process in the target cell or track a TRS in the target cell. The network entity transmits the MAC-CE to the UE, which performs, in response to the trigger included in the handover command and after a particular amount of time (referred to as the actual handover time) , the aperiodic CSI process in the target cell or tracks, in response to the trigger included in the handover command after the actual handover time, a TRS in the target cell. By transmitting the handover command including the trigger to perform the aperiodic CSI process in the target cell or track a TRS in the target cell, the UE is able to quickly begin performing the aperiodic CSI process or tracking of the TRS in the target cell after the handover of the UE to the target cell is completed. The UE need not wait until after the handover to the target cell has been completed to perform the aperiodic CSI process in the target cell or track a TRS in the target cell.

The techniques discussed herein allow the UE to quickly begin performing the aperiodic CSI process or tracking of the TRS in the target cell after the handover of the UE to the target cell is completed. By triggering the aperiodic CSI process in the handover MAC-CE before the actual handover time, the Aperiodic non-zero power (NZP) -CSI-RS resource can be transmitted to the UE earlier, and the physical uplink shared channel (PUSCH) carrying the CSI feedback can be transmitted from the UE to the network entity earlier. This reduces the CSI acquisition delay in the target cell and allows the transmission to resume as soon as possible in the target cell. By implicitly or explicitly triggering the TRS in the target cell in the handover command included in the MAC-CE, the UE can quickly establish tracking in the target cell.

Furthermore, the techniques discussed herein reduce the amount of signaling performed by the target cell by having the network entity in the serving cell transmit to the UE the MAC-CE that includes the trigger indicating to the UE to perform one or both of an aperiodic CSI process in the target cell or track a TRS in the target cell.

Aspects of the present disclosure are described in the context of a wireless communications system. Aspects of the present disclosure are further illustrated and described with reference to device diagrams and flowcharts.

FIG. 1 illustrates an example of a wireless communications system 100 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The wireless communications system 100 may include one or more network entities 102, one or more UEs 104, a core network 106, and a packet data network 108. The wireless communications system 100 may support various radio access technologies. In some implementations, the wireless communications system 100 may be a 4G network, such as an LTE network or an LTE-Advanced (LTE-A) network. In some other implementations, the wireless communications system 100 may be a 5G network, such as an NR network. In other implementations, the wireless communications system 100 may be a combination of a 4G network and a 5G network, or other suitable radio access technology including Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20. The wireless communications system 100 may support radio access technologies beyond 5G. Additionally, the wireless communications system 100 may support technologies, such as time division multiple access (TDMA) , frequency division multiple access (FDMA) , or code division multiple access (CDMA) , etc.

The one or more network entities 102 may be dispersed throughout a geographic region to form the wireless communications system 100. One or more of the network entities 102 described herein may be or include or may be referred to as a network node, a base station, a network element, a radio access network (RAN) , a base transceiver station, an access point, a NodeB, an eNodeB (eNB) , a next-generation NodeB (gNB) , or other suitable terminology. A network entity 102 and a UE 104 may communicate via a communication link 110, which may be a wireless or wired connection. For example, a network entity 102 and a UE 104 may perform wireless communication (e.g., receive signaling, transmit signaling) over a Uu interface.

A network entity 102 may provide a geographic coverage area 112 for which the network entity 102 may support services (e.g., voice, video, packet data, messaging, broadcast, etc. ) for one or more UEs 104 within the geographic coverage area 112. For example, a network entity 102 and a UE 104 may support wireless communication of signals related to services (e.g., voice, video, packet data, messaging, broadcast, etc. ) according to one or multiple radio access technologies. In some implementations, a network entity 102 may be moveable, for example, a satellite associated with a non-terrestrial network. In some implementations, different geographic coverage areas 112 associated with the same or different radio access technologies may overlap, but the different geographic coverage areas 112 may be associated with different network entities 102. Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The one or more UEs 104 may be dispersed throughout a geographic region of the wireless communications system 100. A UE 104 may include or may be referred to as a mobile device, a wireless device, a remote device, a remote unit, a handheld device, or a subscriber device, or some other suitable terminology. In some implementations, the UE 104 may be referred to as a unit, a station, a terminal, or a client, among other examples. Additionally, or alternatively, the UE 104 may be referred to as an Internet-of-Things (IoT) device, an Internet-of-Everything (IoE) device, or machine-type communication (MTC) device, among other examples. In some implementations, a UE 104 may be stationary in the wireless communications system 100. In some other implementations, a UE 104 may be mobile in the wireless communications system 100.

The one or more UEs 104 may be devices in different forms or having different capabilities. Some examples of UEs 104 are illustrated in FIG. 1. A UE 104 may be capable of communicating with various types of devices, such as the network entities 102, other UEs 104, or network equipment (e.g., the core network 106, the packet data network 108, a relay device, an integrated access and backhaul (IAB) node, or another network equipment) , as shown in FIG. 1. Additionally, or alternatively, a UE 104 may support communication with other network entities 102 or UEs 104, which may act as relays in the wireless communications system 100.

A network entity 102 may support communications with the core network 106, or with another network entity 102, or both. For example, a network entity 102 may interface with the core network 106 through one or more backhaul links 116 (e.g., via an S1, N2, N6, or another network interface) . The network entities 102 may communicate with each other over the links 118 (e.g., via an X2, Xn, or another network interface) . In some implementations, the network entities 102 may communicate with each other directly (e.g., between the network entities 102) . In some other implementations, the network entities 102 may communicate with each other indirectly (e.g., via the core network 106) . In some implementations, one or more network entities 102 may include subcomponents, such as an access network entity, which may be an example of an access node controller (ANC) . An ANC may communicate with the one or more UEs 104 through one or more other access network transmission entities, which may be referred to as a radio heads, smart radio heads, or transmission-reception points (TRPs) .

In some implementations, a network entity 102 may be configured in a disaggregated architecture, which may be configured to utilize a protocol stack physically or logically distributed among two or more network entities 102, such as an integrated access backhaul (IAB) network, an open RAN (O-RAN) (e.g., a network configuration sponsored by the O-RAN Alliance) , or a virtualized RAN (vRAN) (e.g., a cloud RAN (C-RAN) ) . For example, a network entity 102 may include one or more of a central unit (CU) , a distributed unit (DU) , a radio unit (RU) , a RAN Intelligent Controller (RIC) (e.g., a Near-Real Time RIC (Near-RT RIC) , a Non-Real Time RIC (Non-RT RIC) ) , a Service Management and Orchestration (SMO) system, or any combination thereof.

An RU may also be referred to as a radio head, a smart radio head, a remote radio head (RRH) , a remote radio unit (RRU) , or a transmission reception point (TRP) . One or more components of the network entities 102 in a disaggregated RAN architecture may be co-located, or one or more components of the network entities 102 may be located in distributed locations (e.g., separate physical locations) . In some implementations, one or more network entities 102 of a disaggregated RAN architecture may be implemented as virtual units (e.g., a virtual CU (VCU) , a virtual DU (VDU) , a virtual RU (VRU) ) .

Split of functionality between a CU, a DU, and an RU may be flexible and may support different functionalities depending upon which functions (e.g., network layer functions, protocol layer functions, baseband functions, radio frequency functions, and any combinations thereof) are performed at a CU, a DU, or an RU. For example, a functional split of a protocol stack may be employed between a CU and a DU such that the CU may support one or more layers of the protocol stack and the DU may support one or more different layers of the protocol stack. In some implementations, the CU may host upper protocol layer (e.g., a layer 3 (L3) , a layer 2 (L2) ) functionality and signaling (e.g., Radio Resource Control (RRC) , service data adaption protocol (SDAP) , Packet Data Convergence Protocol (PDCP) ) . The CU may be connected to one or more DUs or RUs, and the one or more DUs or RUs may host lower protocol layers, such as a layer 1 (L1) (e.g., physical (PHY) layer) or an L2 (e.g., radio link control (RLC) layer, medium access control (MAC) layer) functionality and signaling, and may each be at least partially controlled by the CU.

Additionally, or alternatively, a functional split of the protocol stack may be employed between a DU and an RU such that the DU may support one or more layers of the protocol stack and the RU may support one or more different layers of the protocol stack. The DU may support one or multiple different cells (e.g., via one or more RUs) . In some implementations, a functional split between a CU and a DU, or between a DU and an RU may be within a protocol layer (e.g., some functions for a protocol layer may be performed by one of a CU, a DU, or an RU, while other functions of the protocol layer are performed by a different one of the CU, the DU, or the RU) .

A CU may be functionally split further into CU control plane (CU-CP) and CU user plane (CU-UP) functions. A CU may be connected to one or more DUs via a midhaul communication link (e.g., F1, F1-c, F1-u) , and a DU may be connected to one or more RUs via a fronthaul communication link (e.g., open fronthaul (FH) interface) . In some implementations, a midhaul communication link or a fronthaul communication link may be implemented in accordance with an interface (e.g., a channel) between layers of a protocol stack supported by respective network entities 102 that are in communication via such communication links.

