Synchronization method and user equipment

Abstract

Provided in the present invention are a synchronization method and a user equipment. The synchronization method comprises: associating a synchronization timer with each PDU cluster or PDU set to be synchronized, wherein the value of the timer is configured by a base station for a UE by means of an RRC message or provided by an upper layer; the UE maintaining the synchronization timer to achieve multi-modal data synchronization; and when the base station configures the value of the synchronization timer, the base station separately configuring the value of the timer for each group of data flows requiring synchronization, and when the upper layer provides the value of the synchronization timer, the base station configuring an indication identifier for the UE, wherein the indication identifier is used for indicating whether the UE is allowed to start or run the synchronization timer or whether inter-PDU-set synchronization or multi-modal data synchronization is supported.

Description

Synchronization method and user equipment TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, and more particularly, to a synchronization method and a user equipment. BACKGROUND

[0002] Currently, one of the research targets in 3GPP in Release 19 for eXtended Reality (XR) is to improve the efficient support for XR applications with multi-modal inter-dependencies of multiple QoS flows, to meet multi-modal QoS requirements such as synchronization and / or coordination, see also TR 22.847, TR 23.70060. It is expected that the efficiency will be obvious in terms of capacity or power consumption. The related potential impacts are as follows: a) enhance the awareness of the RAN through signaling from the core network and / or UE indication, b) enhance the user plane, such as scheduling, logical channel priority LCP, resource allocation, packet discard, and the like.

[0003] The present application discusses related issues involved in multi-modal synchronization and / or coordination. SUMMARY

[0004] In order to solve at least part of the above problems, the present application provides a synchronization method and a user equipment.

[0005] According to a first aspect of the present application, a synchronization method is provided, comprising: associating a synchronization timer with each synchronization PDU cluster or PDU set, the value of the timer being configured for the UE by the base station through an RRC message or provided by the upper layer; the UE implements multi-modal data synchronization by maintaining the synchronization timer; in the case where the value of the synchronization timer is configured by the base station, the base station respectively configures the value of the timer for each group of data flows that need to be synchronized, and in the case where the value of the synchronization timer is provided by the upper layer, the base station configures an indication identifier for the UE, the indication identifier being used to indicate whether the UE is allowed to start or run the synchronization timer or whether the inter-PDU set synchronization or multi-modal data synchronization is supported.

[0006] In the synchronization method of the above first aspect, based on the mapping relationship between the QoS flow and the DRB, the synchronization timer runs at the SDAP layer or the PDCP layer or the RLC layer.

[0007] In the synchronization method of the first aspect, when submitting a PDCP PDU to the lower layer, or when receiving an indication of successful submission of a PDCP PDU or PDCP SDU from the lower layer, or when receiving an indication that a PDCP PDU or PDCP SDU has been transmitted from the lower layer, or when receiving an indication that a PDCP PDU or PDCP SDU has been successfully transmitted from the lower layer, the transmitting PDCP entity performs at least one of operations 1-1 to 1-3 if the UE or the PDCP entity is configured for multi-mode data synchronization and / or the PDCP PDU belongs to a synchronization PDU cluster and / or the PDCP PDU belongs to a PDU set.

[0008] In the synchronization method of the first aspect, the operations 1-1 to 1-3 are respectively:

[0009] Operation 1-1: if a synchronization timer associated with a synchronization PDU cluster to which the PDCP PDU or PDCP SDU belongs is not running, or if a synchronization timer associated with a PDU set that has a synchronization relationship with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, or if a synchronization timer associated with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, then starting the synchronization timer;

[0010] Operation 1-2: if the PDCP PDU or PDCP SDU is the first PDCP PDU or PDCP SDU of the PDU set to which it belongs, and / or if a synchronization timer is configured, and / or a synchronization timer associated with a synchronization PDU cluster to which the PDCP PDU or PDCP SDU belongs is not running or a synchronization timer associated with a PDU set that has a synchronization relationship with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, and / or a synchronization timer associated with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, then: (1) if a synchronization timer of the PDU set or synchronization PDU cluster to which the PDCP PDU or PDCP SDU belongs is running, then stopping the synchronization timer, and / or (2) starting the synchronization timer, and / or (3) indicating the submission information to the upper layer so that the upper layer starts a timer associated with the PDU set or synchronization PDU cluster upon receiving the indication;

[0011] The operation 1-3: If the PDCP PDU or PDCP SDU is the last PDCP PDU or PDCP SDU of its associated PDU set or associated synchronous PDU set group that is submitted to lower layer, or if the PDCP PDU or PDCP SDU is the first PDCP PDU or PDCP SDU of its associated PDU set that is submitted to lower layer, or if the PDCP PDU or PDCP SDU is the last PDCP PDU or PDCP SDU of its associated PDU set or associated synchronous PDU set group that is successfully transmitted by lower layer, the synchronous timer associated with the PDU set or the synchronous PDU set group is stopped, or the submission is indicated to upper layer.

[0012] In the synchronization method of the first aspect, the PDCP entity stops the synchronous timer associated with the PDU set or the synchronous PDU set group upon receiving an indication of successful submission or transmission of the last PDCP PDU or PDCP SDU of the PDU set or the synchronous PDU set group from lower layer.

[0013] In the synchronization method of the first aspect, the indication of successful submission or transmission of the PDCP PDU or PDCP SDU can be from MAC or RLC layer.

[0014] In the synchronization method of the first aspect, in case of expiry of discard timer of a PDCP SDU or expiry of low importance discard timer or expiry of synchronous timer, the transmitting PDCP entity performs at least one of the following operations:

[0015] Operation 2-1 : If pdu-SetDiscard is configured, then: (la) discard all PDCP SDUs and corresponding PDCP Data PDUs belonging to the PDU Set to which the PDCP SDU belongs, and / or (2a) if interPdu-setDiscard is configured or the synchronization timer expires, discard all PDCP SDUs and corresponding PDCP Data PDUs belonging to the synchronization PDU Set group to which the PDCP SDU belongs, and / or (3a) if interPdu-setDiscard is configured or if the PDCP SDU belongs to a synchronization PDU Set group or if the synchronization timer expires, discard all PDCP SDUs and corresponding PDCP Data PDUs belonging to the synchronization PDU Set group to which the PDCP SDU belongs, and / or (4a) if interPdu-setDiscard is configured and / or if the PDCP SDU belongs to a synchronization PDU Set group, indicate the discard to upper layers, and / or (5a) if interPdu-setDiscard is configured and / or if the PDCP SDU belongs to a PDU Set of a synchronization PDU Set group or to a synchronization PDU Set group and / or if there is a PDU Set in synchronization relationship with the PDU Set to which the PDCP SDU belongs, stop the synchronization timer associated with the PDU Set to which the PDCP SDU belongs or the synchronization PDU Set group or the PDU Set in synchronization relationship with the PDU Set to which the PDCP SDU belongs;

[0016] Operation 2-2: If interPdu-setDiscard is configured and / or a synchronization timer is configured and / or the PDCP SDU belongs to a PDU set or a synchronization PDU set group and / or there is a synchronization relationship with the PDU set to which the PDCP SDU belongs, then: (1b) discard all PDCP SDUs and corresponding PDCP data PDUs belonging to the PDU set to which the PDCP SDU belongs, and / or (2b) discard all PDCP SDUs and corresponding PDCP data PDUs belonging to the synchronization PDU set group to which the PDCP SDU belongs, and / or (3b) discard all PDCP SDUs and corresponding PDCP data PDUs belonging to the PDU set synchronized with the PDU set to which the PDCP SDU belongs, and / or (4b) indicate the discard to the upper layer, and / or (5b) if the PDCP SDU belongs to a synchronization PDU set group, discard all PDCP SDUs and corresponding PDCP data PDUs belonging to the synchronization PDU set group to which the PDCP SDU belongs, and / or (6b) if the PDCP SDU belongs to a PDU set or a synchronization PDU set group, indicate the discard to the upper layer, and / or (7b) stop the synchronization timer associated with the PDU set to which the PDCP SDU belongs or the synchronization PDU set group or other PDU set synchronized with the PDU set to which the PDCP SDU belongs.

