WO2023115477A1

WO2023115477A1 - Methods and apparatuses for supporting a packet discarding operation in rlc layer due to a packet loss

Info

Publication number: WO2023115477A1
Application number: PCT/CN2021/140954
Authority: WO
Inventors: Congchi ZHANG; Mingzeng Dai; Lianhai WU; Jing HAN
Original assignee: Lenovo (Beijing) Limited
Priority date: 2021-12-23
Filing date: 2021-12-23
Publication date: 2023-06-29

Abstract

Embodiments of the present application relate to methods and apparatuses for supporting a packet discarding operation in radio link control (RLC) layer due to a packet loss. According to an embodiment of the present application, an RLC receiving entity includes a processor and a transceiver coupled to the processor; and the processor is configured: to detect a packet loss or to receive, via the transceiver from an RLC transmitting entity, parameter information regarding a discarding operation of the RLC receiving entity, wherein the packet loss or the discarding operation is associated with a packet; and to perform the discarding operation to discard a further packet related to the packet in a receiving buffer, in response to detecting the packet loss or in response to receiving the parameter information.

Description

METHODS AND APPARATUSES FOR SUPPORTING A PACKET DISCARDING OPERATION IN RLC LAYER DUE TO A PACKET LOSS

TECHNICAL FIELD

Embodiments of the present application generally relate to wireless communication technology, in particular to methods and apparatuses for supporting a packet discarding operation in radio link control (RLC) layer due to a packet loss.

BACKGROUND

Extended reality (XR) , including augmented reality (AR) and virtual reality (VR) , as well as cloud gaming (CG) , presents a new promising category of connected devices, applications, and services. As a potential working area of 3GPP (3rd generation partnership project) Rel-18, application and traffic awareness in radio access network (RAN) is one of key feature to improve user experience of XR services.

XR services require high bit rate with bounded latency. Typically, the applications require a certain minimum granularity of application data to be available on the client side before the next level of processing can start. This minimum granularity of application data is referred to an application data unit (ADU) . The high bit rates may lead to that a large ADU will be transmitted in several IP packets. When these IP packets arrive to RAN, RAN will treat all the packets as if they are uncorrelated from each other. In some embodiments, the ADU represents a group of pictures (GOP) for video service. Groups of pictures (GOPs) are grouped together in ways that enhance the visual result of a video sequence. GOPs may include various types of pictures, such as, intra-coded pictures (I-frame) , predictive coded pictures (P-frame) , or B-predictive coded pictures (B-frame) . Encoders use groups of pictures and other tools to render smoothly streaming video. Frame rates and other metrics may also apply.

Depending on the encoding mechanisms, frames in the same ADU or GOP may be correlated to each other. For instance, if the I-frame is lost, the user will not be able to decode the subsequent P-frames and B-frames. In the meanwhile, due to the nature of wireless communication, a packet loss may happen in the UL or DL transmission. To simplify the data processing at the transmitting or receiving side, upon the data loss of an important packet (e.g., I-frame in one ADU or GOP) , there may be no need for RLC entity to continue processing the other correlated packets (e.g., P-frame, B-frame in the same ADU or GOP) , including both RLC transmission and RLC reception.

Given the above, it is desirable to provide a mechanism for supporting a packet discarding operation in RLC layer due to a packet loss.

SUMMARY

Some embodiments of the present application also provide a radio link control (RLC) receiving entity. The RLC receiving entity includes a processor and a transceiver coupled to the processor; and the processor is configured: to detect a packet loss or to receive, via the transceiver from an RLC transmitting entity, parameter information regarding a discarding operation of the RLC receiving entity, wherein the packet loss or the discarding operation is associated with a packet; and to perform the discarding operation to discard a further packet related to the packet in a receiving buffer, in response to detecting the packet loss or in response to receiving the parameter information.

