Timing advance management in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Methods and apparatus for timing advance management for multi-TRP and beam management in a wireless communication system. A method of a UE includes: receiving a second TAG ID and a PDCCH command associated with a second BS from a first BS; in response to receiving the PDCCH command, initiating a CFRA process; transmitting an RA preamble to a second BS; receiving, for the second BS, a TAC included in the RAR or the MAC CE; and applying the TAC and starting a second time alignment timer corresponding to a second TAG ID associated with the second BS.

Description

Technical Field

[0001] The present disclosure relates generally to wireless communication systems, and more particularly to timing advance management for multiple transmit receive points (TRPs) and beam management in wireless communication systems. Background Art

[0002] 5G mobile communication technology defines a wide frequency band, making high transmission rates and new services possible, and can be implemented not only in "below 6 GHz" frequency bands such as 3.5 GHz, but also in "above 6 GHz" frequency bands called millimeter waves (mmWave) including 28 GHz and 39 GHz. In addition, it has been considered to implement 6G mobile communication technology (called super 5G system) in terahertz frequency bands (e.g., 95 GHz to 3 THz frequency bands) in order to achieve a transmission rate fifty times faster than 5G mobile communication technology and an ultra-low latency one-tenth of 5G mobile communication technology.

[0003] At the beginning of the development of 5G mobile communication technology, in order to support services and meet performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC), there is ongoing standardization on the following items: beamforming and massive MIMO for mitigating radio wave path loss and increasing radio wave transmission distance in millimeter waves, parameter sets supporting dynamic operations for efficient utilization of millimeter wave resources and time slot formats (e.g., operating multiple subcarrier spacings), initial access technology for supporting multi-beam transmission and broadband, definition and operation of BWP (bandwidth part), new channel coding methods (such as LDPC (low-density parity check) codes for large-scale data transmission and polar codes for highly reliable transmission of control information), L2 preprocessing, and network slicing for providing dedicated networks dedicated to specific services.

[0004] Currently, in view of the services to be supported by 5G mobile communication technology, discussions are ongoing on improvements and performance enhancements of initial 5G mobile communication technology, and there is already physical layer standardization on technologies such as the following: V2X (Vehicle to Everything), for assisting driving determination of autonomous vehicles based on information about the location and status of the vehicle sent by the vehicle and for enhancing user convenience; NR-U (New Radio Unlicensed), for system operation that is intended to comply with various regulatory-related requirements in unlicensed bands; NR UE power saving; Non-Terrestrial Network (NTN), which is UE satellite direct communication for providing coverage in areas where communication with terrestrial networks is unavailable; and positioning.

[0005] In addition, in the air interface architecture / protocol, there is already ongoing standardization on technologies such as the Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner, mobility enhancements including conditional switching and DAPS (Dual Active Protocol Stack) switching, and two-step random access (two-step RACH for NR) for simplifying the random access procedure. There is also ongoing standardization on a 5G baseline architecture (e.g., a service-based architecture or service-based interface) for combining network function virtualization (NFV) and software defined network (SDN) technologies, and a system architecture / service for mobile edge computing (MEC) for receiving services based on UE location.

[0006] With the commercialization of 5G mobile communication systems, the already exponentially growing number of connected devices will be connected to the communication network, and it is accordingly expected that enhanced functions and performance of the 5G mobile communication system and integrated operations of the connected devices will be necessary. To this end, new research related to extended reality (XR) is arranged to effectively support AR (augmented reality), VR (virtual reality), MR (mixed reality), etc., to improve 5G performance and reduce complexity by utilizing artificial intelligence (AI) and machine learning (ML), AI service support, meta-service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a foundation for developing not only new waveforms for providing coverage in the terahertz band for 6G mobile communication technology, multi-antenna transmission technologies such as full-dimensional MIMO (FD-MIMO), array antennas, and massive antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional spatial multiplexing technology using OAM (orbital angular momentum), and RIS (reconfigurable smart surface), but also full-duplex technology for improving the frequency efficiency of 6G mobile communication technology and improving system networks, AI-based communication technology for achieving 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 technology for achieving services at a complexity level that exceeds the limits of UE operating capabilities by utilizing ultra-high performance communication and computing resources.

[0008] Fifth generation (5G) or New Radio (NR) mobile communications are gathering increasing momentum recently with all the global technical activities from industry and academia regarding various candidate technologies. Candidate enabling factors for 5G / NR mobile communications include massive antenna technology from traditional cellular bands up to high frequencies to provide beamforming gain and support increased capacity, new waveforms (e.g., new radio access technologies (RATs)) to flexibly accommodate various services / applications with different requirements, new multiple access schemes to support massive connectivity, etc. Summary of the invention

[0009] Technical issues

[0010] The present disclosure relates to wireless communication systems, and more particularly, to timing advance management for multiple TRPs and beam management in wireless communication systems.

[0011] Technical Solution

[0012] In one embodiment, a user equipment (UE) in a wireless communication system is provided. The UE includes a transceiver configured to receive a second timing advance group (TAG) identifier (ID) and a physical downlink control channel (PDCCH) command associated with a second base station (BS) from a first base station (BS). The UE also includes a processor operably coupled to the transceiver, the processor being configured to initiate a contention-free random access (CFRA) process in response to receiving a PDCCH command. The transceiver of the UE is also configured to: send a random access (RA) preamble to the second BS; and receive a timing advance (TA) command (TAC) included in a random access response (RAR) or a media access control element (MAC CE) for the second BS. The processor of the UE is also configured to apply the TAC and start a second time alignment timer corresponding to a second TAG ID associated with the second BS.

[0013] In another embodiment, a method of a UE in a wireless communication system is provided. The method includes: receiving a second TAG ID and a PDCCH command associated with a second BS from a first BS; in response to receiving the PDCCH command, initiating a CFRA process; sending an RA preamble to the second BS; receiving a TAC included in a RAR or a MAC CE for the second BS; and applying the TAC and starting a second time alignment timer corresponding to the second TAG ID associated with the second BS.

[0014] In yet another embodiment, a first BS in a wireless communication system is provided. The first BS includes a processor configured to generate a second TAG ID and a PDCCH command associated with a second BS. The BS also includes a transceiver operably coupled to the processor, the transceiver configured to send a second TAG ID and a PDCCH command associated with the second BS to a UE, wherein: in response to receiving the PDCCH command, an RA preamble is sent to the second BS based on a CFRA process; for the second BS, a TAC included in a RAR or a MAC CE is applied; and a second time alignment timer corresponding to the second TAG ID associated with the second BS is started.

[0015] In yet another embodiment, a method for a first BS in a wireless communication system is provided. The method includes: generating a second TAG ID and a PDCCH command associated with a second BS; and sending the second TAG ID and the PDCCH command associated with the second BS to a UE. Wherein: in response to receiving the PDCCH command, an RA preamble is sent to the second BS based on a CFRA process; for the second BS, a (TAC) included in a RAR or a MAC CE is applied; and a second time alignment timer corresponding to the second TAGID associated with the second BS is started.

[0016] Other technical features may be apparent to those skilled in the art from the following drawings, descriptions and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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, wherein like reference numerals represent like parts:

[0018] Figure 1 An example of a wireless network according to an embodiment of the present disclosure is shown;

[0019] Figure 2 An example of a gNB according to an embodiment of the present disclosure is shown;

[0020] Figure 3 An example of a UE according to an embodiment of the present disclosure is shown;

[0021] Figure 4 and Figure 5 illustrates examples of wireless transmit and receive paths according to the present disclosure;

[0022] Figure 6 A flowchart showing a method for UE-based TA management according to an embodiment of the present disclosure is shown;

[0023] Figure 7A flowchart showing a method for a CFRA process according to an embodiment of the present disclosure;

[0024] Figure 8 A flowchart illustrating a method of a CFRA procedure triggered by a PDCCH command according to an embodiment of the present disclosure; and

[0025] Fig. 9 An example of an enhanced TAC MAC CE with a TCI state ID according to an embodiment of the present disclosure is shown;

[0026] Fig.10 An example of an enhanced TAC MAC CE with two TAs according to an embodiment of the present disclosure is shown;

[0027] Fig.11 An example of an enhanced TAC MAC CE with TAG and TCI state ID according to an embodiment of the present disclosure is shown;

[0028] Fig.12 A flowchart showing a method for UE behavior in network-based TA management according to an embodiment of the present disclosure;

[0029] Fig.13 A flowchart showing a method for network behavior in network-based TA management according to an embodiment of the present disclosure;

[0030] Fig.14 A flowchart illustrating a method for UE behavior in a BFR-triggered L1 / L2-based inter-cell mobility procedure without random access according to an embodiment of the present disclosure;

[0031] Fig.15 A flowchart illustrating a method of UE behavior in a BFR-triggered L1 / L2-based inter-cell mobility procedure with random access according to an embodiment of the present disclosure;

[0032] Fig.16 An example of a BFR-HO MAC CE according to an embodiment of the present disclosure is shown;

[0033] Fig.17 Another example of a BFR-HO MAC CE according to an embodiment of the present disclosure is shown;

[0034] Fig.18 A flowchart illustrating a method for UE behavior in L1 / L2 based mobility procedure with MAC reset / reconfiguration / (re)establishment according to an embodiment of the present disclosure;

[0035] Fig.19A flowchart illustrating a method for UE behavior in a L1 / L2 based mobility procedure without MAC reset / reconfiguration / (re)establishment according to an embodiment of the present disclosure;

[0036] Fig. 20 A flowchart illustrating a method for UE behavior for DL ​​HARQ recovery under L1 / L2 based mobility according to an embodiment of the present disclosure;

[0037] Fig.21 A flowchart illustrating a method for BS behavior for DL ​​HARQ recovery under L1 / L2 based mobility according to an embodiment of the present disclosure;

[0038] Fig. 22 A flowchart showing a method for UE behavior for UL HARQ recovery under L1 / L2 based mobility according to an embodiment of the present disclosure;

[0039] Fig.23 A flowchart illustrating a method for BS behavior for UL HARQ recovery under L1 / L2 based mobility according to an embodiment of the present disclosure; and

[0040] Fig.24 A flowchart of a method for timing advance management for multi-TRP and beam management according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0041] Before the following detailed description, it may be advantageous to set forth the definitions of certain words and phrases used throughout this patent document. The term "coupling" and its derivatives refer to any direct or indirect communication between two or more elements, whether or not these elements are in physical contact with each other. The terms "send", "receive" and "communication" and their derivatives cover both direct and indirect communication. The terms "include" and "comprise" and their derivatives mean including but not limited to. The term "or" is inclusive, meaning and / or. The phrase "associated with ... " and its derivatives mean including, included in ..., interconnected with ..., including, included in ..., connected to or with ..., connected to or with ..., coupled to or with ..., can communicate with ..., collaborate with ..., interlace, juxtapose, be close to, be bound to or with ..., have, have the nature of ..., have to or with ..., etc. 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 function associated with any particular controller can be centralized or distributed, whether local or remote. When used with a list of items, the phrase "at least one of" means that different combinations of one or more of the listed items can be used, and only one of the items in the list may be required. For example, "at least one of A, B, and C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.

[0042] In addition, the various functions described below can be implemented or supported by one or more computer programs, each of which is formed by a computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" indicate one or more computer programs, software components, instruction sets, processes, functions, objects, classes, instances, related data or a portion thereof suitable for implementation in a suitable computer-readable program code. 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 that can be accessed by a computer, such as a read-only memory (ROM), a random access memory (RAM), a hard drive, a compact disk (CD), a digital video disc (DVD) or any other type of memory. "Non-transitory" computer-readable media excludes wired, wireless, optical or other communication links that transmit temporary electrical signals or other signals. Non-transitory computer-readable media include media that can permanently store data and media that can store data and rewrite it later, such as rewritable optical disks or erasable memory devices.

[0043] Definitions for certain other words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

[0044] Discussed below Figures 1 to 24 The various embodiments used to describe the principles of the present disclosure in this patent document are for illustration only and should not be interpreted in any way as limiting the scope of the present disclosure. Those skilled in the art will appreciate that the principles of the present disclosure can be implemented in any appropriately arranged system or device.

[0045] In order to meet the demand for wireless data services that have increased since the deployment of 4G communication systems and to realize various vertical applications, 5G / NR communication systems have been developed and are currently being deployed. 5G / NR communication systems are considered to be implemented in higher frequency (millimeter wave) bands (e.g., 28 GHz or 60 GHz bands) to achieve higher data rates, or in lower frequency bands (such as 6 GHz) to achieve robust coverage and mobility support. In order to reduce the propagation loss of radio waves and increase the transmission distance, beamforming, massive multiple-input multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antenna technology are discussed in 5G / NR communication systems.

[0046] In addition, in the 5G / NR communication system, system network improvements are being developed based on advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, mobile networks, collaborative communications, coordinated multi-point (CoMP), and receiving-end interference cancellation.

[0047] The discussion of 5G systems and frequency bands associated therewith is for reference because certain embodiments of the present disclosure may 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 may be utilized in conjunction with any frequency band. For example, aspects of the present disclosure may also be applied to 5G communication systems, 6G, or even later deployments that may use terahertz (THz) frequency bands.

[0048] The following documents are incorporated by reference into the present disclosure as if fully set forth herein: “3GPP TS 38.300 v17.1.0, NR; NR and NG-RAN Overall description”; “3GPP TS 38.331 v17.1.0, NR; Radio Resource Control (RRC) protocol specification”; “3GPP TS 38.321 v17.1.0, NR; Medium Access Control (MAC) protocol specification”; “3GPP, TS 38.133 v17.6.0, 5G; NR; Requirements for support of radio resource management”; “3GPP, TS 38.306 v17.1.0, 5G; NR; User Equipment (UE) radio access capabilities”; and “3GPP, TS 38.213 v17.2.0, NR; Physical layer procedures for control”.

[0049] The following Figure 1-Figure 3 Various embodiments are described that may be implemented using Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA) communication techniques in a wireless communication system. Figure 1-Figure 3 The description is not meant to imply physical or architectural limitations to the manner in which different embodiments may be implemented. Different embodiments of the present disclosure may be implemented in any suitably arranged communications system.

[0050] Figure 1 An example wireless network according to an embodiment of the present disclosure is shown. Figure 1 The embodiment of the wireless network shown in FIG. 1 is for illustration only. Other embodiments of the wireless network 100 can be used without departing from the scope of the present disclosure.