[0017] In the synchronization method of the first aspect described above, when receiving an indication from the upper layer, i.e., SDAP, to discard a PDCP SDU, the transmission PDCP performs the following operations: discarding the PDCP SDU and corresponding PDCP data PDUs, and / or if pdu-SetDiscard is configured, discarding all PDCP SDUs and corresponding PDCP data PDUs belonging to the PDU set to which the PDCP SDU belongs.

[0018] In the synchronization method of the first aspect described above, the transmission SDAP entity, upon receiving an indication from the lower layer that an SDAP PDU or SDU has been submitted or has been successfully transmitted, performs at least one of the following:

[0019] (1) If the SDAP PDU or SDU is the first or last SDAP PDU or SDU of the PDU set to which it belongs or is the first or last SDAP PDU or SDU of the PDU set to which it belongs that is indicated to have been submitted or successfully transmitted, starting the synchronization timer associated with the PDU set synchronized with the PDU set to which the SDAP PDU or SDU belongs, or starting the synchronization timer associated with the PDU set to which the SDAP PDU or SDU belongs, or starting the synchronization timer associated with the synchronization PDU set group to which the SDAP PDU or SDU belongs;

[0020] (2) if the SDAP PDU or SDU is the first SDAP PDU or SDU in the last PDU set in the synchronization PDU cluster to which the SDAP PDU or SDU belongs, stop the synchronization timer associated with the PDU sets synchronized with the PDU set to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the PDU set to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the synchronization PDU cluster to which the SDAP PDU or SDU belongs;

[0021] (3) if the SDAP PDU or SDU is the last SDAP PDU or SDU of the PDU set to which the SDAP PDU or SDU belongs, or if the SDAP PDU or SDU is the last SDAP PDU or SDU of the PDU set to which the SDAP PDU or SDU belongs that is indicated as submitted or successfully transmitted, or if the SDAP PDU or SDU is the first or the last SDAP PDU or SDU of the last PDU set of the synchronization PDU cluster to which the SDAP PDU or SDU belongs that is indicated as submitted or successfully transmitted, stop the synchronization timer associated with the PDU sets synchronized with the PDU set to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the PDU set to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the synchronization PDU cluster to which the SDAP PDU or SDU belongs.

[0022] Further, according to the second aspect of the present application, a user equipment is provided, comprising: a processor; and a memory storing instructions, wherein the instructions, when executed by the processor, perform the above-mentioned synchronization method.

[0023] Effects of Invention

[0024] According to the synchronization method and the corresponding user equipment provided by the present application, the synchronization problem between PDUs or PDU sets can be effectively solved. BRIEF DESCRIPTION OF DRAWINGS

[0025] The above and other features of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0026] Fig. 1 is a schematic diagram showing the protocol stack involved in the air interface transmission of the present application.

[0027] Fig. 2 is a schematic diagram showing one mapping relationship between data flows and RLC in a multi-mode service.

[0028] Fig. 3 is a schematic diagram showing another mapping relationship between data flows and bearers in a multi-mode service.

[0029] Fig. 4 is a block diagram of a user equipment UE involved in the present application. DETAILED DESCRIPTION

[0030] Some terms related to the present application are described below, and the specific meanings of the terms can be referred to the latest relevant documents of 3GPP, such as TS 38.300-i20, TS 38.321-i20, TS 38.323-i20, TS 38.331-i20, and the like. In addition, embodiments of the present application are described by taking broadcast / multicast service as an example, but embodiments of the present application are not limited to broadcast / multicast service, and can also be applied to other application scenarios.

[0031] UE: User Equipment, user equipment.

[0032] RRC: Radio Resource Control, radio resource control.

[0033] RRC_CONNECTED: RRC connected state.

[0034] RRC_INACTIVE: RRC inactive state.

[0035] RRC_IDLE: RRC idle state.

[0036] RAN: Radio Access Network, radio access network.

[0037] NR: New RAT, new radio access technology.

[0038] AS: Access Stratum, access layer or access stratum.

[0039] NAS: Non Access Stratum, non-access layer or non-access stratum.

[0040] RB: Radio Bearer, radio bearer. DRB is a data radio bearer. Each DRB can be associated with an SDAP entity, and has a corresponding PDCP entity and one or more RLC entities.

[0041] PDU: Protocol Data Unit, protocol data unit

[0042] SDU: Service Data Unit, service data unit

[0043] AM: Acknowledged Mode, acknowledged mode

[0044] UM: Unacknowledged Mode, unacknowledged mode

[0045] TM: Transparent Mode, transparent mode

[0046] SDAP: Service Data Adaptation Protocol

[0047] PDCP: Packet Data Convergence Protocol

[0048] RLC: Radio Link Control

[0049] MAC: Medium Access Control

[0050] HARQ: Hybrid Automatic Repeat reQuest. The HARQ entity or process is located at the MAC layer or MAC entity.

[0051] A PDU set consists of one or more PDUs that carry the payload of a single information unit (e.g., a frame or video slice from an XR service) generated at the application level. In some implementations, the application layer requires all PDUs in the set to use the corresponding information unit. In other implementations, the application layer can still recover some or all of the information units even if some PDUs are lost. One PDU in the set corresponds to one PDCP SDU.

[0052] Multi-modal data is defined as input data from different types of devices / sensors or output data to different types of destinations (e.g., one or more UEs) required to describe the same task or application. Multi-modal data consists of multiple single-modal data sets, each with strong dependencies on the others. A single-modal data set can be viewed as a single type of data. Each single-modal data set can be mapped to a data flow. Each data flow has corresponding Quality of Service (QoS) requirements; therefore, a data flow is also called a Quality of Service (QoS) flow or QoS stream.

[0053] Multi-modal service: A multi-modal service is a communication service consisting of multiple interconnected data streams that require application coordination. These data streams can transmit different types of data (e.g., audio, video, location, haptic data) and may originate from different sources (e.g., a single UE, a single device connected to a single UE, or multiple devices, or multiple UEs). In the case of a single UE, these data streams are closely related and require strong application coordination to correctly execute multi-modal applications; therefore, all these data streams are transmitted within a single PDU session.

[0054] A Multi-modal Service ID (MMSID) is used to indicate a data flow associated with a multi-modal service. Data flows with the same MMSID belong to the same multi-modal service.

