WO2024075095A1 - Timing alignment acquisition - Google Patents

Abstract

Various aspects of the present disclosure relate to methods, apparatuses, and systems that support timing alignment acquisition. For instance, implementations provide for an optimized RACH procedure performed for the purpose of early acquisition of timing alignment (TA) information, e.g., before a handover occurs. Further, implementations enable a candidate cell for a handover to identify a random access procedure as an early TA acquisition RACH, which can enable successful performance of the RACH procedure without establishing an radio resource control (RRC) connection in the candidate cell.

Description

TIMING ALIGNMENT ACQUISITION

RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application Serial No. 63/421,800 filed 02-NOV-2022 entitled “TIMING ALIGNMENT ACQUISITION,” the disclosure of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates to wireless communications, and more specifically to managing connectivity in wireless communications.

BACKGROUND

[0003] 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 nextgeneration 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)).

[0004] Some wireless communications systems provide ways for enabling a UE to perform a handover between different cells. Current handover implementations, however, may not be efficient and may result in latency. SUMMARY

[0005] The present disclosure relates to methods, apparatuses, and systems that support timing alignment (TA) acquisition. For instance, implementations provide for an optimized Random Access Channel (RACH) procedure performed for the purpose of early acquisition of TA information, e.g., before a handover occurs. Further, implementations enable a candidate cell for a handover to identify a random access procedure as an early TA acquisition RACH, which can enable successful performance of the RACH procedure without establishing a Radio Resource Control (RRC) connection in the candidate cell.

[0006] Thus, the described techniques provide optimized handover processes that decrease latency and signaling overhead that may be experienced in some wireless communications systems.

[0007] Some implementations of the methods and apparatuses described herein may further include receiving a first message including information for a set of cells; initiating, based at least in part on the first message, a random access procedure on at least one cell of the set of cells; and transmitting, to the at least one cell, an uplink signal including a usage information pertaining to the random access procedure.

[0008] Some implementations of the methods and apparatuses described herein may further include: receiving the first message as a downlink message on a physical downlink shared channel (PDSCH); where the downlink message on the PDSCH includes a RRC message; transmitting the uplink signal as a physical random access channel (PRACH) preamble; transmitting the uplink signal as a physical uplink shared channel (PUSCH) transmission scheduled by a random access response message; where the PUSCH transmission includes a medium access control (MAC)- control element (CE), and where the MAC-CE includes an identity.

[0009] Some implementations of the methods and apparatuses described herein may further include: where the PUSCH transmission includes a RRC message, and where the RRC message includes a field identifying the usage information; where the random access procedure includes a contention-based random access procedure; further including triggering the random access procedure via a MAC entity; where the usage information includes an indication of timing alignment acquisition, further including receiving, based at least in part on the uplink signal, timing alignment information; receiving an indication of whether the at least one cell of the set of cells supports earlier timing alignment acquisition; determining priority information for the set of cells, and initiating the random access procedure based at least in part on the priority information; receiving, within the first message, an indication of whether the at least one cell supports early timing alignment acquisition, and based at least in part on the indication, transmitting the uplink signal to a candidate cell for obtaining timing alignment information.

[0010] Some implementations of the methods and apparatuses described herein may further include: generating a first message including information for a set of cells, the information including information pertaining to obtaining timing alignment information from one or more cells of the set of cells; and transmitting the first message to a UE.

[0011] Some implementations of the methods and apparatuses described herein may further include: where the information for the set of cells includes an indication whether one or more cells of the set of cells support early acquisition of timing alignment; where the first message further includes a priority indication for timing alignment with the set of cells; transmitting the priority indication in an order that corresponds to a priority order for obtaining timing alignment information for the one or more cells of the set of cells.

[0012] Some implementations of the methods and apparatuses described herein may further include: receiving, at an apparatus and from a UE, a first message including information pertaining to obtaining first timing alignment information; and transmitting, to the UE, a second message including second timing alignment information.

[0013] Some implementations of the methods and apparatuses described herein may further include: where the second timing alignment information includes an indication of whether the apparatus supports early timing alignment acquisition; transmitting the second message via a system information block (SIB).

[0014] Some implementations of the methods and apparatuses described herein may further include receiving a first message including an instruction to perform a RACH procedure for obtaining timing alignment information from one or more cells of a set of cells; and initiating the RACH procedure with the one or more cells of the set of cells.

[0015] Some implementations of the methods and apparatuses described herein may further include where the first message includes downlink control information (DCI) including one or more identities for the one or more cells of the set of cells; the DCI is received as part of physical downlink control channel (PDCCH); the first message includes one or more of a synchronization signal block (SSB), physical broadcast channel (PBCH), or a RACH mask index for the one or more cells for the set of cells; including initiating the RACH procedure using the one or more of the SSB, the PBCH, or the RACH mask index; including receiving, before the first message, a second message including candidate cell information identifying candidate cells, the candidate cells including at least the one or more cells of the set of cells; the first message includes downlink control information (DCI) including one or more references to the one or more cells of the set of cells from the candidate cells of the second message; the DCI identifies the one or more candidate cells of the set of cells based at least in part on an order of the one or more cells of the set of cells in the candidate cell information; acquiring timing alignment information from a target cell of the one or more cells of the set of cells; and starting monitoring physical downlink control channel (PDCCH) in the target cell; starting monitoring PDCCH based at least in part on reception of one or more of a layer 1 (LI) handover command or a layer 2 (L2) handover command; receiving scheduling of uplink resources from the target cell via a dynamic uplink grant; transmitting, via one or more of the uplink resources, a third message indicating completion of a handover to the target cell.

[0016] Some implementations of the methods and apparatuses described herein may further include generating a first message instructing a UE to perform a RACH procedure for obtaining timing alignment information from one or more cells of a set of cells; and transmitting the first message to the UE.

[0017] Some implementations of the methods and apparatuses described herein may further include where the first message includes downlink control information (DCI) including one or more identities for the one or more cells of the set of cells; the DCI is transmitted as part of physical downlink control channel (PDCCH); the first message includes one or more of a synchronization signal block (SSB), physical broadcast channel (PBCH), or a RACH mask index for the one or more cells for the set of cells; transmitting, before the first message, a second message including candidate cell information identifying candidate cells, the candidate cells including at least the one or more cells of the set of cells; the first message includes downlink control information (DCI) including one or more references to the one or more cells of the set of cells from the candidate cells of the second message; the DCI identifies the one or more candidate cells of the set of cells based at least in part on an order of the one or more cells of the set of cells in the candidate cell information.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 illustrates an example of a wireless communications system that supports timing alignment acquisition in accordance with aspects of the present disclosure.

[0019] FIG. 2 illustrates a system 200 for inter-gNB handover procedures.

[0020] FIG. 3 illustrates a system 300 for intra- AMF and UPF handover.

[0021] FIG. 4 illustrates an example of an RRC message 400 that supports timing alignment acquisition in accordance with aspects of the present disclosure.

[0022] FIG. 5 illustrates an example of system 500 that supports timing alignment acquisition in accordance with aspects of the present disclosure.

[0023] FIG. 6 illustrates an example of a block diagram 600 of a device 602 (e.g., an apparatus) that supports timing alignment acquisition in accordance with aspects of the present disclosure.

[0024] FIG. 7 illustrates an example of a block diagram 700 of a device 702 (e.g., an apparatus) that supports timing alignment acquisition in accordance with aspects of the present disclosure.

[0025] FIG. 8 illustrates a flowchart of a method 800 that supports timing alignment acquisition in accordance with aspects of the present disclosure.

[0026] FIG. 9 illustrates a flowchart of a method 900 that supports timing alignment acquisition in accordance with aspects of the present disclosure.

[0027] FIG. 10 illustrates a flowchart of a method 1000 that supports timing alignment acquisition in accordance with aspects of the present disclosure.

[0028] FIG. 11 illustrates a flowchart of a method 1100 that supports timing alignment acquisition in accordance with aspects of the present disclosure.

[0029] FIG. 12 illustrates a flowchart of a method 1200 that supports timing alignment acquisition in accordance with aspects of the present disclosure. DETAILED DESCRIPTION

[0030] In wireless communications systems, when a UE moves from the coverage area of one cell (e.g., Secondary Cell Group (SCG)) to another cell, a serving cell change may be performed, e.g., where a current serving cell does not remain a radio viable option. In some implementations, a serving cell change of a UE is triggered by layer 3 (L3) measurements and is implemented via RRC signaling-triggered reconfiguration with synchronization for a change of Primary Cell (PCell) and Primary Secondary Cell (PSCell), as well as release add for Secondary Cells (SCells) when applicable. Such scenarios may involve complete layer 2 (L2) and layer 1 (LI) resets, leading to longer latency, larger overhead, and longer interruption time than beam switch mobility.