The core network 106 may support user authentication, access authorization, tracking, connectivity, and other access, routing, or mobility functions. The core network 106 may be an evolved packet core (EPC) , or a 5G core (5GC) , which may include a control plane entity that manages access and mobility (e.g., a mobility management entity (MME) , an access and mobility management functions (AMF) ) and a user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW) , a Packet Data Network (PDN) gateway (P-GW) , a user plane function (UPF) ) , or a location management function (LMF) , which is a control plane entity that manages location services. In some implementations, the control plane entity may manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management (e.g., data bearers, signal bearers, etc. ) for the one or more UEs 104 served by the one or more network entities 102 associated with the core network 106.

The core network 106 may communicate with the packet data network 108 over one or more backhaul links 116 (e.g., via an S1, N2, N6, or another network interface) . The packet data network 108 may include an application server 120. In some implementations, one or more UEs 104 may communicate with the application server 120. A UE 104 may establish a session (e.g., a protocol data unit (PDU) session, or the like) with the core network 106 via a network entity 102. The core network 106 may route traffic (e.g., control information, data, and the like) between the UE 104 and the application server 120 using the established session (e.g., the established PDU session) . The PDU session may be an example of a logical connection between the UE 104 and the core network 106 (e.g., one or more network functions of the core network 106) .

In the wireless communications system 100, the network entities 102 and the UEs 104 may use resources of the wireless communication system 100 (e.g., time resources (e.g., symbols, slots, subframes, frames, or the like) or frequency resources (e.g., subcarriers, carriers) to perform various operations (e.g., wireless communications) . In some implementations, the network entities 102 and the UEs 104 may support different resource structures. For example, the network entities 102 and the UEs 104 may support different frame structures. In some implementations, such as in 4G, the network entities 102 and the UEs 104 may support a single frame structure. In some other implementations, such as in 5G and among other suitable radio access technologies, the network entities 102 and the UEs 104 may support various frame structures (i.e., multiple frame structures) . The network entities 102 and the UEs 104 may support various frame structures based on one or more numerologies.

One or more numerologies may be supported in the wireless communications system 100, and a numerology may include a subcarrier spacing and a cyclic prefix. A first numerology (e.g., μ=0) may be associated with a first subcarrier spacing (e.g., 15 kHz) and a normal cyclic prefix. The first numerology (e.g., μ=0) associated with the first subcarrier spacing (e.g., 15 kHz) may utilize one slot per subframe. A second numerology (e.g., μ=1) may be associated with a second subcarrier spacing (e.g., 30 kHz) and a normal cyclic prefix. A third numerology (e.g., μ=2) may be associated with a third subcarrier spacing (e.g., 60 kHz) and a normal cyclic prefix or an extended cyclic prefix. A fourth numerology (e.g., μ=3) may be associated with a fourth subcarrier spacing (e.g., 120 kHz) and a normal cyclic prefix. A fifth numerology (e.g., μ=4) may be associated with a fifth subcarrier spacing (e.g., 240 kHz) and a normal cyclic prefix.

A time interval of a resource (e.g., a communication resource) may be organized according to frames (also referred to as radio frames) . Each frame may have a duration, for example, a 10 millisecond (ms) duration. In some implementations, each frame may include multiple subframes. For example, each frame may include 10 subframes, and each subframe may have a duration, for example, a 1 ms duration. In some implementations, each frame may have the same duration. In some implementations, each subframe of a frame may have the same duration.

Additionally or alternatively, a time interval of a resource (e.g., a communication resource) may be organized according to slots. For example, a subframe may include a number (e.g., quantity) of slots. Each slot may include a number (e.g., quantity) of symbols (e.g., orthogonal frequency division multiplexing (OFDM) symbols) . In some implementations, the number (e.g., quantity) of slots for a subframe may depend on a numerology. For a normal cyclic prefix, a slot may include 14 symbols. For an extended cyclic prefix (e.g., applicable for 60 kHz subcarrier spacing) , a slot may include 12 symbols. The relationship between the number of symbols per slot, the number of slots per subframe, and the number of slots per frame for a normal cyclic prefix and an extended cyclic prefix may depend on a numerology. It should be understood that reference to a first numerology (e.g., μ=0) associated with a first subcarrier spacing (e.g., 15 kHz) may be used interchangeably between subframes and slots.

In the wireless communications system 100, an electromagnetic (EM) spectrum may be split, based on frequency or wavelength, into various classes, frequency bands, frequency channels, etc. By way of example, the wireless communications system 100 may support one or multiple operating frequency bands, such as frequency range designations FR1 (410 MHz –7.125 GHz) , FR2 (24.25 GHz –52.6 GHz) , FR3 (7.125 GHz –24.25 GHz) , FR4 (52.6 GHz –114.25 GHz) , FR4a or FR4-1 (52.6 GHz –71 GHz) , and FR5 (114.25 GHz –300 GHz) . In some implementations, the network entities 102 and the UEs 104 may perform wireless communications over one or more of the operating frequency bands. In some implementations, FR1 may be used by the network entities 102 and the UEs 104, among other equipment or devices for cellular communications traffic (e.g., control information, data) . In some implementations, FR2 may be used by the network entities 102 and the UEs 104, among other equipment or devices for short-range, high data rate capabilities.

FR1 may be associated with one or multiple numerologies (e.g., at least three numerologies) . For example, FR1 may be associated with a first numerology (e.g., μ=0) , which includes 15 kHz subcarrier spacing; a second numerology (e.g., μ=1) , which includes 30 kHz subcarrier spacing; and a third numerology (e.g., μ=2) , which includes 60 kHz subcarrier spacing. FR2 may be associated with one or multiple numerologies (e.g., at least 2 numerologies) . For example, FR2 may be associated with a third numerology (e.g., μ=2) , which includes 60 kHz subcarrier spacing; and a fourth numerology (e.g., μ=3) , which includes 120 kHz subcarrier spacing.

Mechanisms and procedures of L1/L2 based inter-cell mobility for mobility latency reduction may be taken into consideration. This includes configuration and maintenance for multiple candidate cells to allow fast application of configurations for candidate cells, dynamic switch mechanism among candidate serving cells (including SpCell and SCell) for the potential applicable scenarios based on L1/L2 signaling, L1 enhancements for inter-cell beam management, including L1 measurement and reporting, and beam indication, timing advance management, and CU-DU interface signaling to support L1/L2 mobility. These mechanisms are applicable to, for example, the following scenarios: standalone, carrier aggregation (CA) and NR-dual connectivity (DC) case with serving cell change within one configured grant (CG) , intra-DU case and intra-CU inter-DU case (applicable for Standalone and CA) , both intra-frequency and inter-frequency, both FR1 and FR2, source and target cells may be synchronized or non-synchronized.

In one or more implementations, to reduce handover interruption time, solutions to reduce the time for UE reconfiguration, and downlink and uplink synchronization after the handover decision (other parts of dynamic switch not precluded) are also taken into consideration.

Additionally or alternatively, to support L1/L2-based inter-cell mobility for inter-DU scenario (as well as intra-DU scenarios) is considered. The design for intra-DU and inter-DU L1/L2-based mobility sharing as much commonality as reasonable may be taken into consideration.

Additionally or alternatively, assuming that L2 is continued whenever possible (e.g. intra-DU) , without Reset, with the target to avoid data loss, and the additional delay of data recovery is taken into consideration.

Additionally or alternatively, preparation of target cell configurations capable of dynamic switching without need for full configuration is taken into consideration.

Additionally or alternatively, measurement delay may be taken into consideration.

Additionally or alternatively, relying on L1 measurements to trigger L1/L2 mobility is taken into consideration.

Additionally or alternatively, focusing on PCell mobility is taken into consideration.

Additionally or alternatively, L1/L2 mobility including both non-CA (PCell only) and CA scenarios (PCell and SCell) is taken into consideration. This includes the following cases: the target PCell/target SCell (s) is not a current serving cell (CA to CA scenario with PCell change) ; the target PCell is a current SCell; the target SCell is the current PCell.

Additionally or alternatively, DC scenarios are taken into consideration (e.g., PSCell mobility) .

Additionally or alternatively, configuring an L1/L2 inter-cell mobility candidate cell is taken into consideration, such as one RRCReconfiguration message for candidate target cell, one CellGroupConfig information element (IE) for each candidate target cell, or one SpCellConfig IE for each candidate target cell.

The network entity 102 transmits a MAC-CE 122 that includes a handover command to hand over the UE 104 a serving cell (served by the network entity 102) to a target cell with a different PCI. The wherein the handover command includes a trigger indicating to the UE to one or both of perform an aperiodic CSI process in the target cell or track a TRS in the target cell. The UE 104 receives the MAC-CE in a PDSCH and returns an acknowledgment (ACK) 124 to the network entity 102. The handover process then continues and the UE 104 subsequently performs an aperiodic CSI process in the target cell or tracks a TRS in the target cell. Including the trigger in the handover command reduces the latency of the handover and allow the UE 104 to start transmission and reception in the target cell as soon as possible.

Although communication between devices is discussed herein, such as between UEs 104 and network entities 102, using MAC-CE including a handover command, it is should be noted that various other types of signaling may be used for other data or information.