[0055] Synchronization threshold: A multi-modal synchronization threshold can be defined as the maximum tolerable temporal separation of the onset of two stimuli, one presented to one sense and the other to another sense, such that the accompanying sensory objects are perceived as being synchronous. Synchronization relationships may exist between single-mode data within the same multi-modal dataset. A PDU set from one single-mode dataset may be synchronized with PDU sets from one or more other single-mode datasets. For example, when data transmission of one PDU set begins (or ends), data transmission of one or more synchronized PDU sets must begin (or end) within the time limit limited by the synchronization threshold. In this disclosure, a collection of PDU sets consisting of two or more PDU sets with a synchronization relationship is referred to as a synchronized PDU cluster. A synchronized PDU cluster also includes a synchronized PDU cluster containing only one PDU set, where the PDUs in that PDU set have dependencies or synchronization relationships. Unless otherwise specified, the synchronous PDU cluster described in the embodiments of this disclosure may refer to a situation that includes one or more PDU sets.

[0056] Figure 1 illustrates an example of the protocol stack involved in air interface data transmission according to this disclosure. The protocol stack, from top to bottom, consists of SDAP, PDCP, RLC, MAC, and the physical layer. The layer below the SDAP layer can be PDCP and / or RLC and / or MAC and / or the physical layer; the layer below the PDCP layer can be RLC and / or MAC and / or the physical layer; and the layer below the RLC layer can be MAC and / or the physical layer. Correspondingly, the layer above the MAC layer can be SDAP and / or PDCP and / or RLC; the layer above the RLC layer can be SDAP and / or PDCP; and the layer above the PDCP layer can be SDAP. The functions of each layer are implemented by corresponding entities. Specifically, the functions of the MAC layer are implemented by the MAC entity, the RLC layer by the RLC entity, the PDCP layer by the PDCP entity, and the SDAP layer by the SDAP entity. In this disclosure, layers and entities are used interchangeably. When referring to a layer or entity in this disclosure, if it is not specifically stated whether it is an entity or a layer, those skilled in the art can infer from the context whether it refers to the corresponding layer or entity. In the embodiments of this disclosure, SDU and PDU are used interchangeably. Those skilled in the art can easily deduce from the context that the SDU is the SDU corresponding to the PDU, and similarly, the PDU is the PDU corresponding to the SDU. Therefore, unless otherwise specified, embodiments obtained by replacing PDU with SDU or SDU with PDU are also within the scope of this disclosure.

[0057] From the UE's perspective, for downlink, when the physical layer receives data from the base station, it delivers it to the MAC layer. The MAC layer processes the data and then forwards it to the corresponding RLC entity. The RLC entity processes the data and then forwards it to the PDCP layer. The PDCP layer processes the data and then forwards it to the SDAP layer. The SDAP layer processes the data and then forwards it to the upper layer (e.g., the NAS layer). For uplink, the SDAP layer receives data from the upper layer (e.g., the NAS layer), processes it, and then submits it to the corresponding PDCP entity. The PDCP entity processes the data and then submits it to the corresponding RLC entity. The RLC entity processes the data and then submits it to the MAC layer. The MAC layer processes the data and then submits it to the physical layer. The physical layer processes the data and then sends it to the base station over the air interface. For each layer, the data received from the upper layer is called SDU, and the data submitted to the lower layer is called PDU. For example, data received or transmitted from the SDAP layer to the SDAP layer by the PDCP layer is called PDCP SDU (i.e., SDAP PDU), and data received or submitted from the RLC layer to the RLC layer by the PDCP layer is called PDCP PDU (i.e., RLC SDU), and so on for other layers.

[0058] In this invention, the network, base station, and RAN are interchangeable. The network can be a Long Term Evolution (LTE) network, an NR network, an enhanced Long Term Evolution (eLTE) network, or other networks defined in subsequent 3GPP evolution versions, such as a 6G network. For downlink (i.e., the UE-side data reception process), the PDCP entity is also called the receiving PDCP entity, and the corresponding peer entity (i.e., the PDCP entity located at the base station) is the transmitting PDCP entity. For uplink (i.e., the UE-side data transmission process), the PDCP entity is also called the transmitting PDCP entity, and the corresponding peer entity (i.e., the PDCP entity located at the base station) is the receiving PDCP entity. The RLC entity supports three modes: AM RLC, UM RLC, and TM RLC, and their corresponding RLC entities are AM RLC entity, UM RLC entity, and TM RLC entity, respectively. The UM RLC entity can be configured as a receiving UM RLC entity and a transmitting UM RLC entity to perform reception and transmission operations respectively. A TM RLC entity can also be configured to perform receive and transmit operations separately as a receiving TM RLC entity and a transmitting TM RLC entity. An AM RLC entity includes a transmitting side and a receiving side, used to receive data from the upper layer and transmit it to the peer AM RLC entity via the lower layer, and to deliver data to the upper layer and receive data from the peer AM RLC entity via the lower layer, respectively. In the embodiments of this disclosure, when referring to RLC entities, those skilled in the art can correspondingly replace them with transmitting or receiving UM RLC entities, TM RLC entities, or the transmitting or receiving side of AM RLC entities.

[0059] One aspect of the current R19 XR discussion focuses on is the synchronization of multi-modal data. In other words, to achieve synchronization or coordination between data (or PDUs or sets of PDUs) from different data streams, when data transmission of one PDU or set of PDUs begins (or ends), data transmission of one or more PDU sets that are being synchronized with it (i.e., other PDU sets within the synchronized PDU cluster) must begin (or end) within a time limit limited by a synchronization threshold. How to achieve synchronization between PDUs or sets of PDUs is a problem that needs to be solved.

[0060] The following examples are provided to solve this problem.

[0061] A synchronization timer is associated with each synchronization PDU cluster or PDU set. The value of the timer can be configured by the base station for the UE via RRC messages or provided by an upper layer (e.g., the NAS layer). The UE achieves multi-mode data synchronization by maintaining the synchronization timer. If the synchronization timer value is configured by the base station, the base station can configure the timer value separately for each group of data streams that need to be synchronized, for example, configuring the timer value for each DRB or each PDCP entity. If the synchronization timer value is provided by an upper layer, the base station can configure an indication flag (i.e., synchronization PDU cluster parameters) for the UE to indicate whether the UE is allowed to start or run the synchronization timer or whether inter-PDU set synchronization or multi-mode data synchronization is supported (or allowed or configured).

[0062] Figure 2 illustrates a mapping relationship between data flows and RLCs in a multi-mode service. As shown in Figure 2, the SDAP entity maps all QoS flows associated with a multi-mode service to a data bearer (DRB). The PDCP then submits the PDCP SDUs (or corresponding PDCP PDUs) of different QoS flows to the RLC entity corresponding to the QoS flow. For example, the PDCP SDU of QoS flow 1 is mapped to RLC1, and the PDCP SDU of QoS flow 2 is mapped to RLC2.

[0063] Figure 3 illustrates another mapping relationship between data streams and bearers in a multi-mode service. As shown in Figure 3, the SDAP entity maps different QoS streams (i.e., the data of the QoS streams) associated with a multi-mode service to different data bearers (DRBs) or their corresponding PDCP entities. For example, the data of QoS stream 1 (or SDAP PDU) is mapped to DRB1 or PDCP1, and the data of QoS stream 2 (or SDAP PDU) is mapped to DRB2 or PDCP2.