Some embodiments of the present application provide a method, which may be performed by an RLC receiving entity. The method includes: detecting a packet loss or receiving, from an RLC transmitting entity, parameter information regarding a discarding operation of the RLC receiving entity, wherein the packet loss or the discarding operation is associated with a packet; and determining to perform the discarding operation to discard a further packet related to the packet in a receiving buffer, in response to detecting the packet loss or in response to receiving the parameter information.

Some embodiments of the present application also provide an apparatus for wireless communications. The apparatus includes: a non-transitory computer-readable medium having stored thereon computer-executable instructions; a receiving circuitry; a transmitting circuitry; and a processor coupled to the non-transitory computer-readable medium, the receiving circuitry and the transmitting circuitry, wherein the computer-executable instructions cause the processor to implement any of the above-mentioned method performed by an RLC receiving entity.

Some embodiments of the present application also provide an RLC transmitting entity. The RLC transmitting entity includes a processor and a transceiver coupled to the processor; and the processor is configured: to detect a packet loss or to receive, via the transceiver from an RLC receiving entity, parameter information regarding a discarding operation of the RLC transmitting entity, wherein the packet loss or the discarding operation is associated with a packet; and to stop transmitting a further packet related to the packet in a transmitting buffer and to perform the discarding operation to discard the further packet, in response to detecting the packet loss or in response to receiving the parameter information.

Some embodiments of the present application provide a method, which may be performed by an RLC transmitting entity. The method includes: detecting a packet loss or receiving, from an RLC receiving entity, parameter information regarding a discarding operation of the RLC transmitting entity, wherein the packet loss or the discarding operation is associated with a packet; and stopping transmitting a further packet related to the packet in a transmitting buffer and performing the discarding operation to discard the further packet, in response to detecting the packet loss or in response to receiving the parameter information.

Some embodiments of the present application provide an apparatus. The apparatus includes: a non-transitory computer-readable medium having stored thereon computer-executable instructions, a receiving circuitry; a transmitting circuitry; and a processor coupled to the non-transitory computer-readable medium, the receiving circuitry and the transmitting circuitry, wherein the computer-executable instructions cause the processor to implement the abovementioned method performed by an RLC transmitting entity.

The details of one or more examples are set forth in the accompanying drawings and the descriptions below. Other features, objects, and advantages will be apparent from the descriptions and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which advantages and features of the application can be obtained, a description of the application is rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. These drawings depict only example embodiments of the application and are not therefore to be considered limiting of its scope.

FIG. 1 illustrates a schematic diagram of a wireless communication system according to some embodiments of the present application.

FIG. 2 illustrates an exemplary block diagram of an apparatus according to some embodiments of the present application.

FIG. 3 illustrates an exemplary flow chart for a packet discarding operation according to some embodiments of the present application.

FIG. 4 illustrates a further exemplary flow chart for a packet discarding operation according to some embodiments of the present application.

FIG. 5 illustrates an exemplary flow chart of a packet discarding operation in an RLC UM or AM receiving entity according to some embodiments of the present application.

FIG. 6 illustrates an exemplary flow chart of a packet discarding operation in an RLC AM transmitting entity according to some embodiments of the present application.

DETAILED DESCRIPTION

The detailed description of the appended drawings is intended as a description of preferred embodiments 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.

Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architecture and new service scenarios, such as 3rd Generation Partnership Project (3GPP) LTE and LTE advanced, 3GPP 5G NR, 5G-Advanced, 6G, and so on. It is contemplated that along with developments of network architectures and new service scenarios, all embodiments in the present application are also applicable to similar technical problems; and moreover, the terminologies recited in the present application may change, which should not affect the principle of the present application.

FIG. 1 illustrates a schematic diagram of a wireless communication system according to 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. In particular, the wireless communication system 100 includes one BS 101 and two UE 102 (e.g., UE 102a and UE 102b) for illustrative purpose. Although a specific number of BSs and UEs are illustrated in FIG. 1 for simplicity, it is contemplated that the wireless communication system 100 may include more or less BSs and UEs in some other embodiments of the present application.