A set of CSI-AperiodicTriggerState is defined in radio resource control (RRC) and any one of them can be triggered by the handover MAC-CE message. Upon triggering of a CSI-AperiodicTriggerState, the UE measures the associated CSI-RS resource and sends an aperiodic CSI report to the network entity using the PUSCH scheduled by the same MAC-CE.

FIG. 2 illustrates an example information element 200 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The information element 200 is an CSI-AperiodicTriggerStateList IE used to configure the UE with a list of aperiodic trigger states. Each codepoint of the DCI or MAC-CE field "CSI request" is associated with one trigger state. Upon reception of the value associated with a trigger state, the UE will perform measurement of CSI-RS, channel state information interference measurement (CSI-IM) and/or synchronization signal block (SSB) (reference signals) and aperiodic reporting on L1 according to all entries in the associatedReportConfigInfoList for that trigger state.

The IE 200 includes an ap-CSI-MultiplexingMode field that indicates if the behavior of transmitting aperiodic CSI on the first PUSCH repetitions corresponding to two SRS resource sets configured in srs-ResourceSetToAddModList or srs-ResourceSetToAddModListDCI-0-2 with usage 'codebook' or 'noncodebook' is enabled or not.

The IE 200 also includes a csi-IM-ResourcesForInterference field that indicates a CSI-IM-ResourceSet for interference measurement. The entry number in csi-IM-ResourceSetList in the CSI-ResourceConfig indicated by csi-IM-ResourcesForInterference in the CSI-ReportConfig indicated by reportConfigId (e.g., value 1 corresponds to the first entry, value 2 to the second entry, and so on) . The indicated CSI-IM-ResourceSet should have exactly the same number of resources like the NZP-CSI-RS-ResourceSet indicated in resourceSet within nzp-CSI-RS.

The IE 200 also includes a csi-SSB-ResourceSet, csi-SSB-ResourceSet2 field that indicates a CSI-SSB-ResourceSet for channel measurements. The entry number in csi-SSB-ResourceSetList in the CSI-ResourceConfig indicated by resourcesForChannelMeasurement in the CSI-ReportConfig indicated by reportConfigId above (e.g., value 1 corresponds to the first entry, value 2 to the second entry, and so on) .

The IE 200 also includes an nzp-CSI-RS-ResourcesForInterference field that indicates an NZP-CSI-RS-ResourceSet for interference measurement. The entry number in nzp-CSI-RS-ResourceSetList in the CSI-ResourceConfig indicated by nzp-CSI-RS-ResourcesForInterference in the CSI-ReportConfig indicated by reportConfigId above (e.g., value 1 corresponds to the first entry, value 2 to the second entry, and so on) .

The IE 200 also includes a qcl-info, qcl-info2 field that indicates a list of references to TCI-States for providing the quasi co location (QCL) source and QCL type for each NZP-CSI-RS-Resource listed in nzp-CSI-RS-Resources of the NZP-CSI-RS-ResourceSet indicated by resourceSet within nzp-CSI-RS. Each TCI-StateId refers to the TCI-State which has this value for tci-StateId and is defined in tci-StatesToAddModList in the PDSCH-Config included in the BWP-Downlink corresponding to the serving cell and to the DL bandwidth part (BWP) to which the resourcesForChannelMeasurement (in the CSI-ReportConfig indicated by reportConfigId above) belong to. First entry in qcl-info corresponds to first entry in nzp-CSI-RS-Resources of that NZP-CSI-RS-ResourceSet, second entry in qcl-info corresponds to second entry in nzp-CSI-RS-Resources, and so on. When this field is absent for aperiodic CSI RS, the UE shall use QCL information included in the "indicated" DL only/Joint TCI state.

The IE 200 also includes a reportConfigId field that indicates the reportConfigId of one of the CSI-ReportConfigToAddMod configured in CSI-MeasConfig.

The IE 200 also includes a resourcesForChannel2 field that configures reference signals for channel measurement corresponding to the second resource set for L1-reference signal received power (RSRP) measurement as configured in IE CSI-ResourceConfig when nrofReportedGroups-r17 is configured in IE CSI-ReportConfig. If this is present, network configures csi-SSB-ResourceSetExt instead of csi-SSB-ResourceSet and the UE ignores csi-SSB-ResourceSet in resourcesForChannel, and the resourcesForChannel configures the reference signals for channel measurement corresponding to the first resource set for L1-RSRP measurement.

The IE 200 also includes a resourceSet field that indicates a NZP-CSI-RS-ResourceSet for channel measurements. The entry number in nzp-CSI-RS-ResourceSetList in the CSI-ResourceConfig indicated by resourcesForChannelMeasurement in the CSI-ReportConfig indicated by reportConfigId above (value 1 corresponds to the first entry, value 2 to the second entry, and so on) .

Various fields of the IE 200 include conditional presence indicators, including aperiodic, CSI-IM-ForInterference, NZP-CSI-RS-ForInterference, and NoUnifiedTCI.

The aperiodic conditional presence indicator indicates that the field is mandatory present if the NZP-CSI-RS-Resources in the associated resourceSet have the resourceType aperiodic. The field is absent otherwise.

The CSI-IM-ForInterference conditional presence indicator indicates that this field is mandatory present if the CSI-ReportConfig identified by reportConfigId is configured with csi-IM-ResourcesForInterference; otherwise it is absent.

The NZP-CSI-RS-ForInterference conditional presence indicator indicates that this field is mandatory present if the CSI-ReportConfig identified by reportConfigId is configured with nzp-CSI-RS-ResourcesForInterference; otherwise it is absent.

The NoUnifiedTCI conditional presence indicator indicates that this field is absent, Need R, if unifiedTCI-StateType is configured for the serving cell in which the CSI-AperiodicTriggerStateList is included. It is optionally present, Need R, otherwise.

In Release 17, a UE can be configured with periodic, semi-persistent or aperiodic CSI-RS resources for channel measurement to acquire channel information, and send the measured CSI state to the gNB in CSI feedback in physical uplink control channel (PUCCH) or PUSCH. In particular, aperiodic CSI feedback is designed to allow a UE to quickly measure the channel information and send the CSI feedback to the network. Aperiodic CSI measurement and feedback is configured as AperiodicCSI and can be triggered by a DCI format 0_1 with the field “CSI request” . When the CSI request field is set to a non-zero value, a corresponding CSI measurement and feedback process is activated, and the CSI can be quickly measured and sent to the gNB in a PUSCH.

It should be noted that this process is defined only for the serving cell. The DCI 0_1 carrying the CSI request field, the NZP CSI-RS resource for channel measurement, and ZP or NZP CSI-RS resource for interference measurement (if configured) , and the PUSCH carrying the CSI feedback are all sent in the same cell. If this mechanism is applied to a L1/L2 trigger handover, the DCI format 0_1 carrying the CSI request field needs to be sent to the UE from the target cell after the handover of the UE to the target cell is completed. The delay of this can be long, because the long effective time of the MAC-CE message (typically 3ms) . There is also additional delay between the DCI format 0_1 carrying the CSI request and the aperiodic CSI-RS resource to allow the UE to apply the indicated TCI state to the aperiodic CSI-RS resource.

A trigger state can be initiated using the CSI request field in DCI. When all the bits of CSI request field in DCI are set to zero, no CSI is requested. When the number of configured CSI triggering states in CSI-AperiodicTriggerStateList is greater thanwhere N_TS is the number of bits in the DCI CSI request field, the UE receives a subselection indication used to map up totrigger states to the codepoints of the CSI request field in DCI. N_TS is configured by the higher layer parameter reportTriggerSize where N_TS∈ {0, 1, 2, 3, 4, 5, 6} . When the UE would transmit a PUCCH with hybrid automatic repeat request (HARQ) -ACK information in slot n corresponding to the physical downlink shared channel (PDSCH) carrying the subselection indication, the corresponding action in and UE assumption on the mapping of the selected CSI trigger state (s) to the codepoint (s) of DCI CSI request field shall be applied starting from the first slot that is after slot where μ is the sub-carrier spacing (SCS) configuration for the PUCCH andis the subcarrier spacing configuration for k_mac with a value of 0 for frequency range 1, and k_mac is provided by K-Mac or k_mac=0 if K-Mac is not provided.

When the number of CSI triggering states in CSI-AperiodicTriggerStateList is less than or equal tothe CSI request field in DCI directly indicates the triggering state.

For each aperiodic CSI-RS resource in a CSI-RS resource set associated with each CSI triggering state, the UE is indicated the quasi co-location configuration of quasi co-location RS source (s) and quasi co-location type (s) , as described in clause 5.1.5, through higher layer signaling of qcl-info which contains a list of references to TCI-State's for the aperiodic CSI-RS resources associated with the CSI triggering state. If a State referred to in the list is configured with a reference to an RS configured with qcl-Type set to 'typeD' , that RS may be an SS/physical broadcast channel (PBCH) block located in the same or different component carrier (CC) /DL BWP or a CSI-RS resource configured as periodic or semi-persistent located in the same or different CC/DL BWP.

