Wireless communication method and user equipment

Abstract

The present application provides a wireless communication method and a user equipment, which can reduce the interruption time of handover. In one embodiment, the present application provides a wireless communication method, which can include: a user equipment receiving a configuration in a serving cell of a mobile communication network, wherein the configuration comprises information for performing a random access channel (RACH) procedure on a neighboring cell, the neighboring cell belonging to an active cell configured by the mobile communication network; performing the RACH procedure on the neighboring cell, wherein the user equipment acquires a timing advance (TA) of the neighboring cell; receiving a handover command from the mobile communication network for switching from the serving cell to the neighboring cell, wherein the user equipment acquires the TA of the neighboring cell before receiving the handover command; and completing the handover to the neighboring cell without performing an additional RACH procedure after receiving the handover command.

Description

Technical Field

[0001] This invention relates to wireless communication, and more specifically, to a method for obtaining timing advance of neighboring cells in a 5G New Radio (NR) cellular communication network. Background Technology

[0002] Wireless communication networks have grown exponentially over the years. Long-Term Evolution (LTE) systems offer high peak data rates, low latency, improved system capacity, and low operating costs due to a simplified network architecture. LTE systems, also known as 4G systems, also provide seamless integration with older wireless networks such as GSM, CDMA, and the Universal Mobile Telecommunication System (UMTS). In LTE systems, the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) comprises multiple evolved Node-Bs (eNodeBs or eNBs) that communicate with multiple mobile stations known as User Equipment (UEs). 3GPP networks typically include a hybrid of 2G / 3G / 4G systems. The Next Generation Mobile Network (NGMN) committee has decided to focus future NGMN activities on defining end-to-end requirements for 5G New Radio (NR) systems. In 5G NR, base stations are also called gNodeBs or gNBs.

[0003] 5G NR frequency bands are divided into two distinct frequency ranges. Frequency range 1 (FR1) includes sub-6GHz bands, some of which were used in previous standards but have been expanded to cover potentially new spectrum from 410MHz to 7125MHz. Frequency range 2 (FR2) includes bands from 24.25GHz to 52.6GHz. Compared to the bands in FR1, the band range in FR2 within the millimeter wave range is shorter but offers greater available bandwidth. For UEs in RRC connected mode mobility, cell selection is the process by which the UE selects a specific cell for initial registration after power-on, and cell reselection is the mechanism by which the UE changes cells after camping on a cell and entering connected mode. For UEs in RRC connected mode mobility, handover is the process by which the UE switches an ongoing session from the source gNB to a neighboring target gNB.

[0004] During handover for UE reconfiguration and synchronization, data may be interrupted. Random access (RA) is typically required during handover because one of its purposes is to allow the UE to obtain timing advance (TA) of the target cell. RA timing occurs periodically, with some indeterminate delay before the UE can send the preamble. The Random Access Response (RAR) also carries some delay (within a window). For Contention-Based Random Access (CBRA), failure to resolve the contention results in further delays. In LTE, RACH-less handover is possible, but it is only suitable for limited use cases where TA is 0 or the source TA can be reused by the target TA.

[0005] A method is needed to reduce data interruptions caused by random access during handover. Summary of the Invention

[0006] This invention provides a wireless communication method and user equipment that can reduce handover interruption time.

[0007] In one embodiment, a wireless communication method provided by the present invention may include: a user equipment receiving a configuration in a serving cell of a mobile communication network, wherein the configuration includes information on performing a random access channel (RACH) procedure on a neighboring cell, the neighboring cell being an active cell configured by the mobile communication network; performing the RACH procedure on the neighboring cell, wherein the user equipment obtains the timing advance (TA) of the neighboring cell; receiving a handover command from the mobile communication network to the neighboring cell, wherein the user equipment obtains the TA of the neighboring cell before receiving the handover command; and after receiving the handover command, completing the handover to the neighboring cell without performing an additional RACH procedure.

[0008] In another embodiment, the present invention provides a user equipment that may include: a receiver for receiving configuration in a serving cell of a mobile communication network, wherein the configuration includes information for performing a random access channel (RACH) procedure on a neighboring cell, the neighboring cell being an active cell configured by the mobile communication network; a RACH processing circuit for performing the RACH procedure on the neighboring cell, wherein the user equipment obtains the timing advance (TA) of the neighboring cell; and a handover processing circuit for receiving a handover command from the mobile communication network for handover from the serving cell to the neighboring cell, wherein the user equipment obtains the TA of the neighboring cell before receiving the handover command; wherein after the handover processing circuit receives the handover command, the user equipment completes the handover to the neighboring cell without performing an additional RACH procedure.

