Method and apparatus for cell handover

Abstract

The application discloses a cell switching method and device, comprising: receiving first information, the first information is that a first node monitors a first cell and a candidate target cell in a candidate target cell set, and is sent as a response to satisfying a first execution condition, the first execution condition comprising: a signal strength of the first cell received by the first node is not higher than a first threshold; informing at least one candidate target cell in the candidate target cell set, so that the first node switches to one of the candidate target cells in response to satisfying a second execution condition; wherein the first node switching to one of the candidate target cells depends on the sending of the first information; the switching is a non-RACH LTM; and the candidate target cell set is preconfigured. The application can better support a condition-based non-RACH LTM cell switching, and avoid resource waste.

Description

Method and device for cell switching

[0001] The present application claims priority from the Chinese patent application No. 202410473331.0 filed on April 18, 2024, and entitled "Method and device for cell switching", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to a method and device in a wireless communication system, and in particular, to a method and device for cell switching in wireless communication. BACKGROUND

[0003] The application scenarios of future wireless communication systems are increasingly diversified, and different application scenarios put forward different performance requirements for the system. In order to meet the different performance requirements of various application scenarios, it is decided at the 72nd plenary meeting of 3GPP (3rd Generation Partnership Project, 3rd Generation Partnership Project) Radio Access Network (Radio Access Network, RAN) to study New Radio (New Radio, NR) (or 5G). At the 75th plenary meeting of 3GPP RAN, the NR work item (Work Item, WI) agenda was passed, and the standardization work of NR began.

[0004] In the new radio technology, cell switching is one of the most basic requirements. The basic requirement of cell switching is to reduce the handover delay and reduce the impact on delay-sensitive services. In order to be able to adapt to various application scenarios and meet different requirements, 3GPP has been evolving the cell switching technology. When the user equipment (User Equipment, UE) performs cell switching, it may involve handover, conditional handover (Conditional Handover, CHO), layer 1 / 2 triggered mobility (Layer1 / 2 triggered mobility, LTM, Layer 1 / 2 triggered mobility, L1 / L2 triggered mobility) cell switching, primary / secondary cell change (Conditional PScell Change, CPC), and the like. SUMMARY

[0005] Although 3GPP introduced CPC, CHO and other technologies in Release 17 (Rel-17), these technologies are still based on Layer 3 (L3) implementation, with long latency, large signaling overhead and long interruption time. Therefore, it was decided at the 3GPP RAN#94e plenary to start WI standardization work on L1 / L2 (Layer 1 / Layer 2) based LTM mobility enhancement technology to improve cell switching.

[0006] In view of the demand for L1 / L2 based mobility enhancement in NR systems, a solution is disclosed. Embodiments and features in embodiments of the present application can be arbitrarily combined without conflict. Further, although the original intention of the present application is for Uu air interface, the present application can also be used for PC5 interface. Further, although the original intention of the present application is for terminal and base station scenarios, the present application is also applicable to other scenarios facing similar problems, such as Vehicle-to-Everything (V2X), terminal and relay, and relay and base station communication scenarios, achieving similar technical effects in terminal and base station scenarios. In addition, using a unified solution in different scenarios (including but not limited to V2X scenarios and terminal and base station communication scenarios) helps to reduce hardware complexity and cost. In particular, the explanation of the terms (Terminology), nouns, functions, and variables in the present application (if not specifically stated) can refer to the definitions in the 3GPP specification protocols TS38 series and TS37 series.

[0007] To solve the above technical problems, the embodiments of the present application provide a method in a first node for cell switching, comprising: monitoring a first cell and candidate target cells in a candidate target cell set, in response to satisfying a first execution condition, sending first information, the first execution condition comprising: the signal strength of the first cell is not higher than a first threshold; in response to satisfying a second execution condition, switching to one of the candidate target cells; the switching to one of the candidate target cells depends on the sending of the first information; wherein the switching is a Random Access Channel-less (RACH-less) LTM cell switch; the candidate target cell set is pre-configured.

[0008] In the embodiment of the present application, on the premise that a candidate target cell set is pre-configured, a first node (such as a UE) can monitor a source cell (a serving cell, for example, a first cell) and a candidate target cell, judge whether the signal strength of the serving cell of the first node is higher than a first threshold, further determine whether a first execution condition is met, and send first information when the first execution condition is met. After sending the first information and when a second execution condition is met, the first node can perform conditional LTM handover to one of the candidate target cells without RACH. This method can realize L1 / L2 cell handover triggered by the first node below L3, reasonably perform conditional LTM cell handover process, improve LTM handover robustness by meeting multiple execution conditions, and perform handover autonomously by the UE, which is conducive to realizing fast exchange of the serving cell.

[0009] As an embodiment, the above method sends the first information only when the first execution condition is met without sending a random access sequence to perform a random access process, and performs LTM handover to a candidate target cell only when the second condition is further met, which can effectively avoid ping-pong handover, greatly reduce handover delay by sending a handover command through a protocol layer below layer three, avoid resource waste, and support non-RACH LTM cell handover.

[0010] As an embodiment, the present application solves the problem of how to support high robustness of UE-triggered cell handover based on conditional non-RACH LTM cell handover and reduce or avoid resource waste. The technical solution provided by the present application solves the above technical problems well.

[0011] As an embodiment, the above method initiates conditional LTM cell handover without RACH by the first node after the first execution condition is met, instead of being autonomously initiated by the serving cell of the first node, which can further adapt to UE communication process and speed up cell handover process.

[0012] As an embodiment, the above method can effectively support the demand for fast cell handover caused by fast channel change and reduce service interruption time.

[0013] As an embodiment, the present application is particularly suitable for use in a mobility enhancement scenario.

[0014] As an embodiment, the first cell is a serving cell or a source cell, which is the serving cell of the first node.

[0015] According to an aspect of the present application, the second execution condition comprises: the received signal strength of the first cell is not higher than a second threshold; or, the second execution condition comprises: the signal strength of at least one candidate target cell is not lower than a third threshold.

[0016] As an embodiment, the signal strength of the first cell can be a channel quality of the first cell, or a signal strength of a reference signal resource or a beam of the first cell, etc.

[0017] As an embodiment, the monitoring of the first cell can be a measurement of the first cell, which is a layer 3 (L3) measurement.

[0018] As an embodiment, the first threshold is a cell-level measurement result, and the second threshold is a beam-level measurement result.

[0019] In an embodiment, the first threshold can be an L3 threshold, and the second threshold can be an L1 threshold. In another embodiment, the first threshold is for multiple reference signal resources, and the second threshold is for one reference signal resource.

[0020] As an embodiment, the first information indicates that the signal strength of the first cell is not higher than the first threshold. In an exemplary example, the first threshold can be pre-configured by a network or be a default default.

[0021] In an embodiment, when the first node sends the first information, it implicitly indicates that the first node meets the condition of performing the LTM without RACH. In yet another embodiment, when the first node sends the first information, it implicitly indicates that the first node preliminarily meets the condition of performing the LTM without RACH, and the possibility of switching to one of the candidate target cells is extremely large after a short time delay. In another embodiment, the first information indicates that the received signal strength of the first cell is not higher than the first threshold, and also indicates that the LTM switching will be performed within a preset time period. For example, the first information uses bit information to indicate that if no other information is reported, the LTM switching will be performed within a preset time period. The preset time period can be pre-configured or be a default default.

[0022] As an embodiment, the detecting of the at least one candidate target cell in the candidate target cell set depends on the sending of the first information. In other words, if the first information is not sent, the first node does not need to detect the at least one candidate target cell in the candidate target cell set. The detecting refers to blind detection of PDCCH (physical downlink control channel) or blind decoding of DCI (downlink control information).

[0023] As an embodiment, the switching to one of the candidate target cells depends on the sending of the first information as a response to the satisfaction of the second execution condition.

[0024] As an embodiment, the switching to one of the candidate target cells depending on the sending of the first information includes that the first information is not sent, and the at least one candidate target cell does not switch to one of the candidate target cells even if the first cell satisfies the second execution condition.

[0025] As an embodiment, the switching to one of the candidate target cells depending on the sending of the first information includes that the first information is not sent, and the at least one candidate target cell does not switch to one of the candidate target cells even if the first cell satisfies the second execution condition.

[0026] As an embodiment, the switching to one of the candidate target cells depending on the sending of the first information includes that the first information is not sent, and the at least one candidate target cell does not switch to one of the candidate target cells even if the first cell satisfies the second execution condition and the at least one candidate target cell satisfies the second execution condition.

[0027] According to an aspect of the present application, the method includes that the first information carries the at least one candidate target cell in the candidate target cell set.

[0028] The first node carries one or more candidate target cells in the first information, so that the serving cell knows clearly the candidate target cell selected by the first node for switching based on the first information, which helps to reduce the information interaction cost between network devices.

[0029] Preferably, the first information only carries one candidate target cell. This technical solution can save power consumption and signaling.

[0030] According to an aspect of the present application, the method includes starting a timer when the first information is sent, and detecting the cell after switching when the timer expires.

[0031] The scheme detects the cell after the handover only after the timer runs for a period of time, which is beneficial to reduce unnecessary power consumption, thereby saving network resources and improving resource utilization.

[0032] According to an aspect of the present application, the method comprises: receiving resource configuration information sent by the cell after the handover, and sending an uplink signal on the cell after the handover based on the resource configuration information.

[0033] The method can quickly realize the sending of the uplink signal on the cell after the handover, thereby completing data interaction.

[0034] According to an aspect of the present application, the received signal strength of the first cell is at least one of: a measurement result of a reference signal; a signal strength of a signal other than the reference signal; a signal strength of a signal other than the reference signal, and the signal strength of the other signal is not higher than the first threshold in a preset time interval.

[0035] The method monitors the signal strength to determine the signal quality of the serving cell, which is beneficial to quickly realize a reasonable handover strategy.

[0036] According to an aspect of the present application, the candidate target cell set is pre-configured by RRC signaling; and the configuration information of the candidate target cell comprises one or more of:

[0037] The cell identifier of the candidate target cell;

[0038] The cell offset of the candidate target cell;

[0039] The transmission power of the candidate target cell.

[0040] The method enables the terminal device (such as the first node) to know the information of the candidate target cell in advance, which is beneficial to subsequently select a suitable handover scheme.

[0041] According to an aspect of the present application, the method comprises: acquiring the timing advance of the target cell after the handover in dependence on the first execution condition being met.

[0042] The method determines whether to acquire the timing advance in dependence on whether the first execution condition is met, thereby avoiding unnecessary resource consumption.

[0043] To solve the above technical problems, the embodiment of the present application further provides a method in a second node for cell handover, comprising: receiving first information, the first information being sent by a first node monitoring a first cell and candidate target cells in a candidate target cell set and as a response to satisfying a first execution condition, the first execution condition comprising: a signal strength of the first cell received by the first node being not higher than a first threshold; informing at least one candidate target cell in the candidate target cell set, so that the first node switches to one of the candidate target cells in response to satisfying a second execution condition; wherein the first node switching to one of the candidate target cells depends on the sending of the first information; the switching is LTM without RACH; and the candidate target cell set is pre-configured.

[0044] According to an aspect of the present application, the first information carries at least one candidate target cell in the candidate target cell set.

[0045] According to an aspect of the present application, the signal strength of the received first cell is at least one of:

[0046] a measurement result of a reference signal;

[0047] a signal strength of a signal other than the reference signal;

[0048] a signal strength of a signal other than the reference signal, and within a preset time interval, the signal strength of the other signal is not higher than the first threshold.

