Method and apparatus for mobility of lower layer trigger to cell supporting multiple transmit-receive points in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. A method performed by a user equipment (UE) in a wireless communication system includes: receiving mobility (LTM) configuration information for layer 1 (L1) / layer 2 (L2) triggering of a cell; receiving an LTM cell switching command for instructing the UE to execute LTM cell switching; applying a radio resource control (RRC) reconfiguration message in LTM configuration information identified by the candidate configuration index included in the LTM cell handover command; and initiating, if the RRC reconfiguration message is associated with a primary cell group (MCG) and includes a system information block 1 (SIB1), a request to acquire one or more desired system information blocks (SIBs) after completion of a random access procedure or an LTM cell handover to the cell.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to wireless networks. More specifically, the present disclosure relates to lower-layer triggered mobility for a cell supporting multiple transmission reception points (TRPs). BACKGROUND

[0002] 5G mobile communication technologies define wide frequency bands so that high transmission rates and new services are possible, and are implemented not only in "Sub 6 GHz" bands but also in "Above 6 GHz" bands (mmWave), e.g., 28 GHz and 39 GHz. Also, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in Terahertz bands (for example, 95 GHz to 3 THz bands) in order to accomplish transmission rates higher than those of 5G mobile communication technologies and ultra-low latencies.

[0003] At the time when the development of 5G mobile communication technologies is in progress, services and functions are being considered in connection with enhanced Mobile Broad Band (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine Type Communications (mMTC), which are based on 4G technologies. Also, 5G mobile communication technologies are expected to be applied not only in terrestrial systems but also in non-terrestrial systems such as air-to-ground, space-to-ground, and satellite communications. Besides, it is considered to be integrated with other technologies such as IoT, AI, and XR (Extended Reality), and to provide intelligent connectivity and services.

[0004] At present, in consideration of services to be supported by 5G mobile communication technologies, discussions are in progress regarding improvement and performance enhancement of initial 5G mobile communication technologies, and there has been ongoing physical layer standardization regarding technologies such as V2X (Vehicle-to-Everything), NR-U (New Radio Unlicensed), NR UE Power Saving, Non-Terrestrial Network (NTN), and Positioning, in which V2X (Vehicle-to-Everything) is used to assist autonomous driving vehicles in making driving decisions based on information about the location and status of vehicles transmitted by the vehicles and to enhance user convenience, NR-U (New Radio Unlicensed) aims to conform to system operations in line with various regulatory requirements in unlicensed bands, Non-Terrestrial Network (NTN) is UE-satellite direct communication for providing coverage in areas where communication with a terrestrial network is not possible.

[0005] Further, air interface architecture / protocols for technologies such as Industrial Internet of Things (IIoT) for support of new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing nodes for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access (2-step RACH for NR) for simplifying a random access procedure are under standardization. System architecture / services for 5G baseline architecture (e.g., service based architecture or service based interface) for combination of Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and mobile edge computing (MEC) for receiving services based on UE location are also under standardization.

[0006] With the commercialization of 5G mobile communication systems, connected devices, which have increased exponentially, will be connected to communication networks, and thus enhanced functionality and performance of 5G mobile communication systems and integrated operations of connected devices are expected to be necessary. For this reason, new research related to the following is scheduled: extension reality (XR) for efficient support of AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality), etc.; 5G performance improvement and complexity reduction by utilizing artificial intelligence (AI) and machine learning (ML); AI service support; metaverse service support; and drone communication.

[0007] Further, such development of 5G mobile communication systems will not only serve as a basis for developing new waveforms for providing coverage in terahertz bands for 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technologies using OAM (Orbital Angular Momentum) and RIS (Reconfigurable Intelligent Surface), but also for developing full-duplex technologies for improving frequency efficiency of 6G mobile communication technologies and ameliorating system networks, AI-based communication technologies for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technologies for implementing services with a level of complexity that exceeds the limits of UE operating capabilities by utilizing super-high-performance communication and computing resources. SUMMARY

[0008] TECHNICAL PROBLEM

[0009] Due to the increasing popularity of smart phones and other mobile data devices, such as tablet computers, "notebook" computers, netbooks, e-book readers, and machine-type devices, among consumers and enterprises, the demand for wireless data traffic is rapidly increasing. In order to meet the high growth in mobile data traffic and support new applications and deployments, improvements in radio interface efficiency and coverage are essential.

[0010] To meet the demand for wireless data traffic since the deployment of 4G communication systems, and to facilitate various vertical applications, 5G / NR communication systems have been developed and are currently being deployed. The 5G / NR mobile communication is driven by the following factors: massive antenna technology, from a traditional cellular band to a high frequency, for providing beamforming gain and supporting increased capacity; new waveforms (e.g., new radio access technology (RAT)) for flexibly accommodating various services / applications having different requirements; a new multiple access scheme for supporting massive connectivity, etc.

[0011] Solution to the problem

[0012] In one embodiment, a method performed by a user equipment (UE) in a wireless communication system is provided. The method includes receiving layer 1 (L1) / layer 2 (L2) triggered mobility (LTM) configuration information of a cell, receiving an LTM cell handover command instructing the UE to perform an LTM cell handover, applying a radio resource control (RRC) reconfiguration message in the LTM configuration information identified by a candidate configuration index included in the LTM cell handover command, and initiating a request to acquire one or more required system information blocks (SIBs) after a random access procedure or an LTM cell handover completion to the cell in case that the RRC reconfiguration message is associated with a master cell group (MCG) and includes a system information block 1 (SIB1).

[0013] In one embodiment, a UE in a wireless communication system is provided. The UE includes a transceiver and a controller. The controller is configured to receive, via the transceiver, LTM configuration information of a cell, receive, via the transceiver, an LTM cell handover command instructing the UE to perform an LTM cell handover, apply a RRC reconfiguration message in the LTM configuration information identified by a candidate configuration index included in the LTM cell handover command, and initiate a request to acquire one or more required SIBs after a random access procedure or an LTM cell handover completion to the cell in case that the RRC reconfiguration message is associated with a MCG and includes a SIB1.

[0014] In one embodiment, a UE in a wireless communication system is provided. The UE includes a transceiver configured to receive a RRC reconfiguration message including a configuration of a LTM candidate cell, and receive a LTM cell handover command instructing the UE to perform a LTM cell handover to the LTM candidate cell. The UE also includes a processor operably coupled to the transceiver. The processor is configured to determine whether the LTM candidate cell belongs to a MCG, and determine whether the configuration of the LTM candidate cell includes a SIB1. The transceiver is further configured to transmit, to the LTM candidate cell, an SI request after successfully completing the LTM cell handover to the LTM candidate cell when the LTM candidate cell belongs to the MCG and the configuration of the LTM candidate cell includes the SIB1.

[0015] In another embodiment, a method of operating a UE in a wireless communication system is provided. The method includes receiving a RRC reconfiguration message including a configuration of a LTM candidate cell, and receiving a LTM cell handover command instructing the UE to perform a LTM cell handover to the LTM candidate cell. The method also includes determining whether the LTM candidate cell belongs to a MCG, and determining whether the configuration of the LTM candidate cell includes a SIB1. The method further includes transmitting, to the LTM candidate cell, an SI request after successfully completing the LTM cell handover to the LTM candidate cell when the LTM candidate cell belongs to the MCG and the configuration of the LTM candidate cell includes the SIB1.

[0016] Advantages of the Invention

[0017] The present disclosure provides apparatuses and methods for lower layer triggered mobility to a cell supporting multiple TRPs.

[0018] Other technical features can be apparent to those skilled in the art from the following figures, description, and claims. BRIEF DESCRIPTION OF DRAWINGS

[0019] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings in which:

[0020] FIG. 1 An example wireless network is shown in which embodiments of the present disclosure can be implemented;

[0021] FIG. 2A An example wireless transmit path is shown in accordance with embodiments of the present disclosure;

[0022] FIG. 2B An example wireless receive path is shown in accordance with embodiments of the present disclosure;

[0023] FIG. 3A An example UE is shown in accordance with embodiments of the present disclosure;

[0024] FIG. 3B An example gNB is shown in accordance with embodiments of the present disclosure;

[0025] FIG. 4 An example procedure 400 for lower layer triggered mobility is shown in accordance with embodiments of the present disclosure;

[0026] FIG. 5 An example procedure for lower layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown in accordance with embodiments of the present disclosure;

[0027] FIG. 6 Another example procedure for lower layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown in accordance with embodiments of the present disclosure;

[0028] FIG. 7 Another example procedure for lower layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown in accordance with embodiments of the present disclosure;

[0029] FIG. 8 Another example procedure for lower layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown in accordance with embodiments of the present disclosure;

[0030] FIG. 9 Another example procedure for lower layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown in accordance with embodiments of the present disclosure;

[0031] FIG. 10 Another example procedure for lower layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown in accordance with embodiments of the present disclosure;

[0032] FIG. 11 An example procedure for lower layer triggered mobility is shown in accordance with embodiments of the present disclosure; and

[0033] FIG. 12 An example method for lower layer triggered mobility to a cell supporting multiple TRPs is shown in accordance with embodiments of the present disclosure. DETAILED DESCRIPTION

[0034] Before undertaking a detailed description of the foregoing, it can be advantageous to set forth definitions of certain terms and phrases used throughout this patent document. The term “coupled” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “transmit,” “receive,” and “communicate,” as well as derivatives thereof, encompass both direct and indirect communication. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and / or. The phrase “associated with,” as well as derivatives thereof, means to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, be proximate to, be bound to or with, have a property of, have relations with, have agreements with, or the like. The term “controller” means any device, system or part thereof that controls at least one operation. Such a controller can be implemented in hardware or a combination of hardware and software and / or firmware. The functionality associated with any particular controller can be centralized or distributed, whether locally or remotely. The phrase “at least one of’ means one or more items, and possibly only one of the listed items. For example, “at least one of A, B, and C” includes A, B, C, A and B, A and C, B and C, and A and B and C.

[0035] Moreover, various functions described below can be implemented or supported by one or more computer programs, each of which is formed from computer readable program code and embodied in a computer readable medium. The terms “application” and “program” refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof. The phrase “computer readable program code” includes any type of computer code, including source code, object code, and executable code. The phrase “computer readable medium” includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. A “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links. Non-transitory computer readable media include media where data is permanently stored and media where data is stored and later overwritten, such as a rewritable optical disc or an erasable memory device.

[0036] Definitions for other certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art will understand that in many, if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases.

[0037] The following discussion FIGS. 1-12 The various embodiments described for the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to restrict the scope of the present disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any suitably arranged wireless communication system.

[0038] To meet increasing demand with respect to wireless data traffic after 4G communication systems have been deployed, 5G / NR communication systems have been developed and are currently being deployed. The 5G / NR communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 28 GHz or 60 GHz bands, so as to implement a higher data rate beyond that of 4G systems. To decrease propagation loss of the radio waves and increase the transmission distance, beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antennas, analog beamforming, large scale antennas techniques are discussed in 5G / NR communication systems.

[0039] In addition, in 5G / NR communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, a device to device (D2D) communication, wireless backhaul, a mobile network, a cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation and the like.

[0040] The discussion of 5G systems and frequency bands associated therewith is for reference only as certain embodiments of the present disclosure can be implemented in 5G systems. However, the present disclosure is not limited to 5G systems or frequency bands associated therewith and embodiments of the present disclosure can be utilized in conjunction with any frequency band. For example, aspects of the present disclosure are also applicable to 6G or even higher versions that can use terahertz (THz) bands.

[0041] The following FIGS. 1-3B Various embodiments are described that are implemented in wireless communication systems and use orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) communication techniques. FIGS. 1-3B The description of the various embodiments of the present disclosure is not meant to imply physical or architectural limitations to the manner in which different embodiments can be implemented. Different embodiments of the present disclosure can be implemented in any suitably-arranged communication system.

[0042] FIG. 1 An example wireless network 100 according to embodiments of the present disclosure is illustrated. FIG. 1 The embodiment of the wireless network illustrated in FIG. 1 is for illustration only. Other embodiments of the wireless network 100 could be used without departing from the scope of the present disclosure.

[0043] As FIG. 1 illustrated, the wireless network includes a gNB 101 (e.g., base station, BS), a gNB 102, and a gNB 103. The gNB 101 communicates with the gNB 102 and the gNB 103. The gNB 101 also communicates with at least one network 130, such as the Internet, a proprietary Internet Protocol (IP) network, or other data network.

[0044] The gNB 102 provides wireless broadband access to the network 130 for a first plurality of user equipment devices (UEs) within a coverage area 120 of the gNB 102. The first plurality of UEs includes a UE 111, which can be located in a small business; a UE 112, which can be located in an enterprise; a UE 113, which can be a WiFi hotspot; a UE 114, which can be located in a first residence; a UE 115, which can be located in a second residence; and a UE 116, which can be a mobile device, such as a cell phone, a wireless laptop computer, a wireless PDA, and so on. The gNB 103 provides wireless broadband access to the network 130 for a second plurality of UEs within a coverage area 125 of the gNB 103. The second plurality of UEs includes the UE 115 and the UE 116. In some embodiments, one or more of the gNBs 101-103 can communicate with each other and with UEs 111-116 using 5G / NR, long term evolution (LTE), long term evolution advanced (LTE-A), WiMAX, WiFi, or other wireless communication techniques.

[0045] Depending on the network type, the term "base station" or "BS" can refer to any component (or collection of components) configured to provide wireless access to a network, such as a transmit point (TP), transmit-receive point (TRP), an enhanced base station (eNodeB or eNB), a 5G / NR base station (gNB), a macrocell, a femtocell, a WiFi access point (AP), or other wireless-enabled devices. Base stations can provide wireless access in accordance with one or more wireless communication protocols, such as 5G / NR Third Generation Partnership Project (3GPP) NR, Long Term Evolution (LTE), LTE Advanced (LTE-A), High Speed Packet Access (HSPA), Wi-Fi 802.11a / b / g / n / ac, etc. For the sake of convenience, the terms "BS" and "TRP" can be used interchangeably herein to refer to a network infrastructure component that provides wireless access to remote terminals. Further, depending on the network type, the term "user equipment" or "UE" can refer to any component such as a "mobile station," "subscriber station," "remote terminal," "wireless terminal," "receive point," or "user device." For the sake of convenience, the terms "user equipment" and "UE" are used interchangeably herein to refer to a remote wireless equipment that wirelessly accesses a BS, whether the UE is a mobile device (such as a mobile telephone or smartphone) or what is commonly referred to as a stationary device (such as a desktop computer or vending machine).

[0046] Dotted lines show the approximate extents of the coverage areas 120 and 125, which are shown as approximately circular for the purposes of illustration and explanation only. It should be clearly understood that the coverage areas associated with gNBs, such as the coverage areas 120 and 125, can have other shapes, including irregular shapes, depending on the configuration of the gNBs and variations in the radio environment associated with natural and man-made obstructions.

