Method and apparatus for supporting packet discarding at the PDCP layer due to packet loss

Abstract

An embodiment of the present application relates to a method and apparatus for supporting a packet discard operation in a Packet Data Convergence Protocol (PDCP) layer due to packet loss. According to one embodiment of the present application, a PDCP receiving entity includes a processor and a transceiver coupled to the processor, the processor being configured to detect a packet loss or receive parameter information related to a discard operation of the PDCP receiving entity from a PDCP transmitting entity via the transceiver, where the packet loss or discard operation is associated with a packet, and in response to detecting the packet loss or in response to receiving the parameter information, perform a discard operation to discard further packets associated with the packet in a receiving buffer.

Description

[Technical Field]

[0001] FIELD Embodiments of the present application generally relate to wireless communication technologies, and more particularly, to a method and apparatus for supporting packet discarding operations at a Packet Data Convergence Protocol (PDCP) layer due to packet loss. [Background technology]

[0002] Extended reality (XR), which encompasses augmented reality (AR) and virtual reality (VR), as well as cloud gaming (CG), presents a promising new category of connected devices, applications, and services. As a potential work area in 3GPP (3rd generation partnership project) Rel-18, application and traffic awareness in the radio access network (RAN) is one of the key capabilities for improving user experience of XR services.

[0003] XR services require high bitrates with bounded latency. Applications typically require a minimum granularity of application data available on the client side before the next level of processing can begin. This minimum granularity of application data is called an application data unit (ADU). Due to the high bitrate, large ADUs may be transmitted in multiple IP packets. When these IP packets arrive at the RAN, the RAN treats all packets as if they are uncorrelated with each other. In some embodiments, an ADU represents a group of pictures (GOP) for video services. A GOP is grouped in a way that improves the visual outcome of a video sequence. A GOP may contain various types of pictures, such as intra-coded pictures (I-frames), predictively coded pictures (P-frames), or B-predictively coded pictures (B-frames). The encoder uses groups of pictures and other tools to render smooth streaming video. Frame rate and other metrics may also apply.

[0004] Depending on the encoding mechanism, frames within the same ADU or GOP may be correlated with each other. For example, if an I-frame is lost, the user will be unable to decode the subsequent P-frames and B-frames. Meanwhile, due to the nature of wireless communication, packet loss may occur in UL or DL ​​transmission. To simplify data processing at the transmitter or receiver, when a critical packet (e.g., an I-frame within one ADU / GOP) is lost, it may not be necessary to continue processing other correlated packets (e.g., P-frames, B-frames within the same ADU / GOP).

[0005] In view of the above, it is desirable to provide a mechanism that supports packet discarding operations at the PDCP layer due to packet loss. Summary of the Invention [Means for solving the problem]

[0006] Some embodiments of the present application also provide a Packet Data Convergence Protocol (PDCP) receiving entity, the PDCP receiving entity including a processor and a transceiver coupled to the processor, the processor being configured to detect packet loss or receive, from the PDCP transmitting entity via the transceiver, parameter information regarding a discard operation of the PDCP receiving entity, the parameter information relating to the packet loss or the discard operation being associated with the packet, and to perform a discard operation to discard further packets associated with the packet in a receive buffer in response to detecting the packet loss or receiving the parameter information.

[0007] Some embodiments of the present application provide a method that may be performed by a PDCP receiving entity, the method including detecting packet loss or receiving, from a PDCP transmitting entity, parameter information regarding a discarding operation of the PDCP receiving entity, where the packet loss or discarding operation is associated with a packet, and determining, in response to detecting the packet loss or receiving the parameter information, to perform a discarding operation to discard further packets associated with the packet in a receive buffer.

[0008] Some embodiments of the present application also provide an apparatus for wireless communication, the apparatus including: a non-transitory computer-readable storage medium having computer-executable instructions stored thereon, a receiving circuit, a transmitting circuit, and a processor coupled to the non-transitory computer-readable storage medium, the receiving circuit, and the transmitting circuit, the computer-executable instructions causing the processor to perform any of the above-described methods performed by a PDCP receiving entity.

[0009] Some embodiments of the present application also provide a PDCP transmitting entity that includes a processor and a transceiver coupled to the processor, where the processor is configured to detect packet loss, and to decide to perform a discard operation of the PDCP transmitting entity, or to receive parameter information related to the discard operation of the PDCP transmitting entity from the PDCP receiving entity via the transceiver, where the packet loss or the discard operation is associated with a packet, and to perform a further discard operation in response to detecting the packet loss, in response to deciding to perform the discard operation, or in response to receiving the parameter information, to stop transmission of further packets associated with the packet in a transmission buffer and to discard the further packets.

[0010] Some embodiments of the present application provide a method that may be performed by a PDCP transmitting entity, the method including the steps of detecting packet loss, deciding to perform a discard operation of the PDCP transmitting entity, receiving parameter information related to the discard operation of the PDCP transmitting entity from a PDCP receiving entity, where the packet loss or discard operation is associated with a packet, and performing a further discard operation to stop transmission of further packets associated with the packet in a transmission buffer and discard the further packets in response to detecting the packet loss, or in response to deciding to perform the discard operation, or in response to receiving the parameter information.

[0011] Some embodiments of the present application provide an apparatus, the apparatus including: a non-transitory computer-readable storage medium having computer-executable instructions stored thereon, a receiving circuit, a transmitting circuit, and a processor coupled to the non-transitory computer-readable storage medium, the receiving circuit, and the transmitting circuit, the computer-executable instructions causing the processor to perform the above-described method performed by a PDCP transmitting entity.

[0012] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description and drawings, and from the claims. [Brief explanation of the drawings]

[0013] To explain the manner in which the advantages and features of the present invention can be obtained, the invention will be described by reference to specific embodiments thereof which are illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the invention and are therefore not to be considered limiting of its scope.

[0014] [Figure 1] 1 illustrates a schematic diagram of a wireless communication system according to some embodiments of the present application. [Figure 2] 1 illustrates an exemplary block diagram of an apparatus according to some embodiments of the present application. [Figure 3] 1 illustrates an exemplary flowchart of a packet discard operation according to some embodiments of the present application. [Figure 4] 10 illustrates a further exemplary flowchart for a packet discard operation according to some embodiments of the present application. [Figure 5] 1 illustrates an exemplary flowchart of a packet discarding operation in a PDCP receiving entity according to some embodiments of the present application. [Figure 6] 1 illustrates an exemplary flowchart of a packet discarding operation in a PDCP transmitting entity according to some embodiments of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0015] The detailed description of the accompanying drawings is intended as an illustration of a preferred embodiment of the present application and is not intended to represent the only form in which the present application may be practiced. It should be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present application.

[0016] Reference will now be made in detail to several embodiments of the present invention, examples of which are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided under specific network architectures and new service scenarios, such as Third Generation Partnership Project (3GPP) LTE and LTE advanced, 3GPP 5G NR, 5G-Advanced, and 6G. With the development of network architectures and new service scenarios, it is contemplated that all embodiments of the present application are also applicable to similar technical problems. Furthermore, the terms described in the present application may be changed, but this should not affect the principles of the present application.

[0017] 1 illustrates a schematic diagram of a wireless communication system in accordance with some embodiments of the present application. As shown in FIG. 1, the wireless communication system 100 includes at least one base station (BS) 101 and at least one user equipment (UE) 102. Notably, the wireless communication system 100 includes, for illustrative purposes, one BS 101 and two UEs 102 (e.g., UE 102a and UE 102b). While FIG. 1 illustrates a specific number of BSs and UEs for simplicity, it is contemplated that in some other embodiments of the present application, the wireless communication system 100 may include more or fewer BSs and UEs.

[0018] The wireless communication system 100 is compatible with any type of network capable of transmitting and receiving wireless communication signals, such as a wireless communication network, a cellular network, a time division multiple access (TDMA)-based network, a code division multiple access (CDMA)-based network, an orthogonal frequency division multiple access (OFDMA)-based network, an LTE network, a 3GPP-based network, a 3GPP 5G network, a satellite communication network, a high altitude platform network, and / or other communication networks.

[0019] The BS 101 can communicate with a core network (CN) node (not shown), such as a mobility management entity (MME) or serving gateway (S-GW), mobility and management function (AMF), or user plane function (UPF), via an interface. A BS may also be referred to as an access point, access terminal, base, macrocell, Node B, enhanced Node B (eNB), gNB, home Node B, relay node, or device, or other terminology used in the art. In 5G NR, a BS may also be referred to as a RAN node or network equipment. Each BS can serve multiple UEs within a serving area, such as a cell or cell sector, via wireless communication links. Neighboring BSs can communicate with each other as needed, such as during UE handover procedures.

[0020] The UEs 102, e.g., UEs 102a and 102b, should be understood as any type of terminal device, which may include computing devices such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart televisions (e.g., televisions connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), vehicle-mounted computers, network devices (e.g., routers, switches, and modems), etc. According to an embodiment of the present invention, the UEs 102 may include portable wireless communication devices, smartphones, mobile phones, flip phones, devices with subscriber ID modules, personal computers, selective call receivers, or any other devices capable of sending and receiving communication signals over a wireless network. In some embodiments, the UEs 102 may include wearable devices such as smart watches, fitness bands, and optical head-mounted displays. Furthermore, the UEs 102 may be referred to as subscriber units, mobiles, mobile stations, users, terminals, mobile terminals, wireless terminals, fixed terminals, subscriber stations, user terminals, or devices, or may be described using other terms used in the art. The UE 102 can communicate directly with the BS 101 via uplink (UL) communication signals.

[0021] In general, 3GPP standard document TS38.323 defines the data transfer procedures for PDCP transmit and receive operations. For example, when a PDCP SDU is received from a higher layer, the transmitting PDCP entity must start the timer discardTimer associated with this PDCP SDU (if configured). For a PDCP SDU received from a higher layer, the transmitting PDCP entity must associate a COUNT value corresponding to TX_NEXT with this PDCP SDU. When a PDCP data PDU is received from a lower layer, the receiving PDCP entity must determine the COUNT value of the received PDCP data PDU, i.e., RCVD_COUNT. When timer t-Reordering expires, the receiving PDCP entity shall, after header decompression, deliver to the upper layer in ascending order of associated COUNT values: all PDCP SDUs with associated COUNT value < RX_REORD and all PDCP SDUs with associated COUNT values ​​consecutively from RX_REORD; the receiving PDCP entity shall update RX_DELIV to the COUNT value of the first PDCP SDU not yet delivered to the upper layer (COUNT value >= RX_REORD), and if RX_DELIV < RX_NEXT, update RX_REORD to RX_NEXT and start timer t-Reordering.

[0022] Regarding SDU discard behavior, when the PDCP SDU discard timer expires or when a PDCP Status Report confirms successful delivery of the PDCP SDU, the transmitting PDCP entity discards the PDCP SDU along with the corresponding PDCP Data PDU. If the corresponding PDCP Data PDU has already been transmitted to the lower layer, the discard is indicated to the lower layer. In a signaling radio bearer (SRB), when the upper layer requests the discard of a PDCP SDU, the PDCP entity must discard all stored PDCP SDUs and PDCP PDUs.

