Method and apparatus for RACH-free condition handover in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. A user equipment (UE) receives and stores a candidate cell configuration including an execution condition of a conditional cell handover to a candidate cell. Upon determining that the execution condition is satisfied, the UE selects a candidate cell as a target cell for conditional cell handover. The UE determines whether a valid timing advance (TA) and a valid uplink (UL) grant for an initial uplink (UL) transmission to a target cell are available. When the valid TA and the valid UL grant are available, the UE transmits an initial UL transmission to the target cell using the valid TA and the valid UL grant. When the valid TA is not available, the UE performs a random access procedure on the target cell. When the valid UL grant is unavailable, the UE sends a scheduling request to the target cell.

Description

Technical Field

[0001] This disclosure generally relates to wireless communication systems, and more specifically, to mobility in wireless communication systems, for example, but not limited to. Background Technology

[0002] Fifth-generation (5G) mobile communication technology defines a wide frequency band, enabling high transmission rates and new services. It can be implemented not only in the "sub-6 GHz" band, such as 3.5 GHz, but also in the "above 6 GHz" band, including 28 GHz and 39 GHz, known as millimeter wave (mmWave). Furthermore, sixth-generation (6G) mobile communication technology (called "super 5G systems") is being considered in terahertz (THz) bands (e.g., the 95 GHz to 3 THz band) to achieve transmission rates fifty times faster than 5G and ultra-low latency one-tenth that of 5G.

[0003] At the outset of the development of 5G mobile communication technology, in order to support services and meet the performance requirements associated with enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC), there were ongoing standardization efforts regarding the following aspects: beamforming and massive multiple-input multiple-output (MIMO) in mmWave to mitigate radio wave path loss and increase radio wave transmission distance; dynamic operation supporting parameter sets (e.g., operating multiple subcarrier spacings) and time slot formats for efficient utilization of mmWave resources; initial access technologies to support multi-beam transmission and broadband; definition and operation of bandwidth portions (BWP); new channel coding methods such as low-density parity-check (LDPC) codes for large-volume data transmission and polar codes for highly reliable transmission of control information; L2 preprocessing; and network slicing for providing dedicated networks for specific services.

[0004] Currently, given the services that 5G mobile communication technology needs to support, there is ongoing discussion about improvements and performance enhancements to the initial 5G mobile communication technology, and there is already physical layer standardization for technologies such as: Vehicle-to-Everything (V2X) for assisting autonomous vehicle driving decisions based on information about the location and status of vehicles transmitted by vehicles and for enhancing user convenience; New Radio Unlicensed (NR-U) for system operation designed to comply with various regulatory requirements in unlicensed frequency bands; New Radio (NR) User Equipment (UE) power saving; Non-Terrestrial Networks (NTN) for providing coverage in areas where communication with terrestrial networks is not possible, as well as positioning.

[0005] Furthermore, standardization is underway in the air interface architecture / protocol for technologies such as: Industrial Internet of Things (IIoT) supporting new services through interconnection and convergence with other industries; Integrated Access and Backhaul (IAB) providing nodes for network service area extension by supporting wireless backhaul and access links in an integrated manner; mobility enhancements including conditional handover and Dual Active Protocol Stack (DAPS) handover; and two-step random access for NR (RACH for NR) to simplify the random access process. Standardization is also underway in system architecture / services for: 5G baseline architectures (e.g., service-based architectures or service-based interfaces) combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies; and Mobile Edge Computing (MEC) for receiving UE location-based services.

[0006] With the commercialization of 5G mobile communication systems, the already exponentially growing number of connected devices will connect to the communication network, thus necessitating enhanced functionality and performance of 5G mobile communication systems as well as integrated operation of connected devices. To this end, new research is planned related to: Extended Reality (XR) for effectively supporting Augmented Reality (AR), Virtual Reality (VR), Mixed Reality (MR), etc.; 5G performance improvements and complexity reduction through the utilization of Artificial Intelligence (AI) and Machine Learning (ML); AI service support; Metaverse service support; and drone communications.

[0007] Furthermore, this development of 5G mobile communication systems will serve as the foundation for not only the development of new waveforms for providing terahertz band coverage for 6G mobile communication technologies, multi-antenna transmission technologies such as full-dimensional MIMO (FD-MIMO), array antennas, and massive MIMO, metamaterial-based lenses and antennas for improving terahertz band signal coverage, high-dimensional spatial multiplexing technologies using orbital angular momentum (OAM), and reconfigurable smart surfaces (RIS), but also the development of: full-duplex technologies for improving the frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technologies for leveraging satellites and artificial intelligence (AI) from the design stage to achieve system optimization and internalize end-to-end AI support functions, and next-generation distributed computing technologies for achieving services with complexity levels exceeding the operational limits of UEs by utilizing ultra-high-performance communication and computing resources.

[0008] Mobility management operations, including network handover, represent a critical aspect of any wireless communication system. These systems include, for example, LTE and 5G New Radio (NR), as well as upcoming technologies currently being termed "6G." Mobility is currently controlled by the network with the assistance of the user equipment (UE) to maintain optimal connection quality. The network can hand over the UE to a target cell with superior signal quality.

[0009] Enhanced broadband mechanisms requiring high speed and low latency necessitate more complex handover mechanisms. Therefore, Conditional Handover (CHO) and independent Layer 1 / Layer 2 Triggered Mobility (LTM) have been introduced to provide additional conditions for specific networks or their slices, thereby improving handover speed. However, the use of these enhancements introduces its own latency, at least because the network needs to exchange some data with the UE during the handover process. Therefore, the initiation of a planned handover triggered by the network introduces its own latency, signaling overhead, and downtime.

[0010] The descriptions set forth in the Background section should not be assumed to be prior art simply because they are set forth in the Background section. The Background section may describe aspects or embodiments of this disclosure. Summary of the Invention

[0011] Technical issues

[0012] This disclosure aims to provide an efficient method for communication.

[0013] Furthermore, this disclosure aims to provide a method for managing mobility controls.

[0014] Technical solution

[0015] This disclosure provides a user equipment (UE) for facilitating communication in a wireless network. The UE includes a transceiver configured to receive a conditional cell handover configuration from a source cell for one or more execution conditions for one or more candidate cells, wherein each of the one or more execution conditions is associated with a conditional cell handover to a corresponding candidate cell. The UE includes a processor operatively coupled to the transceiver, configured to determine whether one or more execution conditions are met, select a candidate cell as the target cell for the conditional cell handover based on the determination that the execution conditions of the candidate cell are met, and determine whether a valid timing advance (TA) and a valid UL grant for an initial uplink (UL) transmission to the target cell are available. The transceiver is further configured to transmit an initial UL transmission to the target cell using a valid TA and a valid UL grant based on the determination that a valid TA and a valid UL grant are available.

[0016] In some embodiments, the transceiver is also configured to perform a random access procedure for the target cell based on the determination that a valid TA is unavailable.

[0017] In some embodiments, the transceiver is also configured to send a scheduling request to the target cell based on the determination that a valid UL is unavailable.

[0018] In some embodiments, the conditional cell handover configuration includes at least one of TA information for initial UL transmission to the target cell and a configured UL authorization.

[0019] In some embodiments, the processor is configured to determine that the TA information is valid based on the determination that a time condition or distance condition included in the conditional cell handover configuration is met.

[0020] In some embodiments, the processor is configured to determine that the UL authorization of the configuration is valid based on the determination that a time condition included in the conditional cell handover configuration is met.

[0021] In some embodiments, the processor is configured to determine that the pair of TA information and configured UL authorization is valid based on the fact that a time condition associated with the pair of TA information and UL authorization is met.

[0022] In some embodiments, the conditional cell handover configuration includes one or more configurations of UL authorization for each candidate cell, wherein each configuration of the UL authorization is associated with a corresponding beam of one or more beams.

[0023] In some embodiments, the processor is further configured to select a beam among one or more beams based on the execution conditions of the candidate cells, and to determine that the UL authorization of the configuration associated with the selected beam is valid.

[0024] In some embodiments, the processor is further configured to perform TA estimation for a target cell based on the UE location, satellite ephemeris, and public TA information, and to determine that the estimated TA is valid based on the validity of the public TA information and satellite ephemeris provided in the conditional cell handover configuration.

[0025] Another aspect of this disclosure provides a method performed by a user equipment (UE) in a wireless network. The method includes receiving a conditional cell handover configuration from a source cell, comprising one or more execution conditions for one or more candidate cells, wherein each of the one or more execution conditions is associated with a conditional cell handover to a corresponding candidate cell; determining whether the one or more execution conditions are satisfied; selecting a candidate cell as the target cell for the conditional cell handover based on the determination that the execution conditions of the candidate cell are satisfied; determining whether a valid timing advance (TA) and a valid UL grant for an initial uplink (UL) transmission to the target cell are available; and, based on the determination that the valid TA and valid UL grant are available, sending the initial UL transmission to the target cell using the valid TA and valid UL grant.

[0026] In some embodiments, the method further includes performing a random access procedure on the target cell based on the determination that a valid TA is unavailable.

[0027] In some embodiments, the method further includes sending a scheduling request to the target cell based on the determination that a valid UL authorization is unavailable.

[0028] In some embodiments, the conditional cell handover configuration includes at least one of TA information for initial UL transmission to the target cell and a configured UL authorization.

[0029] In some embodiments, determining whether a valid TA and a valid UL authorization are available includes determining that the TA information is valid based on determining that a time condition or distance condition included in the conditional cell handover configuration is met.

[0030] In some embodiments, determining whether a valid TA and a valid UL authorization are available includes determining that the configured UL authorization is valid based on the time condition included in the conditional cell handover configuration being met.

[0031] In some embodiments, determining whether a valid TA and a valid UL authorization are available includes determining that the pair of TA information and configured UL authorization is valid based on the fact that a time condition associated with the pair of TA information and UL authorization is met.

[0032] In some embodiments, the conditional cell handover configuration includes one or more configurations of UL authorization for each candidate cell, wherein each configuration of the UL authorization is associated with a corresponding beam of one or more beams.

[0033] In some embodiments, the method further includes selecting a beam among one or more beams based on the execution conditions of the candidate cells, and determining that the UL authorization of the configuration associated with the selected beam is valid.

[0034] In some embodiments, the method further includes performing TA estimation for a target cell based on UE location, satellite ephemeris and public TA information, and determining that the estimated TA is valid based on the validity of the public TA information and satellite ephemeris provided in the conditional cell handover configuration.

[0035] Another aspect of this disclosure provides a base station (BS) for facilitating communication in a wireless network. The BS includes a transceiver configured to receive measurement reports from a user equipment (UE). The BS includes a processor operatively coupled to the transceiver, the processor being configured to determine readiness for conditional cell handover based on the measurement reports and to generate a conditional cell handover configuration including one or more execution conditions for one or more candidate cells. Each of the one or more execution conditions is associated with a conditional cell handover to a corresponding candidate cell, and the transceiver is further configured to transmit the conditional configuration to the UE.