[0051] like Figure 1 As shown, the wireless network includes gNB 101 (e.g., base station, BS), gNB 102, and gNB 103. gNB 101 communicates with gNB 102 and gNB 103. gNB 101 also communicates with at least one network 130 (such as the Internet, a proprietary Internet Protocol (IP) network, or other data network).

[0052] gNB 102 provides wireless broadband access to network 130 for a first plurality of user equipment (UE) within coverage area 120 of gNB 102. The first plurality of UEs includes UE 111, which may be located in a small business; UE 112, which may be located in an enterprise; UE 113, which may be a WiFi hotspot; UE 114, which may be located in a first residence; UE 115, which may be located in a second residence; and UE 116, which may be a mobile device such as a cellular phone, a wireless laptop, a wireless PDA, etc. gNB 103 provides wireless broadband access to network 130 for a second plurality of UEs within coverage area 125 of gNB 103. The second plurality of UEs includes UE 115 and UE 116. In some embodiments, one or more of gNBs 101-103 may 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 technologies.

[0053] Depending on the network type, the term "base station" or "BS" can indicate any component (or set of components) configured to provide wireless access to a network, such as a transmission point (TP), a transmission-reception point (TRP), an enhanced base station (eNodeB or eNB), a 5G / NR base station (gNB), a macro cell, a femto cell, a WiFi access point (AP), or other wirelessly enabled devices. The base station can provide wireless access according to one or more wireless communication protocols (e.g., 5G / NR Third Generation Partnership Project (3GPP) NR, Long Term Evolution (LTE), Advanced LTE (LTE-A), High Speed ​​Packet Access (HSPA), Wi-Fi 802.11a / b / g / n / ac, etc.). For convenience, the terms "BS" and "TRP" are used interchangeably in this patent document to indicate a network infrastructure component that provides wireless access to a remote terminal. In addition, depending on the network type, the term "user equipment" or "UE" can indicate any component, such as a "mobile station", "subscriber station", "remote terminal", "wireless terminal", "reception point" or "user equipment". For convenience, the terms "user equipment" and "UE" are used in this patent document to refer to a remote wireless device that wirelessly accesses a BS, whether the UE is a mobile device (such as a mobile phone or smartphone) or is generally considered a fixed device (such as a desktop computer or vending machine).

[0054] The dashed lines illustrate the approximate extents of coverage areas 120 and 125, which are shown as approximately circular for purposes of illustration and explanation only. It should be clearly understood that coverage areas associated with a gNB, such as coverage areas 120 and 125, may have other shapes, including irregular shapes, depending on the configuration of the gNB and variations in the radio environment associated with natural and man-made obstacles.

[0055] As described in more detail below, one or more of the UEs 111-116 include circuitry, programming, or a combination thereof for supporting timing advance management for multiple TRPs and beam management in a wireless communication system. In certain embodiments, one or more of the gNBs 101-103 include circuitry, programming, or a combination thereof for supporting timing advance management for multiple TRPs and beam management in a wireless communication system.

[0056] although Figure 1 An example of a wireless network is shown, but Figure 1 Various changes may be made. For example, the wireless network can include any number of gNBs and any number of UEs in any suitable arrangement. In addition, gNB 101 can communicate directly with any number of UEs and provide those UEs with wireless broadband access to network 130. Similarly, each gNB 102-103 can communicate directly with network 130 and provide the UEs with direct wireless broadband access to network 130. In addition, gNBs 101, 102, and / or 103 can provide access to other or additional external networks, such as an external telephone network or other type of data network.

[0057] Figure 2 An example gNB 102 is shown according to an embodiment of the present disclosure. Figure 2 The embodiment of the gNB 102 shown in FIG. is for illustration only, and Figure 1 gNBs 101 and 103 can have the same or similar configurations. However, gNBs have a variety of configurations, and Figure 2 The scope of the present disclosure is not limited to any particular implementation of the gNB.

[0058] like Figure 2 As shown, the gNB 102 includes multiple antennas 205a-205n, multiple transceivers 210a-210n, a controller / processor 225, a memory 230, and a backhaul or network interface 235.

[0059] The transceivers 210a-210n receive incoming RF signals from the antennas 205a-205n, such as signals transmitted by UEs in the network 100. The transceivers 210a-210n downconvert the incoming RF signals to generate IF or baseband signals. The IF or baseband signals are processed by receive (RX) processing circuits in the transceivers 210a-210n and / or the controller / processor 225, which generate processed baseband signals by filtering, decoding, and / or digitizing the baseband or IF signals. The controller / processor 225 may further process the baseband signals.

[0060] Transmit (TX) processing circuitry in the transceivers 210a-210n and / or the controller / processor 225 receives analog or digital data (such as voice data, web data, email, or interactive video game data) from the controller / processor 225. The TX processing circuitry encodes, multiplexes, and / or digitizes the outgoing baseband data to generate processed baseband or IF signals. The transceivers 210a-210n up-convert the baseband or IF signals to RF signals that are transmitted via the antennas 205a-205n.

[0061] The controller / processor 225 can include one or more processors or other processing devices that control the overall operation of the gNB 102. For example, the controller / processor 225 can control the reception of UL channel signals and the transmission of DL channel signals by the transceivers 210a-210n in accordance with well-known principles. The controller / processor 225 can also support additional functionality, such as more advanced wireless communication functionality. For example, the controller / processor 225 can support beamforming or directional routing operations, in which outgoing / incoming signals from / to multiple antennas 205a-205n are weighted differently to effectively steer the outgoing signals in a desired direction. Any of a variety of other functions can be supported by the controller / processor 225 in the gNB 102.

[0062] The controller / processor 225 is also capable of executing programs and other processes, such as an OS, residing in the memory 230. The controller / processor 225 is also capable of moving data into or out of the memory 230 as required by the executed process. The controller / processor 225 is also capable of executing programs and other processes residing in the memory 230, such as processes for timing advance management of multiple TRPs and beam management in wireless communication systems.

[0063] The controller / processor 225 is also coupled to a backhaul or network interface 235. The backhaul or network interface 235 allows the gNB 102 to communicate with other devices or systems via a backhaul connection or via a network. The interface 235 is capable of supporting communication via any suitable wired or wireless connection (or multiple). For example, when the gNB 102 is implemented as part of a cellular communication system (such as a cellular communication system supporting 5G / NR, LTE, or LTE-A), the interface 235 is capable of allowing the gNB 102 to communicate with other gNBs via a wired or wireless backhaul connection. When the gNB 102 is implemented as an access point, the interface 235 may allow the gNB 102 to communicate via a wired or wireless local area network or via a wired or wireless connection to a larger network (such as the Internet). The interface 235 includes any suitable structure that supports communication via a wired or wireless connection, such as Ethernet or a transceiver.

[0064] Memory 230 is coupled to controller / processor 225. A portion of memory 230 can include RAM, and another portion of memory 230 can include flash or other ROM.

[0065] although Figure 2 An example of gNB 102 is shown, but the Figure 2 For example, gNB 102 can include any number of Figure 2 In addition, Figure 2 The various components in can be combined, further subdivided or omitted, and additional components can be added according to specific needs.

[0066] Figure 3 An example UE 116 is shown in accordance with an embodiment of the present disclosure. Figure 3 The embodiment of UE 116 shown in FIG. 1 is for illustration only, and Figure 1 UEs 111-115 can have the same or similar configurations. However, UEs have a variety of configurations, and Figure 3 The scope of the present disclosure is not limited to any particular implementation of the UE.

[0067] like Figure 3 As shown, UE 116 includes antenna (or multiple) 305, transceiver (or multiple) 310 and microphone 320. UE 116 also includes speaker 330, processor 340, input / output (I / O) interface (IF) 345, input 350, display 355 and memory 360. Memory 360 includes operating system (OS) 361 and one or more applications 362.

[0068] Transceiver(s) 310 receives incoming RF signals from antenna 305 transmitted by a gNB of network 100. Transceiver(s) 310 downconverts the incoming RF signals to generate an intermediate frequency (IF) or baseband signal. The IF or baseband signal is processed by RX processing circuitry in transceiver(s) 310 and / or 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 speaker 330 (such as for voice data) or is processed by processor 340 (such as for web browsing data).

[0069] The TX processing circuitry in the transceiver(s) 310 and / or processor 340 receives analog or digital voice data from microphone 320 or other outgoing baseband data (such as web data, email, or interactive video game data) from 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(s) 310 up-converts the baseband or IF signal to an RF signal that is transmitted via antenna(s) 305.

[0070] The processor 340 can include one or more processors or other processing devices and execute the OS 361 stored in the memory 360 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 (or multiple) 310 according to well-known principles. In some embodiments, the processor 340 includes at least one microprocessor or microcontroller.

[0071] The processor 340 is also capable of executing other processes and programs resident in the memory 360, such as processes for timing advance management of multiple TRPs and beam management in a wireless communication system. The processor 340 is capable of moving data into or out of the memory 360 as needed for the executed process. In some embodiments, the processor 340 is configured to execute the application 362 based on the OS 361 or in response to a signal received from the gNB or 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 laptops and handheld computers. The I / O interface 345 is the communication path between these accessories and the processor 340.

[0072] Processor 340 is also coupled to input 350 (which includes, for example, a touch screen, keyboard, etc.) and display 355. An operator of UE 116 can use input 350 to enter data into UE 116. 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 a website).

[0073] Memory 360 is coupled to processor 340. A portion of memory 360 can include random access memory (RAM), and another portion of memory 360 can include flash memory or other read-only memory (ROM).

[0074] although Figure 3 An example of UE 116 is shown, but the Figure 3 Make various changes. For example, Figure 3 The various components in can be combined, further subdivided, or omitted, and additional components can be added according to specific needs. As a specific example, 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, transceiver(s) 310 can include any number of transceivers and signal processing chains and can be connected to any number of antennas. In addition, although Figure 3 The UE 116 is shown configured as a mobile phone or smart phone, but the UE can be configured to operate as other types of mobile or stationary devices.

[0075] Figure 4 and Figure 5 Example wireless transmit and receive paths according to the present disclosure are shown. In the following description, transmit path 400 may be described as being implemented in a gNB (such as gNB 102) and receive path 500 may be described as being implemented in a UE (such as UE 116). However, it is understood that receive path 500 can be implemented in a gNB and transmit path 400 can be implemented in a UE. In some embodiments, receive path 500 is configured to support timing advance management for multiple TRPs and beam management in a wireless communication system.

[0076] like Figure 4 The transmit path 400 shown includes a channel coding and modulation block 405, a serial to parallel (S to P) block 410, an inverse fast Fourier transform (IFFT) block of size N 415, a parallel to serial (P to S) block 420, an add cyclic prefix block 425, and an upconverter (UC) 430. Figure 5 The receive path 500 shown includes a downconverter (DC) 555, a remove cyclic prefix block 560, a serial to parallel (S to P) block 565, a size N fast Fourier transform (FFT) block 570, a parallel to serial (P to S) block 575, and a channel decoding and demodulation block 580.

[0077] like Figure 4As shown, the channel coding and modulation block 405 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 sequence of frequency-domain modulation symbols.

[0078] The serial to parallel block 410 converts (such as demultiplexes) the serial modulation symbols into parallel data to generate N parallel symbol streams, where N is the IFFT / FFT size used in the gNB 102 and the UE 116. The size N IFFT block 415 performs an IFFT operation on the N parallel symbol streams to generate a time domain output signal. The parallel to serial block 420 converts (such as multiplexes) the parallel time domain output symbols from the size N IFFT block 415 to generate a serial time domain signal. The add cyclic prefix block 425 inserts a cyclic prefix into the time domain signal. The up converter 430 modulates (such as upconverts) the output of the add cyclic prefix block 425 to an RF frequency for transmission via a wireless channel. The signal may also be filtered at baseband before conversion to RF frequency.

[0079] The RF signal transmitted from gNB 102 reaches UE 116 after passing through the wireless channel, and operations opposite to those at gNB 102 are performed at UE 116.

[0080] like Figure 5 As shown, the down converter 555 down-converts the received signal to the baseband frequency, and the cyclic prefix removal block 560 removes the cyclic prefix to generate a serial time domain baseband signal. The serial to parallel block 565 converts the time domain baseband signal into a parallel time domain signal. The size N FFT block 570 performs an FFT algorithm to generate N parallel frequency domain signals. The parallel to serial block 575 converts the parallel frequency domain signals into a sequence of modulated data symbols. The channel decoding and demodulation block 580 demodulates and decodes the modulation symbols to recover the original input data stream.

[0081] Each of gNBs 101-103 may implement Figure 4 The transmission path 400 shown is similar to the transmission to UE 111-116 in the downlink, and can be implemented as follows: Figure 5 Receive path 500 is shown, which is similar to receiving from UE 111-116 in the uplink. Similarly, each of UE 111-116 can implement transmit path 400 for transmitting to gNB 101-103 in the uplink and can implement receive path 500 for receiving from gNB 101-103 in the downlink.

[0082] Figure 4 and Figure 5Each component in can be implemented using hardware only or a combination of hardware and software / firmware. As a specific example, Figure 4 and Figure 5 At least some components in can be implemented in software, while other components can be implemented by configurable hardware or a mixture of software and configurable hardware. For example, FFT block 570 and IFFT block 415 can be implemented as configurable software algorithms, wherein the value of size N can be modified according to the implementation.

[0083] In addition, although described as using FFT and IFFT, this is by way of illustration only and may not be construed as limiting the scope of the present disclosure. Other types of transforms can be used, such as discrete Fourier transform (DFT) and inverse discrete Fourier transform (IDFT) functions. It will be appreciated that for DFT and IDFT functions, the value of variable N may be any integer (e.g., 1, 2, 3, 4, etc.), while for FFT and IFFT functions, the value of variable N may be any integer that is a power of two (e.g., 1, 2, 4, 8, 16, etc.).

[0084] although Figure 4 and Figure 5 An example of a wireless transmit and receive path is shown, but the Figure 4 and Figure 5 Make various changes. For example, Figure 4 and Figure 5 The various components in may be combined, further subdivided, or omitted, and additional components can be added according to specific needs. Figure 4 and Figure 5 It 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 communications in a wireless network.