The wireless communication system 100 is compatible with any type of network that is capable of sending and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with a wireless communication network, a cellular telephone 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 communications network, a high altitude platform network, and/or other communications networks.

BS 101 may communicate with a core network (CN) node (not shown) , e.g., a mobility management entity (MME) or a serving gateway (S-GW) , a mobility management function (AMF) or a user plane function (UPF) etc. via an interface. A BS also be referred to as an access point, an access terminal, a base, a macro cell, a node-B, an enhanced node B (eNB) , a gNB, a home node-B, a relay node, or a device, or described using other terminology used in the art. In 5G NR, a BS may also refer to as a RAN node or network apparatus. Each BS may serve a number of UE (s) within a serving area, for example, a cell or a cell sector via a wireless communication link. Neighbor BSs may communicate with each other as necessary, e.g., during a handover procedure for a UE.

UE 102, e.g., UE 102a and UE 102b, should be understood as any type 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 on-board computers, network devices (e.g., routers, switches, and modems) , or the like. According to an embodiment of the present application, UE 102 may include a portable wireless communication device, a smart phone, a cellular telephone, a flip phone, a device having a subscriber identity module, a personal computer, a selective call receiver, or any other device that is capable of sending and receiving communication signals on a wireless network. In some embodiments, UE 102 may include wearable devices, such as smart watches, fitness bands, optical head-mounted displays, or the like. Moreover, UE 102 may be referred to as a subscriber unit, a mobile, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, or a device, or described using other terminology used in the art. UE 102 may communicate directly with BSs 101 via uplink (UL) communication signals.

As defined in 3GPP TS38.322, regarding RLC transmission and reception operations, data transfer procedures include an unacknowledged mode (UM) data transfer procedure and an acknowledged mode (AM) data transfer procedure.

In particular, in an UM data transfer procedure, during transmission operations, when submitting an unacknowledged mode data (UMD) packet data unit (PDU) to lower layer, a transmitting side of an UM RLC entity shall: set the SN of the UMD PDU to TX_Next, if the UMD PDU contains a segment of an RLC service data unit (SDU) ; and increment TX_Next by one, if the UMD PDU contains a segment that maps to the last byte of an RLC SDU.

A transmitting side of an UM RLC entity may also be named as “an RLC UM Tx entity” , “an UM RLC Tx entity” , “an RLC UM transmitting entity” , “an UM RLC transmitting entity” , “a transmitting RLC UM entity” , “a transmitting UM RLC entity” , or the like.

In an UM data transfer procedure, during reception operations, a receiving side of an UM RLC entity shall maintain a reassembly window according to state variable RX_Next_Highest. When receiving an UMD PDU from a lower layer, the receiving side of an UM RLC entity shall: either deliver the UMD PDU to upper layer after removing the RLC header, discard the received UMD PDU, or place it in the reception buffer; and update state variables, reassemble and deliver RLC SDUs to upper layer and start or stop timer t-Reassembly as needed, if the received UMD PDU was placed in the reception buffer. When timer t-Reassembly expires, the receiving side of an UM RLC entity shall: update state variables, discard RLC SDU segments and start timer t-Reassembly as needed.

A receiving side of an UM RLC entity may also be named as “an RLC UM Rx entity” , “an UM RLC Rx entity” , “an RLC UM receiving entity” , “an UM RLC receiving entity” , “a receiving RLC UM entity” , “a receiving UM RLC entity” , or the like.