[0049] According to an aspect of the present application, the candidate target cell set is pre-configured by RRC signaling; and the configuration information of the candidate target cell comprises one or more of:

[0050] a cell identifier of the candidate target cell;

[0051] a cell offset of the candidate target cell;

[0052] a transmission power of the candidate target cell.

[0053] As an embodiment, the above method can simplify the UE implementation.

[0054] As an embodiment, the above method is applicable to the scenario that the second node is a base station of the first cell.

[0055] To solve the above technical problems, the embodiment of the present application further provides a method for a third node in cell switching, comprising: receiving notification information sent from a second node, wherein the notification information comprises at least one candidate target cell in a candidate target cell set, and the candidate target cell set is pre-configured by the second node to a first node, so that the first node monitors a first cell and each candidate target cell in the candidate target cell set, and sends first information to the second node in response to satisfying a first execution condition; wherein the first execution condition comprises that the received signal strength of the first cell is not higher than a first threshold; the first node switches to one of the candidate target cells in response to satisfying a second execution condition; the switching to one of the candidate target cells depends on the sending of the first information; and the switching is LTM without RACH.

[0056] According to an aspect of the present application, the first information carries at least one candidate target cell in the candidate target cell set.

[0057] According to an aspect of the present application, the received signal strength of the first cell is at least one of the following: a measurement result of a reference signal; a signal strength of a signal other than the reference signal; a signal strength of a signal other than the reference signal, and the signal strength of the other signal is not higher than the first threshold within a preset time interval.

[0058] According to an aspect of the present application, the candidate target cell set is pre-configured by the second node through RRC signaling; and the configuration information of the candidate target cell comprises one or more of the following:

[0059] a cell identifier of the candidate target cell;

[0060] a cell offset of the candidate target cell;

[0061] a transmission power of the candidate target cell.

[0062] To solve the above technical problems, the embodiment of the present application further provides a first node for cell switching, comprising: a first transceiver, which monitors a first cell and a candidate target cell in a candidate target cell set, and sends first information in response to satisfying a first execution condition, wherein the first execution condition comprises that the signal strength of the first cell is not higher than a first threshold; a second processor, which switches to one of the candidate target cells in response to satisfying a second execution condition; the switching to one of the candidate target cells depends on the sending of the first information; wherein the switching is LTM without RACH; and the candidate target cell set is pre-configured.

[0063] As an embodiment, the candidate target cell set is pre-configured by the second node.

[0064] As an embodiment, the monitoring of the first cell and the candidate target cells in the candidate target cell set comprises detecting each candidate target cell in the target cell set.

[0065] To solve the above technical problem, the embodiment of the present application further provides a second node for cell switching, comprising: a first transmitter, receiving first information, the first information being sent by a first node in response to monitoring of a first cell and candidate target cells in a candidate target cell set and satisfying a first execution condition, the first execution condition comprising: signal strength of the first cell received by the first node being not higher than a first threshold; a first processor, notifying at least one candidate target cell in the candidate target cell set, so that the first node switches to one of the candidate target cells in response to satisfying a second execution condition; wherein the switching of the first node to one of the candidate target cells depends on the sending of the first information; the switching is LTM without RACH; and the candidate target cell set is pre-configured.

[0066] To solve the above technical problem, the embodiment of the present application further provides a third node for cell switching, comprising: a receiving module, receiving notification information sent by a second node, the notification information comprising at least one candidate target cell in a candidate target cell set, the candidate target cell set being pre-configured by the second node to a first node, so that the first node monitors a first cell and candidate target cells in the candidate target cell set and sends first information to the second node in response to satisfying a first execution condition; wherein the first execution condition comprises: signal strength of the first cell received being not higher than a first threshold; the first node switches to one of the candidate target cells in response to satisfying a second execution condition; the switching to one of the candidate target cells depends on the sending of the first information; and the switching is LTM without RACH.

[0067] To solve the above technical problem, the embodiment of the present application further provides a storage medium, having computer instructions stored thereon, the computer instructions being executed to perform the steps of the above method. Optionally, the embodiment of the present application further provides a cell switching device, comprising various modules or units for performing the method in any possible implementation manner. Optionally, the embodiment of the present application further provides a cell switching device, comprising a processor. The processor is coupled with a memory and is used to execute instructions in the memory to implement the method in any possible implementation manner. Optionally, the cell switching device further comprises the memory. Optionally, the cell switching device further comprises a communication interface, and the processor is coupled with the communication interface.

[0068] To solve the above technical problems, the embodiment of the present application further provides a terminal, comprising a memory and a processor, wherein the memory stores computer instructions executable on the processor, and the processor executes the steps of the above method when executing the computer instructions.

[0069] To solve the above technical problems, the embodiment of the present application further provides a network device, comprising a memory and a processor, wherein the memory stores computer instructions executable on the processor, and the processor executes the steps of the above method when executing the computer instructions.

[0070] Compared with the prior art, the technical scheme of the embodiment of the present application has the following beneficial effects:

[0071] The embodiment of the present application provides a method in a first node for cell switching, comprising: monitoring a first cell and each candidate target cell in a candidate target cell set, in response to satisfying a first execution condition, sending first information to a second node, the first execution condition comprising: the received signal strength of the first cell is not higher than a first threshold; in response to satisfying a second execution condition, switching to one of the candidate target cells; the switching to one of the candidate target cells depends on the sending of the first information; wherein the switching is RACH-less LTM; and the candidate target cell set is pre-configured by the second node. In the method provided by the embodiment of the present application, the first node can be pre-configured with a candidate target cell set, and after monitoring the serving cell and the candidate target cell, it is determined whether the signal strength of the serving cell is higher than the first threshold, and then it is determined whether the first execution condition and the second execution condition are satisfied, and the first information is sent when the first execution condition is satisfied. Depending on the sending of the first information, when the second execution condition is satisfied, the LTM is performed based on RACH, and the cell is switched to a suitable target cell. This method can realize UE self-triggered cell switching, realize fast switching of L1 / L2 serving cells, and improve the switching robustness by satisfying the double execution conditions before performing the switching.

[0072] Further, the above method eliminates the random access process, sends the first information only when the first execution condition is satisfied, and switches to the candidate target cell by LTM only when the second execution condition is satisfied depending on the sending of the first information, which can effectively avoid ping-pong switching and greatly reduce the switching delay by completing the switching through the protocol layer below L3.

[0073] Further, the above method initiates the RACH-less LTM cell switching by the first node when the first execution condition is satisfied, rather than by the serving cell of the first node, which can further speed up the cell switching process.

[0074] As one embodiment, the above method can effectively support the fast cell handover requirement due to fast channel variation, and reduce the service interruption time.

[0075] As one embodiment, the above method is especially suitable for mobility enhancement scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0076] Other features, objects, and advantages of the application will become more apparent from the following detailed description when read in conjunction with the accompanying drawings:

[0077] Fig. 1 illustrates a flowchart of a handover method in a first node according to one embodiment of the present application;

[0078] Fig. 2 illustrates a schematic diagram of a network architecture according to one embodiment of the present application;

[0079] Fig. 3 illustrates a schematic diagram of a radio protocol architecture for the user and control planes according to one embodiment of the present application;

[0080] Fig. 4 illustrates a schematic diagram of hardware modules of a communication device according to one embodiment of the present application;

[0081] Fig. 5 illustrates a flowchart of a wireless signal transmission according to one embodiment of the present application;

[0082] Fig. 6 illustrates a schematic diagram of a part of the flowchart of the handover method in a first node according to one embodiment of the present application;

[0083] Fig. 7 illustrates a schematic diagram of a part of the flowchart of the handover method in a first node according to one embodiment of the present application;

[0084] Fig. 8 illustrates a schematic diagram of detecting a cell after handover according to one embodiment of the present application;

[0085] Fig. 9 illustrates a structural block diagram of a processing apparatus in a first node according to one embodiment of the present application;

[0086] Fig. 10 illustrates a structural block diagram of a processing apparatus in a second node according to one embodiment of the present application;

[0087] Fig. 11 illustrates a structural block diagram of a processing apparatus in a third node according to one embodiment of the present application. DETAILED DESCRIPTION

[0088] As mentioned in the background, in the prior art, there are various technical implementation forms of mobility management such as cell handover, including layer 3 (L3) handover and layer 1 / layer 2 handover below layer 3. The development of conditional handover (CHO) and other conditional migration procedures (CPAC, SCPAC) enables the handover procedure to be executed without prior signaling interaction with the source cell, and also enables high robustness. The LTM technology introduced in Rel-18 provides a shorter interruption time, but its robustness is not as good as that of the conditional L3 mobility procedure. It is necessary to enhance this function in the process of NR evolution, so that the wireless communication system can benefit from high robustness and short interruption time.

[0089] Currently, a network device can provide one or more candidate configurations for a terminal device (such as a UE), and each candidate configuration can include one or more cells. The network device can subsequently control the terminal device to change in multiple candidate configurations through L1 or L2 signaling, that is, cell change control signaling, to achieve service cell change. This procedure can be referred to as an LTM procedure.

[0090] The general procedure of LTM is as follows: first, a terminal device in an RRC connected state reports measurement results to a source cell. In the case that the terminal device supports LTM, the source cell can send an LTM cell handover request to a candidate target cell. After the candidate target cell sends an LTM cell handover request response to the source cell, and sends the configured configuration information of the corresponding LTM candidate target cell to the source cell, the source cell can send RRC reconfiguration information to the terminal device. The RRC reconfiguration information can carry the configuration information of the LTM candidate target cell.

[0091] After receiving the configuration information of the LTM candidate target cell, the terminal device sends an RRC reconfiguration complete message to the source cell. Then, the terminal device performs downlink synchronization and uplink synchronization for each candidate target cell.

[0092] In the process of performing uplink synchronization for each candidate target cell, if the RRC reconfiguration information indicates that the timing advance (TA) is measured by the terminal device itself, the terminal device can measure the timing advance of the source cell, and determine the timing advance of the candidate target cell according to the time difference in receiving the source cell and the candidate cell; or the source cell triggers the contention free random access (CFRA) through the physical downlink control channel order (PDCCH) to obtain the timing advance of the candidate target cell, the terminal device initiates the CFRA to the candidate target cell to obtain the timing advance of the candidate target cell, and then the source cell determines the validity of the timing advance.

[0093] After the uplink synchronization is completed, the terminal device performs layer 1 (L1) measurement on the source cell and the candidate target cell to obtain L1 measurement results, and then the terminal device reports the L1 measurement results to the source cell. After the terminal device reports the L1 measurement results to the source cell, the source cell can determine the target cell according to the L1 measurement results. The source cell sends an LTM switching instruction to the terminal device.

[0094] The LTM switching instruction can be a medium access control (MAC) control element (CE). The MAC CE contains at least the following information: TA, transmission configuration indication state (TCI state) identity (ID), resource information of CFRA, and configuration information identifier of the LTM candidate primary cell. If the source cell determines that the TA obtained by the terminal device before is still in a valid state, the TA can be included in the MAC CE.

[0095] Further, the terminal device disconnects the connection with the source cell and initiates a random access process to the candidate target cell. When the terminal device receives the MAC CE, if the MAC CE carries the TA or the terminal device measures the TA by itself, the terminal device initiates the switching without random access to the candidate target cell, that is, the terminal device sends an uplink signaling or a first uplink data packet to the candidate target cell to indicate that it has accessed the candidate target cell, so as to complete the LTM cell switching.