[0009] As described above, in the embodiments of the present invention, the user equipment obtains the timing advance of the neighboring cell before receiving the handover command and completes the handover to the neighboring cell without performing an additional RACH process after receiving the handover command, thereby reducing the handover interruption time. Attached Figure Description

[0010] Figure 1 An exemplary 5G New Radio (NR) network 100 is shown in accordance with some aspects of the present invention.

[0011] Figure 2 A simplified block diagram of a wireless device (e.g., UE 201 and gNB 211) in a 5G NR network 200 is shown according to some embodiments of the present invention.

[0012] Figure 3 An example is shown of performing an early RACH procedure to reduce latency and interruptions in inter-cell UE mobility.

[0013] Figure 4 Examples of using CFRA to perform RACH to neighboring cells are shown according to some embodiments of the present invention.

[0014] Figure 5 Examples of using CBRA to perform RACH to neighboring cells are shown according to some embodiments of the present invention.

[0015] Figure 6 This is a flowchart of a method for early RACH process and TA acquisition for neighboring cells according to a novel aspect of the present invention. Detailed Implementation

[0016] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." "Substantially" or "approximately" means that, within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect. Furthermore, the terms "coupled" or "coupled" herein include any direct and indirect electrical connection means. Therefore, if a first device is described as coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connection means.

[0017] The following description is for illustrative purposes only and should not be construed as limiting. The scope of the invention is best determined by referring to the appended claims.

[0018] Figure 1 According to some aspects of the present invention, an exemplary 5G New Radio (NR) network 100 is illustrated. The 5G NR network 100 supports active cell set (i.e., active set) configuration and early RACH (e.g., pre-RACH) processes to reduce latency and disruptions in inter-cell mobility. The 5G NR network 100 includes a user equipment (UE) 101 and multiple base stations (including gNB 102, gNB 103, and gNB 104). UE 101 is communicatively connected to serving gNB 102, which provides radio access using Radio Access Technology (RAT) technology (e.g., 5G NR technology). UE 101 may be a smartphone, wearable device, Internet of Things (IoT) device, tablet computer, etc. Alternatively, UE 101 may be a notebook computer (NB) or personal calculator (PC) with a data card containing a modem and radio frequency transceiver to provide wireless communication capabilities inserted or installed.

[0019] The 5G core function receives all connection and session-related information and is responsible for connection and mobility management tasks. For UEs in Radio Resource Control (RRC) connected mode mobility, cell selection is the process by which the UE selects a specific cell for initial registration after power-on, while cell reselection is the mechanism by which the UE changes cells after camping on a cell and entering connected mode. For UEs in RRC connected mode mobility, handover is the process by which the UE switches an ongoing session from the source gNB to a neighboring target gNB. Due to mobility latency (due to time spent on measurement reporting, handover commands, and handover execution), UE 101 is not always served by the best cell / beam. Data may be interrupted during handover for UE reconfiguration and synchronization. In cases of short cell / beam dwell times (e.g., in FR2), the percentage of time the UE is served by a poor cell / beam or experiences service interruptions may be significant.

[0020] Data may be interrupted during handover for UE reconfiguration and synchronization. Random access (RA) is typically required during handover because one of its purposes is to allow the UE to obtain timing advance (TA) of the target cell. RA timing occurs periodically, with some indeterminate delay before the UE can send the preamble. The Random Access Response (RAR) also carries some delay (within a window). For Contention-Based Random Access (CBRA), failure to resolve the contention results in further delay. In LTE, RACH-less handover is possible, but it is only suitable for limited use cases where TA is 0 or the source TA can be reused by the target TA.