Accordingly, in order to attempt to reduce the handover latency (e.g., avoid performing a RACH procedure after a handover command has been received), a UE may perform a random access procedure on a candidate cell before a handover to the candidate targe cell occurs in order to acquire early TA information. However, the current RACH procedure performed at handover has been designed in order to move the RRC connection to the candidate target cell (e.g. synchronizing to the target cell and sending RRCReconfiguration Complete message to the target cell), which may also introduce latency and increased signaling overhead into a handover process.

[0031] Accordingly, this disclosure provides for techniques that support timing alignment acquisition. For instance, implementations provide for an optimized RACH procedure performed for the purpose of early acquisition of TA information, e.g., before a handover occurs. Further, implementations enable a candidate cell for a handover to identify a random access procedure as an early TA acquisition RACH, which can enable successful performance of the RACH procedure without establishing an RRC connection in the candidate cell.

[0032] More specifically, in implementations the message 3 of a contention-based random access procedure performed for the purpose of early TA acquisition includes a new RRC message. The new RRC message, for example, is used for contention resolution and to notify a network that the RACH is being performed for early TA acquisition. In at least one example, the new RRC message includes at least a portion of a UE identity (e.g. 5G-S-TMSI) (5G-S-Temporary Mobile Subscription Identifier), such as to uniquely identify the UE and resolve a potential contention. [0033] Further, in implementations a UE includes a new MAC CE within the RACH msg3 of an early TA acquisition RACH procedure which can be used to identify the RACH procedure as an early TA acquisition RACH procedure and which can also be used for contention resolution. In at least one example, the new MAC CE includes a UE identity. The UE identity, for instance, can be a random value or part of the 5G-S-TMSI. Further, the MAC CE can be identified by a new reserved logical channel ID.

[0034] Thus, the described techniques provide optimized handover processes that decrease latency and signaling overhead that may be experienced in some wireless communications systems.

[0035] 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.

[0036] FIG. 1 illustrates an example of a wireless communications system 100 that supports timing alignment acquisition 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 LIE- 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.

[0037] 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 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.

[0038] 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.

[0039] 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 (loT) device, an Internet-of-Everything (loE) 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.

[0040] 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.

[0041] A UE 104 may also be able to support wireless communication directly with other UEs 104 over a communication link 114. For example, a UE 104 may support wireless communication directly with another UE 104 over a device-to-device (D2D) communication link. In some implementations, such as vehicle-to-vehicle (V2V) deployments, V2X deployments, or cellular- V2X deployments, the communication link 114 may be referred to as a sidelink. For example, a UE 104 may support wireless communication directly with another UE 104 over a PC5 interface.

[0042] 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 SI, N2, N2, or another network interface). The network entities 102 may communicate with each other over the backhaul links 116 (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 or 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).

[0043] 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-real time (RT) RIC), a Non-Real Time RIC (Non-RT RIC)), a Service Management and Orchestration (SMO) system, or any combination thereof.

[0044] 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)).

[0045] 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., 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 (LI) (e.g., physical (PHY) layer) or an L2 (e.g., radio link control (RLC) layer, MAC layer) functionality and signaling, and may each be at least partially controlled by the CU.

[0046] 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). [0047] 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., Fl, Fl-c, Fl-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.

[0048] 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), or a user plane function (UPF)). 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.

[0049] The core network 106 may communicate with the packet data network 108 over one or more backhaul links 116 (e.g., via an SI, N2, N2, or another network interface). The packet data network 108 may include an application server 118. In some implementations, one or more UEs 104 may communicate with the application server 118. 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 118 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).

[0050] 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 (e.g., multiple frame structures). The network entities 102 and the UEs 104 may support various frame structures based on one or more numerologies.

[0051] 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., /r=0) may be associated with a first subcarrier spacing (e.g., 15 kHz) and a normal cyclic prefix. The first numerology (e.g., /r=0) associated with the first subcarrier spacing (e.g., 15 kHz) may utilize one slot per subframe. A second numerology (e.g., /2=1) may be associated with a second subcarrier spacing (e.g., 30 kHz) and a normal cyclic prefix. A third numerology (e.g., /r=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., jU=3) may be associated with a fourth subcarrier spacing (e.g., 120 kHz) and a normal cyclic prefix. A fifth numerology (e.g., /r=4) may be associated with a fifth subcarrier spacing (e.g., 240 kHz) and a normal cyclic prefix.

[0052] 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.

[0053] 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., /r=0) associated with a first subcarrier spacing (e.g., 15 kHz) may be used interchangeably between subframes and slots.

[0054] 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.

[0055] 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., ^=0), which includes 15 kHz subcarrier spacing; a second numerology (e.g., /z=l ), which includes 30 kHz subcarrier spacing; and a third numerology (e.g., /r=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., /r=2), which includes 60 kHz subcarrier spacing; and a fourth numerology (e.g., /r=3), which includes 120 kHz subcarrier spacing.

[0056] According to implementations for timing alignment acquisition, a network entity 102a determines that a UE 104 is to implement a handover to a different cell and transmits a cell information message 120 to the UE 104. The cell information message 120, for instance, includes cell information for different candidate cells for the handover, including information for a cell associated with a network entity 102b. Accordingly, the UE 104 receives the cell information message 120 and based at least in part on the cell information message 120, the UE 104 initiates a random access procedure 122 for performing a handover to the network entity 102b. As part of the random access procedure 122 the UE 104 transmits a usage information message 124 to the network entity 102b. In at least one implementation the usage information message 124 includes an indication to receive early (e.g., prior to handover) TA information from the network entity 102b. Accordingly, the UE 104 can receive early TA information from the network entity 102b and can engage in a handover from the network entity 102a to the network entity 102b.

[0057] In some wireless communications systems, conditional PSCell change

(CPC)/ Conditional PSCell addition (CPA), a CPC/CPA-configured UE is to release the CPC/CPA configurations when completing random access towards a target PSCell. Thus the UE may not have an opportunity to perform subsequent CPC/CPA without prior CPC/CPA reconfiguration and reinitialization from the network. This may increase a delay for the cell change and increase the signaling overhead, such as in the case of frequent SCG changes when operating FR2. Therefore, multi-RAT (MR)-dual connectivity (DC)(MR-DC) with selective activation of cell groups aims at enabling subsequent CPC/CPA after SCG change, without reconfiguration and re- initialization on the CPC/CPA preparation from the network. This may result in a reduction of the signaling overhead and interrupting time for SCG change.

[0058] Currently, conditional handover (CHO) and MR-DC cannot be configured simultaneously. This limits the usefulness of these two features when MR-DC is configured. However, this alone may not be sufficient to optimize MR-DC mobility, as the radio link quality of the conditionally-configured PSCell may not be sufficient or may not be the best candidate PSCell when the UE accesses the target PCell, and this may impact the UE throughput. To mitigate this throughput impact, some implementations for CHO+MRDC can consider CHO including target master cell group (MCG) and multiple candidate SCGs for CPC/CPA.

[0059] Further to some wireless communications systems, network-controlled mobility can apply to UEs in an RRC CONNECTED state and can be categorized into two types of mobility: cell level mobility and beam level mobility. Beam level mobility can include intra-cell beam level mobility and inter-cell beam level mobility.

[0060] FIG. 2 illustrates a system 200 for inter-gNB handover procedures. In different scenarios, cell level mobility involves triggering of explicit RRC signaling, e.g., for handover. For inter-gNB handover, the signaling procedures may consist of at least the elemental components illustrated in the system 200, as described below:

1. The source gNB initiates handover and issues a HANDOVER REQUEST over the Xn interface.

2. The target gNB performs admission control and provides the new RRC configuration as part of the HANDOVER REQUEST ACKNOWLEDGE.

3. The source gNB provides the RRC configuration to the UE by forwarding the RRCReconfiguration message received in the HANDOVER REQUEST ACKNOWLEDGE. The RRCReconfiguration message includes at least cell identifier (ID) and information required to access the target cell so that the UE can access the target cell without reading system information. For some cases, the information required for contention-based and contention-free random access can be included in the RRCReconfiguration message. The access information to the target cell may include beam specific information, if any.

4. The UE moves the RRC connection to the target gNB and replies with the RRCReconfigurationComplete . In implementations, user data can also be sent in step 4 if the grant allows.

[0061] In scenarios for dual active protocol stack (DAPS) handover, the UE can continue the downlink user data reception from the source gNB until releasing the source cell and can continue the uplink user data transmission to the source gNB until successful random-access procedure to the target gNB. Further, source and target PCell can be used during DAPS handover. Carrier aggregation (CA), DC, Supplementary Uplink (SUL), multi-TRP, ethernet header compression (EHC), CHO, Unified Data Convergence (UDC), NR sidelink configurations and V2X sidelink configurations can be released by the source gNB before the handover command is sent to the UE and may not be configured by the target gNB until the DAPS handover has completed, e.g., at earliest in the same message that releases the source PCell.