[0047] As described in more detail below, one or more of the UEs 111-116 include circuitry, programming or a combination thereof for mobility with lower layer triggered to a cell supporting multiple TRPs. In certain embodiments, one or more of the gNBs 101-103 include circuitry, programming or a combination thereof to support mobility with lower layer triggered to a cell supporting multiple TRPs in a wireless communication system.

[0048] Although FIG. 1 One example of a wireless network is illustrated, but FIG. 1Various modifications can be made. For example, the wireless network can include any number of gNBs and any number of UEs in any suitable arrangement. Furthermore, gNB 101 can communicate directly with any number of UEs and provide these UEs with wireless broadband access to network 130. Similarly, each gNB 102-103 can communicate directly with network 130 and provide UEs with direct wireless broadband access to network 130. Additionally, gNBs 101, 102, and / or 103 can provide access to other or additional external networks (such as external telephone networks or other types of data networks).

[0049] FIG. 2A and FIG. 2B Example wireless transmit and receive paths according to embodiments of the present disclosure are illustrated. In the following description, transmit path 200 may be described as being implemented in a gNB (such as gNB 102), and receive path 250 may be described as being implemented in a UE (such as UE 116). However, it should be understood that receive path 250 may be implemented in the gNB, and transmit path 200 may be implemented in the UE. In some embodiments, transmit path 200 and / or receive path 250 are configured to implement and / or support lower-layer triggered mobility to cells supporting multiple TRPs, as described in embodiments of the present disclosure.

[0050] The transmit path 200 includes a channel coding and modulation block 205, a serial-to-parallel (S-to-P) block 210, an N-size inverse fast Fourier transform (IFFT) block 215, a parallel-to-serial (P-to-S) block 220, a cyclic prefix addition block 225, and an up-converter (UC) 230. The receive path 250 includes a down-converter (DC) 255, a cyclic prefix removal block 260, a serial-to-parallel (S-to-P) block 265, an N-size fast Fourier transform (FFT) block 270, a parallel-to-serial (P-to-S) block 275, and a channel decoding and demodulation block 280.

[0051] In transmit path 200, channel coding and modulation block 205 receives a set of information bits, applies coding (such as low-density parity-check (LDPC) coding), and modulates the input bits (such as using quadrature phase shift keying (QPSK) or quadrature amplitude modulation (QAM)) to generate a frequency-domain modulated symbol sequence. Serial-to-parallel block 210 converts (e.g., demultiplexes) the serial modulated symbols into parallel data to generate N parallel symbol streams, where N is the IFFT / FFT size used in gNB 102 and UE 116. IFFT block 215 of size N performs an IFFT operation on the N parallel symbol streams to generate a time-domain output signal. Parallel-to-serial block 220 converts (e.g., multiplexes) the parallel time-domain output symbols from IFFT block 215 of size N to generate a serial time-domain signal. Cyclic prefix addition block 225 inserts a cyclic prefix into the time-domain signal. Upconverter 230 modulates (such as upconverts) the output of cyclic prefix block 225 to an RF frequency for transmission via a wireless channel. The signal can also be filtered at baseband before conversion to the RF frequency.

[0052] The transmitted RF signal from gNB 102 reaches UE 116 after passing through the wireless channel, and performs the opposite operation to that at gNB 102. Downconverter 255 downconverts the received signal to the baseband frequency, and cyclic prefix removal block 260 removes the cyclic prefix to generate a serial time-domain baseband signal. Serial-to-parallel block 265 converts the time-domain baseband signal into a parallel time-domain signal. FFT block 270 of size N performs an FFT algorithm to generate N parallel frequency-domain signals. Parallel-to-serial block 275 converts the parallel frequency-domain signals into a sequence of modulated data symbols. Channel decoding and demodulation block 280 demodulates and decodes the modulated symbols to recover the original input data stream.

[0053] Each of gNBs 101-103 can implement a transmission path 200 similar to that sent to UEs 111-116 in the downlink, and a reception path 250 similar to that received from UEs 111-116 in the uplink. Similarly, each of UEs 111-116 can implement a transmission path 200 for sending to gNBs 101-103 in the uplink, and a reception path 250 for receiving from gNBs 101-103 in the downlink.

[0054] FIG. 2A and FIG. 2B Each component in the system can be implemented using only hardware or a combination of hardware and software / firmware. As a specific example, FIG. 2A and FIG. 2BAt least some components can be implemented in software, while others can be implemented using configurable hardware or a combination of software and configurable hardware. For example, FFT block 270 and IFFT block 215 can be implemented as configurable software algorithms, where the value of size N can be modified depending on the implementation method.

[0055] Furthermore, although described as using FFT and IFFT, this is merely illustrative and should not be construed as limiting the scope of this disclosure. Other types of transforms, such as the Discrete Fourier Transform (DFT) and Inverse Discrete Fourier Transform (IDFT) functions, may be used. It should be understood that for the DFT and IDFT functions, the value of the variable N can be any integer (e.g., 1, 2, 3, 4, etc.), while for the FFT and IFFT functions, the value of the variable N can be any integer that is a power of 2 (e.g., 1, 2, 4, 8, 16, etc.).

[0056] although FIG. 2A and FIG. 2B An example of a wireless transmit and receive path is shown, but it is possible to modify it further. FIG. 2A and FIG. 2B Make various changes. For example, you can combine, further subdivide, or omit. FIG. 2A and FIG. 2B It includes various components and allows for the addition of additional components as needed. Furthermore, FIG. 2A and FIG. 2B This is intended to illustrate examples of the types of transmit and receive paths that can be used in a wireless network. Any other suitable architecture can be used to support wireless communication in a wireless network.

[0057] FIG. 3A An example UE 116 according to an embodiment of the present disclosure is shown. FIG. 3A The embodiment of UE 116 shown is for illustrative purposes only, and FIG. 1 UEs 111-115 can have the same or similar configurations. However, UEs have a wide variety of configurations, and FIG. 3A This disclosure is not intended to limit the scope of any particular implementation of the UE.

[0058] like FIG. 3A As shown, UE 116 includes an antenna 305, a transceiver 310, and a microphone 320. UE 116 also includes a speaker 330, a processor 340, an input / output (I / O) interface (IF) 345, an input 350, a display 355, and memory 360. Memory 360 includes an operating system (OS) 361 and one or more applications 362.

[0059] The transceiver 310 receives, from the antenna 305, an incoming RF signal transmitted by a gNB of the network 100. The transceiver 310 down-converts the incoming RF signal to generate an intermediate frequency (IF) or baseband signal. The IF or baseband signal is processed by the transceiver 310 and / or the RX processing circuitry in the processor 340, which generates a processed baseband signal by filtering, decoding, and / or digitizing the baseband or IF signal. The RX processing circuitry transmits the processed baseband signal to the speaker 330 (such as for voice data) or to the processor 340 (such as for web browsing data).

[0060] The transceiver 310 and / or TX processing circuitry in the processor 340 receives analog or digital voice data from the microphone 320 or other outgoing baseband data (such as web access data, e-mail, or interactive video game data) from the processor 340. The TX processing circuitry encodes, multiplexes, and / or digitizes the outgoing baseband data to generate a processed baseband or IF signal. The transceiver 310 up-converts the baseband or IF signal to an RF signal that is transmitted via the antenna 305.

[0061] The processor 340 can include one or more processors or other processing devices and execute the OS 361 stored in the memory 360 in order to control the overall operation of the UE 116. For example, the processor 340 can control the reception of DL channel signals and the transmission of UL channel signals by the transceiver 310, according to well-known principles. In some embodiments, the processor 340 includes at least one microprocessor or microcontroller.

[0062] The processor 340 is also capable of executing other processes and programs stored in the memory 360, such as a process for mobility with lower layer triggered to a cell supporting multiple TRPs, as discussed in more detail below. The processor 340 can move data into or out of the memory 360 as required by the processes executing on the processor 340. In some embodiments, the processor 340 is configured to execute the applications 362 based on the OS 361 or in response to signals received from gNBs or an operator. The processor 340 is also coupled to the I / O interface 345, which provides the UE 116 with the ability to connect to other devices such as laptop computers and handheld computers. The I / O interface 345 is the communication path between these accessories and the processor 340.

[0063] The processor 340 is also coupled to the input 350 and the display 355, the input 350 including, for example, a touchscreen, keypad, and the like. The operator of the UE 116 can use the input 350 to enter data into the UE 116. The display 355 can be a liquid crystal display, light emitting diode display, or other display capable of rendering text and / or at least limited graphics, such as from web sites.

[0064] Memory 360 is coupled to the processor 340. Part of the memory 360 can include random access memory (RAM), and another part of the memory 360 can include non-volatile memory such as flash memory or other read-only memory (ROM).

[0065] Although FIG. 3A One example of a UE 116 is shown, but various changes can be made FIG. 3A For example, FIG. 3A Various components in the computer system 350 can be combined, further subdivided, or omitted and additional components can be added according to particular needs but, as a specific example, the processor 340 can be divided into multiple processors such as one or more central processing units (CPUs) and one or more graphics processing units (GPUs). In another example, the transceiver 310 can include any number of transceivers and signal processing chains and can be connected to any number of antennas. Moreover, while FIG. 3A Although the UE 116 is shown configured as a mobile telephone or smartphone, a UE can be configured to operate as other types of mobile devices or fixed devices.

[0066] FIG. 3B An example gNB 102 according to embodiments of the present disclosure is illustrated. FIG. 3B The embodiment of the gNB 102 illustrated in FIG. 1 The gNBs 101 and 103 of can have the same or similar configuration. However, gNBs have a wide variety of configurations and FIG. 3B The scope of the present disclosure is not limited to any particular implementation of gNBs.

[0067] As FIG. 3B illustrated, the gNB 102 includes multiple antennas 370a-370n, multiple transceivers 372a-372n, a controller / processor 378, memory 380, and a backhaul or network interface 382.

[0068] The transceivers 372a-372n receive, from the antennas 370a-370n, incoming RF signals such as signals transmitted by UEs in the network 100. The transceivers 372a-372n down-convert the incoming RF signals to generate IF or baseband signals. The IF or baseband signals are processed by the transceivers 372a-372n and / or RX processing circuitry within the controller / processor 378 by filtering, decoding, and / or digitizing the baseband or IF signals, to generate processed baseband signals. The controller / processor 378 can further process the baseband signals.

[0069] Transmit (TX) processing circuitry in the transceiver 372a-372n and / or controller / processor 378 receives analog or digital data (such as voice data, web data, e-mail, or interactive video game data) from the controller / processor 378. The TX processing circuitry encodes, multiplexes, and / or digitizes the outgoing baseband data to generate processed baseband or IF signals. The transceiver 372a-372n up-converts the baseband or IF signals to RF signals and transmits the processed RF signals from the antenna 370a-370n.

[0070] The controller / processor 378 can include one or more processors or other processing devices to manage the overall operation of the gNB 102. For example, the controller / processor 378 can control the reception of downlink (DL) channel signals and the transmission of uplink (UL) channel signals by the transceiver 372a-372n in accordance with well-known principles. The controller / processor 378 can support additional functions as well, such as more advanced wireless communication functions. For instance, the controller / processor 378 can support beam forming or directional routing operations in which outgoing / incoming signals from / to multiple antennas 370a-370n are weighted differently to effectively steer the outgoing signals in a desired direction. Any of a wide variety of other functions can be supported in the gNB 102 by the controller / processor 378.

[0071] The controller / processor 378 is also capable of executing programs and other processes resident in the memory 380, such as an OS, and processes for supporting mobility to cells supporting multiple TRPs, as discussed in more detail below. The controller / processor 378 can move data into or out of memory 380 as needed during the execution of these processes.

[0072] The controller / processor 378 is also coupled to a backhaul or network interface 382. The backhaul or network interface 382 allows the gNB 102 to communicate with other devices or systems over a backhaul connection or over a network. The interface 382 can support communication over any suitable wired or wireless connection. For example, when the gNB 102 is implemented as part of a cellular communication system such as a 5G / NR, LTE, or LTE-A cellular communication system, the interface 382 can allow the gNB 102 to communicate with other gNBs over a wired or wireless backhaul connection. When the gNB 102 is implemented as an access point, the interface 382 can allow the gNB 102 to communicate with other gNBs over a wired or wireless local area network or through a wired or wireless connection to a larger network such as the Internet. The interface 382 includes any suitable structure supporting communication over a wired or wireless connection, such as an Ethernet or coaxial connection or a transceiver.

[0073] The memory 380 is coupled to the controller / processor 378. Part of the memory 380 could include a RAM, and another part of the memory 380 could include a flash memory or other ROM.

[0074] Although FIG. 3B various changes can be made to FIG. 3B the gNB 102 could include any number of FIG. 3B components shown in FIG. 1. Also, FIG. 3B components could be combined, further subdivided, or omitted and additional components could be added according to particular needs.

[0075] In next generation wireless communication systems (e.g., 5G, ultra-5G, 6G) operating in higher frequency (mmWave) bands, UEs and gNBs communicate with each other using beamforming. Beamforming techniques are used to mitigate propagation path loss and increase propagation distance to communicate at higher frequency bands. Beamforming uses high-gain antennas to enhance transmission and reception performance. Beamforming can be classified into transmit (TX) beamforming performed in a transmission end and receive (RX) beamforming performed in a reception end. Generally, TX beamforming allows a region where a propagation arrives to be densely located in a specific direction by using multiple antennas. In this case, the aggregation of multiple antennas can be referred to as an antenna array, and each antenna included in the array can be referred to as an array element. The antenna array can be configured in various forms such as a linear array, a planar array, etc. The use of TX beamforming results in an increase in the directivity of a signal, thereby increasing a propagation distance. Also, since a signal is hardly transmitted in a direction other than the directivity direction, signal interference acting on another reception end is significantly reduced. The reception end can perform beamforming on an RX signal by using an RX antenna array. RX beamforming increases RX signal strength transmitted in a specific direction by allowing propagation to be concentrated in the specific direction and excluding signals transmitted in a direction other than the specific direction from the RX signal, thereby providing an effect of blocking an interfering signal. By using beamforming techniques, a transmitter can generate a plurality of transmission beam patterns in different directions. Each of these transmission beam patterns can also be referred to as a transmit (TX) beam. A wireless communication system operating at high frequencies uses multiple narrow TX beams to transmit a signal in a cell, since each narrow TX beam provides coverage for a part of the cell. The narrower the TX beam, the higher the antenna gain, and thus the greater the propagation distance of a signal transmitted using beamforming. A receiver can also generate a plurality of reception (RX) beam patterns in different directions. Each of these reception patterns can also be referred to as a receive (RX) beam.