In an AM data transfer procedure, during transmission operations, a transmitting side of an AM RLC entity shall prioritize transmission of RLC control PDUs over acknowledged mode data (AMD) PDUs. The transmitting side of an AM RLC entity shall prioritize transmission of AMD PDUs containing previously transmitted RLC SDUs or RLC SDU segments over transmission of AMD PDUs containing not previously transmitted RLC SDUs or RLC SDU segments. The transmitting side of an AM RLC entity shall maintain a transmitting window according to the state variable TX_Next_Ack. The transmitting side of an AM RLC entity shall not submit to lower layer any AMD PDU whose SN falls outside of the transmitting window. For each RLC SDU received from the upper layer, the AM RLC entity shall: associate a SN with the RLC SDU equal to TX_Next and construct an AMD PDU by setting the SN of the AMD PDU to TX_Next; and increment TX_Next by one. When submitting an AMD PDU that contains a segment of an RLC SDU, to a lower layer, the transmitting side of an AM RLC entity shall: set the SN of the AMD PDU to the SN of the corresponding RLC SDU. The transmitting side of an AM RLC entity can receive a positive acknowledgement (confirmation of successful reception by its peer AM RLC entity) for an RLC SDU by the following: STATUS PDU from its peer AM RLC entity. When receiving a positive acknowledgement for an RLC SDU with “SN = x” , the transmitting side of an AM RLC entity shall: send an indication to the upper layers of successful delivery of the RLC SDU; and set TX_Next_Ack equal to the SN of the RLC SDU with the smallest SN, whose SN falls within the range “TX_Next_Ack <= SN <= TX_Next” and for which a positive acknowledgment has not been received yet.

A transmitting side of an AM RLC entity may also be named as “an RLC AM Tx entity” , “an AM RLC Tx entity” , “an RLC AM transmitting entity” , “an AM RLC transmitting entity” , “a transmitting RLC AM entity” , “a transmitting AM RLC entity” , or the like.

In an AM data transfer procedure, during reception operations, a receiving side of an AM RLC entity shall maintain a receiving window according to the state variable RX_Next. When receiving an AMD PDU from a lower layer, the receiving side of an AM RLC entity shall: either discard the received AMD PDU or place it in the reception buffer; and update state variables, reassemble and deliver RLC SDUs to upper layer and start or stop timer t-Reassembly as needed, if the received AMD PDU was placed in the reception buffer. When timer t-Reassembly expires, the receiving side of an AM RLC entity shall update state variables and start timer t-Reassembly as needed.

A receiving side of an AM RLC entity may also be named as “an RLC AM Rx entity” , “an AM RLC Rx entity” , “an RLC AM receiving entity” , “an AM RLC receiving entity” , “a receiving RLC AM entity” , “a receiving AM RLC entity” , or the like.

Currently, there is no mechanism for supporting a packet discarding operation in RLC layer due to a packet loss. Embodiments of the present application aim to solve the above-mentioned issue. Specifically, in some embodiments of the present application, an RLC AM receiving entity or an RLC UM receiving entity may detect a packet loss and decide to discard some other packets which have already been received in the receiving buffer of the RLC AM receiving entity or the RLC UM receiving entity. In some further embodiments of the present application, an RLC AM transmitting entity or an RLC UM transmitting entity may be informed by a peer RLC AM or UM receiving entity about the packet discarding decision and stop the relevant packet transmission. In some other embodiments of the present application, the RLC AM transmitting entity may detect a packet loss according to the received RLC status report and decide to stop transmitting and discard some packets without causing an RLC failure.

In some cases, a GOP may be deemed as one kind of an ADU, and packets belonging to the same ADU are correlated to each other. In the embodiments of the present application, parameters related to an ADU (e.g., an index value of an ADU, “ADUIndexToDiscard” , and etc. ) may be replaced by or applicable for parameters related to a GOP, without departing from the spirit and scope of the disclosure. For example, in some embodiments, an index value of an ADU may be changed or modified to an index value of a GOP. 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. The embodiments with any of such kind of parameter modifications may also solve the above-mentioned issue.

More details will be illustrated in the following text in combination with the appended drawings. Persons skilled in the art should well know that the wording "a/the first, " "a/the second" and "a/the third" etc. are only used for clear description, and should not be deemed as any substantial limitation, e.g., sequence limitation.

FIG. 2 illustrates 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 an RLC receiving entity or an RLC transmitting entity.