[0062] The handover mechanism triggered by RRC may involve the UE to at least reset the MAC entity and re-establish RLC, except for DAPS handover, where upon reception of the handover command, the UE can: - Create a MAC entity for target;

- Establish the RLC entity and an associated dedicated traffic channel (DTCH) logical channel for target for each data radio bearer (DRB) configured with DAPS;

- For each DRB configured with DAPS, reconfigure the PDCP entity with separate security and Robust Header Compression (ROHC) functions for source and target and associates them with the RLC entities configured by source and target respectively;

- Retain the rest of the source configurations until release of the source.

[0063] In some wireless communications systems, RRC managed handovers with and without PDCP entity re-establishment can both be supported. For DRBs using RLC acknowledged mode (AM) mode, PDCP can either be re-established together with a security key change or initiate a data recovery procedure without a key change. For DRBs using RLC Unacknowledged Mode (UM) mode, PDCP can either be re-established together with a security key change or remain as it is without a key change. For SRBs, PDCP can either remain as it is, discard its stored PDCP PDUs/SDUs without a key change or be re-established together with a security key change.

[0064] Data forwarding, in-sequence delivery and duplication avoidance at handover, can be successful when the target gNB uses the same DRB configuration as the source gNB. Timer based handover failure procedure can be supported in NR. RRC connection re-establishment procedure can be used for recovering from handover failure except in certain CHO or DAPS handover scenarios:

- When DAPS handover fails, the UE can fall back to the source cell configuration, resume the connection with the source cell, and report DAPS handover failure via the source without triggering RRC connection re-establishment if the source link has not been released.

- When initial CHO execution attempt fails or handover fails, the UE can perform cell selection, and if the selected cell is a CHO candidate and if network configured the UE to try CHO after handover/CHO failure, then the UE can attempt CHO execution once, otherwise re-establishment can be performed.

[0065] In some scenarios the handover of the Integrated Access and Backhaul (lAB)-mobile terminated (MT) in standalone mode follows the same procedure as described for the UE. After the backhaul has been established, the handover of the IAB-MT is part of an intra-CU topology adaptation procedure. Modifications to the configuration of backhaul adaption protocol (BAP) sublayer and higher protocol layers above the BAP sublayer can be implemented.

[0066] In some wireless communications scenarios beam level mobility does not require explicit RRC signaling to be triggered. For instance, beam level mobility can be within a cell or between cells, and the latter is referred to as inter-cell beam management (ICBM). For ICBM, a UE can receive or transmit UE dedicated channels/signals via a TRP associated with a Physical Cell Identity (PCI) different from the PCI of a serving cell, while non-UE-dedicated channels/signals may be received via a TRP associated with a PCI of the serving cell. A gNB can provide via RRC signaling the UE with measurement configuration containing configurations of Synchronization Signal/Physical Broadcast Channel (SS/PBCH) block (SSB)/channel state information (CSI) resources and resource sets, reports and trigger states for triggering channel and interference measurements, and reports. In case of ICBM, a measurement configuration can include SSB resources associated with PCIs different from the PCI of a serving cell. Beam level mobility can then be dealt with at lower layers by means of physical layer and MAC layer control signaling, and RRC may not be required to know which beam is being used at a given point in time.

[0067] In scenarios, SSB-based Beam Level Mobility is based on the SSB associated to the initial downlink (DL) bandwidth part (BWP) and can be configured for the initial DL BWPs and for DL BWPs containing the SSB associated to the initial DL BWP. For other DL BWPs, Beam level mobility can be performed based on CSI-reference signal (RS).

[0068] FIG. 3 illustrates a system 300 for intra- AMF and UPF handover. In some scenarios, an intra-NR RAN handover performs the preparation and execution phase of the handover procedure performed without involvement of the 5GC, e.g., preparation messages are directly exchanged between the gNBs. The release of the resources at the source gNB during the handover completion phase can be triggered by the target gNB. The system 300 depicts a handover scenario where neither the AMF nor the UPF changes:

0. The UE context within the source gNB contains information regarding roaming and access restrictions which were provided either at connection establishment or at the last Timing Advance update. 1. The source gNB configures the UE measurement procedures and the UE reports according to the measurement configuration.

2. The source gNB decides to handover the UE, based on MeasurementReport and Radio Resource Management (RRM) information.

3. The source gNB issues a Handover Request message to the target gNB passing a transparent RRC container with necessary information to prepare the handover at the target side. The information includes at least the target cell ID, KgNB*, the Cell Radio Network Temporary Identifier (C-RNTI) of the UE in the source gNB, RRM-configuration including UE inactive time, basic access stratum (AS)-configuration including antenna Info and DL Carrier Frequency, the current QoS flow to DRB mapping rules applied to the UE, the SIB1 from source gNB, the UE capabilities for different RATs, PDU session related information, and can include the UE reported measurement information including beam-related information if available. The PDU session related information includes the slice information and QoS flow level QoS profile(s). The source gNB may also request a DAPS handover for one or more DRBs. In some scenarios, after issuing a Handover Request, the source gNB is not to reconfigure the UE, including performing Reflective QoS flow to DRB mapping.

4. Admission Control may be performed by the target gNB. Slice-aware admission control can be performed if the slice information is sent to the target gNB. If the PDU sessions are associated with non-supported slices the target gNB can reject such PDU Sessions.

5. The target gNB prepares the handover with L1/L2 and sends the HANDOVER REQUEST ACKNOWLEDGE to the source gNB, which includes a transparent container to be sent to the UE as an RRC message to perform the handover. The target gNB also indicates if a DAPS handover is accepted.

NOTE 2: As soon as the source gNB receives the HANDOVER REQUEST

ACKNOWLEDGE, or as soon as the transmission of the handover command is initiated in the downlink, data forwarding may be initiated.

NOTE 3: For DRBs configured with DAPS, downlink PDCP SDUs are forwarded with Sequence Number (SN) assigned by the source gNB, until SN assignment is handed over to the target gNB in step 8b, for which the normal data forwarding follows specified procedures.

6. The source gNB triggers the Uu handover by sending an RRCReconfiguration message to the UE, containing the information used to access the target cell: at least the target cell ID, the new C-RNTI, and the target gNB security algorithm identifiers for the selected security algorithms. It can also include a set of dedicated RACH resources, the association between RACH resources and SSB(s), the association between RACH resources and UE-specific CSI-RS configuration(s), common RACH resources, and system information of the target cell, etc.

NOTE 4: For DRBs configured with DAPS, the source gNB may not stop transmitting downlink packets until it receives the HANDOVER SUCCESS message from the target gNB in step 8a.

NOTE 4a: CHO may not be configured simultaneously with DAPS handover.

7a. For DRBs configured with DAPS, the source gNB sends the EARLY STATUS TRANSFER message. The DL COUNT value conveyed in the EARLY STATUS TRANSFER message indicates PDCP SN and hyper frame number (HFN) of the first PDCP Service Data Unit (SDU) that the source gNB forwards to the target gNB. The source gNB does not stop assigning SNs to downlink PDCP SDUs until it sends the SN STATUS TRANSFER message to the target gNB in step 8b.

7. For DRBs not configured with DAPS, the source gNB sends the SN STATUS TRANSFER message to the target gNB to convey the uplink PDCP SN receiver status and the downlink PDCP SN transmitter status of DRBs for which PDCP status preservation applies (i.e. for RLC AM). The uplink PDCP SN receiver status includes at least the PDCP SN of the first missing uplink (UL) PDCP SDU and may include a bit map of the receive status of the out of sequence UL PDCP SDUs that the UE needs to retransmit in the target cell, if any. The downlink PDCP SN transmitter status indicates the next PDCP SN that the target gNB can assign to new PDCP SDUs, not having a PDCP SN yet.

NOTE 5: In case of DAPS handover, the uplink PDCP SN receiver status and the downlink PDCP SN transmitter status for a DRB with RLC-AM and not configured with DAPS may be transferred by the SN STATUS TRANSFER message in step 8b instead of step 7.

NOTE 6: For DRBs configured with DAPS, the source gNB may additionally send the EARLY STATUS TRANSFER message(s) between step 7 and step 8b, to inform discarding of already forwarded PDCP SDUs. The target gNB may not transmit forwarded downlink PDCP SDUs to the UE, whose COUNT is less than the conveyed DL COUNT value and discards them if transmission has not been attempted already.