[0064] Based on the different mapping relationships between QoS flows and DRBs, the synchronization timer can run at the SDAP layer, PDCP layer, or RLC layer. For example, if the mapping relationship in Figure 2 is used, the synchronization timer can run at the PDCP layer; if the mapping relationship in Figure 3 is used, the synchronization timer can run at the SDAP layer.

[0065] The following describes the operations performed by the PDCP entity during transmission.

[0066] In one embodiment, upon submitting a PDCP PDU to a lower layer, or upon receiving an indication of successful submission (i.e., submission or submission for transmission) of a PDCP PDU or PDCP SDU from a lower layer (e.g., RLC or MAC), or upon receiving an indication that a PDCP PDU or PDCP SDU has been transmitted from a lower layer (e.g., RLC or MAC), or upon receiving an indication that a PDCP PDU or PDCP SDU has been successfully transmitted from a lower layer (e.g., RLC or MAC), the PDCP transmission entity performs the following operations:

[0067] If the UE or the PDCP entity is configured for multi-mode data synchronization and / or the PDCP PDU belongs to a synchronized PDU cluster (in other words, the PDCP PDU belongs to a set of PDUs within a synchronized PDU cluster) and / or the PDCP PDU belongs to a set of PDUs (this set of conditions is optional; for example, if an indication of successful submission of a PDCP PDU or PDCP SDU from a lower layer is received, then at least one of the following operations is performed directly):

[0068] Operation 1-1: If the synchronization timer associated with the synchronization PDU cluster to which the PDCP PDU or PDCP SDU belongs is not running, or if the synchronization timer associated with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, or if the synchronization timer associated with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, then start the synchronization timer.

[0069] Operation 1-2: If the PDCP PDU or PDCP SDU is the first PDCP PDU or PDCP SDU in its PDU set or synchronous PDU cluster, and / or if a synchronization timer is configured, and / or the synchronization timer associated with the synchronous PDU cluster to which the PDCP PDU or PDCP SDU belongs is not running or the synchronization timer associated with a PDU set that has a synchronization relationship with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, and / or the synchronization timer associated with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, then: (1) if the synchronization timer of the PDU set or synchronous PDU cluster to which the PDCP PDU or PDCP SDU belongs is running, then stop the synchronization timer, and / or (2) start the synchronization timer, and / or (3) indicate the submission information to the upper layer (i.e., SDAP), for example, indicating to the upper layer that the first PDCP PDU or PDCP SDU in the PDU set or synchronous PDU cluster has been submitted. The relevant information of the SDU is provided so that the upper layer can start the timer associated with the PDU set or the synchronization PDU cluster when the instruction is received. It should be noted that the condition "the synchronization timer associated with the PDU set that has a synchronization relationship with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running" may contain multiple PDU sets that have a synchronization relationship with the PDU set to which the PDCP PDU or PDCP SDU belongs, and there may be multiple corresponding synchronization timers. If the condition is applied, the synchronization timers associated with the PDU sets that have a synchronization relationship with the PDU set to which the PDCP PDU or SDU belongs will be started respectively.

[0070] Operations 1-3: If the PDCP PDU or PDCP SDU is the last PDCP PDU or PDCP SDU submitted to the lower layer in its PDU set or synchronous PDU cluster (in other words, all PDCP PDUs or PDCP SDUs in the PDU set or synchronous PDU cluster have been submitted to the lower layer or transmitted), or if the PDCP PDU or PDCP SDU is the first (or last) PDCP PDU or PDCP SDU submitted to the lower layer (or confirmed by the lower layer as sent or successfully transmitted) in the PDU set of its synchronous PDU cluster that was the last to submit a PDCP PDU to the lower layer (in other words, all other PDU sets in the synchronous PDU cluster have PDCP PDUs or PDCP SDUs submitted to the lower layer or transmitted), or if the PDCP PDU or PDCP SDU is the last PDCP PDU or PDCP SDU in its PDU set or synchronous PDU cluster that has been confirmed by the lower layer as successfully transmitted (in other words, all PDCP PDUs or PDCP SDUs in the PDU set or ...... If all SDUs have been confirmed as successfully transmitted by the lower layer, then the synchronization timer associated with the PDU set or synchronous PDU cluster to which the PDCP PDU or PDCP SDU belongs (the timer only executes during runtime) is stopped, or the submission is indicated to the upper layer (e.g., SDAP). For example, the submission is indicated to the upper layer that the PDCP PDU or PDCP SDU is the last PDCP PDU or PDCP SDU in its PDU set or synchronous PDU cluster to be submitted to the lower layer.

[0071] It can be stipulated that when a PDCP entity receives an indication of successful submission or transmission of the last PDCP PDU or PDCP SDU in a PDU set or synchronous PDU cluster from a lower layer (RLC or MAC) (in other words, all PDCP PDUs or PDCP SDUs in the PDU set or synchronous PDU cluster have been indicated by the lower layer to have been submitted to the lower layer or have been confirmed by the lower layer to have been successfully transmitted), the synchronization timer associated with the PDU set or the synchronous PDU cluster can be stopped.

[0072] In this embodiment, the indication or transmission indication of successful submission of the PDCP PDU or PDCP SDU can originate from the MAC or RLC layer. Specifically, if the indication of successful submission of the PDCP PDU or SDU originates from the MAC layer, the MAC entity is required to send an indication to the PDCP layer or upper layer upon confirming the successful transmission of the PDCP PDU or SDU or its containing transport block. If the indication of transmission of the PDCP PDU or SDU originates from the MAC layer, the MAC entity is required to send an indication to the PDCP layer when multiplexing the PDCP PDU to a MAC PDU and / or submitting the MAC PDU to the lower layer for transmission. If the indication of successful submission of the PDCP PDU or SDU originates from the RLC layer, the RLC entity is required to send an indication to the upper layer (PDCP layer) when submitting an RLCPDU containing the PDCP PDU (or the last byte or the first byte of the PDCP PDU) to the lower layer. Furthermore, it can be stipulated that the MAC or RLC will only send an indication of successful submission or transmission of the PDCP PDU or SDU when it determines that the PDCP PDU or SDU is the first PDCP PDU or SDU in its PDU set, or the MAC or RLC entity will only send an indication of successful submission or transmission of the PDCP PDU or SDU when multi-mode data synchronization is configured.

[0073] The indication of successful transmission from the lower layer comes from the MAC layer. After the MAC layer confirms that a transport block containing the PDCP PDU or SDU (or a portion thereof) has been successfully transmitted, it sends an indication to the upper layer (PDCP layer).

[0074] It should be noted that in operations 1-2 of this embodiment, the first PDCP PDU or SDU of the PDU set can be replaced by one of the following descriptions: the first PDCP PDU or SDU submitted to the lower layer of the PDU set, the first PDCP PDU or SDU of the PDU set that has been confirmed to be successfully transmitted, the last PDCP PDU or SDU of the PDU set, the last PDCP PDU or SDU submitted to the lower layer of the PDU set, the last PDCP PDU or SDU of the PDU set that has been confirmed to be successfully transmitted, the first PDCP PDU or SDU of the synchronous PDU cluster, the first PDCP PDU or SDU submitted to the lower layer of the synchronous PDU cluster, the first PDCP PDU or SDU of the synchronous PDU cluster that has been confirmed to be successfully transmitted, the first PDCP PDU or SDU of the first PDU set in the synchronous PDU cluster, the first PDCP PDU or SDU submitted to the lower layer of the first PDU set in the synchronous PDU cluster, and the first PDCP PDU or SDU of the first PDU set in the synchronous PDU cluster that has been confirmed to be successfully transmitted.