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

In some embodiments of the present application, the apparatus 200 may be an RLC receiving entity (e.g., RLC UM/AM Rx entity 510 or RLC AM Rx entity 610 as shown and illustrated in FIG. 5 or FIG. 6) . The processor 204 of the RLC receiving entity may be configured: to detect a packet loss or to receive, via the transceiver 202 from an RLC transmitting entity (e.g., RLC UM/AM Tx entity 520 or RLC AM Tx entity 620 as shown and illustrated in FIG. 5 or FIG. 6) , parameter information regarding a discarding operation of the RLC receiving entity, wherein the packet loss or the discarding operation is associated with a packet; and to perform the discarding operation to discard a further packet related to the packet in a receiving buffer, in response to detecting the packet loss or in response to receiving the parameter information.

For example, in an AM or UM data transfer procedure, the processor 204 of the RLC receiving entity may be configured to detect the packet loss. In an AM data transfer procedure, the processor 204 of the RLC receiving entity may be configured to receive the parameter information regarding the discarding operation of the RLC receiving entity. Specific examples are described in embodiments of FIGS. 5 and 6 as follows.

In following text, the packet may be named as “the 1st packet” , and the further packet is named as “the 2nd packet” , for simplicity. According to some embodiments, the 1st packet or the 2nd packet may be at least one of:

(1) an RLC unacknowledged mode data (UMD) packet data unit (PDU) ;

(2) an RLC acknowledged mode data (AMD) PDU;

(3) an RLC UMD service data unit (SDU) ;

(4) an RLC AMD SDU;

(5) an RLC UMD segment; or

(6) an RLC AMD segment.

In some embodiments, the 1st packet and the 2nd packet belong to one application data unit (ADU) . For example, the 1st packet and the 2nd packet have the same ADU index value. In some other embodiments, the 1st packet and the 2nd packet belong to one group of picture (GOP) . For example, the 1st packet and the 2nd packet have the same GOP index value.

According to some embodiments, the parameter information may be carried via at least one of: physical uplink control channel (PUCCH) signalling, a medium access control (MAC) control element (CE) , or an RLC control PDU. The parameter information received by the RLC receiving entity may include at least one of:

(1) An index value (which is marked as “the 1st index value” for simplicity) of an ADU (which is marked as “the 1st ADU” for simplicity) to which the 1st packet belongs. For example, the 1st index value may be “ADUIndexToDiscard” in embodiments in FIGS. 5 and 6.

(2) An index number (which is marked as “the 1st index number” for simplicity) of the 1st packet in a group of packets belonging to the 1st ADU. For example, the 1st index number may be “NumberInUnitToDiscard” in embodiments in FIGS. 5 and 6.

(3) An importance level (which is marked as “the 1st importance level” for simplicity) of the 1st packet. For example, the 1st importance level may be “ImportanceToDiscard” in embodiments in FIGS. 5 and 6. For instance, the 1st importance level is configured by a network node.

(4) A sequence number (SN) value (which is marked as “the 1st SN value” for simplicity) of the 1st packet. For example, the 1st SN value may be “SNToDiscard” in embodiments in FIGS. 5 and 6.

(5) An offset value (which is marked as “the 1st offset value” for simplicity) related to the 1st SN value of the 1st packet. For example, the 1st offset value may be “Offset” in embodiments in FIGS. 5 and 6.

In some embodiments, in response to receiving the parameter information from the RLC transmitting entity and in response to the parameter information including the 1st index value (e.g., ADUIndexToDiscard) of the 1st ADU to which the 1st packet belongs, during performing the discarding operation of the RLC receiving entity, the processor 204 of the RLC receiving entity may be configured to check whether “an index value (which is marked as “the 2nd index value” for simplicity) of an ADU (which is marked as “the 2nd ADU” for simplicity) to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU” (e.g., ADUIndexToDiscard) . In response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU, the processor 204 of the RLC receiving entity may be configured to discard the 2nd packet in the receiving buffer.