8. The UE synchronizes to the target cell and completes the RRC handover procedure by sending RRCReconfigurationComplete message to target gNB. In case of DAPS handover, the UE does not detach from the source cell upon receiving the RRCReconfiguration message. The UE releases the source resources and configurations and stops DL/UL reception/transmission with the source upon receiving an explicit release from the target node.

NOTE 6a: From RAN point of view, the DAPS handover is considered to only be completed after the UE has released the source cell as explicitly requested from the target node. RRC suspend, a subsequent handover or inter-RAT handover cannot be initiated until the source cell has been released.

8a/8b In case of DAPS handover, the target gNB sends the HANDOVER SUCCESS message to the source gNB to inform that the UE has successfully accessed the target cell. In return, the source gNB sends the SN STATUS TRANSFER message for DRBs configured with DAPS for which the description in step 7 applies, and the normal data forwarding follows specified procedures.

NOTE 7: The uplink PDCP SN receiver status and the downlink PDCP SN transmitter status are also conveyed for DRBs with RLC-UM in the SN STATUS TRANSFER message in step 8b, if configured with DAPS.

NOTE 8: For DRBs configured with DAPS, the source gNB does not stop delivering uplink QoS flows to the UPF until it sends the SN STATUS TRANSFER message in step 8b. The target gNB does not forward QoS flows of the uplink PDCP SDUs successfully received in-sequence to the UPF until it receives the SN STATUS TRANSFER message, in which UL HFN and the first missing SN in the uplink PDCP SN receiver status indicates the start of uplink PDCP SDUs to be delivered to the UPF. The target gNB does not deliver any uplink PDCP SDUs which has an UE COUNT lower than the provided.

9. The target gNB sends a PATH SWITCH REQUEST message to AMF to trigger 5GC to switch the DL data path towards the target gNB and to establish an NG-C interface instance towards the target gNB.

10. 5GC switches the DL data path towards the target gNB. The UPF sends one or more "end marker" packets on the old path to the source gNB per PDU session/tunnel and then can release any U-plane/ Transport Network Layer (TNL) resources towards the source gNB.

11. The AMF confirms the PATH SWITCH REQUEST message with the PATH SWITCH REQUEST ACKNOWLEDGE message.

12. Upon reception of the PATH SWITCH REQUEST ACKNOWLEDGE message from the AMF, the target gNB sends the UE CONTEXT RELEASE to inform the source gNB about the success of the handover. The source gNB can then release radio and C-plane related resources associated to the UE context. Any ongoing data forwarding may continue.

[0069] According to scenarios, an RRM configuration can include both beam measurement information (for layer 3 mobility) associated to SSB(s) and CSI-RS(s) for the reported cell(s) if both types of measurements are available. Also, if CA is configured, the RRM configuration can include the list of best cells on each frequency for which measurement information is available. And the RRM measurement information can also include the beam measurement for the listed cells that belong to the target gNB.

[0070] The common RACH configuration for beams in the target cell may only be associated to the SSB(s). The network can have dedicated RACH configurations associated to the SSB(s) and/or have dedicated RACH configurations associated to CSI-RS(s) within a cell. The target gNB can include one of the following RACH configurations in the Handover Command to enable the UE to access the target cell: i) Common RACH configuration; ii) Common RACH configuration + Dedicated RACH configuration associated with SSB; iii) Common RACH configuration + Dedicated RACH configuration associated with CSI- RS.

[0071] In scenarios the dedicated RACH configuration allocates RACH resource(s) together with a quality threshold to use them. When dedicated RACH resources are provided, they can be prioritized by the UE and the UE is not to switch to contention-based RACH resources as long as the quality threshold of those dedicated resources is met. The order to access the dedicated RACH resources can be up to UE implementation.

[0072] Upon receiving a handover command requesting DAPS handover, the UE can suspend source cell SRBs, stop sending and receiving any RRC control plane signaling toward the source cell, and establish SRBs for the target cell. The UE can release the source cell SRBs configuration upon receiving source cell release indication from the target cell after successful DAPS handover execution. When DAPS handover to the target cell fails and if the source cell link is available, then the UE can revert back to the source cell configuration and resume source cell SRBs for control plane signaling transmission.

[0073] In various scenarios (e.g., for L1/L2 mobility), a UE is to maintain a TA for a candidate cell before handover in order to reduce handover latency. For instance, the UE is_to obtain the TA for the candidate cell before receiving the L1/L2 handover command from a source cell. Then, if the UE receives the L1/L2 handover command from the source cell, the UE can perform the handover to the candidate cell without performing the Random Access (RA) procedure to the candidate cell.

[0074] For instance, to avoid performing the RA procedure to the candidate cell after receiving the L1/L2 handover command, the TA for the candidate cell can be obtained before receiving the L1/L2 handover command. One of the options considered is that the UE performs a random access procedure (RACH) on a candidate cell in order to acquire uplink timing related information prior to an actual handover.

[0075] Accordingly, solutions are provided in this disclosure for an optimized RACH procedure performed for the purpose of acquiring an TA information early, e.g., before a handover occurs. [0076] In implementations, a UE triggers a random access procedure (RACH) on a candidate cell in response to the reception of candidate cell information from a source cell (e.g., source gNB). For instance, the candidate cell information is provided in an RRC message to the UE from the source cell, e.g., a current serving gNB. Throughout this disclosure a message which provides a UE with configurations applicable for the candidate cells to which UE may be handed over may be referred to as candidate cell information message, but this is not to be construed as limiting and such messages may be referred to using additional or alternative terminology.

[0077] In at least one example a candidate cell information message includes configuration information for a set of candidate cells. For instance, the RRC layer of the UE triggers and/or initiates a RACH procedure (e.g., instructing the MAC layer to start a random access procedure) in one of the candidate cells for which configuration information was provided in the candidate cell information message for the purpose of acquiring uplink timing synchronization in the candidate cell, e.g., to obtain TA from the candidate cell. A new RACH trigger is introduced (e.g., reception of the candidate cell information) according to implementations.

[0078] In implementations, a UE (e.g., RRC layer of the UE) can trigger a RACH procedure for the purpose of early TA acquisition for each of the candidate cells for which configuration information is provided in the candidate cell information message. The order in which RRC layer can initiate the RACH procedure on the candidate cells can correspond in at least one example to the order in which the candidate cell configuration is signaled from the network. For instance, the UE initiates a RACH procedure first on the candidate cell for which the configuration information is signaled first within the candidate cell information message. In an alternative or additional example the order in which the UE and/or RRC layer initiates the RACH procedures on the candidate cells is according to UE implementation.

[0079] In implementations the candidate cell information message includes one or more signaling fields which indicate for which of the candidate cells the UE is to acquire early uplink timing synchronization by initiating a RACH procedure. For instance, the UE may acquire an early TA only for a subset of the candidate cells for which configurations are provided within the candidate cell information message, e.g., multiple candidate cells may share the same uplink timing such as by belong to the same timing alignment group. In at least one example the configuration information for a candidate cell contains a field and/or signaling indicating whether the UE is to acquire early timing synchronization for the candidate cell. In at least one example, the field may a be a one-bit flag and/or Boolean.

[0080] In implementations a UE uses a random-access preamble from a set of reserved random access preambles when performing a random access procedure for the purpose of early acquisition of uplink timing synchronization on a candidate cell. For instance, implementations include a set of random access preambles and/or PRACH resources reserved and/or configured for early TA acquisition RACH attempts in a candidate cell. The RACH configuration including the set of reserved RACH preambles and/or PRACH resources, for example, is broadcast in system information by the candidate cells. In another alternative or additional example the RACH information for early TA acquisitions is provided within the candidate cell information message to the UE. Using reserved RACH preambles and/or PRACH resources can enable the network to earlier identify the purpose of the RACH procedure based on the received preamble and/or PRACH resource, and may also decrease the probability of a contention and/or collision.

[0081] In implementations the candidate cell information includes information indicating whether a candidate cell supports early TA acquisition. For instance, the configuration information provided for a candidate cell includes information indicating whether a UE is permitted to perform a RACH procedure in the candidate cell for the purpose of early uplink timing synchronization. Alternatively or additionally, a candidate cell may broadcast (e.g., in system information) whether RACH for the purpose of early TA acquisition is supported in a cell.