[0036] In some embodiments, the conditional cell handover configuration includes at least one of timing advance (TA) information for the initial uplink (UL) transmission to each of the one or more candidate cells and a configured UL authorization.

[0037] Beneficial effects

[0038] This disclosure provides efficient methods for communication.

[0039] According to this disclosure, a method for RACH-free handover is provided. Attached Figure Description

[0040] Figure 1 An example of a wireless network according to an embodiment is shown.

[0041] Figure 2A An example of a wireless transmission path according to an embodiment is shown.

[0042] Figure 2B An example of a wireless reception path according to an embodiment is shown.

[0043] Figure 3A An example of a user equipment (“UE”) according to an embodiment is shown.

[0044] Figure 3B An example of a base station (“BS”) according to an embodiment is shown.

[0045] Figure 4 An example procedure for cell handover without RACH conditions is shown according to an embodiment.

[0046] Figure 5 An example procedure for signaling a handover in a cell without RACH conditions is shown.

[0047] In one or more embodiments, not all of the components depicted in each figure may be required, and one or more embodiments may include additional components not shown in the figures. Variations in the arrangement and type of components may be made without departing from the scope of this subject matter disclosure. Additional components, different components, or fewer components may be utilized within the scope of this subject matter disclosure. Detailed Implementation

[0048] The detailed description set forth below in conjunction with the accompanying drawings is intended to describe various embodiments and is not intended to represent the only embodiments in which the subject matter can be practiced. Rather, this detailed description includes specific details to provide a thorough understanding of the subject matter of the invention. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the scope of this disclosure. Therefore, the drawings and description are to be considered illustrative rather than restrictive in nature. The same reference numerals denote the same elements.

[0049] The following description pertains to certain embodiments for the purpose of illustrating the innovative aspects of this disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in a variety of different ways. The examples in this disclosure are based on current 5G NR systems, advanced 5G (5G-A) and its further improvements and advancements, as well as upcoming 6G communication systems. However, in various cases, the described embodiments can also be implemented in any device, system, or network capable of transmitting and receiving radio frequency (RF) signals according to other technologies, such as 3G and 4G systems or further embodiments thereof. For example, the principles of this disclosure can be applied to Global System for Mobile Communications (GSM), GSM / General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunking Radio (TETRA), Wideband CDMA (W-CDMA), Evolved Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High-Speed ​​Packet Access (HSPA), High-Speed ​​Downlink Packet Access (HSDPA), High-Speed ​​Uplink Packet Access (HSUPA), Evolved High-Speed ​​Packet Access (HSPA+), Long Term Evolution (LTE), Enhanced 5G NR, AMPS, or other known signals for communication within wireless, cellular, or IoT networks, such as one or more of the aforementioned systems utilizing 3G, 4G, 5G, 6G, or further implementations thereof. This technology can also be associated with and applied to any of the existing or proposed IEEE 802.11 standards, Bluetooth standards, and other wireless communication standards.

[0050] As described above, wireless communication is one of the most commercially successful innovations in history. Aside from automation software, robotics, machine learning, and other software that automates the use of these types of communication devices, the absolute number of wireless or cellular subscribers continues to grow. A year ago, the number of subscribers for all types of communication services exceeded five billion. This number has long been surpassed and continues to grow rapidly. The demand for services using wireless data traffic is also increasing rapidly, partly due to the growing popularity of smartphones and other mobile data devices, such as tablets, notepad computers, netbooks, e-book readers, and dedicated machine-type devices, among consumers and businesses. It goes without saying that improvements in radio interface efficiency and coverage are crucial to meeting the high growth of mobile data traffic and supporting new applications and deployments.

[0051] To continue accommodating the rapidly increasing demand for wireless data traffic over the years and to facilitate the growth and complexity of so-called “vertical applications” (i.e., code written or generated to achieve goals specific to a user or entity, such as enterprise resource planning and customer relationship management software), 5G communication systems have been developed and are currently being commercially deployed. Advanced 5G, as defined in 3GPP Release 18, represents a further upgrade to various aspects of 5G and has already been introduced in some countries as an optimization of 5G. Development of Advanced 5G is ongoing. The development and enhancement of 5G can also provide greater overall efficiency for processing resources, including, for example, in high-intensity machine learning environments involving precision medical devices, measuring equipment, robotics, etc. Due to 5G and its anticipated successors, these devices are expected to have more robust access to one or more application programming interfaces (APIs) and other software routines and operate at faster speeds.

[0052] Among other advantages, 5G can be implemented using higher frequency bands, particularly 28 GHz or 60 GHz. More generally, such bands can include those above 6 GHz. A key benefit of these higher frequency bands is potentially significantly better data rates. One disadvantage is the requirement for line-of-sight (LOS) in some cases, the difficulty of higher frequencies penetrating barriers between the base station and the UE, and a shorter overall transmission range. When transmitting at these millimeter-wave (mmW) frequencies, 5G systems rely on more directional communication (e.g., using multiple antennas, massive MIMO implementations, transmit and / or receive beamforming, temporary power boosting, etc.). Furthermore, 5G can advantageously use lower frequency bands (such as below 6 GHz) for transmission to achieve more robust and longer-range coverage and for mobility support (including handover, etc.). As described above, various aspects of this disclosure can be applied to 5G deployments, currently developing 6G systems, and subsequent versions. The latter category can include those standards applied to the THz frequency band. To reduce radio wave propagation loss and increase transmission distance, as described in some sections, emerging technologies such as MIMO, full-dimensional MIMO (FD-MIMO), array antennas, digital and analog beamforming, massive MIMO technology, and others are discussed in various 3GPP-based standards that define implementations of 5G communication systems.

[0053] In addition, in 5G communication systems, the development of system network improvements based on advanced small cells, cloud radio access networks (RAN) ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, mobile networks, cooperative communication, coordinated multipoint (CoMP), and receiver interference cancellation are underway or have already been deployed. With the emergence of exemplary technologies such as neural network machine learning, autonomous or partially controlled electric vehicles, or hydrogen-based vehicles, these 5G advancements are expected to play potentially significant roles in their respective implementations. Other advanced access technologies under 5G that have been developed or are under development include, for example, advanced coding and modulation (ACM) schemes using hybrid frequency shift keying (FSK), frequency orthogonal amplitude modulation (FQAM), and sliding window superposition coding (SWSC); and advanced access technologies using filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA).

[0054] Also under development are the principles of 6G technology, which could be commercially available by the end of the decade or even earlier. 6G systems are expected to incorporate most or all of the improvements brought by 5G and further enhance them, as well as add new features and capabilities. 6G is also expected to exploit unmapped areas of bandwidth to increase overall capacity. As noted, the principles of this disclosure are also intended to apply to 6G systems and beyond.

[0055] Figure 1 An example of a wireless network 100 according to an embodiment is shown. Figure 1 The embodiment of the wireless network 100 shown is for illustrative purposes only. Other embodiments of the wireless network 100 may be used without departing from the scope of this disclosure. It should be noted initially that the nomenclature can vary widely depending on the system. For example, in Figure 1 In this context, the term "BS" (base station) can also be referred to as eNodeB (eNB), gNodeB (gNB), or, in the commercial rollout of 6G, BS may have another name. For the purposes of this disclosure, BS and gNB are used interchangeably. Therefore, depending on the network type, the term "gNB" can refer to any component (or set of components) configured to provide wireless access to a network to remote terminals, such as a base transceiver station, radio base station, transmitting point (TP), transmitting-receiving point (TRP), terrestrial gateway, airborne gNB, satellite system, mobile base station, macrocell, microcell, WiFi access point (AP), etc. Return to Reference Figure 1 Network 100 includes BS (or gNB) 101, 102, and 103. BS 101 communicates with BS 102 and BS 103. BSs can be connected via known backhaul connections or other connection methods, such as wireless connections. BS 101 also communicates with at least one Internet Protocol (IP) based network 130. Network 130 may include the Internet, a proprietary IP network, or another network.

[0056] Similarly, depending on the type of network 100, other well-known terms may be used instead of "user equipment" or "UE," such as "mobile station," "subscriber station," "remote terminal," "wireless terminal," or "user device." For convenience, the terms "user equipment" and "UE" are used interchangeably with "subscriber station" in this patent document to refer to a remote wireless device that wirelessly accesses the gNB, whether the UE is a mobile device (such as a mobile phone or smartphone) or is generally considered to be a fixed device (such as a desktop computer, vending machine, appliance, or any device with a wireless connection compatible with network 100). Continue to refer to Figure 1BS 102 provides wireless broadband access to IP network 130 to a first plurality of user equipments (UEs) within its coverage area 120. The first plurality of UEs includes UE 111, which may be located in a small business (SB); UE 112, which may be located in an enterprise (E); UE 113, which may be located in a WiFi hotspot (HS); UE 114, which may be located in a first residence (R); UE 115, which may be located in a second residence (R); and UE 116, which may be a mobile device (M), such as a cellular phone, wireless laptop computer, wireless PDA, etc. BS 103 provides wireless broadband access to IP network 130 to a second plurality of UEs within its coverage area 125. The second plurality of UEs includes UE 115 and UE 116, which are located in both coverage areas 120 and 125. In some embodiments, one or more of BS 101-103 may communicate with each other and with UE 111-116 using 6G, 5G, LTE, LTE-A, WiMAX or other advanced wireless communication technologies.

[0057] exist Figure 1 In the diagram, as noted, the dashed lines represent the approximate extents of coverage areas 120 and 125 of BS 102 and 103, respectively, which are shown as approximately circular for illustrative and explanatory purposes only. It should be clearly understood that, depending on the configuration of the BS, the coverage areas associated with the AP (such as coverage areas 120 and 125) can have other shapes, including irregular shapes. Although Figure 1 An example of a wireless network 100 is shown, but more details can be found on other wireless networks. Figure 1 Various modifications can be made. For example, the wireless network 100 can include any number of BS / gNBs and any number of UEs in any suitable arrangement. Furthermore, BS 101 can communicate directly with any number of UEs and provide these UEs with wireless broadband access to the IP network 130. Similarly, each BS 102 or 103 can communicate directly with the IP network 130 and provide the UEs with direct wireless broadband access to the network 130. Additionally, gNBs 101, 102, and / or 103 can provide access to other or additional external networks, such as external telephone networks or other types of data networks.

[0058] It should be understood that in a 5G system, BS 101 may include multiple antennas, multiple radio frequency (RF) transceivers, transmit (TX) processing circuitry, and receive (RX) processing circuitry. BS 101 may also include a controller / processor, memory, and a backhaul or network interface. The RF transceivers can receive incoming RF signals from the antennas, such as signals transmitted by the UE in network 100. The RF transceivers can down-convert the incoming RF signals to generate intermediate (IF) or baseband signals. The IF or baseband signals are sent to the RX processing circuitry, which generates a processed baseband signal by filtering, decoding, and / or digitizing the baseband or IF signals. The RX processing circuitry then sends the processed baseband signal to the controller / processor for further processing.