In some further embodiments, in response to receiving the parameter information from the RLC transmitting entity and in response to the parameter information including the 1st index value of the 1st ADU (e.g., ADUIndexToDiscard) and the 1st index number of the 1st packet (e.g., NumberInUnitToDiscard) , during performing the discarding operation of the RLC receiving entity, the processor 204 of the RLC receiving entity may be configured:

(1) to check whether “the 2nd index value of the 2nd ADU to which the 2nd packet belongs” is equal to the 1st index value of the 1st ADU;

(2) to check whether “an index number (which is marked as “the 2nd index number” for simplicity) of the 2nd packet in the group of packets belonging to the 1st ADU” is greater than “the 1st index number of the 1st packet” , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

(3) to discard the 2nd packet in the receiving buffer, in response to the 2nd index number of the 2nd packet being greater than the 1st index number of the 1st packet.

In some other embodiments, in response to receiving the parameter information from the RLC transmitting entity and in response to the parameter information including the 1st index value of the 1st ADU (e.g., ADUIndexToDiscard) and the 1st importance level of the 1st packet (e.g., ImportanceToDiscard) , during performing the discarding operation of the RLC receiving entity, the processor 204 of the RLC receiving entity may be configured:

(1) to check whether “the 2nd index value of the 2nd ADU to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU” (e.g., ADUIndexToDiscard) ;

(2) to check whether “an importance level (which is marked as “the 2nd importance level” for simplicity) of the 2nd packet” is less than “the 1st importance level of the 1st packet” (e.g., ImportanceToDiscard) , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

(3) to discard the 2nd packet in the receiving buffer, in response to the 2nd importance level of the 2nd packet being less than the 1st importance level of the 1st packet.

In some additional embodiments, in response to receiving the parameter information from the RLC transmitting entity and in response to the parameter information including the 1st SN value of the 1st packet (e.g., SNToDiscard) and the 1st offset value related to the 1st SN value (e.g., Offset) , during performing the discarding operation of the RLC receiving entity, the processor 204 of the RLC receiving entity may be configured:

(1) to check whether a SN value (which is marked as “the 2nd SN value” for simplicity) of the 2nd packet is greater than the 1st SN value of the 1st packet (e.g., SN > SNToDiscard) ;

(2) to check whether “the 2nd SN value of the 2nd packet minus the 1st offset value related to the 1st SN value” is less than or equal to “the 1st SN value of the 1st packet” (e.g., ‘SN –Offset’ <= SNToDiscard) , in response to the 2nd SN value of the 2nd packet being greater than the 1st SN value of the 1st packet; and

(3) to discard the 2nd packet in the receiving buffer, in response to “the 2nd SN value of the 2nd packet minus the 1st offset value” being less than or equal to “the 1st SN value of the 1st packet” .

In yet some additional embodiments, in response to receiving the parameter information from the RLC transmitting entity and in response to the parameter information including the 1st SN value of the 1st packet (e.g., SNToDiscard) , during performing the discarding operation of the RLC receiving entity, the processor 204 of the RLC receiving entity may be configured:

(1) to determine “the 2nd SN value of the 2nd packet” and “an offset value (which is marked as “the 2nd offset value” for simplicity) related to the 2nd SN value” based on packet header information of the 2nd packet;

(2) to check whether “the 2nd SN value of the 2nd packet” is greater than “the 1st SN value of the 1st packet” (e.g., SN > SNToDiscard) ;

(3) to check whether “the 2nd SN value of the 2nd packet minus the 2nd offset value related to the 2nd SN value” is less than or equal to “the 1st SN value of the 1st packet” (e.g., ‘SN –Offset’ <= SNToDiscard) , in response to the 2nd SN value of the 2nd packet being greater than the 1st SN value of the 1st packet; and

(4) to discard the 2nd packet in the receiving buffer, in response to “the 2nd SN value of the 2nd packet minus the 2nd offset value” being less than or equal to “the 1st SN value of the 1st packet” .