[0096] For the scenario without RACH, when changing the cell, the terminal device can not initiate a random access process in the candidate target cell. The uplink transmission resource of the candidate target cell can be indicated to the terminal device in the following manner:

[0097] Dynamic scheduling: the terminal obtains an uplink grant (i.e., dynamic grant) by listening to the PDCCH of the target cell;

[0098] Semi-static scheduling: the network configures a periodic uplink grant (i.e., configured grant).

[0099] Considering that the LTM is mainly aimed at a shorter interruption time, Rel-18 supports the RACH-free procedure. If NR supports the conditional LTM in the subsequent evolution without RACH, it will cause information deviation between the network and the UE, the network does not know when the UE switches, and the network has to always reserve resources, which will cause resource waste; if the resources are not always reserved, robustness problems will occur.

[0100] The embodiment of the application provides a method in a first node for cell switching, comprising: monitoring a first cell and each candidate target cell in a candidate target cell set, in response to satisfying a first execution condition, sending first information to a second node, the first execution condition comprising: the received signal strength of the first cell is not higher than a first threshold; in response to satisfying a second execution condition, switching to one of the candidate target cells; the switching to one of the candidate target cells depends on the sending of the first information; wherein the switching is LTM without RACH; the candidate target cell set is pre-configured by the second node.

[0101] In the method provided by the embodiment of the application, the first node can be pre-configured with a candidate target cell set, and after monitoring the serving cell and the candidate target cell, it can determine whether the signal strength of the serving cell is higher than a first threshold, and then determine whether the first execution condition and the second execution condition are satisfied, and send the first information when the first execution condition is satisfied; and in response to sending the first information, perform LTM cell switching to a suitable target cell under the condition without RACH when the second execution condition is satisfied. The method can realize UE self-triggered cell switching, is conducive to guaranteeing the switching robustness, reducing resource waste, and improving resource utilization.

[0102] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the specific embodiments of the application will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments of the application and the features in the embodiments can be arbitrarily combined with each other without conflict.

[0103] For the convenience of clearly describing the technical solutions of the embodiments of the present application, in the embodiments of the present application, the terms of "first", "second", etc. are used to distinguish the same or similar items with basically the same functions and effects. For example, the first chip and the second chip are only used to distinguish different chips, and do not limit the sequence. Those skilled in the art can understand that the terms of "first", "second", etc. do not limit the quantity and execution sequence, and the terms of "first", "second", etc. also do not necessarily mean different.

[0104] It should be noted that in the embodiments of the present application, the words of "exemplary" or "for example" are used to represent as an example, illustration or description. Any embodiment or design scheme described as "exemplary" or "for example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. In fact, the words of "exemplary" or "for example" are intended to present the related concept in a specific way.

[0105] Embodiment 1

[0106] Embodiment 1 illustrates a flowchart of a handover method in a first node according to an embodiment of the present application, as shown in FIG. 1. The handover method is performed by the first node, for example, by a terminal device; by a UE. The handover method can include the following steps:

[0107] Step S101, monitoring a first cell and each candidate target cell in a candidate target cell set, in response to satisfying a first execution condition, sending first information to a second node, the first execution condition comprising: the received signal strength of the first cell is not higher than a first threshold;

[0108] Step S102, in response to satisfying a second execution condition, switching to one of the candidate target cells; the switching to one of the candidate target cells depends on the sending of the first information.

[0109] Wherein, the switching is LTM without RACH; the candidate target cell set is pre-configured by the second node.

[0110] Specifically, the first node can receive the candidate target cell set pre-configured by the second node before step S101. The candidate target cell set includes one or more candidate target cells. In an embodiment, the second node is a base station of the first cell. The first cell is a serving cell of the first node, and / or is a primary serving cell of the first node, and / or is a source cell of the LTM handover flow.

[0111] As an embodiment, the configuration information of the candidate target cell can comprise one or more of the following: a cell identity of the candidate target cell; a cell offset of the candidate target cell; a transmit power of the candidate target cell.

[0112] In one embodiment, the handover refers to RACH-less LTM; or can be referred to as RACH-less conditional LTM, or can be referred to as RACH-less layer 1 / layer 2 triggered mobile cell handover. Conditional LTM refers to performing LMT cell handover based on UE trigger.

[0113] In step S101, the first node, after receiving the pre-configured candidate target cell set, stores configuration information of the candidate target cell set and configuration information of each candidate target cell. The first node can monitor / measure the first cell and each candidate target cell in the candidate target cell set. The first node can report the measurement results in a conventional manner.

[0114] In one embodiment, when the measurement result shows that the signal strength of the first cell is lower than or equal to the first threshold, the first node determines that the first execution condition is met. At this time, the first node can send the first information to the first cell in response to meeting the first execution condition.

[0115] As an embodiment, the first information comprises that the received signal strength is not higher than the first threshold. As a variant embodiment, the first information indicates that the received signal strength is not higher than the first threshold. The first information can trigger the execution of LTM. In other words, LTM depends on the sending of the first information. Without sending the first information, LTM will not be executed.

[0116] As an embodiment, the detection of at least one candidate target cell in the candidate target cell set depends on the sending of the first information.

[0117] As an embodiment, the handover to one of the candidate target cells in response to meeting the second execution condition depends on the sending of the first information.

[0118] As an embodiment, the handover to one of the candidate target cells in response to the sending of the first information comprises that when the first information is not sent, the at least one candidate target cell does not meet the second execution condition either, and will not be handed over to one of the candidate target cells.

[0119] As an embodiment, the switching to one of the candidate target cells depends on the sending of the first information comprises: when the first information is not sent, there is no need to determine whether the at least one candidate target cell meets the second execution condition for switching to one of the candidate target cells.

[0120] As an embodiment, the switching to one of the candidate target cells depends on the sending of the first information comprises: when the first information is not sent, there is no need to measure whether the at least one candidate target cell meets the second execution condition for switching to one of the candidate target cells.

[0121] In an embodiment, the first execution condition can comprise that the received signal strength of the first cell is not higher than a first threshold. In an embodiment, the first execution condition can comprise that the received signal strength of the first cell is not higher than the first threshold, and the received signal strength of at least one of the candidate target cells is higher than a preset threshold, such as a first preset threshold.

[0122] In an embodiment, the signal strength of the first cell can be the channel quality of the first cell.

[0123] As an embodiment, the received signal strength of the first cell can be the average of one or more of the following: the measurement result of a reference signal; the signal strength of a signal other than the reference signal; the signal strength of a signal other than the reference signal, and the signal strength of the other signal is not higher than the first threshold within a preset time interval.

[0124] The measurement result of the reference signal can be the measurement result of a single reference signal, or the measurement result of multiple reference signals. The reference signal includes but is not limited to SSB (Synchronization Signal Block) and CSI-RS (Channel Status Information-Reference Signal).

[0125] As an embodiment, the cell switching is performed at a protocol layer below layer three. The protocol layer below layer three includes the MAC sublayer and the physical layer.

[0126] As a sub-embodiment of the above embodiment, the cell switching is performed at the MAC sublayer.

[0127] As a sub-embodiment of the above embodiment, the cell switching is performed at the physical layer.

[0128] As an embodiment, the first threshold is a measured value, or a configured value, or a default value, or a value after linear processing of a measured value and a configured value.

[0129] As an embodiment, when a signal strength of a cell is less than a threshold, a channel quality of the cell is worse than the threshold. Conversely, when a channel quality of a cell is greater than a threshold, the channel quality of the cell is better than the threshold.

[0130] As an embodiment, a signal strength of a cell is represented by RSRP (Reference Signal Received Power), or RSRQ (Reference Signal Received Quality), or RSSI (Received Signal Strength Indicator), or SINR (Signal to Interference & Noise Ratio).

[0131] In an embodiment, the signal strength of the first cell can be a channel quality of the first cell, or a signal strength of a reference signal resource, or a beam of the first cell, etc.

[0132] As an embodiment, a signal strength of a cell is obtained by measuring a reference signal of the cell.

[0133] As an embodiment, cell measurement is performed at a protocol layer below L3.

[0134] As an embodiment, cell measurement is performed at L1, or cell measurement is performed at L1 and L3.

[0135] As an embodiment, a signal strength of a cell is obtained by linear processing of a measured value of a reference signal of the cell and a configured offset value. In a specific implementation, the configured offset value includes at least one of a measurement object specific offset value, a cell specific offset value, an event specific offset value, and an event hysteresis parameter value.

[0136] As an embodiment, the signal strength of the first cell being worse than the first threshold includes: Mp < Mn; wherein the Mp is the signal strength of the first cell; and the first threshold is the Mn. In an implementation, the Mn is a signal strength of a candidate target cell in the candidate target cell set.

[0137] As one embodiment, the signal strength of the first cell being worse than the first threshold comprises: Mp < Threshl; wherein the Mp is the signal strength of the first cell; the first threshold is the Threshl, which is configured.

[0138] As one embodiment, the received signal strength of the first cell is lower than a second threshold; the second threshold is less than the first threshold.

[0139] As one embodiment, the signal strength of the candidate target cell being better than the third threshold comprises: Mn > Thresh3; wherein the Mn is the signal strength of the candidate target cell; the third threshold is the Thresh3, which is configured.

[0140] As one embodiment, the signal strength of the first cell being worse than the first threshold comprises: Mn + Ofn + Ocn - Hys > Mp + Ofp + Ocp + Off; wherein the signal strength of the first cell is Mp + Ofp + Ocp + Off; the first threshold is Mn + Ofn + Ocn - Hys; the Mp is the result of measurement for the first cell; the Ofp is the measurement object specific offset value for the first cell; the Ocp is the cell specific offset value for the first cell; the Off is the offset value for the event; the Mn is the result of measurement for the candidate target cell; the Ofn is the measurement object specific offset value for the candidate target cell; the Ocn is the cell specific offset value for the candidate target cell; the Hys is the hysteresis parameter value for the event; when the Mp and the Mn are RSRP, the units of the Mp and the Mn are dBm (decibel-milliwatt); when the Mp and the Mn are RSRQ or RS-SINR (Reference Signal Signal to Interference and Noise Ratio), the units of the Mp and the Mn are dB (decibel); the units of the Ofn, the Ocn, the Ofp, the Ocp, the Hys and the Off are dB.

[0141] As one embodiment, the signal strength of the first cell being worse than the first threshold comprises: Mp + Hys < Threshl; wherein the signal strength of the first cell is Mp + Hys, the first threshold is Threshl; the Mp is the result of measurement for the first cell; the Hys is the hysteresis parameter value for the event; the Threshl is configured.

[0142] As an embodiment, the signal strength of the candidate target cell being better than the third threshold comprises: the signal strength of the candidate target cell being Mn+Ofn+Ocn-Hys, and the third threshold being Thresh3; wherein the Mn is a result measured for the candidate target cell; the Ofn is a measurement object specific offset value for the candidate target cell; the Ocn is a cell specific offset value for the candidate target cell; the Hys is a hysteresis parameter value for the event; and the Thresh3 is configured.

[0143] As an embodiment, when the Mp and the Mn are RSRP, the units of the Mp and the Mn are dBm; when the Mp and the Mn are RSRQ or RS-SINR, the units of the Mp and the Mn are dB; the units of the Ofn, the Ocn and the Hys are dB, the unit of the Thresh1 is the same as that of the Mp; and the unit of the Thresh2 is the same as that of the Mn.

[0144] As an embodiment, the first cell is a serving cell of the first node.

[0145] As an embodiment, the first cell is a SpCell (Special Cell).