[0059] The controller / processor may include control BS 101 ( Figure 1 The controller / processor is one or more processors or other processing devices that control the overall operation of the UE, RX processing circuitry, and TX processing circuitry to receive uplink signals and transmit downlink signals, based on well-known principles. The controller / processor may also support additional functions, such as more advanced wireless communication functions. For example, the controller / processor may support beamforming or directional routing operations, where outgoing signals from multiple antennas are weighted differently to effectively guide outgoing signals in a desired direction. The controller / processor may also support OFDMA operations, where outgoing signals can be assigned to subsets of different subcarriers for different receivers (e.g., different UEs 111-114). The controller / processor may support various other functions in BS 101, including combinations of MIMO and OFDMA in the same transmission opportunity. In some embodiments, the controller / processor may include at least one microprocessor or microcontroller. The controller / processor is also capable of executing programs and other processes residing in memory, such as the OS. The controller / processor may move data into or out of memory as needed for the execution process.

[0060] The controller / processor is also coupled to a backhaul or network interface. The backhaul or network interface allows BS 101 to communicate with other BSs, devices, or systems via a backhaul connection or over a network. The interface can support communication via any suitable wired or wireless connection. For example, the interface can allow BS 101 to communicate with a larger network (such as the Internet) via a wired or wireless LAN or via a wired or wireless connection. The interface can include any suitable architecture that supports communication via a wired or wireless connection, such as Ethernet or an RF transceiver. Memory is coupled to the controller / processor. A portion of the memory can include RAM, and another portion can include flash memory or other ROM.

[0061] For the purposes of this disclosure, a processor may include not only a main processor but also other hardware, firmware, middleware, or software implementations capable of performing various functions. Furthermore, the processor executing code in memory may include multiple processors and other components, and may include one or more physical memories. Therefore, for example, executable code or data may reside in different physical memories, and this embodiment remains within the spirit and scope of this disclosure.

[0062] Figure 2A An example of a wireless transmission path 200A according to an embodiment is shown. Figure 2B An example of a wireless receiving path 200B according to an embodiment is shown. In the following description, a transmitting path 200A can be implemented in a gNB / BS (such as...). Figure 1 The BS 102) is implemented, while the receive path 200B can be implemented in the UE (such as...). Figure 1 The receiving path 200B is implemented in the UE 111 (SB). However, it should be understood that the receiving path 200B can be implemented in the BS, and the transmitting path 200A can be implemented in the UE. In some embodiments, the receiving path 200B is configured to support codebook design and architecture for a system with a 2D antenna array as described in some embodiments of this disclosure. That is, each of the BS and UE includes both transmitting and receiving paths, enabling full-duplex communication such as voice sessions.

[0063] Transmission path 200A includes: a channel coding and modulation block 205 for modulating and encoding data bits into symbols; a serial-to-parallel (S-to-P) conversion block 210; an N-size inverse fast Fourier transform (IFFT) block 215 for converting N frequency-based signals back to the time domain before transmission; a parallel-to-serial (P-to-S) block 220 for serializing the parallel data blocks from IFFT block 215 into a single data stream (note that BS / UEs with multiple transmission paths can each transmit separate data streams); and a cyclic prefix addition block 225 for adding a guard interval, which can be a copy of the end portion of an orthogonal frequency domain modulation (OFDM) symbol (or any modulation scheme used) and is typically at least as long as the delay spread to mitigate the effects of multipath propagation. Alternatively, the cyclic prefix can contain data about the corresponding frame or other data unit. Next, an upconverter (UC) 230 modulates the baseband (or, in some cases, intermediate frequency (IF)) signal onto a carrier signal for use as an RF signal transmitted via an antenna.

[0064] The receive path 200B essentially comprises the opposite circuitry and includes: a downconverter (DC) 255 for removing the data stream from the carrier signal and restoring it to a baseband (or IF) data stream in other embodiments; a cyclic prefix removal block 260 for removing guard intervals (or removing intervals of varying lengths); a serial-to-parallel (S-to-P) block 265 for acquiring the data stream and parallelizing it into N data streams for faster operation; a multi-input size N Fast Fourier Transform (FFT) block 270 for converting N time-domain signals into symbols in the frequency domain; a parallel-to-serial (P-to-S) block 275 for serializing the symbols; and a channel decoding and demodulation block 280 for decoding the data and demodulating the symbols into bits using any demodulation and decoding scheme initially used to reference the modulated and encoded data of the transmit path 200A.

[0065] As another example, in Figure 2A In the transmission path 200A, channel coding and modulation block 205 receives a set of information bits, applies coding (such as low-density parity-check (LDPC) coding), and modulates the input bits (such as using quadrature phase shift keying (QPSK), quadrature amplitude modulation (QAM), orthogonal frequency domain multiple access (OFDMA), or other current or future modulation schemes) to generate a sequence of frequency domain modulation symbols. Serial-to-parallel block 210 converts (e.g., demultiplexes) the serial modulation symbols into parallel data to generate N parallel symbol streams, where, as noted, N is in BS 102 and UE 116 ( Figure 1 The size of the IFFT / FFT used is specified. An IFFT block 215 of size N performs an IFFT operation on N parallel symbol streams to generate a time-domain output signal. A parallel-to-serial block 220 converts (e.g., multiplexes) the parallel time-domain output symbols from the N-size IFFT block 215 to generate a serial time-domain signal. A cyclic prefix addition block 225 inserts a cyclic prefix into the time-domain signal. An upconverter 230 modulates (e.g., upconverts) the output of the cyclic prefix addition block 225 from baseband (or, in other embodiments, intermediate frequency IF) to an RF frequency for transmission via a wireless channel. The signal may also be filtered at baseband before conversion to the RF frequency.

[0066] The RF signal transmitted from BS 102 reaches UE 116 after passing through the wireless channel, and in UE 116 ( Figure 1The operation at BS 102 is the reverse of the operation at BS 102. Downconverter 255 (e.g., at UE 116) downconverts the received signal to baseband or IF frequency, and cyclic prefix removal block 260 removes the cyclic prefix to generate a serial time-domain baseband signal. Serial-to-parallel block 265 converts or multiplexes the time-domain baseband signal into a parallel time-domain signal. FFT block 270 of size N performs an FFT algorithm to generate N parallel frequency-domain signals. Parallel-to-serial block 275 converts the parallel frequency-domain signals into a sequence of modulated data symbols. Channel decoding and demodulation block 280 demodulates and decodes the modulated symbols to recover the original input data stream. The data stream can then be segmented and processed accordingly using the processor and its associated memory. Figure 1 Each of the BSs 101-103 can implement a transmission path 200A similar to that sent to UEs 111-116 in the downlink, and similarly, each of the BSs 101-103 can implement a reception path 200B similar to that received from UEs 111-116 in the uplink. Similarly, to achieve bidirectional signaling, each of the UEs 111-116 can implement a transmission path 200A for sending to BSs 101-103 in the uplink, and each of the UEs 111-116 can implement a reception path 200B for receiving from gNBs 101-103 in the downlink. In this way, a given UE can bidirectionally exchange signals with BSs within its range, and vice versa.

[0067] Figure 2A and Figure 2B Each component in the system can be implemented using only hardware or a combination of hardware and software / firmware. As a specific example, Figure 2A and Figure 2B At least some components can be implemented in software, while others can be implemented using configurable hardware or a combination of software and configurable hardware. For example, FFT block 270 and IFFT block 215 can be implemented as configurable software algorithms, wherein the value of size N can be modified according to the implementation. Furthermore, although described as using FFT and IFFT, this exemplary implementation is for illustrative purposes only and should not be construed as limiting the scope of this disclosure. For example, other types of transforms such as Discrete Fourier Transform (DFT) and Inverse Discrete Fourier Transform (IDFT) functions can be used instead of FFT / IFFT. It should be understood that for DFT and IDFT functions, the value of variable N can be any integer (such as 1, 2, 3, 4, etc.), while for FFT and IFFT functions, the value of variable N can be any integer a power of 2 (such as 1, 2, 4, 8, 16, etc.). Additionally, although... Figure 2A and Figure 2B An example of a wireless transmit and receive path is shown, but it is possible to modify it further. Figure 2A and Figure 2B Make various changes. For example, Figure 2A and Figure 2B The various components can be combined, further subdivided, or omitted, and additional components can be added as needed. Furthermore, Figure 2A and Figure 2B This section provides examples illustrating the types of send and receive paths that can be used in a wireless network. Any other suitable architecture can be used to support wireless communication in a wireless network. For example, [the architecture described here is missing from the original text]. Figure 2A and Figure 2B The functions performed by the modules can be executed by a processor that executes the correct code in the memory corresponding to each module.

[0068] Figure 3A A user equipment (“UE”) 300A according to an embodiment is shown (which may be, for example, Figure 1 Examples include UE 116 (or another UE). It should be emphasized that... Figure 3A The embodiment of UE 300A shown is for illustrative purposes only, and Figure 1 UEs 111-116 can have the same or similar configurations. However, UEs have a wide variety of configurations, and Figure 3A The scope of this disclosure is not limited to any particular implementation of the UE, as per UE300A. Reference is now made to... Figure 3A The UE 300A includes components such as an antenna 305 (which may be a single antenna or an array or multiple arrays in other UEs), a radio frequency (RF) transceiver 310, transmit (TX) processing circuitry 315 coupled to the RF transceiver 310, a microphone 320, and receive (RX) processing circuitry 325. The UE 300A also includes a speaker 330 coupled to the receive processing circuitry 325, a main processor 340, an input / output (I / O) interface (IF) 345 coupled to the processor 340, a keypad (or other input device) 350, a display 355, and a memory 360 coupled to the processor 340. In addition to data, the memory 360 also includes a basic operating system (OS) program 361 and one or more applications 362. In some embodiments, the display 355 may also constitute an input touchpad, and in this case, it may be bidirectionally coupled to the processor 340.

[0069] Depending on the complexity and configuration of the UE, the RF transceiver may include more than one transceiver. RF transceiver 310 receives incoming RF signals transmitted by the BS of network 100 from antenna 305. The RF transceiver transmits and receives radio data and control information. In this example, the RF transceiver is operatively coupled to processor 340 via TX processing circuitry 315 and RF processing circuitry 325. RF transceiver 310 may then down-convert the incoming RF signal to generate an intermediate frequency (IF) or baseband signal. In some embodiments, down-conversion may be performed by another device coupled to the transceiver. The IF or baseband signal is sent to RX processing circuitry 325, which generates a processed baseband signal by filtering, decoding, and / or digitizing the baseband or IF signal. RX processing circuitry 325 sends the processed baseband signal to speaker 330 (e.g., in the context of a voice call) or to main processor 340 for further processing (e.g., for web browsing data or any number of other applications). TX processing circuitry 315 receives analog or digital voice data from microphone 320, or in other cases, it may receive other outgoing baseband data (such as web data, email, or interactive video game data) from main processor 340. TX processing circuitry 315 encodes, multiplexes, and / or digitizes the outgoing baseband data to generate processed baseband or IF signals. RF transceiver 310 receives the outgoing processed baseband or IF signals from TX processing circuitry 315 and up-converts them into RF signals transmitted via antenna 305. Alternative methods and arrangements may be used to perform the same operation without departing from the spirit or scope of this disclosure.