[0082] In implementations the message 3 of a contention-based random access procedure (e.g., PUSCH scheduled by Random Access Response (RAR)) performed for the purpose of early TA acquisition includes an RRC message. For instance, the RACH message 3 (e.g., UL message scheduled by a Random Access Response message) includes an RRC message which can be used for the purpose of contention resolution and/or to notify the network that the RACH is performed for early TA acquisition. In at least one example the RRC message is a message transmitted on the UL Common Control Channel (CCCH), e.g., UL CCCH SDU(s). In implementations the RRC message may have for example a size of 48bits. In at least one example the RRC message includes at least part of a UE identity (e.g., 5G- -TMSI), such as to uniquely identify the UE and resolve a potential contention. In at least one example a ReestblishmentUE-Identity and/or a shortMAC-I may be included as a UE identity. When a gNB receives the RRC message, the gNB can be aware of the UE identity and the purpose of the RACH attempt (e.g., early TA acquisition) and can react and/or respond accordingly. In an additional or alternative example the RACH msg3 for the early TA acquisition RACH procedure is a RRCSetupRequest message, and in an example implementation an Establishmentcause value (e.g., one of the spare values) can be used in order to identify an early TA acquisition RACH.

[0083] In implementations the message 3 does not contain data of Data radio bearers (DRBs), e.g., user plane data. For instance, only SDU(s) of a SRB can be included in a RACH message 3. In at least one example a logical channel restriction is applied for the message 3 of a RACH procedure initiated for the purpose of early TA acquisition, e.g., SDU(s) of DRBsZLCH(s) are not permitted to be multiplexed in the RACH message 3. In at least one example the UE considers the data radio bearer as suspended when generating the TB for the RACH message 3. In at least one example the UE is not permitted to multiplex a MAC CE (e.g., Buffer State Reporting (BSR) MAC CE or Power Headroom Report (PHR) MAC CE) within the RACH message 3 for scenarios where the RACH is performed for early TA acquisition.

[0084] FIG. 4 illustrates an example of an RRC message 400 that supports timing alignment acquisition in accordance with aspects of the present disclosure. The RRC message 400, for instance, can be used for the purpose of contention resolution and/or to notify the network that a RACH is performed for early TA acquisition.

[0085] FIG. 5 illustrates an example of system 500 that supports timing alignment acquisition in accordance with aspects of the present disclosure. In the system 500, at 502 a UE 104 transmits an RRCSetupRequest message to a network entity 102 indicating a purpose of early TA acquisition from the network entity 102. The network entity 102, for instance, represents a candidate gNB. Accordingly, at 504 the network entity 102 transmits an RRCRelease message or an RRCReject message to the UE 104 in response to the reception of the RRCSetupRequest message.

[0086] According to implementations, for scenarios where a Contention Based RACH Access (CBRA) RACH is performed in order to obtain early uplink timing synchronization on a candidate cell and the RRCSetupRequest message (e.g., with a new Establishmentcause) is used as RACH Msg3, there may not be a need to signal in response to the reception of the RACH Msg3 the RRCConnectionSetup message (e.g., DL message in Msg 4, nor to signal the RRCConnectionSetupComplete message in the uplink) in order to complete the RRC connection establishment.

[0087] For instance, according to at least one example, a gNB doesn’t include the RRCConnectionSetup message in a RACH Msg4, e.g., a contention resolution message. Further, a UE may not send a RRCConnectionSetupComplete message in response to a successful contention resolution and completion of the RACH procedure. For example, the candidate gNB sends an RRCRelease or RRCReject message as part of the RACH Msg4. For instance, a Contention Resolution Identity MAC CE is included in RACH Msg4, such as for scenarios where the UE included the RRCSetupRequest message in RACH Msg3.

[0088] In implementations, if a UE performing a CBRA for early TA acquisition does not have a valid C-RNTI, the contention resolution message (RACH Msg4) can be addressed using the Temporary C-RNTI (TC-RNTI) (which can be received in the RACH response message) and the associated DL-Shared Channel (SCH) can contain the contention-resolution message, e.g., Contention Resolution Identity MAC CE. Upon transmission of RACH Message 3, the MAC layer at the UE can start the ra-ContentionResolutionTimer. The value of contention resolution timer can be provided with RACH-ConfigCommon. After starting the timer, the UE can begin monitoring the Physical Downlink Control Channel (PDCCH) for downlink control information (DCI) format 1 0 with the CRC scrambled with corresponding TC-RNTT Upon reception of the PDSCH, the timer is stopped.

[0089] If the decoded MAC PDU contains a Contention Resolution Identity (e.g., within the Contention resolution identity MAC CE) that matches the CCCH SDU transmitted in Message 3, the contention resolution can be considered successful. In implementations, the UE can stop monitoring PDCCH from the candidate cell on which the early TA acquisition RACH procedure was performed in response to a successful contention resolution. Further, the UE can consider the early TA acquisition procedure as successfully completed. In response to the PDSCH reception (RACH Msg4), the UE may transmit Hybrid Automatic Repeat Request (HARQ) feedback on the Physical Uplink Control Channel (PUCCH). As mentioned above, the UE may not transmit the RRCConnectionSetupComplete message for scenarios involving early TA acquisition. In at least one example the candidate gNB sends a RRCRelease or RRCReject message as part of the RACH Msg4 (e.g., Contention Resolution Identity MAC CE is also included in RACH Msg4) in order to complete the early TA acquisition RACH procedure.

[0090] In implementations, a UE includes a MAC CE within the RACH msg3 of an early TA acquisition RACH procedure which is used to identify the RACH procedure as an early TA acquisition RACH procedure and which is also used for contention resolution. In at least one example the MAC CE contains a UE identity and the UE identity can be, for example, a random value or part of the 5G-S-TMSI. The MAC CE can be identified by a new reserved logical channel ID. In at least one example the new MAC CE has a size of 48bits. For scenarios where the UE includes the new MAC CE within the RACH Msg3 of an CBRA RACH procedure performed for early TA acquisition, the UE can start monitoring the PDCCH for DCI format 1 0 with the CRC scrambled with corresponding TC-RNTI upon transmission of the RACH msg3. Upon reception of a PDSCH (RACH Msg4) the UE can check whether the decoded MAC PDU contains a Contention Resolution Identity MAC CE that matches the new MAC CE transmitted in Message 3. Responsive to a match the UE can consider the contention resolution as successful and consider also the early TA acquisition procedure as successfully completed. The UE can stop monitoring PDCCH on the candidate cell.

[0091] In implementations the message 3 does not include other data other than the MAC CE. For instance, no SDU(s) of DRBs or SRB(s) (e.g., user plane data) are included in the RACH Msg3. In at least one example a logical channel restriction is applied for the message 3 of a RACH procedure initiated for the purpose of early TA acquisition. For instance, SDU(s) of RBs/LCH(s) are not permitted to be multiplexed in the RACH message 3. In at least one example the UE considers the data/signaling radio bearer(s) as suspended when generating the TB for the RACH message 3. In at least one example the UE is not permitted to multiplex other MAC CE(s) (e.g., BSR MAC CE or PHR MAC CE) within the RACH message 3 for scenarios where the RACH is performed for early TA acquisition.

[0092] In implementations, a UE includes a C-RNTI MAC CE in the RACH msg3 of an early TA acquisition RACH procedure which is used for contention resolution. In at least one example the UE receives the C-RNTI for the candidate cell within the candidate cell information message from its current serving cell/gNB. The UE can set the C-RNTI field within the C-RNTI MAC CE to the value received within the candidate cell information message, e.g., the C-RNTI of the MAC entity for the candidate cell. According to at least one implementation the C-RNTI MAC CE used for early TA acquisition is different to the C-RNTI MAC CE used in the legacy specifications. The new C-RNTI MAC CE can also be used to identify the RACH procedure as an early TA acquisition RACH procedure. The new C-RNTI MAC CE can be identified by a new reserved logical channel (LCH) ID. In scenarios where the UE already had a C-RNTI assigned, contention resolution can be handled by addressing the UE on the PDCCH using the C-RNTI. Upon detection of its C-RNTI on the PDCCH, the UE can declare the RA attempt successful and there may be no need for contention-resolution-related information on the DL-SCH, e.g., (RACH Msg4). Alternatively or additionally the UE can multiplex a C-RNTI MAC CE and a further new MAC CE within the RACH Msg3 of an early TA acquisition RACH procedure. The new MAC CE may have a fixed size of zero bits and can be used to identify the RACH procedure as an early TA acquisition RACH procedure. The new MAC CE can be identified by a reserved logical channel ID (LCID).

[0093] In implementations the RACH message 3 does not contain data other than the MAC CE(s). For instance, SDU(s) of DRBs and/or SRB(s) (e.g., user plane data) are not included in the RACH Msg3. In at least one example a logical channel restriction is applied for the message 3 of a RACH procedure initiated for the purpose of early TA acquisition, e.g., SDU(s) of RBs/LCH(s) are not permitted to be multiplexed in the RACH message 3. In at least one example the UE considers the data/signaling radio bearer(s) as suspended when generating the TB for the RACH message 3. In at least one example the UE is not permitted to multiplex other MAC CE(s) (e.g., BSR MAC CE or PHR MAC CE) within the RACH message 3 for scenarios where the RACH is performed for early TA acquisition.