[0146] As an embodiment, the first cell is a PCell (Primary Cell).

[0147] As an embodiment, the first information is a MAC CE (Control Element).

[0148] As an embodiment, the first information is physical layer information.

[0149] As an embodiment, the first information indicates that the received signal strength is not higher than the first threshold. As another embodiment, the first information carries at least one candidate target cell, such as an identifier of a candidate target cell.

[0150] In a specific implementation, after the second node receives the first information, the second node knows that the first node is going to perform a RACH-free conditional LTM cell handover. Then, the second node can notify at least one of the candidate target cells in the candidate target cell set, so that at least one of the candidate target cells reserves resources for the first node to complete the LTM handover.

[0151] In one embodiment, the first information carries a plurality of candidate target cells, in which case the second node learns that the first node intends to perform LTM handover to one of the plurality of candidate target cells without RACH, and exchanges information with the plurality of candidate target cells, so that the plurality of candidate target cells reserve resources for the first node to select one of the plurality of candidate target cells and quickly complete LTM handover.

[0152] In one preferred embodiment, the first information carries only one candidate target cell, in which case the second node learns that the first node intends to perform LTM handover to the candidate target cell without RACH, and exchanges information with the candidate target cell, so that the candidate target cell reserves resources for the first node to quickly complete LTM handover. In a specific implementation, the channel quality or signal strength of the candidate target cell is better than those of other candidate target cells.

[0153] As one embodiment, the first node can obtain the timing advance of the target cell after handover in dependence on satisfying the first execution condition. In a specific implementation, the first node can use a RACH-free solution after satisfying the first execution condition. In one example, the first node can obtain the timing advance based on RS, or based on receiving timing difference, such as the RACH-free mechanism in LTE, based on UE's TA measurement, etc.

[0154] As one embodiment, the first node needs to complete uplink synchronization with the candidate target cell before LTM handover.

[0155] As one embodiment, the first node can obtain the timing advance of the candidate target cell from the first cell, or autonomously obtain the timing advance of the candidate target cell from the candidate target cell.

[0156] Suppose the value of the target timing advance is t; if the uplink transmission time slot of the uplink signal is n, the first node starts to transmit the uplink signal at a time point t before the start time point of the corresponding downlink time slot n.

[0157] As one embodiment, the value of the target timing advance is related to the subcarrier spacing of the uplink signal.

[0158] As one embodiment, the timing advance is a positive integer less than 4096; or the value of the timing advance is 0, 1, 2,..., 3846.

[0159] In step S102, as a response to satisfying the second execution condition, the first node switches to one of the candidate target cells in dependence on the sending of the first information.

[0160] In a specific implementation, the at least one candidate target cell includes only one candidate target cell. Upon satisfying the second execution condition, the first node switches to the candidate target cell after sending the first information. In another specific implementation, upon satisfying the second execution condition, the first node selects the best-performing one of the candidate target cells, and switches to the selected candidate target cell after sending the first information.

[0161] In one embodiment, the second execution condition includes that the received signal strength of the first cell is not higher than a second threshold.

[0162] In another embodiment, the second execution condition includes that the received signal strength of the candidate target cell is not lower than a third threshold. In a specific implementation, the third threshold is greater than the first threshold.

[0163] In another embodiment, the second execution condition includes that the received signal strength of the first cell is not higher than a second threshold, and that the received signal strength of the candidate target cell is not lower than a third threshold. In a specific implementation, the second threshold is less than the first threshold, and the third threshold is greater than the first threshold.

[0164] In a specific implementation, the second threshold is less than the first threshold. In a specific implementation, the first threshold is cell-level, and the second threshold is beam-level.

[0165] In another specific implementation, the first threshold is L3-derived, and the second threshold is L1-derived.

[0166] In another specific implementation, the first threshold is L3-derived, and the second threshold and the third threshold are L1-derived.

[0167] In another specific implementation, the first threshold is L3-derived, and the third threshold is L1-derived.

[0168] In yet another specific implementation, the first threshold is for a plurality of reference signal resources, and the second threshold and / or the third threshold is for one reference signal resource.

[0169] In yet another embodiment, the second execution condition includes that the received signal strength of the candidate target cell is not lower than a third threshold. In a specific implementation, the third threshold is greater than the first threshold.

[0170] As an embodiment, the uplink signal can be transmitted on the post-handoff cell after the first node switches to the candidate target cell. In an implementation, the post-handoff cell is taken as a new serving cell after the first node completes the LTM handoff, and the first node receives physical layer signaling (e.g., DCI) carrying resource configuration from the new serving cell.

[0171] In an implementation, the DCI contains resource configuration information. After receiving the DCI signaling, the first node can transmit the uplink signal on the post-handoff cell based on the resource configuration information.

[0172] As an embodiment, the uplink signal can be uplink signaling transmitted via PUCCH (Physical Uplink Control Channel). As another embodiment, the uplink signal can be uplink data transmitted via PUSCH (Physical Uplink Shared Channel). Alternatively, the uplink signal can include both uplink signaling and uplink data transmitted via PUSCH.

[0173] As an embodiment, the air interface resource occupied by the uplink signal is indicated by the DCI signaling.

[0174] As an embodiment, the air interface resource occupied by the uplink signal is pre-configured.

[0175] As an embodiment, the air interface resource occupied by the uplink signal belongs to uplink configured grant.

[0176] As an embodiment, the air interface resource includes at least one of time domain resource, frequency domain resource, code domain resource, or spatial resource.

[0177] As an embodiment, the timing advance is applied to the uplink wireless signal.

[0178] As an embodiment, the timing advance is applied to the uplink signal includes that the timing advance is used to determine a target timing advance value, which is an advance value of a starting time of an uplink time unit for transmitting the uplink signal relative to a corresponding downlink time unit. The time unit can be frame, subframe, slot, or symbol.

[0179] Embodiment 2

[0180] Embodiment 2 illustrates a network architecture diagram according to one embodiment of the application, as shown in FIG. 2. FIG. 2 illustrates a diagram of a network architecture 200 for NR 5G, LTE (Long-Term Evolution), and LTE-A (Long-Term Evolution Advanced) systems. The NR 5G, LTE, or LTE-A network architecture 200 can be referred to as a 5GS (5G System) / EPS (Evolved Packet System) 200 or some other suitable terminology. The 5GS / EPS 200 can include one or more UEs 201, NG-RAN (Next Generation Radio Access Network) 202, 5GC (5G Core Network) / EPC (Evolved Packet Core) 210, HSS (Home Subscriber Server) / UDM (Unified Data Management) 220, and Internet services 230. The 5GS / EPS can interconnect with other access networks, but these entities / interfaces are not shown for simplicity. As shown, the 5GS / EPS provides packet-switched services, however, those skilled in the art will readily appreciate that the various concepts presented throughout this disclosure can be extended to networks providing circuit- switched services or other cellular networks. The NG-RAN includes NR Node Bs (gNBs) 203 and other gNBs 204. The gNBs 203 provide user and control plane protocol terminations toward the UEs 201. The gNBs 203 can be connected to the other gNBs 204 via an Xn interface (e.g., backhaul). The gNBs 203 can also be referred to as base stations, base transceiver stations, radio base stations, radio transceivers, transceiver functions, basic service sets (BSSs), extended service sets (ESSs), TRPs (Transmission Reception Points), or some other suitable terminology, and in NTN (Non Terrestrial Network, satellite network) networks, the gNBs 203 can be satellites, aircrafts, or ground base stations relayed through satellites. The gNBs 203 provide the UEs 201 with access to the 5GC / EPC 210.Examples of UE 201 include cellular phones, smart phones, Session Initiation Protocol (SIP) phones, laptop computers, Personal Digital Assistants (PDAs), satellite radios, global positioning systems, multimedia devices, video devices, digital audio players (e.g., MP3 players), cameras, game consoles, unmanned aerial vehicles, aerial vehicles, narrowband internet of things devices, machine type communication devices, land vehicles, automobiles, vehicular equipment, vehicular communication units, wearable devices, or any other similar functional device. Those skilled in the art will also recognize that a UE 201 can be referred to as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.gNB 203 is connected by an S1 / NG interface to 5GC / EPC 210. 5GC / EPC 210 includes MME (Mobility Management Entity) / AMF (Authentication Management Field) / SMF (Session Management Function) 211, other MME / AMF / SMF 214, S-GW (Service Gateway) / UPF (User Plane Function) 212, and P-GW (Packet Date Network Gateway) / UPF 213. MME / AMF / SMF 211 is the control node that processes the signaling between UE 201 and 5GC / EPC 210. Generally, MME / AMF / SMF 211 provides bearer and connection management. All user IP (Internet Protocol) packets are transferred through S-GW / UPF 212, which itself connects to P-GW / UPF 213. The P-GW provides UE IP address allocation as well as other functions. P-GW / UPF 213 connects to Internet services 230. Internet services 230 include operator corresponding Internet protocol services, which can include the Internet, intranet, IMS (IP Multimedia Subsystem), and PS (Packet Switching) streaming services, among others.

[0181] As one embodiment, the UE 201 corresponds to a first node in the present invention.

[0182] As one embodiment, the gNB 203 corresponds to the second node and or the third node in the application.

[0183] As one embodiment, the gNB 203 is a Macro Cell base station.

[0184] As one embodiment, the gNB 203 is a Micro Cell base station.

[0185] As one embodiment, the gNB 203 is a Pico Cell base station.

[0186] As one embodiment, the gNB 203 is a Femto Cell base station.

[0187] As one embodiment, the gNB 203 is a base station device supporting large latency difference.

[0188] As one embodiment, the gNB 203 is a flying platform device.

[0189] As one embodiment, the gNB 203 is a satellite device.

[0190] As one embodiment, the gNB 203 is a test device (e.g. a transceiver simulating part of the function of a base station, a signaling tester).

[0191] As one embodiment, the other gNB 204 is a Macro Cell base station.

[0192] As one embodiment, the other gNB 204 is a Micro Cell base station.

[0193] As one embodiment, the other gNB 204 is a Pico Cell base station.

[0194] As one embodiment, the other gNB 204 is a Femto Cell base station.

[0195] As one embodiment, the other gNB 204 is a base station device supporting large latency difference.

[0196] As one embodiment, the other gNB 204 is a flying platform device.

[0197] As one embodiment, the other gNB 204 is a satellite device.

[0198] As one embodiment, the other gNB 204 is a test equipment (e.g. a transceiver emulating part of the functionality of a base station, a signaling tester).

[0199] As one embodiment, the wireless link from the UE 201 to the gNB 203 is an uplink, which is used to perform uplink transmission.

[0200] As one embodiment, the wireless link from the gNB 203 to the UE 201 is a downlink, which is used to perform downlink transmission.

[0201] As one embodiment, the UE 201 and the gNB 203 are connected through a Uu interface.