[0023] Regarding status reporting, for Data Radio Bearers (DRBs) configured by higher layers to send PDCP status reports in the uplink (statusReportRequired in 3GPP TS38.331 [3]), the receiving PDCP entity MUST trigger a PDCP status report. During compilation of a PDCP status report, the receiving PDCP entity MUST set the FMC field to RX_DELIV. If RX_DELIV < RX_NEXT, the receiving PDCP entity MUST allocate a Bitmap field with a length equal to the COUNT number of missing PDCP SDUs from the first to the last; the receiving PDCP entity MUST set the Bitmap field to "0" for all PDCP SDUs not received and, optionally, for PDCP SDUs that failed to be decompressed, and the receiving PDCP entity MUST set the Bitmap field to "1" for all received PDCP SDUs. In the case of DRB, upon receiving a PDCP status report on the downlink or sidelink, the transmitting PDCP entity shall consider any PDCP SDU whose bit in the bitmap is set to "1" or whose associated COUNT value is less than the value of the FMC field as successfully delivered and shall discard that PDCP SDU.

[0024] Currently, there is no mechanism to support packet discarding at the PDCP layer due to packet loss. The present invention aims to solve the above-mentioned problem. Specifically, in some embodiments of the present invention, a receiving PDCP entity can detect packet loss and decide to discard some other packets already received in the receive buffer. In some further embodiments of the present application, a transmitting PDCP entity can be notified by a peer receiving PDCP entity about the packet discard decision and stop transmitting the associated packets. In some other embodiments of the present application, a transmitting PDCP entity may decide to discard some packets and stop transmission and notify the receiving PDCP entity. In some other embodiments of the present application, the PDCP packet discarding operation can be performed based on the COUNT value, an offset value related to the COUNT value, an ADU index, the number of units, and / or importance level information included in the PDCP packet header.

[0025] In some cases, a GOP may be considered a type of ADU, and packets belonging to the same ADU may be correlated with each other. In embodiments of the present invention, parameters related to an ADU (e.g., an ADU index value, "ADUIndexToDiscard," etc.) may be replaced with or applied to parameters related to a GOP without departing from the spirit and scope of the present disclosure. For example, in some embodiments, an ADU index value may be changed or modified to a GOP index value. In some embodiments, "ADUIndexToDiscard" may be changed or modified to "GOPIndexToDiscard." In some embodiments, "NumberInUnitToDiscard" associated with an ADU may be changed or modified to "NumberInUnitToDiscard" associated with a GOP. In some embodiments, "ImportanceToDiscard" associated with an ADU may be changed or modified to "ImportanceToDiscard" associated with a GOP. Embodiments involving such parameter changes can also solve the above-mentioned problems.

[0026] The receiving side of a PDCP entity may also be named a "PDCP Rx entity," an "Rx PDCP entity," a "PDCP receiving entity," a "receiving PDCP entity," etc. The transmitting side of a PDCP entity may also be named a "PDCP Tx entity," a "Tx PDCP entity," a "PDCP transmitting entity," a "transmitting PDCP entity," etc.

[0027] Details are described in the following text in combination with the accompanying drawings. Those skilled in the art should be well aware that the terms "a / first", "a / second" and "a / third" are used for clarity of description only and should not be considered as substantial limitations, such as limitations on the sequence.

[0028] 2 is an exemplary block diagram of an apparatus according to some embodiments of the present application. As shown in FIG. 2, the apparatus 200 may include at least one processor 204 and at least one transceiver 202 coupled to the processor 204. The at least one transceiver 202 may be a wired transceiver or a wireless transceiver. The apparatus 200 may be a PDCP receiving entity or a PDCP transmitting entity, as described in the embodiments of FIGS. 5 and 6 below.

[0029] Although elements such as at least one transceiver 202 and processor 204 are described in the singular in this figure, the plural is contemplated unless limitation to the singular is expressly stated. In some embodiments of the present invention, the transceiver 202 may be divided into two devices, such as a receive circuit and a transmit circuit. In some embodiments of the present invention, the apparatus 200 may further include an input device, memory, and / or other components.

[0030] In some embodiments of the present application, the apparatus 200 may be a PDCP receiving entity (e.g., the PDCP Rx entity 510 or the PDCP Rx entity 610 as shown in FIG. 5 or 6). The processor 204 of the PDCP receiving entity may be configured to detect packet loss or receive parameter information related to a discard operation of the PDCP receiving entity via the transceiver 202 from a PDCP transmitting entity (e.g., the PDCP Tx entity 520 or the PDCP Tx entity 620 as shown in FIG. 5 or 6). The packet loss or the discard operation is associated with a packet. The processor 204 of the PDCP receiving entity may be further configured to perform a discard operation to discard further packets associated with the packet in the receive buffer in response to detecting the packet loss or receiving the parameter information.

[0031] In the following text, for simplicity, a packet may be named a "first packet" and a further packet may be named a "second packet". According to some embodiments, the first packet may be at least one of the following: (1) PDCP Packet Data Unit (PDU); (2) PDCP Service Data Unit (SDU). (3) Packets discarded by a PDCP transmitting entity based on the expiration of a timer (e.g., the timer discardTimer).

[0032] According to some embodiments, the second packet is at least one of a PDCP PDDU or a PDCP SDU. In some embodiments, the first packet and the second packet belong to one Application Data Unit (ADU). For example, the first packet and the second packet have the same ADU index value. In some other embodiments, the first packet and the second packet belong to one Group of Pictures (GOP). For example, the first packet and the second packet have the same GOP index value.

[0033] According to some embodiments, the parameter information is transmitted via at least one of Physical Uplink Control Channel (PUCCH) signaling or PDCP control PDUs. The parameter information received by the PDCP receiving entity may include at least one of the following: (1) An index value (denoted as "first index value" for simplicity) of the ADU (denoted as "first ADU" for simplicity) to which the first packet belongs. For example, in the embodiments of Figures 5 and 6, the first index value may be "ADUIndexToDiscard." (2) An index number of the first packet of the packets belonging to the first ADU (for simplicity, referred to as the "first index number"). For example, in the embodiments of Figures 5 and 6, the first index number may be "NumberInUnitToDiscard." (3) A first packet importance level (for simplicity, referred to as the "first importance level"). For example, in the embodiments of Figures 5 and 6, the first importance level may be "ImportanceToDiscard." For example, the first importance level is set by the network node. (4) A count value of the first packet (for simplicity, referred to as a "first count value"). For example, in the embodiments of FIGS. 5 and 6, the first count value may be "CountToDiscard." (5) An offset value associated with the first count value of the first packet (for simplicity, referred to as the "first offset value"). For example, in the embodiments of Figures 5 and 6, the first offset value may be "Offset."

[0034] In some embodiments, in response to receiving parameter information from the PDCP transmitting entity, processor 204 of the PDCP receiving entity may be configured to check whether a first index value of a first ADU to which a first packet belongs (e.g., ADUIndexToDiscard of the first ADU to which the first packet belongs) is equal to the “first index value of the first ADU (e.g., ADUIndexToDiscard).” In response to the second index value of the second ADU being equal to the first index value of the first ADU, processor 204 of the PDCP receiving entity may be configured to discard the second packet in the receive buffer.

[0035] In some further embodiments, while performing a discard operation of the PDCP receiving entity in response to receiving parameter information from the PDCP transmitting entity, and in response to receiving the parameter information including a first index value of the first ADU (e.g., ADUIndexToDiscard) and a first index number of the first packet (e.g., NumberInUnitToDiscard), the processor 204 of the PDCP receiving entity: (1) Check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU"; (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, checking whether the "index number of the second packet of the packet group belonging to the first ADU (for simplicity, referred to as the "second index number")" is greater than the "first index number of the first packet"; (3) Discarding the second packet in the receive buffer in response to the second index number of the second packet being greater than the first index number of the first packet. It may be configured as follows.

[0036] In some other embodiments, while performing a discard operation of the PDCP receiving entity in response to receiving parameter information from the PDCP transmitting entity, and in response to the parameter information including a first index value of the first ADU (e.g., ADUIndexToDiscard) and a first importance level of the first packet (e.g., ImportanceToDiscard), the processor 204 of the PDCP receiving entity: (1) Check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU" (e.g., ADUIndexToDiscard); (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, check whether the "importance level of the second packet (for simplicity, referred to as the "second importance level")" is less than the "first importance level of the first packet" (e.g., ImportanceToDiscard); (3) discarding the second packet in the receive buffer in response to the second importance level of the second packet being less than the first importance level of the first packet; It may be configured as follows.

[0037] In some additional embodiments, while performing a discard operation of the PDCP receiving entity in response to receiving parameter information from the PDCP transmitting entity, and in response to the parameter information including a first count value (e.g., CountToDiscard) of a first packet and a first offset value (e.g., Offset) related to the first count value, the processor 204 of the PDCP receiving entity: (1) Check whether the count value of the second packet (for simplicity, referred to as the "second count value") is greater than the first count value of the first packet (e.g., COUNT > CountToDiscard); (2) in response to the second count value of the second packet being greater than the first count value of the first packet, checking whether the "second count value of the second packet minus a first offset value associated with the first count value" is less than or equal to the "first count value of the first packet" (e.g., "Count-Offset"<=CountToDiscard); (3) Discarding the second packet in the receive buffer in response to the "value obtained by subtracting the first offset value from the second count value of the second packet" being equal to or less than the "first count value of the first packet." It may be configured as follows.

[0038] In still some additional embodiments, while performing a discard operation of the PDCP receiving entity in response to receiving parameter information from the PDCP transmitting entity, and in response to the parameter information including a first count value (e.g., CountToDiscard) of the first packet, the processor 204 of the PDCP receiving entity: (1) determining a "second count value of the second packet" and an "offset value associated with the second count value (referred to as a "second offset value" for simplicity)" based on packet header information of the second packet; (2) Check whether the "second count value of the second packet" is greater than the "first count value of the first packet" (e.g., COUNT > CountToDiscard); (3) in response to the second count value of the second packet being greater than the first count value of the first packet, checking whether the "second count value of the second packet minus a second offset value associated with the second count value" is less than or equal to the "first count value of the first packet" (e.g., "Count-Offset" <= CountToDiscard); (4) Discarding the second packet in the receive buffer in response to the "value obtained by subtracting the second offset value from the second count value of the second packet" being equal to or less than the "first count value of the first packet." It may be configured as follows.

[0039] According to some embodiments, while performing the discard operation of the PDCP receiving entity in response to detecting a packet loss associated with the first packet, the processor 204 of the PDCP receiving entity: (1) checking whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU to which the first packet belongs"; (2) discarding a second packet in the receive buffer in response to the second index value of the second ADU being equal to the first index value of the first ADU; It may be configured as follows.

[0040] According to some further embodiments, while performing the discard operation of the PDCP receiving entity in response to detecting a packet loss associated with the first packet, the processor 204 of the PDCP receiving entity: (1) checking whether a "second index value of the second ADU to which the second packet belongs" is equal to a "first index value of the first ADU to which the first packet belongs"; (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, checking whether the "second index number of the second packet in the packet group belonging to the first ADU" is greater than the "first index number of the first packet in the packet group belonging to the first ADU"; (3) Discarding the second packet in the receive buffer in response to the second index number of the second packet being greater than the first index number of the first packet. It may be configured as follows.