[0076] Next generation wireless communication systems (e.g., 5G, Ultra 5G, 6G) support standalone operation mode as well as dual connectivity (DC). In DC, a multi-Rx / Tx UE can be configured to utilize resources provided by two different nodes (or NBs) connected via a non-ideal backhaul. One node acts as a master node (MN) and the other node acts as a secondary node (SN). The MN and SN are connected via a network interface and at least the MN is connected to a core network. NR also supports multi-RAT dual connectivity (MR-DC) operation whereby a UE in RRC CONNECTED state is configured to utilize radio resources provided by two different schedulers located in two different nodes connected via a non-ideal backhaul and providing E-UTRA (i.e., if the nodes are ng-eNBs) or NR access (i.e., if the nodes are gNBs). In NR, for a UE in RRC CONNECTED state not configured with CA / DC, there is only one serving cell comprising a primary cell. For a UE in RRC CONNECTED state configured with CA / DC, the term “serving cells” is used to denote the set of cells comprising special cells (SpCells) and all secondary cells (SCells). In NR, the term master cell group (MCG) refers to a set of serving cells associated with a master node comprising a primary cell (PCell) and optionally one or more SCells. In NR, the term secondary cell group (SCG) refers to a set of serving cells associated with a secondary node comprising a PSCell and optionally one or more SCells. In NR, a PCell refers to a serving cell in the MCG operating on a primary frequency where the UE performs an initial connection establishment procedure or initiates a connection re-establishment procedure. In NR, for a UE configured with CA, an SCell is a cell providing additional radio resources on top of a special cell. A primary SCG cell (PSCell) refers to a serving cell in the SCG where the UE performs random access when performing a reconfiguration with sync procedure. For dual connectivity operation, the term SpCell refers to the PCell of the MCG or the PSCell of the SCG, otherwise the term special cell refers to the PCell.

[0077] In next generation wireless communication systems (e.g., 5G, beyond 5G, 6G), a node B (gNB) or base station in a cell broadcasts a synchronization signal and PBCH block (SSB) including primary and secondary synchronization signals (PSS, SSS) and system information. The system information includes common parameters needed for communication in the cell. In the fifth generation wireless communication system (also referred to as next generation radio or NR), the system information (SI) is divided into a master information block (MIB) and multiple system information blocks (SIBs), where: the MIB is transmitted on the BCH with a periodicity of 80 ms and is repeated within 80 ms, and the MIB includes parameters needed to acquire SIB1 from the cell. SIB1 is transmitted on the DL-SCH with a periodicity of 160 ms and variable transmission repetition. The default transmission repetition periodicity for SIB1 is 20 ms, but the actual transmission repetition periodicity depends on network implementation. For SSB and CORESET multiplexing pattern 1, the SIB1 repetition transmission periodicity is 20 ms. For SSB and CORESET multiplexing pattern 2 / 3, the SIB1 transmission repetition periodicity is the same as the SSB periodicity. SIB1 includes information on the availability and scheduling of other SIBs (e.g., mapping of SIBs to SI messages, periodicity, SI window size), with an indication of whether one or more SIBs are provided on-demand only, and in that case, the configuration needed by the UE to perform SI request. SIB1 is a cell-specific SIB; SIBs and posSIBs other than SIB1 are carried in SystemInformation (SI) messages sent on the DL-SCH. SIBs or posSIBs with the same periodicity can be mapped to the same SI message. SIBs and posSIBs are mapped to different SI messages. Each SI message is transmitted within a periodically occurring time domain window (referred to as SI window) that has the same length for all SI messages. Each SI message is associated with an SI window, and the SI windows for different SI messages do not overlap. That is, within one SI window, only the corresponding SI message is transmitted. An SI message can be transmitted multiple times within an SI window. Using the indication in SIB1, any SIB or posSIB other than SIB1 can be configured to be cell-specific or area-specific. A cell-specific SIB is applicable only within the cell providing the SIB, while an area-specific SIB is applicable within an area referred to as an SI area, which includes one or more cells and is identified by a systemInformationAreaID; the mapping of SIBs to SI messages is configured in SchedulingInfoList, while the mapping of posSIBs to SI messages is configured in pos-SchedulingInfoList. Each SIB is contained in a single SI message, and each SIB and posSIB is contained at most once in that SI message.For UEs in RRC CONNECTED state, the network can provide system information by dedicated signaling using RRCReconfiguration message, e.g., if the UE has an active BWP that is not configured to monitor the system information, the common search space of paging, or upon request from the UE. In RRC CONNECTED state, the UE acquires the required SIBs from the PCell. For PSCell and SCell, the network provides the required SI by dedicated signaling (i.e., within RRCReconfiguration message). However, the UE shall acquire the MIB of PSCell to obtain the SFN timing of SCG (which can be different from MCG). Upon change of relevant SI for SCell, the network releases and adds the relevant SCell. For PSCell, the required SI can be changed by reconfiguration with sync.

[0078] In next generation wireless communication systems (e.g., 5G, beyond-5G, 6G), a physical downlink control channel (PDCCH) is used to schedule DL transmissions on a physical downlink shared channel (PDSCH) and UL transmissions on a physical uplink shared channel (PUSCH), where downlink control information (DCI) on the PDCCH includes: a downlink assignment containing at least modulation and coding format, resource allocation, and hybrid-ARQ information related to DL-SCH; and an uplink scheduling grant containing at least modulation and coding format, resource allocation, and hybrid-ARQ information related to UL-SCH. In addition to scheduling, the PDCCH can also be used for: activation and deactivation of configured PUSCH transmission with configured grant; activation and deactivation of PDSCH semi-persistent transmission; informing one or more UEs of the slot format; informing one or more UEs that the UE can assume that there is no transmission intended for the UE on the PRBs and OFDM symbols; transmission of TPC commands for PUCCH and PUSCH; transmission of one or more TPC commands for SRS transmission by one or more UEs; switching the active bandwidth part of a UE; and initiating a random access procedure. A UE monitors a set of PDCCH candidates in configured monitoring occasions in one or more configured control resource sets (CORESETs) according to a corresponding search space configuration. A CORESET comprises a set of PRBs with a duration of 1 to 3 OFDM symbols. Within a CORESET, resource units resource element groups (REGs) control channel elements (CCEs) are defined, where each CCE comprises a set of REGs. Control channels are formed by aggregation of CCEs. Different code rates for control channels are achieved by aggregating different number of CCEs. Interleaved and non-interleaved CCE-to-REG mapping is supported in a CORESET. Polar coding is used for PDCCH. Each resource element group carrying a PDCCH carries its own DMRS. QPSK modulation is used for PDCCH.

[0079] In the next generation wireless communication system (e.g., 5G, beyond 5G, 6G), a gNB signals a list of search space configurations for each configured BWP of a serving cell, where each search configuration is uniquely identified by a search space identifier. The search space identifier is unique in a BWP of a serving cell. The gNB explicitly signals the identifier of the search space configuration to be used for a specific purpose such as paging reception, SI reception, random access response reception, etc. for each configured BWP. In NR, a search space configuration includes parameters Monitoring-periodicity-PDCCH-slot, Monitoring-offset-PDCCH-slot, Monitoring-symbols-PDCCH-within-slot, and duration. A UE determines a PDCCH monitoring occasion within a slot using the parameters PDCCH monitoring periodicity (Monitoring-periodicity-PDCCH-slot), PDCCH monitoring offset (Monitoring-offset-PDCCH-slot), and PDCCH monitoring pattern (Monitoring-symbols-PDCCH-within-slot). The PDCCH monitoring occasion is in slot 'x' to x + duration, where the slot number 'x' in a radio frame number 'y' satisfies the following equation:

[0080] (y (slot number in a radio frame) + x - monitoring-offset-PDCCH-slot) mod (Monitoring-periodicity-PDCCH-slot) = 0.

[0081] The starting symbol of a PDCCH monitoring occasion in each slot with PDCCH monitoring occasions is given by Monitoring-symbols-PDCCH-within-slot. The length of a PDCCH monitoring occasion in units of symbols is given in the CORESET associated with the search space. The search space configuration includes an identifier of the CORESET configuration associated with it. The gNB signals a list of CORESET configurations for each configured BWP of a serving cell, where each CORESET configuration is uniquely identified by a CORESET identifier. The Coreset identifier is unique in a BWP of a serving cell. Note that each radio frame has a duration of 10 ms. A radio frame is identified by a radio frame number or a system frame number. Each radio frame includes a number of slots, where the number of slots in a radio frame and the duration of a slot depend on the subcarrier spacing. The number of slots in a radio frame and the duration of a slot for each supported SCS are pre-defined in NR. Each CORESET configuration is associated with a list of TCI (Transmission Configuration Indicator) states. Each TCI state configures a DL RS ID (SSB or CSI RS). The list of TCI states corresponding to a CORESET configuration is signaled by the gNB via RRC signaling. One of the TCI states in the list of TCI states is activated by the gNB and indicated to the UE. The TCI state indicates the DL TX beam (the DL TX beam is QCL (Quasi Co-located) with the SSB / CSI RS of the TCI state) used by the gNB for transmission of PDCCH in the PDCCH monitoring occasions of the search space.

[0082] In next generation wireless communication systems (e.g., 5G, beyond 5G, 6G), bandwidth adaptation (BA) is supported. With BA, the receive and transmit bandwidth of a UE does not need to be as large as the bandwidth of a cell and can be adjusted: the width can be commanded to change (e.g., shrink during low activity periods to save power); the location can be moved in the frequency domain (e.g., to increase scheduling flexibility); and the subcarrier spacing can be commanded to change (e.g., to allow for different services). A subset of the total cell bandwidth of a cell is referred to as a bandwidth part (BWP). BA is achieved by configuring a UE in RRC connected with BWPs and telling the UE which of the configured BWPs is currently the active BWP. When BA is configured, a UE only has to monitor PDCCH on one active BWP, i.e., it does not have to monitor PDCCH on the entire DL frequency of a serving cell. In RRC connected state, for each configured serving cell (i.e., PCell or SCell), a UE is configured with one or multiple DL and UL BWPs. For an activated serving cell, there is always one active UL and DL BWP at any point in time. BWP switching of a serving cell is used to activate a non-active BWP and deactivate an active BWP at a time. BWP switching is controlled by PDCCH indicating downlink assignment or uplink grant, by bwp-InactivityTimer, by RRC signaling, or by the MAC entity itself when initiating a random access procedure. Upon addition of a SpCell or activation of an SCell, the DL BWP and UL BWP indicated by firstActiveDownlinkBWP-Id and firstActiveUplinkBWP-Id, respectively, are active without receiving PDCCH indicating downlink assignment or uplink grant. The active BWP of a serving cell is indicated by RRC or PDCCH. For unpaired spectrum, DL BWP is paired with UL BWP and BWP switching is common for both UL and DL. Upon expiry of the BWP inactivity timer, the UE switches from the active DL BWP to the default DL BWP or initial DL BWP (if the default DL BWP is not configured).

[0083] In next generation wireless communication systems (e.g., 5G, beyond 5G, 6G), random access (RA) is supported. Random access (RA) is used to achieve uplink (UL) time synchronization. RA is used during initial access, handover, radio resource control (RRC) connection re-establishment procedure, scheduling request transmission, secondary cell group (SCG) addition / modification, beam failure recovery, and transmission of data or control information in the UL by a non-synchronized UE in RRC connected state. Several types of random access procedures are supported.

[0084] In contention-based random access (CBRA) (also known as 4-step CBRA), the UE first transmits a random access preamble (also known as Msgl), and then waits for a random access response (RAR) in a RAR window. The RAR is also known as Msg2. The next generation NodeB (gNB) transmits the RAR on PDSCH. The PDCCH scheduling the PDSCH carrying the RAR is addressed to a RA-radio network temporary identifier (RA-RNTI). The RA-RNTI identifies the time-frequency resource (also known as a physical RA channel (PRACH) occasion or PRACH transmission (TX) occasion or RA channel [RACH] occasion) in which the gNB detected the RA preamble. The RA-RNTI is calculated as follows: RA-RNTI = 1 + s_id + 14 t_id + 14 80 f_id + 14 80 8 ul_carrier_id, where s_id is the index of the first orthogonal frequency-division multiplexing (OFDM) symbol of the PRACH occasion in which the UE has transmitted the Msgl (i.e., the RA preamble); 0 < s-id < 14; t_id is the index of the first slot of the PRACH occasion (0 < t_id < 80); f_id is the index of the PRACH occasion within the slot in the frequency domain (0 < f_id < 8), and ul_carrier_id is the UL carrier used for the Msgl transmission (0 for normal UL (NUL) carrier and 1 for supplementary UL (SUL) carrier). Several RARs for various random access preambles detected by the gNB can be multiplexed by the gNB in the same RAR medium access control (MAC) protocol data unit (PDU). The RAR in the MAC PDU corresponds to the UE’s RA preamble transmission if the RAR includes the RA preamble identifier (RAPID) of the RA preamble transmitted by the UE. If no RAR corresponding to the UE’s RA preamble transmission is received during the RAR window, and the UE has not transmitted the RA preamble a configurable number of times (configured by the gNB in the RACH configuration), the UE goes back to the first step, i.e., selects a random access resource (preamble / RACH occasion) and transmits the RA preamble. Backoff can be applied before going back to the first step.

[0085] If a RAR corresponding to the UE's RA preamble transmission is received, the UE transmits a message 3 (Msg3) in the UL grant received in the RAR. The Msg3 includes a message such as a RRC connection request, a RRC connection reestablishment request, a RRC handover confirm, a scheduling request, an SI request, etc. The Msg3 can include a UE identity (i.e., a cell radio network temporary identifier (C-RNTI) or a system architecture evolution (SAE)-temporary mobile subscriber identity (S-TMSI) or a random number). After transmitting the Msg3, the UE starts a contention resolution timer. While the contention resolution timer is running, if the UE receives a physical downlink control channel (PDCCH) addressed to the C-RNTI included in the Msg3, the contention resolution is considered successful, the contention resolution timer stops, and the RA procedure is completed. While the contention resolution timer is running, if the UE receives a contention resolution MAC control element (CE) including the UE's contention resolution identity (the first X bits of the common control channel (CCCH) service data unit (SDU) transmitted in the Msg3), the contention resolution is considered successful, the contention resolution timer stops, and the RA procedure is completed. If the contention resolution timer expires and the UE has not transmitted the RA preamble a configurable number of times, the UE returns to the first step, i.e., selecting a random access resource (preamble / RACH occasion) and transmitting the RA preamble. Backoff can be applied before returning to the first step.

[0086] Contention free random access (CFRA) (also referred to as legacy CFRA or 4-step CFRA) is used for scenarios such as handover requiring low latency, timing advance establishment for secondary cell (Scell), etc. An evolved node B (eNB) assigns a dedicated random access preamble to a UE. The UE transmits the dedicated RA preamble. The eNB transmits a RAR on a PDSCH addressed to a RA-RNTI. The RAR conveys a RA preamble identifier and timing alignment information. The RAR can also include a UL grant. Similar to a contention based RA (CBRA) procedure, the RAR is transmitted in a RAR window. After receiving a RAR including a RA preamble identifier (RAPID) of the RA preamble transmitted by the UE, the CFRA is considered to be successfully completed. In case of initiating the RA for beam failure recovery, the CFRA is considered to be successfully completed if a PDCCH addressed to a C-RNTI is received in a search space for beam failure recovery. If the RAR window expires and the RA is not successfully completed and the UE has not transmitted the RA preamble a configurable (configured by the gNB in the RACH configuration) number of times, the UE retransmits the RA preamble.