[0070] The main processor 340 may include one or more processors or other processing devices and executes a basic OS program 361 stored in memory 360 to control the overall operation of UE 116. For example, the main processor 340 may control the RF transceiver 310, RX processing circuitry 325, and TX processing circuitry 315 to receive forward channel signals and transmit reverse channel signals according to well-known principles. In some embodiments, the main processor 340 includes at least one microprocessor or microcontroller. The transceiver 310 is coupled directly to the processor 340 or via an intermediate element. The main processor 340 is also capable of executing other processes and programs residing in memory 360, such as CLTM in a wireless communication system as described in embodiments of this disclosure. The main processor 340 may move data into or out of memory 360 as needed for the execution of the process. In some embodiments, the main processor 340 is configured to execute application 362 based on OS program 361 or in response to signals received from an operator of the BS or UE. The main processor 340 is also coupled to an I / O interface 345, which provides the UE 300A 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 main controller 340. The main processor 340 is also coupled to a keypad 350 and a display unit 355. The operator of the UE 300A can use the keypad 350 to input data into the UE 300A. The display 355 may be a liquid crystal display or other display capable of displaying text and / or at least limited graphics from a website. Memory 360 is coupled to the main processor 340. A portion of the memory 360 may include random access memory (RAM), and another portion of the memory 360 may include flash memory or other read-only memory (ROM).

[0071] Figure 3AThe UE 300A may also include additional or different types of memory, including dynamic random access memory (DRAM), non-volatile flash memory, static RAM (SRAM), cache memory at different levels, etc. While the main processor 340 may be a complex instruction set computer (CISC) based processor with one or more cores, it should be noted that in other embodiments, the processor may include multiple processors. The processor may also include a reduced instruction set computer (RISC) based processor. Various other components of the UE 300A may include separate processors, or they may be partially or wholly controlled by firmware or middleware. For example, any one or more components of the UE 300A may include one or more digital signal processors (DSPs), one or more field-programmable gate arrays (FPGAs), one or more programmable logic devices (PLDs), one or more application-specific integrated circuits (ASICs), and / or one or more system-on-a-chip (SoCs) for performing the various tasks discussed above. In some embodiments, the UE 300A may rely on middleware or firmware, whose updates may be received from time to time. For its target, which is typically compact smartphones and other UEs, the hardware design may be implemented to reflect this smaller aspect ratio. The antenna can extend from the device or be located within other UEs; it can also be embedded within the UE body. The display panel may include a layer of indium tin oxide or a similar compound to enable the display to function as a touchpad. In short, although... Figure 3A An example of UE 300A is shown, but it is possible to compare it with other models. Figure 3A Various changes may be made without departing from the scope of this disclosure. For example, Figure 3A The various components can be combined, further subdivided, or omitted, and additional components can be added as needed. As an example, the main 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). Furthermore, although... Figure 3A This may include a UE configured as a mobile phone or smartphone (e.g., Figure 1 The UE (as defined in UE 116) can be configured to operate as other types of mobile or fixed devices. For example, the UE can be incorporated into tower desktop computers, tablet computers, laptops, workstations, and servers.

[0072] Figure 3B An example of a BS 300B according to an embodiment is shown. Non-exhaustive examples of the BS 300B could be... Figure 1 An example of BS 102. As stated above, for the purposes of this disclosure, the terms BS and gNB are used interchangeably. Figure 3B The BS300B embodiment shown is for illustrative purposes only, and Figure 1 Other BSs can have the same or similar configurations. However, BS / gNBs have a wide variety of configurations, and it should be emphasized that... Figure 3B The BS shown does not limit the scope of this disclosure to any particular implementation of the BS. For example, BS 101 and BS 103 may include [missing information - likely related to specific implementations of the BS]. Figure 1 BS 102 or BS 300B (in Figure 3B They have the same or similar structures, or they can have different structures. For example... Figure 3B As shown, the BS 300B includes multiple antennas 370a-370n, multiple corresponding RF transceivers 372a-372n, transmit (TX) processing circuitry 374, and receive (RX) processing circuitry 376. The transceivers 372a-372n are coupled directly to the processor or via intermediate elements. In some embodiments, one or more of the multiple antennas 370a-370n include a 2D antenna array. The BS 300B also includes a controller / processor 378 (hereinafter referred to as "processor 378"), a memory 380, and a backhaul or network interface 382. The RF transceivers 372a-372n receive incoming RF signals from the antennas 370a-370n, such as signals transmitted by the UE or other BSs. The RF transceivers 372a-372n down-convert the corresponding incoming RF signals to generate IF or baseband signals. The IF or baseband signal is sent to the RX processing circuit 376, which generates a processed baseband signal by filtering, decoding, and / or digitizing the baseband or IF signal. The RX processing circuit 376 sends the processed baseband signal to the controller / processor 378 for further processing. The TX processing circuit 374 receives analog or digital data (such as voice data, network data, email, interactive video game data, or data used in machine learning programs) from the processor 378. The TX processing circuit 374 encodes, multiplexes, and / or digitizes the outgoing baseband data to generate a processed baseband or IF signal. RF transceivers 372a-372n receive the outgoing processed baseband or IF signal from the TX processing circuit 374 and up-convert the baseband or IF signal into an RF signal transmitted via antennas 370a-370n. It should be noted that the above is descriptive in nature; in reality, not all antennas 370-370n need to be active simultaneously.

[0073] Processor 378 may include one or more processors or other processing devices that control the overall operation of BS 300B. For example, processor 378 may control the reception of forward channel signals and the transmission of reverse channel signals by RF transceivers 372a-372n, RX processing circuitry 376, and TX processing circuitry 374 according to well-known principles. Processor 378 may also support additional functions, such as more advanced wireless communication functions. For example, processor 378 may perform blind interference sensing (BIS) processes (such as those performed by BIS algorithms) and decode the received signal after subtracting interference signals. Processor 378 may support any of a variety of other functions in BS 300B. In some embodiments, processor 378 includes at least one microprocessor or microcontroller or an array thereof. Processor 378 is also capable of executing programs and other processes residing in memory 380, such as a basic operating system (OS). Processor 378 is also capable of supporting CLTM in wireless communication systems as described in embodiments of this disclosure. In some embodiments, controller / processor 378 supports communication between entities, such as web RTC. The processor 378 can move data into or out of the memory 380 as needed during execution. The backhaul or network interface 382 allows the BS 300B to communicate with other devices or systems via a backhaul connection or network. Interface 382 can support communication via any suitable wired or wireless connection. For example, when the BS 300B is implemented as part of a cellular communication system (such as a cellular communication system supporting 5G, 5G-A, LTE, or LTE-A), interface 382 can allow the BS 102 ( Figure 1 It communicates with other BSs via wired or wireless backhaul connections. (Return to Reference) Figure 3B Interface 382 allows BS 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. Interface 382 includes any suitable architecture supporting communication via a wired or wireless connection, such as an Ethernet or RF transceiver. Memory 380 is coupled to processor 378. A portion of memory 380 may include RAM, and another portion of memory 380 may include flash memory or other ROM. In some exemplary embodiments, multiple instructions, such as a dual-spectrum exponential algorithm (BIS), may be stored in memory. The multiple instructions are configured to cause processor 378 to perform the BIS process and decode the received signal after subtracting at least one interference signal determined by the BIS algorithm.

[0074] The BS 102's transmit and receive paths are described in more detail below (in...). Figure 3BIn the example, the BS 300B (implemented using RF transceivers 372a-372n, TX processing circuitry 374, and / or RX processing circuitry 376) supports aggregated communication with Frequency Division Duplex (FDD) cells or Time Division Duplex (TDD) cells, or some combination of both. That is, communication with multiple UEs can be achieved by allocating the transceiver's uplink to a certain frequency and establishing downlinks using different frequencies (FDD). In TDD, uplink and downlink allocation is achieved by allocating certain time for uplink transmissions to the BS and other time for downlink transmissions from the BS to the UE. Although... Figure 3B This shows that it can be similar to or equivalent to BS 102 ( Figure 1 An example of BS 300B, but it is possible to... Figure 3B Various changes can be made. For example, BS 300B can include any number of... Figure 3B Each component is shown. As a specific example, an access point may include multiple interfaces 382, ​​and a processor 378 may support routing capabilities to route data between different network addresses. As another example, although for simplicity... Figure 3B The description includes a single instance of TX processing circuitry 374 and a single instance of RX processing circuitry 376, but the BS 300B may include multiple instances of each (such as one transmit or receive per RF transceiver).

[0075] As an example, LTE version 13 supports up to 16 CSI-RS (Channel State Information-Reference Signal) antenna ports, allowing the BS to be equipped with a large number of antenna elements (such as 64 or 128). In this case, multiple antenna elements are mapped to a single CSI-RS port. Furthermore, version 14 LTE supports up to 32 CSI-RS ports. For next-generation cellular systems such as 5G, the maximum number of CSI-RS ports can be even greater. CSI-RS is a reference signal sent by the BS to the UE to allow the UE to estimate the downlink radio channel quality. CSI-RS can be transmitted in any available OFDM symbols and subcarriers configured in the Radio Resource Control (RRC) message. The UE measures various radio channel quality parameters (time delay, signal-to-noise ratio, power, etc.) and reports the results to the BS.

[0076] Figure 3BThe BS 300B may also include additional or different types of memory 380, including dynamic random access memory (DRAM), non-volatile flash memory, static RAM (SRAM), different levels of cache memory, etc. While the main processor 378 may be a complex instruction set computer (CISC) based processor with one or more cores, in other embodiments, the processor may include multiple processors or an array of processors. Typically, in embodiments, the processing power and requirements of the BS may be much higher than those of a typical UE, although this is not necessary. Some BSs may include large structures on towers or other structures, and their immobility allows them to access a fixed power supply without requiring any local power, except for a backup battery in power outage-type events. The processor 378 may also include a reduced instruction set computer (RISC) based processor or an array thereof. Various other components of the BS 300B may include separate processors, or they may be partially or wholly controlled by firmware or middleware. For example, any one or more components of the BS 300B may include one or more digital signal processors (DSPs), one or more field-programmable gate arrays (FPGAs), one or more programmable logic devices (PLDs), one or more application-specific integrated circuits (ASICs), and / or one or more system-on-a-chip (SoCs) for performing the various tasks described above. In some implementations, the BS 300B may rely on middleware or firmware, whose updates may be received from time to time. In some configurations, the BS may include multi-layered stacked motherboards to accommodate greater processing demands and process channel state information (CSI) and other data received from nearby UEs.