If the scheduling offset between the last symbol of the physical downlink control channel (PDCCH) carrying the triggering DCI and the first symbol of the aperiodic CSI-RS resources in a NZP-CSI-RS-ResourceSet configured without higher layer parameter trs-Info is smaller than the UE reported threshold beamSwitchTiming, when the reported value is one of the values ofand enableBeamSwitchTiming is not provided, or is smaller thanwhen the UE provides beamSwitchTiming-r16, enableBeamSwitchTiming is provided and the NZP-CSI-RS-ResourceSet is configured with the higher layer parameter repetition set to 'off' or configured without the higher layer parameter repetition, or is smaller than the UE reported threshold beamSwitchTiming-r16, when enableBeamSwitchTiming is provided and the NZP-CSI-RS-ResourceSet is configured with the higher layer parameter repetition set to 'on' .

If the scheduling offset between the last symbol of the PDCCH carrying the triggering DCI and the first symbol of the aperiodic CSI-RS resources in a NZP-CSI-RS-ResourceSet is equal to or greater than the UE reported threshold beamSwitchTiming when the reported value is one of the values ofand enableBeamSwitchTiming is not provided and the NZP-CSI-RS-ResourceSet is not configured with higher layer parameter trs-Info, or is equal to or greater than the UE reported threshold beamSwitchTiming when the reported value is one of the values of and the NZP-CSI-RS-ResourceSet is configured with higher layer parameter trs-Info, or is equal to or greater thanwhen the UE provides beamSwitchTiming-r16 and enableBeamSwitchTiming is provided and the NZP-CSI-RS-ResourceSet is configured with the higher layer parameter repetition set to 'off' or configured without the higher layer parameters repetition and trs-Info, or is equal to or greater than the UE reported threshold beamSwitchTiming-r16, when enableBeamSwitchTiming is provided and the NZP-CSI-RS-ResourceSet is configured with the higher layer parameter repetition set to 'on' , the UE is expected to apply the QCL assumptions in the indicated TCI states for the aperiodic CSI-RS resources in the CSI triggering state indicated by the CSI trigger field in DCI.

The delay incurred by transmitting a DCI format 0_1 to trigger the aperiodic CSI process after the handover is complete may cause service disruption during the handover process. The techniques discussed herein reduce this delay to facilitate seamless handover.

In aspects of this disclosure, assuming L1/2 mobility trigger information is conveyed in a MAC CE.

In aspects of this disclosure, assuming the MAC CE for L1/2 mobility trigger contains at least a candidate configuration index is taken into consideration.

In aspects of this disclosure, if the MAC CE can indicate TCI state (s) (or other beam info) to activate for the target Cell (s) , is taken into consideration.

In aspects of this disclosure, for Release 18 L1/L2 mobility, L1 intra-frequency measurement for candidate cell being supported is taken into consideration. At least the following aspects are taken into consideration: assumption of Rel-17 inter-cell beam management (ICBM) CSI measurement as starting point; whether and how to apply relaxation for the restrictions imposed on the Release 17 intra-frequency L1 non-serving cell measurement (e.g., system frame number (SFN) offset alignment compared with serving cell, BWP setting, i.e. non-serving cell SSB should be covered by serving cell active BWP, introduction of symbol level gap or SSB based measurement timing configuration (SMTC) for larger Rx timing difference (i.e. larger than CP length) ; commonality with intra-frequency L3 measurement; commonality with L1 inter-frequency measurement for measurement configuration.

In aspects of this disclosure, for Release 18 L1/L2 mobility, the potential impact of L1 inter-frequency measurement is taken into consideration. In aspects of this disclosure, assumption of at least the following is taken into consideration: the frequency of the measured RS not covered by any of the active BWPs of SpCell and Scells configured for a UE, but covered by some of the configured BWPs of SpCell and Scells configured for a UE; the frequency of the measured RS not covered by any of the configured BWPs of SpCell and Scells configured for a UE. In aspects of this disclosure, commonality with L1 intra-frequency measurement for measurement configuration is taken into consideration.

In aspects of this disclosure, scenarios not included in intra-frequency are regarded as inter-frequency, which includes at least the following scenarios: the frequency of the measured RS not covered by any of the active BWPs of SpCell and Scells configured for a UE, but covered by some of the configured BWPs of SpCell and Scells configured for a UE; the frequency of the measured RS not covered by any of the configured BWPs of SpCell and Scells configured for a UE.

In aspects of this disclosure, the introduction of measurement gap and SMTC for L1 inter-frequency measurement, if any, is taken into consideration.

In aspects of this disclosure, for Release 18 L1/L2 mobility, the following is taken into consideration. SSB is supported for L1 intra-frequency measurement. SSB is supported for L1 inter-frequency measurement if inter-frequency L1 measurements are supported. Study of the following L1 measurement RS for candidate cell: CSI-RS for tracking, beam management, CSI and mobility, CSI-IM, which is for L1 intra-frequency and L1 inter-frequency (if supported) .

In aspects of this disclosure, for candidate cell measurement for Release 18 L1/L2 mobility, the following is taken into consideration. L1-RSRP is supported for intra-frequency candidate cell measurement. Study of the following measurement quantities for candidate cell measurement: L1-RSRP for inter-frequency (if supported) ; L1-signal to interference noise ratio (SINR) for intra-frequency and inter-frequency (if supported) .

In aspects of this disclosure, the use case and the benefit of UL measurement instead of/in addition to DL L1 measurement, is taken into consideration, which includes: how the UL measurement result is used, e.g., handover decision; signals/channels used for UL measurement, e.g., sounding reference signal (SRS) ; other WGs, e.g. definition of gNB measurement, interface to transfer RS configuration or measurement results.

In aspects of this disclosure, potential enhancements to perform at least the following procedures prior to the reception of L1/L2 cell switch command aiming at the reduction of handover delay /interruption is taken into consideration: DL synchronization for candidate cell (s) ; TRS tracking for candidate cell (s) ; CSI acquisition for candidate cell (s) ; activation/selection of TCI states for candidate cell (s) ; whether the above procedures prior to the reception of L1/L2 cell switch command can be performed on candidate cell when it is deactivated SCell.

In aspects of this disclosure, for Release 18 LTM, L1 inter-frequency measurement is supported is taken into consideration.

In aspects of this disclosure, enhancements to reduce the handover delay /interruption for Release 18 LTM is taken into consideration. This includes support at least DL synchronization for candidate cell (s) based on at least SSB before cell switch command, and the necessary mechanism, e.g., signaling and UE capability.

In aspects of this disclosure, for L1 measurement report for Release 18 L1/L2 mobility, if UE event triggered report for L1 measurement is supported based on further study, at least the following aspects may be considered: how to define UE event and exact definition of events; report container; resource allocation/assignment for UE event triggered report; necessity of indication to gNB when the condition UE event is met, and how; necessity to define the condition to start/stop the reporting; contents of the report/reporting format, PCI, RS identifier (ID) , measurement result etc.; the interaction with filtered L1 measurement results (if supported) ; support of simultaneous configuration of both UE event triggered and any of periodic/semi-persistence/aperiodic reporting, and solutions when both of them are configured; report destination, whether the report is sent to serving cell only or can be sent to one or more candidate cell (s) ; benefit when L3 measurement is involved

In aspects of this disclosure, for candidate cell measurement for Release 18 LTM, the following is taken into consideration: SSB based L1-RSRP is supported for intra-frequency measurement; SSB based L1-RSRP is supported for inter-frequency measurement; L1-SINR, CSI-RS based L1-RSRP.

In aspects of this disclosure, the beam indication of candidate cell (s) for Release 18 LTM being designed based on the following is taken into consideration: beam indication for Release 18 LTM is designed based on Release 17 unified TCI framework, if both serving cell and candidate cell support Release 17 unified TCI framework; whether/how to design mechanism for Beam indication for Release 18 LTM when at least one from serving cell and candidate cell supports only Release 15 TCI framework; how and whether to indicate the new serving cell (s) and timing for beam indication.

In aspects of this disclosure, for gNB scheduled L1 measurement report for Release 18 LTM, report as UCI is taken into consideration. This includes semi-persistent report on PUSCH, and aperiodic report on PUSCH are supported; periodic and semi- persistent PUCCH; in a single report instance, report for serving cell and candidate cell (s) for intra-frequency and/or inter-frequency can be included.

In aspects of this disclosure, for beam indication timing for Release 18 LTM, the following is taken into consideration: Beam indication together with cell switch command; for Release 17 unified TCI framework, Beam indication indicates TCI state for each target serving cell; Beam indication before cell switch command; Beam indication after cell switch command; activation of TCI state (s) of target serving and/or candidate cell (s) .

A MAC-CE message is used as an LTM handover command, and the use of DCI as LTM handover command may also be taken into consideration. The techniques discussed herein describe using the MAC-CE message to signal, to the UE, the handover (HO) of the UE from one cell to another (e.g., from a serving cell to a target cell) .