[0202] Embodiment 3

[0203] Embodiment 3 illustrates a schematic diagram of a radio protocol architecture for the user and control planes according to an embodiment of the present application, as shown in FIG. 3. FIG. 3 is a schematic diagram illustrating an embodiment of a radio protocol architecture for the user plane 350 and control plane 300, which shows the control plane 300 of a UE and gNB radio protocol architecture at three layers: Layer 1, Layer 2, and Layer 3. Layer 1 (LI) is the lowest layer and implements various PHY (Physical layer) signal processing functions. The LI layer will be referred to as the PHY 301 herein. Layer 2 (L2 layer) 305 is above the PHY 301 and is responsible for the link between the UE and gNB by means of the PHY 301. The L2 layer 305 includes a MAC sublayer 302, a RLC (Radio Link Control) sublayer 303, and a PDCP (Packet Data Convergence Protocol) sublayer 304, which are terminated at the gNB on the network side. The PDCP sublayer 304 provides data ciphering and integrity protection, and also handles handover between gNBs. The RLC sublayer 303 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and also provides duplicate data packet detection and protocol error detection. The MAC sublayer 302 provides mapping between logical and transport channels and multiplexing of logical channel identities. The MAC sublayer 302 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer 302 is also responsible for HARQ (Hybrid Automatic Repeat Request) operations. The RRC (Radio Resource Control) sublayer 306 in Layer 3 (L3 layer) in the control plane 300 is responsible for obtaining radio resources (i.e., radio bearers) and configuring the lower layers using RRC signaling between the gNB and the UE. Although not shown, there can also be a V2X layer above the RRC sublayer 306 in the control plane 300 of the UE, which is responsible for generating a PC5 QoS parameter set and QoS rules according to received service data or service request, generating a PC5 QoS flow corresponding to the PC5 QoS parameter set and sending the PC5 QoS flow identification and the corresponding PC5 QoS parameter set to an AS (Access Stratum) layer for QoS processing of data packets belonging to the PC5 QoS flow identification by the AS layer; the V2X layer also includes a PC5-S (PC5-Signaling Protocol) sublayer, which is responsible for indicating the AS layer whether each transmission is a PC5-S transmission or a V2X service data transmission.The radio protocol architecture of the user plane 350 includes layer 1 (LI layer) and layer 2 (L2 layer), which are substantially the same in the user plane 350 as the corresponding layers and sub-layers in the control plane 300 for the physical layer 351, the PDCP sub-layer 354 in the L2 layer 355, the RLC sub-layer 353 in the L2 layer 355, and the MAC sub-layer 352 in the L2 layer 355, but the PDCP sub-layer 354 also provides header compression for upper layer data packets to reduce radio transmission overhead. The L2 layer 355 in the user plane 350 further includes a SDAP (Service Data Adaptation Protocol) sub-layer 356, which is responsible for mapping between QoS (Quality of Service) flows and data radio bearers (DRBs) to support diverse services. The radio protocol architecture in the user plane 350 at the L2 layer can include partial or full protocol sub-layers of the SDAP sub-layer 356, the PDCP sub-layer 354, the RLC sub-layer 353, and the MAC sub-layer 352 for the UE. Although not shown, the UE can also have several upper layers above the L2 layer 355, including a network layer (e.g., IP layer) that terminates at the P-GW on the network side and an application layer that terminates at the other end of the connection (e.g., a remote UE, a server, etc.).

[0204] As one embodiment, the radio protocol architecture in FIG. 3 is applicable to the first node in the present application.

[0205] As one embodiment, the radio protocol architecture in FIG. 3 is applicable to the second node in the present application.

[0206] As one embodiment, the radio protocol architecture in FIG. 3 is applicable to the third node in the present application.

[0207] As one embodiment, the first information in the present application is generated at the MAC 302 or the MAC 352.

[0208] As one embodiment, the first information in the present application is generated at the PHY 301 or the PHY 351.

[0209] As one embodiment, the uplink signal in the present application is generated at the PHY 301 or the PHY 351.

[0210] As one embodiment, the RRC signaling in the present application is generated at the RRC 306.

[0211] As one embodiment, the RRC sub-layer 306 in the L3 layer belongs to a higher layer.

[0212] Embodiment 4

[0213] Embodiment 4 illustrates a hardware module diagram of a communication device according to an embodiment of the application, as shown in FIG. 4. FIG. 4 is a block diagram of a first communication device 450 and a second communication device 410 in communication with each other in an access network.

[0214] The first communication device 450 includes a controller / processor 459, a memory 460, a data source 467, a transmit processor 468, a receive processor 456, a multi-antenna transmit processor 457, a multi-antenna receive processor 458, a transmitter / receiver 454, and an antenna 452.

[0215] The second communication device 410 includes a controller / processor 475, a memory 476, a data source 477, a receive processor 470, a transmit processor 416, a multi-antenna receive processor 472, a multi-antenna transmit processor 471, a transmitter / receiver 418, and an antenna 420.

[0216] In the transmission from the second communication device 410 to the first communication device 450, at the second communication device 410, upper layer packets from a core network or upper layer packets from a data source 477 are provided to a controller / processor 475. The core network and the data source 477 represent all protocol layers above the L2 layer. The controller / processor 475 implements the functionality of the L2 layer. In the transmission from the second communication device 410 to the first communication device 450, the controller / processor 475 provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations for the first communication device 450 based on various priority metrics. The controller / processor 475 is also responsible for retransmission of lost packets, and signaling to the first communication device 450. Transmit processor 416 and multiple antenna transmit processor 471 implement various signal processing functions for the LI layer (i.e., physical layer). The transmit processor 416 implements coding and interleaving to facilitate forward error correction (FEC) at the second communication device 410, and mapping of coded bits to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The multiple antenna transmit processor 471 performs digital spatial pre-coding of the coded and modulated symbols, including codebook-based and non-codebook-based pre-coding, and beamforming processing, generating one or more spatial streams. The transmit processor 416 then maps to each spatial stream to a subcarrier, multiplexes the stream with reference signals (e.g., pilot) in the time and / or frequency domain, and then performs an inverse fast Fourier transform (IFFT) to generate a time-domain multicarrier symbol stream for the physical channel. The multiple antenna transmit processor 471 then performs transmit analog pre-coding / beamforming operations on the time-domain multicarrier symbol stream. Each transmitter 418 converts the baseband multicarrier symbol stream provided by the multiple antenna transmit processor 471 into a radio frequency stream, and then provides the radio frequency stream to a different antenna 420.

[0217] In transmissions from the second communication device 410 to the first communication device 450, at the first communication device 450, each receiver 454 receives a signal through its respective antenna 452. Each receiver 454 recovers information modulated onto an RF carrier and provides the recovered information at baseband as a stream of symbols to a receive processor 456. The receive processor 456 and a multiple access receiver processor 458 implement various signal processing functions of the Ll layer. The multiple access receiver processor 458 performs receive analog precoding / beamforming operations on the baseband multiple carrier symbol stream from the receivers 454. The receive processor 456 converts the baseband multiple carrier symbol stream from the receive analog precoding / beamforming operations from the time domain to the frequency domain using a Fast Fourier Transform (FFT). In the frequency domain, the physical layer data signals and the reference signals are demultiplexed from the received signal by the receive processor 456, where the reference signals will be used for channel estimation, and the data signals are recovered after multiple access detection in the multiple access receiver processor 458 for any spatial streams destined for the first communication device 450. The symbols on each spatial stream are demodulated and recovered by the receive processor 456 and soft decisions are generated. The receive processor 456 then decodes and de-interleaves the soft decisions to recover the upper layer data and control signals transmitted by the second communication device 410 on the physical channel. The upper layer data and control signals are then provided to a controller / processor 459. The controller / processor 459 implements the functions of the L2 layer. The controller / processor 459 can be associated with a memory 460 that stores program codes and data. The memory 460 can be referred to as a computer readable medium. In transmissions from the second communication device 410 to the first communication device 450, the controller / processor 459 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer data packets from the second communication device 410. The upper layer data packets are then provided to all protocol layers above the L2 layer. Various control signals can also be provided to the L3 for L3 processing.

[0218] In the transmission from the first communication device 450 to the second communication device 410, at the first communication device 450, a data source 467 provides upper layer data packets to a controller / processor 459 using the data source 467. The data source 467 represents all protocol layers above the L2 layer. Similar to the transmit function at the second communication device 410 described in the transmission from the second communication device 410 to the first communication device 450, the controller / processor 459 implements header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels, L2 layer functionality for the user plane and control plane. The controller / processor 459 is also responsible for retransmission of lost packets, and signaling to the second communication device 410. Transmit processor 468 performs modulation mapping, channel coding processing, multi-antenna transmit processor 457 performs digital multi-antenna spatial precoding, including codebook-based precoding and non-codebook-based precoding, and beamforming processing, and then transmit processor 468 modulates the generated spatial streams into multi-carrier / single-carrier symbol streams, which are further processed by analog precoding / beamforming operations in multi-antenna transmit processor 457 and then provided to different antennas 452 via transmitters 454. Each transmitter 454 first converts the baseband symbol stream provided by multi-antenna transmit processor 457 into a radio frequency signal, and then provides the radio frequency signal to the antenna 452.

[0219] In the transmission from the first communication device 450 to the second communication device 410, the functions at the second communication device 410 are similar to the receive functions at the first communication device 450 described in the transmission from the second communication device 410 to the first communication device 450. Each receiver 418 receives a radio frequency signal through its respective antenna 420, converts the received radio frequency signal into a baseband signal, and provides the baseband signal to multi-antenna receive processor 472 and receive processor 470. The receive processor 470 and multi-antenna receive processor 472 collectively implement the functionality of the L1 layer. Controller / processor 475 implements the functionality of the L2 layer. Controller / processor 475 can be associated with a memory 476 that stores program codes and data. The memory 476 can be referred to as a computer readable medium. In the transmission from the first communication device 450 to the second communication device 410, the controller / processor 475 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer data packets from the first communication device 450. Upper layer data packets from the controller / processor 475 can be provided to the core network or all protocol layers above the L2 layer, and various control signals can be provided to the core network or L3 for L3 processing.

[0220] As one embodiment, the first communication device 450 apparatus comprises at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the first communication device 450 apparatus at least to monitor a first cell and individual candidate target cells of a set of candidate target cells, transmit first information to a network device in response to satisfying a first execution condition, the first execution condition comprising that a received signal strength of the first cell is not higher than a first threshold, handover to one of the candidate target cells in response to satisfying a second execution condition, the handover to one of the candidate target cells being dependent on the transmission of the first information, wherein the handover is a RACH-less LTM, and wherein the set of candidate target cells is pre-configured by the network device.

[0221] As one embodiment, the first communication device 450 apparatus comprises a memory storing a computer readable program of instructions which, when executed by at least one processor, causes actions comprising monitoring a first cell and individual candidate target cells of a set of candidate target cells, transmitting first information to a network device in response to satisfying a first execution condition, the first execution condition comprising that a received signal strength of the first cell is not higher than a first threshold, handover to one of the candidate target cells in response to satisfying a second execution condition, the handover to one of the candidate target cells being dependent on the transmission of the first information, wherein the handover is a RACH-less LTM, and wherein the set of candidate target cells is pre-configured by the network device.

[0222] As one embodiment, the second communication device 410 apparatus comprises at least one processor and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the second communication device 410 apparatus at least to receive first information, the first information being transmitted by a first node monitoring a first cell and individual candidate target cells of a set of candidate target cells and in response to satisfying a first execution condition, the first execution condition comprising that a received signal strength of the first cell is not higher than a first threshold, and to inform at least one of the candidate target cells of the set of candidate target cells to enable the first node to handover to one of the candidate target cells in response to satisfying a second execution condition, wherein the first node handover to one of the candidate target cells is dependent on the transmission of the first information, wherein the handover is a RACH-less LTM, and wherein the set of candidate target cells is pre-configured.