[0077] In short, although Figure 3B An example of a BS is shown, but it is possible to compare it with other BS examples. Figure 3B Various changes may be made without departing from the scope of this disclosure. For example, Figure 3B The various components within can be combined, further subdivided, or omitted, and additional components can be added as needed. As an example mentioned above, the main processor 378 can be divided into multiple processors, such as one or more central processing units (CPUs) and one or more graphics processing units (GPUs)—or, in some cases, multiple motherboards for enhanced functionality. The BS can also include a large amount of solid-state drive (SSD) memory or magnetic hard disks for long-term data retention. Furthermore, while one example of the BS 300B is a tower-based structure, this description is merely exemplary, and the BS can exist in other forms based on well-known principles.

[0078] The following provides a description of various aspects of this disclosure. The text and corresponding drawings in the written description are provided by way of example only to help the reader understand the principles of this disclosure. They are not intended and should not be construed as limiting the scope of this disclosure in any way. Although certain embodiments and examples have been provided, those skilled in the art will understand based on the disclosure herein that changes can be made to the illustrated embodiments and examples without departing from the scope of this disclosure.

[0079] From the following detailed description, aspects, features, and advantages of this disclosure will become apparent. Several embodiments and implementations are shown for illustrative purposes. This disclosure is also capable of further and different embodiments, and several details thereof may be modified in various obvious ways without departing from the spirit and scope of this disclosure. Therefore, the drawings and description are to be considered illustrative in nature and not restrictive. This disclosure is illustrated in the accompanying figures by way of example rather than limitation.

[0080] Although the following exemplary descriptions and embodiments employ Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA) for illustrative purposes, other encoding / decoding techniques may be used. That is, this disclosure can be extended to other OFDM-based transmission waveforms or multiple access schemes such as filtered OFDM (F-OFDM). Furthermore, the principles of this disclosure also apply to different encoding and modulation methods. Examples include LDPC, QPSK, BPSK, QAM, etc.

[0081] This disclosure covers several components that can be used in combination or together with each other or can operate as independent solutions. Given the large number of terms and jargon used in conveying concepts related to wireless communication, those skilled in the art have developed numerous acronyms to refer to common elements, components, and processes. For the reader's convenience, a non-exhaustive list of exemplary acronyms is provided below. As will be apparent in the following text, many of these acronyms below and in the remainder of the document may have been newly created by the inventors, while others may currently be familiar. For example, certain acronyms (e.g., CLTM, etc.) may have been developed by the inventors and designed to help provide an effective description of unique features within this disclosure. The following is a list of common and unique acronyms.

[0082] abbreviation:

[0083] [Table 1]

[0084]

[0085]

[0086]

[0087] The following documents are incorporated herein by reference in their entirety, as if fully set forth herein: i) 3GPP TS 38.300 v17.5.0; ii) 3GPP TS 38.331 v17.5.0; and iii) 3GPP TS 38.321 v17.5.0.

[0088] 3GPP (3rd Generation Partnership Project) has developed technical specifications and standards to define the new 5G radio access technology, known as 5G NR. Mobility handling is a critical aspect of any mobile communication system that includes 5G systems. For a UE in connected mode, mobility is controlled by the network with the assistance of the UE to maintain optimal connection quality. Based on measurements of radio link quality of the serving cell (or source cell) and neighboring 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. The basic procedures for network-controlled mobility in connected mode were developed in 3GPP Release 15 NR. Furthermore, in Release 16 NR, enhancements to network-controlled mobility in connected mode were introduced to mitigate connection disruptions during handover procedures. Specifically, two enhanced handover mechanisms were developed, called Conditional Handover (CHO) and Dual Active Protocol Stack (DAPS).

[0089] Typically, in a CHO procedure, the UE is allowed to decide whether to perform a handover when certain execution conditions are met. After receiving a CHO configuration, including configurations for multiple candidate cells, in an RRC reconfiguration message, the UE initiates an evaluation of the CHO execution conditions for the candidate cells. If at least one CHO candidate cell meets its corresponding CHO execution condition, the UE separates from the source cell, applies the target cell's configuration, and synchronizes with the target cell. The UE then completes the CHO process by sending an "RRC reconfiguration complete" message to the target cell. After successfully completing the handover procedure, the UE releases the stored CHO configuration.

[0090] More specifically, a CHO is a handover performed by the UE when one or more handover execution conditions are met. The UE begins evaluating the execution conditions upon receiving the CHO configuration and stops evaluating the execution conditions once the handover is performed.

[0091] The following principles apply to CHO. First, CHO configuration includes the configuration of CHO candidate cells generated by the candidate BS (e.g., gNB) and execution conditions generated by the source (or serving) BS. Execution conditions may include one or two trigger conditions (such as CHO events A3 / A5). Only a single RS type is supported, and up to two different trigger quantities (e.g., RSRP and RSRQ, RSRP and SINR) can be configured simultaneously to evaluate the CHO execution conditions for a single candidate cell. Furthermore, the UE performs the HO procedure upon receiving an HO command (i.e., no CHO configuration) before any CHO execution conditions are met, regardless of any previously received CHO configurations. During CHO execution, or more specifically, from the time the UE begins synchronizing with the target cell, the UE does not monitor the source cell. These principles are typically applied to CHO in existing implementations.

[0092] For mobility in connected modes, including regular handovers via CHO, the network initiates the process based on Layer 3 (L3) measurements via higher-layer signaling (e.g., RRC messages). However, this process involves increased latency, signaling overhead, and downtime, which can be a critical issue in some scenarios with frequency switching, such as, but not limited to, when the UE is in high-speed vehicles and in frequency range 2 (FR2) deployments. Therefore, it is necessary to reduce the increased latency, signaling overhead, and downtime during handover. Thus, Layer 1 / L2 triggered mobility (LTM) is needed, where handover can be triggered using L1 / L2 signaling based on L1 physical layer measurements. More specifically, LTM can refer to a mobility mechanism where the UE switches from a source cell (or serving cell) to a target cell via beam switching triggered by L1 / L2 signaling. Beam switching decisions are based on L1 measurements of beams between adjacent cells. Furthermore, cell handover can be triggered by L1 / L2 signaling from the network or by the fulfillment of pre-configured conditional events, such as during conditional LTM (CLTM). CLTM can refer to LTM process, in which execution conditions are evaluated against one or more candidate cells based on L1 measurements, and cell handover is performed only when one or more execution conditions are met.

[0093] To reduce latency and overload during handover, a RACH-free Choh or CLTM is required. In this disclosure, a RACH-free Choh can refer to a handover process in which there is no random access procedure to the target cell during the handover. A RACH-free Choh can be applied to conditional mobility. In this disclosure, conditional mobility can refer to a handover process triggered by meeting pre-configured conditions of a candidate cell, including, but not limited to, Choh, CLTM, Conditional PSCell Addition (CPA), and Conditional PSCell Change (CPC).

[0094] This disclosure provides a RACH-free HO procedure in conditional mobility. A RACH-free HO or RACH-free cell handover can be performed based on the validity of timing advance (TA) information for the initial uplink (UL) transmission to the target cell and the configured uplink (UL) grant. The terms "cell switch" and "handover" are used interchangeably in this disclosure.

[0095] Figure 4 An example procedure 400 for cell handover without RACH conditions according to an embodiment is shown. For purposes of explanation and illustration, example procedure 400 may be performed by a UE. Although one or more operations are described or shown in a specific order, in other embodiments, the operations may be rearranged in a different order, which may include performing multiple operations in at least partially overlapping time periods.

[0096] refer to Figure 4 Procedure 400 can begin in operation 401. In operation 401, the UE receives and stores the configuration for RACH-free conditional cell handover for each candidate cell. Multiple candidate cells may exist for conditional cell handover. The configuration may include, for example, but not limited to, execution conditions to be evaluated for the candidate cells, TA information, and / or UL authorization for the configuration of initial UL transmission to the candidate cells for RACH-free cell handover.

[0097] In Operation 403, the UE evaluates the execution conditions for each candidate cell.

[0098] In operation 405, when the execution conditions of the candidate cell are met or satisfied, the UE selects the candidate cell as the target cell (or applicable cell) and then performs a cell handover to the target cell.

[0099] In operation 407, when performing a cell handover, the UE determines whether a valid TA and valid UL grant for the initial UL transmission to the target cell are available. The initial UL transmission may include an “RRCReconfigurationComplete” message. A valid TA can be determined or obtained in various ways. In an embodiment, if included in the target cell's configuration, the valid TA can be determined based on pre-configured TA information. In an embodiment, if included in the target cell's configuration, the valid TA can be determined based on time-based events, distance-based events, or validity information. In an embodiment, when RACH resources are pre-configured in the target cell's configuration, the valid TA can be obtained through early TA acquisition. This allows the UE to send a PRACH to the target cell before the cell handover. When a TA estimation configuration is provided in the target cell's configuration, the valid TA can be obtained through UE-autonomous estimation. A valid UL grant can also be determined in various ways. In an embodiment, if included in the target cell's configuration, the valid UL grant can be determined based on pre-configured UL grants. In an embodiment, if included in the target cell's configuration, the valid UL grant can be determined based on time-based events or validity information.

[0100] In operation 409, if both a valid TA and a valid UL authorization are available, process 400 proceeds to operation 411. Otherwise, it proceeds to operation 413.

[0101] In operation 411, the UE sends an initial UL transmission (e.g., UL PUSCH) to the target cell by applying a valid TA and a valid UL grant.

[0102] In operation 413, one or both of the valid TA and valid UL grant are unavailable. The UE performs a random access procedure to the target cell or sends a scheduling request (SR) to the target cell. In this embodiment, when the valid TA is unavailable, the UE performs a random access procedure to the target cell. When the valid TA is available but the valid UL grant is unavailable, the UE sends an SR to the target cell.

[0103] Figure 5 An example procedure 500 for signaling a handover without RACH conditions, according to an embodiment, is illustrated. For purposes of explanation and illustration, example procedure 500 may be performed by a UE, a source BS (source cell), and one or more candidate BSs (candidate cells). Although one or more operations are described or illustrated in a specific order, in other embodiments, the operations may be rearranged in a different order, which may include performing multiple operations in at least partially overlapping time periods.

[0104] refer to Figure 5Process 500 can begin in operation 501. In operation 501, the UE sends a measurement report to the source BS. In this embodiment, the source BS may be referred to as the source cell. For example, but not limited to, the UE may report the signal quality (e.g., RSRP) of the source cell and candidate cells.

[0105] In Operation 503, the source BS determines that a RACH-free cell handover is configured and initiates cell preparation for a RACH-free cell handover with one or more candidate cells.

[0106] In Operation 505, the source BS sends an RRCReconfiguration message to the UE, including one or more candidate cell configurations for conditional cell handover. The configuration may include TA information for one or more candidate cells and / or configured UL authorization.