[0041] According to some other embodiments, while performing the discard operation of the PDCP receiving entity in response to detecting a packet loss associated with the first packet, the processor 204 of the PDCP receiving entity: (1) checking whether a "second index value of the second ADU to which the second packet belongs" is equal to a "first index value of the first ADU to which the first packet belongs"; (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, checking whether the "second importance level of the second packet" is less than the "first importance level of the first packet"; (3) discarding a second packet in the receive buffer in response to the second importance level being less than the first importance level; It may be configured as follows.

[0042] According to some additional embodiments, while performing the discard operation of the PDCP receiving entity in response to detecting a packet loss associated with the first packet, the processor 204 of the PDCP receiving entity: (1) determining a "second count value of the second packet" and a "second offset value associated with the second count value" based on packet header information of the second packet; (2) Check whether the "second count value of the second packet" is greater than the "first count value of the first packet" (e.g., COUNT > CountToDiscard); (3) in response to the second count value being greater than the first count value, checking whether the "second count value minus the second offset value" is less than or equal to the "first count value" (e.g., "Count-Offset" <= CountToDiscard); (4) Discarding a second packet in the receive buffer in response to the value obtained by subtracting the second offset value from the second count value being equal to or less than the first count value. It may be configured as follows.

[0043] According to some embodiments, the processor 204 of the PDCP receiving entity may be configured to generate further parameter information regarding a discard operation of the PDCP transmitting entity and transmit the further parameter information to the PDCP transmitting entity via the transceiver 202. The further discard operation is associated with the first packet. The further parameter information may be conveyed via PUCCH signaling or at least one of a PDCP control PDU. The further parameter information may include: (1) The greatest between the "first index value of the first ADU" and the "second index value of the second ADU"; (2) The largest among the "first index number of the first packet" and the "second index number of the second packet"; (3) the greatest between the "first importance level of the first packet" and the "second importance level of the second packet"; (4) the largest value between the "first count value of the first packet" and the "second count value of the second packet"; or (5) a second offset value associated with the second count value of the second packet; It may include at least one of:

[0044] According to some embodiments, in response to discarding the second packet in the receive buffer, the processor 204 of the PDCP receiving entity: (1) setting a receive state variable (e.g., RX_DELIV in the embodiments of FIGS. 5 and 6) to a count value of PDCP SDUs that have not been delivered to upper layers and that have not been discarded by the PDCP receiving entity (where the PDCP SDU count value is greater than or equal to the receive state variable associated with the reordering timer (e.g., COUNT value >= RX_REORD); or (2) updating the next receive state variable (e.g., RX_NEXT in the embodiment of FIGS. 5 and 6) to the count value following the highest count value among the remaining packets in the receive buffer; or (3) updating the receive state variable associated with the reordering timer (e.g., RX_REORD) to the next receive state variable (e.g., RX_NEXT) in response to the receive state variable being less than the next receive state variable (e.g., RX_DELIV < RX_NEXT); The device may be configured to perform at least one of the following:

[0045] According to some embodiments, the processor 204 of the PDCP receiving entity: (1) in response to receiving a third packet from the PDCP transmitting entity, checking whether the index value (for simplicity, marked as a "third index value") of another ADU (for simplicity, marked as a "third ADU") to which the other packet (for simplicity, marked as a "third packet") belongs is equal to the first index value (e.g., ADUIndexToDiscard) of the first ADU to which the first packet belongs; (2) In response to the third index value of the third ADU being equal to the first index value of the first ADU, the third packet is not stored in the receive buffer and the third packet is discarded. It may be configured as follows.

[0046] According to some other embodiments, the processor 204 of the PDCP receiving entity: (1) in response to receiving a third packet from the PDCP transmitting entity, determining whether a "third index value of a third ADU to which the third packet belongs" is equal to a "first index value of a first ADU to which the first packet belongs"; (2) in response to the third index value of the third ADU being equal to the first index value of the first ADU, check whether the "index number of the third packet in the packet group belonging to the third ADU (for simplicity, referred to as the "third index number")" is greater than the "first index number of the first packet in the packet group belonging to the first ADU"; (3) In response to the third index number of the third packet being greater than the first index number of the first packet, not storing the third packet in the receive buffer and discarding the third packet. It may be configured as follows.

[0047] According to some further embodiments, the processor 204 of the PDCP receiving entity: (1) in response to receiving a third packet from the PDCP transmitting entity, checking whether a "third index value of a third ADU to which the third packet belongs" is equal to a "first index value of a first ADU to which the first packet belongs"; (2) in response to the third index value of the third ADU being equal to the first index value of the first ADU, checking whether the "importance level of the third packet (denoted as "third importance level" for simplicity)" is less than the "first importance level of the first packet"; (3) in response to the third importance level being less than the first importance level, not storing the third packet in the receive buffer and discarding the third packet; It may be configured as follows.

[0048] According to some additional embodiments, the processor 204 of the PDCP receiving entity: (1) in response to receiving a third packet from the PDCP transmitting entity, determining, based on packet header information of the third packet, a count value of the third packet (referred to as a "third count value" for simplicity) and an offset value associated with the third count value (referred to as a "third offset value" for simplicity); (2) checking whether the "third count value of the third packet" is greater than the "first count value of the first packet"; (3) in response to the third count value being greater than the first count value, checking whether the "third count value minus the third offset value" is less than or equal to the first count value of the first packet; (4) If the value obtained by subtracting the third offset value from the third count value is equal to or less than the first count value, the third packet is not stored in the receive buffer and the third packet is discarded. It may be configured as follows.

[0049] According to some additional embodiments, the processor 204 of the PDCP receiving entity: (1) in response to receiving a third packet from the PDCP transmitting entity, determining a "third count value for the third packet" based on packet header information of the third packet; (2) checking whether the "third count value of the third packet" is greater than the "first count value of the first packet"; (3) in response to the third count value being greater than the first count value and in response to first parameter information including a first offset value associated with the first count value of the first packet, checking whether the "third count value minus the first offset value associated with the first count value of the first packet" is less than or equal to the "first count value of the first packet"; (4) In response to the fact that the value obtained by subtracting the first offset value from the third count value is equal to or less than the first count value, the third packet is not stored in the receive buffer and the third packet is discarded. It may be configured as follows.

[0050] According to some additional embodiments, the processor 204 of the PDCP receiving entity may be configured to receive, via the transceiver 202, configuration information from the network node regarding whether the PDCP receiving entity's discard operation is supported for the radio bearer.

[0051] In some embodiments of the present application, the apparatus 200 may be a PDCP transmitting entity (eg, the PDCP Tx entity 520 or the PDCP Tx entity 620 as shown and illustrated in FIG. 5 or FIG. 6). The PDCP transmitting entity processor 204 may be configured to detect packet loss and decide to perform a discard operation of the PDCP transmitting entity, or to receive parameter information related to the discard operation of the PDCP transmitting entity from a PDCP receiving entity (e.g., the PDCP Rx entity 510 or the PDCP Rx entity 610 (as shown in FIG. 5 or FIG. 6 ) via the transceiver 202). The PDCP transmitting entity processor 204 may be further configured to stop transmission of a further packet (referred to as a “second packet” for simplicity) related to the packet in the transmission buffer and perform a further discard operation to discard the further packet in response to detecting packet loss, or in response to deciding to perform a discard operation, or in response to receiving the parameter information. The parameter information may be conveyed via at least one of PUCCH signaling or a PDCP control PDU. A specific example is described below in the embodiments of FIGS. 5 and 6 .

[0052] According to some embodiments, the first packet is at least one of (1) a PDCP PDU, (2) a PDCP SDU, or (3) a packet discarded by the PDCP transmitting entity based on expiration of a timer (e.g., timer discardTimer). According to some embodiments, the second packet is at least one of a PDCP PDU or a PDCP SDU. In some embodiments, the first packet and the second packet belong to one ADU or one GOP. For example, the first packet and the second packet have the same ADU index value or the same GOP index value.

[0053] According to some embodiments, the processor 204 of the PDCP transmitting entity may be configured to receive configuration information regarding whether further discard operations of the PDCP transmitting entity are supported for a radio bearer from the network node via the transceiver 202. In some embodiments, no out-of-order delivery variable (e.g., outOfOrderDelivery) is configured for the radio bearer.

[0054] According to some embodiments, in response to detecting a packet loss associated with the first packet or in response to deciding to perform a discarding operation, while performing a further discarding operation of the PDCP transmitting entity, the processor 204 of the PDCP transmitting entity: (1) Check whether the index value (marked as "second index value" for simplicity) of the ADU to which the second packet belongs (marked as "second ADU" for simplicity) is equal to the "first index value of the first ADU to which the first packet belongs" (e.g., ADUIndexToDiscard); (2) discarding a second packet in the transmit buffer in response to the second index value of the second ADU being equal to the first index value of the first ADU; It may be configured as follows.

[0055] According to some embodiments, in response to detecting a packet loss associated with the first packet or in response to deciding to perform a discarding operation, while performing a further discarding operation of the PDCP transmitting entity, the processor 204 of the PDCP transmitting entity: (1) Check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU to which the first packet belongs" (e.g., ADUIndexToDiscard); (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, check whether the "index number of the second packet of the packet group belonging to the first ADU (for simplicity, referred to as the "second index number")" is greater than the "first index number of the first packet of the packet group belonging to the first ADU" (e.g., NumberInUnitToDiscard); (3) Discarding the second packet in the transmit buffer in response to the second index number of the second packet being greater than the first index number of the first packet. It may be configured as follows.

[0056] According to some embodiments, in response to detecting a packet loss associated with the first packet or in response to deciding to perform a discarding operation, while performing a further discarding operation of the PDCP transmitting entity, the processor 204 of the PDCP transmitting entity: (1) Check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU to which the first packet belongs" (e.g., ADUIndexToDiscard); (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, check whether the "importance level of the second packet (for simplicity, referred to as the "second importance level")" is less than the "first importance level of the first packet" (e.g., ImportanceToDiscard); (3) discarding a second packet in the transmit buffer in response to the second importance level being less than the first importance level; It may be configured as follows.

[0057] According to some embodiments, in response to detecting a packet loss associated with the first packet or in response to deciding to perform a discarding operation, while performing a further discarding operation of the PDCP transmitting entity, the processor 204 of the PDCP transmitting entity: (1) determining a count value of the second packet (for simplicity, referred to as a "second count value") and an offset value associated with the second count value (for simplicity, referred to as a "second offset value") based on packet header information of the second packet; (2) Check whether the "second count value of the second packet" is greater than the "first count value of the first packet" (e.g., COUNT > CountToDiscard); (3) in response to the second count value being greater than the first count value, checking whether the "second count value minus a second offset value associated with the second count value" is less than or equal to the "first count value of the first packet" (e.g., "Count-Offset" <= CountToDiscard); (4) Discarding a second packet in the transmit buffer in response to the second count value being equal to or less than the first count value. It may be configured as follows.

[0058] According to some embodiments, the processor 204 of the PDCP transmitting entity may be configured to transmit, via the transceiver 202, to the PDCP receiving entity, further parameter information regarding the discard behavior of the PDCP receiving entity, the discard behavior of the PDCP receiving entity being associated with the first packet. The further parameter information may be conveyed via at least one of PUCCH signaling or a PDCP control PDU. The further parameter information may include: (1) the second index value of the second ADU to which the second packet belongs; (2) the second index number of the second packet; (3) a second importance level for the second packet; (4) a second count value for a second packet; or (5) a second offset value associated with the second count value; It may include at least one of the following.