[0223] As one embodiment, the second communication device 410 apparatus comprises: a memory storing a computer readable program, the computer readable program, when executed by at least one processor, produces actions comprising: receiving first information, the first information being sent by a first node monitoring a first cell and each of a set of candidate target cells, and in response to satisfying a first execution condition, the first execution condition comprising: a signal strength of the first cell received by the first node being not higher than a first threshold; informing at least one of the set of candidate target cells to enable the first node to handover to one of the candidate target cells in response to satisfying a second execution condition; wherein the handover to one of the candidate target cells is dependent on the sending of the first information; the handover is LTM without RACH; and the set of candidate target cells is pre-configured.

[0224] As one embodiment, the second communication device 410 apparatus comprises: at least one processor and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the second communication device 410 apparatus at least: to receive informing information sent by a second node, the informing information comprising at least one of a set of candidate target cells pre-configured by the second node to a first node to enable the first node to monitor a first cell and each of the set of candidate target cells, and in response to satisfying a first execution condition, to send first information to the second node; wherein the first execution condition comprises: a signal strength of the first cell received being not higher than a first threshold; the first node to handover to one of the candidate target cells in response to satisfying a second execution condition; the handover to one of the candidate target cells is dependent on the sending of the first information; and the handover is LTM without RACH.

[0225] As an embodiment, the second communication device 410 comprises: a memory storing a computer readable program, the computer readable program, when executed by at least one processor, generates actions comprising: receiving a notification information from a second node, the notification information comprising at least one candidate target cell in a candidate target cell set, the candidate target cell set being pre-configured by the second node to the first node for the first node to monitor a first cell and each candidate target cell in the candidate target cell set, and sending a first information to the second node in response to satisfying a first execution condition; wherein the first execution condition comprises that a received signal strength of the first cell is not higher than a first threshold; the first node switches to one of the candidate target cells in response to satisfying a second execution condition; the switching to one of the candidate target cells is dependent on the sending of the first information; and the switching is a RACH-less LTM.

[0226] As an embodiment, the first communication device 450 corresponds to the first node in the present application.

[0227] As an embodiment, the second communication device 410 corresponds to the second node in the present application.

[0228] As an embodiment, the second communication device 410 corresponds to the third node in the present application.

[0229] As an embodiment, the first communication device 450 is a UE.

[0230] As an embodiment, the first communication device 450 is a relay.

[0231] As an embodiment, the second communication device 410 is a base station device.

[0232] As an embodiment, the second communication device 410 is a distributed unit of a base station.

[0233] As an embodiment, the second communication device 410 is a piece of code in a distributed unit of a base station.

[0234] As an embodiment, at least one of the antenna 452, the transmitter 454, the multi-antenna transmission processor 457, the transmission processor 468 or the controller / processor 459 is used to transmit the uplink signal in the present application.

[0235] As an embodiment, at least one of the antenna 420, the receiver 418, the multi-antenna reception processor 472, the reception processor 470 or the controller / processor 475 is used to receive the uplink signal in the present application.

[0236] As an embodiment, at least one of the antenna 420, the transmitter 418, the multi-antenna transmission processor 471, the transmission processor 416, or the controller / processor 475 is configured to transmit the first information in the present application.

[0237] As an embodiment, at least one of the antenna 452, the receiver 454, the multi-antenna reception processor 458, the reception processor 456, or the controller / processor 459 is configured to receive the first information in the present application.

[0238] As an embodiment, at least one of the antenna 420, the transmitter 418, the multi-antenna transmission processor 471, the transmission processor 416, or the controller / processor 475 is configured to transmit the RRC signaling in the present application.

[0239] As an embodiment, at least one of the antenna 452, the receiver 454, the multi-antenna reception processor 458, the reception processor 456, or the controller / processor 459 is configured to receive the RRC signaling in the present application.

[0240] Embodiment 5

[0241] Embodiment 5 illustrates a flow chart of wireless signal transmission according to an embodiment of the present application, as shown in FIG. 5. It is particularly noted that the sequence in this example does not limit the sequence of signal transmission and the sequence of implementation in the present application.

[0242] For the first node N51, the RRC signaling is received in step S511; each candidate target cell in the first cell and the set of candidate target cells is monitored in step S512; the first information is transmitted in step S513; in response to satisfying the second execution condition, the handover to one of the candidate target cells is performed in step S514; the DCI is received in step S515; and the uplink signal is transmitted in step S516.

[0243] For the second node N52, the RRC signaling is transmitted in step S521; the first information is received in step S522; and the signaling is exchanged with the third node N53 in step S531.

[0244] For the third node N53, the signaling is exchanged with the second node N52 in step S531; the DCI is transmitted in step S532; and the uplink signal is received in step S533.

[0245] In embodiment 5, the second node N52 transmits the RRC signaling to the first node N51 in step S521.

[0246] As one embodiment, the RRC signaling comprises a candidate target cell configuration IE (Information element).

[0247] As one embodiment, the RRC signaling configures a candidate cell configuration for a candidate target cell set.

[0248] As one embodiment, the RRC signaling configures a candidate target cell configuration for each candidate target cell in the candidate target cell set, each candidate target cell configuration being indicated by a configuration identity.

[0249] As one embodiment, the candidate target cell set is an LTM candidate target cell set.

[0250] As one embodiment, the candidate target cell configuration is an LTM candidate target cell configuration.

[0251] As one embodiment, the candidate target cell configuration is a partial or complete LTM candidate target cell configuration.

[0252] As one embodiment, the RRC signaling is an RRCReconfiguration (RRC reconfiguration, or condRRCReconfig (conditional RRC reconfiguration); or ltm-ReferenceConfiguration (LTM reference configuration).

[0253] As one embodiment, the RRC signaling comprises an LTM-Candidate (LTM candidate); or the RRC signaling comprises an ltm-CandidateConfig (LTM candidate configuration); or the RRC signaling comprises an ltm-CandidateConfig which is a complete LTM candidate cell configuration configured for the LTM candidate target cell set.

[0254] As one embodiment, the RRC signaling comprises an ltm-ReferenceConfiguration and the ltm-CandidateConfig to generate a complete LTM candidate target cell configuration and configure it to the LTM candidate target cell set.

[0255] As one embodiment, the candidate target cell set is configured according to a measurement report reported by the first node N51.

[0256] As one embodiment, the candidate target cell set is configured by the second node N52, which is configured by a base station of the first cell.

[0257] As one embodiment, the second cell belongs to the candidate target cell set.

[0258] As one embodiment, the candidate target cell is used for cell switch.

[0259] As one embodiment, the candidate target cell is used for LTM.

[0260] As one embodiment, the RRC signaling indicates the second cell. In one implementation, the second cell is identified by a PhysCellld (Physical Cell ld). Alternatively, the second cell is identified by a candidateCellld (candidate target cell ld).

[0261] As one embodiment, the RRC signaling configures the candidate target cell configuration for the second cell.

[0262] As one embodiment, the second cell is any cell in a candidate target cell set configured to the first node N51; wherein the candidate target cell set configured to the first node N51 comprises at least one cell.

[0263] As one embodiment, the base station of the first cell and the base station of the candidate target cell are the same base station.

[0264] As one embodiment, the base station of the first cell and the base station of the candidate target cell are different base stations.

[0265] As one embodiment, the candidate target cell is a candidate target cell of the first node.

[0266] As one embodiment, the candidate target cell is an LTM candidate target cell of the first node N51.

[0267] As one embodiment, the evaluating whether the first execution condition is satisfied comprises performing channel measurement to evaluate signal strength for each candidate target cell in the candidate target cell set; wherein the third node N53 is a base station of any candidate target cell in the candidate target cell set.

[0268] As one embodiment, after receiving the RRC signaling and before determining that the first execution condition is satisfied, the first node is in an RRC connected (RRC_connected) state.

[0269] As one embodiment, the first RRC signaling indicates the first threshold.

[0270] As an embodiment, the first RRC signaling comprises the first threshold value, or comprises the second threshold value, or comprises both the first threshold value and the second threshold value.

[0271] As an embodiment, the RRC signaling indicates the first execution condition, or indicates the second execution condition, or indicates both the first execution condition and the second execution condition.

[0272] As a variant embodiment, the first execution condition and the second execution condition are issued by different RRC signaling.

[0273] As an embodiment, the RRC signaling configures an event in which the conditional LTM is executed.

[0274] As an embodiment, after the RRC signaling is received, the configuration of each candidate target cell comprised therein is stored.

[0275] As an embodiment, the RRC signaling further comprises the first threshold value, the second threshold value, and / or the third threshold value.

[0276] As another embodiment, the first threshold value is issued by other RRC signaling and is received and stored by the first node N51. Alternatively, one or more of the first threshold value, the second threshold value, and / or the third threshold value are issued by other RRC signaling; or, the first threshold value, the second threshold value, and / or the third threshold value are issued by other different RRC signaling. Then, they are received and stored by the first node N51.

[0277] In an embodiment, the RRC signaling comprises the set of candidate target cells and is configured to the first node N51. The configuration information of the candidate target cell can comprise one or more of the following: cell identity of the candidate target cell; cell offset of the candidate target cell; transmission power of the candidate target cell.

[0278] In a specific implementation, the step S511 and the step S512 can be executed in parallel, sequentially, or the step S512 is executed first and the step S511 is executed second.

[0279] In a specific implementation, the first node N51 receives the RRC signaling in the step S511. After receiving the RRC signaling, the first node N51 stores the configuration information in the RRC signaling. In the step S512, the first node N51 monitors the first cell and each candidate target cell in the set of candidate target cells.

[0280] As an embodiment, before the first execution condition is met, the candidate target cell configuration included in the RRC signaling is not applied.

[0281] In a specific implementation, the first node N51 can be in an RRC connected state. The first node N51 monitors the first cell to obtain the signal strength of the first cell, for example, monitors the reference signal (RS) of the base station second node N52 of the first cell, such as SSB and / or CSI-RS.

[0282] As an embodiment, the signal strength of the first cell can be the channel quality of the first cell, or the signal strength of a reference signal resource, a beam, etc. of the first cell. The monitoring of the first cell can be a measurement of the first cell, which is an L3 measurement.

[0283] In a specific implementation, the first node N51 can measure the RS of the second node N52, and can also measure the RS of each candidate target cell in the candidate target cell set to obtain the signal strength of the first cell and each candidate target cell. For example, SSB or CSI-RS is measured to obtain the signal strength of each cell.

[0284] As an embodiment, the first threshold is a cell-level measurement result, and the second threshold is a beam-level measurement result. In an implementation, the first threshold can be an L3 threshold, and the second threshold can be an L1 threshold. In another implementation, the first threshold is for multiple RS resources, and the second threshold is for one RS resource.

[0285] In an embodiment, the signal strength received by the first node N51 is lower than or equal to the first threshold. For example, the signal strength or channel quality obtained by measuring SSB or CSI-RS is lower than or equal to the first threshold. At this time, the first execution condition is met.

[0286] If the first execution condition is met, in step S513, the first node N51 sends the first information to the second node N52. The first information can indicate that the received signal strength is not higher than the first threshold.

[0287] In one embodiment, the first information can indicate that the received signal strength of the first cell is not higher than a first threshold; or, the first information can indicate that the received signal strength of the first cell is not higher than a first threshold and the received signal strength of at least one of the candidate target cells is higher than the first threshold; or, the first information can indicate that the received signal strength of the first cell is not higher than a first threshold and the received signal strength of at least one of the candidate target cells is higher than a third threshold, the third threshold being higher than the first threshold.

[0288] Depending on the sending of the first information, the first node N51 will perform a RACH-less conditional LTM handover; or, depending on the sending of the first information, the first node N51 will have a high probability to perform a RACH-less conditional LTM handover.

[0289] As one embodiment, depending on the satisfaction of the first execution condition, the first node N51 acquires the timing advance of the target cell after handover.