[0087] For certain events, such as handover and beam failure recovery, if a dedicated preamble is assigned to the UE, the UE determines whether to transmit a dedicated preamble or a non-dedicated preamble during the first step of random access, i.e., during random access resource selection for Msgl transmission. Dedicated preambles are typically provided for a subset of SSBs / CSIRS. If there is no SSB / CSIRS with a DL RSRP above a threshold in the SSB / CSIRS for which the gNB provides contention-free random access resources (i.e., dedicated preamble / RO), the UE selects a non-dedicated preamble. Otherwise, the UE selects a dedicated preamble. Thus, during a RA procedure, one random access attempt can be CFRA, while other random access attempts can be CBRA.

[0088] For 2-step contention-based random access (2-step CBRA), in the first step, the UE transmits a random access preamble on PRACH and a payload (i.e., MAC PDU) on PUSCH. The random access preamble and payload transmission is also referred to as MsgA. In the second step, after the MsgA transmission, the UE monitors for a response from the network (i.e., gNB) within a configured window. The response is also referred to as MsgB. The next generation NodeB (gNB) transmits MsgB on PDSCH. The PDCCH scheduling the PDSCH carrying MsgB is addressed to MsgB-Radio Network Temporary Identifier (MSGB-RNTI). The MSGB-RNTI identifies the time-frequency resource (also referred to as physical RA channel (PRACH) occasion or PRACH transmission (TX) occasion or RACH occasion) in which the gNB detected the RA preamble. The MSGB-RNTI is computed as follows: RA-RNTI = 1 + s_id + 14 t_id + 14 80 f_id + 14 80 8 ul_carrier_id + 14 x 80 x 8 x 2, where s_id is the index of the first orthogonal frequency-division multiplexing (OFDM) symbol of the PRACH occasion in which the UE has transmitted Msgl (i.e., RA preamble); 0 < s_id < 14; t_id is the index of the first slot of the PRACH occasion (0 < t_id < 80); f_id is the index of the PRACH occasion within the slot in the frequency domain (0 < f_id < 8), and ul_carrier_id is the UL carrier used for Msgl transmission (0 for normal UL (NUL) carrier, 1 for supplementary UL (SUL) carrier).

[0089] If a common control channel (CCCH) service data unit (SDU) is sent in the MsgA payload, the UE performs contention resolution using the contention resolution information in MsgB. Contention resolution is successful if the contention resolution received in MsgB identifies a match to the first 48 bits of the CCCH SDU sent in MsgA. Contention resolution is successful if the C-RNTI is sent in the MsgA payload, if the UE receives a PDCCH addressed to the C-RNTI. If contention resolution is successful, the random access procedure is considered to be successfully completed. Instead of contention resolution information corresponding to the sent MsgA, MsgB can include backoff information corresponding to the random access preamble sent in MsgA. If backoff information is received, the UE sends Msg3 and performs contention resolution using Msg4 as in the CBRA procedure. If contention resolution is successful, the random access procedure is considered to be successfully completed. If contention resolution fails at backoff (i.e., at the time of sending Msg3), the UE retransmits MsgA. If the configured window for the UE to monitor for a network response expires after sending MsgA, and the UE does not receive MsgB including contention resolution information or backoff information as described above, the UE retransmits MsgA. If the random access procedure is not successfully completed even after the configurable number of times of sending MsgA, the UE falls back to the 4-step RACH procedure, i.e., the UE only sends a PRACH preamble.

[0090] A MsgA payload can include one or more of a common control channel (CCCH) service data unit (SDU), a dedicated control channel (DCCH) SDU, a dedicated traffic channel (DTCH) SDU, a buffer status report (BSR) MAC control element (CE), a power headroom report (PHR) MAC CE, SSB information, a C-RNTI MAC CE, or padding. A MsgA can include a UE ID (e.g., a random ID, an S-TMSI, a C-RNTI, a resume ID, etc.) and a preamble in the first step. The UE ID can be included in a MAC PDU of the MsgA. A UE ID such as a C-RNTI can be carried in a MAC CE, which is included in the MAC PDU. Other UE IDs such as a random ID, an S-TMSI, a C-RNTI, a resume ID, etc. can be carried in a CCCH SDU. The UE ID can be one of a random ID, an S-TMSI, a C-RNTI, a resume ID, an IMSI, an idle mode ID, an inactive mode ID, etc. The UE ID can be different in different scenarios when the UE performs a RA procedure. When the UE performs a RA after power on (before the UE is attached to a network), then the UE ID is a random ID. When the UE performs a RA in an idle state after the UE is attached to a network, the UE ID is an S-TMSI. If the UE has an assigned C-RNTI (e.g., in a connected state), then the UE ID is a C-RNTI. In the case of the UE being in an inactive state, the UE ID is a resume ID. In addition to the UE ID, some additional control information can be sent in the MsgA. The control information can be included in a MAC PDU of the MsgA. The control information can include one or more of a connection request indication, a connection resume request indication, an SI request indication, a buffer status indication, beam information (e.g., one or more DL TX beam IDs or SSB IDs), a beam failure recovery indication / information, a data indicator, a cell / BS / TRP switch indication, a connection re-establishment indication, a reconfiguration complete or handover complete message, etc.

[0091] In 2-step contention-free random access (2-step CFRA), a gNB allocates a dedicated random access preamble and PUSCH resources for MsgA transmission to a UE. The RO to be used for preamble transmission can also be indicated. In the first step, the UE transmits a random access preamble on PRACH and a payload on PUSCH using the contention-free random access resources (i.e., dedicated preamble / PUSCH resources / RO). In the second step, after the MsgA transmission, the UE monitors for a response from the network (i.e., gNB) within a configured window. The response is also referred to as MsgB.

[0092] The next generation NodeB (gNB) transmits MsgB on a physical downlink shared channel (PDSCH). The PDCCH scheduling the PDSCH carrying MsgB is addressed to a MsgB-radio network temporary identifier (MSGB-RNTI). The MSGB-RNTI identifies the time-frequency resource (also referred to as a physical RA channel (PRACH) occasion or PRACH transmission (TX) occasion or RA channel (RACH) occasion) in which the gNB detected the RA preamble. The MsgB-RNTI is computed as follows: RA-RNTI = 1 + s_id + 14 t_id + 14 80 f_id + 14 80 8 ul_carrier_id + 14 x 80 x 8 x 2, where s_id is the index of the first orthogonal frequency-division multiplexing (OFDM) symbol of the PRACH occasion in which the UE has transmitted Msgl (i.e., the RA preamble); 0 < s_id < 14; t_id is the index of the first slot of the PRACH occasion (0 < t_id < 80); f_id is the index of the PRACH occasion within the slot in the frequency domain (0 < f_id < 8), and ul_carrier_id is the UL carrier used for Msgl transmission (0 for normal UL (NUL) carrier, 1 for supplementary UL (SUL) carrier).

[0093] The random access procedure is considered successfully completed if the UE receives a PDCCH addressed to C-RNTI. The random access procedure is considered successfully completed if the UE receives a fallback information corresponding to the preamble it has transmitted.

[0094] For certain events, such as handover and beam failure recovery, if a dedicated preamble and PUSCH resources are allocated to the UE during the first step of random access (i.e., during random access resource selection for MsgA transmission), the UE determines whether to transmit a dedicated preamble or a non-dedicated preamble. Dedicated preambles are typically provided for a subset of SSB / CSIRS. If there is no SSB / CSIRS with a DL RSRP above a threshold in the SSB / CSIRS for which the gNB provides contention-free random access resources (i.e., dedicated preamble / RO / PUSCH resources), the UE selects a non-dedicated preamble. Otherwise, the UE selects a dedicated preamble. Thus, during a RA procedure, one random access attempt can be 2-step CFRA, while another random access attempt can be 2-step CBRA.

[0095] At the initiation of a random access procedure, the UE first selects a carrier (SUL or NUL). If the carrier for the random access procedure is explicitly signaled by the gNB, the UE selects the signaled carrier to perform the random access procedure. If the carrier for the random access procedure is not explicitly signaled by the NB, and if the serving cell for the random access procedure is configured with a supplementary uplink, and if the RSRP of the downlink pathloss reference is less than rsrp-ThresholdSSB-SUL, the UE selects the SUL carrier for performing the random access procedure. Otherwise, the UE selects the NUL carrier to perform the random access procedure. At the selection of the UL carrier, the UE determines the UL BWP and DL BWP for the random access procedure. Then, the UE determines whether to perform 2-step RACH or 4-step RACH for this random access procedure.

[0096] If the random access procedure is initiated by a PDCCH order, and if the ra-PreambleIndex explicitly provided by the PDCCH is not 0b000000, the UE selects 4-step RACH. Otherwise, if the gNB signals 2-step contention-free random access resources for this random access procedure, the UE selects 2-step RACH. Otherwise, if the gNB signals 4-step contention-free random access resources for this random access procedure, the UE selects 4-step RACH. Otherwise, if the UL BWP selected for this random access procedure is configured with only 2-step RACH resources, the UE selects 2-step RACH. Otherwise, if the UL BWP selected for this random access procedure is configured with only 4-step RACH resources, the UE selects 4-step RACH. Otherwise, if the UL BWP selected for this random access procedure is configured with both 2-step and 4-step RACH resources, if the RSRP of the downlink pathloss reference is below a configured threshold, the UE selects 4-step RACH. Otherwise, the UE selects 2-step RACH.

[0097] Layer 1 (L1) / Layer 2 (L2) triggered mobility (LTM) (also referred to herein as lower layer triggered mobility) is a procedure in which a gNB receives an L1 / L3 measurement report from a UE, and based on the L1 / L3 measurement report, the gNB changes the serving cell of the UE by a cell change command signaled via a MAC CE. The cell change command indicates the LTM candidate cell configuration that the gNB previously prepared and provided to the UE by RRC signaling. The UE then switches to the target cell according to the cell change command. The LTM procedure can be used to reduce the mobility latency. The network can request the UE to perform an early TA acquisition of the candidate cell prior to the cell switch. The early TA acquisition is triggered by a PDCCH order or by UE-based TA measurement.

[0098] The network indicates in the cell handover command whether the UE should access the target cell with the RA procedure without providing a TA value or with PUSCH transmission using the indicated TA value. For LTM without RACH, the UE accesses the target cell via the configured grant provided in the RRC signaling and selects the configured grant occasion associated with the beam indicated in the cell handover command. If the UE does not receive a configured grant in the RRC signaling, the UE monitors the PDCCH for dynamic scheduling from the target cell at LTM cell handover. The UE shall not trigger a random access procedure if it does not have a valid PUCCH resource for the SR to trigger until the LTM without RACH procedure is completed.

[0099] FIG. 4 An example procedure 400 for lower-layer triggered mobility is shown in accordance with an embodiment of the disclosure. FIG. 4 Embodiments of the procedures shown in the figures are for illustration only. FIG. 4 One or more components shown in the figures can be implemented in specialized circuitry configured to perform the recited functions, or one or more components can be implemented by one or more processors executing instructions to perform the recited functions. Other embodiments of lower-layer triggered mobility can be used without departing from the scope of the disclosure.

[0100] In FIG. 4 In an example of FIG. 4, the UE 402 is in RRC CONNECTED state. At step 1, the UE 402 sends a MeasurementReport message to the gNB 404. The gNB 404 decides to configure LTM and initiates candidate cell preparation.

[0101] At step 2, the gNB 404 sends an RRCReconfiguration message to the UE 402, which includes LTM candidate cell configuration for one or more candidate cells.

[0102] At step 3, the UE 402 stores the LTM candidate cell configuration and sends an RRCReconfigurationComplete message to the gNB 404.

[0103] At step 4a, the UE 402 can perform DL synchronization with the candidate cell before receiving the cell handover command.

[0104] At step 4b, if requested by the network, the UE 402 performs early TA acquisition on the candidate cell prior to receiving the cell change command. Early TA acquisition is performed through CFRA triggered by a PDCCH order from the source cell, followed by the UE 402 sending a preamble to the indicated candidate cell. To minimize data interruption to the source cell due to CFRA towards the candidate cell, the UE 402 does not receive a RAR for TA value acquisition and the TA value of the candidate cell is indicated in the cell change command. The UE does not maintain a TA timer for the candidate cell and relies on network implementation to guarantee TA validity.

[0105] At step 5, the UE 402 performs L1 / L3 measurements on the configured candidate cell and sends the L1 / L3 measurement report to the gNB 404.

[0106] At step 6, the gNB 404 decides to perform a cell change to the target cell and sends a MAC CE triggering the cell change including the candidate configuration index of the target cell. The UE 402 changes to the target cell and applies the configuration indicated by the candidate configuration index.

[0107] At step 7, if the UE 402 does not have a valid TA for the target cell, the UE 402 performs a random access procedure for the target cell.

[0108] At step 8, the UE 402 completes the LTM cell change procedure by sending an RRCReconfigurationComplete message to the target cell. If the UE 402 has performed a RA procedure in step 7, the UE 402 considers the LTM execution successfully completed when the random access procedure is successfully completed. For LTM without RACH, the UE 402 considers the LTM execution successfully completed when the UE 402 determines that the network has successfully received its first UL data. The UE 402 determines the successful reception of its first UL data by receiving a PDCCH addressed to the UE’s 402 C-RNTI in the target cell scheduling a new transmission after the first UL data.

[0109] Although FIG. 4 One example procedure 400 for lower layer triggered mobility is shown, but various changes can be made FIG. 4 For example, while shown as a series of steps, various steps in FIG. 4 may overlap, occur in parallel, occur in a different order, occur any number of times, be omitted, or be replaced by other steps.

[0110] In existing wireless communication systems, a cell is associated with one Timing Advance Group (TAG), where the UE maintains one timing advance (or TA) value for each TAG, which is used to adjust the UL timing for the cell associated with that TAG. Recently, multiple transmission reception point (TRP) communication is being enabled in 5G systems, where a cell can have multiple TRPs and the UE can communicate with each TRP of the cell to enhance throughput and reliability. DCI can be transmitted independently from each of these TRPs and UL can be transmitted independently to each of these TRPs using the corresponding UL timing. To do this, the UE needs to maintain multiple TAs for each cell, which is different from the existing systems where only one TA is maintained per cell. Each of the TRPs of a cell can be associated with the same physical cell identifier (PCI) or different PCIs.