[0075] In this embodiment of the disclosure, the timer associated with the synchronization PDU cluster can also be replaced with the timer associated with the PDU set to which the PDCP PDU or its corresponding PDCP SDU belongs. The UE being configured for multi-mode data synchronization can be replaced with the PDCP entity being configured for multi-mode data synchronization. The UE, PDCP, or SDAP being configured for multi-mode data synchronization can refer to one of the following: being configured with a synchronization timer, being configured for inter-PDU set discarding (i.e., if a PDCP PDU or SDU in a PDU set is discarded, then all PDCP PDUs or SDUs in the synchronization PDU cluster to which the PDU set belongs are discarded), or being configured for inter-PDU set synchronization. A PDCP PDU or SDU belonging to a synchronous PDU cluster means one of the following: the PDCP SDU corresponding to the PDCP PDU belongs to a synchronous PDU cluster; the PDCP PDU or its corresponding PDCP SDU belongs to a set of PDUs in a synchronous PDU cluster; the PDCP PDU or its corresponding PDCP SDU has a synchronization relationship with other PDCP PDUs or PDCP SDUs in the synchronous PDU cluster; or the PDCP PDU or its corresponding PDCP SDU belongs to a set of PDUs in the synchronous PDU cluster to which the PDU set belongs has a synchronization relationship. The synchronous PDU cluster to which the PDCP PDU or SDU belongs is simply the synchronous PDU cluster of the set of PDUs to which the PDCP PDU or SDU belongs.

[0076] The PDU set or synchronous PDU cluster to which the PDCP PDU belongs in the embodiments of this disclosure is the same as the PDU set or synchronous PDU cluster to which the corresponding PDCP SDU belongs, and vice versa. The PDCP SDU of a synchronous PDU cluster is the same as the PDCP PDU of the synchronous PDU cluster, that is, the PDCP SDU or PDCP PDU of the PDU set within the synchronous PDU cluster. A PDCP PDU belonging to a PDU set or synchronous PDU cluster is the same as a PDCP SDU belonging to a PDU set or synchronous PDU cluster, and vice versa.

[0077] When a PDCP PDU or SDU belonging to a PDU set is discarded, if the PDU set belongs to a synchronous PDU cluster, discarding the PDCP PDU or SDU may render other PDCP PDUs or SDUs in other PDU sets within the synchronous PDU cluster invalid. Continuing to transmit these unnecessary or invalid PDCP PDUs or SDUs will result in wasted resources. The following embodiments address this problem.

[0078] The following describes the operations involved in a PDCP entity discarding a PDCP SDU.

[0079] When a PDCP SDU's discard timer expires, or its low-importance discard timer expires, or its synchronization timer (i.e., the synchronization timer associated with the PDU set or synchronization PDU cluster to which the PDCP SDU belongs) expires, the PDCP transport entity performs at least one of the following operations:

[0080] Operation 2-1: If pdu-SetDiscard is configured, then: (1a) Discard all PDCP SDUs belonging to the PDU set to which the PDCP SDU belongs, and the corresponding PDCP data PDUs, and / or (2a) if interPdu-setDiscard is configured or the synchronization timer expires, discard all PDCP SDUs belonging to the synchronous PDU cluster to which the PDCP SDU belongs, and the corresponding PDCP data PDUs (i.e., PDCP SDUs and the corresponding PDCP data PDUs of all PDU sets belonging to the synchronous PDU cluster), and / or (3a) if interPdu-setDiscard is configured or if the PDCP SDU belongs to a synchronous PDU cluster (i.e., the PDU set to which the PDCP SDU belongs belongs to a synchronous PDU cluster) or if the synchronization timer expires, discard all PDCP SDUs belonging to the synchronous PDU cluster to which the PDCP SDU belongs, and the corresponding PDCP data PDUs, and / or (4a) if interPdu-setDiscard is configured and / or if the PDCP SDU belongs to a synchronous PDU cluster (i.e., the PDCP SDU set to which the PDCP SDU belongs belongs to a synchronous PDU cluster), and / or if the PDCP SDU belongs to a synchronous PDU cluster (i.e., the PDCP SDU set to which the PDCP SDU belongs belongs to a synchronous PDU cluster), and / or if interPdu-setDiscard is configured and / or if the PDCP SDU belongs to a synchronous PDU cluster (i.e., the PDCP SDU set to which the PDCP SDU belongs belongs to a synchronous PDU cluster), and / or if the synchronization timer expires, discard all PDCP SDUs belonging to the synchronous PDU cluster to which the PDCP SDU belongs, and / or (4a) if interPdu-setDiscard is configured and / or if the PDCP SDU belongs to a synchronous PDU cluster (i.e., the PDCP SDU set If the PDU set to which the SDU belongs belongs to a synchronous PDU cluster, or if there exists a PDU set synchronized with the PDU set to which the PDCP SDU belongs, the upper layer (i.e., SDAP) is instructed to discard the SDU, and / or (5a) if interPdu-setDiscard is configured and / or if the PDCP SDU belongs to a PDU set of a synchronous PDU cluster, or if there exists a PDU set synchronized with the PDU set to which the PDCP SDU belongs, the synchronization timer associated with the PDU set to which the PDCP SDU belongs, the synchronous PDU cluster, or the PDU set synchronized with the PDU set synchronized with the PDU set to which the PDCP SDU belongs (the synchronization timer performs this operation only during runtime). It should be noted that in this operation, "discard all PDCP SDUs belonging to the synchronous PDU cluster to which the PDCP SDU belongs and the corresponding PDCP data PDUs" can be replaced with "discard all PDCP SDUs belonging to the PDU set synchronized with the PDU set to which the PDCP SDU belongs and the corresponding PDCP data PDUs".

[0081] Operation 2-2: If interPdu-setDiscard is configured and / or a synchronization timer is configured and / or the PDCP SDU belongs to a PDU set or a synchronized PDU cluster and / or there exists a PDU set that is synchronized with the PDU set to which the PDCP SDU belongs, then: (1b) Discard all PDCP SDUs belonging to the PDU set to which the PDCP SDU belongs, and / or (2b) Discard all PDCP SDUs belonging to the synchronized PDU cluster to which the PDCP SDU belongs, and / or (3b) Discard all PDCP SDUs belonging to the PDU set synchronized with the PDU set to which the PDCP SDU belongs, and / or (4b) Indicate the discard to the upper layer (i.e., SDAP), and / or (5b) If the PDCP SDU belongs to a synchronized PDU cluster (i.e., the PDU set to which the PDCP SDU belongs belongs to a synchronized PDU cluster), discard all PDCP SDUs belonging to the synchronized PDU cluster to which the PDCP SDU belongs. SDU and corresponding PDCP data PDU, and / or (6b) if the PDCP SDU belongs to a PDU set or a synchronous PDU cluster (i.e., the PDU set to which the PDCP SDU belongs belongs to a synchronous PDU cluster, this condition is optional), instruct the upper layer (i.e., SDAP) to discard, and / or (7b) stop the synchronization timer associated with the PDU set to which the PDCP SDU belongs or the synchronous PDU cluster or other PDU sets synchronized with the PDU set to which the PDCP SDU belongs (the synchronization timer performs this operation only when running).