[0021] According to a novel aspect of the invention, a method is provided for obtaining timing advances for neighboring cells to reduce delays in inter-cell mobility. In dense deployments, UE 101 is configured to have a set of configured cells and a set of active cells. For configuration set 110 (e.g., Figure 1 The area illustrated by the large dashed box indicates that a configuration cell (i.e., the cell handling UE context) has been prepared, and the UE processes and maintains the configuration of the corresponding cell. For active set 120 (e.g., Figure 1(As illustrated in the three small dashed boxes), UE 101 can perform fast handover between active cells. A non-serving active cell in the active set may become the target cell for handover, and UE 101 can switch to the target cell in the active set via low-latency network handover signaling (L1 or MAC signaling). As shown in box 130, to reduce handover interruptions, UE 101 acquires and maintains the timing advance for the corresponding cells in the active set. UE 101 performs an early RACH for the potential target cell and acquires the TA. Once UE 101 acquires a handover command indicating one of the active cells as the target cell, UE 101 no longer needs to perform RACH, thus reducing handover interruption time.

[0022] Figure 2 Simplified block diagrams of wireless devices (e.g., UE 201 and gNB 211) in a 5G NR network 200 are shown according to some embodiments of the present invention. gNB 211 includes an antenna 215 for transmitting and receiving radio signals. A radio frequency (RF) transceiver 214, coupled to the antenna 215, is used to receive RF signals from the antenna 215 and convert the received signals into baseband signals for transmission to a processor 213. The RF transceiver 214 is also used to convert baseband signals received from the processor 213 into RF signals and transmit the converted RF signals back to the antenna 215. The processor 213 processes the received baseband signals and invokes different functional modules to perform functions in gNB 211. A memory 212 stores program instructions and data 220 to control the operation of gNB 211. Figure 2 In the example, gNB 211 also includes a protocol stack 280 and a set of control function modules and circuits 290. Protocol stack 280 may include a Non-Access-Stratum (NAS) layer for communicating with AMF / SMF / MME entities connected to the core network, a Radio Resource Control (RRC) layer for higher-layer configuration and control, a Packet Data Convergence Protocol / Radio Link Control (PDCP / RLC) layer, a Media Access Control (MAC) layer, and a Physical (PHY) layer. In one example, control function modules and circuits 290 include configuration circuitry 291 for configuring measurement reports and activation sets for the UE, and handover processing circuitry 292 for sending cell handover decisions to the UE.

[0023] Similarly, UE 201 includes memory 202, processor 203, and RF transceiver 204. RF transceiver 204 is coupled to antenna 205, receives RF signals from antenna 205, converts them into baseband signals, and sends them to processor 203. RF transceiver 204 also converts received baseband signals from processor 203 into RF signals and sends them to antenna 205. Processor 203 processes the received baseband signals (e.g., including cell add / activation commands) and invokes different functional modules and circuits to execute features in UE 201. Memory 202 stores data and program instructions 210 to be executed by processor 203 to control the operation of UE 201. As examples, suitable processors include special-purpose processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors associated with a DSP core, controllers, microcontrollers, application-specific integrated circuits (ASICs), file-programmable gate arrays (FPGAs), and other types of integrated circuits (ICs) and / or state machines. Software-associated processors can be used to implement and configure the features of UE201.

[0024] UE 201 also includes a protocol stack 260 and a set of control function modules and circuits 270. Protocol stack 260 may include a NAS layer for communicating with AMF / SMF / MME entities connected to the core network, an RRC layer for higher-level configuration and control, a PDCP / RLC layer, a MAC layer, and a PHY layer. Control function modules and circuits 270 may be implemented and configured through software, firmware, hardware, and / or combinations thereof. When executed by processor 203 via program instructions contained in memory 202, control function modules and circuits 270 cooperate to allow UE 201 to perform embodiments, functional tasks, and features within the network. In one embodiment, control function modules and circuits 270 include configuration circuitry 271 for acquiring configuration information for the active set and pre-RACH, measurement circuitry 272 for performing measurements and reporting measurements, and synchronization / random access / handover processing circuitry 273 for performing pre-synchronization, pre-RACH, and handover procedures based on configuration and handover (HO) commands received from the network.

[0025] Figure 3An embodiment is illustrated for performing an early RACH procedure to reduce latency and interruptions in inter-cell UE mobility. In step 311, UE 301 performs data transmission and reception with the serving base station (i.e., serving gNB or source gNB) in the serving cell (i.e., source cell). In step 312, UE 301 performs neighboring cell measurements and sends a measurement report to the serving gNB. In step 313, the source gNB sends a preparation request to one or more target base stations (i.e., target gNBs). In step 314, the target gNB (located in the target cell) sends a preparation acknowledgement to the source gNB. In step 321, the source gNB may provide UE 301 with RRC configuration / PDCCH commands for the activation set (including the active cell) and the early RACH (e.g., pre-RACH) procedure. The RRC configuration includes information for the UE to perform DL and UL synchronization on the active cell, as well as public and private configurations required when the active cell becomes the UE's serving cell.