[0111] If the target cell is associated with multiple TRPs, the target cell can be associated with multiple TAGs. In case of LTM, the UE can estimate the TA itself or it can receive the TA in the LTM cell switch command. In case multiple TAGs are supported in the target cell, the UE does not know which TAG the UE estimated TA or the TA received in the LTM cell switch command should be applied to. The present disclosure provides procedures to enable the UE to determine which TAG the UE estimated TA or the TA received in the LTM cell switch command should be applied to.

[0112] FIG. 5 An example procedure 500 for lower layer triggered mobility to a cell supporting multiple TRPs / TAGs according to an embodiment of the present disclosure is shown. FIG. 5 Embodiments of the method shown in FIG. 5 One or more components shown in can be implemented in dedicated circuitry configured to perform the recited functions, or one or more components can be implemented by one or more processors executing instructions to perform the recited functions. Other embodiments of lower layer triggered mobility to a cell supporting multiple TRPs / TAGs can be used without departing from the scope of the present disclosure.

[0113] In FIG. 5In the example of FIG. 5, the procedure starts at step 510. At step 510, the gNB (or base station) 504 of cell A provides the LTM configuration of candidate cell B to the UE 502. Cell A is the serving cell. Cell B is associated with multiple TRPs / TAGs. The TAG ID of each TAG is included in the LTM configuration of candidate cell B. In one embodiment, the number of multiple TRPs / TAGs can be 2, and one of these TAGs / TAG IDs can be referred to as the first TAG (identified by TAG index 0) and the other can be referred to as the second TAG (identified by TAG index 1). The LTM configuration of candidate cell B can include a TA acquisition configuration. The TA acquisition configuration includes RRC configuration information for transmitting a random access preamble to cell B so that the gNB 506 to which cell B belongs can calculate a TA value to be used by the UE 502, e.g., in case of performing an LTM cell handover procedure to cell B. The LTM configuration of candidate cell B can include the configuration of cell B to be applied in case of performing an LTM cell handover procedure to cell B. The LTM configuration of candidate cell B can include a list of TCI states, where each TCI state is associated with one of the TAGs of cell B. In case cell A and cell B belong to different DUs of the same gNB, the gNB (or base station) 504 can obtain the configuration of cell B from the distributed units (DUs) of cell B. In case cell A and cell B belong to different DUs of different gNBs, the gNB (or base station or central unit (CU)) 504 of cell A can obtain the configuration of cell B from the gNB (or base station or CU) 506 of cell B. The LTM configuration of candidate cell B can include an L1 measurement configuration.

[0114] At step 520, the UE 502 confirms the RRC reconfiguration by sending an RRC reconfiguration complete message.

[0115] At step 530, the gNB (or base station) 504 to which cell A belongs sends a PDCCH order to the UE 502 in order to initiate a TA acquisition procedure with cell B. The PDCCH order includes information for transmitting a random access preamble to cell B (e.g., random access preamble index, SSB index, UL carrier (SUL or NUL)). Note that after sending the RRCReconfiguration complete message, the UE 502 performs L1 measurements of cell B and reports the measurements to the gNB (or base station) 504 to which cell A belongs. Based on these measurements, the gNB 504 can identify the UL carrier and SSB index of cell B to be included in the PDCCH order.

[0116] At step 540, for example, if the LTM cell handover procedure is triggered to cell B, the UE 502 sends a random access preamble to cell B so that the gNB 506 to which cell B belongs can calculate a TA value to be used by the UE 502.

[0117] In one embodiment, in case cell A and cell B belong to different DUs of the same gNB, the DU of cell B can determine the TA and TAG based on the received random access preamble and inform the DU of cell A about the determined TA and TAG. The DU of cell B informs the DU of cell A about the TAG ID or TAG index of the determined TAG. For example, cell B can be associated with two TAGs (TAG A and TAG B) with TAG IDs. TAG A can be referenced by logical TAG index 0 and TAG B can be referenced by logical TAG index 1. In one embodiment, the DU of cell B informs the DU of cell A about the TA and TAG upon receiving the random access preamble. In an alternative embodiment, the DU of cell B informs the DU of cell A about the TA and TAG upon receiving a request for the TA and TAG from the DU of cell A, where the DU of cell A can make the request upon the DU of cell A determining handover to cell B. The DU of cell B can determine the TAG based on the SSB associated with the received random access preamble. Different TRPs / TAGs of cell B can be associated with different SSBs, so the DU of cell B can determine the TRP / TAG based on the SSB associated with the received random access preamble.

[0118] In one embodiment, in case cell A and cell B belong to the same DU of the same gNB, the DU determines the TA and TAG based on the received random access preamble and informs the DU of cell A about the determined TA and TAG. For example, cell B can be associated with two TAGs (TAG A and TAG B) with TAG IDs. TAG A can be referenced by logical TAG index 0 and TAG B can be referenced by logical TAG index 1. The DU of cell B can determine the TAG based on the SSB associated with the received random access preamble. Different TRPs / TAGs of cell B can be associated with different SSBs, so the DU of cell B can determine the TRP / TAG based on the SSB associated with the received random access preamble.

[0119] In one embodiment, in case cell A and cell B belong to different DUs of different gNBs, the DU of cell B can determine the TA and TAG based on the received random access preamble and inform the CU of cell B about the determined TA and TAG. The CU of cell B then sends this information to the CU of cell A, which informs the DU of cell A about this information. The DU of cell A can determine the TA and TAG based on the received random access preamble and inform the CU of cell A about the determined TA and TAG. The CU of cell A then sends this information to the DU of cell A, which informs the DU of cell B about this information. In one embodiment, in case cell A and cell B belong to different DUs of different gNBs, the DU of cell B can determine the TA and TAG based on the received random access preamble and inform the DU of cell A about the determined TA and TAG of cell B. For example, cell B can be associated with two TAGs (TAG A and TAG B) with TAG IDs. TAG A can be referred by logical TAG index 0 and TAG B can be referred by logical TAG index 1. The DU of cell B can determine the TAG based on the SSB associated with the received random access preamble. Different TRPs / TAGs of cell B can be associated with different SSBs, so the DU of cell B can determine the TRP / TAG based on the SSB associated with the received random access preamble.

[0120] In one embodiment, in case cell A and cell B belong to different DUs of different gNBs, the DU of cell B can determine the TA and TAG based on the received random access preamble and inform the UE directly by sending a RAR including the above information. The TAG ID or TAG index of the determined TAG is included in the RAR. The DU of cell B can determine the TAG based on the SSB associated with the received random access preamble. Different TRPs / TAGs of cell B can be associated with different SSBs, so the DU of cell B can determine the TRP / TAG based on the SSB associated with the received random access preamble.

[0121] At step 550, the gNB (or base station) 504 of cell A decides to perform a cell handover to target cell B and sends a MAC CE triggering cell handover including a candidate configuration index of the target cell (i.e., cell B), TAs of cell B, a TAG ID or a TAG index associated with the TAs received from the gNB 506 of cell B. In one embodiment, multiple TAs of cell B can be included in the MAC CE triggering cell handover. The TAGs associated with each of the TAs of cell B are included in the MAC CE triggering cell handover. The TAGs associated with each of the TAs of cell B are not included in the MAC CE triggering cell handover, and a first TA included in the MAC CE belongs to a first TAG and a second TA included in the MAC CE belongs to a second TAG. In one embodiment, the number of multiple TRPs / TAGs can be 2. The multiple TAs / TAGs can be determined using the operations in steps 530 and 540. In one embodiment, one or more TCI state identifiers (identifying joint / UL TCI state / DL TCI state) of each of the multiple TRPs of cell B can be included in the MAC CE triggering cell handover.

[0122] At step 560, the UE 502 hands over to the target cell B and applies the configuration indicated by the candidate configuration index (at step 510, the UE 502 can receive the LTM configurations of multiple candidate cells, and each configuration is identified by a candidate configuration index). The UE 502 applies the TAs received in the MAC CE triggering cell handover to the TAGs (identified by the TAG ID or the TAG index) indicated in the MAC CE triggering cell handover and starts the corresponding TATs. For example, cell B can be associated with two TAGs (TAG A and TAG B) with TAG IDs. TAG A can be referenced by logical TAG index 0 and TAG B can be referenced by logical TAG index 1. The MAC CE can include a TAG ID, i.e., TAG A or TAG B. The MAC CE can include a TAG index, and the UE can identify TAG A or TAG B based on the mapping of the TAG ID to the TAG index.

[0123] At step 570, the UE 502 completes the LTM cell change procedure by sending an RRCReconfigurationComplete message to the target cell B. In one embodiment, if the target cell B is not associated with multiple TAGs and the valid TA of the target cell B is available to the UE 502 (e.g., received in the MAC CE that triggered the cell change or the UE 502 has estimated the TA), the UE 502 does not initiate RACH, performs LTM cell change without RACH, and transmits a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes the RRCReconfigurationComplete message. In one embodiment, if one uplink TCI state identifier is included in the MAC CE that triggered the cell change and the target cell B is associated with multiple TAGs and the valid TA of the TAG associated with the TCI state (identified by the uplink TCI state identifier) is available to the UE 502 (e.g., received in the MAC CE that triggered the cell change or the UE 502 has estimated the TA), the UE 502 does not initiate RACH, performs LTM cell change without RACH, and transmits a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes the RRCReconfigurationComplete message. In one embodiment, if two uplink TCI state identifiers are included in the MAC CE that triggered the cell change and the target cell B is associated with multiple TAGs and the valid TA of the TAG associated with the TCI state identified by at least one uplink TCI state identifier is available to the UE 502 (e.g., received in the MAC CE that triggered the cell change or the UE 502 has estimated the TA), the UE 502 does not initiate RACH, performs LTM cell change without RACH, and transmits a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes the RRCReconfigurationComplete message.

[0124] Although FIG. 5 One example procedure 500 for lower-layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown, various changes can be made FIG. 5 For example, while shown as a series of steps, various steps in FIG. 5 may overlap, occur in parallel, occur in a different order, occur any number of times, be omitted, or be replaced by other steps.

[0125] FIG. 6Another example procedure 600 for lower layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown in accordance with an embodiment of the present disclosure. FIG. 6 Embodiments of the method shown in are for illustration only. FIG. 6 One or more components shown in can be implemented in dedicated circuitry configured to perform the recited functions, or one or more components can be implemented by one or more processors executing instructions to perform the recited functions. Other embodiments of lower layer triggered mobility to a cell supporting multiple TRPs / TAGs can be used without departing from the scope of the present disclosure.

[0126] In FIG. 6 In an example of, the procedure starts at step 610. At step 610, the gNB (or base station) 604 of cell A provides the LTM configuration of candidate cell B to the UE 602. Cell A is the serving cell. Cell B is associated with multiple TRPs / TAGs. In one embodiment, the number of multiple TRPs / TAGs can be 2. The TAG ID of each TAG is included in the LTM configuration of candidate cell B. The LTM configuration of candidate cell B can include a TA acquisition configuration. The TA acquisition configuration includes RRC configuration information for sending a random access preamble to cell B so that the gNB 606 to which cell B belongs can calculate a TA value to be used by the UE 602, e.g., in case of performing an LTM cell handover procedure to cell B. The LTM configuration of candidate cell B can include the configuration of cell B to be applied in case of performing an LTM cell handover procedure to cell B. The LTM configuration of candidate cell B can include a list of TCI states, where each TCI state is associated with one of the TAGs of cell B. In case cell A and cell B belong to different DUs of the same gNB, the gNB (or base station) 604 can obtain the configuration of cell B from the DU of cell B. In case cell A and cell B belong to different DUs of different gNBs, the gNB (or base station or CU) 604 of cell A can obtain the configuration of cell B from the gNB (or base station or CU) 606 of cell B. The LTM configuration of candidate cell B can include a L1 measurement configuration.

[0127] At step 620, the UE 602 confirms the RRC reconfiguration by sending an RRC reconfiguration complete message.

[0128] At step 630, the gNB (or base station) 604 to which cell A belongs sends a PDCCH order to the UE 602 to initiate the TA acquisition procedure with cell B. The PDCCH order includes information for transmitting a random access preamble to cell B (e.g., random access preamble index, SSB index, UL carrier (SUL or NUL)). Note that after sending the RRC reconfiguration complete message, the UE 602 performs L1 measurements of cell B and reports these to the gNB (or base station) 604 to which cell A belongs. Based on these measurements, the gNB 604 can identify the UL carrier and SSB index of cell B to include in the PDCCH order.

[0129] At step 640, the UE 602 transmits a random access preamble to cell B so that the gNB 606 to which cell B belongs can calculate a TA value to be used by the UE 602, e.g., if the LTM cell switch procedure is triggered to cell B.

[0130] In one embodiment, in the case where cell A and cell B belong to different DUs of the same gNB, the DU of cell B can determine the TA based on the received random access preamble and inform the DU of cell A of the determined TA. In one embodiment, the DU of cell B informs the DU of cell A of the TA upon receiving the random access preamble. In another embodiment, the DU of cell B informs the DU of cell A of the TA upon receiving a request for the TA from the DU of cell A, where the DU of cell A can request this information when it determines to switch to cell B.

[0131] In one embodiment, in the case where cell A and cell B belong to the same DU of the same gNB, the DU determines the TA based on the received random access preamble and informs the DU of cell A of the determined TA.

[0132] In one embodiment, in the case where cell A and cell B belong to different DUs of different gNBs, the DU of cell B can determine the TA based on the received random access preamble and inform the CU of cell B of the determined TA. The CU of cell B then sends this information to the CU of cell A, and the CU of cell A informs the DU of cell A of this information. In one embodiment, the DU of cell B can determine the TA based on the received random access preamble and inform the DU of cell A of the determined TA.

[0133] At step 650, the gNB (or base station) 604 of cell A decides to perform a cell handover to a target cell and sends a MAC CE triggering cell handover including a candidate configuration index of the target cell (i.e., cell B), a TA of cell B. In one embodiment, the TCI state identifier (identifying joint / UL TCI state / DL TCI state) of each of the multiple TRPs of cell B can be included in the MAC CE triggering cell handover.

[0134] At step 660, the UE 602 hands over to the target cell B and applies the configuration indicated by the candidate configuration index (at step 610, the UE can receive LTM configurations of multiple candidate cells and each configuration is identified by a candidate configuration index). In one embodiment, the UE 602 applies the TA received in the MAC CE triggering cell handover to the first TAG (e.g., one TAG corresponding to TAG index 0 can be predefined, or which one of the two TAGs is the first or second TAG) and starts the corresponding TAT. In another embodiment, the UE 602 applies the TA received in the MAC CE triggering cell handover to the second TAG (e.g., the TA corresponding to TAG index 1 can be predefined, or which one of the two TAGs is the first or second TAG) and starts the corresponding TAT. In one embodiment, the UE 602 can determine the TAG based on the SSB associated with the transmitted random access preamble (i.e., the SSB index indicated in the PDCCH order) in step 640. Different TRPs / TAGs of cell B can be associated with different SSBs, thus based on the SSB associated with the transmitted random access preamble (i.e., the SSB index indicated in the PDCCH order), the UE 602 can determine the TRP / TAG. The mapping between SSBs and TAGs of cell B can be indicated to the UE 602 in the configuration of cell B. Alternatively, the mapping between TCI states and TAGs of cell B can be indicated to the UE 602 in the configuration of cell B, where the RS associated with the TCI state is SSB.