[0082] It should be noted that, in the above operation, it can be further specified that the discarding is only indicated to the upper layer when the discarded PDCP SDU is the first discarded PDCP SDU in the PDU set or the synchronization PDU cluster.

[0083] In addition, when an instruction to discard a PDCP SDU is received from the upper layer (i.e., SDAP), the PDCP transmission performs the following operations: discards the PDCP SDU and the corresponding PDCP data PDU, and / or if pdu-SetDiscard is configured (this condition is optional), discards all PDCP SDUs belonging to the PDU set to which the PDCP SDU belongs and the corresponding PDCP data PDU.

[0084] In this embodiment of the disclosure, unless otherwise specified, the synchronization timer expiration refers to the expiration of the synchronization timer associated with the PDU set to which the PDCP SDU belongs, the synchronous PDU cluster to which the PDCP SDU belongs, or the PDU set synchronized with the PDU set to which the PDCP SDU belongs. The synchronization timer can be maintained by the transport end, and its duration can be configured for the UE by the base station via RRC messages (e.g., RRC reconfiguration messages). One synchronization timer can be associated with each PDU set or synchronous PDU cluster. The discard timer is configured only for DRB, and its duration is configured for the UE by the base station via RRC messages. At the transport end (i.e., the transport PDCP entity), a new discard timer is started after receiving a PDCP SDU from the upper layer; in other words, one discard timer is associated with each PDCP SDU. The low-importance discard timer is configured only for DRB, and its duration is configured for the UE by the base station via RRC messages. At the transport end (i.e., the transport PDCP entity), a new low-importance discard timer is started when a PDCP SDU belonging to a low-importance PDU set is received from the upper layer. The parameter `pdu-SetDiscard` is configured by the base station for each PDCP entity of the UE via RRC messages. If `pdu-SetDiscard` is set to true, the UE performs PDU-based discarding for this PDCP entity. This parameter is configured only for DRB. The parameter `interPdu-setDiscard` can be configured by the base station for each PDCP entity or each SDAP entity of the UE via RRC messages (i.e., included in the parameters `PDCP-Config` or `SDAP-Config`). If `interPdu-SetDiscard` is set to true, the UE performs synchronous PDU-based discarding for this PDCP entity or SDAP entity. This parameter can be specified to be configured only for DRB. `PDCP-Config` is used to set configurable PDCP parameters for signaling, MBS multicast radio bearers, or data radio bearers, and `SDAP-Config` is used to set configurable SDAP parameters for DRB.

[0085] In this embodiment of the disclosure, the discarded PDU or PDU set or data may be PDCP PDU and / or PDCP SDU discarded by the PDCP entity and / or RLC PDU and / or RLC SDU discarded by the RLC entity or its segments.

[0086] The following is an example of the operations performed by the SDAP entity to achieve multi-mode data synchronization.

[0087] When the transport SDAP entity receives an SDAP SDU of a QoS stream from the upper layer, and constructs the SDAP data PDU corresponding to the SDAP SDU and submits it to the lower layer, if the SDAP data PDU belongs to a PDU set or a synchronous PDU cluster, and / or if a synchronization timer is configured, and / or if multi-mode data synchronization is configured, the SDAP entity indicates to the lower layer (e.g., the PDCP layer) the relevant information that the SDAP PDU belongs to a PDU set or a synchronous PDU cluster.

[0088] Upon receiving an indication from a lower-level SDAP PDU or SDU that it has been submitted or successfully transmitted, the transmitting SDAP entity shall perform at least one of the following:

[0089] (1) If the SDAP PDU or SDU is the first (or last) SDAP PDU or SDU in its PDU set or the first (or last) SDAP PDU or SDU in its PDU set that has been indicated to have been submitted or successfully transmitted, then start the synchronization timer associated with the PDU set to which the SDAP PDU or SDU belongs, or start the synchronization timer associated with the PDU set to which the SDAP PDU or SDU belongs, or start the synchronization timer associated with the synchronous PDU cluster to which the SDAP PDU or SDU belongs.

[0090] (2) If the SDAP PDU or SDU is the first SDAP PDU or SDU in the last PDU set of its corresponding synchronous PDU cluster, then stop the synchronization timer associated with the PDU set synchronized with the PDU set to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the PDU set to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the synchronous PDU cluster to which the SDAP PDU or SDU belongs. It should be noted that there may be multiple PDU sets synchronized with the PDU set to which the SDAP PDU or SDU belongs; in this case, stop the synchronization timer associated with each of the PDU sets synchronized with the PDU set to which the SDAP PDU or SDU belongs.

[0091] (3) If the SDAP PDU or SDU is the last SDAP PDU or SDU in its PDU set, or if the SDAP PDU or SDU is the last SDAP PDU or SDU in its PDU set that has been indicated as submitted or successfully transmitted, or if the SDAP PDU or SDU is the first or last SDAP PDU or SDU in the last PDU set in its synchronous PDU cluster that has been indicated as submitted or successfully transmitted, then stop the synchronization timer associated with the PDU set to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the PDU set to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the synchronous PDU cluster to which the SDAP PDU or SDU belongs.

[0092] When a transmitting SDAP entity receives a discard instruction for an SDAP PDU (i.e., a PDCP SDU) or its corresponding SDAP SDU from a lower layer (i.e., a PDCP entity), and / or the SDAP PDU or SDU belongs to a PDU set that is synchronized with other PDU sets, or belongs to a synchronized PDU cluster, or a PDU set belonging to a synchronized PDU cluster, it stops the synchronization timer associated with the PDU set or the synchronized PDU cluster, and / or instructs other PDCP entities to delete the PDCP SDU belonging to the synchronized PDU cluster. It can be specified that the other PDCP entities are PDCP entities used to transmit PDCP SDUs or PDUs from other PDU sets that are synchronized with the SDAP PDU or SDU of the PDU set.

[0093] It can be stipulated that, in this embodiment of the disclosure, before executing the start of the synchronization timer, it can be determined whether the synchronization timer is running, and the synchronization timer is started only if it is not running.

[0094] When the synchronization timer associated with a PDU set or synchronous PDU cluster expires, it instructs the lower layer (i.e., the PDCP entity) to delete the PDCP SDUs belonging to the PDU set or synchronous PDU cluster. It can be specified that the PDCP entity is the PDCP entity used to transmit the PDCP SDUs of the PDU set or synchronous PDU cluster.

[0095] It should be noted that, in this disclosure, SDAP PDU belonging to a PDU set or synchronous PDU cluster means that the SDAP SDU corresponding to the SDAP PDU belongs to a PDU set or synchronous PDU cluster, and vice versa.

[0096] In this disclosure, fields, domains, and information elements are used interchangeably. In the embodiments of this disclosure, if multiple operations need to be performed, unless otherwise specified, embodiments obtained by changing the execution order of the operations are also within the scope of protection of this disclosure. Similarly, when multiple parallel judgment conditions are involved, embodiments obtained by changing the order of the judgment conditions are also within the scope of protection of this disclosure. The terms "and," "or," "and / or," "and," and "and" in the conditions involved in the embodiments of this disclosure are used interchangeably, and the resulting embodiments are also within the scope of this disclosure.