[0026] In step 322, UE 301 performs a synchronization and pre-RACH procedure to obtain the TA of neighboring cells. In the downlink, UE 301 performs fine time-frequency tracking for at least a portion of the beams of the active cell. In the uplink, UE 301 performs pre-RACH to obtain the timing advance of the active cell. In a first alternative, the UE performs RACH by receiving RRC configuration, for example, when a neighboring cell is added to the active set. In a second alternative, the UE performs RACH by receiving PDCCH commands; for example, the network may first add a cell to the active set using RRC configuration, and then trigger RACH using PDCCH commands. The DL receive timing reference used to transmit PRACH (Physical RACH) (i.e., transmit the preamble) can be based on the serving cell or on neighboring cells. RACH can be Contention-Free Random Access (CFRA). RRC configuration or PDCCH commands can provide the UE with configurations for performing CFRA (such as SSB (Synchronization Signal and PBCH block) index and preamble index). RACH can be contention-based random access (CBRA). After RACH, UE301 obtains TA for the active cell, but does not immediately change the serving cell.

[0027] In step 331, UE 301 performs neighboring cell measurements and sends the measurement report to the serving gNB. In step 332, the serving gNB makes a cell handover decision based on the measurement report. In step 341, the serving gNB sends a HO (Handover) command message to UE 301. Based on the received HO command, UE 301 implements target cell configuration. The HO command can be L1 / L2 / L3 signaling. In step 342, UE 301 sends an HO completion message to the target gNB, and the handover process is completed. In step 351, UE 301 begins data transmission and reception in the target cell. Because the UE maintains the target cell configuration and performs synchronization and RACH with the target cell before receiving the HO command, the HO interruption time is reduced.

[0028] When performing pre-RACH to a neighboring cell, the UE still provides services through its serving cell. Depending on the UE's capabilities (e.g., whether the UE has additional RF module sets), communication on the serving cell and RACH to the neighboring cell can be performed in parallel. In some cases, PRACH transmissions to the neighboring cell and UL transmissions to the serving cell can be scheduled at the same time. In one embodiment, transmit (TX) power to the neighboring cell and the serving cell can be scaled based on the same or different scaling factors. If the total TX power exceeds the maximum value, one of the PRACH transmissions to the neighboring cell and the UL transmissions to the serving cell is prioritized while the other is dropped. The prioritized transmission can be either the RACH to the neighboring cell or the transmission on the serving cell. In other cases, multiple RACH transmissions are not allowed to occur simultaneously. In one example, RACH to the configuration cell takes precedence over transmissions on the serving cell. In some embodiments, RACH transmissions to the neighboring cell take precedence over a subset of signaling from the serving cell. For example, RACH to the neighboring cell may not take precedence over RACH transmissions to the serving cell. In another example, RACH to the configuration cell can be deprioritized.

[0029] Depending on the UE's capabilities, for a specific UE, communication on the serving cell and RACH to neighboring cells cannot be performed simultaneously. The UE can use the scheduling gap in the serving cell to send RACH preambles to neighboring cells and monitor the RAR of neighboring cells within the serving cell (i.e., RAR can be transmitted through the serving cell). Alternatively, the UE can use the gap in the serving cell to send preambles to neighboring cells and receive RAR from neighboring cells. The gap in the serving cell is aligned with the RACH procedure, therefore the UE will not lose data transmissions in the serving cell.

[0030] In Contention-Free Random Access (CFRA), the gNB allocates the preamble, and this preamble is called a dedicated random access preamble. The dedicated random access preamble is provided to the UE via RRC signaling (the allocation of the preamble can be specified in the RRC message) or physical layer signaling (DCI on the PDCCH). Therefore, there is no preamble conflict. When dedicated resources are insufficient, the gNB instructs the UE to initiate contention-based random access. CFRA is also known as the three-step RACH procedure: Step 1 – Allocation of the random access preamble; Step 2 – Transmission of the random access preamble (Msg1); Step 3 – Random Access Response (RAR) (Msg2), which includes TA information.