[0059] According to some embodiments, the processor 204 of the PDCP transmitting entity is configured to determine to perform a discard operation based on expiration of a discard timer (e.g., discardTimer) for the first packet. According to some embodiments, the processor 204 of the PDCP transmitting entity is configured to detect packet loss associated with the first packet based on receipt of a PDCP status report indicating packet loss for the first packet.

[0060] According to some embodiments, the parameter information received by the PDCP transmitting entity comprises: (1) The index value (e.g., "ADUIndexToDiscard" in the embodiment of FIGS. 5 and 6) of the ADU to which the first packet belongs (denoted as "first index value" for simplicity). (2) The index number of the first packet of the packet group belonging to the first ADU (for simplicity, referred to as the "first index number"), for example, "NumberInUnitToDiscard" in the embodiments of FIGS. (3) A first packet importance level (referred to as "first importance level" for simplicity), e.g., "ImportanceToDiscard" in the embodiments of Figures 5 and 6. For example, the importance level is set by a network node. (4) A count value of the first packet (for simplicity, referred to as a "first count value"), for example, "CountToDiscard" in the embodiment of FIGS. (5) An offset value associated with the first count value of the first packet (for simplicity, referred to as the "first offset value"), for example, "Offset" in the embodiment of FIGS. Contains at least one of the following:

[0061] In some embodiments, while performing a further discard operation of the PDCP transmitting entity in response to receiving parameter information from the PDCP receiving entity, and in response to the parameter information including a first index value of the first ADU (e.g., ADUIndexToDiscard), the processor 204 of the PDCP transmitting entity: (1) Check whether the index value (marked as "second index value" for simplicity) of the ADU to which the second packet belongs (marked as "second ADU" for simplicity) is equal to the "first index value of the first ADU" (e.g., ADUIndexToDiscard); (2) discarding a second packet in the transmit buffer in response to the second index value of the second ADU being equal to the first index value of the first ADU; It may be configured as follows.

[0062] In some embodiments, while performing a further discard operation of the PDCP transmitting entity in response to receiving parameter information from the PDCP receiving entity and in response to receiving the parameter information including a first index value of the first ADU (e.g., ADUIndexToDiscard) and a first index number of the first packet (e.g., NumberInUnitToDiscard), the processor 204 of the PDCP transmitting entity: (1) Check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU" (e.g., ADUIndexToDiscard); (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, check whether the "index number of the second packet of the packet group belonging to the first ADU (for simplicity, referred to as the "second index number")" is greater than the "first index number of the first packet" (e.g., NumberInUnitToDiscard); (3) Discarding the second packet in the transmit buffer in response to the second index number of the second packet being greater than the first index number of the first packet. It may be configured as follows.

[0063] In some embodiments, while performing a further discard operation of the PDCP transmitting entity in response to receiving parameter information from the PDCP receiving entity, and in response to receiving the parameter information including a first index value of the first ADU (e.g., ADUIndexToDiscard) and a first importance level of the first packet (e.g., ImportanceToDiscard), the processor 204 of the PDCP transmitting entity: (1) Check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU" (e.g., ADUIndexToDiscard); (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, check whether the "importance level of the second packet (for simplicity, referred to as the "second importance level")" is less than the "first importance level of the first packet" (e.g., ImportanceToDiscard); (3) discarding a second packet in the transmit buffer in response to the second importance level being less than the first importance level; It may be configured as follows.

[0064] In some embodiments, while performing a further discard operation of the PDCP transmitting entity in response to receiving parameter information from the PDCP receiving entity, and in response to the parameter information including a first count value (e.g., CountToDiscard) of the first packet and a first offset value (e.g., Offset) related to the first count value, the processor 204 of the PDCP transmitting entity: (1) Check whether the "count value of the second packet (for simplicity, we will refer to it as the "second count value")" is greater than the "first count value of the first packet" (e.g., COUNT > CountToDiscard); (2) in response to the second count value being greater than the first count value, checking whether the "second count value minus a first offset value associated with the first count value" is less than or equal to the first count value (e.g., "Count - Offset" <= CountToDiscard); (3) Discarding a second packet in the transmit buffer in response to the value obtained by subtracting the first offset value from the second count value being equal to or less than the first count value. It may be configured as follows.

[0065] In some embodiments, while performing a further discard operation of the PDCP transmitting entity in response to receiving parameter information from the PDCP receiving entity, and in response to the parameter information including a first count value (e.g., CountToDiscard) of the first packet, the processor 204 of the PDCP transmitting entity: (1) determining a second count value of the second packet and a second offset value associated with the second count value based on packet header information of the second packet; (2) checking whether the "second count value of the second packet" is greater than the "first count value of the first packet"; (3) in response to the second count value being greater than the first count value, checking whether the "second count value minus a second offset value associated with the second count value" is less than or equal to the "first count value of the first packet"; (4) Discarding the second packet in the transmit buffer in response to the "value obtained by subtracting the second offset value from the second count value" being equal to or less than the "first count value of the first packet." It may be configured as follows.

[0066] In some embodiments of the present application, the apparatus 200 may include at least one non-transitory computer-readable storage medium. In some embodiments of the present disclosure, the non-transitory computer-readable storage medium may have computer-executable instructions stored thereon for causing a processor to implement a method related to a PDCP receiving entity or a PDCP transmitting entity described above. For example, the computer-executable instructions, when executed, cause the processor 204, which interacts with the transceiver 202, to perform operations of a method such as those described with reference to FIGS. 3-6.

[0067] 3 shows an example flowchart of a packet discarding operation according to some embodiments of the present invention. Method 300 may be performed by a PDCP receiving entity (e.g., PDCP Rx entity 510 or PDCP Rx entity 610 as shown and illustrated in FIG. 5 or 6). Although described with respect to a PDCP receiving entity, it should be understood that other devices may also be configured to perform the method as shown and illustrated in FIG.

[0068] In the exemplary method 300 shown in FIG. 3, in operation 301, a PDCP receiving entity (e.g., PDCP Rx entity 510 as shown and illustrated in FIG. 5) detects packet loss or receives parameter information related to the PDCP receiving entity's discard operation from a PDCP transmitting entity (e.g., PDCP Tx entity 520 as shown and illustrated in FIG. 5). The packet loss or discard operation is associated with a packet (referred to as a "first packet" for simplicity). In operation 302, the PDCP receiving entity, in response to detecting the packet loss or receiving the parameter information from the PDCP transmitting entity, determines to perform a discard operation to discard a further packet (referred to as a "second packet" for simplicity) related to the first packet in the receive buffer. Specific examples are described below in the embodiments of FIGS. 5 and 6.

[0069] According to some embodiments of the method 300 shown in FIG. 3, the first packet may be at least one of (1) a PDCP PDU, (2) a PDCP SDU, or (3) a packet discarded by the PDCP transmitting entity based on a timer expiration (e.g., the timer discardTimer). The second packet is at least one of a PDCP PDU or a PDCP SDU. In some embodiments, the first packet and the second packet belong to one ADU, e.g., the first packet and the second packet have the same ADU index value. In other embodiments, the first packet and the second packet belong to one GOP, e.g., the first packet and the second packet have the same GOP index value.

[0070] According to some embodiments of the method 300 shown in Figure 3, the parameter information may be conveyed via at least one of PUCCH signaling or PDCP control PDUs. The parameter information received by the PDCP receiving entity may include at least one of the following parameters: (1) The index value (e.g., "ADUIndexToDiscard" in the embodiment of FIGS. 5 and 6) of the ADU to which the first packet belongs (denoted as "first index value" for simplicity). (2) The index number of the first packet of the packet group belonging to the first ADU (for simplicity, referred to as the "first index number"), for example, "NumberInUnitToDiscard" in the embodiments of FIGS. (3) A first packet importance level (referred to as "first importance level" for simplicity), e.g., "ImportanceToDiscard" in the embodiments of Figures 5 and 6. For example, the first importance level is set by a network node. (4) A count value of the first packet (for simplicity, referred to as a "first count value"), for example, "CountToDiscard" in the embodiment of FIGS. (5) An offset value associated with the first count value of the first packet (for simplicity, referred to as the "first offset value"), for example, "Offset" in the embodiment of FIGS.

[0071] 3, in response to receiving the parameter information from the PDCP transmitting entity, and during execution of the discard operation, the PDCP receiving entity further checks whether the first index value of the first ADU to which the first packet belongs (e.g., ADUIndexToDiscard of the first ADU to which the first packet belongs) is equal to the "first index value of the first ADU" (e.g., ADUIndexToDiscard). In response to the second index value of the second ADU being equal to the first index value of the first ADU, the PDCP receiving entity may discard the second packet in the receive buffer.

[0072] In some further embodiments of the method 300 shown in FIG. 3 , while performing the discard operation in response to receiving parameter information from the PDCP transmitting entity, and in response to the parameter information including a first index value of the first ADU (e.g., ADUIndexToDiscard) and a first index number of the first packet (e.g., NumberInUnitToDiscard), the PDCP receiving entity: (1) may check whether a second index value of a second ADU to which the second packet belongs is equal to a first index value of the first ADU; (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, checking whether the "index number of the second packet of the packet group belonging to the first ADU (for simplicity, referred to as the "second index number")" is greater than the "first index number of the first packet"; (3) In response to the second index number of the second packet being greater than the first index number of the first packet, the second packet in the receive buffer may be discarded.

[0073] In some other embodiments of the method 300 shown in FIG. 3 , while performing a discard operation of the PDCP receiving entity in response to receiving parameter information from the PDCP transmitting entity, and in response to the parameter information including a first index value of the first ADU (e.g., ADUIndexToDiscard) and a first importance level of the first packet (e.g., ImportanceToDiscard), the PDCP receiving entity: (1) It may check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU" (e.g., ADUIndexToDiscard); (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, it may check whether the "importance level of the second packet (for simplicity, referred to as the "second importance level")" is less than the "first importance level of the first packet" (e.g., ImportanceToDiscard); (3) In response to the second importance level of the second packet being less than the first importance level of the first packet, the second packet in the receive buffer may be discarded.

[0074] In some additional embodiments of the method 300 shown in FIG. 3 , while performing a discard operation of the PDCP receiving entity in response to receiving parameter information from the PDCP transmitting entity, and in response to the parameter information including a first count value (e.g., CountToDiscard) of the first packet and a first offset value (e.g., Offset) related to the first count value, the PDCP receiving entity: (1) It may check whether the count value of the second packet (for simplicity, referred to as the "second count value") is greater than the first count value of the first packet (e.g., COUNT > CountToDiscard); (2) In response to the second count value of the second packet being greater than the first count value of the first packet, checking whether the "second count value of the second packet minus a first offset value associated with the first count value" is less than or equal to the "first count value of the first packet" (e.g., "Count-Offset" <= CountToDiscard); (3) In response to the "value obtained by subtracting the first offset value from the second count value of the second packet" being equal to or less than the first count value of the first packet, the second packet in the receive buffer may be discarded.