[0085] 3GPP has developed technical specifications and standards to define the new 5G radio access technology known as 5G NR. MIMO is one of the key technologies in NR systems and has shown its success in commercial deployments. In multi-TRP operation, the serving cell is able to schedule UEs from two TRPs to provide better coverage, reliability, and data rate for downlink and uplink transmission / reception. Two operation modes are supported to schedule multi-TRP transmissions: single DCI for UEs scheduled by the same DCI for both TRPs and multi-DCI for UEs scheduled by independent DCIs from each TRP.

[0086] In Rel-17, inter-cell multi-TRP operation was introduced, where one TRP comes from the serving cell and the other TRP can come from a cell with a PCI other than the serving cell, i.e., a non-serving cell, without changing the serving cell. For downlink multi-DCI transmission, one or more transmission configuration indicator (TCI) states can be associated with a synchronization signal / physical broadcast channel (PBCH) block (SSB) from a non-serving cell. An activated TCI state can be associated with at most one non-serving cell at a time. For uplink transmission, the UE sends the same content to two TRPs with corresponding beam directions associated with different spatial relationships.

[0087] In Rel-17, a single timing advance (TA) is maintained for multi-TRP operation and inter-cell beam management, assuming that transmissions from / to both TRPs are synchronized within the cyclic prefix (CP). Although the serving cell is not changed by inter-cell multi-TRP operation, the TRP from the non-serving cell can be inter-distributed unit (DU) or intra-centralized unit (CU), which may have different propagation delays for UL transmissions and may not be synchronized with the serving cell TRP. In such a scenario, the UE is expected to maintain two TAs for the serving cell.

[0088] In the present disclosure, TA management in which one or more TAs are maintained for a serving cell for L1 / L2 triggered mobility is provided, for example, in multi-TRP operation, inter-cell beam management operation, and early UL synchronization. RRC configuration and MAC procedures are specified. In the present disclosure, operations for the second TRP of a serving cell can also be applied to a TRP or TCI state (or multiple) of a non-serving cell, and vice versa. Operations on TCI states associated with non-serving cells can be applied to non-serving cells. A non-serving cell can refer to an additional cell having a PCI in addition to the serving cell PCI.

[0089] Figure 6 1 is a flow chart showing a method 600 for UE-based TA management according to an embodiment of the present disclosure. The method 600 may be performed by a UE (e.g., Figure 1 111-116) as shown. Figure 6 The embodiment of method 600 shown in FIG. 6 is for illustration only. Figure 6 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0090] like Figure 6As shown, at operation 605, the UE maintains the TA for the serving cell TRP and / or TCI state by a conventional UL timing alignment operation, i.e., adjusting the TA according to a timing advance command (TAC) MAC CE and maintaining the timeAlignmentTimer for the TAG targeted by the TAC MAC CE. At operation 610, when an UL transmission using a TCI state associated with a second TRP and / or a non-serving cell is configured / scheduled, the UE establishes an initial TA for the TRP and / or TCI state. At operation 615, the UE maintains the TA for the TRP and / or TCI state by adjusting the TA according to the TAC MAC CE and / or maintaining UL timing alignment through the timeAlignmentTimer.

[0091] Figure 7 700 is a flowchart of a method for a CFRA process according to an embodiment of the present disclosure. The method 700 may be performed by a UE (eg, Figure 1 111-116) as shown. Figure 7 The embodiment of method 700 shown in FIG. 7 is for illustration only. Figure 7 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0092] In one embodiment of UE-based TA management, the UE maintains more than one TA for the serving cell and / or non-serving cell. For multi-TRP operation, each TA is maintained for one TRP. For inter-cell beam management, in addition to the serving cell TA, a second TA is maintained for UL transmission using the TCI state associated with the non-serving cell. Figure 7 As shown, at operation 705, the UE maintains a first TA for the TRP and / or TCI state of the serving cell by a conventional UL timing alignment operation, i.e., adjusting the TA according to a timing advance command (TAC) MAC CE and maintaining a timeAlignmentTimer for the TAG targeted by the TAC MAC CE. At operation 710, the UE establishes a second TA for the TRP and / or TCI state of the serving cell and / or non-serving cell. At operation 715, the UE maintains the TA for the TRP and / or TCI state by adjusting the TA according to the TAC MAC CE and / or maintaining UL timing alignment through one or more timeAlignmentTimers.

[0093] As an embodiment of operation 710, the UE performs random access (e.g., contention-based random access (CBRA) or CFRA) to establish a TA for DL / UL data transmission when the UE is out of synchronization for both TRPs, wherein the two TRPs can belong to the same serving cell, or one TRP belongs to the serving cell and the other TRP belongs to a non-serving cell. "Out-of-synchronization" can refer to a situation where each TRP is associated with a time alignment timer and both time alignment timers for the two TRPs expire. For example, if CFRA is not configured, the UE initiates CBRA for one TRP belonging to the serving cell. In another example, the UE initiates CFRA for one TRP belonging to the serving cell and configured with CFRA resources (e.g., preamble index).

[0094] As another embodiment of operation 710, when the UE is out of synchronization for a TRP, the UE performs random access (e.g., CBRA or CFRA) to establish a TA for DL / UL data transmission, wherein the TRP can belong to a serving cell or a non-serving cell. "Out of synchronization" can refer to a situation where the time alignment timer for the TRP expires. As an example, if CFRA is not configured, the UE initiates CBRA for the TRP. In another example, if CFRA resources (e.g., preamble index) are configured, the UE initiates CFRA for the TRP.

[0095] In one embodiment of process 710, the UE performs a random access (RA) to establish an initial TA for the second TRP and / or for a TCI state associated with a non-serving cell. Figure 7 As shown, the UE is able to perform a 4-step CFRA with a process similar to beam failure recovery for SpCell. CFRA resources (e.g., preamble index) are allocated through RRC configuration for random access to establish an initial TA (705) for a second TRP or for a TCI state associated with a non-serving cell. When scheduled to transmit using a TCI state associated with a second TRP or a non-serving cell, or when instructed to perform random access for UL synchronization with a second TRP or a non-serving cell, the UE triggers the CFRA process (710).

[0096] The UE sets the preamble index to a preconfigured ra-PreambleIndex corresponding to the SSB or CSI-RS associated with the TCI state to be used for the scheduled transmission (715), determines the PRACH opportunity associated with the SSB if the TCI state is associated with the CSI-RS or applies the ra-OcsionList configured by the RRC (720), and instructs the physical layer to send the RA preamble using the selected PRACH opportunity, preamble index and PREAMBLE_RECEIVED_TARGET_POWER (725).

[0097] Figure 8 800 is a flowchart of a method 800 for a CFRA process triggered by a PDCCH command according to an embodiment of the present disclosure. The method 8000 may be performed by a UE (e.g., Figure 1 111-116) as shown. Figure 8 The embodiment of method 800 shown in FIG. 8 is for illustration only. Figure 8 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0098] In such Figure 8 In another example shown, similar to the process of establishing a TA for a SCell for a secondary TAG, the CFRA process is initiated by the gNB with a PDCCH command, wherein the PDCCH command is sent via a TRP and / or TCI state associated with the serving cell (805). Alternatively, the PDCCH command for CFRA can be sent via a second TRP and / or TCI state associated with a non-serving cell (805). For example, the PDDCH command is sent on a control resource set configured with a CORESET pool index indicating the associated TRP.

[0099] Upon receiving the PDCCH command, the UE sets the preamble index to the ra-PreambleIndex signaled by the PDCCH command (810), determines the PRACH opportunity associated with the SSB index indicated by the SSB index field of the PDCCH command (815), calculates the RA-RNTI associated with the PRACH opportunity in which the random access preamble is sent (820), and instructs the physical layer to send the RA preamble using the selected PRACH opportunity, corresponding RA-RNTI, preamble index and PREAMBLE_RECEIVED_TARGET_POWER (825). The RA preamble transmission occurs on the second TRP or non-serving cell as follows: the SSB index signaled in the PDCCH command is associated with the TCI state for the second TRP or non-serving cell.

[0100] After sending the RA preamble, the UE starts the ra-ResponseWindow configured in RACH-ConfigCommon, and monitors the PDCCH in the common search space for a random access response (RAR) identified by a C-RNTI or RA-RNTI while the ra-ResponseWindow is running (730, 830). When the UE receives the RAR, the UE applies the TAC received in the RAR to the TRP and / or TCI state (735, 835). If the TAG is pre-configured for the TRP and / or TCI state, the UE starts / restarts the timeAlignmentTimer associated with the TAG (740, 840). The UE can use the UL grant in the RAR for transmission to a second TRP and / or using a TCI state associated with a non-serving cell. The UE can ignore the TEMPORAL_C-RNTI received in the RAR.

[0101] For another embodiment of operation 610, the TA determined by the network is indicated via L1 or L2 signaling and / or configured by an RRC message from the serving gNB. In one example, the initial TA for UL transmissions using a TCI state associated with a second TRP and / or a non-serving cell can be indicated in a DCI indicating the TCI state for scheduled UL transmissions. A new field can be introduced in the DCI for TA indication, or a reserved field can be used. The initial TA value can be indicated by a TA offset to the serving cell TA.

[0102] For an example, a new MAC CE can be introduced to indicate the TA scheduled for UL transmission using a TCI state associated with a second TRP and / or a non-serving cell. Using a MAC subheader with LCID or eLCID, the new MAC CE can include the TCI state and / or CORESET pool identifier (ID) and / or the corresponding TA and / or the associated TAG ID, such as Fig. 9 The TA value can be indicated by a TA offset to the serving cell TA or as an absolute TA.

[0103] Fig. 9 An example of an enhanced TAC MAC CE 900 with a TCI state ID according to an embodiment of the present disclosure is shown. Fig. 9 The embodiment 900 of the enhanced TAC MAC CE with TCI state ID shown in FIGURE 9 is for illustration only.

[0104] For an example, in a TCI state configuration for multi-TRP and / or inter-cell beam management or in a CORESET pool configuration for multi-TRP operation, each TCI state or each CORESET pool can be configured with a TAG ID. Alternatively, in a TAG configuration, one TAG ID can be associated with a set of TCI states or with a CORESET pool ID, as shown in Table 1.

[0105]

Table 1

[0106]

[0107]

[0108] When the UE is scheduled to use a TCI state associated with a second TRP and / or a non-serving cell, the TA can be indicated by a TAC MAC CE with a TAG ID associated with the TCI state. A new TAC MAC CE can be distinguished from an existing TAC MAC CE by using a MAC subheader with a different LCID or eLCID.

[0109] For one example, the TA for transmission using a TCI state associated with a second TRP and / or a non-serving cell can be indicated in an enhanced TAC MAC CE by a TA offset relative to the serving cell TA, the enhanced TAC MAC CE containing the TA and TA offset associated with the TAG ID of the serving cell to determine the TA or TCI state of the second TRP associated with the non-serving cell.

[0110] Fig.10An example of an enhanced TAC MAC CE 1000 with two TAs according to an embodiment of the present disclosure is shown. Fig.10 The embodiment 1000 of the enhanced TAC MAC CE with two TAs shown in FIG. 1 is for illustration only.

[0111] Fig.10 The following example is shown in FIG. 1 , where fields T1 and T2 indicate whether serving cell TA and TA offset are indicated, respectively, and the field Timing Advance Offset can include one bit for a positive / negative sign of the offset value.

[0112] For one example, the TA for transmissions using TCI states associated with a second TRP and / or a non-serving cell can be configured by RRC. A common initial TA value can be configured for all TCI states associated with a second TRP or a non-serving cell. Alternatively, a group common initial TA value can be configured for a group of TCI states.

[0113] For operation 615, the UE maintains a TA for the second TRP and / or TCI state associated with the non-serving cell. In the first embodiment, if a separate TAG ID is configured for the second TRP and / or TCI state associated with the non-serving cell, the UE maintains a separate TimeAlignmentTimer. The TAG can be pre-configured by the RRC as shown above, that is, each TCI state or each CORESET pool is mapped to a TAG ID. An additional TAG ID for the second TRP of the serving cell can be configured in the serving cell configuration (e.g., servingCellConfig). The TAG ID associated with each non-serving cell can be configured in the serving cell configuration (e.g., servingCellConfig).

[0114] Upon receiving a TA command or RAR for a TAG and adjusting the TA according to the TA command or RAR; or upon obtaining UL synchronization for a second TRP and / or TCI state associated with a non-serving cell (e.g., through a random access procedure), the UE starts / restarts the TimeAlignmentTimer associated with the TAG. The TAC can be included in Fig. 9 In the MAC CE shown in or Fig.10 or in a TAC MAC CE distinguished from an existing TAC MAC CE by using a MAC subheader with a different LCID or eLCID.

[0115] If the timeAlignmentTimer expires for the TAG associated with the second TRP or if the timeAlignmentTimer expires for the TAG configured for the TCI state associated with the non-serving cell, the UE may stop UL transmission and / or notify the RRC to release PUCCH and / or SRS and / or any configured downlink allocations and / or configured uplink grants and / or any PUSCH resources for semi-persistent CSI reporting that are associated with the second TRP and / or associated with the TCI state associated with the non-serving cell while the timeAlignmentTimer for the first TRP is running.

[0116] If both the timeAlignmentTimer for the first TRP and the timeAlignmentTimer for the second TRP in the serving cell expire, the UE stops UL transmission and / or notifies the RRC to release PUCCH and / or SRS and / or any configured downlink allocations and / or configured uplink grants and / or any PUSCH resources for semi-persistent CSI reporting, which are associated with the second TRP and / or associated with a TCI state associated with a non-serving cell.

[0117] If the network indicates via RRC or MAC CE that the second TRP is not scheduled or that the TCI state (or states) associated with the non-serving cell is prohibited, or if the maximum uplink transmit timing difference between the TAG used for the serving cell TRP and the TAG used for the second TRP is exceeded, the UE considers that the TimeAlignmentTimer associated with the second TRP or the TimeAlignmentTimer associated with the TCI state of the non-serving cell has expired, the UE stops UL transmission and / or releases PUCCH and / or SRS and / or any configured downlink allocations and / or configured uplink grants and / or any PUSCH resources for semi-persistent CSI reporting, which are associated with the second TRP and / or associated with the TCI state associated with the non-serving cell.

[0118] In one embodiment of operation 615, the UE maintains a single TimeAlignmentTimer with a single TAG ID configured for the serving cell, i.e., the TimeAlignmentTimer associated with the TAG for the serving cell is maintained as a legacy operation for UL timing alignment. In one example, in order to update the serving cell TA together with the TA for the second TRP and / or the TA for the TCI state associated with the non-serving cell, the network can send another request for UL synchronization by triggering random access, e.g., a PDCCH command, or the network can send Fig.10MAC CE shown in .