In order to prepare for cell switching, before receiving the cell switch command, the UE can conduct measurement from multiple potential target cells on the DL synchronization signal based on at least SSB. Using CSI-RS for beam management may also be considered. The UE conducts measurements based on these configured SSB signals and reports the measured L1-RSRP (and possibly L1-SINR) to the network entity (e.g., gNB) . Based on the UE reporting, the network entity (e.g., gNB) decides which neighbor cell to handover the UE to, and sends the UE the handover command in a handover MAC-CE message. Before receiving the handover message, the UE has no idea of the target cell, and the only information the UE has regarding this target cell is the configured DL RS resources and its measurement (L1-RSRP, L1-SINR) . In order disrupt the services as little as possible and make the handover as smooth as possible, to start transmission and reception in the new cell, the UE establishes the transmission and reception parameters in the new cell, such as synchronization, TRS tracking, beam indication, CSI acquisition, buffer status, and so forth. In particular, additional channel state information is typically required by the UE and the network entity (e.g., gNB) . It is desirable that the CSI acquisition process starts as soon as the UE receives the handover command.

To expedite the CSI acquisition process, a trigger in the MAC-CE message to trigger an aperiodic CSI report and the associated CSI-RS resource. The same MAC-CE also includes scheduling information to schedule the PUSCH for the UE to report the CSI feedback to the network entity (e.g., gNB) in the target cell. To facilitate MAC-CE triggered aperiodic CSI process in the target cell, several aspects are addressed, including how to configure aperiodic CSI-RS resources in neighbor cells, how to configure and trigger aperiodic CSI process in the target cell from the current serving cell, how to schedule the PUSCH for the CSI feedback in the target cell, and related application time for various signals. These aspects are discussed below. The aperiodic CSI process includes receiving an aperiodic CSI-RS resource, and sending the CSI information to the network entity (e.g., gNB) .

With respect to configuration of CSI-RS resource for CSI acquisition in a cell with different PCI, an aperiodic NZP CSI-RS resource for CSI acquisition is configured for the target cell before the UE receives the handover command. Because this is done before the UE (and possibly the network entity (e.g., gNB) ) knows the target cell, this may be configured for more than one candidate cell, each with its own CSI-RS resource. This can be made possible by configuring the NZP CSI-RS resource for CSI with a PCI that is different from the current serving cell. One or more aperiodic NZP-CSI-RS resource for channel measurement can be configured in a neighbor cell. That information can be configured in each candidate cell configuration.

With respect to configuration of aperiodic CSI trigger state in a cell with different PCI, the CSI-AperiodicTriggerState in Release 17 is defined only for the serving cell. In order to trigger an aperiodic CSI report in a target cell, which is one of several candidate cells before the handover, CSI-AperiodicTriggerState for another cell with different PCI is defined before the handover. This can be done by including the physical cell identifier (PCI) or the candidate cell configuration index in the CSI-AperiodicTriggerState (in RRC message) , or including the PCI or the candidate cell configuration index in the CSI-RS resource for channel measurement (resourceForChannel) . The list CSI-AperiodicTriggerStateList contains a set of aperiodic CSI trigger states, some of which are from neighbor cells with different PCIs.

In one or more implementations, only aperiodic NZP-CSI-RS resource for channel measurement is configured in each neighbor cell. This enables implicit triggering of the aperiodic CSI process in the target cell after handover, as discussed in more detail below.

With respect to triggering of aperiodic CSI report and associated aperiodic NZP-CSI-RS resource, the handover command in the MAC-CE can include a CSI request field to trigger an aperiodic CSI report and associated aperiodic NZP-CSI-RS resource in the target cell. The CSI-AperiodicTriggerStateList contains a list of aperiodic CSI trigger states, some of them are from neighbor cells with different PCI. The CSI request field contains an indicator to trigger one of the configured CSI-AperiodicTriggerState from the target cell after the handover (e.g., in accordance with the timeline discussed below) . According to the triggered CSI-AperiodicTriggerState, both the associated CSI-RS and the PUSCH carrying the measured CSI will be sent after the handover following the timeline discussed in FIG. 3 below.

When only one aperiodic CSI state is configured in the target cell, there is no need to explicitly indicate the CSI-AperiodicTriggerState in the target cell. The CSI request field can be absent from the handover command in the MAC-CE message in this case.

FIG. 3 illustrates an example handover timeline 300 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The example handover timeline 300 is a timeline for L1 or L2 triggered handover using the techniques discussed herein and illustrates the application time of the handover command. The example handover timeline 300 is illustrated with one network entity (e.g., a gNB) 302, a UE 304, and another network entity (e.g., another gNB) 306. Time illustrated along the vertical arrows, progressing from top to bottom. The network entity 302 is a serving cell (the cell currently serving the UE 304) and the network entity 306 is the target cell (the cell to which the UE 304 is being handed over) .

At 308, the handover MAC-CE message is sent from the current serving cell (the network entity 302) to move the UE to the target cell (the network entity 306) . After the UE 304 transmits a PUCCH 310 carrying an ACK corresponding to the PDSCH carrying the MAC CE in slot n, the actual handover takes place at time T_HO, also referred to as the actual handover time, illustrated at 312. The handover begins in slot where T_g is a guard time (atime gap) for the UE 304 to switch its radio frequency (RF) for when the target cell (network entity 306) and the current serving cell (network entity 302) are in different frequencies or different bands, μ is the subcarrier spacing of the carrier where the ACK is sent (the PUSCH and the PUCCH may be sent in the same or different subcarriers) , andis a time of k subframes in the numerology μ. The parameter k can be a fixed value in the specification, for example k=3 in NR Release 17, or it can be signaled to the wireless network by the UE 304 as part of its capability. The handover MAC-CE message also triggers the aperiodic CSI-RS resource to be sent from the target cell at 314 after the handover. The time between the last symbol of the PUCCH at 310 to the time T₁ of the AP-CSI-RS resource is equal to or larger than a threshold (T_switch) . This is to allow the UE 304 to switch to the new beam in the target cell. The switching time T_switch is a UE capability parameter reported by the UE 304 to the network, and can be beamSwitchTiming, beamAppTime_r17, or a new beam switching time defined for beam switching during handover. If the subcarrier spacing is different between the target cell (network entity 306) and the original serving cell (network entity 302) , T_switch is defined in terms of number of symbols with the subcarrier in the target cell (network entity 306) .

The aperiodic CSI-RS process includes the UE 304 receiving the aperiodic CSI-RS at 314, generating the CSI feedback, and transmitting the CSI feedback in a PUSCH 316. The UE 304 and the network entity 306 can then proceed with various DL and UL transmissions 318.

The handover MAC-CE message at 308 includes the scheduling information for the PUSCH in the target cell for the UE 304 to send the CSI feedback information (at 316) to the network entity 306 in the new cell. The scheduling information for the PUSCH can include time and frequency domain resource assignment, frequency hopping flag, modulation and coding scheme, HARQ process number, transmit power control (TPC) command, and so forth. The parameter setting, including default parameter of the PUSCH, of random access response (RAR) UL grant for message 3 PUSCH in the random access procedure can be reused. The new data indication bit may be ignored. Because the network entity 302 in the current serving cell does not have enough channel state information of the target cell, it cannot schedule with transmit precoding matrix index (TPMI) so there is no need to include TPMI or rank indicator (RI) in the scheduling information. In one or more implementations, only single port (therefore single layer, single codeword) PUSCH transmission can be scheduled. Compared with scheduling the PUSCH with a DCI after the handover, there is no performance loss with including the scheduling information in the handover MAC-CE message at 308. On the other hand, because the network entity 306 does not wait for the handover to complete to send the DCI format to schedule the PUSCH, the delay of the aperiodic CSI-RS and generation of the CSI feedback is reduced.

With respect to configuration and coordination between the serving cell and the target cell by higher layer, the configuration of the aperiodic CSI-RS resource and the aperiodic CSI feedback is coordinated between the DU at the target cell and the DU at the serving cell through the CU. Through coordination, the CUs and DUs at the target cell and the serving cell make sure they are in sync with each other and the aperiodic CSI process triggered by the handover MAC-CE message sent by the network entity 302 of the current serving cell at 308 will be executed by the target cell.

Additionally or alternatively, to expediate triggering of TRS tracking using MAC-CE, the handover MAC-CE message is also used to signal the UE to start tracking the CSI-RS resource for tracking (TRS, or NZP-CSI-RS resource with “trs-info” configured) in the target cell for fast tracking in the target cell. Because the UE receives the handover MAC-CE message in the current serving cell (network entity 302) and the TRS is sent in the target cell (network entity 306) , the TRS is configured for the UE 304 before the handover. This includes the NZP-CSI-RS resource of the TRS being configured with a PCI different from the current serving cell. The UE 304 can be signaled in the handover MAC-CE message to start tracking one of several TRSs (possibly from one or more candidate cells with different PCIs) by a TRS activation field. This field can indicate one of the configured TRSs for the UE 304 to track after the handover. In one example, this field explicitly signals the NZP-CSI-RS resource ID of the TRS. In another example, the MAC- CE may include a bitmap where each bit corresponds to one of the set of configured TRSs. In this case a set of TRS with possibly different PCIs is configured in RRC.