[0094] In implementations, the candidate gNB sends a RRCRelease message as RACH Msg4, e.g., in response to receiving a RACH Msg3 which identifies the RACH procedure as an early TA acquisition RACH in order to complete the early TA acquisition RACH procedure.

[0095] In implementations, after successful contention resolution the UE can discard the TC- RNTI received during the early TA acquisition RACH procedure, e.g., within the RACH response message. In at least one example the UE doesn’t set the C-RNTI for the candidate cell to the TC- RNTI value for scenarios where the Msg3 doesn’t include a C-RNTI MAC CE. Alternatively or additionally, the UE can set the C-RNTI for the candidate cell to the value of the received TC-RNTI and stores the C-RNTI value in its context. [0096] In implementations, a UE applies the TA command received during the early TA acquisition RACH procedure (e.g., within the RACH response message) and uses the acquired uplink timing for the transmission of the RACH msg3 and/or the HARQ feedback for RACH Msg 4. In at least one example the UE sets the NTA value for the candidate cell to the TA value received within the RACH response message. For instance, the UE maintains a NTA value for each of the candidate cells for which an early TA acquisition RACH procedure was successfully completed, e.g., early TA was acquired. According to at least one implementation, the UE starts a timer in response to the reception of the TA command within the RACH response message of an early TA acquisition RACH procedure. While the timer is running the UE can consider itself to be uplink synchronized to the candidate cell. In at least one example the timer is associated to the candidate cell and is set to a value signaled by the source cell/current serving cell. In at least one example the timer configuration is signaled within the candidate cell information message. In another example, the timer controlling the validity of early TA can be common to all candidate cells and can be signaled in the RRC Reconfiguration message configuring one or more candidate cells; the value of this timer, for instance, is same as T304 configured by the source cell.

[0097] In implementations, a UE informs the current serving cell/gNB that it has successfully acquired uplink timing synchronization to a candidate cell. Upon having performed and successfully completed an early TA acquisition RACH procedure, the UE can send information to its current serving cell/gNB indicating that it has successfully acquired the TA from the candidate cell. In an example implementation a new MAC CE is used in order to inform the gNB about the successful TA acquisition. Alternatively or additionally, a RRC measurement report includes measurement results for a corresponding measurement identity and indicates if an Early TA has been obtained for at least one of the cells belonging to the corresponding measurement object.

[0098] In implementations, a DCI signals to a UE to perform a random access procedure on a candidate cell for early TA acquisition. According to at least one implementation, the DCI includes a new field which identifies for which cell the UE is to perform a RACH procedure and acquire uplink timing synchronization. The new DCI may be sent after the serving gNB has sent the candidate cell information message to the UE. In at least one example the current PDCCH order (e.g. DCI format 1 0) contains the following information. [0099] DCI format 1 0 is for random access procedure initiated by a PDCCH order, with all remaining fields set as follows:

Random Access Preamble index - 6 bits according to ra-Preamblelndex in Clause 5.1.2 of [8, TS38.321]

UL/SUL indicator - 1 bit. If the value of the "Random Access Preamble index" is not all zeros and if the UE is configured with supplementaryUplink in ServingCellConfig in the cell, this field indicates which UL carrier in the cell to transmit the PRACH according to Table 7.3.1.1.1-1; otherwise, this field is reserved

SS/PBCH index - 6 bits. If the value of the "Random Access Preamble index" is not all zeros, this field indicates the SS/PBCH that shall be used to determine the RACH occasion for the PRACH transmission; otherwise, this field is reserved.

PRACH Mask index - 4 bits. If the value of the "Random Access Preamble index" is not all zeros, this field indicates the RACH occasion associated with the SS/PBCH indicated by "SS/PBCH index" for the PRACH transmission, according to Clause 5.1.1 of [8, TS38.321]; otherwise, this field is reserved

Reserved bits - 12 bits for operation in a cell with shared spectrum channel access; otherwise 10 bits

[0100] In implementations, some of the reserved bits can be used to signal the cell identity information, e.g., information identifying for which candidate cell(s) a UE is to perform a random access procedure to acquire early TA information. Accordingly, the UE, upon reception of the DCI instructing a RACH on one of the candidate cells, uses the SSB/PBCH index and RACH Mask Index of the indicated candidate cell.

[0101] In implementations, the DCI cell identity can be a reference to the candidate cells provided in the candidate cell information message. For instance, candidate cells are identified based on the order in which candidate cell configuration is provided in the candidate cell information message. For example, an identity set to 0 refers to the first candidate cell for which configuration information is provided within the candidate cell information message.

[0102] In implementations, a UE performs a contention-free random access procedure on a candidate cell in order to acquire early TA information. The UE may be provided in the candidate cell information with the dedicated RACH information (e.g., PRACH preamble and PRACH resource) for the Contention Free RACH Access (CFRA). In response to the reception of the preamble transmission used for early TA acquisition, a gNB can send a response message which includes the TA information. According to at least one implementation, a new RAR format can be used as the response message. For instance, a new MAC payload for Random Access Response consists in one example only of a TA command field. In at least one example, no UL grant field or TC-RNTI is contained in the new MAC payload for RAR.

[0103] In an alternative or additional implementation, the UE can ignore the UL grant received in a legacy RAR in response to a PRACH transmission for early TA acquisition for scenarios where the RAR reception was successful. Further, the UE may not perform an UL transmission scheduled by the RAR for early TA acquisition CFRA RACH. In at least one example, the UE considers the early TA acquisition procedure as successfully completed in response to a successful Random Access Response reception.

[0104] In implementations, the UE is provided with uplink resources (e.g., PUSCH resources) in the candidate cells before handover to the candidate cells occurs. According to at least one implementation, the UE sends a message indicating the completion of the handover in response to having received the handover command (e.g. L1/L2 handover command) on the allocated uplink resources in the candidate cell when the UE has moved to the candidate cell. In at least one example the uplink resources are configured grant uplink resources (e.g., configured grant (CG)-PUSCH resources) which are periodically configured for the candidate cells. In at least one example the message sent on the allocated uplink resources is a RRC message, e.g., RRCReconfigurationComplete message and/or HandoverComplete message. According to at least one implementation, the uplink resources (e.g., CG-PUSCH resources) in the candidate cells are provided in the candidate cell information message. For instance, the configured CG-PUSCH resources are autonomously deactivated by the UE when the successful reception of the RRC message (e.g. RRCReconfigurationComplete message ) is acknowledged by the candidate target gNB. In at least one example, the preconfigured CG-PUSCH resources are only to be used for the transmission of the RRC message, e.g., a first message after handover. In at least one example, the UE is not to send other data on the CG-PUSCH resources, with an optional exception of a MAC CE. In at least one example, the CG-PUSCH resources are considered as valid PUSCH resources in response to the reception of the L1/L2 handover command.

[0105] In implementations, the UE sends an uplink signal on the candidate target cell in response to the reception of the L1/L2 handover command. In at least one example the uplink signal is a Sounding Reference Signal (SRS) transmission. For instance, the SRS transmission is performed by the UE when the UE is moved to the target candidate cell, and informs the candidate cell (e.g., new serving cell) that the UE has executed the handover. Upon detection/reception of the uplink signal/SRS transmission, the gNB may schedule UE PUSCH resources for the transmission of an RRC message, e.g., a Handover complete message.

[0106] In implementations, the UE starts monitoring for PDCCH in the target cell in response to the reception of the L1/L2 handover command for scenarios where the UE has already acquired uplink timing synchronization for the target cell, e.g., where early TA was successfully acquired. The target cell may schedule uplink resources to the UE in response to having sent the L1/L2 handover command (e.g., from the source cell) by means of a dynamic uplink grant which is to be used by the UE for the transmission of the RRCReconfigurationComplete message, e.g. indicating the completion of the handover. In at least one example the source cell informs the target cell of the transmission of the L1/L2 handover command to the UE, e.g., successful transmission.