[0107] In Operation 507, the UE stores one or more candidate cell configurations for conditional cell handover. The UE then sends an RRCReconfigurationComplete message to the source BS.

[0108] In Operation 509, the UE begins evaluating the execution conditions of candidate cells for conditional cell handover. The execution conditions of candidate cells may include RRM (Radio Resource Management) measurement events, time-based events, and / or distance-based events.

[0109] In Operation 511, the UE can perform early synchronization. More specifically, in Operation 511a, the UE can perform downlink (DL) synchronization with the candidate cell before cell handover. Additionally, in Operation 511b, if configured by the network, the UE can perform early TA acquisition using the candidate cell before cell handover. Early TA acquisition can be performed through a random access procedure for the candidate cell. The UE needs to maintain the validity of the early acquired TA.

[0110] In operation 513, when at least one candidate cell meets the execution conditions, the UE selects a candidate cell as the target cell. Then, the UE separates from the source cell and applies the stored candidate cell configuration to the selected candidate cell (target cell or target BS).

[0111] In operation 515, the UE determines, for example but not limited to, whether it has a valid TA and / or valid UL authorization for initial UL transmission to the target cell, based on TA information included in the candidate cell configuration and / or configured UL authorization. When both a valid TA and a valid UL authorization are available, procedure 500 proceeds to operation 519. Otherwise, it proceeds to operation 517.

[0112] In operation 517, when the UE does not have a valid TA and / or valid UL authorization for the target cell, the UE performs a random access procedure or scheduling request to the target cell. In this embodiment, when a valid TA is unavailable, the UE performs a random access procedure to the target cell. When a valid TA is available but a valid UL authorization is unavailable, the UE sends an SR to the target cell.

[0113] In Operation 519, when the UE has a valid TA and a valid UL authorization for the target cell, the UE sends an initial UL transmission to the target cell, for example, in the PUSCH. The initial UL transmission may include an RRCReconfigurationComplete message. In Operation 519, the random access procedure is skipped (no RACH cell handover).

[0114] In Operation 521, when the UE has already performed a random access procedure for the target cell, it determines that the cell handover has been successfully completed once the random access is successfully completed. For cell handover without RACH, the UE determines that the cell handover has been successfully completed when it confirms that the network has successfully received the initial UL transmission. The UE can confirm the successful reception of the initial UL transmission by receiving the PDDCH of the C-RNTI addressing the UE in the target cell. The target cell schedules new downlink and / or uplink transmissions after the initial UL transmission.

[0115] The UE may not automatically release candidate cell configurations, but instead maintain them by adding, modifying, and / or releasing them based on network reconfiguration. In some embodiments, operations 509 to 521 may be performed multiple times for subsequent cell handovers using the candidate cell configurations provided in operation 505.

[0116] In some embodiments, the candidate cell configuration in operation 505 includes TA information, which includes TA parameters (N_TA) to be applied to the initial UL transmission (e.g., UL PUSCH) to the selected candidate cell (i.e., the target cell). When the execution conditions of the candidate cell are met in operation 513 and the candidate cell is selected as the target cell, the UE determines that the TA parameters (N_TA) are valid for sending the initial UL transmission to the target cell. The UE may apply the TA parameters (N_TA) to a configured or indicated timing advance group (TAG). In one embodiment, a TAG ID may be associated with the TA parameters (N_TA). In another embodiment, the UE may apply the TA parameters (N_TA) to a TAG with ID 0.

[0117] In some embodiments, the candidate cell configuration in operation 505 includes TA information, which includes TA parameters (N_TA) to be applied to the initial UL transmission (e.g., UL PUSCH) to the target cell. The candidate cell configuration in operation 505 also includes execution conditions for the candidate cell, which include time-based events specifying a time window. The time-based events can be configured to determine the validity of the candidate cell or specifically to determine the validity of the candidate cell's TA information. If the time measured at the UE is within the time window specified in the time-based event, the UE can determine that the time-based event has been triggered or satisfied (i.e., the entry condition has been met). If the measured time at the UE is not within the time window specified in the time-based event, the UE can determine that the time-based event has not been triggered or satisfied (i.e., the departure condition has been met). The measured time may refer to the time when the UE determines that the execution conditions of the candidate cell have been satisfied. When the execution conditions of the candidate cell are satisfied in operation 513 and the candidate cell is selected as the target cell, the UE determines that the TA parameters (N_TA) are valid for sending the initial UL transmission to the target cell. The UE can apply the TA parameter (N_TA) to a configured or indicated TAG. In one implementation, the TAG ID can be associated with the TA parameter (N_TA). In another implementation, the UE can apply the TA parameter (N_TA) to a TAG with ID 0.

[0118] In some embodiments, the candidate cell configuration in operation 505 includes TA information, which includes TA parameters (N_TA) to be applied to the initial UL transmission (e.g., UL PUSCH) to the target cell. The candidate cell configuration in operation 505 also includes execution conditions for the candidate cell, which include distance-based events specifying a reference location and a distance threshold. In one embodiment, if the distance between the real-time measured UE location and the real-time reference location is less than the distance threshold, then the UE can determine that the distance-based event has been triggered or satisfied (i.e., the entry condition is satisfied). If the distance between the real-time measured UE location and the real-time reference location is greater than the distance threshold, then the UE can determine that the distance-based event has not been triggered or satisfied (i.e., the departure condition is satisfied). In another embodiment, if the distance between the real-time measured UE location and the real-time reference location is greater than the distance threshold, then the UE can determine that the distance-based event has been triggered or satisfied (i.e., the entry condition is satisfied). If the distance between the real-time measured UE location and the real-time reference location is less than the distance threshold, then the UE can determine that the distance-based event has not been triggered or satisfied (i.e., the departure condition is satisfied). When the execution conditions for the candidate cell are met in operation 513 and the candidate cell is selected as the target cell, the UE determines that the TA parameter (N_TA) is valid for sending the initial UL transmission to the target cell. The UE can apply the TA parameter (N_TA) to a configured or indicated TAG. In one implementation, the TAG ID can be associated with the TA parameter (N_TA). In another implementation, the UE can apply the TA parameter (N_TA) to a TAG with ID 0.

[0119] In some embodiments, the candidate cell configuration in operation 505 includes TA information, which includes TA parameters (N_TA) to be applied to the initial UL transmission (e.g., UL PUSCH) to the target cell. The candidate cell configuration in operation 505 also includes execution conditions for the candidate cell, which include distance-based events specifying a reference location at a reference time and a distance threshold. In one embodiment, if the distance between the real-time measured UE location and the real-time reference location is less than the distance threshold, then the UE can determine that the distance-based event has been triggered or satisfied (i.e., the entry condition is satisfied). If the distance between the real-time measured UE location and the real-time reference location is greater than the distance threshold, then the UE can determine that the distance-based event has not been triggered or satisfied (i.e., the departure condition is satisfied). In another embodiment, if the distance between the real-time measured UE location and the real-time reference location is greater than the distance threshold, then the UE can determine that the distance-based event has been triggered or satisfied (i.e., the entry condition is satisfied). If the distance between the real-time measured UE location and the real-time reference location is less than the distance threshold, then the UE can determine that the distance-based event has not been triggered or satisfied (i.e., the departure condition is satisfied). The UE can estimate the real-time reference position based on mobility information associated with the reference position of the candidate cell. Mobility information can be provided in the candidate cell configuration in the form of satellite ephemeris parameters, mobility speed parameters, mobility direction parameters, and / or speed parameters. Reference time can be provided in the candidate cell configuration in the form of satellite epoch time, UTC (Coordinated Universal Time), SFN (System Frame Number), subframe, or symbol number. When the execution conditions of the candidate cell are met in operation 513 and the candidate cell is selected as the target cell, the UE determines that the TA parameter (N_TA) is valid for sending the initial UL transmission to the target cell. The UE can apply the TA parameter (N_TA) to a configured or indicated TAG. In one implementation, the TAG ID can be associated with the TA parameter (N_TA). In another implementation, the UE can apply the TA parameter (N_TA) to a TAG with ID 0.

[0120] In some embodiments, the candidate cell configuration in operation 505 includes a UE-autonomous TA estimation configuration, which includes parameters to be applied to the TA estimation at the UE. In one embodiment, a reference TA, validity information, and / or a reference signal for TA estimation are provided in the UE-autonomous TA estimation configuration. In another embodiment, the UE-autonomous TA estimation configuration provides satellite ephemeris, common TA parameters, validity duration of a timer (e.g., T430), and / or epoch time for non-terrestrial network (NTN) candidate cells. If a UE-autonomous TA estimation configuration is provided for a candidate cell, the UE performs TA estimation on the candidate cell based on this configuration and maintains the validity of the estimated TA. For example, the UE maintains the validity of the candidate cell's ephemeris and common TA parameters by running a timer T430 for the NTN candidate cell. The UE can perform TA estimation for the candidate cell by calculating the round-trip time (RTT) between the UE location and the satellite location while the timer (T430) is running. The validity of the estimated TA may depend on the validity of the ephemeris and common TA parameters. If the applied ephemeris and common TA parameters are valid (e.g., as long as the candidate cell's T430 is operational), the UE can determine that the estimated TA is valid. If the candidate cell's T430 expires, the UE can determine that the estimated TA is no longer valid. When the candidate cell's execution conditions are met, in operation 513, the candidate cell is selected as the target cell, and the UE's estimated TA for the candidate cell is valid. The UE determines that the estimated TA is valid for sending the initial UL transmission to the target cell. The UE can apply the estimated TA to a configured or indicated TAG. In one implementation, the TAG ID can be associated with the estimated TA. In another implementation, the UE can apply the estimated TA to a TAG with ID 0.

[0121] In some embodiments, the candidate cell configuration in operation 505 includes an early TA acquisition configuration, which includes a RACH configuration for the candidate cell. If an early TA acquisition configuration is provided for the candidate cell, the UE can acquire the TA of the candidate cell by sending a PRACH to the candidate cell and receiving the candidate cell's TA information from the source cell in a Random Access Response (RAR) or MAC CE (Control Element). The TA information may include a TA value and / or the duration of a TA validity timer. The UE maintains a validity timer for the TA of the candidate cell. If the validity timer is running, the UE determines that the TA is valid. Conversely, if the validity timer expires, the UE determines that the TA is invalid. When the execution conditions of the candidate cell are met, the candidate cell is selected as the target cell in operation 513, and the early acquired TA of the candidate cell is valid. The UE determines that the TA is valid for sending the initial UL transmission to the target cell. The UE may apply the early acquired TA to a configured or indicated TAG. In one embodiment, a TAG ID may be associated with the early acquired TA. In another embodiment, the UE may apply the early acquired TA to a TAG with ID 0.