[0075] In some additional embodiments of the method 300 shown in FIG. 3, while performing a discard operation of the PDCP receiving entity in response to receiving parameter information from the PDCP transmitting entity, and in response to the parameter information including a first count value (e.g., CountToDiscard) of the first packet, the PDCP receiving entity: (1) may determine a "second count value of the second packet" and an "offset value associated with the second count value (referred to as a "second offset value" for simplicity)" based on packet header information of the second packet; (2) It may check whether the "second count value of the second packet" is greater than the "first count value of the first packet" (e.g., COUNT > CountToDiscard); (3) In response to the second count value of the second packet being greater than the first count value of the first packet, checking whether the "second count value of the second packet minus a second offset value associated with the second count value" is less than or equal to the "first count value of the first packet" (e.g., "Count-Offset" <= CountToDiscard); (4) In response to the "value obtained by subtracting the second offset value from the second count value of the second packet" being less than or equal to the "first count value of the first packet," the second packet in the receive buffer may be discarded.

[0076] According to some embodiments of the method 300 shown in FIG. 3, while performing a discard operation of the PDCP receiving entity in response to detecting a packet loss associated with the first packet, the PDCP receiving entity: (1) may check whether a "second index value of the second ADU to which the second packet belongs" is equal to a "first index value of the first ADU to which the first packet belongs"; (2) In response to the second index value of the second ADU being equal to the first index value of the first ADU, the second packet in the receive buffer may be discarded.

[0077] According to some further embodiments of the method 300 shown in FIG. 3, while performing the discard operation of the PDCP receiving entity in response to detecting packet loss associated with the first packet, the PDCP receiving entity: (1) may check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU to which the first packet belongs"; (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, checking whether the “second index number of the second packet in the group of packets belonging to the first ADU” is greater than the “first index number of the first packet in the group of packets belonging to the first ADU”; (3) In response to the second index number of the second packet being greater than the first index number of the first packet, the second packet in the receive buffer may be discarded.

[0078] According to some other embodiments of the method 300 shown in FIG. 3, in response to detecting a packet loss associated with the first packet during execution of a discard operation of the PDCP receiving entity, the PDCP receiving entity: (1) may check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU to which the first packet belongs"; (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, checking whether the “second importance level of the second packet” is less than the “first importance level of the first packet”; (3) In response to the second importance level being less than the first importance level, a second packet in the receive buffer may be discarded.

[0079] According to some additional embodiments of the method 300 shown in FIG. 3, in response to detecting a packet loss associated with the first packet during execution of a discard operation of the PDCP receiving entity, the PDCP receiving entity: (1) may determine a “second count value of the second packet” and a “second offset value associated with the second count value” based on packet header information of the second packet; (2) It may check whether the "second count value of the second packet" is greater than the "first count value of the first packet" (e.g., COUNT > CountToDiscard); (3) In response to the second count value being greater than the first count value, it may check whether the "second count value minus the second offset value" is less than or equal to the "first count value" (e.g., "Count-Offset" <= CountToDiscard); (4) In response to the "value obtained by subtracting the second offset value from the second count value" being equal to or less than the first count value, the second packet in the receive buffer may be discarded.

[0080] According to some embodiments of the method 300 shown in FIG. 3, the PDCP receiving entity may generate further parameter information regarding a discard operation of the PDCP transmitting entity and transmit the further parameter information to the PDCP transmitting entity. The further discard operation is associated with the first packet. The further parameter information is conveyed via at least one of PUCCH signaling or a PDCP control PDU. The further parameter information may include: (1) The greatest value between the "first index value of the first ADU" and the "second index value of the second ADU"; (2) The largest among the "first index number of the first packet" and the "second index number of the second packet"; (3) the greatest between the "first importance level of the first packet" and the "second importance level of the second packet"; (4) The maximum of the first count value of the first packet and the second count value of the second packet; or (5) a second offset value associated with the second count value of the second packet; may include at least one of:

[0081] According to some embodiments of the method 300 shown in FIG. 3, in response to discarding the second packet in the receive buffer, the PDCP receiving entity: (1) setting a receive state variable (e.g., RX_DELIV in the embodiments of FIGS. 5 and 6) to a count value of PDCP SDUs that have not been delivered to upper layers and that have not been discarded at the PDCP receiving entity (where the PDCP SDU count value is greater than or equal to the receive state variable associated with the reordering timer (e.g., COUNT value >= RX_REORD); or (2) updating the next receive state variable (e.g., RX_NEXT in the embodiments of FIGS. 5 and 6) to the count value following the highest count value among the remaining packets in the receive buffer; or (3) updating the receive state variable associated with the reordering timer (e.g., RX_REORD) to the next receive state variable (e.g., RX_NEXT) in response to the receive state variable being less than the next receive state variable (e.g., RX_DELIV < RX_NEXT); At least one of the following may be performed.

[0082] According to some embodiments of the method 300 shown in FIG. 3, the PDCP receiving entity: (1) in response to receiving a third packet from the PDCP transmitting entity, checking whether the index value (for simplicity, marked as "third index value") of another ADU (for simplicity, marked as "third ADU") to which the other packet (for simplicity, marked as "third packet") belongs is equal to the first index value (e.g., ADUIndexToDiscard) of the first ADU to which the first packet belongs; (2) In response to the third index value of the third ADU being equal to the first index value of the first ADU, "do not store the third packet in the receive buffer" and "discard the third packet." You may do so.

[0083] According to some other embodiments of the method 300 shown in FIG. 3, the PDCP receiving entity: (1) In response to receiving a third packet from the PDCP transmitting entity, it may check whether the "third index value of the third ADU to which the third packet belongs" is equal to the "first index value of the first ADU to which the first packet belongs" (e.g., ADUIndexToDiscard); (2) In response to the third index value of the third ADU being equal to the first index value of the first ADU, it may check whether the "index number of the third packet of the packet group belonging to the third ADU (for simplicity, referred to as the "third index number")" is greater than the "first index number of the first packet of the packet group belonging to the first ADU" (e.g., NumberInUnitToDiscard); (3) In response to the third index number of the third packet being greater than the first index number of the first packet, the third packet may be stored in the receive buffer and the third packet may be discarded.

[0084] According to some further embodiments of the method 300 shown in FIG. 3, the PDCP receiving entity: (1) in response to receiving a third packet from the PDCP transmitting entity, may check whether the "third index value of the third ADU to which the third packet belongs" is equal to the "first index value of the first ADU to which the first packet belongs"; (2) in response to the third index value of the third ADU being equal to the first index value of the first ADU, checking whether the "importance level of the third packet (denoted as "third importance level" for simplicity)" is less than the "first importance level of the first packet"; (3) In response to the third importance level being lower than the first importance level, the third packet may not be stored in the receiving buffer, but may be discarded.

[0085] According to some additional embodiments of the method 300 shown in FIG. 3, the PDCP receiving entity: (1) in response to receiving a third packet from the PDCP transmitting entity, determine, based on packet header information of the third packet, a count value for the third packet (referred to for simplicity as a "third count value") and an offset value associated with the third count value (referred to for simplicity as a "third offset value"); (2) checking whether the "count value of the third packet" is greater than the "count value of the first packet"; (3) in response to the third count value being greater than the first count value, checking whether the "third count value minus the third offset value" is less than or equal to the first count value of the first packet; (4) If the "value obtained by subtracting the third offset value from the third count value" is equal to or less than the first count value, the third packet may be discarded without being stored in the receive buffer.

[0086] According to some additional embodiments of the method 300 shown in FIG. 3, the PDCP receiving entity: (1) may, in response to receiving a third packet from the PDCP transmitting entity, determine a “third count value for the third packet” based on packet header information of the third packet; (2) checking whether the "count value of the third packet" is greater than the "count value of the first packet"; (3) in response to the third count value being greater than the first count value and in response to the first parameter information including a first offset value associated with the first count value of the first packet, checking whether the "third count value minus the first offset value associated with the first count value of the first packet" is less than or equal to the "first count value of the first packet"; (4) In response to the "value obtained by subtracting the first offset value from the third count value" being equal to or less than the first count value, the third packet may be discarded without being stored in the receive buffer.

[0087] According to some additional embodiments of the method 300 shown in FIG. 3, the PDCP receiving entity may receive configuration information from the network node regarding whether the PDCP receiving entity's discard operation is supported for the radio bearer.

[0088] It is contemplated that the method 300 illustrated in FIG. 3 may include other operations not shown, such as any of the operations described with respect to FIGS. 2 and 4-6.

[0089] Details described in all other embodiments of the present invention (e.g., details regarding a mechanism for supporting packet discard operations at the PDCP layer due to packet loss) are applicable to the embodiment of Figure 3. Furthermore, details described in the embodiment of Figure 3 are applicable to all embodiments of Figures 1, 2, and 4 to 6. It should be understood by those skilled in the art that the order of operations in the exemplary procedure in the embodiment of Figure 3 may be changed, and some of the operations in the exemplary procedure in the embodiment of Figure 3 may be deleted or modified, without departing from the spirit and scope of the present disclosure.

[0090] 4 shows a further exemplary flowchart for a packet discard operation according to some embodiments of the present invention. The embodiment of FIG. 4 may be performed by a PDCP transmitting entity (e.g., PDCP Tx entity 520 or PDCP Tx entity 620 as shown and illustrated in FIG. 5 or FIG. 6). Although described with respect to a PDCP transmitting entity, it should be understood that other devices may be configured to perform a method similar to FIG. 4.

[0091] In the exemplary method 400 as shown in FIG. 4, in operation 401, a PDCP transmitting entity (e.g., PDCP Tx entity 520 as shown and illustrated in FIG. 5) detects packet loss or receives parameter information related to the PDCP transmitting entity's discard operation from a PDCP receiving entity (e.g., PDCP Rx entity 510 as shown and illustrated in FIG. 5). The packet loss or discard operation is associated with a packet (denoted as a "first packet" for simplicity). As shown in FIG. 4, in operation 402, the PDCP transmitting entity, in response to detecting the packet loss or receiving the parameter information, stops transmitting a further packet (denoted as a "second packet" for simplicity) related to the first packet in the transmission buffer and performs a discard operation to discard the further packet. According to some embodiments of the method 400 shown in FIG. 4, the parameter information may be conveyed via at least one of PUCCH signaling or a PDCP control PDU. Specific examples are described below in the embodiments of FIGS. 5 and 6.

[0092] According to some embodiments of the method 400 shown in FIG. 4, the first packet may be at least one of (1) a PDCP PDU, (2) a PDCP SDU, or (3) a packet discarded by the PDCP transmitting entity based on a timer expiration (e.g., the timer discardTimer). According to some embodiments, the second packet is at least one of a PDCP PDU or a PDCP SDU. In some embodiments, the first packet and the second packet belong to one ADU, e.g., the first packet and the second packet have the same ADU index value. In other embodiments, the first packet and the second packet belong to one GOP, e.g., the first packet and the second packet have the same GOP index value.

[0093] In some embodiments of the method 400 shown in Figure 4, the PDCP transmitting entity may receive configuration information from a network node regarding whether the PDCP transmitting entity's discard behavior is supported for a radio bearer. For example, the radio bearer may not be configured with an out-of-order delivery variable (e.g., outOfOrderDelivery).

[0094] According to some embodiments of the method 400 shown in FIG. 4 , while performing a further discard operation of the PDCP transmitting entity in response to detecting packet loss associated with the first packet or in response to determining to perform a discard operation, the PDCP transmitting entity: (1) It may check whether the index value (marked as "second index value" for simplicity) of the ADU to which the second packet belongs (marked as "second ADU" for simplicity) is equal to the first index value (e.g., ADUIndexToDiscard) of the first ADU to which the first packet belongs; (2) In response to the second index value of the second ADU being equal to the first index value of the first ADU, the second packet in the transmit buffer may be discarded.