[0107] Accordingly, in summary, implementations described in this disclosure provide for aspects for early TA acquisition including new aspects for RACH procedures, including:

• Upon reception of candidate target cell information, a UE triggers RACH to acquire TA from candidate cells: o RACH procedure can be triggered by RRC

■ Priority order for TA acquisition (order in which neighbor cell information is provided)

• Reserved RACH resources for identification of early TA acquisition RACH;

• Cell (e.g., gNB) indicates whether it supports and/or enables early TA acquisition, such as in SIB and/or in candidate target cell message; • Content of message 3: o Where a UE doesn’t have C-RNTI for candidate cell:

■ A new RRC message is introduced for early TA acquisition RACH and contention resolution;

■ A new MAC CE can be used instead of RRC message to identify early TA acquisition and for contention resolution; o Where a UE has been provided with C-RNTI for candidate cell:

■ A new C-RNTI MAC CE (new reserved LCID) in order to identify early TA acquisition RACH

• UE behavior upon successful contention resolution: o T-CRNTI can be released after successful Contention Resolution

■ Discard T-CRNTI; or

■ Do not set C-RNTI to T-CRNTI o OR store T-CRNTI for later handovers;

■ Target cell configuration may be released by a network procedure o TA can be maintained for the candidate cell;

■ New NTA value for each candidate target cell:

• Timing alignment Timer (TAT): may be retrieved from candidate cell information message and/or may use current TAT value, e.g., if indicated to do so in the RRC Reconfiguration message configuring one or more candidate cells;

• PDCCH order to acquire TA from target cell, e.g., a new DCI content.

• CFRA: UL grant in RAR can be ignored and TA information and RAPID is included in a new RAR format. [0108] FIG. 6 illustrates an example of a block diagram 600 of a device 602 (e.g., an apparatus) that supports timing alignment acquisition 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).

[0109] 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.

[0110] 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). In the context of UE 104, for example, the transceiver 608 and the processor coupled 604 coupled to the transceiver 608 are configured to cause the UE 104 to perform the various described operations and/or combinations thereof.

[OHl] For example, the processor 604 and/or the transceiver 608 may support wireless communication at the device 602 in accordance with examples as disclosed herein. For instance, the processor 604 and/or the transceiver 608 may be configured as and/or otherwise support a means to receive a first message including information for a set of cells; initiate, based at least in part on the first message, a random access procedure on at least one cell of the set of cells; and transmit, to the at least one cell, an uplink signal including a usage information pertaining to the random access procedure.

[0112] Further, in some implementations, the processor is configured to cause the apparatus to receive the first message as a downlink message on a PDSCH; the downlink message on the PDSCH includes a RRC message; the processor is configured to cause the apparatus to transmit the uplink signal as a PRACH preamble; the processor is configured to cause the apparatus to transmit the uplink signal as a PUS CH transmission scheduled by a random access response message; the PUSCH transmission includes a MAC-control element (CE), and the MAC-CE includes an identity; the PUSCH transmission includes a RRC message, and the RRC message includes a field identifying the usage information; the random access procedure includes a contention-based random access procedure.

[0113] Further, in some implementations, the processor is configured to cause the apparatus to trigger the random access procedure via a MAC entity of the apparatus; the usage information includes an indication of timing alignment acquisition, and the processor is configured to cause the apparatus to receive, based at least in part on the uplink signal, timing alignment information; the processor is configured to cause the apparatus to receive an indication of whether the at least one cell of the set of cells supports earlier timing alignment acquisition; the processor is configured to cause the apparatus to determine priority information for the set of cells, and to initiate the random access procedure based at least in part on the priority information; the processor is configured to cause the apparatus to receive, within the first message, an indication of whether the at least one cell supports early timing alignment acquisition, and based at least in part on the indication, to transmit the uplink signal to a candidate cell for obtaining timing alignment information.

[0114] The processor 604 of the device 602, such as a UE 104, may support wireless communication in accordance with examples as disclosed herein. The processor 604 includes at least one controller coupled with at least one memory, and the at least one controller is configured to and/or operable to cause the processor to receive a first message comprising information for a set of cells; initiate, based at least in part on the first message, a random access procedure on at least one cell of the set of cells; and transmit, to the at least one cell, an uplink signal comprising a usage information pertaining to the random access procedure. Further, the at least one controller is configured to and/or operable to cause the processor to perform one or more other operations described herein such as with reference to a UE 104 and/or the device 602.

[0115] The processor 604 of the device 602, such as a UE 104, may support wireless communication in accordance with examples as disclosed herein. The processor 604 includes at least one controller coupled with at least one memory, and the at least one controller is configured to and/or operable to cause the processor to receive a first message including an instruction for a UE to perform a RACH procedure for obtaining timing alignment information from one or more cells of a set of cells; and initiate the RACH procedure with the one or more cells of the set of cells.

[0116] For example, the processor 604 and/or the transceiver 608 may support wireless communication at the device 602 in accordance with examples as disclosed herein. For instance, the processor 604 and/or the transceiver 608 may be configured as and/or otherwise support a means to receive a first message including an instruction to perform a RACH procedure for obtaining timing alignment information from one or more cells of a set of cells; and initiate the RACH procedure with the one or more cells of the set of cells.

[0117] Further, in some implementations, the first message includes downlink control information (DCI) including one or more identities for the one or more cells of the set of cells; the DCI is received as part of physical downlink control channel (PDCCH); the first message includes one or more of a synchronization signal block (SSB), physical broadcast channel (PBCH), or a RACH mask index for the one or more cells for the set of cells; initiate the RACH procedure using the one or more of the SSB, the PBCH, or the RACH mask index; the at least one processor is configured to cause the UE to receive, before the first message, a second message including candidate cell information identifying candidate cells, the candidate cells including at least the one or more cells of the set of cells; the first message includes downlink control information (DCI) including one or more references to the one or more cells of the set of cells from the candidate cells of the second message; the DCI identifies the one or more candidate cells of the set of cells based at least in part on an order of the one or more cells of the set of cells in the candidate cell information; acquire timing alignment information from a target cell of the one or more cells of the set of cells; and start monitoring physical downlink control channel (PDCCH) in the target cell; the at least one processor is configured to cause the UE to start monitoring PDCCH based at least in part on reception of one or more of a layer 1 (LI) handover command or a layer 2 (L2) handover command; receive scheduling of uplink resources from the target cell via a dynamic uplink grant; transmit, via one or more of the uplink resources, a third message indicating completion of a handover to the target cell.

[0118] 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.

[0119] 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.

[0120] 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 M02. 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 iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. In some implementations, the RO controller 610 may be implemented as part of a processor, such as the processor M08. In some implementations, a user may interact with the device 602 via the RO controller 610 or via hardware components controlled by the RO controller 610. [0121] 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 (e.g., 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.

[0122] FIG. 7 illustrates an example of a block diagram 700 of a device 702 (e.g., an apparatus) that supports timing alignment acquisition in accordance with aspects of the present disclosure. The device 702 may be an example of a network entity 102 as described herein. The device 702 may support wireless communication with one or more network entities 102, UEs 104, or any combination thereof. The device 702 may include components for bi-directional communications including components for transmitting and receiving communications, such as a processor 704, a memory 706, a transceiver 708, and an I/O controller 710. 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).

[0123] The processor 704, the memory 706, the transceiver 708, 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 704, the memory 706, the transceiver 708, or various combinations or components thereof may support a method for performing one or more of the operations described herein.

[0124] In some implementations, the processor 704, the memory 706, the transceiver 708, 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 704 and the memory 706 coupled with the processor 704 may be configured to perform one or more of the functions described herein (e.g., executing, by the processor 704, instructions stored in the memory 706). In the context of network entity 102, for example, the transceiver 708 and the processor 704 coupled to the transceiver 708 are configured to cause the network entity 102 to perform the various described operations and/or combinations thereof.

[0125] For example, the processor 704 and/or the transceiver 708 may support wireless communication at the device 702 in accordance with examples as disclosed herein. For instance, the processor 704 and/or the transceiver 708 may be configured as or otherwise support a means to generate a first message including information for a set of cells, the information including information pertaining to obtaining timing alignment information from one or more cells of the set of cells; and transmit the first message to a UE.

[0126] Further, in some implementations, the information for the set of cells includes an indication whether one or more cells of the set of cells support early acquisition of timing alignment; the first message further includes a priority indication for timing alignment with the set of cells; the processor is configured to cause the apparatus to transmit the priority indication in an order that corresponds to a priority order for obtaining timing alignment information for the one or more cells of the set of cells.

[0127] In a further example, the processor 704 and/or the transceiver 708 may support wireless communication at the device 702 in accordance with examples as disclosed herein. The processor 704 and/or the transceiver 708, for instance, may be configured as or otherwise support a means to receive, from a UE, a first message including information pertaining to obtaining first timing alignment information; and transmit, to the UE, a second message including second timing alignment information.

[0128] Further, in some implementations, the second timing alignment information includes an indication of whether the apparatus supports early timing alignment acquisition; the processor is configured to cause the apparatus to transmit the second message via an SIB.

[0129] In a further example the processor 704 and/or the transceiver 708, for instance, may be configured as or otherwise support a means to generate a first message instructing a UE to perform a RACH procedure for obtaining timing alignment information from one or more cells of a set of cells; and transmit the first message to the UE.