[0119] In one example, in order to independently update the TA for the second TRP and / or the TA for the TCI state associated with the non-serving cell, the network is able to send a MAC CE including a TAG ID and / or a TA value and / or a CORESET pool ID and / or a TCI state ID. Fig.11 An example is shown in , where the TAC is for the indicated TCI state ID or the CORESET pool ID associated with the indicated TAG. When any one TA for the serving cell is updated or resynchronized, for example by a MAC CE or random access procedure, a single TimeAlignmentTimer is restarted.

[0120] Fig.11 An example of an enhanced TAC MAC CE 1100 with TAG and TCI state ID according to an embodiment of the present disclosure is shown. Fig.11 The embodiment 1100 of the enhanced TAC MAC CE with TAG and TCI state ID shown in FIGURE 1 is for illustration only.

[0121] If the network indicates via RRC or MAC CE that the second TRP is not scheduled or that the TCI state(s) associated with the non-serving cell is prohibited, or if the maximum uplink transmit timing difference between the two TRPs is exceeded, the UE considers that the TimeAlignmentTimer has expired, the UE stops UL transmission and / or releases PUCCH and / or SRS and / or any configured downlink allocations and / or configured uplink grants and / or any PUSCH resources for semi-persistent CSI reporting, which are associated with two TRPs or any TCI states.

[0122] In one embodiment of operation 615, the network configures a single TAG or two TAGs for multi-TRP operation in L1 / L2 triggered mobility or inter-cell beam management or early UL synchronization according to the UE capability. A UE capability indication can be introduced for whether the UE supports two TAGs (i.e., two timeAlignmentTimers) or a single TAG (i.e., a single timeAlignmentTimer) for the corresponding operation. The capability indication can be per UE or per frequency band or per frequency band combination.

[0123] Fig.12 1 is a flow chart showing a method 1200 for UE behavior in network-based TA management according to an embodiment of the present disclosure. The method 1200 may be performed by a UE (e.g., Figure 1 111-116) as shown. Fig.12The embodiment of method 1200 shown in FIG. 1 is for illustration only. Fig.12 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0124] In one embodiment of network-based TA management, the UE can maintain the TRP and / or TA of the beam for the serving cell through traditional UL timing alignment operations, i.e., adjusting the TA according to the TAC MAC CE and maintaining the timeAlignmentTimer, such as Fig.12 1205 in operation 1206. For multi-TRP operation, when the UE is scheduled to transmit to the second TRP, the UE can assume that the TA used for the second TRP is the same as the TA used for the first TRP of the serving cell, and apply the serving cell TA to the second TRP (1210). For inter-cell beam management, when the UE is scheduled to transmit using a TCI state associated with a non-serving cell, the UE can assume that the TA used for UL transmissions using the TCI state associated with the serving cell and the non-serving cell is the same, and apply the serving cell TA to the UL transmissions using the TCI state associated with the non-serving cell.

[0125] Fig.13 1 is a flowchart showing a method 1300 for network behavior in network-based TA management according to an embodiment of the present disclosure. The method 1300 may be performed by a BS (e.g., Figure 1 101-103) as shown. Fig.13 The embodiment of method 1300 shown in FIG. 1 is for illustration only. Fig.13 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0126] like Fig.13 As shown, the network is able to handle TA differences between the two TRPs (if any). At operation 1305, the network (e.g., serving gNB) configures multi-TRP operation and / or inter-cell beam management, schedules UL transmissions, and determines a TA for a second TRP and / or for a TCI state associated with a non-serving cell. In an example, the TA for the second TRP can be estimated based on a previous UL transmission to the TRP. In another example, the TA for an UL transmission using a TCI state associated with a non-serving cell can be estimated based on a previous transmission using the TCI state from the non-serving cell.

[0127] As an example, if necessary, the processing of TA for the second TRP and / or for the TCI state associated with the non-serving cell can be coordinated via DU-CU interface signaling. At operation 1310, when any UL transmission is received, the network processes the TA for the second TRP and / or for the TCI state associated with the non-serving cell, for example by pre-compensating for any timing differences.

[0128] For UEs in connected mode, mobility is controlled by the network with help from the UE to maintain good connection quality. Based on measurements of the radio link quality of the serving cell and neighboring cell (or cells) reported by the UE, when the UE is experiencing a degraded connection to the serving cell, the network can switch the UE to a neighboring cell that can provide better radio conditions. In Release 15 NR, basic mechanisms and procedures for network-controlled mobility in connected mode were developed. In Release 16 NR, enhancements to network-controlled mobility in connected mode were introduced to mitigate connection interruptions during the switching process. Specifically, two enhanced switching mechanisms, called Conditional Handover (CHO) and Dual Active Protocol Stack (DAPS), were developed.

[0129] For mobility in connected mode, handover is initiated by the network based on L3 (Layer 3) measurements via high-layer signaling (e.g., RRC messages). However, this process involves more latency, signaling overhead, and interruption time, which may become a critical issue in some scenarios with frequent handovers, such as high-speed vehicles and UEs in FR2 deployments.

[0130] It is necessary to reduce the overhead and / or latency and interruption time during the handover process. This brings about the need for L1 / L2 (layer 1 / layer 2) inter-cell mobility, by which the handover can be triggered by L1 / L2 signaling based on L1 measurements. More specifically, L1 / L2-based inter-cell mobility refers to a network-controlled mobility mechanism that switches the UE from a source cell to a target cell via inter-cell beam switching triggered by L1 / L2 signaling, wherein the beam switching decision is based on L1 measurements of beams between neighboring cells.

[0131] On the other hand, beam failure detection (BFD) and beam failure recovery (BFR) have been supported since Release 15 and further enhanced in Release 16 and Release 17. For beam failure detection, the gNB configures the UE with a beam failure detection reference signal (BFD-RS), which can be an SSB or CSI-RS, as a BFD-RS set (or multiple) for each serving cell. If one BFD-RS set is configured for a serving cell, the UE declares a beam failure on the serving cell when the number of beam failure instance indications from the physical layer reaches a configured threshold before the configured timer expires. If two BFD-RS sets are configured for a serving cell for beam failure detection in multi-TRP operation, each BFD-RS set is associated with a TRP, and the UE declares a beam failure for the TRP when the number of beam failure instance indications associated with the corresponding BFD-RS set from the physical layer reaches a configured threshold before the configured timer expires.

[0132] For beam failure recovery, if beam failure is detected on the BFD-RS set for the SpCell if one BFD-RS set is configured, or on both BFD-RS sets for the SpCell if two BFD-RS sets are configured, the UE triggers beam failure recovery by initiating a random access procedure on the SpCell and selects a suitable beam to perform beam failure recovery if available. If the gNB has provided dedicated random access resources for certain beams, the UE may prioritize these resources. In case of beam failure on one BFD-RS set of the SpCell, the BFR MAC CE is included in MsgA / Msg3 for contention-based random access.

[0133] In case of beam failure on two BFD-RS sets of SpCell, an enhanced BFR MAC CE is included in MsgA / Msg3. Beam failure recovery for SpCell is considered complete upon completion of the random access procedure. If beam failure is detected on the BFD-RS set for SCell when one BFD-RS set is configured, or if beam failure is detected on the BFD-RS set for the TRP of the serving cell, the UE triggers beam failure recovery by initiating transmission of a BFR MAC CE for the SCell or an enhanced BFR MAC CE for the TRP of the serving cell, respectively.

[0134] If available and indicated in the MAC CE, a suitable beam for recovery is selected for that SCell / TRP. Beam failure recovery for that SCell / TRP is considered complete upon receipt of a PDCCH indicating an uplink grant for a new transmission of the HARQ process for the transmission of the MAC CE.

[0135] In Release 18, new work items have been agreed to further enhance mobility in NR, aiming at L1 / L2-based inter-cell mobility. For L1 / L2-based inter-cell mobility, switching can be initiated / triggered / performed by beam switching indicated from the physical layer. In the traditional BFD / BFR process, when a beam failure is detected, the UE is switched to a new suitable beam to recover the current serving cell. However, in scenarios where the UE moves quickly, beam failure may mean that switching that can be performed by L1 / L2-based inter-cell mobility is required. That is, the UE is able to recover from the beam failure by switching the beam to the target cell, instead of selecting / switching to a beam within the candidate beams from the current serving cell. Therefore, it is expected to develop BFR-triggered L1 / L2-based inter-cell mobility.

[0136] The present disclosure utilizes various embodiments including configuration, procedures, and signaling of L1 / L2 based inter-cell mobility triggered by failure recovery.

[0137] Fig.14 1400 is a flowchart showing a method 1400 for UE behavior in a BFR-triggered L1 / L2-based inter-cell mobility procedure without random access according to an embodiment of the present disclosure. The method 1400 may be performed by a UE (e.g., Figure 1 111-116) as shown. Fig.14 The embodiment of method 1400 shown in FIG. 1 is for illustration only. Fig.14 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0138] In one embodiment, L1 / L2 based inter-cell mobility can be triggered by BFR without random access, such as Fig.14 shown.

[0139] At operation 1405, the UE receives an RRC message, such as RRCReconfiguration, from the serving gNB for BFR-triggered L1 / L2 mobility configuration. The RRC message can provide L1 / L2 mobility configuration for each serving cell or each cell group, which can include a candidate cell pool, and information included in ServingCellConfigCommon and / or ServingCellConfig and / or system information about each candidate cell. Candidate cells can include SpCells, SCells (or multiple), additional cells that provide a second TRP in inter-cell multi-TRP operation, and any other inter-DU intra-CU cells.

[0140] RRC messages, such as RRCReconfiguration, can provide BFD / BFR configuration per serving cell or per zone group, can include BFD-RS set, BFR-RS set, BFD / BFR related parameters, and information included in RadioLinkMonitoringConfig and / or BeamFailureRecoveryConfig and / or BeamFailureRecoveryRSConfig. The gNB can configure the UE with one set of BFD-RS (i.e., SSB and / or periodic CSI-RS and / or aperiodic CSI-RS and / or semi-persistent CSI-RS) or two sets of BFD-RS for multi-TRP operation, each associated with a TRP, and one TRP can be from an additional cell other than the serving cell. The BFR-RS for BFR that can trigger L1 / L2 mobility can be associated with one L1 / L2 mobility candidate cell, and a new C-RNTI to be used as a new UE identity can be allocated for handover to the candidate cell. The priority of the candidate cells for BFR triggered L1 / L2 mobility can be configured.

[0141] RRC messages, such as RRCReconfiguration, can provide an indication of enabling / disabling BFR triggered L1 / L2 mobility per serving cell or per cell group, which can be configured based on the UE capability indication. A one-bit indication of the UE's ability to support BFR triggered L1 / L2 mobility can be defined per UE or per frequency band or per frequency band combination or per FR and sent by the UE in the UECapabilityInformation message upon network request.

[0142] At operation 1410, the UE performs BFD on a BFD-RS set (or multiple) for a serving cell. When the number of beam failure instance indications sent from the physical layer reaches a configured threshold before a configured timer expires, the UE declares a beam failure for the BFD-RS set.

[0143] At operation 1415, if a beam failure is detected on the BFD-RS set of the TRP for the serving cell (e.g., SpCell or SCell), the UE can trigger BFR by initiating the transmission of a MAC CE or SR. If at operation 1405 BFR-triggered L1 / L2 mobility is enabled in the configuration, the UE can recover the beam failure through L1 / L2 mobility; otherwise, that is, if BFR-triggered L1 / L2 mobility is not enabled, the UE can recover the beam failure through a conventional BFR process.

[0144] For BFR triggered L1 / L2 mobility, if uplink grant is configured for the target cell, the UE triggers BFR by initiating transmission of a MAC CE or SR to the current serving cell or the target cell. If at least one BFR for only one BFD-RS set has been triggered and not cancelled for the SpCell for which the evaluation of candidate beams according to the requirements specified in 3GPP standard specification TS 38.133 has been completed, if UL-SCH resources are available for new transmission and if the UL-SCH resources can accommodate the MAC CE plus its subheader as a result of the LCP, the UE instructs the multiplexing and assembly entity to generate a MAC CE and send the MAC CE in a MAC PDU.

[0145] Otherwise, if UL-SCH resources are not available for new transmission, the UE triggers SR for beam failure recovery.

[0146] The MAC CE can include a beam failure indication, and / or a suitable new beam (or multiple beams) for recovery (if any), and / or a HO request for BFR triggered L1 / L2 mobility. The beam failure indication can include whether the beam failure is detected on the SpCell or on a specific SCell, and / or if two BFD-RS sets are configured, whether the beam failure is detected for the serving cell on only one BFD-RS set or on both BFD-RS sets, and / or whether a suitable new beam is available. A suitable new beam for recovery can be a beam whose L1 measurement for the associated RS is greater than or equal to a configured threshold. The L1-measurement can be configured as L1-RSRP, and / or SINR, and / or BLER, and / or CQI, and / or other quality metrics determined based on SSB or CSI-RS measurements, and / or any combination of these metrics. In another example, a suitable new beam for recovery can be a beam whose L1 measurement for an associated RS is greater than or equal to a configured threshold for at least a configured duration and / or for at least a configured number of consecutive times.

[0147] In one example, the latest measurement result before sending the MAC CE is used to select a suitable new beam. A suitable new beam (or beams) is selected from the BFR-RS set (or beams) associated with the BFD-RS set in which the beam failure is detected and / or from the BFR-RS (or beams) configured for L1 / L2 mobility triggered by BRD for the serving cell. If a suitable new beam is available, the corresponding RS index is indicated.

[0148] In one example, if the UE requests handover to any of the candidate cells, an explicit HO request can be indicated in the MAC CE, and for each candidate cell, a suitable new beam for recovery is selected from the BFR-RS (or multiple) configured for BRD triggered L1 / L2 mobility, and the new beam is indicated in the MAC CE. Alternatively, if a suitable new beam for recovery is selected from the BFR-RS (or multiple) configured for BRD triggered L1 / L2 mobility and indicated in the MAC CE, the UE implicitly indicates a HO request, and the candidate cell is the cell associated with the indicated suitable new beam. In this case, the target cell for BFR triggered L1 / L2 mobility can be selected by the network from the candidate cells for which the suitable new beam is indicated.