[0095] According to some embodiments of the method 400 shown in FIG. 4, while performing a further discard operation of the PDCP transmitting entity in response to detecting a packet loss associated with the first packet, the PDCP transmitting entity: (1) It may check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU to which the first packet belongs" (e.g., ADUIndexToDiscard); (2) In response to the second index value of the second ADU being equal to the first index value of the first ADU, it may check whether the "index number of the second packet of the packet group belonging to the first ADU (for simplicity, referred to as the "second index number")" is greater than the "first index number of the first packet of the packet group belonging to the first ADU" (e.g., NumberInUnitToDiscard); (3) In response to the second index number of the second packet being greater than the first index number of the first packet, the second packet may be discarded in the transmit buffer.

[0096] According to some embodiments of the method 400 shown in FIG. 4, while performing a further discard operation of the PDCP transmitting entity in response to detecting a packet loss associated with the first packet, the PDCP transmitting entity: (1) It may check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU to which the first packet belongs" (e.g., ADUIndexToDiscard); (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, it may check whether the "importance level of the second packet (for simplicity, referred to as the "second importance level")" is less than the "first importance level of the first packet" (e.g., ImportanceToDiscard); (3) In response to the second importance level being less than the first importance level, a second packet in the transmit buffer may be discarded.

[0097] According to some embodiments of the method 400 shown in FIG. 4, while performing a further discard operation of the PDCP transmitting entity in response to detecting a packet loss associated with the first packet, the PDCP transmitting entity: (1) may determine a count value of the second packet (for simplicity, referred to as a "second count value") and an offset value associated with the second count value (for simplicity, referred to as a "second offset value") based on packet header information of the second packet; (2) It may check whether the "second count value of the second packet" is greater than the "first count value of the first packet" (e.g., COUNT > CountToDiscard); (3) in response to the second count value being greater than the first count value, checking whether the "second count value minus a second offset value associated with the second count value" is less than or equal to the "first count value of the first packet" (e.g., "Count-Offset" <= CountToDiscard); (4) In response to the "value obtained by subtracting the second offset value from the second count value" being equal to or less than the first count value, the second packet in the transmission buffer may be discarded.

[0098] According to some embodiments of the method 400 shown in FIG. 4, the PDCP transmitting entity may transmit to the PDCP receiving entity further parameter information regarding the discard behavior of the PDCP receiving entity. The discard behavior of the PDCP receiving entity is associated with the first packet. The further parameter information is conveyed via at least one of PUCCH signaling or a PDCP control PDU. The further parameter information may include at least one of the following: (1) the second index value of the second ADU to which the second packet belongs; (2) the second index number of the second packet; (3) a second importance level for the second packet; (4) a second count value for a second packet; or (5) A second offset value associated with the second count value.

[0099] According to some embodiments of the method 400 shown in Figure 4, the PDCP transmitting entity determines to perform a discard operation based on expiration of a discard timer (e.g., discardTimer) for the first packet. According to some embodiments of the method 400 shown in Figure 4, the PDCP transmitting entity detects packet loss associated with the first packet based on receipt of a PDCP status report indicating packet loss for the first packet.

[0100] According to some embodiments of the method 400 shown in FIG. 4, the parameter information received by the PDCP transmitting entity includes at least one of the following: (1) The index value (e.g., "ADUIndexToDiscard" in the embodiment of FIGS. 5 and 6) of the ADU to which the first packet belongs (denoted as "first index value" for simplicity). (2) The index number of the first packet of the packet group belonging to the first ADU (for simplicity, referred to as the "first index number"), for example, "NumberInUnitToDiscard" in the embodiments of FIGS. (3) A first packet importance level (referred to as "first importance level" for simplicity), e.g., "ImportanceToDiscard" in the embodiments of Figures 5 and 6. For example, the importance level is set by a network node. (4) A count value of the first packet (for simplicity, referred to as a "first count value"), for example, "CountToDiscard" in the embodiment of FIGS. (5) An offset value associated with the first count value of the first packet (for simplicity, referred to as the "first offset value"), for example, "offset" in the embodiment of FIGS.

[0101] In some embodiments of the method 400 shown in FIG. 4 , while performing a further discard operation of the PDCP transmitting entity in response to receiving parameter information from the PDCP receiving entity, and in response to the parameter information including a first index value of the first ADU (e.g., ADUIndexToDiscard), the PDCP transmitting entity: (1) It may check whether the index value (marked as "second index value" for simplicity) of the ADU to which the second packet belongs (marked as "second ADU" for simplicity) is equal to the "first index value of the first ADU" (e.g., ADUIndexToDiscard); (2) In response to the second index value of the second ADU being equal to the first index value of the first ADU, the second packet in the transmit buffer may be discarded.

[0102] In some embodiments of the method 400 shown in FIG. 4 , while performing a further discard operation of the PDCP transmitting entity in response to receiving parameter information from the PDCP receiving entity and in response to receiving the parameter information including a first index value of the first ADU (e.g., ADUIndexToDiscard) and a first index number of the first packet (e.g., NumberInUnitToDiscard), the PDCP transmitting entity: (1) It may check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU" (e.g., ADUIndexToDiscard); (2) In response to the second index value of the second ADU being equal to the first index value of the first ADU, it may check whether the "index number of the second packet of the packet group belonging to the first ADU (for simplicity, referred to as the "second index number")" is greater than the "first index number of the first packet" (e.g., NumberInUnitToDiscard); (3) In response to the second index number of the second packet being greater than the first index number of the first packet, the second packet may be discarded in the transmit buffer.

[0103] In some embodiments of the method 400 shown in FIG. 4 , while performing a further discard operation of the PDCP transmitting entity in response to receiving parameter information from the PDCP receiving entity, and in response to the parameter information including a first index value of the first ADU (e.g., ADUIndexToDiscard) and a first importance level of the first packet (e.g., ImportanceToDiscard), the PDCP transmitting entity: (1) It may check whether the "second index value of the second ADU to which the second packet belongs" is equal to the "first index value of the first ADU" (e.g., ADUIndexToDiscard); (2) in response to the second index value of the second ADU being equal to the first index value of the first ADU, it may check whether the "importance level of the second packet (for simplicity, referred to as the "second importance level")" is less than the "first importance level of the first packet" (e.g., ImportanceToDiscard); (3) In response to the second importance level being less than the first importance level, a second packet in the transmit buffer may be discarded.

[0104] In some embodiments of the method 400 shown in FIG. 4 , while performing a further discard operation of the PDCP transmitting entity in response to receiving parameter information from the PDCP receiving entity, and in response to the parameter information including a first count value (e.g., CountToDiscard) of the first packet and a first offset value (e.g., Offset) related to the first count value, the PDCP transmitting entity: (1) It may check whether the "count value of the second packet (for simplicity, we will refer to it as the 'second count value')" is greater than the "first count value of the first packet" (e.g., COUNT > CountToDiscard); (2) In response to the second count value being greater than the first count value, it may check whether the "second count value minus a first offset value associated with the first count value" is less than or equal to the first count value (e.g., "Count - Offset" <= CountToDiscard); (3) In response to the "value obtained by subtracting the first offset value from the second count value" being equal to or less than the first count value, the second packet in the transmission buffer may be discarded.

[0105] In some embodiments of the method 400 shown in FIG. 4 , while performing a further discard operation of the PDCP transmitting entity in response to receiving parameter information from the PDCP receiving entity, and in response to the parameter information including a first count value (e.g., CountToDiscard) of the first packet, the PDCP transmitting entity: (1) may determine a second count value of the second packet and a second offset value associated with the second count value based on packet header information of the second packet; (2) checking whether the "second count value of the second packet" is greater than the "first count value of the first packet"; (3) in response to the second count value being greater than the first count value, checking whether the "second count value minus a second offset value associated with the second count value" is less than or equal to the "first count value of the first packet"; (4) In response to the "value obtained by subtracting the second offset value from the second count value" being equal to or less than the "first count value of the first packet," the second packet in the transmission buffer may be discarded.

[0106] It is contemplated that the method illustrated in FIG. 4 may include other operations not shown, such as any of the operations described with respect to FIGS.

[0107] Details described in all other embodiments of the present invention (e.g., details regarding the mechanism supporting packet discarding operations at the PDCP layer due to packet loss) are applicable to the embodiment of Figure 4. Furthermore, details described in the embodiment of Figure 4 are applicable to all embodiments of Figures 1-3, 5, and 6. It should be understood by those skilled in the art that the order of operations in the exemplary procedure in the embodiment of Figure 4 may be changed, and some of the operations in the exemplary procedure in the embodiment of Figure 4 may be deleted or modified, without departing from the spirit and scope of the present disclosure.

[0108] 5 and 6 illustrate some specific embodiments of the method as shown and illustrated in FIGS. 2-4. The embodiments of FIGS. 5 and 6 assume that packets are associated with one XR service and are correlated with each other. For example, each packet (i.e., PDCP PDU) is associated with an ADU or GOP index, a subunit number (i.e., the number of frames in the same ADU or GOP), and an importance level. One ADU or GOP has multiple frames that are correlated with each other. Packets belonging to the same ADU or GOP are correlated with each other; for example, if an I-frame packet is lost, the user will not be able to decode the subsequent P-frames and B-frames. Packets belonging to the same ADU or GOP have different importance levels; for example, I-frame packets have a higher importance level than P-frames and B-frames. In the embodiments of FIGS. 5 and 6, the packets may be PDUs, SDUs, or packets discarded by the PDCP transmitting entity based on timer expiration (e.g., timer discardTimer).

[0109] FIG. 5 illustrates an exemplary flowchart of a packet discarding operation in a PDCP receiving entity according to some embodiments of the present application.

[0110] 5, the PDCP Rx entity 510 makes a packet discard decision in step 501. In step 502, the PDCP Rx entity 510 sends "parameter information regarding the discard behavior of the PDCP Tx entity 520" to the PDCP Tx entity 520.

[0111] For example, if the PDCP Rx entity 510 (which may be, for example, a PDCP receiving entity) determines a packet loss or decides to discard an associated received packet in a receiving buffer (which may be named a receiving buffer), the PDCP Rx entity 510 may transmit "parameter information regarding packet loss and discard behavior of the PDCP Rx entity 510" to the PDCP Tx entity 520 (which may be, for example, a PDCP transmitting entity). The parameter information may be transmitted via PUCCH signaling and / or a PDCP control PDU (e.g., a PDCP status report or a new PDCP control PDU). In some embodiments, the parameter information may refer to any of the following: 1) A CountToDiscard value and, optionally, an Offset value relative to the "CountToDiscard" value. 2) An ADUIndexToDiscard value, and optionally, a NumberInUnitToDiscard value or an ImportanceToDiscard value.

[0112] In some embodiments, CountToDiscard, ADUIndexToDiscard, NumberInUnitToDiscard, and / or ImportanceToDiscard are set to values ​​indicated or determined by the PDCP Rx entity 510.