[0130] Further, in some implementations, the first message includes downlink control information (DCI) including one or more identities for the one or more cells of the set of cells; the DCI is transmitted as part of physical downlink control channel (PDCCH); the first message includes one or more of a synchronization signal block (SSB), physical broadcast channel (PBCH), or a RACH mask index for the one or more cells for the set of cells; transmit, before the first message, a second message including candidate cell information identifying candidate cells, the candidate cells including at least the one or more cells of the set of cells; the first message includes downlink control information (DCI) including one or more references to the one or more cells of the set of cells from the candidate cells of the second message; the DCI identifies the one or more candidate cells of the set of cells based at least in part on an order of the one or more cells of the set of cells in the candidate cell information.

[0131] The processor 704 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 704 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 704. The processor 704 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 706) to cause the device 702 to perform various functions of the present disclosure.

[0132] The memory 706 may include random access memory (RAM) and read-only memory (ROM). The memory 706 may store computer-readable, computer-executable code including instructions that, when executed by the processor 704 cause the device 702 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 704 but may cause a computer (e.g., when compiled and executed) to perform functions described herein. In some implementations, the memory 706 may include, among other things, a basic VO system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices. [0133] The I/O controller 710 may manage input and output signals for the device 702. The I/O controller 710 may also manage peripherals not integrated into the device M02. In some implementations, the I/O controller 710 may represent a physical connection or port to an external peripheral. In some implementations, the I/O controller 710 may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. In some implementations, the I/O controller 710 may be implemented as part of a processor, such as the processor M06. In some implementations, a user may interact with the device 702 via the I/O controller 710 or via hardware components controlled by the I/O controller 710.

[0134] In some implementations, the device 702 may include a single antenna 712. However, in some other implementations, the device 702 may have more than one antenna 712 (e.g., multiple antennas), including multiple antenna panels or antenna arrays, which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver 708 may communicate bi-directionally, via the one or more antennas 712, wired, or wireless links as described herein. For example, the transceiver 708 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 708 may also include a modem to modulate the packets, to provide the modulated packets to one or more antennas 712 for transmission, and to demodulate packets received from the one or more antennas 712.

[0135] FIG. 8 illustrates a flowchart of a method 800 that supports timing alignment acquisition 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 UE 104 as described with reference to FIGs. 1 through 7. 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.

[0136] At 802, the method may include receiving a first message comprising information for a set of cells. The operations of 802 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 802 may be performed by a device as described with reference to FIG. 1. [0137] At 804, the method may include initiating, based at least in part on the first message, a random access procedure on at least one cell of the set of cells. The operations of 804 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 804 may be performed by a device as described with reference to FIG. 1.

[0138] At 806, the method may include transmitting, to the at least one cell, an uplink signal comprising a usage information pertaining to a random access procedure. The operations of 806 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 806 may be performed by a device as described with reference to FIG. 1.

[0139] FIG. 9 illustrates a flowchart of a method 900 that supports timing alignment acquisition 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 7. 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.

[0140] At 902, the method may include generating a first message comprising information for a set of cells, the information comprising information pertaining to obtaining timing alignment information from one or more cells of the set of cells. The operations of 902 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 902 may be performed by a device as described with reference to FIG. 1.

[0141] At 904, the method may include transmitting the first message to a UE. The operations of 904 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 904 may be performed by a device as described with reference to FIG. 1.

[0142] FIG. 10 illustrates a flowchart of a method 1000 that supports timing alignment acquisition 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 network entity 102 as described with reference to FIGs. 1 through 7. 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.

[0143] At 1002, the method may include receiving, at an apparatus and from a UE, a first message comprising information pertaining to obtaining first timing alignment information. The operations of 1002 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1002 may be performed by a device as described with reference to FIG. 1.

[0144] At 1004, the method may include transmitting, to the UE, a second message comprising second timing alignment information. The operations of 1004 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1004 may be performed by a device as described with reference to FIG. 1.

[0145] FIG. 11 illustrates a flowchart of a method 1100 that supports timing alignment acquisition 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 7. 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.

[0146] At 1102, the method may include receiving a first message comprising an instruction to perform a RACH procedure for obtaining timing alignment information from one or more cells of a set of cells. The operations of 1102 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1102 may be performed by a device as described with reference to FIG. 1.

[0147] At 1104, the method may include initiating the RACH procedure with the one or more cells of the set of cells. The operations of 1104 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1104 may be performed by a device as described with reference to FIG. 1. [0148] FIG. 12 illustrates a flowchart of a method 1200 that supports timing alignment acquisition 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 network entity 102 as described with reference to FIGs.

1 through 7. 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.

[0149] At 1202, the method may include generating a first message instructing a UE to perform a RACH procedure for obtaining timing alignment information from one or more cells of a set of cells. The operations of 1202 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1202 may be performed by a device as described with reference to FIG. 1.

[0150] At 1204, the method may include transmitting the first message to the UE. The operations of 1204 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1204 may be performed by a device as described with reference to FIG. 1.

[0151] 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.

[0152] 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. [0153] 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.

[0154] 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.

[0155] 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. [0156] 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 (e.g., 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.

[0157] 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).

[0158] 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.

[0159] 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

CLAIMS What is claimed is:

1. A user equipment (UE) for wireless communication, comprising: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the UE to: receive a first message comprising an instruction to perform a random access channel (RACH) procedure for obtaining timing alignment information from one or more cells of a set of cells; and initiate the RACH procedure with the one or more cells of the set of cells.

2. The UE of claim 1 , wherein the first message comprises downlink control information (DCI) comprising one or more identities for the one or more cells of the set of cells.

3. The UE of claim 2, wherein the DCI is received as part of physical downlink control channel (PDCCH).

4. The UE of claim 1, wherein the first message comprises one or more of a synchronization signal block (SSB), physical broadcast channel (PBCH), or a RACH mask index for the one or more cells for the set of cells.

5. The UE of claim 4, wherein the at least one processor is configured to cause the UE to initiate the RACH procedure using the one or more of the SSB, the PBCH, or the RACH mask index.

6. The UE of claim 1, wherein the at least one processor is configured to cause the UE to receive, before the first message, a second message comprising candidate cell information identifying candidate cells, the candidate cells comprising at least the one or more cells of the set of cells.

7. The UE of claim 6, wherein the first message comprises downlink control information (DCI) comprising one or more references to the one or more cells of the set of cells from the candidate cells of the second message.

8. The UE of claim 7, wherein the DCI identifies the one or more candidate cells of the set of cells based at least in part on an order of the one or more cells of the set of cells in the candidate cell information.

9. The UE of claim 1 , wherein the at least one processor is configured to cause the UE to: acquire timing alignment information from a target cell of the one or more cells of the set of cells; and start monitoring physical downlink control channel (PDCCH) in the target cell.

10. The UE of claim 9, wherein the at least one processor is configured to cause the UE to start monitoring PDCCH based at least in part on reception of one or more of a layer 1 (LI) handover command or a layer 2 (L2) handover command.

11. The UE of claim 9, wherein the at least one processor is configured to cause the UE to receive scheduling of uplink resources from the target cell via a dynamic uplink grant.

12. The UE of claim 11, wherein the at least one processor is configured to cause the UE to transmit, via one or more of the uplink resources, a third message indicating completion of a handover to the target cell.

13. A processor for wireless communication, comprising: at least one controller coupled with at least one memory and configured to cause the processor to: receive a first message comprising an instruction for a user equipment (UE) to perform a random access channel (RACH) procedure for obtaining timing alignment information from one or more cells of a set of cells; and initiate the RACH procedure with the one or more cells of the set of cells.

14. The processor of claim 13, wherein the first message comprises downlink control information (DCI) comprising one or more identities for the one or more cells of the set of cells.

15. The processor of claim 14, wherein the DCI is received as part of physical downlink control channel (PDCCH).

16. The processor of claim 13, wherein the first message comprises one or more of a synchronization signal block (SSB), physical broadcast channel (PBCH), or a RACH mask index for the one or more cells for the set of cells.

17. The processor of claim 13, wherein the at least one controller is configured to cause the processor to receive, before the first message, a second message comprising candidate cell information identifying candidate cells, the candidate cells comprising at least the one or more cells of the set of cells.

18. The processor of claim 17, wherein the first message comprises downlink control information (DCI) comprising one or more references to the one or more cells of the set of cells from the candidate cells of the second message.

19. A method performed by a user equipment (UE), the method comprising: receiving a first message comprising an instruction to perform a random access channel (RACH) procedure for obtaining timing alignment information from one or more cells of a set of cells; and initiating the RACH procedure with the one or more cells of the set of cells.

20. A base station for wireless communication, comprising: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the base station to: generate a first message instructing a user equipment (UE) to perform a random access channel (RACH) procedure for obtaining timing alignment information from one or more cells of a set of cells; and transmit the first message to the UE.