[0149] In another example, if the UE requests handover to a specific candidate cell, an explicit HO request can be indicated in the MAC CE, for which a suitable new beam for recovery is selected from the BFR-RS (or multiple) configured for BRD-triggered L1 / L2 mobility and the new beam is indicated in the MAC CE. The cell ID of the target cell selected by the UE can be indicated. Alternatively, if only one suitable new beam for recovery is selected from the BFR-RS (or multiple) configured for BRD-triggered L1 / L2 mobility and indicated in the MAC CE, the UE implicitly indicates a HO request, and the target cell is the cell associated with the indicated suitable new beam.

[0150] For target cell selection from the pool of L1 / L2 mobility candidate cells, the UE can select a target cell for which a BFR-RS (or multiple) for BFR-triggered L1 / L2 mobility is configured and for which a suitable new beam is available. If multiple cells are eligible, the UE can randomly select a target cell; and / or the UE can select the target cell according to the configured priority; and / or the UE can select in the order of the additional cell providing the second TRP, the SCell and all other candidate cells from high to low priority level; and / or the UE can sort the eligible cells according to the configured metric and select the cell ranked first.

[0151] In another example, in the case where two BFR-RS sets are configured, where one BFR-RS set is used for a TRP from a SpCell and a second BFR-RS set is used for a second TRP from an additional cell other than the SpCell, if at least one BFR of the BFD-RS set associated with the TRP of the SpCell has been triggered and not canceled, and an evaluation of candidate beams has been completed for it according to the requirements specified in the 3GPP standard specification TS 38.133, the UE selects the additional cell providing the second TRP as the target cell to recover the beam failure detected on the SpCell.

[0152] At operation 1420, upon receiving a PDCCH indicating an uplink grant for a new transmission of a HARQ process for transmission of a MAC CE, the UE considers that the BFR is successfully completed, sets the beam failure counter (BFI_COUNTER) of the BFD-RS set to 0, and cancels all triggered BFRs of the BFD-RS set. In one example, if the PDCCH addresses a C-RNTI associated with a L1 / L2 mobility candidate cell, the UE regards it as a HO command for the candidate cell. In another example, an explicit HO command can be included in a DCI format carried by a received PDCCH. For a TA for a new transmission to a target cell, in one example, the TA can be included in a DCI format carried by a received PDCCH. In another example, the TA for a new transmission to a target cell can be indicated in a MAC CE in a PDSCH scheduled by a received PDCCH. In yet another example, the UE can apply a TA pre-configured for a target cell in an L1 / L2 mobility configuration at operation 1405.

[0153] At operation 1425, the UE switches to the target cell and applies the target cell configuration. Specifically, the UE monitors the PDCCH in all CORESETs of the target cell and receives the PDSCH and aperiodic CSI-RS resources in the CSI-RS resource set using the same antenna port quasi-co-location parameters as the antenna port quasi-co-location parameters associated with the corresponding selected RS associated with the target cell (i.e., the appropriate new beam for the target cell indicated in the MAC CE at operation 1415). The UE sends PUSCH, PUCCH, and SRS using the same spatial domain filter as the spatial domain filter corresponding to the selected RS associated with the target cell (i.e., the appropriate new beam for the target cell indicated in the MAC CE at operation 1415).

[0154] In another embodiment, L1 / L2 based inter-cell mobility can be triggered by BFR with random access, such as Fig.15 shown.

[0155] Fig.15 1 is a flow chart showing a method 1500 for UE behavior in a BFR-triggered L1 / L2-based inter-cell mobility procedure with random access according to an embodiment of the present disclosure. The method 1500 may be performed by a UE (e.g., Figure 1 111-116) as shown. Fig.15 The embodiment of method 1500 shown in FIG. 1 is for illustration only. Fig.15 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0156] At operation 1505, the UE receives an RRC configuration, such as RRCReconfiguration, for BFR-triggered L1 / L2 mobility from the serving gNB. The RRC message can provide L1 / L2 mobility configuration per serving cell or per cell group, which can include a pool of candidate cells, and information included in ServingCellConfigCommon and / or ServingCellConfig and / or system information about each candidate cell. Candidate cells can include SpCells, SCells (or multiple), additional cells that provide a second TRP in inter-cell multi-TRP operation, and any other inter-DU intra-CU cells.

[0157] RRC messages, such as RRCReconfiguration can provide BFD / BFR configuration per serving cell or per cell group, which can include BFD-RS sets, BFR-RS sets, BFD / BFR related parameters, and information included in RadioLinkMonitoringConfig and / or BeamFailureRecoveryConfig and / or BeamFailureRecoveryRSConfig. The gNB can configure the UE with one set of BFD-RS (i.e., SSB and / or periodic CSI-RS and / or aperiodic CSI-RS and / or semi-persistent CSI-RS) or two sets of BFD-RS for multi-TRP operation, each associated with a TRP, and one TRP can come from an additional cell other than the serving cell. The BFR-RS for BFR that can trigger L1 / L2 mobility can be associated with one L1 / L2 mobility candidate cell. Dedicated RACH resources and / or information included in the BeamFailureRecoveryConfig to be used in the random access procedure on the L1 / L2 mobility candidate cell can be configured to be associated with the candidate cell and / or associated with the BFR-RS(s) for BFR triggered L1 / L2 mobility. A new C-RNTI to be used as the new UE identity can be allocated for handover to the candidate cell. Priorities of candidate cells for BFR triggered L1 / L2 mobility can be configured.

[0158] RRC messages, such as RRCReconfiguration, can provide an indication to enable / disable BFR triggered L1 / L2 mobility per serving cell or per cell group, which can be configured based on the UE capability indication. A one-bit indication of the UE's ability to support BFR triggered L1 / L2 mobility can be defined per UE or per frequency band or per frequency band combination or per FR and sent by the UE in the UECapabilityInformation message upon network request.

[0159] At operation 1510, the UE performs BFD on a BFD-RS set (or multiple) for a serving cell. When the number of beam failure instance indications sent from the physical layer reaches a configured threshold before a configured timer expires, the UE declares a beam failure for the BFD-RS set.

[0160] At operation 1515, if a beam failure is detected on at least one BFD-RS set of a TRP for a serving cell (e.g., SpCell or SCell), then if BFR-triggered L1 / L2 mobility is enabled in the RRC configuration at operation 1505, the UE can trigger BFR by initiating a random access procedure on the selected target cell to recover the beam failure through L1 / L2 mobility. The UE can recover the beam failure via L1 / L2 mobility with random access, for the following example but not limited thereto.

[0161] In such an example, if two BFR-RS sets are configured, then for the SpCell for which candidate beams have been evaluated according to the requirements specified in the 3GPP standard specification TS 38.133, at least one BFR for only one BFD-RS set has been triggered and not canceled.

[0162] In such an example, if two BFR-RS sets are configured, BFR is triggered for both BFD-RS sets of the SpCell, and the BFR process is not successfully completed for any BFD-RS set (i.e., the MAC entity has not sent a MAC PDU containing a BFR MAC CE, or has not received a PDCCH scheduling a new transmission).

[0163] In such an example, if one BFR-RS set is configured and beam failure is detected on the BFR-RS set for the SpCell.

[0164] In order to recover beam failure via L1 / L2 mobility, for target cell selection from the L1 / L2 mobility candidate cell pool, the UE can select a target cell to perform a random access procedure, for which BFR-RS (or multiple) for BFR-triggered L1 / L2 mobility is configured and the L1 measurement of at least one BFR-RS is greater than or equal to the configured threshold. The L1-measurement can be L1-RSRP, and / or SINR, and / or BLER, and / or CQI, and / or other quality metrics determined based on SSB and / or CSI-RS measurements, and / or any combination of these metrics.

[0165] In another example, the L1 measurement of at least one BFR-RS for BFR triggered L1 / L2 mobility is greater than or equal to a configured threshold for at least a configured duration and / or for at least a configured number of consecutive times. In one example, the latest measurement result before sending the MAC CE is used. If multiple cells are eligible, the UE can randomly select a target cell; and / or the UE can select the target cell according to the configured priority; and / or the UE can select in the order of the additional cell providing the second TRP, the SCell and all other candidate cells from high to low priority level; and / or the UE can sort the qualified cells according to the configured metric and select the cell ranked first.

[0166] In another example, in the case where two BFR-RS sets are configured, where one BFR-RS set is used for a TRP from a SpCell and the second BFR-RS set is used for a second TRP from an additional cell other than the SpCell, if at least one BFR of the BFD-RS set associated with the TRP of the SpCell has been triggered and not canceled, wherein an evaluation of candidate beams according to the requirements specified in 3GPP standard specification TS 38.133 has been completed for the SpCell, the UE recovers from the beam failure by initiating a random access procedure on the additional cell providing the second TRP.

[0167] If dedicated RACH resources (e.g., random access preamble and / or PRACH opportunity) are configured for the target cell or for the BFR-RS (or multiple) associated with the target cell, the UE can perform a contention-free random access to the target cell. Otherwise, the UE can perform a contention-based random access procedure. If both 2-step and 4-step RA type random access resources are configured and the RSRP of the downlink path loss reference is higher than msgA-RSRP-Threshold, or if only 2-step RA type random access resources are configured, the UE selects 2-step RA; otherwise, the UE selects 4-step RA.

[0168] If a random access procedure on the target cell is initiated for SpCell beam failure recovery; and if RA triggered by BFR is configured for the target cell; and if ra-PrioritizationTwoStep is configured, the UE sets the variable PREAMBLE_POWER_RAMPING_STEP to powerRampingStepHighPriority included in ra-PrioritizationTwoStep; if scalingFactorBI is configured in ra-PrioritizationTwoStep, the UE sets the variable ScalingFactor_BI to scalingFactorBI. If the UE performs a 4-step RA; and if RA triggered by BFR is configured for the target cell, the UE starts beamFailureRecoveryTimer (if configured); and applies parameters powerRampingStep, preambleReceivedTargetPower and preambleTransMax (if configured).

[0169] If the UE performs a 4-step RA; and if beamFailureRecoveryTimer is running or is not configured; and if in operation 1505 contention-free random access resources for BFR-triggered L1 / L2 mobility associated with any one of the SSBs and / or CSI-RSs have been explicitly configured by RRC; and if at least one of an SSB whose SS-RSRP among the SSBs in the configured BFR-RSs is higher than an SSB whose SS-RSRP is higher than rsrp-ThresholdSSB or a CSI-RS whose CSI-RSRP among the CSI-RSs in the configured BFR-RSs is higher than rsrp-ThresholdCSI-RS is available, the UE selects an SSB whose SS-RSRP among the SSBs is higher than rsrp-ThresholdSSB or a CSI-RS whose CSI-RSRP among the CSI-RSs is higher than rsrp-ThresholdCSI-RS. The UE sets PREAMBLE_INDEX to the ra-PreambleIndex corresponding to the selected SSB or CSI-RS from the set of random access preambles configured in the dedicated RA resources for BFR triggered L1 / L2 mobility. If a CSI-RS is selected and there is no ra-PreambleIndex associated with the selected CSI-RS, the UE sets PREAMBLE_INDEX to the ra-PreambleIndex corresponding to the SSB in the configured BFR-RS that is quasi-co-located with the selected CSI-RS.

[0170] For contention-free random access, the UE sends a random access preamble using the new C-RNTI associated with the target cell. Once the contention-free random access preamble is sent, the UE starts the ra-ResponseWindow configured for RA on the target cell in the BFR triggered L1 / L2 mobility and monitors PDCCH transmissions on the search space configured for RA on the target cell in the BFR triggered L1 / L2 mobility identified by the new C-RNTI while the ra-ResponseWindow is running. For PDCCH monitoring and for corresponding PDSCH reception, the UE assumes the same antenna port quasi-co-location parameters as those associated with the selected SSB or CSI-RS in the random access preamble transmission until the UE receives a MAC CE activation command for TCI state. If a PDCCH is received and addressed to the new C-RNTI, the UE considers the random access procedure to be successfully completed.

[0171] For contention-based random access, the UE sends a random access preamble using the calculated RA-RNTI associated with the PRACH opportunity in which the random access preamble is sent. Once the contention-based random access preamble is sent, the UE starts the ra-ResponseWindow configured for the common RA procedure for the target cell and monitors the PDCCH for the target cell identified by the RA-RNTI while the ra-ResponseWindow is running. If a PDCCH is received and addressed to the RA-RNTI and if the RAR contains a MAC subPDU with a random access preamble identifier corresponding to the sent PREAMBLE_INDEX, the UE considers that the RAR is received successfully.

[0172] In the case where 4-step contention-based RA and / or contention-free RA is performed, once the RAR is successfully received, if the UE is configured to send MAC CE for BFR-triggered L1 / L2 mobility during the RA process on the target cell; or, if beam failure is detected on two BFR-RS sets of the serving cell, the UE uses the uplink grant included in the RAR to send MAC CE in a subsequent uplink transmission (i.e., Msg3) to indicate that beam failure is detected on the corresponding BFR-RS set (or multiple). In the case where 2-step contention-based RA and / or contention-free RA is performed, if the UE is configured to send MAC CE for BFR-triggered L1 / L2 mobility during the RA process on the target cell; or, if beam failure is detected on two BFR-RS sets of the serving cell, the UE uses the configured uplink grant to send MAC CE in MsgA to indicate that beam failure is detected on the corresponding BFR-RS set.

[0173] The MAC CE can include a beam failure indication, and / or a suitable new beam (or multiple beams) for recovery (if any), and / or a HO request for BFR triggered L1 / L2 mobility. The beam failure indication can include whether the beam failure is detected on the SpCell or on a specific SCell, and / or if two BFD-RS sets are configured, whether the beam failure is detected for the serving cell on only one BFD-RS set or on both BFD-RS sets, and / or whether a suitable new beam is available. A suitable new beam for recovery can be a beam whose L1 measurement for the associated RS is greater than or equal to a configured threshold. The L1 measurement can be configured as L1-RSRP, and / or SINR, and / or BLER, and / or CQI, and / or other quality metrics determined based on SSB and / or CSI-RS measurements, and / or any combination of these metrics.