[0031] Figure 4 Examples of performing RACH to a neighboring cell using CFRA are shown according to some embodiments of the present invention. In step 411, UE 401 performs data transmission and reception with the serving base station (i.e., the source gNB) in the serving cell (i.e., the source cell). In step 412, the source gNB provides UE 401 with an RRC configuration / PDCCH command for the activated cell and for triggering a RACH procedure with a neighboring cell (i.e., the target cell) (e.g., from the activated cell). The RRC configuration includes information for the UE to perform DL and UL synchronization on the activated cell, as well as public and private configurations required when the activated cell becomes the UE's serving cell. The RRC / PDCCH command further includes private preamble allocation information for the upcoming CFRA procedure.

[0032] In step 421, UE 401 performs synchronization and RACH procedures to obtain the TA of the neighboring cell by sending a RACH preamble (Msg1) to the neighboring cell. UE 401 can use gaps in the serving cell to send the RACH preamble to the neighboring cell. The gaps in the serving cell are aligned with the RACH procedure, so the UE does not lose data transmission from the serving cell. In step 422, UE 401 monitors the Random Access Response (RAR) (Msg2) from the neighboring cell. In a first alternative, UE 401 directly monitors the RAR from the neighboring cell using gaps in the serving cell. In one example, separate gaps are used for msg-1 TX and msg-2 RX (received) from the neighboring cell. Between gaps, the UE can monitor the activity of the serving cell. In a second alternative, the RAR is sent by the neighboring cell and transmitted to the UE through the serving cell. UE 401 obtains and maintains the TA and configuration of the neighboring cell to complete the RACH procedure.

[0033] In step 431, UE 401 performs neighboring cell measurements and sends a measurement report to the serving gNB. In step 432, the serving gNB makes a cell handover decision based on the measurement report and sends an HO command message to UE 401. Based on the received HO command, UE 401 implements target cell configuration. The HO command can be L1 / L2 / L3 signaling. In step 433, UE 401 sends an HO completion message to the target gNB (located in the target cell), and the handover process is completed. In step 441, UE 401 begins data transmission and reception in the target cell. Because the UE maintains the target cell configuration and performs synchronization and pre-RACH to obtain TA for the target cell before receiving the HO command, the HO interruption time is reduced.

[0034] In the specific implementation Figure 4 Steps 411, 412, 431, 432, 433, and 441 in the text can respectively correspond to Figure 3 Steps 311, 321, 331, 332-341, 342, and 351 in the text, while Figure 4 Steps 421-422 in the text correspond to Figure 3 Step 322 in the diagram. Furthermore, although not illustrated, in... Figure 4 Steps 312-314 can also be performed between steps 411 and 412.

[0035] In Contention-Based Random Access (CBRA), the UE randomly selects a preamble from a preamble pool shared with other UEs. This means that the UE has the potential risk of selecting the same preamble as other UEs and subsequently experiencing collisions or contention. The gNB uses a contention resolution mechanism to handle such access requests. During CBRA, the outcome is random and not all random access will be successful. CBRA is also known as the four-step RACH process: Step 1 – Random Preamble Transmission (Msg1); Step 2 – Random Access Response (RAR) (Msg2); Step 3 – Schedule Uplink Transmission (Msg3); and Step 4 – Contention Resolution (Msg4).

[0036] Figure 5 Examples of performing RACH with neighboring cells using CBRA are shown according to some embodiments of the present invention. In step 511, UE 501 performs data transmission and reception with the serving base station (i.e., the source gNB) in the serving cell. In step 512, the source gNB provides UE 501 with an RRC configuration / PDCCH command, which is used for the active cell and to trigger a RACH procedure with a neighboring cell (i.e., the target cell) (e.g., from the active cell). The RRC configuration includes information for the UE to perform synchronization on the active cell and public and private configurations required when the active cell becomes the UE's serving cell.

[0037] In step 521, UE 501 performs DL synchronization and RACH procedures to obtain the TA of the neighboring cell by sending a RACH preamble (Msg1) to the neighboring cell. UE 501 can use gaps in the serving cell to send the RACH preamble to the neighboring cell. In step 522, UE 501 monitors the Random Access Response (RAR) (Msg2) from the neighboring cell. In a first alternative, UE 501 directly monitors the RAR from the neighboring cell using gaps in the serving cell. In a second alternative, the RAR sent by the neighboring cell is transmitted to UE 501 through the serving cell.