[0113] According to some embodiments of FIG. 5, the PDCP Rx entity 510 determines that a PDCP PDU or PDCP SDU is lost when the timer t-Reordering expires and a PDCP PDU or PDCP SDU with an associated COUNT value < RX_REORD has not yet been found. The PDCP Rx entity 510 may discard one or more received PDCP packets that depend on the lost PDCP packet (e.g., belong to the same ADU or GOP). In these embodiments, the PDCP packet discard operation of the PDCP Rx entity 510 is triggered by the PDCP Rx entity 510.

[0114] In some embodiments of FIG. 5, whether to discard PDCP packets according to lost PDCP packets is permitted for a given data radio bearer configured by a network node. This may also mean whether the PDCP header contains information about correlation with other PDCP packets (e.g., an offset value means depending on the offset number of the previous PDCP packet, the ADU or GOP index, the number within the unit, or importance information). In some embodiments, a radio bearer that allows PDCP packet discarding should not set outoforderdelivery. If outoforderdelivery is set, PDCP SDUs are not buffered in the PDCP Rx entity 510, and therefore PDCP packet discarding is not applicable.

[0115] 5, in step 503, upon receiving the parameter information from the PDCP Rx entity 510, the PDCP Tx entity 520 may discard packets (e.g., PDUs) in the transmit buffer that correlate to the discarded packets indicated by the PDCP Rx entity 510. In such an embodiment, the PDCP packet discard operation of the PDCP Tx entity 520 is triggered by receiving the parameter information from the PDCP Rx entity 510. For example, the PDCP Tx entity 520 may perform one of the following: 1) Stop transmission and discard any remaining packets in the current send buffer with COUNT and Offset values ​​that satisfy 'COUNT' - Offset' <= CountToDiscard (this does not affect packets that may arrive in the future). 2) Stop transmission and discard any remaining packets associated with the same ADU index as ADUIndexToDiscard (including both packets currently in the transmit buffer and packets arriving in the future). 3) If provided, stop transmitting and discard any remaining packets (including both packets currently in the transmit buffer and packets arriving in the future) associated with an ADU index equal to ADUIndexToDiscard and an in-unit number greater than NumberInUnitToDiscard. 4) Stop transmission and discard any remaining packets (including both packets currently in the transmit buffer and packets arriving in the future) associated with the same ADU index as ADUIndexToDiscard and with an importance level lower than ImportanceToDiscard, if provided.

[0116] According to some embodiments of Figure 5, the PDCP data PDU header includes an offset value, which means that the current PDCP packet depends on the offset number of previous PDCP packets, and if the previous offset number of PDCP packets are lost, the current PDCP packet is useless.

[0117] In some embodiments, when a PDCP packet is received from a lower layer, the PDCP Rx entity 510 checks whether the associated COUNT and Offset values ​​satisfy COUNT - Offset <= CountToDiscard. If so, the PDCP Rx entity 510 discards the received PDCP packet and does not place it in the receive buffer.

[0118] According to some embodiments of Figure 5, when the receiving PDCP entity determines packet loss of a PDCP packet associated with "COUNT = CountLost," the PDCP Rx entity 510 discards PDCP packets in the receive buffer with associated COUNT and Offset values ​​that satisfy "COUNT" - "Offset" <= CountLost. For example, if a PDCP data PDU header contains "COUNT value = 100" and "Offset value = 10," loss of a PDCP packet with a COUNT value in the range "90-99" renders the current PDCP PDU useless and can be discarded. The PDCP Rx entity 510 may update CountToDiscard to the maximum COUNT associated with the discarded PDCP packet.

[0119] In some embodiments, upon discarding the PDCP packet from among the PDCP packets remaining in the receive buffer, the PDCP Rx entity 510 may perform one or a combination of the following actions: 1) RX_DELIV is updated to the COUNT value of the first PDCP SDU with a COUNT value >= RX_REORD that has not been delivered to higher layers. 2) RX_NEXT is updated to the COUNT value following the largest COUNT value among the PDCP packets remaining in the receive buffer. 3) If RX_DELIV < RX_NEXT, RX_REORD is updated to RX_NEXT.

[0120] 5, if the lost packet is associated with a particular ADU / GOP indicated by an ADU / GOP index (e.g., ADUIndexToDiscard) and is packet number "N" in the ADU / GOP indicated by a number in units (e.g., NumberInUnitToDiscard), the PDCP Rx entity 510 discards other packets that belong to the same ADU / GOP and (optionally) have numbers in units greater than "N." Information about the lost packet may be indicated by upper layers of the PDCP Rx entity 510 or the PDCP Tx entity 520.

[0121] In some embodiments, when a PDCP packet is received from a lower layer, the PDCP Rx entity 510 checks whether the associated ADU index is equal to ADUIndexToDiscard and (optionally) whether the associated number in units is greater than NumberInUnitToDiscard. If so, the PDCP Rx entity 510 discards the received PDCP packet and does not place it in the receive buffer. One specific embodiment may be as follows: - After determining that the COUNT value of the received PDCP Data PDU is equal to RCVD_COUNT, the PDCP Rx entity 510 -Use COUNT = RCVD_COUNT to decrypt and verify the integrity of PDCP Data PDUs; -If integrity verification fails: -Indicates a failure of integrity verification to higher layers; -Discard the PDCPData PDU and consider it not received; - If the associated ADU index is equal to ADUIndexToDiscard and (optionally) the number in the associated unit is greater than NumberInUnitToDiscard - RCVD_COUNT < RX_DELIV; or -If a PDCPData PDU with COUNT = RCVD_COUNT has been received: -Discard PDCPData PDU

[0122] 5, when the PDCP Rx entity 510 detects a failed PDCP packet reception, when the timer t-Reordering expires, the PDCP Rx entity 510 discards other PDCP packets in the receive buffer that have an ADU index equal to the ADU index associated with the lost PDCP packet and (optionally) an intra-unit number greater than the intra-unit number associated with the lost PDCP packet; the PDCP Rx entity 510 updates the values ​​of ADUIndexToDiscard and NumberInUnitToDiscard. In some embodiments, the value of ADUIndexToDiscard is updated to the highest ADU index associated with the discarded PDCP packet, and the value of NumberInUnitToDiscard is updated to the value of the highest intra-unit number associated with the discarded PDCP packet.

[0123] In some embodiments, upon discarding the PDCP packet from among the PDCP packets remaining in the receive buffer, the PDCP Rx entity 510 may perform one or a combination of the following actions: 1) RX_DELIV is updated to the COUNT value of the first PDCP SDU with a COUNT value >= RX_REORD that has not been delivered to higher layers. 2) Set RX_NEXT to the COUNT value following the largest COUNT value among the PDCP packets remaining in the receive buffer. 3) If RX_DELIV < RX_NEXT, RX_REORD is updated to RX_NEXT.

[0124] Specific embodiments may be as follows: When t-Reordering expires, the PDCP Rx entity 510: - If there is an associated PDCP SUDU with a COUNT value < RX_REORD and it has not yet been found, discard the PDCP SDU in the PDCP receive buffer whose ADU index is equal to ADUIndexToDiscard and (optionally) whose associated unit number is greater than NumberInUnitToDiscard. - After performing header decompression, to the higher layer, in ascending order of the associated COUNT value (if the following operations were not performed before decompression): - all stored PDCP SDUs whose associated COUNT value is < RX_REORD; - all stored PDCP SDUs with consecutively associated COUNT values ​​starting from RX_REORD; will be distributed. - Update RX_DELIV to the COUNT value of the first PDCP SDU that has not been delivered to the upper layer, and the COUNT value >= RX_REORD If -RX_DELIV < RX_NEXT: -Update RX_REORD to RX_NEXT. -t - Start Reordering.

[0125] 5, if a lost packet is associated with a particular ADU / GOP indicated by the ADU / GOP index and has an importance value of "M," the PDCP Rx (receive) entity 510 discards other packets that belong to the same ADU / GOP and have an importance level lower than the importance level "M" of the lost packet. Information about the lost packet may be indicated by upper layers of the PDCP Rx entity 510 or by the PDCP Tx (transmit) entity 520.

[0126] In some embodiments, when a PDCP packet is received from a lower layer, the PDCP Rx entity 510 must check whether the associated ADU index is equal to ADUIndexToDiscard and whether the associated importance level is less than or equal to ImportanceToDiscard. If so, the PDCP Rx entity 510 discards the received PDCP packet and does not place it in the receive buffer.

[0127] In some embodiments, if the receiving PDCP entity detects a failed reception of a PDCP packet upon expiration of timer t-Reordering, the PDCP Rx entity 510 discards other PDCP packets in the receive buffer that have an ADU index equal to the ADU index associated with the lost PDCP packet and a number associated with an importance level less than or equal to ImportanceToDiscard, and the PDCP Rx entity 510 updates the value of ADUIndexToDiscard.

[0128] In an embodiment, the value of ADUIndexToDiscard is updated to the highest ADU index associated with the discarded PDU. In an embodiment, upon discarding the associated PDCP packet among the PDCP packets remaining in the receive buffer, the PDCP Rx entity 510 may perform one or a combination of the following actions: 1) RX_DELIV is updated to the COUNT value of the first PDCP SDU with a COUNT value >= RX_REORD that has not been delivered to higher layers. 2) RX_NEXT is updated to the COUNT value following the largest COUNT value among the PDCP packets remaining in the receive buffer. 3) If RX_DELIV < RX_NEXT, RX_REORD is updated to RX_NEXT.

[0129] Also, the details described in all other embodiments of the present invention (e.g., details related to a mechanism for supporting packet discarding operations in the PDCP layer due to packet loss) are applicable to the embodiment of Fig. 5. Furthermore, the details described in the embodiment of Fig. 5 are applicable to all embodiments of Figs. 1-4 and 6.

[0130] 6 shows an exemplary flowchart of a packet discard operation in a PDCP transmitting entity according to some embodiments of the present invention. As shown in FIG. 6, in step 601, the PDCP Tx entity 620 makes a packet discard decision. In step 602, the PDCP Tx entity 620 sends "parameter information regarding the discard operation of the PDCP Rx entity 610" to the PDCP Rx entity 610. In step 603, the PDCP Rx entity 610 discards the associated packet. In some embodiments, the parameter information may mean any of the following: 1) A CountToDiscard value and, optionally, an Offset value relative to the "CountToDiscard" value. 2) An ADUIndexToDiscard value, and optionally, a NumberInUnitToDiscard value or an ImportanceToDiscard value.

[0131] In some embodiments, CountToDiscard, ADUIndexToDiscard, NumberInUnitToDiscard, and / or ImportanceToDiscard are set to values ​​indicated or determined by the PDCP Tx entity 620.

[0132] 6, when the PDCP Tx entity 620 decides to discard one PDCP packet, the PDCP Tx entity 620 may also discard other associated PDCP packets in its transmit buffer. In some embodiments, whether PDCP packet discarding behavior in the PDCP Tx entity 620 is supported for a radio bearer depends on the network configuration, such that offset and / or ADU / GOP information is carried in the PDCP packet header during transmission.

[0133] According to some embodiments of FIG. 6, the PDCP Tx entity 620 may decide to discard one PDCP packet for any of the following reasons: 1) The timer discardTimer expires for a PDCP SDU (ie, the PDCP Tx entity 620 itself decides to perform a discard action based on the timer discardTimer). 2) The PDCP status report indicates the loss of a PDCP SDU (ie, the PDCP Tx entity 620 itself decides to perform discard action based on the PDCP status report). 3) The PDCP Rx entity 610 triggers a discard operation for the PDCP packet and notifies the PDCP Tx entity 620, for example, as described in the embodiment of FIG. 5 (i.e., the PDCP Tx entity 620 receives parameter information regarding the discard operation from the PDCP Rx entity 610).