[0174] In another example, a suitable new beam for recovery can be a beam whose L1 measurement for the associated RS is greater than or equal to a configured threshold for at least a configured duration and / or for at least a configured number of consecutive times. In one example, the latest measurement result before sending the MAC CE is used to select a suitable new beam. A suitable new beam (or beams) is selected from a BFR-RS set (or multiple) associated with a BFD-RS set in which a beam failure is detected and / or from a BFR-RS configured for L1 / L2 mobility triggered by a BRD for a serving cell. If a suitable new beam is available, the corresponding RS index is indicated.

[0175] At operation 1520, upon successful completion of the random access procedure to the target cell, the UE considers the BFR to be complete, sets the beam failure counter (BFI_COUNTER) to 0, and stops the beamFailureRecoveryTimer (if running).

[0176] At operation 1525, the UE switches to the target cell and applies the target cell configuration. Specifically, the UE monitors the PDCCH in all CORESETs of the target cell and uses the same antenna port quasi-co-location parameters as the antenna port quasi-co-location parameters associated with the SSB or CSI-RS selected in the random access preamble transmission or the antenna port quasi-co-location parameters associated with the selected RS associated with the target cell (i.e., the appropriate new beam indicated in the MAC CE in the Msg3 or MsgA transmission of operation 1515) to receive the PDSCH and aperiodic CSI-RS resources in the CSI-RS resource set until the UE receives a MAC CE activation command for the TCI state. The UE sends PUSCH, PUCCH, and SRS using the same spatial domain filter corresponding to the SSB or CSI-RS selected in the random access preamble code transmission or the spatial domain filter corresponding to the selected RS associated with the target cell (i.e., the appropriate new beam indicated in the MAC CE in the Msg3 or MsgA transmission of operation 1515) until the UE receives a MAC CE activation command for the TCI state.

[0177] Similar to BFR-triggered L1 / L2-based inter-cell mobility, when HO failure occurs, such as L3 mobility failure, CHO failure, L1 / L2-based inter-cell mobility failure, UE can also trigger L1 / L2-based inter-cell mobility to a new target cell. Fig.14 and Fig.15 An embodiment in which BFR is replaced by HO failure recovery.

[0178] In one embodiment, the configuration of the BFR triggered L1 / L2 based inter-cell mobility procedure without / with random access at operation 1405 / 1505 can be included in the configuration of the candidate cells for L1 / L2 mobility, for example, in the IE ServingCellConfig. In one example, the configuration for BFR triggered L1 / L2 based inter-cell mobility is included in the IE BeamFailureRecoveryHO-Config in ServingCellConfig as follows. The maximum number of candidate cells for enabling BFR triggered L1 / L2 based inter-cell mobility is indicated by maxNrofBFR-HO-Cells, which can be 8. The maximum number of candidate beams in the BFR-RS set for BFR triggered L1 / L2 based inter-cell mobility is indicated by maxNrofCandidateBeamsh0, which can be 16. The field beamFailureRecoveryHO-RA can include parameters in the BeamFailureRecoveryConfig in the RRC specification. Table 2 shows the beam failure recovery HO configuration information element. Table 3 shows the description of beam failure recovery HO configuration information elements.

[0179]

Table 2

[0180]

[0181]

[0182]

[0183]

Table 3

[0184]

[0185]

[0186] Fig.16 An example of a BFR-HO MAC CE 1600 according to an embodiment of the present disclosure is shown. Fig.16 The embodiment of the BFR-HO MAC CE 1600 shown in FIG. 1 is for illustration only.

[0187] Fig.17 Another example of a BFR-HO MAC CE 1700 according to an embodiment of the present disclosure is shown. Fig.17 The embodiment of the BFR-HO MAC CE 1700 shown in FIG. 1 is for illustration only.

[0188] In one embodiment, the MAC CE sent by the UE at operation 1415 / 1515 can be identified by a MAC subheader with an LCID or by a MAC subheader with an eLCID. The MAC CE can be composed of any combination of the following fields. Fig.16 and Fig.17 Two examples are shown in Fig.16 and 17 , define the following contents.

[0189] SP: This field indicates whether a beam failure is detected on the BFD-RS set (or multiple) for the SpCell or SCell. The SP field set to 1 indicates that a beam failure is detected on the BFD-RS set (or multiple) for the SpCell; otherwise, the field is set to 0.

[0190] C: This field indicates whether the beam failure is detected on only one BFD-RS set or on both BFD-RS sets for the serving cell. A C field set to 1 indicates that if two BFD-RS sets are configured, the beam failure is detected on both BFD-RS sets for the serving cell. A C field set to 0 indicates that if two BFD-RS sets are configured, the beam failure is detected on only one BFD-RS set for the serving cell. If only one BFD-RS set is configured, the C field is set to 0.

[0191] HO Request: This field indicates whether the UE requests handover when the MAC CE is sent in a BFR triggered L1 / L2 mobility operation without random access. The HO Request field set to 1 indicates that the UE requests handover to one of the candidate cells (or multiple cells) whose candidate RSs are indicated in the MAC CE in the BFR triggered L1 / L2 mobility operation without random access; otherwise, the HO Request field is set to 0. If the MAC CE is sent in a BFR triggered L1 / L2 mobility operation with random access, this field is reserved with the R bit.

[0192] AC: This field indicates that the (Cell) ID field and the Candidate RS ID field are present in this octet. If at least one of an SSB with SS-RSRP higher than rsrp-ThresholdBFR or rsrp-ThresholdSSB among the SSBs in the candidate beam list for the candidate cell or a CSI-RS with CSI-RSRP higher than rsrp-ThresholdBFR or rsrp-ThresholdCSI-RS among the CSI-RS in the candidate beam list for the candidate cell is available, the AC field is set to 1; otherwise, this field is set to 0. If the AC field is set to 1, the Cell ID field and the Candidate RS ID field are present. If the AC field is set to 0, the R bit is present instead.

[0193] ID: This field indicates the identity of the BFD-RS set. If this octet corresponds to the first BFD-RS set associated with the TRP from the SpCell, this field is set to 0. If this octet corresponds to the second BFD-RS set associated with the second TRP from the SpCell or with the TRP from an additional cell other than the SpCell, this field is set to 1. For serving cells that are not configured with two BFD-RS sets, this field is set to 0;

[0194] Cell ID: This field indicates the index of the candidate cell, which is configured by BeamFailureRecoveryHO-CellId. If MAC CE is sent in a BFR-triggered L1 / L2 mobility operation with random access, this field is reserved with the R bit.

[0195] Candidate RS ID: This field is set to the index of an SSB with an SS-RSRP higher than rsrp-ThresholdBFR or rsrp-ThresholdSSB among the SSBs in the candidate beam list for the candidate cell, or to the index of a CSI-RS with a CSI-RS higher than rsrp-ThresholdBFR or rsrp-ThresholdCSI-RS among the CSI-RS in the candidate beam list for the candidate cell. The index of an SSB or CSI-RS is the index of the entry in the candidate beam list corresponding to the SSB or CSI-RS. Index 0 corresponds to the first entry in the candidate beam list, index 1 corresponds to the second entry in the list, and so on. The length of this field is 6 bits;

[0196] R: Reserved bit, set to "0".

[0197] For UEs in connected mode, mobility is controlled by the network with help from the UE to maintain good connection quality. Based on measurements of the radio link quality of the serving cell and neighboring cell (or cells) reported by the UE, when the UE is experiencing a degraded connection to the serving cell, the network can switch the UE to a neighboring cell that can provide better radio conditions. In Release 15 NR, basic mechanisms and procedures for network-controlled mobility in connected mode were developed. In Release 16 NR, enhancements to network-controlled mobility in connected mode were introduced to mitigate connection interruptions during the switching process. Specifically, two enhanced switching mechanisms, called CHO and DAPS, were developed.

[0198] For mobility in connected mode, handover is initiated by the network based on L3 (layer 3) measurements via high-layer signaling (e.g., RRC messages). However, this process involves more delay, signaling overhead, and interruption time, which may become a critical issue in some scenarios with frequent handovers, such as high-speed vehicles and UEs in FR2 deployments. It is necessary to reduce the overhead and / or delay and interruption time in the handover process. This brings the need for L1 / L2 (layer 1 / layer 2) inter-cell mobility, through which handover can be triggered by L1 / L2 signaling based on L1 measurements.

[0199] More specifically, L1 / L2-based inter-cell mobility refers to a network-controlled mobility mechanism that switches the UE from a source cell to a target cell via inter-cell beam switching triggered by L1 / L2 signaling, wherein the beam switching decision is based on L1 measurements of beams between neighboring cells.

[0200] In Release 18, new work items have been agreed to further enhance mobility in NR, targeting L1 / L2 based inter-cell mobility. For L1 / L2 based inter-cell mobility, the handover can be initiated / triggered / performed by beam switching indicated from the physical layer. It is expected to specify the operation of MAC processes, such as HARQ processes, during L1 / L2 handover.

[0201] In this disclosure, it is specified how the MAC process including the HARQ process operates during L1 / L2 based inter-cell mobility. Full MAC reset and partial MAC reset operations for L1 / L2 triggered mobility are included.

[0202] For one embodiment, Fig.18 The L1 / L2 based inter-cell mobility procedure with full MAC reset / reconfiguration / (re)establishment is shown for the UE behavior.

[0203] Fig.181800 is a flowchart showing a method 1800 for UE behavior in L1 / L2 based mobility process with MAC reset / reconfiguration / (re)establishment according to an embodiment of the present disclosure. The method 1800 may be performed by a UE (e.g., Figure 1 111-116) as shown. Fig.18 The embodiment of method 1800 shown in FIG. 1 is for illustration only. Fig.18 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0204] exist Fig.18 In operation 1805, the UE receives an RRCReconfiguration message (or messages) for L1 / L2-based mobility configuration from the serving gNB, including candidate cell PCI and / or logical ID, and / or transmission configuration indicator (TCI) state configuration, and / or measurement and reporting configuration, and / or public / dedicated serving cell configuration for the candidate cell.

[0205] At operation 1810, the UE sends an RRCReconfigurationComplete message to the serving gNB. At operation 1815, the UE performs measurements on the SSB(s) and / or CSI-RS(s) of the serving cell and the candidate cells, and reports to the serving gNB individual or joint measurement results including the L1-RSRP(s) of the serving cell and the candidate cells. At operation 1820, the UE receives L1 / L2 signaling from the serving gNB that triggers HO to the target cell. At operation 1825, the UE performs HO to the target cell using MAC reset / reconfiguration / (re)establishment, and applies the target cell configuration pre-configured by the RRCReconfiguration message.

[0206] In one example of operation 1825, if the target cell configuration includes reconfiguration with synchronization; and / or if the random access procedure is performed for L1 / L2 handover to the target cell, the UE triggers a reset / reconfiguration / (re)establishment of the MAC entity. In another example, if the NW requests / indicates a MAC reset / reconfiguration / (re)establishment for L1 / L2 handover to the target cell in a pre-configured L1 / L2 mobility configuration at operation 1805, or requests / indicates a MAC reset / reconfiguration / (re)establishment for L1 / L2 handover to the target cell in an L1 / L2HO command through an RRC message or MAC CE or DCI using an explicit or implicit indication of a MAC reset / reconfiguration / (re)establishment at operation 1820, the UE triggers a reset / reconfiguration / (re)establishment of the MAC entity.

[0207] In yet another example, if the target cell configuration of operation 405 includes a MAC configuration, for example, mac-CellGroupConfig, the UE performs a MAC reset / reconfiguration / (re)establishment.

[0208] In one example, if the HO command received at operation 1820 explicitly or implicitly indicates that the HO is inter-DU, the UE performs a complete MAC reset / reconfiguration / (re)establishment and / or performs a PDCP sequence number (SN) and superframe number (HFN) reset for the RLC-AM bearer and / or for the RLC-UM bearer, and / or performs a PDCP / RLC entity reconfiguration / (re)establishment. In an example, if the target cell and the source cell are from different cell groups (e.g., configured with different cell group IDs) by explicit indication; or if the target cell is not one of the SCells configured in the cell group of the source cell; or if the target cell and the source cell are associated with different cell group configurations; or the HO command indicates that the cell group configuration ID is to be applied to a target cell that is different from the cell group configuration ID of the source cell, the UE is able to know that the HO is inter-DU.

[0209] If a full MAC reset is triggered, the MAC entity may: (1) initialize Bj for each logical channel to zero; (2) stop (if running) all timers except the MBS broadcast DRX timer; (3) consider all TimeAlignmentTimer, inactivePosSRS-TimeAlignmentTimer and cg-SDT-TimeAlignmentTimer (if configured) as expired and perform corresponding actions; (4) set the NDI of all uplink HARQ processes to the value 0; (5) set the NDI of all HARQ process IDs to the value 0 for monitoring PDCCH in sidelink resource allocation mode 1; (6) stop the ongoing random access process (if any); (7) discard the explicitly signaled contention-free random access resources for 4-step RA type and 2-step RA type (if any); (8) flush the Msg3 buffer; (9) flush the MSGA buffer; (10 ) cancel the triggered scheduling request process (if any); (11) cancel the triggered buffer status report process (if any); (12) cancel the triggered power headroom report process (if any); (13) cancel the triggered consistent LBT failure (if any); (14) cancel the triggered BFR (if any); (15) cancel the triggered sidelink buffer status report process (if any); (16) cancel the triggered preemption buffer status report process (if any); (17) cancel the triggered timing advance report process (if any); (18) cancel the triggered recommended bit rate query process (if any); (19) cancel the triggered configured uplink grant confirmation (if any); (20) cancel the triggered configured sidelink grant confirmation (if any); (21) cancel the triggered expected protection symbol query (if any); (22) cancel the triggered positioning measurement gap activation / deactivation request process (if any); (23) cancel the triggered SDT process (if any); (24) except for the DL being used for MBS broadcasting In addition to the HARQ process, flush the soft buffers used for all DL HARQ processes; (25) for each DL HARQ process, treat the next received transmission of the TB as the original first transmission; (26) release the temporary C-RNTI (if any); and (27) reset all LBT_COUNTERs.

[0210] If MAC reconfiguration is triggered, the UE reconfigures the MAC primary configuration of the cell group of the target cell according to mac-CellGroupConfig in the target cell configuration received in operation 1805 .

[0211] If MAC (re)establishment is triggered, in one example, the UE creates a MAC entity for the cell group of the target cell having the same configuration as the MAC entity for the source cell group. In another example, the UE creates a MAC entity for the cell group of the target cell according to the mac-CellGroupConfig in the target cell configuration received in operation 1805. In yet another example, the UE applies a default MAC cell group configuration as specified in the 3GPP standard specification.