[0038] In step 523, UE 501 sends Msg3 to a neighboring cell. Msg3 can be scheduled by the network to be on the serving cell or a neighboring cell, preferably on the serving cell. In a first alternative, UE 501 sends Msg3 directly to the neighboring cell. In a second alternative, UE 501 sends Msg3 to the serving cell, which then forwards it to the neighboring cell. If the transmission of Msg3 is scheduled by Msg2, the transmission may not require a gap. An additional guard period may be required before or after the Msg3 resource. Subsequently, in step 524, UE 501 monitors Msg4 from either the neighboring cell or the serving cell, preferably from the serving cell. In the first alternative, UE 501 receives Msg4 directly from the neighboring cell. In the second alternative, UE 501 receives Msg4 from the serving cell, which was sent to UE 501 by the neighboring cell. An additional time window needs to be defined for receiving Msg4 from the neighboring cell.

[0039] In step 531, UE 501 performs neighboring cell measurements and sends a measurement report to the serving gNB. In step 532, the serving gNB makes a cell handover decision based on the measurement report and sends an HO command message to UE 501. Based on the received HO command, UE 501 implements target cell configuration. The HO command can be L1 / L2 / L3 signaling. In step 533, UE 501 sends an HO completion message to the target gNB (located in the target cell), and the handover process is completed. In step 541, UE 501 begins data transmission and reception in the target cell. Because the UE maintains the target cell configuration and performs synchronization and pre-RACH to obtain TA for the target cell before receiving the HO command, the HO interruption time is reduced.

[0040] The PDCCH command can be used to trigger a UE to perform a neighboring cell RACH procedure. In a first alternative, the DCI field in the PDCCH command can indicate a RACH procedure directed towards one of the neighboring cells (e.g., neighboring cell ID). The configuration associated with the PDCCH command can indicate only a subset of the PRACH resources, leaving the others for the UE to choose. In one example, the preamble sequence can be indicated by the network. In another example, the RACH timing / resources can be selected by the UE based on UE measurements (e.g., UETX beam, path loss RS). Notably, the initial RACH transmission timing can be configured to occur within a time window following the PDCCH command. In a second alternative, the DCI field of the PDCCH command can carry information about which RACH timing / resources should be performed from the configuration. Therefore, the DCI field carries information for providing a QCL-type D reference (beam), power control reference signal (path loss RS), etc., to determine the PRACH beam direction.

[0041] The RAR can be received from the serving cell or a neighboring cell. If the RAR comes from the serving cell, the UE can assume that it uses the same beam as the received PDCCH-order (QCL-typeD). If the RAR comes from a neighboring cell, the UE can assume that it uses the same beam as the previous RACH transmission (QCL-typeD). Similarly, Msg-3 / Msg-4 TX / RX can come from the serving cell or a neighboring cell. If it comes from the serving cell, the UE can use the same beam as the received PDCCH-order (QCL-typeD). If it comes from a neighboring cell, the UE can use the same beam as the previous RACH transmission (QCL-typeD).

[0042] In the specific implementation Figure 5 Steps 511, 512, 531, 532, 533, and 541 in the text can respectively correspond to Figure 3 Steps 311, 321, 331, 332-341, 342, and 351 in the text, while Figure 5 Steps 521-524 in the text correspond to Figure 3 Step 322 in the diagram. Furthermore, although not illustrated, in... Figure 5 Steps 312-314 can also be performed between steps 511 and 512.

[0043] Figure 6This is a flowchart illustrating a method for early RACH procedures and TA acquisition for neighboring cells according to a novel aspect of the present invention. In step 601, the UE receives a configuration in the serving cell of the mobile communication network, the configuration including information for performing a Random Access Channel (RACH) procedure on a neighboring cell, wherein the neighboring cell is an active cell configured by the network. In step 602, the UE performs the RACH procedure on the neighboring cell, wherein the UE acquires the timing advance (TA) of the neighboring cell. In step 603, the UE receives a handover command from the network to switch from the serving cell to the neighboring cell, wherein the UE acquires the TA of the neighboring cell before receiving the handover command. In step 604, after receiving the handover command, the UE completes the handover to the neighboring cell without performing an additional RACH procedure.