[0135] At step 670, the UE 670 completes the LTM cell change procedure by sending an RRCReconfigurationComplete message to the target cell B. In one embodiment, if the target cell B is not associated with multiple TAGs and the valid TA of the target cell B is available to the UE 602 (e.g., received in the MAC CE that triggered the cell change or the UE 602 has estimated the TA), the UE 602 does not initiate RACH, performs LTM cell change without RACH, and uses the configured UL grant or dynamic UL grant to send a first UL PUSCH transmission. The first UL transmission includes the RRCReconfigurationComplete message. In one embodiment, if one uplink TCI state identifier is included in the MAC CE that triggered the cell change and the target cell B is associated with multiple TAGs and the valid TA of the TAG associated with the TCI state (identified by the uplink TCI state identifier) is available to the UE 602 (e.g., received in the MAC CE that triggered the cell change or the UE 602 has estimated the TA), the UE 602 does not initiate RACH, performs LTM cell change without RACH, and uses the configured UL grant or dynamic UL grant to send a first UL PUSCH transmission. The first UL transmission includes the RRCReconfigurationComplete message. In another embodiment, if two uplink TCI state identifiers are included in the MAC CE that triggered the cell change and the target cell B is associated with multiple TAGs and the valid TA of the TAG associated with the TCI state identified by at least one uplink TCI state identifier is available to the UE 602 (e.g., received in the MAC CE that triggered the cell change or the UE 602 has estimated the TA), the UE 602 does not initiate RACH, performs LTM cell change without RACH, and uses the configured UL grant or dynamic UL grant to send a first UL PUSCH transmission. The first UL transmission includes the RRCReconfigurationComplete message.

[0136] Although FIG. 6 One example procedure 600 for lower-layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown, various changes can be made FIG. 6 For example, while shown as a series of steps, various steps in FIG. 6 may overlap, occur in parallel, occur in a different order, occur any number of times, be omitted, or be replaced by other steps.

[0137] FIG. 7Another example procedure 700 for lower layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown, in accordance with an embodiment of the present disclosure. FIG. 7 Embodiments of the method shown in are for illustration only. FIG. 7 One or more components shown in can be implemented in specialized circuitry configured to perform the recited functions, or one or more components can be implemented by one or more processors executing instructions to perform the recited functions. Other embodiments of lower layer triggered mobility to a cell supporting multiple TRPs / TAGs can be used without departing from the scope of the present disclosure.

[0138] In FIG. 7 In an example of, the procedure starts at step 710. At step 710, the (gNB or base station) 704 of cell A provides the LTM configuration of candidate cell B to the UE 702. Cell A is the serving cell. Cell B is associated with multiple TRPs / TAGs. In one embodiment, the number of multiple TRPs / TAGs can be 2. The TAG ID of each TAG is included in the LTM configuration of candidate cell B. One of these TAGs / TAG IDs can be referred to as the first TAG (identified by TAG index 0) and the other can be referred to as the second TAG (identified by TAG index 1). The LTM configuration of candidate cell B can include a TA acquisition configuration. The TA acquisition configuration includes RRC configuration information for transmitting a random access preamble to cell B, so that the gNB 706 to which cell B belongs can calculate a TA value to be used by the UE 702, e.g., in case of performing an LTM cell handover procedure to cell B. The TAG ID / TAG index of the TAG associated with the early TA is included in the TA acquisition configuration. The LTM configuration of candidate cell B can include the configuration of cell B to be applied in case of performing an LTM cell handover procedure to cell B. The LTM configuration of candidate cell B can include a list of TCI states, where each TCI state is associated with one of the TAGs of cell B. In case cell A and cell B belong to different DUs of the same gNB, the gNB (or base station) 704 can obtain the configuration of cell B from the DU of cell B. In case cell A and cell B belong to different DUs of different gNBs, the gNB (or base station or CU) 704 of cell A can obtain the configuration of cell B from the gNB (or base station or CU) 706 of cell B. The LTM configuration of candidate cell B can include a L1 measurement configuration.

[0139] At step 720, the UE 702 confirms the RRC reconfiguration by sending an RRC reconfiguration complete message.

[0140] At step 730, the gNB (or base station) 704 to which cell A belongs sends a PDCCH order to the UE 702 to initiate the TA acquisition procedure with cell B. The PDCCH order includes information for transmitting a random access preamble to cell B (e.g., random access preamble index, SSB index, UL carrier (SUL or NUL)). Note that after sending the RRC reconfiguration complete message, the UE 702 performs L1 measurements of cell B and reports these to the gNB (or base station) 704 to which cell A belongs. Based on these measurements, the gNB 604 can identify the UL carrier and SSB index of cell B to include in the PDCCH order.

[0141] At step 740, the UE 702 transmits a random access preamble to cell B so that the gNB 706 to which cell B belongs can compute a TA value to be used by the UE 702, e.g., if the LTM cell switch procedure is triggered to cell B.

[0142] In one embodiment, in the case where cell A and cell B belong to different DUs of the same gNB, the DU of cell B can determine the TA based on the received random access preamble and inform the DU of cell A of the determined TA. In one embodiment, the DU of cell B informs the DU of cell A of the TA upon receiving the random access preamble. In another embodiment, the DU of cell B informs the DU of cell A of the TA upon receiving a request for the TA from the DU of cell A, where the DU of cell A can request this information when it determines to switch to cell B.

[0143] In one embodiment, in the case where cell A and cell B belong to the same DU of the same gNB, the DU determines the TA based on the received random access preamble and informs the DU of cell A of the determined TA.

[0144] In one embodiment, in the case where cell A and cell B belong to different DUs of different gNBs, the DU of cell B can determine the TA based on the received random access preamble and inform the CU of cell B of the determined TA. The CU of cell B then sends this information to the CU of cell A, and the CU of cell A informs the DU of cell A of this information. In one embodiment, the DU of cell B can determine the TA based on the received random access preamble and inform the DU of cell A of the determined TA.

[0145] At step 750, the gNB (or base station) 704 of cell A decides to perform a cell handover to a target cell and sends a MAC CE triggering the cell handover by including a candidate configuration index of the target cell (i.e., cell B), a TA of cell B. In one embodiment, one or more TCI state identifiers (identifying joint / UL TCI state / DL TCI state) of each of the multiple TRPs of cell B can be included in the MAC CE triggering the cell handover.

[0146] At step 760, the UE 702 hands over to the target cell B and applies the configuration indicated by the candidate configuration index (at step 710, the UE 702 can receive LTM configurations of multiple candidate cells and each configuration is identified by a candidate configuration index). In one embodiment, the UE 760 applies the TA received in the MAC CE triggering the cell handover to the TAG corresponding to the TAG ID included in the early TA configuration (or the TAG corresponding to the TAG index) and starts the corresponding TAT.

[0147] At step 770, the UE 702 completes the LTM cell change procedure by sending an RRCReconfigurationComplete message to the target cell B. In one embodiment, if the target cell B is not associated with multiple TAGs and the valid TA of the target cell B is available to the UE 702 (e.g., received in the MAC CE that triggered the cell change or the UE 702 has estimated the TA), the UE 702 does not initiate RACH, performs LTM cell change without RACH, and uses the configured UL grant or dynamic UL grant to send a first UL PUSCH transmission. The first UL transmission includes the RRCReconfigurationComplete message. In one embodiment, if one uplink TCI state identifier is included in the MAC CE that triggered the cell change and the target cell B is associated with multiple TAGs and the valid TA of the TAG associated with the TCI state (identified by the uplink TCI state identifier) is available to the UE 702 (e.g., received in the MAC CE that triggered the cell change or the UE 702 has estimated the TA), the UE 702 does not initiate RACH, performs LTM cell change without RACH, and uses the configured UL grant or dynamic UL grant to send a first UL PUSCH transmission. The first UL transmission includes the RRCReconfigurationComplete message. In one embodiment, if two uplink TCI state identifiers are included in the MAC CE that triggered the cell change and the target cell B is associated with multiple TAGs and the valid TA of the TAG associated with the TCI state identified by at least one uplink TCI state identifier is available to the UE 702 (e.g., received in the MAC CE that triggered the cell change or the UE has estimated the TA), the UE 702 does not initiate RACH, performs LTM cell change without RACH, and uses the configured UL grant or dynamic UL grant to send a first UL PUSCH transmission. The first UL transmission includes the RRCReconfigurationComplete message.

[0148] Although FIG. 7 One example procedure 700 for lower-layer triggered mobility to a cell supporting multiple TRPs / TAGs is shown, various changes can be made FIG. 7 For example, while shown as a series of steps, various steps in FIG. 7 may overlap, occur in parallel, occur in a different order, occur any number of times, be omitted, or be replaced by other steps.

[0149] FIG. 8Another example procedure 800 for lower layer triggered mobility to a cell supporting multiple TRPs / TAGs according to embodiments of the disclosure is shown. FIG. 7 Embodiments of the methods shown in the figures are for illustration only. FIG. 8 One or more components shown in the figures can be implemented in specialized circuitry configured to perform the functions described, or one or more components can be implemented by one or more processors executing instructions to perform the functions described. Other embodiments of lower layer triggered mobility to a cell supporting multiple TRPs / TAGs can be used without departing from the scope of the disclosure.

[0150] In FIG. 8 In an example of FIG. 8, the procedure starts at step 810. At step 810, the gNB (or base station) 804 of cell A provides the LTM configuration of candidate cell B to the UE 802. Cell A is the serving cell. Cell B is associated with multiple TRPs / TAGs. In one embodiment, the number of multiple TRPs / TAGs can be 2. The TAG ID of each TAG is included in the LTM configuration of candidate cell B. One of these TAGs / TAG IDs can be referred to as the first TAG (identified by TAG index 0) and the other can be referred to as the second TAG (identified by TAG index 1). The LTM configuration of candidate cell B can include a TA acquisition configuration. The TA acquisition configuration includes RRC configuration information for transmitting a random access preamble to cell B so that the gNB 806 to which cell B belongs can calculate a TA value to be used by the UE 802, e.g., in case of performing an LTM cell handover procedure to cell B. The LTM configuration of candidate cell B can include the configuration of cell B to be applied in case of performing an LTM cell handover procedure to cell B. The LTM configuration of candidate cell B can include a list of TCI states, where each TCI state is associated with one of the TAGs of cell B. In case cell A and cell B belong to different DUs of the same gNB, the gNB or base station can obtain the configuration of cell B from the DU of cell B. In case cell A and cell B belong to different DUs of different gNBs, the gNB (or base station or CU) 804 of cell A can obtain the configuration of cell B from the gNB (or base station or CU) 806 of cell B. The LTM configuration of candidate cell B can include a L1 measurement configuration.

[0151] At step 820, the UE 802 confirms the RRC reconfiguration by sending an RRC reconfiguration complete message.

[0152] In step 830, the gNB (or base station) 804 of cell A sends a PDCCH command to the UE 802 to initiate a TA acquisition procedure with cell B. The PDCCH command includes information for sending a random access preamble to cell B (e.g., random access preamble index, SSB index, UL carrier (SUL or NUL)). Note that after sending the RRC reconfiguration complete message, the UE 802 performs L1 measurements of cell B and reports these to the gNB (or base station) 802 of cell A. Based on these measurements, the gNB 804 can identify the UL carrier and SSB index of cell B to be included in the PDCCH command. In one embodiment, the TAG ID / TAG index of the TAG associated with the earlier TA is included in the PDCCH command.

[0153] In step 840, UE 802 sends a random access preamble to cell B, enabling gNB 806, to which cell B belongs, to calculate the TA value to be used by the UE, for example, if an LTM cell handover process is triggered to cell B.

[0154] In one embodiment, when cell A and cell B belong to different DUs within the same gNB, the DU of cell B can determine the TA based on the received random access preamble and notify the determined TA to the DU of cell A. In one embodiment, the DU of cell B notifies the TA to the DU of cell A upon receiving the random access preamble. In another embodiment, the DU of cell B, upon receiving a request for the TA from the DU of cell A, notifies the DU of cell A of the TA, wherein the DU of cell A can request this information when the DU or cell A determines to hand over to cell B.

[0155] In one embodiment, when cell A and cell B belong to the same DU of the same gNB, the DU determines the TA based on the received random access preamble and notifies the DU of cell A of the determined TA.

[0156] In one embodiment, when cell A and cell B belong to different DUs of different gNBs, the DU of cell B can determine the TA based on the received random access preamble and notify the CU of cell B of the determined TA. Then, the CU of cell B sends this information to the CU of cell A, and the CU of cell A notifies the DU of cell A of the determined TA. In one embodiment, the DU of cell B can determine the TA based on the received random access preamble and notify the DU of cell A of the determined TA.

[0157] In step 850, the gNB (or base station) 804 of cell A determines to perform a cell handover to the target cell and sends a MAC CE that triggers the cell handover by including the candidate configuration index of the target cell (i.e., cell B) and the TA of cell B. In one embodiment, one or more TCI status identifiers (identifying the joint / UL TCI status / DL TCI status) of each of the plurality of TRPs of cell B may be included in the MAC CE that triggers the cell handover.

[0158] In step 860, UE 802 switches to target cell B and applies the configuration indicated by the candidate configuration index (in step 810, UE 802 may receive LTM configurations for multiple candidate cells, and each configuration is identified by a candidate configuration index). In one embodiment, UE 802 applies the TA received in the MAC CE that triggers cell handover to the TAG corresponding to the TAG ID included in the PDCCH command (or the TAG corresponding to the TAG index) and initiates the corresponding TAT.

[0159] In step 870, UE 802 completes the LTM cell handover process by sending an RRCReconfigurationComplete message to target cell B. In one embodiment, if target cell B is not associated with multiple TAGs, and a valid TAG for target cell B is available to UE 802 (e.g., received in the MAC CE that triggered the cell handover, or UE 802 has already estimated the TAG), then UE 802 does not initiate a RACH, performs an LTM cell handover without a RACH, and sends a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes the RRCReconfigurationComplete message. In one embodiment, if an uplink TCI state identifier is included in the MAC CE that triggers the cell handover, and the target cell B is associated with multiple TAGs, and the valid TA for the TAG associated with the TCI state (identified by the uplink TCI state identifier) ​​is available to UE 802 (e.g., received in the MAC CE that triggers the cell handover or UE 802 has already estimated the TA), then UE 802 does not initiate a RACH, performs an LTM cell handover without RACH, and sends a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes an RRCReconfigurationComplete message. In one embodiment, if two uplink TCI state identifiers are included in the MAC CE that triggers the cell handover, and target cell B is associated with multiple TAGs, and a valid TA for the TAG associated with the TCI state identified by at least one uplink TCI state identifier is available to UE 802 (e.g., received in the MAC CE that triggers the cell handover or UE 802 has estimated the TA), then UE 802 does not initiate a RACH, performs an LTM cell handover without RACH, and sends a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes an RRCReconfigurationComplete message.