[0122] In some embodiments, the candidate cell configuration in operation 505 includes authorizations (i.e., UL authorizations) for one or more configurations. Each configuration authorization (CG) includes periodic CG timings for PUSCH transmissions. Each CG may be associated with a corresponding one of one or more SSBs, CSI-RSs, or TRS, for example, in a manner where the CG timing is mapped to an SSB, CSI-RS, or TRS. RSRP thresholds can be configured for beam selection and CG timing selection. When the candidate cell execution conditions are met, and the candidate cell is selected as the target cell in operation 505, and at least one of the SSBs, CSI-RSs, or TRS associated with the CG has an RSRP exceeding the RSRP threshold, the UE determines that the CG is valid for an initial UL transmission to the target cell. The UE selects an SSB, CSI-RS, or TRS associated with the CG having an RSRP higher than the RSRP threshold. The UE then transmits the initial UL transmission (UL PUSCH) at the PUSCH timing corresponding to the selected SSB, CSI-RS, or TRS.

[0123] In some embodiments, the candidate cell configuration in operation 505 includes authorizations (i.e., UL authorizations) for one or more configurations. Each configuration authorization (CG) includes periodic CG timings for PUSCH transmissions. Each CG may be associated with a corresponding one of one or more SSBs, CSI-RSs, or TRS, for example, in a manner where the CG timing is mapped to an SSB, CSI-RS, or TRS. RSRP thresholds may be configured for beam selection and CG timing selection. The candidate cell configuration in operation 505 also includes execution conditions for the candidate cell, which include time-based events specifying a time window. The time-based events may be configured for the validity of the candidate cell or specifically for the validity of the CGs of the candidate cell. If the measurement time at the UE is within the time window specified in the time-based event, the UE determines that the time-based event has been triggered or satisfied (i.e., the entry condition has been satisfied). If the measurement time at the UE is not within the time window specified in the time-based event, the UE may determine that the time-based event has not been triggered or satisfied (i.e., the departure condition has been satisfied). The measurement time may refer to the time at which the UE determines that the execution conditions of the candidate cell have been satisfied. When the execution conditions of the candidate cell are met, and in operation 505 the candidate cell is selected as the target cell, and at least one of the SSB, CSI-RS, or TRS associated with the CG has an RSRP exceeding the RSRP threshold, the UE determines that the CG is valid for the initial UL transmission to the target cell. The UE selects the SSB, CSI-RS, or TRS associated with the CG that has an RSRP higher than the RSRP threshold. Then, the UE transmits the initial PUSCH at the PUSCH timing corresponding to the selected SSB, CSI-RS, or TRS.

[0124] In some embodiments, the candidate cell configuration in operation 505 includes one or more CGs. Each CG includes a periodic CG timing for PUSH transmission. Each CG may be associated with a corresponding one of one or more SSBs, CSI-RS, or TRS, for example, in a manner where CG timings are mapped to SSBs, CSI-RS, or TRS. The candidate cell configuration in operation 505 also includes execution conditions for the candidate cell, which include beam / L1 measurement events. If the measurement of the configured beam satisfies the pre-configured conditions, the UE determines that the beam / L1 measurement event has been triggered or satisfied. If the execution conditions of the candidate cell are satisfied, the candidate cell is selected as the target cell in operation 513, and at least one of the SSBs, CSI-RS, or TRS that satisfies the beam / L1 measurement event is associated with the CG, the UE determines that the CG is valid for the initial UL transmission to the target cell. The UE selects the beam, SSB, CSI-RS, or TRS that satisfies the beam / L1 measurement event and is associated with the CG. Then, the UE sends an initial PUSCH at the PUSCH timing corresponding to the selected beam, SSB, CSI-RS, or TRS. In the presence of multiple beams, SSBs, CSI-RS, or TRS that satisfy a beam / L1 measurement event, in an embodiment, the UE can select the optimal beam, SSB, CSI-RS, or TRS from among the multiple beams, SSBs, CSI-RS, and TRS. For example, but not limited to, the optimal beam, SSB, CSI-RS, or TRS can be associated with an L1 measurement quantity. In another embodiment, a threshold (e.g., an L1-RSRP threshold) can be configured for beam selection, such that the UE selects a beam, SSB, CSI-RS, or TRS exceeding the threshold from among the multiple beams, SSBs, CSI-RS, and TRS. In another embodiment, the UE can select a beam, SSB, CSI-RS, or TRS from among the multiple beams, SSBs, CSI-RS, and TRS that satisfy a beam / L1 measurement event based on the UE implementation.

[0125] In some embodiments, the candidate cell configuration in operation 505 includes one or more CGs. Each CG includes periodic CG timings for PUSCH transmissions. Each CG may be associated with a corresponding one of one or more SSBs, CSI-RS, or TRS, for example, in a manner where CG timings are mapped to SSBs, CSI-RS, or TRS. The candidate cell configuration in operation 505 also includes execution conditions for the candidate cell, which include time-based events specifying time windows. The time-based events may be configured for the validity of the candidate cell or specifically configured for the validity of the CGs of the candidate cell. If the measurement time at the UE is within the time window specified in the time-based event, the UE determines that the time-based event has been triggered or satisfied (i.e., the entry condition has been satisfied). If the measurement time at the UE is not within the time window specified in the time-based event, the UE may determine that the time-based event has not been triggered or satisfied (i.e., the departure condition has been satisfied). The measurement time may refer to the time when the UE determines that the execution conditions of the candidate cell have been satisfied. The candidate cell configuration in operation 505 also includes beam / L1 measurement events. If the measurements of the configured beam meet pre-configured conditions, the UE determines that a beam / L1 measurement event has been triggered or satisfied. If the execution conditions of the candidate cell are met, the candidate cell is selected as the target cell in operation 513, and at least one of the SSB, CSI-RS, or TRS that satisfies the beam / L1 measurement is associated with the CG. The UE determines that the CG is valid for the initial UL transmission to the target cell. The UE selects the beam, SSB, CSI-RS, or TRS that satisfies the beam / L1 measurement event and is associated with the CG. Then, the UE sends the initial PUSCH at the PUSCH timing corresponding to the selected SSB, CSI-RS, or TRS. In the case where multiple beams, SSBs, CSI-RS, or TRS satisfy the beam / L1 measurement event, in the embodiment, the UE can select the best beam, SSB, CSI-RS, or TRS from multiple beams, SSBs, CSI-RS, and TRS. For example, but not limited to, the best beam, SSB, CSI-RS, or TRS can be associated with an L1 measurement. In another embodiment, a threshold (e.g., an L1-RSRP threshold) can be configured for beam selection, allowing the UE to select a beam, SSB, CSI-RS, or TRS that exceeds the threshold from a plurality of beams, SSBs, CSI-RS, and TRS. In another embodiment, the UE can select a beam, SSB, CSI-RS, or TRS from a plurality of beams, SSBs, CSI-RS, and TRS that satisfy a beam / L1 measurement event, based on the UE implementation.

[0126] In some embodiments, the candidate cell configuration in operation 505 includes one or more CGs. Each CG includes a periodic CG timing for PUSCH transmission. Each CG may be associated with a corresponding one of one or more SSBs, CSI-RS, or TRS, for example, in a manner where CG timing is mapped to an SSB, CSI-RS, or TRS. An RSRP threshold may be configured for beam and CG timing selection. Each CG may be configured for an effective duration. The effective duration may be indicated by a start time and / or a duration. The start time may be signaled in the form of UTC time, SFN, subframe, or symbol number. When the candidate cell execution conditions are met, in operation 513, a candidate cell is selected as the target cell, at least one of the SSBs, CSI-RS, or TRS associated with the CG has an RSRP exceeding the RSRP threshold, and the time measured at the UE is within the effective duration of the CG. The UE determines that the CG is valid for the initial UL transmission to the target cell. The UE selects the SSB, CSI-RS, or TRS associated with the CG having an RSRP higher than the RSRP threshold. Then, the UE sends the initial PUSCH at the PUSCH timing corresponding to the selected SSB, CSI-RS, or TRS.

[0127] In some embodiments, the candidate cell configuration in operation 505 includes one or more CGs. Each CG includes a periodic CG timing for PUSCH transmission. Each CG may be associated with a corresponding one of one or more SSBs, CSI-RS, or TRS in such a way that the CG timing is mapped to an SSB, CSI-RS, or TRS. Each CG may be configured for an effective duration. The effective duration may be indicated by a start time and / or a duration. The start time may be signaled in the form of UTC time, SFN, subframe, or symbol number. The candidate cell configuration in operation 505 also includes beam / L1 measurement events. If the measurement of the configured beam satisfies the configured conditions, then the UE determines that a beam / L1 measurement event is triggered or satisfied. If the execution conditions of the candidate cell are satisfied, the candidate cell is selected as the target cell in operation 513, and at least one of the SSBs, CSI-RS, or TRS that satisfies the beam / L1 measurement is associated with a CG, and the measurement time at the UE is within the effective duration of the CG, the UE determines that the CG is valid for the initial UL transmission to the target cell. The UE selects the beam, SSB, CSI-RS, or TRS that satisfies the beam / L1 measurement event and is associated with the CG. The UE then sends an initial PUSCH at the PUSCH timing corresponding to the selected beam, SSB, CSI-RS, or TRS. In the presence of multiple beams, SSBs, CSI-RS, or TRS that satisfy the beam / L1 measurement event, in one embodiment, the UE can select the optimal beam, SSB, CSI-RS, or TRS from among the multiple beams, SSBs, CSI-RS, and TRS. The optimal beam, SSB, CSI-RS, or TRS can be associated with an L1 measurement. In another embodiment, a threshold (e.g., an L1-RSRP threshold) can be configured for beam selection, such that the UE selects a beam, SSB, CSI-RS, or TRS exceeding the threshold from among the multiple beams / SSBs / CSI-RS / TRS. In another embodiment, the UE can select a beam, SSB, CSI-RS, and TRS from multiple beams, SSBs, CSI-RS, and TRS that satisfy the beam / L1 measurement event based on the UE implementation.

[0128] In some embodiments, the candidate cell configuration in operation 505 may include one or more pairs of TA information and configured UL authorization. Each pair may be associated with a specific time window. The UE evaluates the conditions of the candidate cell for conditional cell handover. When the conditions for conditional cell handover are met and the measurement time (e.g., the time when the conditions are met) is within the specific time window, the UE identifies the pair of TA information and UL authorization associated with the specific time window and determines that the TA information and UL authorization are valid. When an initial UL transmission is sent to the candidate cell, the UE performs a conditional cell handover to the candidate cell in a RACH-free process using the TA information and UL authorization.

[0129] One or more of the above embodiments can be used individually or in combination to determine the valid TA and valid UL grant for the initial UL transfer to the target cell. If the valid TA is unavailable, the valid UL grant is unavailable, or both the valid TA and valid UL grant are unavailable, then in operation 517, the UE performs a random access procedure to the target cell. If the valid TA is available but no valid UL grant is available, then the UE can trigger a scheduling request (SR) in operation 509.