[0097] The following description uses FIG4 to illustrate a user equipment that can perform the synchronization method described in detail above as an embodiment of the present invention.

[0098] Figure 4 is a block diagram illustrating the user equipment (UE) involved in this invention.

[0099] As shown in Figure 4, the user equipment UE400 includes a processor 401 and a memory 402. The processor 401 may include, for example, a microprocessor, a microcontroller, an embedded processor, etc. The memory 402 may include, for example, volatile memory (such as random access memory, RAM), a hard disk drive (HDD), non-volatile memory (such as flash memory), or other memory. Program instructions are stored in the memory 402. When executed by the processor 401, these instructions can perform the methods described in detail herein, executed by the user equipment.

[0100] The synchronization method and corresponding user equipment involved in this invention have been described in detail above based on embodiments. This synchronization method can be executed by the user equipment. This invention is not limited to the synchronization method and corresponding user equipment; it can be implemented in other ways as long as the spirit of this invention is achieved.

[0101] The methods and related apparatus of this disclosure have been described above in conjunction with preferred embodiments. Those skilled in the art will understand that the methods shown above are merely exemplary, and the various embodiments described above can be combined with each other without contradiction. The methods of the present invention are not limited to the steps and order shown above.

[0102] In the embodiments of this disclosure, when multiple operations are included, the execution order of each operation is exemplarily listed. Embodiments obtained by changing the execution order of each operation are also within the scope of protection of this disclosure. Furthermore, when multiple judgment conditions are included, embodiments obtained by changing the execution order of each judgment condition are also within the scope of protection of this disclosure. In addition, unless otherwise specified in this disclosure, the meaning of a domain defined in one embodiment can also be applied to the corresponding domain involved in other embodiments. Furthermore, in the embodiments of this disclosure, "if...", "when...", "when...", "in...", "satisfies...", or "satisfies..." conditions can be replaced with "in the case of...". In the embodiments of this disclosure, embodiments obtained by replacing "and", "and", and "and" in some or all conditions with "or" are also within the scope of protection of this disclosure; embodiments obtained by replacing "or" in some or all conditions with "and" are also within the scope of protection of this disclosure.

[0103] Furthermore, the user equipment shown above may include more modules, such as modules that can be developed or will be developed in the future for use with base stations, MMEs, or UEs, etc. The various identifiers shown above are merely exemplary and not limiting, and this disclosure is not limited to the specific information elements exemplified by these identifiers. Many variations and modifications can be made by those skilled in the art based on the teachings of the illustrated embodiments.

[0104] It should be understood that the above embodiments of this disclosure can be implemented by software, hardware, or a combination of both. For example, the various components inside the base station and user equipment in the above embodiments can be implemented by a variety of devices, including but not limited to: analog circuit devices, digital circuit devices, digital signal processing (DSP) circuits, programmable processors, proprietary integrated circuits (ASICs), field-programmable gate arrays (FPGAs), programmable logic devices (CPLDs), and so on.

[0105] Furthermore, the computer-executable instructions or program running on the device according to the invention can be a program that enables the computer to perform the functions of the embodiments of the invention by controlling the central processing unit (CPU). The program or the information processed by the program can be temporarily stored in volatile memory (such as random access memory RAM), hard disk drive (HDD), non-volatile memory (such as flash memory), or other memory systems.

[0106] Computer-executable instructions or programs for implementing the functions of the various embodiments of the present invention can be recorded on a computer-readable storage medium. The corresponding functions can be implemented by causing a computer system to read and execute the programs recorded on the recording medium. The term "computer system" here can refer to a computer system embedded in the device, and may include an operating system or hardware (such as peripheral devices). "Computer-readable storage medium" can be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a short-time dynamic program storage medium, or any other computer-readable recording medium.

[0107] Various features or functional modules of the devices used in the above embodiments can be implemented or executed by circuits (e.g., monolithic or multi-chip integrated circuits). Circuits designed to perform the functions described in this specification may include general-purpose processors, digital signal processors (DSPs), proprietary integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination of the above devices. A general-purpose processor may be a microprocessor, or any existing processor, controller, microcontroller, or state machine. The above circuits may be digital circuits or analog circuits. In cases where advancements in semiconductor technology have led to new integrated circuit technologies that replace existing integrated circuits, one or more embodiments of the present invention may also be implemented using these new integrated circuit technologies.

[0108] Furthermore, the present invention is not limited to the embodiments described above. Although various examples of the embodiments have been described, the present invention is not limited thereto. Fixed or non-mobile electronic devices installed indoors or outdoors can be used as terminal devices or communication devices, such as AV equipment, kitchen equipment, cleaning equipment, air conditioners, office equipment, vending machines, and other household appliances.

[0109] As described above, embodiments of the present invention have been described in detail with reference to the accompanying drawings. However, the specific structure is not limited to the above embodiments, and the present invention also includes any design modifications that do not depart from the spirit of the invention. Furthermore, various modifications can be made to the present invention within the scope of the claims, and embodiments obtained by appropriately combining the technical means invented in different embodiments are also included within the technical scope of the present invention. In addition, components with the same effects described in the above embodiments can be substituted for each other.

Claims

1. A synchronization method, comprising: associating a synchronization timer with each synchronization PDU group or PDU set, the value of the timer being configured for the UE by the base station through RRC message or provided by upper layer; the UE implements multi-mode data synchronization by maintaining the synchronization timer; in case the value of the synchronization timer is configured by the base station, the base station configures the value of the timer for each group of data flows that need to be synchronized respectively, in case the value of the synchronization timer is provided by upper layer, the base station configures an indication for the UE, the indication indicating whether the UE is allowed to start or run the synchronization timer or whether inter-PDU set synchronization or multi-mode data synchronization is supported. 2.The synchronization method of claim 1, wherein, the synchronization timer is running at SDAP layer or PDCP layer or RLC layer based on the mapping relationship between QoS flow and DRB. 3.The synchronization method of claim 2, wherein, when submitting a PDCP PDU to lower layer, or when receiving an indication of successful submission of PDCP PDU or PDCP SDU from lower layer, or when receiving an indication of PDCP PDU or PDCP SDU has been transmitted from lower layer, or when receiving an indication of successful transmission of PDCP PDU or PDCP SDU from lower layer, the transmitting PDCP entity performs the following operations: if the UE or the PDCP entity is configured with multi-mode data synchronization and / or the PDCP PDU belongs to a synchronization PDU group and / or the PDCP PDU belongs to a PDU set, at least one of operation 1-1 to operation 1-3 is performed. 4.The synchronization method of claim 3, wherein, the operation 1-1: if the synchronization timer associated with the synchronization PDU group to which the PDCP PDU or PDCP SDU belongs is not running, or if the synchronization timer associated with the PDU set that has synchronization relationship with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, or if the synchronization timer associated with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, the synchronization timer is started. The operation 1-2: If the PDCP PDU or PDCP SDU is the first PDCP PDU or PDCP SDU of the PDU set or the synchronization PDU set group to which the PDCP PDU or PDCP SDU belongs, and / or if the synchronization timer is configured, and / or the synchronization timer associated with the synchronization PDU set group to which the PDCP PDU or PDCP SDU belongs is not running or the synchronization timer associated with the PDU set having a synchronization relationship with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, and / or the synchronization timer associated with the PDU set to which the PDCP PDU or PDCP SDU belongs is not running, then: (1) if the synchronization timer of the PDU set or the synchronization PDU set group to which the PDCP PDU or PDCP SDU belongs is running, stop the synchronization timer, and / or (2) start the synchronization timer, and / or (3) indicate the submission information to the upper layer, so that the upper layer starts the timer associated with the PDU set or the synchronization PDU set group when receiving the indication; The operation 1-3: If the PDCP PDU or PDCP SDU is the last PDCP PDU or PDCP SDU submitted to the lower layer of the PDU set or the synchronization PDU set group to which the PDCP PDU or PDCP SDU belongs, or if the PDCP PDU or PDCP SDU is the first PDCP PDU or PDCP SDU submitted to the lower layer of the PDU set to which the PDCP PDU or PDCP SDU belongs and which is the last PDCP PDU submitted to the lower layer of the synchronization PDU set group to which the PDCP PDU or PDCP SDU belongs, or if the PDCP PDU or PDCP SDU is the last PDCP PDU or PDCP SDU successfully transmitted by the lower layer of the PDU set or the synchronization PDU set group to which the PDCP PDU or PDCP SDU belongs, stop the synchronization timer associated with the PDU set or the synchronization PDU set group to which the PDCP PDU or PDCP SDU belongs, or indicate the submission to the upper layer.