According to some embodiments, in response to detecting the packet loss associated with the 1st packet, during performing the discarding operation of the RLC receiving entity, the processor 204 of the RLC receiving entity may be configured:

(1) to check whether “the 2nd index value of the 2nd ADU to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” ; and

(2) to discard the 2nd packet in the receiving buffer, in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU.

According to some further embodiments, in response to detecting the packet loss associated with the 1st packet, during performing the discarding operation of the RLC receiving entity, the processor 204 of the RLC receiving entity may be configured:

(1) to check whether “the 2nd index value of the 2nd ADU to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” ;

(2) to check whether “the 2nd index number of the 2nd packet in the group of packets belonging to the 1st ADU” is greater than “the 1st index number of the 1st packet in a group of packets belonging to the 1st ADU” , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

According to some other embodiments, in response to detecting the packet loss associated with the 1st packet, during performing the discarding operation of the RLC receiving entity, the processor 204 of the RLC receiving entity may be configured:

(2) to check whether “the 2nd importance level of the 2nd packet” is less than “the 1st importance level of the 1st packet” , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

(3) to discard the 2nd packet in the receiving buffer, in response to the 2nd importance level being less than the 1st importance level.

According to some additional embodiments, in response to detecting the packet loss associated with the 1st packet, during performing the discarding operation of the RLC receiving entity, the processor 204 of the RLC receiving entity may be configured:

(1) to determine “the 2nd SN value of the 2nd packet” and “the 2nd offset value related to the 2nd SN value” based on packet header information of the 2nd packet;

(3) to check whether “the 2nd SN value minus the 2nd offset value” is less than or equal to “the 1st SN value” (e.g., ‘SN –Offset’ <= SNToDiscard) , in response to the 2nd SN value being greater than the 1st SN value; and

(4) to discard the 2nd packet in the receiving buffer, in response to “the 2nd SN value minus the 2nd offset value” being less than or equal to the 1st SN value.

According to some embodiments, the processor 204 of the RLC receiving entity may be configured: to generate further parameter information regarding a discarding operation of the RLC transmitting entity; and to transmit the further parameter information via the transceiver 202 to the RLC transmitting entity. The further discarding operation is associated with the 1st packet. The further parameter information may be carried via at least one of PUCCH signalling, a MAC CE, or an RLC control PDU. The further parameter information may include at least one of:

(1) a largest one between “the 1st index value of the 1st ADU” and “the 2nd index value of the 2nd ADU” ;

(2) a largest one between “the 1st index number of the 1st packet” and “the 2nd index number of the 2nd packet” ;

(3) a largest one between “the 1st importance level of the 1st packet” and “the 2nd importance level of the 2nd packet” ;

(4) a largest one between “the 1st SN value of the 1st packet” and “the 2nd SN value of the 2nd packet” ; or

(5) the 2nd offset value related to the 2nd SN value of the 2nd packet.

According to some embodiments, in response to discarding the 2nd packet in the receiving buffer, the processor 204 of the RLC receiving entity may be configured to perform at least one of:

(1) setting an unacknowledged mode (UM) receiving state variable (e.g., RX_Next_Reassembly in embodiments in FIGS. 5 and 6) to a SN value of a packet that has not been reassembled and has not been discarded at the RLC receiving entity;

(2) updating a receiving state variable (e.g., RX_Next in embodiments in FIGS. 5 and 6) to a SN value of a non-discarded packet in the receiving buffer, in response to the SN value of the non-discarded packet being greater than a current receiving state variable; or

(3) setting a receiving state variable status trigger value (e.g., RX_Next_Status_Trigger in embodiments in FIGS. 5 and 6) to a sum of the updated receiving state variable and one (e.g., RX_Next_Status_Trigger + 1) .