FIG. 4 illustrates an example message 400 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The message 400 is an example of supporting a set of TRS with possibly different PCIs by configuring in RRC. The message 400 is an NZP-CSI-RS-ResourceSet RRC message.

The message 400 includes a trs-Info field that can be set to “true” to tell the UE this is a set of TRS.

An LTP-HO-NeighborCell-TRS field indicates to the UE that this set is defined as a set of TRS in neighbor cells. When this field is enabled (set to “true” ) , the UE understands the field contains a set of TRS configured for tracking in neighbor cells. Before the UE receives the handover MAC-CE message, the UE does not need to track any of the TRS in this set because the UE is not activated in these cells. When the serving cell (network entity) sends the UE the handover MAC-CE message, after the UE has become activated in the target cell network entity (e.g., T_HO) , the UE starts to track the TRS in the target cell.

Another method to configure and activate the TRS in the target cell is to configure 1 TRS for each neighbor cell (with the same PCI) . The handover MAC-CE message includes the PCI of the target cell. The only TRS in the target cell is activated with the handover. Because the sole TRS configured in the target cell is implied by the target cell ID in the handover MAC-CE message, there is no need to include an explicit TRS resource ID in the MAC-CE.

Similar to the aperiodic CSI process, configuration of tracking of TRS in the target cell after handover is also coordinated between the serving cell and the target cell through higher layers. The DUs at the serving cell and the target cell coordinate through the CU to ensure the TRS in the target cell is properly configured by the serving cell before the handover promptly and transmitted by the target cell to the UE after the handover.

Accordingly, the techniques discussed herein expedite the L1/L2 triggered handover by incorporating the trigger for aperiodic CSI feedback and trigger for tracking TRS in the target cell into the handover MAC-CE message. By triggering the aperiodic CSI process in the Handover MAC-CE before the actual handover time (T_HO) , the Aperiodic NZP-CSI-RS resource can be transmitted to the UE earlier, as well as the PUSCH carrying the CSI feedback. This reduces the CSI acquisition delay in the target cell and allows the transmission to resume as soon as possible in the target cell. By implicitly or explicitly triggering the TRS in the target cell in the handover MAC-CE message, the UE can quickly establish tracking in the target cell.

FIG. 5 illustrates an example of a block diagram 500 of a device 502 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The device 502 may be an example of a network entity 102 as described herein. The device 502 may support wireless communication with one or more network entities 102, UEs 104, or any combination thereof. The device 502 may include components for bi-directional communications including components for transmitting and receiving communications, such as a processor 504, a memory 506, a transceiver 508, and an I/O controller 510. These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces (e.g., buses) .

The processor 504, the memory 506, the transceiver 508, or various combinations thereof or various components thereof may be examples of means for performing various aspects of the present disclosure as described herein. For example, the processor 504, the memory 506, the transceiver 508, or various combinations or components thereof may support a method for performing one or more of the operations described herein.

In some implementations, the processor 504, the memory 506, the transceiver 508, or various combinations or components thereof may be implemented in hardware (e.g., in communications management circuitry) . The hardware may include a processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure. In some implementations, the processor 504 and the memory 506 coupled with the processor 504 may be configured to perform one or more of the functions described herein (e.g., executing, by the processor 504, instructions stored in the memory 506) .

For example, the processor 504 may support wireless communication at the device 502 in accordance with examples as disclosed herein. Processor 504 may be configured as or otherwise support to: generate a MAC-CE that includes a handover command to hand over a UE from a serving cell to a target cell with a different PCI, where the handover command includes a trigger indicating to the UE to perform one or both of an aperiodic CSI process in the target cell or track a TRS in the target cell; transmit, to the UE, the MAC-CE.

Additionally or alternatively, the processor 504 may be configured to or otherwise support: to transmit, to the UE, RRC signaling indicating CSI reference signal resources for channel measurement with PCIs different from the PCI of the serving cell; to transmit, to the UE, RRC signaling indicating aperiodic CSI trigger state in cells with PCIs different from the PCI of the serving cell; to transmit, to the UE, RRC signaling indicating CSI-RS resources for TRS in cells with PCIs different from the PCI of the serving cell; where the handover command including a trigger indicating to perform an aperiodic CSI process in the target cell indicates a CSI-AperiodicTriggerState explicitly; where the handover command including a trigger indicating to perform an aperiodic CSI process in the target cell indicates an only CSI-AperiodicTriggerState in the target cell implicitly; where the MAC-CE including the handover command also includes a scheduling information of a physical uplink shared channel in the target cell for the UE to send aperiodic CSI feedback; where the scheduling information in the MAC-CE follows a random-access response uplink grant in a random-access procedure; where the handover command including a trigger indicating to track the TRS in the target cell indicates a TRS resource explicitly; where the handover command including a trigger indicating to track the TRS in the target cell indicates an only TRS resource configured in the target cell implicitly; where the MAC-CE including the handover command also includes scheduling information of a physical uplink shared channel in the target cell for CSI feedback, the scheduling information including at least a time and a frequency resource; to coordinate with the target cell through centralized units and distributed units of the apparatus and a network entity in the target cell.

For example, the processor 504 may support wireless communication at the device 502 in accordance with examples as disclosed herein. Processor 504 may be configured as or otherwise support a means for generating a MAC-CE that includes a handover command to hand over a UE from a serving cell to a target cell with a different PCI, where the handover command includes a trigger indicating to the UE to perform one or both of an aperiodic CSI process in the target cell or track a TRS in the target cell; and transmitting, to the UE, the MAC-CE.

Additionally or alternatively, the processor 504 may be configured to or otherwise support: transmitting, to the UE, RRC signaling indicating CSI reference signal resources for channel measurement with PCIs different from the PCI of the serving cell; transmitting, to the UE, RRC signaling indicating aperiodic CSI trigger state in cells with PCIs different from the PCI of the serving cell; transmitting, to the UE, RRC signaling indicating CSI-RS resources for TRS in cells with PCIs different from the PCI of the serving cell; where the handover command including a trigger indicating to perform an aperiodic CSI process in the target cell indicates a CSI-AperiodicTriggerState explicitly; where the handover command including a trigger indicating to perform an aperiodic CSI process in the target cell indicates an only CSI-AperiodicTriggerState in the target cell implicitly; where the MAC-CE including the handover command also includes a scheduling information of a physical uplink shared channel in the target cell for the UE to send aperiodic CSI feedback; where the scheduling information in the MAC-CE follows a random-access response uplink grant in a random-access procedure; where the handover command including a trigger indicating to track the TRS in the target cell indicates a TRS resource explicitly; where the handover command including a trigger indicating to track the TRS in the target cell indicates an only TRS resource configured in the target cell implicitly; where the MAC-CE including the handover command also includes scheduling information of a physical uplink shared channel in the target cell for CSI feedback, the scheduling information including at least a time and a frequency resource; coordinating with the target cell through centralized units and distributed units of an apparatus implementing the method and a network entity in the target cell.

The processor 504 may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some implementations, the processor 504 may be configured to operate a memory array using a memory controller. In some other implementations, a memory controller may be integrated into the processor 504. The processor 504 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 506) to cause the device 502 to perform various functions of the present disclosure.

The memory 506 may include random access memory (RAM) and read-only memory (ROM) . The memory 506 may store computer-readable, computer-executable code including instructions that, when executed by the processor 504 cause the device 502 to perform various functions described herein. The code may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. In some implementations, the code may not be directly executable by the processor 504 but may cause a computer (e.g., when compiled and executed) to perform functions described herein. In some implementations, the memory 506 may include, among other things, a basic I/O system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The I/O controller 510 may manage input and output signals for the device 502. The I/O controller 510 may also manage peripherals not integrated into the device 502. In some implementations, the I/O controller 510 may represent a physical connection or port to an external peripheral. In some implementations, the I/O controller 510 may utilize an operating system such as or another known operating system. In some implementations, the I/O controller 510 may be implemented as part of a processor, such as the processor 504. In some implementations, a user may interact with the device 502 via the I/O controller 510 or via hardware components controlled by the I/O controller 510.

In some implementations, the device 502 may include a single antenna 512. However, in some other implementations, the device 502 may have more than one antenna 512 (i.e., multiple antennas) , including multiple antenna panels or antenna arrays, which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver 508 may communicate bi-directionally, via the one or more antennas 512, wired, or wireless links as described herein. For example, the transceiver 508 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 508 may also include a modem to modulate the packets, to provide the modulated packets to one or more antennas 512 for transmission, and to demodulate packets received from the one or more antennas 512.

FIG. 6 illustrates an example of a block diagram 600 of a device 602 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The device 602 may be an example of UE 104 as described herein. The device 602 may support wireless communication with one or more network entities 102, UEs 104, or any combination thereof. The device 602 may include components for bi-directional communications including components for transmitting and receiving communications, such as a processor 604, a memory 606, a transceiver 608, and an I/O controller 610. These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces (e.g., buses) .