[0160] although FIG. 8 An example procedure 800 for lower-layer triggered mobility to a cell supporting multiple TRP / TAGs is shown, but it is possible to... FIG. 8 Various changes were made. For example, although it is shown as a series of steps, FIG. 8 The steps in the process can overlap, occur in parallel, occur in different orders, occur any number of times, be omitted, or be replaced by other steps.

[0161] FIG. 9Another example process 900 for lower-layer triggered mobility to a cell supporting multiple TRP / TAGs, according to an embodiment of this disclosure, is shown. FIG. 9 The embodiments of the methods shown are for illustrative purposes only. FIG. 9 One or more components shown may be implemented in a dedicated circuit configured to perform the function, or one or more components may be implemented by one or more processors that execute instructions to perform the function. Other embodiments of lower-layer triggered mobility supporting multiple TRP / TAG cells may be used without departing from the scope of this disclosure.

[0162] exist FIG. 9 In the example, the process begins at step 910. At step 910, the gNB (or base station) 904 of cell A provides the LTM configuration of candidate cell B to the UE 902. Cell A is the serving cell. Cell B is associated with multiple TRPs / TAGs. In one embodiment, the number of TRPs / TAGs can be two. The TAG ID of each TAG is included in the LTM configuration of candidate cell B. One of these TAG / TAG IDs can be referred to as the first TAG (identified by TAG index 0), and the other can be referred to as the second TAG (identified by TAG index 1). The LTM configuration of candidate cell B can include a TA acquisition configuration. The TA acquisition configuration includes RRC configuration information for sending a random access preamble to cell B, enabling the gNB 906 to which cell B belongs to calculate the TA value to be used by the UE 902, for example, in the case of performing an LTM cell handover procedure on cell B. The LTM configuration of candidate cell B can include the configuration of cell B to be applied in the case of performing an LTM cell handover procedure on cell B. The LTM configuration of candidate cell B may include a list of TCI states, where each TCI state is associated with one of cell B's TAGs. If cell A and cell B belong to different DUs within the same gNB, the gNB or base station can obtain the configuration of cell B from the DU of cell B. If cell A and cell B belong to different DUs within different gNBs, the gNB (or base station or CU) 904 of cell A can obtain the configuration of cell B from the gNB (or base station or CU) 906 of cell B. The LTM configuration of candidate cell B may include an L1 measurement configuration.

[0163] In step 920, UE 902 confirms the RRC reconfiguration by sending an RRC reconfiguration completion message.

[0164] In step 930, the gNB (or base station) 904 of cell A sends a PDCCH command to UE 902 to initiate a TA acquisition procedure with cell B. The PDCCH command includes information required to send the random access preamble to cell B (e.g., random access preamble index, SSB index, UL carrier (SUL or NUL)). Note that after sending the RRC reconfiguration complete message, UE 902 performs L1 measurements of cell B and reports these to the gNB (or base station) 904 of cell A. Based on these measurements, gNB 904 can identify the UL carrier and SSB index of cell B to be included in the PDCCH command.

[0165] In step 940, UE 902 sends a random access preamble to cell B, enabling gNB 906, to which cell B belongs, to calculate the TA value to be used by UE 902, for example, if an LTM cell handover process is triggered to cell B.

[0166] In one embodiment, when cell A and cell B belong to different DUs within the same gNB, the DU of cell B can determine the TA based on the received random access preamble and notify the determined TA to the DU of cell A. In one embodiment, the DU of cell B notifies the TA to the DU of cell A upon receiving the random access preamble. In another embodiment, the DU of cell B, upon receiving a request for the TA from the DU of cell A, notifies the DU of cell A of the TA, wherein the DU of cell A can request this information when it determines to hand over to cell B.

[0167] In one embodiment, when cell A and cell B belong to the same DU of the same gNB, the DU determines the TA based on the received random access preamble and notifies the DU of cell A of the determined TA.

[0168] In one embodiment, when cell A and cell B belong to different DUs of different gNBs, the DU of cell B can determine the TA based on the received random access preamble and notify the CU of cell B of the determined TA. Then, the CU of cell B sends this information to the CU of cell A, and the CU of cell A notifies the DU of cell A of the information.

[0169] In step 950, the gNB or base station of cell A decides to perform a cell handover to the target cell and sends a MAC CE that triggers the cell handover by including the candidate configuration index of the target cell (i.e., cell B) and the TA of cell B.

[0170] At step 960, UE 902 switches to target cell B and applies the configuration indicated by the candidate configuration index (at step 910, UE 902 may receive LTM configurations for multiple candidate cells, each identified by a candidate configuration index). In this embodiment, the UE applies the TA received in the MAC CE that triggered the cell handover to a TAG, which is configured to be associated with the joint / UL TCI state indicated in the MAC CE that triggered the cell handover, and initiates the corresponding TAT. In step 910, the mapping from TCI state to TAG is received. The MAC CE may include a TCI state ID field. The LTM configuration of target cell B received in step 910 may include the field / parameter unifiedTCI-StateType. unifiedTCI-StateType may be set to either "single" or "joint". If unifiedTCI-StateType is set to "joint", the TCI state ID field indicates the joint TCI state. If unifiedTCI-StateType is set to "single", the TCI state ID field indicates the DL TCI state. The MAC CE may include a UL TCI state ID field. The LTM configuration of the target cell B received in step 910 may include the field / parameter unifiedTCI-StateType. unifiedTCI-StateType can be set to either "Individual" or "Combined". If unifiedTCI-StateType is set to "Individual", the UL TCI State ID field indicates the UL TCI state.

[0171] In one embodiment, if `unifiedTCI-StateType` is set to "Single" in the LTM configuration of target cell B, UE 902 will apply the TA received in the MAC CE that triggered the cell handover to a TAG configured to be associated with the UL TCI state indicated in the MAC CE that triggered the cell handover (i.e., the TCI state indicated by the UL TCI state ID field) and initiate the corresponding TAT. The list of UL TCI states is configured by the list `ltm-UL-TCI-StateToAddModList` in the LTM configuration of target cell B. The UL TCI states in the list are identified by `TCI-UL-StateId` in `ltm-UL-TCI-StateToAddModList`. The TAG associated with the UL TCI state (e.g., the first or second TAG) is also indicated in `ltm-UL-TCI-StatesToAddModList`. The UL TCI state ID is set to the `TCI-UL-StateId` of the UL TCI state.

[0172] In one embodiment, if `unifiedTCI-StateType` is set to "Unified" in the LTM configuration of target cell B, UE 902 will apply the TA received in the MAC CE that triggered the cell handover to a TAG configured to be associated with the joint TCI state indicated in the MAC CE that triggered the cell handover (i.e., the TCI state indicated by the TCI state ID field), and initiate the corresponding TAT. The list of joint TCI states is configured by the list `ltm-DL-OrJointTCI-StateToAddModList` in the LTM configuration of target cell B. Each joint TCI state in the list is identified by `TCI-StateId` in `ltm-DL-OrJointTCI-StateToAddModList`. The TAG associated with the joint TCI state (e.g., the first or second TAG) is also in `ltm-DL-OrJointTCI-StateToAddModList`. The TCI state ID is set to the TCI-StateId of the joint TCI state.

[0173] In one embodiment, if the UL TCI State ID field is included in the MAC CE that triggers cell handover, then UE902 will apply the TA received in the MAC CE that triggers cell handover to a TAG that is configured to be associated with the UL TCI state indicated in the MAC CE that triggers cell handover (i.e., the TCI state indicated by the UL TCI State ID field), and initiate the corresponding TAT (i.e., the TAT of the TAG associated with the UL TCI state (i.e., the TCI state indicated by the UL TCI State ID field).

[0174] In one embodiment, if the UL TCI state ID field is not included in the MAC CE that triggered the cell handover, the UE 902 will apply the TA received in the MAC CE that triggered the cell handover to a TAG that is configured to be associated with the joint TCI state indicated in the MAC CE that triggered the cell handover (i.e., the TCI state indicated by the TCI state ID field in the MAC CE that triggered the cell handover), and initiate the corresponding TAT (i.e., the TAT of the TAG associated with the UL TCI state (i.e., the TCI state indicated by the TCI state ID field in the MAC CE that triggered the cell handover).

[0175] In step 970, UE 902 completes the LTM cell handover process by sending an RRCReconfigurationComplete message to target cell B. In one embodiment, if target cell B is not associated with multiple TAGs, and a valid TAG for target cell B is available to UE 902 (e.g., received in the MAC CE that triggered the cell handover, or UE 902 has already estimated the TAG), then UE 902 does not initiate a RACH, performs an LTM cell handover without a RACH, and sends a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes the RRCReconfigurationComplete message. In one embodiment, if an uplink TCI state identifier is included in the MAC CE that triggers the cell handover, and the target cell B is associated with multiple TAGs, and the valid TA for the TAG associated with the TCI state (identified by the uplink TCI state identifier) ​​is available to UE 902 (e.g., received in the MAC CE that triggers the cell handover, or UE 902 has already estimated the TA), then UE 902 does not initiate a RACH, performs an LTM cell handover without a RACH, and sends a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes an RRCReconfigurationComplete message.

[0176] In one embodiment, if two uplink TCI state identifiers are included in the MAC CE that triggers cell handover, and target cell B is associated with multiple TAGs, and a valid TA for the TAG associated with the TCI state identified by at least one uplink TCI state identifier is available to UE 902 (e.g., received in the MAC CE that triggers cell handover or UE 902 has estimated the TA), then UE 902 does not initiate RACH, performs LTM cell handover without RACH, and sends a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes an RRCReconfigurationComplete message.

[0177] although FIG. 9 An example procedure 900 for lower-layer triggered mobility to a cell supporting multiple TRP / TAGs is shown, but it is possible to... FIG. 9 Various changes were made. For example, although it is shown as a series of steps, FIG. 9 The steps in the process can overlap, occur in parallel, occur in different orders, occur any number of times, be omitted, or be replaced by other steps.

[0178] FIG. 10Another example process 1000 for lower-layer triggered mobility to a cell supporting multiple TRP / TAGs, according to an embodiment of this disclosure, is shown. FIG. 10 The embodiments of the methods shown are for illustrative purposes only. FIG. 10 One or more components shown may be implemented in a dedicated circuit configured to perform the function, or one or more components may be implemented by one or more processors that execute instructions to perform the function. Other embodiments of lower-layer triggered mobility supporting multiple TRP / TAG cells may be used without departing from the scope of this disclosure.

[0179] exist FIG. 10 In the example, the process begins at step 1010. In step 1010, the gNB (or base station) 1004 of cell A provides the LTM configuration of candidate cell B to UE 1002. Cell A is the serving cell. Cell B is associated with multiple TRPs / TAGs. In one embodiment, the number of multiple TRPs / TAGs can be 2. The TAG ID of each TAG is included in the LTM configuration of candidate cell B. One of these TAG / TAG IDs can be referred to as the first TAG (identified by TAG index 0), and the other can be referred to as the second TAG (identified by TAG index 1). The LTM configuration of candidate cell B can include TA acquisition configuration. The TA acquisition configuration includes RRC configuration information for sending a random access preamble to cell B, such that the gNB 1006 to which cell B belongs can calculate the TA value to be used by UE 1002, for example, in the case of performing an LTM cell handover procedure on cell B. The LTM configuration of candidate cell B can include the configuration of cell B to be applied in the case of performing an LTM cell handover procedure on cell B. The LTM configuration of candidate cell B may include a list of TCI states, where each TCI state is associated with one of cell B's TAGs. If cell A and cell B belong to different DUs within the same gNB, gNB (or base station) 1004 can obtain cell B's configuration from cell B's DU. If cell A and cell B belong to different DUs within different gNBs, gNB (or base station or CU) 1004 of cell A can obtain cell B's configuration from gNB (or base station or CU) 1006 of cell B. The LTM configuration of candidate cell B may include an L1 measurement configuration.

[0180] In step 1020, UE 1002 confirms the RRC reconfiguration by sending an RRC reconfiguration completion message.

[0181] In step 1030, UE 1002 estimates the TA of cell B based on the difference between the arrival of DL signals at cell A and cell B and the TA of cell A.

[0182] In step 1040, the gNB (or base station) 1004 of cell A decides to perform a cell handover to the target cell and sends a MAC CE that triggers the cell handover by including the candidate configuration index of the target cell (i.e., cell B).

[0183] At step 1050, UE 1002 switches to target cell B and applies the configuration indicated by the candidate configuration index (at step 1010, UE 1002 may receive LTM configurations of multiple candidate cells, and each configuration is identified by the candidate configuration index).

[0184] In one embodiment, UE 1002 applies the estimated TA to the first TAG of cell B (i.e., the TAG corresponding to TAG index 0) and initiates the corresponding TAT. UE 1002 does not initiate RACH, performs LTM handover without RACH, and uses the configured UL grant or dynamic UL grant to transmit the first UL PUSCH transmission. The first UL transmission includes an RRCReconfigurationComplete message.

[0185] In another embodiment, UE 1002 applies the estimated TA to the second TAG of cell B (i.e., the TAG corresponding to TAG index 1) and initiates the corresponding TAT. UE 1002 does not initiate RACH, performs LTM cell handover without RACH, and uses the configured UL grant or dynamic UL grant to transmit the first UL PUSCH transmission. The first UL transmission includes an RRCReconfigurationComplete message.

[0186] In another embodiment, UE 1002 applies the estimated TA to the TAG of cell B indicated in the early TA configuration and initiates the corresponding TAT. UE 1002 does not initiate RACH, performs LTM cell handover without RACH, and uses the configured UL grant or dynamic UL grant to transmit the first UL PUSCH transmission. The first UL transmission includes an RRCReconfigurationComplete message.

[0187] In another embodiment, UE 1002 applies the estimated TA to the TAG of cell B, which is configured to be associated with the joint / UL TCI state indicated in the cell handover command, and initiates the corresponding TAT. The UE does not initiate a RACH, performs an LTM cell handover without a RACH, and sends a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes an RRCReconfigurationComplete message.

[0188] In another embodiment, if a RS (SSB or CSI-RS) is used for TA estimation, and if the RS is configured to be in TCI state and indicates TCI state in the LTM handover MAC CE, then UE 1002 uses the estimated TA for the TAG configured for the TCI state and initiates the corresponding TAT. The UE does not initiate RACH, performs an LTM cell handover without RACH, and sends a first UL PUSCH transmission using the configured UL grant or dynamic UL grant. The first UL transmission includes an RRCReconfigurationComplete message. Otherwise, UE 1002 may initiate RACH toward target cell B.