[0212] Fig.19 1900 is a flowchart showing a method 1900 for UE behavior in L1 / L2 based mobility process without MAC reset / reconfiguration / (re)establishment according to an embodiment of the present disclosure. The method 1900 may be performed by a UE (e.g., Figure 1 111-116) as shown. Fig.19 The embodiment of method 1900 shown in FIG. 1 is for illustration only. Fig.19 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0213] For one embodiment, Fig.19 The L1 / L2 based inter-cell mobility procedure without MAC reset / reconfiguration / (re)establishment or with partial MAC reset is shown for the UE behavior in FIG.

[0214] exist Fig.19 In operation 1905, the UE receives an RRCReconfiguration message (or messages) for L1 / L2-based mobility configuration from the serving gNB, including a candidate cell PCI and / or logical ID, and / or a transmission configuration indicator (TCI) state configuration, and / or a measurement and reporting configuration, and / or a public / dedicated serving cell configuration for the candidate cell.

[0215] At operation 1910, the UE sends an RRCReconfigurationComplete message to the serving gNB. At operation 1915, the UE performs measurements on the SSB(s) and / or CSI-RS(s) of the serving cell and the candidate cells, and reports to the serving gNB individual or joint measurement results including the L1-RSRP(s) of the serving cell and the candidate cells. At operation 1920, the UE receives L1 / L2 signaling from the serving gNB triggering HO to the target cell. At operation 1925, the UE performs HO to the target cell without MAC reset / reconfiguration / (re)establishment or with partial MAC reset, and applies the target cell configuration pre-configured by the RRCReconfiguration message.

[0216] In one example of operation 1925, if the NW requests / indicates no MAC reset / reconfiguration / (re)establishment for L1 / L2 handover to the target cell in a pre-configured L1 / L2 mobility configuration in operation 1905 or in an L1 / L2 HO command using an explicit or implicit indication of no MAC reset / configuration / (re)establishment via an RRC message or MACCE or DCI in operation 1920, the UE does not perform a MAC reset / reconfiguration / (re)establishment.

[0217] As an example, if the target cell configuration does not include reconfiguration with synchronization; and / or if the random access procedure is not performed for L1 / L2 switching to the target cell, the UE does not perform MAC reset / reconfiguration / (re)establishment. For another example, if any process-specific indication is included in the pre-configured L1 / L2 mobility configuration at operation 1905 or in the L1 / L2HO command via an RRC message or MAC CE or DCI at operation 1920, such as, for example, a HARQ recovery indication and / or an LCP no reset indication, the UE does not perform MAC reset / reconfiguration / (re)establishment. In yet another example, if it is predefined in the specification that MAC reset / reconfiguration / (re)establishment is not performed for L1 / L2 mobility operations, the UE does not perform MAC reset / reconfiguration / (re)establishment. In another example, if the target cell configuration of operation 1805 does not include a MAC configuration, such as mac-CellGroupConfig, the UE does not perform MAC reset / reconfiguration / (re)establishment.

[0218] For another example, if the HO command received at operation 1820 explicitly or implicitly indicates that the HO is intra-DU, the UE does not perform a MAC reset / reconfiguration / (re)establishment and / or performs a partial MAC reset / reconfiguration / (re)establishment and / or does not perform a PDCP sequence number (SN) and superframe number (HFN) reset for an RLC-AM bearer and / or for an RLC-UM bearer and / or does not perform a PDCP / RLC entity reconfiguration / (re)establishment. In one example, the UE may know that the HO is intra-DU if the target cell and the source cell are from the same cell group (e.g., configured with the same cell group ID) by explicit indication; or if the target cell is one of the SCells configured in the cell group of the source cell; or if the target cell and the source cell are associated with the same cell group configuration; or the HO command indicates that the cell group configuration ID is to be applied to the target cell that is the same as the cell group configuration ID of the source cell.

[0219] If the MAC is not reset or partially reset, the MAC entity may: (1) not initialize Bj for each logical channel to zero; (2) not stop (if running) all timers except the MBS broadcast DRX timer; (3) keep all TimeAlignmentTimers, inactivePosSRS-TimeAlignmentTimer and / or cg-SDT-TimeAlignmentTimer (if configured) running and perform corresponding actions; (4) not change the NDI used for all uplink HARQ processes; (5) not change the NDI for all HARQ process IDs monitoring PDCCH in sidelink resource allocation mode 1; (6) not cancel the triggered scheduling request process (if any); (7) not cancel the triggered buffer status report process (if any); and / or (8) maintain the soft buffer for all DL HARQ processes except the DL HARQ process being used for MBS broadcast.

[0220] If MAC reconfiguration is not triggered, the UE does not reconfigure the MAC primary configuration of the cell group of the target cell.

[0221] In one embodiment of operation 525, the HARQ process can be interrupted by the L1 / L2 handover to the target cell, for example, the DL / UL HARQ process is not completed before the UE performs the L1 / L2 handover to the target cell. For this case, the NW can enable HARQ recovery so that once the UE successfully switches to the target cell, the unfinished HARQ process (or processes) can be continued.

[0222] Fig. 201 is a flow chart showing a method 2000 for UE behavior for DL ​​HARQ recovery under L1 / L2 based mobility according to an embodiment of the present disclosure. The method 2000 may be performed by a UE (e.g., Figure 1 111-116) as shown. Fig. 20 The embodiment of method 2000 shown in FIG. 2 is for illustration only. Fig. 20 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0223] Fig.21 2 is a flowchart showing a method 2100 of BS behavior for DL ​​HARQ recovery based on L1 / L2 mobility according to an embodiment of the present disclosure. The method 2100 may be performed by a BS (e.g., Figure 1 101-103) as shown. Fig.21 The embodiment of method 2100 shown in FIG. 2 is for illustration only. Fig.21 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0224] Fig. 20 and Fig.21 Embodiments of DL HARQ recovery for UE behavior and BS behavior are shown separately.

[0225] From the perspective of the UE, in operation 2005, the UE explicitly or implicitly receives a DL HARQ recovery indication. In one example, HARQ recovery can be enabled by an explicit one-bit indication in a pre-configured L1 / L2 mobility configuration or in a L1 / L2 HO command via an RRC message or MAC CE or DCI. Alternatively, the L1 / L2HO command via an RRC message or MAC CE or DCI implicitly indicates that HARQ recovery is enabled. As another example, in the L1 / L2HO command via an RRC message or MAC CE or DCI, the DL HARQ process to be resumed can be indicated by a HARQ process ID. As yet another example, in the L1 / L2 HO command via an RRC message or MAC CE or DCI, a bitmap having a length of the total number of configured or ongoing DL HARQ processes can be used, wherein 1 indicates a request to resume the HARQ process represented by the bit, and 0 indicates not to resume the HARQ process represented by the bit.

[0226] At operation 2010, if DL HARQ recovery is enabled, the UE maintains data in a soft buffer while performing L1 / L2 HO to a target cell. In one example, if ACK / NACK for a HARQ process has not been sent before L1 / L2 HO is triggered, the UE sends ACK / NACK feedback for the HARQ process in Msg3 or Msg5 or MsgA in a random access procedure for L1 / L2 HO and / or in a confirmation MAC CE for L1 / L2 HO. In another example, if a bundling operation is performed before L1 / L2 HO is triggered and is not completed with a configured number of repetitions for the HARQ process, the UE sends ACK / NACK feedback for the HARQ process in Msg3 or Msg5 or MsgA in a random access procedure for L1 / L2 HO and / or in a confirmation MAC CE for L1 / L2 HO.

[0227] In operation 2015, the UE receives a downlink allocation indication and associated HARQ information for each HARQ process to be resumed after a successful L1 / L2 HO to the target cell. For dynamic scheduling, the UE receives the downlink allocation in a DCI format in the PDCCH. For semi-persistent scheduling (SPS), the UE receives an activation indication of the configured scheduling in a DCI format addressed to the CS-RNTI in the PDCCH. In one example, the HARQ process to be resumed is implicitly indicated by using the same HARQ process ID, that is, the HARQ process ID does not change before and after the L1 / L2 HO, and the NDI is set to indicate that this is a retransmission. In this way, the UE considers that the HARQ process with the unchanged ID is resumed. Alternatively, a new HARQ process ID can be used, but it is linked to the old ID for the HARQ process that was not completed before the L1 / L2 HO, and the UE regards the HARQ process with the new ID as a resumption of the HARQ process with the old ID.

[0228] In operation 2020, the UE receives a retransmission (or multiple) for each recovered HARQ process and decodes the data. In one example of resuming the bundling operation in the recovered HARQ process, the UE is able to receive the remaining number of repetitions that were not sent before the L1 / L2 HO was triggered; alternatively, the UE is able to receive the configured number of repetitions for the recovered bundling operation. For each recovered HARQ process, the MAC entity assigns the TB (or multiple) and the associated HARQ information received from the physical layer to the HARQ process indicated by the associated HARQ information. The MAC entity instructs the physical layer to combine the received data with the data currently in the soft buffer for the TB and attempt to decode the combined data. If the data is successfully decoded for the TB, the MAC entity delivers the decoded MAC PDU to the decomposition and demultiplexing entity; otherwise, the MAC entity instructs the physical layer to replace the data in the soft buffer for the TB with the data that the MAC entity attempts to decode.

[0229] The UE sends ACK / NACK feedback on each restored HARQ process at operation 2025. The MAC entity instructs the physical layer to generate ACK / NACK for data in the TB for each restored HARQ process that is not configured with HARQ feedback prohibition or defined as a HARQ process with no feedback.

[0230] From the perspective of the BS, at operation 2105, the BS explicitly or implicitly sends a DL HARQ recovery indication. In one example, HARQ recovery can be enabled by an explicit one-bit indication in a pre-configured L1 / L2 mobility configuration or in a L1 / L2 HO command via an RRC message or MAC CE or DCI. Alternatively, the L1 / L2HO command via an RRC message or MAC CE or DCI implicitly indicates that HARQ recovery is enabled. As another example, in the L1 / L2HO command via an RRC message or MAC CE or DCI, the DL HARQ process to be resumed can be indicated by a HARQ process ID. As yet another example, in the L1 / L2 HO command via an RRC message or MAC CE or DCI, a bitmap having a length of the total number of configured or ongoing DL HARQ processes can be used, wherein 1 indicates a request to resume the HARQ process represented by the bit, and 0 indicates not to resume the HARQ process represented by the bit.

[0231] At operation 2110, if the UE has not sent ACK / NACK feedback for the HARQ process before the L1 / L2 HO is triggered, the BS receives ACK / NACK feedback for the HARQ process in Msg3, Msg5, or MsgA in the random access procedure for the L1 / L2 HO and / or in the confirmation MAC CE for the L1 / L2 HO. In another example, if the bundling operation is performed before the L1 / L2 HO is triggered and the transmission of the number of repetitions configured for the HARQ process is not completed, the BS receives ACK / NACK feedback for the HARQ process in Msg3, Msg5, or MsgA in the random access procedure for the L1 / L2 HO and / or in the confirmation MAC CE for the L1 / L2 HO.

[0232] At operation 2115, the BS schedules downlink allocations for each HARQ process to be resumed after a successful L1 / L2 HO to the target cell. The BS is able to determine the HARQ process to be resumed based on the HARQ feedback received at operation 2110. For dynamic scheduling, the BS indicates the downlink allocation in a DCI format in the PDCCH. For semi-persistent scheduling (SPS), the BS activates the configured scheduling in a DCI format addressed to the CS-RNTI in the PDCCH. In one example, the HARQ process to be resumed is implicitly indicated by using the same HARQ process ID, i.e., the HARQ process ID does not change before and after the L1 / L2 HO, and the NDI is set to indicate that this is a retransmission. In this way, the BS indicates that the HARQ process with the unchanged ID is resumed. Alternatively, a new HARQ process ID can be used, but the new HARQ process ID is linked to the old ID for the HARQ process that was not completed before L1 / L2 HO, and the BS indicates the HARQ process with the new ID as a resumption of the HARQ process with the old ID.

[0233] At operation 2120, the BS sends a retransmission (or multiple) for each resumed HARQ process. In one example of resuming bundling operation in the resumed HARQ process, the BS sends the remaining repetition number that was not sent before the L1 / L2 HO was triggered; alternatively, the BS can send the configured number of bundling operation repetitions for resumption.

[0234] In operation 2125, the BS receives ACK / NACK feedback for each restored HARQ process.

[0235] Fig. 22 2 is a flowchart showing a method 2200 for UE behavior for UL HARQ recovery under L1 / L2 based mobility according to an embodiment of the present disclosure. The method 2200 may be performed by a UE (e.g., Figure 1 111-116) as shown. Fig. 22 The embodiment of method 2200 shown in FIG. 2 is for illustration only. Fig. 22 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0236] Fig.23 2300 is a flowchart showing a BS behavior for UL HARQ recovery under L1 / L2 based mobility according to an embodiment of the present disclosure. The method 2300 may be performed by a BS (e.g., Figure 1 101-103) as shown. Fig.23 The embodiment of method 2300 shown in FIG. 2 is for illustration only. Fig.23 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0237] Fig. 22 and Fig.23 Embodiments of UL HARQ recovery are shown for UE behavior and BS behavior, respectively.

[0238] From the perspective of the UE, in operation 2205, the UE explicitly or implicitly receives a UL HARQ recovery indication. In one example, HARQ recovery can be enabled by an explicit one-bit indication in a pre-configured L1 / L2 mobility configuration or in a L1 / L2 HO command via an RRC message or MAC CE or DCI. Alternatively, the L1 / L2HO command via an RRC message or MAC CE or DCI implicitly indicates that HARQ recovery is enabled. As another example, in the L1 / L2HO command via an RRC message or MAC CE or DCI, the UL HARQ process to be resumed can be indicated by a HARQ process ID. As yet another example, in the L1 / L2 HO command via an RRC message or MAC CE or DCI, a bitmap having a length of the total number of configured or ongoing UL HARQ processes can be used, wherein 1 indicates a request to resume the HARQ process represented by the bit, and 0 indicates not to resume the HARQ process represented by the bit.