The processor 604, the memory 606, the transceiver 608, or various combinations thereof or various components thereof may be examples of means for performing various aspects of the present disclosure as described herein. For example, the processor 604, the memory 606, the transceiver 608, or various combinations or components thereof may support a method for performing one or more of the operations described herein.

In some implementations, the processor 604, the memory 606, the transceiver 608, or various combinations or components thereof may be implemented in hardware (e.g., in communications management circuitry) . The hardware may include a processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure. In some implementations, the processor 604 and the memory 606 coupled with the processor 604 may be configured to perform one or more of the functions described herein (e.g., executing, by the processor 604, instructions stored in the memory 606) .

For example, the processor 604 may support wireless communication at the device 602 in accordance with examples as disclosed herein. Processor 604 may be configured as or otherwise support to: receive, from a first network entity, a MAC-CE that includes a handover command for handover of a UE from a serving cell to a target cell with a different PCI; perform, in response to the handover command, an aperiodic CSI process in the target cell or track, in response to the handover command, a TRS in the target cell.

Additionally or alternatively, the processor 604 may be configured to or otherwise support: where the apparatus is configured with CSI reference signal resources for channel measurement with PCIs different from the PCI of the serving cell; where the apparatus is configured with aperiodic CSI trigger states in cells with PCIs different from the PCI of the serving cell; where the apparatus is configured with TRS in cells with PCIs different from the PCI of the serving cell; to measure a channel from an aperiodic CSI reference signal resource in the target cell following a CSI-AperiodicTriggerState signaled by the handover command explicitly; to measure a channel from an aperiodic CSI reference signal resource in the target cell following an only CSI-AperiodicTriggerState configured in the target cell; to transmit, to a second network entity in the target cell, CSI feedback in a physical uplink shared channel scheduled by the MAC-CE that includes the handover command; to track the TRS in the target cell on a CSI reference signal resource for tracking signaled by the MAC-CE that includes the handover command explicitly after handover to the target cell; to track the TRS in the target cell on an only CSI reference signal resource for tracking configured in the target cell after handover to the target cell; to: measure a channel from an aperiodic CSI reference signal resource; and transmit, to a second network entity in the target cell, CSI feedback following an only CSI-AperiodicTriggerState configured in the target cell; where T_g is a gap to allow the apparatus to switch to a new TCI state in the target cell, k is a fixed value, μ is a subcarrier spacing of a carrier wherein the apparatus transmitted to the first network entity an acknowledgment of the handover command, is a time of k subframes in μ, and the apparatus is handed over to the target cell after

For example, the processor 604 may support wireless communication at the device 602 in accordance with examples as disclosed herein. Processor 604 may be configured as or otherwise support a means for receiving, from a first network entity, a MAC-CE that includes a handover command for handover of a UE from a serving cell to a target cell with a different PCI; and performing, in response to the handover command, an aperiodic CSI process in the target cell or track, in response to the handover command, a TRS in the target cell.

Additionally or alternatively, the processor 604 may be configured to or otherwise support: where an apparatus implementing the method is configured with CSI reference signal resources for channel measurement with PCIs different from the PCI of the serving cell; where an apparatus implementing the method is configured with aperiodic CSI trigger states in cells with PCIs different from the PCI of the serving cell; where an apparatus implementing the method is configured with TRS in cells with PCIs different from the PCI of the serving cell; measuring a channel from an aperiodic CSI reference signal resource in the target cell following a CSI-AperiodicTriggerState signaled by the handover command explicitly; measuring a channel from an aperiodic CSI reference signal resource in the target cell following an only CSI-AperiodicTriggerState configured in the target cell; transmitting, to a second network entity in the target cell, CSI feedback in a physical uplink shared channel scheduled by the MAC-CE that includes the handover command; tracking the TRS in the target cell on a CSI reference signal resource for tracking signaled by the MAC-CE that includes the handover command explicitly after handover to the target cell; tracking the TRS in the target cell on an only CSI reference signal resource for tracking configured in the target cell after handover to the target cell; measuring a channel from an aperiodic CSI reference signal resource; and transmitting, to a second network entity in the target cell, CSI feedback following an only CSI-AperiodicTriggerState configured in the target cell; where T_g is a gap to allow an apparatus implementing the method to switch to a new TCI state in the target cell, k is a fixed value, μis a subcarrier spacing of a carrier wherein the apparatus transmitted to the first network entity an acknowledgment of the handover command, is a time of k subframes in μ, and the apparatus is handed over to the target cell afterwhere the method is implemented in a UE and the first network entity comprises a base station.

The processor 604 may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) . In some implementations, the processor 604 may be configured to operate a memory array using a memory controller. In some other implementations, a memory controller may be integrated into the processor 604. The processor 604 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 606) to cause the device 602 to perform various functions of the present disclosure.

The memory 606 may include random access memory (RAM) and read-only memory (ROM) . The memory 606 may store computer-readable, computer-executable code including instructions that, when executed by the processor 604 cause the device 602 to perform various functions described herein. The code may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. In some implementations, the code may not be directly executable by the processor 604 but may cause a computer (e.g., when compiled and executed) to perform functions described herein. In some implementations, the memory 606 may include, among other things, a basic I/O system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The I/O controller 610 may manage input and output signals for the device 602. The I/O controller 610 may also manage peripherals not integrated into the device 602. In some implementations, the I/O controller 610 may represent a physical connection or port to an external peripheral. In some implementations, the I/O controller 610 may utilize an operating system such as or another known operating system. In some implementations, the I/O controller 610 may be implemented as part of a processor, such as the processor 604. In some implementations, a user may interact with the device 602 via the I/O controller 610 or via hardware components controlled by the I/O controller 610.

In some implementations, the device 602 may include a single antenna 612. However, in some other implementations, the device 602 may have more than one antenna 612 (i.e., multiple antennas) , including multiple antenna panels or antenna arrays, which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver 608 may communicate bi-directionally, via the one or more antennas 612, wired, or wireless links as described herein. For example, the transceiver 608 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 608 may also include a modem to modulate the packets, to provide the modulated packets to one or more antennas 612 for transmission, and to demodulate packets received from the one or more antennas 612.

FIG. 7 illustrates a flowchart of a method 700 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The operations of the method 700 may be implemented by a device or its components as described herein. For example, the operations of the method 700 may be performed by a network entity 102 as described with reference to FIGs. 1 through 6. In some implementations, the device may execute a set of instructions to control the function elements of the device to perform the described functions. Additionally, or alternatively, the device may perform aspects of the described functions using special-purpose hardware.

At 705, the method may include generating a MAC-CE that includes a handover command to hand over a UE from a serving cell to a target cell with a different PCI, wherein the handover command includes a trigger indicating to the UE to perform one or both of an aperiodic CSI process in the target cell or track a TRS in the target cell. The operations of 705 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 705 may be performed by a device as described with reference to FIG. 1.

At 710, the method may include transmitting, to the UE, the MAC-CE. The operations of 710 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 710 may be performed by a device as described with reference to FIG. 1.

FIG. 8 illustrates a flowchart of a method 800 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The operations of the method 800 may be implemented by a device or its components as described herein. For example, the operations of the method 800 may be performed by a network entity 102 as described with reference to FIGs. 1 through 6. In some implementations, the device may execute a set of instructions to control the function elements of the device to perform the described functions. Additionally, or alternatively, the device may perform aspects of the described functions using special-purpose hardware.

At 805, the method may include the MAC-CE including the handover command also including a scheduling information of a physical uplink shared channel in the target cell for the UE to send aperiodic CSI feedback. The operations of 805 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 805 may be performed by a device as described with reference to FIG. 1.

FIG. 9 illustrates a flowchart of a method 900 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The operations of the method 900 may be implemented by a device or its components as described herein. For example, the operations of the method 900 may be performed by a network entity 102 as described with reference to FIGs. 1 through 6. In some implementations, the device may execute a set of instructions to control the function elements of the device to perform the described functions. Additionally, or alternatively, the device may perform aspects of the described functions using special-purpose hardware.

At 905, the method may include the MAC-CE including the handover command also including scheduling information of a physical uplink shared channel in the target cell for CSI feedback, the scheduling information including at least a time and a frequency resource. The operations of 905 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 905 may be performed by a device as described with reference to FIG. 1.

FIG. 10 illustrates a flowchart of a method 1000 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The operations of the method 1000 may be implemented by a device or its components as described herein. For example, the operations of the method 1000 may be performed by a UE 104 as described with reference to FIGs. 1 through 6. In some implementations, the device may execute a set of instructions to control the function elements of the device to perform the described functions. Additionally, or alternatively, the device may perform aspects of the described functions using special-purpose hardware.

At 1005, the method may include receiving, from a first network entity, a MAC-CE that includes a handover command for handover of a UE from a serving cell to a target cell with a different PCI. The operations of 1005 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1005 may be performed by a device as described with reference to FIG. 1.

At 1010, the method may include performing, in response to the handover command, an aperiodic CSI process in the target cell or track, in response to the handover command, a TRS in the target cell. The operations of 1010 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1010 may be performed by a device as described with reference to FIG. 1.