[0189] although FIG. 10 An example procedure 1000 for lower-layer triggered mobility to a cell supporting multiple TRP / TAGs is shown, but it is possible to modify the following: FIG. 10 Various changes were made. For example, although it is shown as a series of steps, FIG. 10 The steps in the process can overlap, occur in parallel, occur in different orders, occur any number of times, be omitted, or be replaced by other steps.

[0190] MAC CE triggers cell handover, instructing the UE to apply the TA of the source cell during LTM cell handover to an LTM candidate cell with multiple TRPs. In one embodiment, in step 1, the gNB or base station (such as...) of the serving cell (cell A) FIG. 1 BS 102) determines to perform a cell handover to the target cell and sends a candidate configuration index to the UE (such as) including the target cell (i.e., cell B). FIG. 1 UE 116) sends a MAC CE that triggers cell handover. In one embodiment, the MAC CE that triggers cell handover may instruct the UE to apply the TA of cell A. In one embodiment, one or more TCI status identifiers (identifying the joint / UL TCI status / DL TCI status) of each of the plurality of TRPs of cell B may be included in the MAC CE that triggers cell handover.

[0191] In step 2, the UE switches to target cell B and applies the configuration indicated by the candidate configuration index (in step 1, the UE may receive LTM configurations of multiple candidate cells, and each configuration is identified by the candidate configuration index).

[0192] The MAC CE that triggered the cell handover instructed the UE to apply the TA of cell A. The UE performed the following operations:

[0193] Scenario 1: Cell A is associated with a TAG. Cell B is associated with a TAG. In this case, the UE applies the TAG of cell A to the UL transmission to cell B. The UL transmission and the joint / UL TCI state indicated in the MAC CE that triggered the cell handover are QCL (quasi-co-located).

[0194] Scenario 2: Cell A is associated with one TAG. Cell B is associated with two TAGs. In this case, the UL transmission and the joint / UL TCI state are QCL, which are associated with the same TAG as the TAG of Cell A, and the UE applies the TA of Cell A. The UE applies the TA of Cell A to the UL transmission associated with the TAG that is the same as the TAG of Cell A.

[0195] In one embodiment, if the MAC CE triggering the cell handover contains a joint / uplink TCI state identifier, and the target cell B is associated with multiple TAGs, and the TAG associated with the TCI state (identified by the uplink TCI state identifier) ​​is the same as the TAG of cell A, then the UE does not initiate a RACH, performs an LTM cell handover without RACH, and transmits a first UL PUSCH using the configured UL grant or dynamic UL grant. The first UL transmission includes an RRCReconfigurationComplete message.

[0196] In one embodiment, if the MAC CE that triggers cell handover contains a joint / uplink TCI status identifier, and the target cell B is associated with multiple TAGs, and the TAG associated with the TCI status (identified by the uplink TCI status identifier) ​​is different from the TAG of cell A, then the UE initiates RACH to cell B.

[0197] In one embodiment, if the MAC CE triggering the cell handover contains two joint / uplink TCI state identifiers, and the target cell B is associated with multiple TAGs, and the TAG associated with the TCI state identified by at least one uplink TCI state identifier is the same as the TAG of cell A, then the UE does not initiate RACH, performs LTM cell handover without RACH, and transmits the first UL PUSCH using the configured UL grant or dynamic UL grant. The first UL transmission includes the RRCReconfigurationComplete message.

[0198] Scenario 3: Cell A is associated with two tags. Cell B is associated with one tag. In this case, the UE applies the TA of cell A corresponding to the tag of cell B to the UL transmission to cell B. The UL transmission and the joint / UL TCI state indicated in the MAC CE that triggers the cell handover are QCL.

[0199] Scenario 4: Cell A is associated with two tags. Cell B is associated with two tags. In this case, the UL transmission's joint / UL TCI state associated with the tag that is the same as the tag in cell A is QCL, and the UE applies the TA of cell A corresponding to that tag.

[0200] In one embodiment, if the MAC CE triggering the cell handover contains a joint / uplink TCI state identifier, and the target cell B is associated with multiple TAGs, and the TAG associated with the TCI state (identified by the uplink TCI state identifier) ​​is the same as the TAG of cell A, then the UE does not initiate RACH, performs a RACH-free cell handover, and transmits the first UL PUSCH using the configured UL grant or dynamic UL grant. The first UL transmission includes the RRCReconfigurationComplete message.

[0201] In one embodiment, if the MAC CE triggering the cell handover contains two joint / uplink TCI state identifiers, and the target cell B is associated with multiple TAGs, and the TAG associated with the TCI state identified by at least one uplink TCI state identifier is the same as the TAG of cell A, then the UE does not initiate RACH, performs LTM cell handover without RACH, and transmits the first UL PUSCH using the configured UL grant or dynamic UL grant. The first UL transmission includes the RRCReconfigurationComplete message.

[0202] In existing wireless communication systems supporting LTM, a UE receives an RRCReconfiguration message including RRCReconfiguration of one or more candidate LTM cells, the UE receives an LTM cell handover command MAC CE for the candidate LTM cells, and the UE applies the indicated RRCReconfiguration for the candidate LTM cells. The RRCReconfiguration includes dedicatedSIB1-Delivery. Upon receiving SIB1, the UE performs an action to process SIB1. This results in the generation and submission of an SI request. Additionally, the RRCReconfiguration message includes ltm-Config: the UE performs an LTM configuration procedure. This results in the generation and submission of a ReconfigurationComplete message. However, according to the above operations, ReconfigurationComplete will be delayed due to the SI request message in the SRB buffer. This disclosure provides a process to overcome this problem.

[0203] FIG. 11 An example process 1100 for lower-layer triggered mobility is shown according to an embodiment of the present disclosure. FIG. 11 The embodiments of the methods shown are for illustrative purposes only. FIG. 11 One or more components shown may be implemented in a dedicated circuit configured to perform the function, or one or more components may be implemented by one or more processors that execute instructions to perform the function. Other embodiments of lower-layer triggered mobility supporting multiple TRP / TAG cells may be used without departing from the scope of this disclosure.

[0204] exist FIG. 11 In the example, the process begins at step 1110. At step 1110, the gNB (or base station) 1102 of cell A provides the UE 1102 with the configuration of LTM candidate cell B. The configuration of LTM candidate cell B may include L1 measurement configuration. Cell A is the serving cell and belongs to the MCG, and cell B is a candidate PCell or SpCell. The RRCReconfigurationIE for cell B is included in the RRCReconfiguration message received from the gNB (or base station) 1104 of cell A. The RRCReconfigurationIE for cell B includes dedicatedSIB1-Delivery and ltm-Config IEs.

[0205] At step 1120, UE 1102 acknowledges the RRC reconfiguration received from gNB (or base station) 1104 of cell A by transmitting an RRC reconfiguration completion message.

[0206] At step 1130, after transmitting the RRC reconfiguration complete message, UE 1102 performs L1 measurements of cell B and reports these to the gNB (or base station) 1102 to which cell A belongs.

[0207] At step 1140, based on L1 measurement, gNB (or base station) 1104 of cell A decides to perform LTM cell handover to the target cell (i.e., cell B) and sends a MAC CE that triggers LTM cell handover by including the candidate configuration index of the target cell (i.e., cell B).

[0208] In step 1150, UE 1102 switches to target cell B and applies the configuration indicated by the candidate configuration index (i.e., the RRCReconfiguration IE of cell B received in step 1) (in step 1110, the UE may receive LTM configurations of multiple candidate cells, and each configuration is identified by the candidate configuration index).

[0209] In one embodiment, if the applied RRCReconfiguration is associated with an MCG (i.e., target cell B belongs to an MCG) and includes ltm-Config and dedicatedSIB1-Delivery, the UE initiates a request (if needed) to obtain the required SIBs for cell B only after the LTM execution toward the target SpCell is successfully completed (step 1180). dedicatedSIB1-Delivery includes the SIB1s of cell B and indicates which SIBs of cell B are periodically broadcast and which are not. For SIBs that are not periodically broadcast and are required in the RRC_CONNECTED state, the UE can send an SI request message to cell B. In this embodiment, the UE processes dedicatedSIB1-Delivery before ltm-Config. If the UE does not have a valid TA for the target cell, the UE performs a random access procedure for target cell B. The UE completes the LTM cell handover procedure by sending an RRCReconfigurationComplete message to target cell B. If the UE has already performed the RA procedure, the UE considers the LTM execution to have been successfully completed when the random access procedure is successfully completed. For LTM without RACH, the UE considers LTM execution to have successfully completed when it determines that the network has successfully received its first UL data (i.e., a PUSCH transmission using configured UL grant or dynamic UL grant at step 1160). The UE determines successful reception of its first UL data by receiving the PDCCH of the UE's C-RNTI in the addressing target cell at step 1170, which schedules new transmissions (e.g., new UL transmissions or new DL transport blocks / transmissions) following the first UL data.

[0210] In an alternative embodiment, if RRCReconfiguration is associated with MCG and includes ltm-Config and dedicatedSIB1-Delivery, the UE processes ltm-Config before processing dedicatedSIB1-Delivery in the applied RRCReconfiguration.

[0211] although FIG. 11 An example procedure for mobility triggered by a lower layer is shown, but it is possible to modify it further. FIG. 11 Various changes were made. For example, although it is shown as a series of steps, FIG. 11 The steps in the process can overlap, occur in parallel, occur in different orders, occur any number of times, be omitted, or be replaced by other steps.

[0212] FIG. 12An example method 1200 for lower-layer triggered mobility to a cell supporting multiple TRPs is illustrated according to an embodiment of the present disclosure. FIG. 12 The embodiments of the methods shown are for illustrative purposes only. FIG. 12 One or more components shown may be implemented in a dedicated circuit configured to perform the function, or one or more components may be implemented by one or more processors that execute instructions to perform the function. Other embodiments of lower-layer triggered mobility supporting multiple TRPs may be used without departing from the scope of this disclosure.

[0213] exist FIG. 12 In the example, the method begins at step 1210. In step 1210, such as... FIG. 1 UE 116 receives an RRC reconfiguration message including the configuration of the LTM candidate cell. In step 1220, the UE receives an LTM cell handover command instructing the UE to perform an LTM cell handover to the LTM candidate cell. In step 1230, the UE determines whether the LTM candidate cell belongs to an MCG. In step 1240, the UE determines whether the configuration of the LTM candidate cell includes SIB1. If the LTM candidate cell belongs to an MCG and the LTM candidate cell configuration includes SIB1, the method proceeds to step 1250. Otherwise, the method ends. In step 1250, after successfully completing the LTM cell handover to the LTM candidate cell, the UE sends an SI request to the LTM candidate cell.

[0214] although FIG. 12 An example method 1200 for lower-layer triggered mobility to a cell supporting multiple TRPs is shown, but it is possible to... FIG. 12 Various changes were made. For example, although it is shown as a series of steps, FIG. 12 The steps in the process can overlap, occur in parallel, occur in different orders, occur any number of times, be omitted, or be replaced by other steps.

[0215] Any of the above-described variant embodiments can be used independently or in combination with at least one other variant embodiment. The flowcharts above illustrate example methods that can be implemented according to the principles of this disclosure, and various changes can be made to the methods shown in the flowcharts herein. For example, although shown as a series of steps, the individual steps in each figure may overlap, occur in parallel, occur in different orders, or occur multiple times. In another example, steps may be omitted or replaced with other steps.

[0216] Although this disclosure has been described using exemplary embodiments, various changes and modifications may be suggested to those skilled in the art. This disclosure is intended to cover such changes and modifications that fall within the scope of the appended claims. Nothing described in this application should be construed as implying that any particular element, step, or function is an essential element that must be included within the scope of the claims. The scope of the subject matter for which patent protection is sought is defined by the claims.

Claims

1. A method performed by a user equipment (UE) in a wireless communication system, the method comprising: Receive mobility (LTM) configuration information triggered by Layer 1 (L1) / Layer 2 (L2) of the cell; Receive an LTM cell handover command instructing the UE to perform an LTM cell handover; The application is a Radio Resource Control (RRC) reconfiguration message in the LTM configuration information identified by the candidate configuration index included in the LTM cell handover command; and When an RRC reconfiguration message is associated with a primary cell group (MCG) and includes System Information Block 1 (SIB1), a request to obtain one or more required System Information Blocks (SIBs) is initiated after the random access procedure or LTM cell handover to the cell is completed.

2. The method according to claim 1, wherein, The LTM cell handover is performed as an LTM cell handover without a random access channel (RACH).

3. The method according to claim 2, further comprising: The handover of the LTM cell is considered complete when a Physical Downlink Control Channel (PDCCH) is received after the first uplink transmission to the cell and the PDCCH schedules a new transmission.

4. The method according to claim 3, wherein, The PDCCH is associated with the UE's Cell Radio Network Temporary Identifier (C-RNTI).

5. The method according to claim 1, wherein, The LTM configuration information includes the Transmission Configuration Indicator (TCI) status and the mapping information of the Timing Advance Group (TAG).

6. The method according to claim 5, wherein, The LTM cell handover command includes information indicating the timing advance value and information indicating the TCI state in the TCI state.

7. The method according to claim 6, further comprising: Based on the mapping information, the timing advance value is applied to the TAG associated with the indicated TCI state.

8. A user equipment (UE) in a wireless communication system, the UE comprising: transceiver; and The controller is configured to: The transceiver receives Layer 1 (L1) / Layer 2 (L2) triggered mobility (LTM) configuration information of the cell. The transceiver receives an LTM cell handover command instructing the UE to perform an LTM cell handover. The application uses the Radio Resource Control (RRC) reconfiguration message in the LTM configuration information identified by the candidate configuration index included in the LTM cell handover command, and When an RRC reconfiguration message is associated with a primary cell group (MCG) and includes System Information Block 1 (SIB1), a request to obtain one or more required System Information Blocks (SIBs) is initiated after the random access procedure or after the LTM cell handover to the cell is completed.

9. The UE according to claim 8, wherein, The LTM cell handover is performed as an LTM cell handover without a random access channel (RACH).

10. The UE according to claim 9, wherein, The controller is also configured to consider the LTM cell handover complete based on the determination that a physical downlink control channel (PDCCH) is received after the first uplink transmission to the cell and that the PDCCH schedules a new transmission.

11. The UE according to claim 10, wherein, The PDCCH is associated with the UE's Cell Radio Network Temporary Identifier (C-RNTI).

12. The UE according to claim 8, wherein, The LTM configuration information includes the Transmission Configuration Indicator (TCI) status and the mapping information of the Timing Advance Group (TAG).

13. The UE according to claim 12, wherein, The LTM cell handover command includes information indicating the timing advance value and information indicating the TCI state in the TCI state.

14. The UE according to claim 13, wherein, The controller is also configured to apply the timing advance value to a TAG associated with the indicated TCI state based on the mapping information.

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