[0239] At operation 2210, if UL HARQ recovery is enabled, the UE maintains data in the corresponding HARQ buffer and / or sets the NDI for all uplink HARQ processes to be unchanged while performing L1 / L2 HO to the target cell. In one example, if the UL HARQ process is performed using the configured grant before the L1 / L2 HO is triggered, and the configuredGrantTimer and / or cg-RetransmissionTimer for the corresponding HARQ process is running, the UE stops the configuredGrantTimer and / or cg-RetransmissionTimer and regards the corresponding HARQ process as pending. In another example, if the bundling operation is performed before the L1 / L2 HO is triggered and the number of repetitions configured for the HARQ process is not completed, the UE regards the corresponding HARQ process as pending.

[0240] At operation 2215, the UE receives an uplink grant and associated HARQ information for each HARQ process to be resumed after a successful L1 / L2 HO to the target cell. The HARQ entity delivers the uplink grant and the HARQ information of the TB to the identified HARQ process and indicates that the identified HARQ process triggers retransmission. For dynamic scheduling, the UE receives an uplink grant indication in a DCI format in the PDCCH. For semi-persistent scheduling (SPS), the UE receives an uplink grant indication for the configured grant in a DCI format addressed to the CS-RNTI in the PDCCH. In one example, the HARQ process to be resumed is implicitly indicated by using the same HARQ process ID, i.e., the HARQ process ID does not change before and after the L1 / L2 HO, and the NDI is set to indicate that retransmission is required.

[0241] In this way, the UE considers the HARQ process with the unchanged ID to be resumed. Alternatively, a new HARQ process ID can be used, but linked to the old ID used for the HARQ process that was not completed before the L1 / L2 HO, and the UE considers the HARQ process with the new ID to be a resumption of the HARQ process with the old ID. For the HARQ process (or processes) that are not resumed, the NDI is set to indicate a new transmission.

[0242] At operation 2220, the UE sends a retransmission (or multiple) for each resumed HARQ process using the associated uplink grant. In one example of resuming bundling operation in the resumed HARQ process, the UE can send the remaining number of repetitions that were not sent before the L1 / L2 HO was triggered; alternatively, the UE can send the configured number of repetitions for the resumed bundling operation. If the uplink grant is addressed to the CS-RNTI; or if the uplink grant is addressed to the C-RNTI and the identified HARQ process is configured for the configured uplink grant, then if the LBT failure indication is not received from the lower layer when the retransmission is performed, the HARQ entity starts or restarts the configuredGrantTimer and / or cg-RetransmissionTimer (if configured) at the beginning of the first symbol of the PUSCH transmission for the corresponding HARQ process.

[0243] At operation 2225, the UE receives downlink feedback information for each resumed HARQ process. If the HARQ process receives downlink feedback information, the HARQ process may stop the cg-RetransmissionTimer (if running); if confirmation is indicated, the HARQ process may stop the configuredGrantTimer (if running). If the configuredGrantTimer for the HARQ process expires, the HARQ process may stop the cg-RetransmissionTimer (if running).

[0244] From the perspective of the BS, in operation 2305, the BS explicitly or implicitly sends a UL HARQ recovery indication. In one example, HARQ recovery can be enabled by an explicit one-bit indication in a pre-configured L1 / L2 mobility configuration or in an L1 / L2 HO command via an RRC message or MAC CE or DCI. Alternatively, the L1 / L2HO command via an RRC message or MAC CE or DCI implicitly indicates that HARQ recovery is enabled. As another example, in the L1 / L2HO command via an RRC message or MAC CE or DCI, the UL HARQ process to be resumed can be indicated by a HARQ process ID. As yet another example, in the L1 / L2 HO command via an RRC message or MAC CE or DCI, a bitmap having a length of the total number of configured or ongoing UL HARQ processes can be used, wherein 1 indicates a request to resume the HARQ process represented by the bit, and 0 indicates not to resume the HARQ process represented by the bit.

[0245] At operation 2310, the BS sends an uplink grant indication and associated HARQ information for each HARQ process to be resumed after the UE successfully completes the L1 / L2 HO to the target cell. For dynamic scheduling, the BS sends the uplink grant indication in the DCI format in the PDCCH. For semi-persistent scheduling (SPS), the BS sends an uplink grant indication for the configured grant in the DCI format addressed to the CS-RNTI in the PDCCH. In one example, the HARQ process to be resumed is implicitly indicated by using the same HARQ process ID, that is, the HARQ process ID does not change before and after the L1 / L2 HO, and the NDI is set to indicate that retransmission is required. In this way, the BS indicates that the HARQ process with the unchanged ID is resumed.

[0246] Alternatively, a new HARQ process ID can be used, but linked to the old ID used for the HARQ process that was not completed before L1 / L2HO, and the BS indicates the HARQ process with the new ID as a resumption of the HARQ process with the old ID. For the HARQ process (or processes) that are not resumed, the NDI is set to indicate the new transmission.

[0247] At operation 2315, the BS receives a retransmission (or multiple) for each resumed HARQ process. In one example of resuming bundling operation in the resumed HARQ process, the BS can receive the remaining number of repetitions that were not sent before the L1 / L2 HO was triggered; alternatively, the BS can receive the number of repetitions configured for the resumed bundling operation.

[0248] In operation 2320, the BS transmits downlink feedback information for each restored HARQ process.

[0249] Fig.24 2400 for timing advance management for multiple TRPs and beam management according to an embodiment of the present disclosure. The method 2400 may be performed by a UE (e.g., Figure 1 111-116) as shown. Fig.24 The embodiment of method 2400 shown in FIG. 2 is for illustration only. Fig.24 One or more of the components shown in the can be implemented in dedicated circuits 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.

[0250] like Fig.24 As shown, the method 2400 starts at 2402. In step 2402, the UE receives a second TAG ID and a PDCCH order associated with a second BS from a first BS.

[0251] In one embodiment, the PDCCH order indicates at least one of an SSB index associated with the second BS or a TCI state associated with the second BS.

[0252] In one embodiment, the first BS is a first TRP in a serving cell; and the second BS is a second TRP in the serving cell or in a cell having a PCI other than the serving cell PCI.

[0253] Then, in step 2404, the UE initiates a CFRA procedure in response to receiving the PDCCH command.

[0254] Then, in step 2406, the UE sends an RA preamble to the second BS.

[0255] Next, in step 2408, the UE receives a TAC included in the RAR or in the MAC CE for the second BS.

[0256] In one embodiment, the MAC CE includes a TA associated with a second TAG ID corresponding to the second BS, the MAC CE includes a TA associated with a coresetPoolIndex corresponding to the second BS, or the MAC CE includes a TA associated with a TCI state ID corresponding to the second BS. In one embodiment, the MAC CE is identified by a MAC subheader including an LCID or an eLCID.

[0257] In one embodiment, the MAC CE includes a first TA and a TA offset associated with a first TAG ID for a first BS; the processor is further configured to: determine a second TA for a second BS based on the first TA and the TA offset; and the MAC CE is identified by a MAC subheader including an LCID or eLCID.

[0258] Finally, in step 2410, the UE applies the TAC and starts a second time alignment timer corresponding to a second TAG ID associated with the second BS.

[0259] In one embodiment, the UE determines whether a second time alignment timer for a second TAG associated with the second BS has expired. The UE stops UL transmission to the second BS, clears DL allocation associated with the second BS, or releases UL resources associated with the second BS based on determining that the second time alignment timer has expired.

[0260] In one embodiment, the UE determines whether a first time alignment timer associated with a first BS in a serving cell and a second time alignment timer associated with a second BS in the serving cell have expired. In one embodiment, the UE stops UL transmission, releases UL resources associated with the first BS and the second BS, and clears DL allocations associated with the first BS and the second BS based on determining that the first time alignment timer and the second time alignment timer have expired.

[0261] In one embodiment, the UE sends a UE capability indication, which indicates whether the UE supports multiple TAGs or a single TAG for multi-TRP operation for a serving cell.

[0262] In one embodiment, the UE associates a first set of TCI states or a first coresetPoolIndex with a first TAG ID for a first BS and associates a second set of TCI states or a second coresetPoolIndex with a second TAG ID for a second BS.

[0263] The above flow charts illustrate example methods that can be implemented according to the principles of the present disclosure, and various changes can be made to the methods shown in the flow charts herein. For example, although shown as a series of steps, the various steps in each figure can overlap, occur in parallel, occur in a different order, or occur multiple times. In another example, steps can be omitted or replaced by other steps.

[0264] Although the present disclosure has been described using exemplary embodiments, various changes and modifications may be suggested to those skilled in the art. The present disclosure is intended to cover these changes and modifications that fall within the scope of the appended claims. None of the descriptions in this application should be interpreted 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 patent subject matter is defined by the claims.

Claims

1. A user equipment (UE), comprising: a transceiver configured to receive, from a first base station (BS), a second timing advance group (TAG) identifier (ID) and a physical downlink control channel (PDCCH) command associated with a second BS; as well as a processor operatively coupled to the transceiver, the processor configured to initiate a contention-free random access (CFRA) procedure in response to receiving a PDCCH command, The transceiver is further configured as: Sending a random access (RA) preamble to the second BS, and receiving a timing advance (TA) command (TAC) included in a random access response (RAR) or a medium access control element (MAC CE) for the second BS, and The processor is further configured to apply the TAC and start a second time alignment timer corresponding to a second TAG ID associated with the second BS.

2. The UE according to claim 1, wherein: The PDCCH command indicates at least one of a synchronization signal / physical broadcast channel (PBCH) block (SSB) index associated with the second BS and a transmission configuration indicator (TCI) state associated with the second BS.

3. The UE according to claim 1, wherein: The MAC CE includes a TA associated with a second TAG ID corresponding to the second BS, The MAC CE includes the TA associated with the coresetPoolIndex corresponding to the second BS, or The MAC CE includes a TA associated with a TCI state ID corresponding to the second BS, and The MAC CE is identified by a MAC subheader including a logical channel identifier (LCID) or an enhanced LCID (eLCID).

4. The UE according to claim 1, wherein: The MAC CE includes a first TA and a TA offset associated with a first TAG ID for a first BS; The processor is further configured to: determine a second TA for a second BS based on the first TA and the TA offset; and The MAC CE is identified by a MAC subheader including a logical channel identifier (LCID) or an enhanced LCID (eLCID).

5. The UE according to claim 1, wherein: The processor is also configured to: determining whether a second time alignment timer for a second TAG associated with the second BS has expired; and Based on determining that the second time alignment timer expires: stopping uplink (UL) transmission to the second BS, clearing the DL allocation associated with the second BS, or UL resources associated with the second BS are released.

6. The UE according to claim 1, wherein: The processor is also configured to: determining whether a first time alignment timer associated with a first BS in a serving cell and a second time alignment timer associated with a second BS in the serving cell have expired; and Based on determining that the first time alignment timer and the second time alignment timer expire: Stop uplink (UL) transmission, releasing UL resources associated with the first BS and the second BS, and Downlink (DL) allocations associated with the first BS and the second BS are cleared.

7. The UE according to claim 1, wherein: The first BS is a first transmit reception point (TRP) in the serving cell; and The second BS is a second TRP in the serving cell or in a cell having a physical cell identifier (PCI) other than the serving cell PCI.

8. The UE according to claim 1, wherein: The processor is further configured to associate a first set of TCI states or a first coresetPoolIndex with a first TAG ID for a first BS and associate a second set of TCI states or a second coresetPoolIndex with a second TAG ID for a second BS.

9. A method of a user equipment (UE), the method comprising: receiving, from a first base station (BS), a second timing advance group (TAG) identifier (ID) and a physical downlink control channel (PDCCH) command associated with a second BS; Initiating a contention free random access (CFRA) procedure in response to receiving a PDCCH command; sending a random access (RA) preamble to the second BS; receiving, for the second BS, a timing advance (TA) command (TAC) included in a random access response (RAR) or a medium access control element (MAC CE); as well as The TAC is applied and a second time alignment timer corresponding to a second TAG ID associated with the second BS is started.

10. The method according to claim 9, wherein: The PDCCH command indicates at least one of a synchronization signal / physical broadcast channel (PBCH) block (SSB) index associated with the second BS and a transmission configuration indicator (TCI) state associated with the second BS.

11. A first base station (BS), comprising: a processor configured to generate a second timing advance group (TAG) identifier (ID) and a physical downlink control channel (PDCCH) command associated with a second BS; as well as a transceiver operably coupled to the processor, the transceiver configured to send a second TAG ID and a PDCCH command associated with a second BS to a user equipment (UE), in: In response to receiving the PDCCH command, a random access (RA) preamble is sent to the second BS based on a contention-free random access (CFRA) procedure; For the second BS, a timing advance (TA) command (TAC) included in a random access response (RAR) or a medium access control element (MAC CE) is applied; and A second time alignment timer corresponding to a second TAG ID associated with the second BS is started.

12. The BS according to claim 11, wherein: The PDCCH order indicates at least one of a synchronization signal / physical broadcast channel (PBCH) block (SSB) index associated with the second BS and a transmission configuration indicator (TCI) state associated with the second BS, wherein: The MAC CE includes a TA associated with a second TAG ID corresponding to the second BS, The MAC CE includes the TA associated with the coresetPoolIndex corresponding to the second BS, or The MAC CE includes a TA associated with a TCI state ID corresponding to the second BS, and The MAC CE is identified by a MAC subheader including a logical channel identifier (LCID) or an enhanced LCID (eLCID).

13. The first BS according to claim 11, wherein: The MAC CE includes a first TA and a TA offset associated with a first TAG ID for a first BS; and The MAC CE is identified by a MAC subheader including a logical channel identifier (LCID) or an enhanced LCID (eLCID).

14. The first BS according to claim 11, wherein: The first BS is a first transmit reception point (TRP) in the serving cell; and The second BS is a second TRP in the serving cell or in a cell having a physical cell identifier (PCI) other than the serving cell PCI.

15. A method of a first base station (BS), the method comprising: generating a second timing advance group (TAG) identifier (ID) and a physical downlink control channel (PDCCH) order associated with a second BS; as well as sending a second TAG ID and a PDCCH command associated with a second BS to a user equipment (UE); in: In response to receiving the PDCCH command, a random access (RA) preamble is sent to the second BS based on a contention-free random access (CFRA) procedure; For the second BS, a timing advance (TA) command (TAC) included in a random access response (RAR) or a medium access control element (MAC CE) is applied; and A second time alignment timer corresponding to a second TAG ID associated with the second BS is started.

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