FIG. 11 illustrates a flowchart of a method 1100 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The operations of the method 1100 may be implemented by a device or its components as described herein. For example, the operations of the method 1100 may be performed by a UE 104 as described with reference to FIGs. 1 through 6. In some implementations, the device may execute a set of instructions to control the function elements of the device to perform the described functions. Additionally, or alternatively, the device may perform aspects of the described functions using special-purpose hardware.

At 1105, the method may include tracking the TRS in the target cell on a CSI reference signal resource for tracking signaled by the MAC-CE that includes the handover command explicitly after handover to the target cell. The operations of 1105 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1105 may be performed by a device as described with reference to FIG. 1.

FIG. 12 illustrates a flowchart of a method 1200 that supports user equipment handover in a wireless network using a MAC-CE in accordance with aspects of the present disclosure. The operations of the method 1200 may be implemented by a device or its components as described herein. For example, the operations of the method 1200 may be performed by a UE 104 as described with reference to FIGs. 1 through 6. In some implementations, the device may execute a set of instructions to control the function elements of the device to perform the described functions. Additionally, or alternatively, the device may perform aspects of the described functions using special-purpose hardware.

At 1205, the method may include measuring a channel from an aperiodic CSI reference signal resource. The operations of 1205 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1205 may be performed by a device as described with reference to FIG. 1.

At 1210, the method may include transmitting, to a second network entity in the target cell, CSI feedback following an only CSI-AperiodicTriggerState configured in the target cell. The operations of 1210 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1210 may be performed by a device as described with reference to FIG. 1.

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

The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable ROM (EEPROM) , flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that may be used to carry or store desired program code means in the form of instructions or data structures and that may be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

Any connection may be properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of computer-readable medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

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

The terms “transmitting, ” “receiving, ” or “communicating, ” when referring to a network entity, may refer to any portion of a network entity (e.g., a base station, a CU, a DU, a RU) of a RAN communicating with another device (e.g., directly or via one or more other network entities) .

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

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

Claims

An apparatus for wireless communication, comprising:

a processor; and

a memory coupled with the processor, the processor configured to cause the apparatus to:

generate a medium access control control element (MAC-CE) that includes a handover command to hand over a user equipment (UE) from a serving cell to a target cell with a different physical cell identifier (PCI) , wherein the handover command includes a trigger indicating to the UE to perform one or both of an aperiodic channel state information (CSI) process in the target cell or track a tracking reference signal (TRS) in the target cell;

transmit, to the UE, the MAC-CE.
The apparatus of claim 1, wherein the processor is further configured to transmit, to the UE, radio resource control (RRC) signaling indicating CSI reference signal resources for channel measurement with PCIs different from the PCI of the serving cell.
The apparatus of claim 1, wherein the processor is further configured to transmit, to the UE, radio resource control (RRC) signaling indicating aperiodic CSI trigger state in cells with PCIs different from the PCI of the serving cell.
The apparatus of claim 1, wherein the processor is further configured to transmit, to the UE, radio resource control (RRC) signaling indicating CSI-RS resources for TRS in cells with PCIs different from the PCI of the serving cell.
The apparatus of claim 1, wherein the handover command including a trigger indicating to perform an aperiodic CSI process in the target cell indicates a CSI-AperiodicTriggerState explicitly.
The apparatus of claim 1, wherein the handover command including a trigger indicating to perform an aperiodic CSI process in the target cell indicates an only CSI-AperiodicTriggerState in the target cell implicitly.
The apparatus of claim 1, wherein the MAC-CE including the handover command also includes a scheduling information of a physical uplink shared channel in the target cell for the UE to send aperiodic CSI feedback.
The apparatus of claim 7, wherein the scheduling information in the MAC-CE follows a random-access response uplink grant in a random-access procedure.
The apparatus of claim 1, wherein the handover command including a trigger indicating to track the TRS in the target cell indicates a TRS resource explicitly.
The apparatus of claim 1, wherein the handover command including a trigger indicating to track the TRS in the target cell indicates an only TRS resource configured in the target cell implicitly.
The apparatus of claim 1, wherein the MAC-CE including the handover command also includes scheduling information of a physical uplink shared channel in the target cell for CSI feedback, the scheduling information including at least a time and a frequency resource.
The apparatus of claim 1, wherein the processor is further configured to cause the apparatus to coordinate with the target cell through centralized units and distributed units of the apparatus and a network entity in the target cell.
An apparatus for wireless communication, comprising:

a processor; and

a memory coupled with the processor, the processor configured to cause the apparatus to:

receive, from a first network entity, a medium access control control element (MAC-CE) that includes a handover command for handover of a user equipment (UE) from a serving cell to a target cell with a different physical cell identifier (PCI) ;

perform, in response to the handover command, an aperiodic channel state information (CSI) process in the target cell or track, in response to the handover command, a tracking reference signal (TRS) in the target cell.
The apparatus of claim 13, wherein the apparatus is configured with CSI reference signal resources for channel measurement with PCIs different from the PCI of the serving cell.
The apparatus of claim 13, wherein the apparatus is configured with aperiodic CSI trigger states in cells with PCIs different from the PCI of the serving cell.
The apparatus of claim 13, wherein the apparatus is configured with TRS in cells with PCIs different from the PCI of the serving cell.
The apparatus of claim 13, wherein the processor is further configured to cause the apparatus to measure a channel from an aperiodic CSI reference signal resource in the target cell following a CSI-AperiodicTriggerState signaled by the handover command explicitly.
The apparatus of claim 13, wherein the processor is further configured to cause the apparatus to measure a channel from an aperiodic CSI reference signal resource in the target cell following an only CSI-AperiodicTriggerState configured in the target cell.
The apparatus of claim 13, wherein the processor is further configured to cause the apparatus to transmit, to a second network entity in the target cell, CSI feedback in a physical uplink shared channel scheduled by the MAC-CE that includes the handover command.
The apparatus of claim 13, wherein the processor is further configured to cause the apparatus to track the TRS in the target cell on a CSI reference signal resource for tracking signaled by the MAC-CE that includes the handover command explicitly after handover to the target cell.
The apparatus of claim 13, wherein the processor is further configured to cause the apparatus to track the TRS in the target cell on an only CSI reference signal resource for tracking configured in the target cell after handover to the target cell.
The apparatus of claim 13, wherein the processor is further configured to cause the apparatus to:

measure a channel from an aperiodic CSI reference signal resource; and

transmit, to a second network entity in the target cell, CSI feedback following an only CSI-AperiodicTriggerState configured in the target cell.
The apparatus of claim 13, wherein T_g is a gap to allow the apparatus to switch to a new TCI state in the target cell, k is a fixed value, μ is a subcarrier spacing of a carrier wherein the apparatus transmitted to the first network entity an acknowledgment of the handover command, is a time of k subframes in μ, and the apparatus is handed over to the target cell after
The apparatus of claim 13, wherein the apparatus comprises a user equipment (UE) and the first network entity comprises a base station.
A method, comprising:

generating a medium access control control element (MAC-CE) that includes a handover command to hand over a user equipment (UE) from a serving cell to a target cell with a different physical cell identifier (PCI) , wherein the handover command includes a trigger indicating to the UE to perform one or both of an aperiodic channel state information (CSI) process in the target cell or track a tracking reference signal (TRS) in the target cell; and

transmitting, to the UE, the MAC-CE.
The method of claim 25, further comprising transmitting, to the UE, radio resource control (RRC) signaling indicating CSI reference signal resources for channel measurement with PCIs different from the PCI of the serving cell.
The method of claim 25, further comprising transmitting, to the UE, radio resource control (RRC) signaling indicating aperiodic CSI trigger state in cells with PCIs different from the PCI of the serving cell.
The method of claim 25, further comprising transmitting, to the UE, radio resource control (RRC) signaling indicating CSI-RS resources for TRS in cells with PCIs different from the PCI of the serving cell.
The method of claim 25, wherein the handover command including a trigger indicating to perform an aperiodic CSI process in the target cell indicates a CSI-AperiodicTriggerState explicitly.
The method of claim 25, wherein the handover command including a trigger indicating to perform an aperiodic CSI process in the target cell indicates an only CSI-AperiodicTriggerState in the target cell implicitly.
The method of claim 25, wherein the MAC-CE including the handover command also includes a scheduling information of a physical uplink shared channel in the target cell for the UE to send aperiodic CSI feedback.
The method of claim 31, wherein the scheduling information in the MAC-CE follows a random-access response uplink grant in a random-access procedure.
The method of claim 25, wherein the handover command including a trigger indicating to track the TRS in the target cell indicates a TRS resource explicitly.
The method of claim 25, wherein the handover command including a trigger indicating to track the TRS in the target cell indicates an only TRS resource configured in the target cell implicitly.
The method of claim 25, wherein the MAC-CE including the handover command also includes scheduling information of a physical uplink shared channel in the target cell for CSI feedback, the scheduling information including at least a time and a frequency resource.
The method of claim 25, further comprising coordinating with the target cell through centralized units and distributed units of an apparatus implementing the method and a network entity in the target cell.