[0044] While the invention has been described by way of example and according to preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments. Rather, it is intended to cover various modifications and similar arrangements (which will be apparent to those skilled in the art). Therefore, the scope of the appended claims should be given the broadest interpretation to cover all such modifications and similar arrangements.

Claims

1. A wireless communication method, characterized in that, include: The user equipment receives a configuration in the serving cell of the mobile communication network, wherein the configuration includes information on performing a random access channel procedure for a neighboring cell, which is an active cell of the mobile communication network configuration. A random access channel procedure is performed on the neighboring cell, wherein the user equipment obtains the timing advance of the neighboring cell; The user equipment receives a handover command from the serving cell to the neighboring cell from the mobile communication network, wherein the user equipment obtains the timing advance of the neighboring cell before receiving the handover command; and Upon receiving the handover command, the handover to the neighboring cell is completed without performing any additional random access channel procedures. The random access channel procedure for the neighboring cell is triggered by the downlink control information field of the physical downlink control channel command. The downlink control information field of the physical downlink control channel command indicates the random access channel procedure for one of the neighboring cells, and the downlink control information field also carries information indicating the timing or resources of the random access channel to be executed from the configuration.

2. The wireless communication method as described in claim 1, characterized in that, The random access channel procedure for the neighboring cell is further configured and triggered by radio resource control signals.

3. The wireless communication method as described in claim 1, characterized in that, The user equipment performs the random access channel procedure for the neighboring cell and the communication with the serving cell in parallel.

4. The wireless communication method as described in claim 3, characterized in that, The transmit power for the neighboring cell and the serving cell can be scaled based on the same or different scaling factors.

5. The wireless communication method as described in claim 3, characterized in that, The user equipment prioritizes random access channel transmissions on the neighboring cell and uplink transmissions on the serving cell.

6. The wireless communication method as described in claim 1, characterized in that, The user equipment uses the scheduling interval in the serving cell to perform the random access channel procedure for the neighboring cell.

7. The wireless communication method as described in claim 6, characterized in that, The user equipment receives Msg3 from the neighboring cell or sends Msg4 to the neighboring cell through the serving cell.

8. The wireless communication method as described in claim 6, characterized in that, The user equipment monitors the activity of the serving cell between multiple gaps.

9. A user equipment, characterized in that, include: A receiver is configured to receive a configuration in a serving cell of a mobile communication network, wherein the configuration includes information on performing a random access channel procedure on a neighboring cell, the neighboring cell being an active cell of the mobile communication network configuration. A random access channel processing circuit is used to perform a random access channel procedure on the neighboring cell, wherein the user equipment obtains the timing advance of the neighboring cell; A handover processing circuit is configured to receive a handover command from the mobile communication network from the serving cell to the neighboring cell, wherein the user equipment obtains the timing advance of the neighboring cell before receiving the handover command; After receiving the handover command, the user equipment completes the handover to the neighboring cell without performing additional random access channel procedures. The random access channel procedure for the neighboring cell is triggered by the downlink control information field of the physical downlink control channel command. The downlink control information field of the physical downlink control channel command indicates the random access channel procedure for one of the neighboring cells, and the downlink control information field also carries information indicating the timing or resources of the random access channel to be executed from the configuration.

10. The user equipment as claimed in claim 9, characterized in that, The random access channel procedure for the neighboring cell is further configured and triggered by radio resource control signals.

11. The user equipment of claim 9, wherein the user equipment performs the random access channel procedure for the neighboring cell and the communication with the serving cell in parallel.

12. The user equipment of claim 11, wherein the transmit power for the neighboring cell and the serving cell may be scaled based on the same or different scaling factors.

13. The user equipment of claim 11, wherein the user equipment prioritizes random access channel transmissions on the neighboring cell and uplink transmissions on the serving cell.

14. The user equipment of claim 9, wherein the user equipment uses the scheduling interval in the serving cell to perform a random access channel procedure for the neighboring cell.

15. The user equipment of claim 14, wherein the user equipment receives Msg3 from the neighboring cell or sends Msg4 to the neighboring cell through the serving cell.

16. The user equipment of claim 14, wherein the user equipment monitors the activity of the serving cell between a plurality of gaps.

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