[0134] 6, the PDCP Tx entity 620 stops transmitting and discards other packets associated with the discarded one. For example, the PDCP Tx entity 620 may perform any or a combination of the following actions: 1) Stop transmission and discard any remaining packets in the current send buffer whose COUNT and Offset values ​​satisfy 'COUNT - Offset' <= CountToDiscard (this does not affect packets that may arrive in the future). 2) Stop transmission and discard any remaining packets associated with the same ADU index as ADUIndexToDiscard (including both packets currently in the transmit buffer and packets arriving in the future). 3) Stop transmission and discard any remaining packets (including both packets currently in the transmit buffer and packets arriving in the future) that have the same ADU index as ADUIndexToDiscard and an in-unit number greater than NumberInUnitToDiscard, if applicable. 4) Stop transmitting and discard any remaining packets (including both packets currently in the transmit buffer and packets arriving in the future) associated with the same ADU index as ADUIndexToDiscard and with an importance level lower than ImportanceToDiscard (if applicable).

[0135] According to some embodiments of FIG. 6, if the discard operation of a PDCP packet is triggered by the transmitting PDCP entity itself (e.g., when the timer discardTimer expires for a PDCP SDU or when a PDCP status report indicates a missing PDCP SDU), the PDCP Tx entity 620 may perform one or a combination of the following actions: 1) CountToDiscard is set to the COUNT value associated with the PDCP packet in the transmit buffer that triggers the PDCP packet discard operation. 2) ADUIndexToDiscard is set to the ADU index value associated with the PDCP packet in the transmit buffer that triggers the PDCP packet discard operation. 3) NumberInUnitToDiscard is set to the number of the unit value associated with the PDCP packet in the transmit buffer that triggers the PDCP packet discard operation. 4) ImportanceToDiscard is set to the value of the importance level associated with the PDCP packet in the transmit buffer that triggers the discard of the PDCP packet, or to the value of ImportanceToDiscard previously set by the network node.

[0136] 6, upon receiving parameter information regarding PDCP packet discard behavior from the PDCP Tx entity 620, the PDCP Rx entity 610 discards PDCP SDUs in the receive buffer that correlate with the discarded PDCP SDU(s) indicated by the PDCP Tx entity 620. For example, the PDCP Rx entity 610 may: 1) PDCP SDUs in the receive buffer whose COUNT and offset values ​​satisfy 'COUNT' - 'Offset' <= CountToDiscard may be discarded. 2) For PDCP SDUs in the receive buffer, those associated with the same ADU index as ADUIndexToDiscard may be discarded. 3) For PDCP SDUs in the receive buffer, it may discard those associated with the same ADU index as ADUIndexToDiscard and with a unit number greater than NumberInUnitToDiscard (if applicable). 4) For PDCP SDUs in the receive buffer, those associated with the same ADU index as ADUIndexToDiscard and with an importance level lower than ImportanceToDiscard may be discarded (if applicable).

[0137] In some embodiments of FIG. 6, upon discarding the PDCP packet from among the PDCP packets remaining in the receive buffer, the PDCP Rx entity 610 may perform one or a combination of the following actions: (1) RX_DELIV is updated to the COUNT value (COUNT value >= RX_REORD) of the first PDCP SDU that has not been delivered to the upper layer. (2) RX_NEXT is updated to the COUNT value following the largest COUNT value among the PDCP packets remaining in the receive buffer. (3) If RX_DELIV < RX_NEXT, RX_REORD is updated to RX_NEXT.

[0138] Furthermore, the details described in all other embodiments of the present invention (for example, details related to a mechanism for supporting packet discarding operations in the PDCP layer due to packet loss) are applicable to the embodiment of Fig. 6. Furthermore, the details described in the embodiment of Fig. 6 are applicable to all embodiments of Figs. 1 to 5.

[0139] The methods of the present disclosure can be performed on a programmed processor. However, the controllers, flowcharts, and modules can also be implemented in hardware electronic or logical circuitry such as a general-purpose or special-purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, integrated circuits, discrete element circuits, programmable logic devices, etc. In general, any apparatus having a finite state machine capable of implementing the flowcharts shown in the figures can be used to perform the processing functions of the present disclosure.

[0140] While the present disclosure has been described in specific embodiments thereof, it is apparent that many alternatives, modifications, and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be exchanged, added, or substituted in other embodiments. Also, not all elements in the figures are necessary for the operation of the disclosed embodiments. For example, those skilled in the art will be able to make and use the teachings of the present disclosure by simply employing the elements of the independent claims. Accordingly, the embodiments of the present disclosure described herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0141] As used in this document, the terms "comprise," "comprising," or other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements, but may include other elements not expressly listed or inherent in such process, method, article, or apparatus. Elements preceded by "a," "an," etc., do not preclude the presence of additional identical elements in a process, method, article, or apparatus that includes, without more constraints, the element. Also, the term "another" is defined as at least a second or more. As used herein, terms such as "having" are defined as "including."

Claims

1. A Packet Data Convergence Protocol (PDCP) receiving entity, comprising: a processor; a transceiver coupled to the processor; The processor: configured to detect a packet loss or receive, via the transceiver, from a PDCP transmitting entity, first parameter information relating to a first discarding operation of the PDCP receiving entity, the packet loss or the first discarding operation being associated with a first packet; and configured to perform the first discard operation to discard a second packet associated with the first packet in a receive buffer in response to detecting the packet loss or in response to receiving the first parameter information. PDCP receiving entity.

2. The first packet and the second packet belong to one application data unit (ADU) or one group of pictures (GOP).

2. The PDCP receiving entity of claim 1.

3. The first parameter information is a first index value of a first application data unit (ADU) to which the first packet belongs; a first index number of the first packet in a group of packets belonging to the first ADU; a first importance level of the first packet; a first count value of the first packet; or a first offset value associated with the first count value of the first packet; Contains at least one of 2. The PDCP receiving entity of claim 1.

4. While performing the first discard operation in response to receiving the first parameter information and in response to the first parameter information including the first count value of the first packet, the processor of the PDCP receiving entity: determining a second count value for the second packet and a second offset value associated with the second count value based on packet header information of the second packet; checking whether the second count value of the second packet is greater than the first count value of the first packet; in response to the second count value being greater than the first count value, checking whether the second count value minus the second offset value associated with the second count value is less than or equal to the first count value; discarding the second packet in the receive buffer in response to the value obtained by subtracting the second offset value from the second count value being equal to or less than the first count value; It is configured as follows:

4. The PDCP receiving entity of claim 3.

5. In response to detecting the packet loss, while performing the first discarding operation, the processor of the PDCP receiving entity: determining a second count value for the second packet and a second offset value associated with the second count value based on packet header information of the second packet; checking whether the second count value of the second packet is greater than the first count value of the first packet; in response to the second count value being greater than the first count value, checking whether the second count value minus the second offset value is less than or equal to the first count value; discarding the second packet in the receive buffer in response to the value obtained by subtracting the second offset value from the second count value being equal to or less than the first count value; It is configured as follows:

2. The PDCP receiving entity of claim 1.

6. The processor of the PDCP receiving entity: and configured to generate second parameter information related to a second discard operation of the PDCP transmitting entity, the second discard operation being associated with the first packet, the second parameter information comprising: the largest between the first index value of the first ADU and the second index value of the second ADU; the largest between the first index number of the first packet and the second index number of the second packet; the maximum between the first importance level of the first packet and the second importance level of the second packet; the maximum between the first count value of the first packet and the second count value of the second packet; or the second offset value associated with the second count value; and configured to transmit the second parameter information to the PDCP transmitting entity via the transceiver.

6. The PDCP receiving entity of claim 5.

7. The processor of the PDCP receiving entity: in response to receiving a third packet from the PDCP transmitting entity, determining a third count value for the third packet and a third offset value associated with the third count value based on packet header information of the third packet; checking whether the third count value of the third packet is greater than the first count value of the first packet; in response to the third count value being greater than the first count value, checking whether the value obtained by subtracting the third offset value from the third count value is less than or equal to the first count value; In response to the value obtained by subtracting the third offset value from the third count value being equal to or less than the first count value, the third packet is not stored in the receive buffer and the third packet is discarded. It is configured as follows:

2. The PDCP receiving entity of claim 1.

8. The processor of the PDCP transmitting entity is configured to receive, via the transceiver, from a network node, configuration information regarding whether the first discard operation is supported for a radio bearer.

2. The PDCP receiving entity of claim 1.

9. A Packet Data Convergence Protocol (PDCP) transmitting entity, comprising: a processor; a transceiver coupled to the processor; The processor: is configured to detect a packet loss and determine to perform a first discard operation of the PDCP transmitting entity or receive first parameter information related to the first discard operation of the PDCP transmitting entity from a PDCP receiving entity via the transceiver, the packet loss or the first discard operation being associated with a first packet; configured to stop transmitting a second packet associated with the first packet in a transmission buffer in response to detecting the packet loss, in response to determining to perform the first discard operation, or in response to receiving the first parameter information. PDCP transmitting entity.

10. The first packet and the second packet belong to one application data unit (ADU) or one group of pictures (GOP).

10. The PDCP transmission entity of claim 9.

11. The processor of the PDCP transmitting entity is configured to receive, via the transceiver, from a network node, configuration information regarding whether the first discard operation is supported for a radio bearer.

10. The PDCP transmission entity of claim 9.

12. The radio bearer is not configured with an out of order delivery parameter.

12. The PDCP transmission entity of claim 11.

13. While performing the second discarding operation in response to detecting the packet loss or in response to determining to perform the first discarding operation, the processor of the PDCP transmitting entity: determining a second count value for the second packet and a second offset value associated with the second count value based on packet header information of the second packet; checking whether the second count value of the second packet is greater than the first count value of the first packet; in response to the second count value being greater than the first count value, checking whether the second count value minus the second offset value associated with the second count value is less than or equal to the first count value; discarding the second packet in the transmission buffer in response to a value obtained by subtracting the second offset value from the second count value being equal to or less than the first count value; It is configured as follows:

10. The PDCP transmission entity of claim 9.

14. The first parameter information is a first index value of a first application data unit (ADU) to which the first packet belongs; a first index number of the first packet in a group of packets belonging to the first ADU; a first importance level of the first packet; a first count value of the first packet; or a first offset value associated with the first count value of the first packet; Contains at least one of 10. The PDCP transmission entity of claim 9.

15. While performing the second discard operation in response to receiving the first parameter information and in response to the first parameter information including the first count value of the first packet, the processor of the PDCP transmitting entity: determining a second count value for the second packet and a second offset value associated with the second count value based on packet header information of the second packet; checking whether the second count value of the second packet is greater than the first count value of the first packet; in response to the second count value being greater than the first count value, checking whether the second count value minus the second offset value associated with the second count value is less than or equal to the first count value; discarding the second packet in the transmission buffer in response to a value obtained by subtracting the second offset value from the second count value being equal to or less than the first count value; It is configured as follows:

15. The PDCP transmission entity of claim 14.

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