[0290] As one embodiment, when the base station of the first cell and the base station of the candidate target cell are different base stations, the timing advance is acquired at the base station of one of the candidate target cells, then forwarded to the base station of the first cell through a backhaul network, and sent to the first node through the first cell. This method can reduce the communication interruption time with the first cell by not receiving the timing advance command at the second cell. Here, the backhaul network is ideal. Or, the backhaul network is non-ideal.

[0291] For example, the timing advance is obtained at the third node N53, then forwarded to the second node N52 through a backhaul network, and sent to the first node N51, at this time the first node N51 acquires the timing advance.

[0292] After step S512, the first node N51 selects one or more appropriate candidate target cells, and sends the first information in step S513.

[0293] In one embodiment, the first information can indicate a RACH-less conditional LTM cell handover. For example, the first information includes 1 bit to indicate whether a RACH-less conditional LTM cell handover. When indicating a RACH-less conditional LTM handover, the second node N52 receiving the first information can know that the first node N51 satisfies the first execution condition.

[0294] Then, the second node N52 receives the first information in step S522. After that, the second node N52 performs step S531 with the third node N53, and interacts signaling. In a specific implementation, the signaling interaction includes that the second node N52 sends notification information to the third node N53, to notify at least one candidate target cell in the candidate target cell set, so that the first node N51 can switch to one of the candidate target cells in response to satisfying a second execution condition. The notification information can include at least one candidate target cell in the candidate target cell set. For example, the at least one candidate target cell can be the ID of each candidate target cell. The at least one candidate target cell can be obtained by the first node through the first information. It should be noted that step S531 is an inter-cell signaling interaction.

[0295] In a specific implementation, the switching to one of the candidate target cells depends on the sending of the first information.

[0296] Preferably, the at least one candidate target cell is only one candidate target cell. The signal strength or channel quality of the only one candidate target cell is the best in the candidate target cell set; or the signal strength or channel quality of the only one candidate target cell is a candidate target cell satisfying a certain preset threshold.

[0297] After receiving the notification information sent by the second node N52, the third node N53 will reserve resources for the first node N51, so that the first node N51 can perform RACH-free conditional LTM cell switching to the candidate target cell to which the third node N53 belongs. The candidate target cell to which the third node N53 belongs is one of the at least one candidate target cell reported by the first node N51.

[0298] In one embodiment, the third node N53 will perform signaling interaction with the second node N52 to prepare to complete the conditional LTM of the first node N51.

[0299] In a specific implementation, the third node N53 can send a PDCCH. For example, a DCI is sent in step S532, and the DCI includes resource configuration information, such as an uplink grant (UL grant).

[0300] During this period, the first node N51 can continue to judge the signal strength of the first cell and / or the second cell after step S513. In step S514, in response to satisfying the second execution condition, the first node N51 switches to one of the candidate target cells.

[0301] As an embodiment, the second execution condition is satisfied when the received signal strength of the first cell is not higher than a second threshold. Alternatively, the second execution condition is satisfied when the signal strength of at least one candidate target cell is not lower than a third threshold. Alternatively, the second execution condition is satisfied when the received signal strength of the first cell is not higher than a second threshold and the signal strength of at least one candidate target cell is not lower than a third threshold.

[0302] In a specific implementation, the second threshold is not higher than the first threshold; and the third threshold is higher than the first threshold.

[0303] As an embodiment, the first node switches to one of the candidate target cells in response to the second execution condition being satisfied; and the switching to one of the candidate target cells is dependent on the sending of the first information.

[0304] As an embodiment, the switching to one of the candidate target cells in dependent on the sending of the first information means that the sending of the first information triggers the first node to switch to one of the candidate target cells. If the first information is not sent, the first node will not perform the switching.

[0305] As an embodiment, the switching to one of the candidate target cells in dependent on the sending of the first information means that the time interval between the sending of the first information and the switching is very small.

[0306] As an embodiment, the switching to one of the candidate target cells in dependent on the sending of the first information means that after the sending of the first information, the second execution condition set is evaluated to determine whether the switching is performed.

[0307] As an embodiment, the switching to one of the candidate target cells in dependent on the sending of the first information means that a timer is started when the first information is sent, and the cell after the switching is detected when the timer expires. For example, the uplink grant is detected to obtain the uplink resource.

[0308] As an embodiment, after the first execution condition is satisfied, the first node N51 can perform uplink synchronization with one of the at least one candidate target cell. Preferably, the first information carries one of the candidate target cells, and the first node N51 autonomously acquires the timing advance of the candidate target cell to complete the uplink synchronization.

[0309] In the embodiment, the first node N51 configures multiple execution conditions, and after the first execution condition is reached, the first node N51 sends the first information to the serving cell (for example, the first cell). After the serving cell receives the first information, the resources of the target cell or the candidate target cell can be activated through inter-cell signaling interaction, so that the UE autonomous LTM handover is quickly completed, and resources are saved.

[0310] In the implementation, the first node N51 can configure the first threshold, the second threshold, and / or the third threshold. After the first threshold configured by the RRC is met, the first node N51 sends the first information to the serving cell, and after the serving cell receives the first information, the resources of the target cell or the candidate target cell are activated, so that the handover is completed, and resources are saved.

[0311] In step S515, the first node N51 receives the DCI. In the implementation, the first node N51 detects the post-handover cell to receive the resource configuration information carried by the DCI.

[0312] As an embodiment, the detection of the post-handover cell includes that the first node N51 performs the LTM handover to the post-handover cell by itself.

[0313] As an embodiment, the detection of the post-handover cell includes that the first node N51 performs the handover of the layer below the layer three to the post-handover cell by itself.

[0314] As an embodiment, the detection of the post-handover cell includes that the RRC configuration for the first cell is released.

[0315] As an embodiment, the detection of the post-handover cell includes that the L2 of the first node N51 is reset.

[0316] In step S516, the first node N51 sends the uplink signal. In the implementation, after the first node N51 receives the resource configuration information carried by the DCI sent by the third node N53, the first node N51 sends the uplink signal in the cell to which the third node N53 belongs based on the resource configuration information. The PUSCH signal can be sent, or the PUCCH signal can be sent. Correspondingly, the third node N53 receives the uplink signal in step S533.

[0317] For more information about the working principle and working mode of FIG. 5, please refer to the above description of the technical solutions shown in FIG. 1.

[0318] Embodiment 6

[0319] FIG. 6 illustrates a part of the steps in the handover method flow in the first node according to the embodiment of the application.

[0320] In combination with FIG. 5, after the first node N51 determines that the first execution condition is satisfied in step S512 and sends the first information in step S513, the first node N51 performs step S601. In step S601, the first node N51 evaluates whether the second execution condition is satisfied.

[0321] In one embodiment, the first node N51 does not satisfy the second execution condition, and the first node performs step S602 to send second information to the node N52.

[0322] In one embodiment, the second information indicates that the second execution condition is not satisfied. At this time, the candidate target cell can release the resources reserved for the first node N51 to save resources.

[0323] In another embodiment, the second information indicates to stop the handover. At this time, the candidate target cell can release the resources reserved for the first node N51 to save resources.

[0324] As an embodiment, whether to evaluate whether the second execution condition is satisfied depends on whether the first information is sent by the first node.

[0325] As a variant embodiment, whether to evaluate whether the second execution condition is satisfied depends on whether the first execution condition is satisfied. If the first execution condition is not satisfied, the first node does not send the first information and does not evaluate the second execution condition information.

[0326] As an embodiment, depending on the satisfaction of the first execution condition, the first node can obtain the timing advance of the target cell after the handover.

[0327] As a variant embodiment, when the first execution condition is not satisfied, it is not required to obtain the timing advance of the first cell.

[0328] As an embodiment, after the first information is sent, the first node can obtain the timing advance of the at least one candidate target cell.

[0329] As an embodiment, the first node synchronizes uplink to one of the candidate target cells before the handover to the candidate target cell.

[0330] In implementation, in the process of performing uplink synchronization for each candidate cell, if the RRC reconfiguration information indicates that the timing advance is measured by the terminal device itself, the terminal device can measure the timing advance of the source cell, and determine the timing advance of the candidate cell according to the time difference in receiving the source cell and the candidate cell; or, the source cell triggers CFRA through PDCCH order to obtain the timing advance of the candidate cell, the terminal device initiates CFRA to the candidate cell to obtain the timing advance of the candidate cell, and the source cell determines the validity of the timing advance.

[0331] Embodiment 7

[0332] FIG. 7 illustrates a part of the flow of the handover method in the first node according to an embodiment of the present application.

[0333] In combination with FIG. 5, after step S512, the first node N51 determines that the first execution condition is not met.

[0334] As an embodiment, the first node N51 performs step S701, and sends the second information. The second information sent to the second node N52 indicates that the first execution condition is not met.

[0335] As an embodiment, the second information indicates that the received signal strength of the first cell is higher than a first threshold.

[0336] In implementation, after sending the second information, the evaluation of whether the second execution condition is met is stopped.

[0337] In implementation, the second information is carried by high-layer signaling, for example, RRC signaling; or, the second information is carried by L3 below signaling. For example, MAC CE or physical layer signaling.

[0338] Embodiment 8

[0339] FIG. 8 illustrates a diagram of detecting the post-handover cell according to an embodiment of the present application.

[0340] As an embodiment, the first node starts a timer when sending the first information in step S801, and detects the post-handover cell after the expiration of the timer in S802.

[0341] As an embodiment, the post-handover cell is detected when the timer expires only when the second execution condition is met.

[0342] As an embodiment, starting the timer comprises: setting the value of the timer to an initial value; wherein the initial value is 0, or the initial value is a preset expiration value.

[0343] As an embodiment, the preset expiration value is preconfigured.

[0344] As an embodiment, the preset expiration value is configured by network.

[0345] As an embodiment, the preset expiration value is used to determine expiration of the timer.

[0346] As an embodiment, the timer is started in running state.

[0347] As an embodiment, the timer is maintained in higher layer. The higher layer is RRC layer, or the higher layer is MAC layer.

[0348] As an embodiment, the sending time of the first information is earlier than the starting time of the timer.

[0349] As an embodiment, the timer is used to detect the cell after the handover.

[0350] As an embodiment, the timer is stopped after the cell handover is successful. In other words, when the timer expires, the cell handover has been completed.

[0351] As an embodiment, when the timer expires, the first node starts to blindly detect the cell after the handover.

[0352] As an embodiment, if the cell handover is aborted, the timer is stopped.

[0353] As an embodiment, when the HARQ is received at the third node, it is determined that the uplink signal is successfully received by the three nodes.

[0354] As an embodiment, the initial value of the timer is 0, and updating the timer is to add 1 to the value of the timer; when the value of the timer is a preset expiration value, the timer expires, and the timer is reset to 0.

[0355] As an embodiment, the initial value of the timer is a preset expiration value, and updating the timer is to subtract 1 from the value of the timer; when the value of the timer is 0, the timer expires. The timer is reset to the preset expiration value.

[0356] As an embodiment, when the timer is running, the timer is updated at each time interval. Each time interval is 1 millisecond; or the time length included in 1 slot.

[0357] As an embodiment, when the timer is running, if the stop condition of the timer is met, the timer is stopped.

[0358] Embodiment 9

[0359] Embodiment 9 illustrates a structure block diagram of a processing device in a first node according to an embodiment of the present application, as shown in FIG. 9. In FIG. 9, the first node processing device 900 includes a first processor 901 and a second processor 902; the first node 900 is a UE. In a specific implementation, the first processor 901 and the second processor 902 can be the same processing module, or can be different processing modules.