[0130] In some embodiments, the conditions for determining a valid TA and the conditions for determining a valid UL grant can be applied simultaneously in an additive manner to determine a RACH-free cell handover in conditional mobility. For example, if the UE has a valid TA and a valid UL grant for the target cell, the UE performs a RACH-free cell handover to the target cell using the valid TA and valid CG. However, if the UE has a valid TA but no valid UL grant for the target cell, the UE can use the valid TA to perform a SR. If the UE has neither a valid TA nor a valid CG for the target cell, the UE performs a random access procedure to the target cell when performing a cell handover. When the UE performs an SR, if the Buffer State Report (BSR) procedure determines that at least one BSR has been triggered and not canceled, and if a regular BSR has been triggered and a timer (e.g., logicalChannelSR-DelayTimer) is not running, and if no UL-SCH resources are available for the new transmission, then if an SR configuration including PUCCH resources is provided, the UE triggers an SR to the target cell. In another embodiment, an SR configuration including PUCCH resources for the initial UL transmission for a RACH-free cell handover can be provided in the candidate cell configuration. If the UE has a valid TA but no valid UL authorization for the target cell, the UE can use SR configuration to trigger an SR for the target cell.

[0131] Unless otherwise specified, references to elements in the singular form are not intended to indicate one and only one, but rather one or more. For example, a module can refer to one or more modules. In the absence of further constraints, elements preceded by "a," "the," or "said" do not preclude the presence of additional identical elements.

[0132] Titles and subtitles (if any) are used for convenience only and do not limit this disclosure. Words used exemplarily are used to indicate that they are intended as examples or illustrations. Within the scope of the use of terms such as “include,” “have,” etc., such terms are intended to be inclusive, similar to how the term “comprise” is interpreted when used as a transition word in the claims. Relational terms such as “first” and “second” may be used to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between these entities or actions.

[0133] Phrases such as aspect, that aspect, on the other hand, some aspects, one or more aspects, implementation, that implementation, another implementation, some implementations, one or more implementations, embodiment, that embodiment, another embodiment, some embodiments, one or more embodiments, configuration, that configuration, another configuration, some configurations, one or more configurations, subject matter, disclosure, this disclosure, other variations thereof, etc., are used for convenience and do not imply that disclosures associated with such phrases are essential to the subject matter, or that such disclosures apply to all configurations of the subject matter. Disclosures associated with such phrases may apply to all configurations or one or more configurations. Disclosures associated with such phrases may provide one or more examples. Phrases such as aspect or some aspects may refer to one or more aspects, and this similarly applies to other foregoing phrases.

[0134] The phrase "at least one of..." following a list of items, using the terms "and" or "or" to separate any items, modifies the list as a whole, rather than each member of the list. The phrase "at least one of..." does not require the selection of at least one item; rather, it allows for the inclusion of at least one of any one item, and / or at least one of any combination of items, and / or the meaning of at least one of each item. For example, each of the phrases "at least one of A, B, and C" or "at least one of A, B, or C" refers to only A, only B, or only C; any combination of A, B, and C; and / or at least one of each of A, B, and C.

[0135] It should be understood that the specific order or hierarchy of the disclosed steps, operations, or processes is an illustration of exemplary methods. Unless otherwise explicitly stated, it should be understood that the specific order or hierarchy of steps, operations, or processes may be performed in a different order. Some steps, operations, or processes may be performed simultaneously, or may be performed as part of one or more other steps, operations, or processes. The appended method claims (if any) present elements of various steps, operations, or processes in a sample order, but this does not imply limitation to the specific order or hierarchy presented. These may be performed serially, linearly, in parallel, or in a different order. It should be understood that the described instructions, operations, and systems can generally be integrated together in a single software / hardware product or packaged into multiple software / hardware products.

[0136] This disclosure is provided to enable any person skilled in the art to practice the various aspects described herein. In some cases, well-known structures and components are shown in block diagram form to avoid obscuring the concept of the subject matter. This disclosure provides numerous examples of the subject matter, and the subject matter is not limited to these examples. Various modifications to these aspects will be apparent to those skilled in the art, and the principles described herein can be applied to other aspects.

[0137] All structural and functional equivalents of the various aspects described herein, whether now or hereafter known to a person skilled in the art, are expressly incorporated herein by reference and are intended to be covered by the claims. Furthermore, nothing disclosed herein is intended to be made public, whether or not such disclosure is explicitly stated in the claims. Pursuant to 35 USC §112, paragraph 6, no claim element may be interpreted unless it is explicitly stated using the phrase “for a component of” or, in the case of a method claim, using the phrase “for a step of”.

[0138] The title, background art, description of the drawings, abstract, and figures are incorporated herein by reference and are provided as illustrative examples rather than as limiting descriptions. It should be understood at the time of filing that they are not intended to limit the scope or meaning of the claims. Furthermore, the detailed description provides illustrative examples, and various features are combined in various embodiments for the purpose of simplifying this disclosure. The approach of this disclosure should not be construed as reflecting an intention to require more features than expressly recited in each claim. Rather, as reflected in the following claims, the inventive subject matter lies in all features of fewer than those in a single disclosure configuration or operation. The appended claims are incorporated herein by reference, wherein each claim is independently claimed as a separate subject matter.

[0139] The claims are not intended to be limited to the aspects described herein, but rather to conform to the full scope consistent with the language claims and to include all legal equivalents. Nevertheless, no claim is intended to include subject matter that does not meet the requirements of applicable patent law, nor should they be interpreted in this manner.

Claims

1. A user equipment (UE) in a wireless network, the UE comprising: transceiver; and At least one processor, operatively coupled to the transceiver, is configured to: Receive from source cell a conditional cell handover configuration including one or more execution conditions for one or more candidate cells, wherein each of the one or more execution conditions is associated with a conditional cell handover to the corresponding candidate cell; Determine whether the one or more execution conditions are met; Based on the fact that the execution conditions for the candidate cell are met, the candidate cell is selected as the target cell for conditional cell handover. Determine whether a valid timing advance (TA) and a valid UL grant are available for the initial uplink (UL) transmission to the target cell; and Based on the determination that a valid TA and a valid UL authorization are available, an initial UL transmission is sent to the target cell using the valid TA and valid UL authorization.

2. The UE according to claim 1, wherein, The at least one processor is further configured to: Based on the determination that a valid access date (TA) is unavailable, a random access procedure is performed on the target cell; and Based on the determination that a valid UL authorization is unavailable, a scheduling request is sent to the target cell.

3. The UE according to claim 1, wherein, Conditional cell handover configuration includes at least one of TA information for initial UL transmission to the target cell and a configured UL authorization; The at least one processor is configured to determine at least one of the following: The TA information is valid if the time or distance conditions included in the conditional cell handover configuration are met. The configured UL authorization is valid based on the fact that the time conditions included in the conditional cell handover configuration are met; and The pair of TA information and configured UL authorization is valid based on the fact that the time conditions associated with the pair of TA information and UL authorization are met.

4. The UE according to claim 1, wherein: Conditional cell handover configuration includes one or more UL grants for each candidate cell, each of the one or more UL grants being associated with a corresponding beam from one or more beams; and The at least one processor is further configured to: Based on the execution conditions of the candidate cells, a beam is selected from one or more beams; and It is determined that the UL authorization for the configuration associated with the selected beam is valid.

5. The UE according to claim 1, wherein, The at least one processor is further configured to: TA estimation for the target cell is performed based on UE location, satellite ephemeris, and public TA information; as well as Based on the fact that the public TA information and satellite ephemeris provided in the conditional cell handover configuration are valid, it is determined that the estimated TA is valid.

6. A method performed by a user equipment (UE) in a wireless network, the method comprising: Receive from source cell a conditional cell handover configuration including one or more execution conditions for one or more candidate cells, wherein each of the one or more execution conditions is associated with a conditional cell handover to the corresponding candidate cell; Determine whether the one or more execution conditions are met; Based on the fact that the execution conditions for the candidate cell are met, the candidate cell is selected as the target cell for conditional cell handover. Determine whether a valid timing advance (TA) and a valid UL grant are available for the initial uplink (UL) transmission to the target cell; and Based on the determination that a valid TA and a valid UL authorization are available, an initial UL transmission is sent to the target cell using the valid TA and valid UL authorization.

7. The method according to claim 6, further comprising: Based on the determination that a valid TA is unavailable, a random access procedure is performed on the target cell; as well as Based on the determination that a valid UL authorization is unavailable, a scheduling request is sent to the target cell.

8. The method according to claim 6, wherein, Conditional cell handover configuration includes at least one of TA information for initial UL transmission to the target cell and a configured UL authorization; and Determining whether a valid TA and a valid UL authorization are available includes at least one of the following: Based on the determination that the time or distance conditions included in the conditional cell handover configuration are met, it is determined that the TA information is valid; Based on the determination that the time conditions included in the conditional cell handover configuration are met, it is determined that the configured UL authorization is valid; and The pair of TA information and configured UL authorization is determined to be valid based on the fact that the time conditions associated with the pair of TA information and UL authorization are met.

9. The method according to claim 6, wherein, Conditional cell handover configuration includes one or more configurations of UL authorization for each candidate cell, wherein each of the one or more configurations of UL authorization is associated with a corresponding beam in one or more beams; as well as Also includes: Based on the execution conditions of the candidate cells, a beam is selected from one or more beams; as well as It is determined that the UL authorization for the configuration associated with the selected beam is valid.

10. The method of claim 6, further comprising: TA estimation for the target cell is performed based on UE location, satellite ephemeris, and public TA information; as well as Based on the fact that the public TA information and satellite ephemeris provided in the conditional cell handover configuration are valid, it is determined that the estimated TA is valid.

11. A base station (BS) in a wireless network, the BS comprising: transceiver; and At least one processor, operatively coupled to the transceiver, is configured to: Receive measurement reports from user equipment (UE); Based on the measurement report, determine the readiness conditions for cell handover; Generate a conditional cell handover configuration that includes one or more execution conditions for one or more candidate cells, wherein each of the one or more execution conditions is associated with a conditional cell handover to the corresponding candidate cell; as well as Send conditional configuration to the UE.

12. The BS according to claim 11, wherein, The conditional cell handover configuration includes at least one of timing advance (TA) information for the initial uplink (UL) transmission to each of the one or more candidate cells and a configured UL authorization.

13. A method performed by a base station (BS) in a wireless network, the BS comprising: Receive measurement reports from user equipment (UE); Based on the measurement report, determine the readiness conditions for cell handover; Generate a conditional cell handover configuration that includes one or more execution conditions for one or more candidate cells, wherein each of the one or more execution conditions is associated with a conditional cell handover to the corresponding candidate cell; as well as Send conditional configuration to the UE.

14. The method according to claim 13, wherein, The conditional cell handover configuration includes at least one of timing advance (TA) information for the initial uplink (UL) transmission to each of the one or more candidate cells and a configured UL authorization.

15. The method according to claim 13, in, Conditional cell handover configuration includes one or more UL authorizations for each candidate cell, each of the one or more UL authorizations being associated with a corresponding beam in one or more beams.

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