5. The synchronization method of claim 2, wherein, The PDCP entity stops the synchronization timer associated with the PDU set or the synchronization PDU set group upon receiving an indication of successful submission or transmission of the last PDCP PDU or PDCP SDU of the PDU set or the synchronization PDU set group from the lower layer.

6. The synchronization method of claim 2, wherein, The indication of successful submission or transmission of the PDCP PDU or PDCP SDU can be from the MAC or RLC layer.

7. The synchronization method of claim 1, wherein, In the case of expiration of the discard timer of a PDCP SDU or expiration of the low importance discard timer or expiration of the synchronization timer, the transmitting PDCP entity performs at least one of the following operations: Operation 2-1 : If pdu-SetDiscard is configured, then: (la) discard all PDCP SDUs and corresponding PDCP Data PDUs belonging to the PDU Set to which the PDCP SDU belongs, and / or (2a) if interPdu-setDiscard is configured or the synchronization timer expires, discard all PDCP SDUs and corresponding PDCP Data PDUs belonging to the synchronization PDU Set group to which the PDCP SDU belongs, and / or (3a) if interPdu-setDiscard is configured or if the PDCP SDU belongs to a synchronization PDU Set group or if the synchronization timer expires, discard all PDCP SDUs and corresponding PDCP Data PDUs belonging to the synchronization PDU Set group to which the PDCP SDU belongs, and / or (4a) if interPdu-setDiscard is configured and / or if the PDCP SDU belongs to a synchronization PDU Set group, indicate the discard to upper layers, and / or (5a) if interPdu-setDiscard is configured and / or if the PDCP SDU belongs to a PDU Set of a synchronization PDU Set group or to a synchronization PDU Set group and / or if there is a PDU Set in synchronization relationship with the PDU Set to which the PDCP SDU belongs, stop the synchronization timer associated with the PDU Set to which the PDCP SDU belongs or the synchronization PDU Set group or the PDU Set in synchronization relationship with the PDU Set to which the PDCP SDU belongs; Operation 2-2: If interPdu-setDiscard is configured and / or a synchronization timer is configured and / or the PDCP SDU belongs to a PDU set or a synchronization PDU set group and / or there is a synchronization relationship with the PDU set to which the PDCP SDU belongs, then: (1b) discard all PDCP SDUs and corresponding PDCP data PDUs belonging to the PDU set to which the PDCP SDU belongs, and / or (2b) discard all PDCP SDUs and corresponding PDCP data PDUs belonging to the synchronization PDU set group to which the PDCP SDU belongs, and / or (3b) discard all PDCP SDUs and corresponding PDCP data PDUs belonging to the PDU set synchronized with the PDU set to which the PDCP SDU belongs, and / or (4b) indicate the discard to the upper layer, and / or (5b) if the PDCP SDU belongs to a synchronization PDU set group, discard all PDCP SDUs and corresponding PDCP data PDUs belonging to the synchronization PDU set group to which the PDCP SDU belongs, and / or (6b) if the PDCP SDU belongs to a PDU set or a synchronization PDU set group, indicate the discard to the upper layer, and / or (7b) stop the synchronization timer associated with the PDU set to which the PDCP SDU belongs or the synchronization PDU set group or other PDU set synchronized with the PDU set to which the PDCP SDU belongs.

8. The synchronization method of claim 7, wherein, When receiving an indication from the upper layer, i.e., SDAP, to discard a PDCP SDU, the transmission PDCP performs the following operations: discard the PDCP SDU and corresponding PDCP data PDUs, and / or if pdu-SetDiscard is configured, discard all PDCP SDUs and corresponding PDCP data PDUs belonging to the PDU set to which the PDCP SDU belongs.

9. The synchronization method of claim 1, wherein, The transmission SDAP entity, upon receiving an indication from the lower layer that an SDAP PDU or SDU has been submitted or has been successfully transmitted, performs at least one of the following: (1) If the SDAP PDU or SDU is the first or last SDAP PDU or SDU of the PDU set to which it belongs or is the first or last SDAP PDU or SDU of the PDU set to which it belongs that is indicated to have been submitted or successfully transmitted, start the synchronization timer associated with the PDU set synchronized with the PDU set to which the SDAP PDU or SDU belongs, or start the synchronization timer associated with the PDU set to which the SDAP PDU or SDU belongs, or start the synchronization timer associated with the synchronization PDU set group to which the SDAP PDU or SDU belongs. (2) if the SDAP PDU or SDU is the first SDAP PDU or SDU in the last PDU group in the synchronization PDU group to which the SDAP PDU or SDU belongs, stop the synchronization timer associated with the PDU group synchronized with the PDU group to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the PDU group to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the synchronization PDU group to which the SDAP PDU or SDU belongs; (3) if the SDAP PDU or SDU is the last SDAP PDU or SDU of the PDU group to which the SDAP PDU or SDU belongs, or if the SDAP PDU or SDU is the last SDAP PDU or SDU of the PDU group to which the SDAP PDU or SDU belongs that is indicated as submitted or successfully transmitted, or if the SDAP PDU or SDU is the first or the last SDAP PDU or SDU of the last PDU group of the synchronization PDU group to which the SDAP PDU or SDU belongs that is indicated as submitted or successfully transmitted, stop the synchronization timer associated with the PDU group synchronized with the PDU group to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the PDU group to which the SDAP PDU or SDU belongs, or stop the synchronization timer associated with the synchronization PDU group to which the SDAP PDU or SDU belongs.

10. A user equipment (UE), comprising: a processor; and a memory storing instructions; wherein the instructions, when executed by the processor, perform the synchronization method according to any one of claims 1-9.

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