[0360] In embodiment 9, the first node processing device 900 includes: the first processor 901, monitoring a first cell and a candidate target cell in a candidate target cell set, sending first information as a response to satisfying a first execution condition, the first execution condition including: the signal strength of the first cell is not higher than a first threshold; the second processor 902, switching to one of the candidate target cells as a response to satisfying a second execution condition; the switching to one of the candidate target cells depends on the sending of the first information; wherein the switching is LTM without RACH; the candidate target cell set is pre-configured.

[0361] As an embodiment, the monitoring the first cell and the candidate target cell in the candidate target cell set includes monitoring at least one candidate target cell in the candidate target cell set.

[0362] As an embodiment, the monitoring the first cell and the candidate target cell in the candidate target cell set includes monitoring each candidate target cell in the candidate target cell set.

[0363] As an embodiment, the monitoring the first cell and the candidate target cell in the candidate target cell set includes measuring the signal strength of the first cell.

[0364] As an embodiment, the monitoring the first cell and the candidate target cell in the candidate target cell set includes measuring the signal strength of the candidate cell in the candidate target cell set.

[0365] As an embodiment, the first information carries at least one candidate target cell in the candidate target cell set.

[0366] As an embodiment, the first processor 901 can start a timer when sending the first information, and detect a cell after switching when the timer runs out.

[0367] In one embodiment, the first processor 901 can receive resource configuration information sent by the cell after the handover, and send uplink signals on the cell after the handover based on the resource configuration information.

[0368] In a specific implementation, the signal strength of the first cell can be at least one of the following: a measurement result of a reference signal; a signal strength of a signal other than the reference signal; a signal strength of a signal other than the reference signal, and the signal strength of the other signal is not higher than the first threshold in a preset time interval.

[0369] In one embodiment, the candidate target cell set can be pre-configured by RRC signaling; and the configuration information of the candidate target cell includes one or more of the following: a cell identifier of the candidate target cell; a cell offset of the candidate target cell; and a transmission power of the candidate target cell.

[0370] As an embodiment, the first processor 901 can obtain the timing advance of the target cell after the handover in dependence on the first execution condition being met.

[0371] As an embodiment, the first processor 901 includes at least one of the receiver 454 (including the antenna 452), the receiving processor 456, the multi-antenna receiving processor 458, and the controller / processor 459 in FIG. 4.

[0372] As an embodiment, the first processor 901 includes at least one of the receiver 454 (including the antenna 452), the receiving processor 456, the multi-antenna receiving processor 458, or the controller / processor 459 in FIG. 4.

[0373] As an embodiment, the second processor 902 includes at least one of the receiver 454 (including the antenna 452), the receiving processor 456, the multi-antenna receiving processor 458, and the controller / processor 459 in FIG. 4.

[0374] As an embodiment, the second processor 902 includes at least one of the receiver 454 (including the antenna 452), the receiving processor 456, the multi-antenna receiving processor 458, or the controller / processor 459 in FIG. 4.

[0375] For more details about the working principle and working mode of the first node processing device 900, please refer to the above descriptions of the technical solutions shown in FIGS. 1 to 7.

[0376] Embodiment 10

[0377] Embodiment 10 illustrates a structure block diagram of a processing device in a second node according to an embodiment of the present application, as shown in FIG. 10. In FIG. 10, the first node processing device 1000 includes a first receiver 1001 and a first processor 1002; the second node 1000 is a network device, such as a NR base station. The first receiver 1001 and the first processor 1002 can be the same processing module or different processing modules.

[0378] In Embodiment 10, the first node processing device 1000 includes: the first receiver 1001 can receive first information, the first information is that the first node monitors a first cell and a candidate target cell set in a candidate target cell, and is sent as a response to satisfying a first execution condition, the first execution condition includes: the signal strength of the first cell measured by the first node is not higher than a first threshold; the first processor 1002 notifies at least one candidate target cell in the candidate target cell set, so that the first node switches to one of the candidate target cells in response to satisfying a second execution condition; wherein the first node switching to one of the candidate target cells depends on the sending of the first information; the switching is LTM without RACH; the candidate target cell set is pre-configured.

[0379] As an embodiment, the first information carries at least one candidate target cell in the candidate target cell set.

[0380] As an embodiment, the received signal strength of the first cell can be at least one of: a measurement result of a reference signal; a signal strength of a signal other than the reference signal; a signal strength of a signal other than the reference signal, and within a preset time interval, the signal strength of the other signal is not higher than the first threshold.

[0381] As an embodiment, the candidate target cell set is pre-configured by RRC signaling; the configuration information of the candidate target cell can include one or more of: a cell identifier of the candidate target cell; a cell offset of the candidate target cell; a transmission power of the candidate target cell.

[0382] As an embodiment, the first receiver 1001 includes at least one of the receiver 418 (including the antenna 420), the reception processor 470, the multi-antenna reception processor 472, and the controller / processor 475 in FIG. 4 of the present application.

[0383] As an embodiment, the first receiver 1001 includes at least one of the receiver 418 (including the antenna 420), the reception processor 470, the multi-antenna reception processor 472, or the controller / processor 475 in FIG. 4 of the present application.

[0384] As one embodiment, the first processor 1002 includes at least one of the transmitter 418 (including the antenna 420), the transmit processor 416, the multi-antenna transmit processor 471, or the controller / processor 475 in FIG. 4 of the present application.

[0385] As one embodiment, the first processor 1002 includes at least one of the transmitter 418 (including the antenna 420), the transmit processor 416, the multi-antenna transmit processor 471, or the controller / processor 475 in FIG. 4 of the present application.

[0386] For more details about the working principle and working mode of the second node processing device 1000, please refer to the related description of the technical solutions shown in FIGS. 1 to 7 above, which will not be repeated here.

[0387] Embodiment 11

[0388] Embodiment 11 illustrates a structural block diagram of a processing device in a third node according to an embodiment of the present application, as shown in FIG. 11. In FIG. 11, the third node processing device 1100 includes a first receiver 1101; the third node processing device 1100 is a network device, such as an NR base station.

[0389] In specific implementation, the third node processing device 1100 can include: the first receiver 1101 can receive the notification information sent by the second node, the notification information including at least one candidate target cell in a candidate target cell set, the candidate target cell set being pre-configured by the second node to the first node, so that the first node monitors the first cell and the candidate target cell in the candidate target cell set, and sends the first information to the second node as a response to the first execution condition; wherein the first execution condition includes: the signal strength of the first cell is not higher than the first threshold; the first node switches to one of the candidate target cells in response to the second execution condition; the switching to one of the candidate target cells depends on the sending of the first information; and the switching is LTM without RACH.

[0390] As one embodiment, the first receiver 1101 includes at least one of the receiver 418 (including the antenna 420), the receive processor 470, the multi-antenna receive processor 472, or the controller / processor 475 in FIG. 4 of the present application.

[0391] As one embodiment, the first receiver 1101 includes at least one of the receiver 418 (including the antenna 420), the receive processor 470, the multi-antenna receive processor 472, or the controller / processor 475 in FIG. 4 of the present application.

[0392] More details about the working principle and working mode of the third node processing device 1100 can be referred to the related descriptions of the technical solutions shown in FIG. 1 to FIG. 7.

[0393] Those skilled in the art can understand that all or part of the steps of the above method can be instructed by a program to complete the relevant hardware, and the program can be stored in a computer readable storage medium, such as a read-only memory, a hard disk, or an optical disk. Optionally, all or part of the steps of the above embodiment can also be implemented using one or more integrated circuits. Correspondingly, each module unit in the above embodiment can be implemented in the form of hardware or in the form of a software function module, and the present application is not limited to any specific form of combination of software and hardware. The first type of communication node or UE or terminal in the present application includes but is not limited to a mobile phone, a tablet computer, a notebook computer, a network card, a low-power device, an eMTC (enhanced Machine Type Communication) device, an NB-IoT device, a vehicle-mounted communication device, a flying vehicle, an airplane, a drone, a remote control airplane, and other wireless communication devices. The second type of communication node or base station or network side device in the present application includes but is not limited to a macro cellular base station, a micro cellular base station, a home base station, a relay base station, an eNB, a gNB, a transmission and reception point (TRP), a relay satellite, a satellite base station, an air base station, and other wireless communication devices.

[0394] The above describes only the preferred embodiments of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A first node for cell handover, characterized by, Comprising: a first processor, monitoring a first cell and candidate target cells in a candidate target cell set, and sending first information in response to satisfying a first execution condition, wherein the first execution condition comprises that a signal strength of the first cell is not higher than a first threshold; a second processor, switching to one of the candidate target cells in response to satisfying a second execution condition; the switching to one of the candidate target cells is dependent on the sending of the first information; wherein the switching is LTM without RACH; and the candidate target cell set is pre-configured.

2. The first node of claim 1, wherein: the first information indicates at least one of the candidate target cells in the candidate target cell set.

3. The first node of claim 1 or 2, wherein: the first processor starts a timer when sending the first information, and detects a cell after switching when the timer expires.

4. The first node of claim 3, wherein, Comprising: the first processor receives resource configuration information sent by the cell after switching, and sends an uplink signal on the cell after switching based on the resource configuration information.

5. The first node of any one of claims 1 to 4, wherein: the signal strength of the first cell is at least one of: a measurement result of a reference signal; a signal strength of a signal other than the reference signal; a signal strength of a signal other than the reference signal, and the signal strength of the other signal is not higher than the first threshold within a preset time interval.

6. The first node of any one of claims 1 to 5, wherein, the candidate target cell set is pre-configured by RRC signaling; and the configuration information of the candidate target cell comprises one or more of: a cell identity of the candidate target cell; a cell offset of the candidate target cell; a transmission power of the candidate target cell.

7. The first node of any one of claims 1 to 6, wherein: the first processor acquires a timing advance of the cell after switching in dependence on satisfying the first execution condition. 8.A second node for cell handover, characterized in that, Comprising: a first transceiver, receiving first information sent by a first node in response to monitoring a first cell and candidate target cells in a candidate target cell set and satisfying a first execution condition, wherein the first execution condition comprises that a signal strength of the first cell is not higher than a first threshold; a first processor, notifying at least one of the candidate target cells in the candidate target cell set, so that the first node switches to one of the candidate target cells in response to satisfying a second execution condition; wherein the first node switches to one of the candidate target cells in dependence on the sending of the first information; the switching is LTM without RACH; and the candidate target cell set is pre-configured.

9. A method in a first node for cell handover, characterized by, Comprising: monitoring a first cell and candidate target cells in a candidate target cell set, and sending first information in response to satisfying a first execution condition, wherein the first execution condition comprises that a signal strength of the first cell is not higher than a first threshold; in response to satisfying a second execution condition, switching to one of the candidate target cells; the switching to one of the candidate target cells is dependent on the sending of the first information; wherein the switching is a non-RACH based LTM; and the set of candidate target cells is pre-configured.

10. A method in a second node for cell handover, characterized by, comprising: receiving first information, the first information being sent by a first node in response to satisfying a first execution condition, the first execution condition comprising: a signal strength of a first cell received by the first node being no higher than a first threshold; informing at least one of the set of candidate target cells, so that the first node switches to one of the candidate target cells in response to satisfying a second execution condition; wherein the first node switches to one of the candidate target cells is dependent on the sending of the first information; the switching is a non-RACH based LTM; and the set of candidate target cells is pre-configured.

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