According to some embodiments, the processor 204 of the RLC receiving entity may be configured to receive, via the transceiver 202 from a network node, configuration information regarding whether the discarding operation of the RLC receiving entity is supported for a radio bearer.

According to some embodiments, the processor 204 of the RLC receiving entity may be configured to receive, via the transceiver 202 from a network node, configuration information regarding a reception failure number threshold for the RLC receiving entity (e.g., NumberOfReceptionFailure in embodiments in FIGS. 5 and 6) . The discarding operation of the RLC receiving entity may be performed upon meeting the reception failure number threshold for the RLC receiving entity.

According to some embodiments, the processor 204 of the RLC receiving entity may be configured:

(1) to check whether “an index value (which is marked as “the 3rd index value” for simplicity) of another ADU (which is marked as “the 3rd ADU” for simplicity) to which another packet (which is marked as “the 3rd packet” for simplicity) belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” (e.g., ADUIndexToDiscard) , in response to receiving the 3rd packet from the RLC transmitting entity; and

(2) not to store the 3rd packet into the receiving buffer and to discard the 3rd packet, in response to the 3rd index value of the 3rd ADU being equal to the 1st index value of the 1st ADU.

According to some other embodiments, the processor 204 of the RLC receiving entity may be configured:

(1) to check whether “the 3rd index value of the 3rd ADU to which the 3rd packet belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” , in response to receiving the 3rd packet from the RLC transmitting entity;

(2) to check whether “an index number (which is marked as “the 3rd index number” for simplicity) of the 3rd packet in a group of packets belonging to the 3rd ADU” is greater than “the 1st index number of the 1st packet in a group of packets belonging to the 1st ADU” , in response to the 3rd index value of the 3rd ADU being equal to the 1st index value of the 1st ADU; and

(3) not to store the 3rd packet into the receiving buffer and to discard the 3rd packet, in response to the 3rd index number of the 3rd packet being greater than the 1st index number of the 1st packet.

According to some further embodiments, the processor 204 of the RLC receiving entity may be configured to:

(1) to check whether “the 3rd index value of the 3rd ADU to which the 3rd packet belongs” is equal to “the 1st index value of a first ADU to which the 1st packet belongs” , in response to receiving the 3rd packet from the RLC transmitting entity;

(2) to check whether “an importance level (which is marked as “the 3rd importance level” for simplicity) of the 3rd packet” is less than “the 1st importance level of the 1st packet” , in response to the 3rd index value of the 3rd ADU being equal to the 1st index value of the 1st ADU; and

(3) not to store the 3rd packet into the receiving buffer and to discard the 3rd packet, in response to the 3rd importance level being less than the 1st importance level.

According to some additional embodiments, the processor 204 of the RLC receiving entity may be configured to:

(1) to determine a SN value (which is marked as “the 3rd SN value” for simplicity) of the 3rd packet and a offset value (which is marked as “the 3rd offset value” for simplicity) related to the 3rd SN value based on packet header information of the 3rd packet, in response to receiving the 3rd packet from the RLC transmitting entity;

(2) to check whether “the 3rd SN value of the 3rd packet” is greater than “the 1st SN value of the 1st packet” ;

(3) to check whether “the 3rd SN value minus the 3rd offset value” is less than or equal to the 1st SN value of the 1st packet, in response to the 3rd SN value being greater than the 1st SN value; and

(4) not to store the 3rd packet into the receiving buffer and to discard the 3rd packet, in response to “the 3rd SN value minus the 3rd offset value” being less than or equal to the 1st SN value.

According to yet some additional embodiments, the processor 204 of the RLC receiving entity may be configured:

(1) to determine “the 3rd SN value of the 3rd packet” based on packet header information of the 3rd packet, in response to receiving the 3rd packet from the RLC transmitting entity;

(3) to check whether “the 3rd SN value minus the 1st offset value related to the 1st SN value of the 1st packet” is less than or equal to “the 1st SN value of the 1st packet” , in response to the 3rd SN value being greater than the 1st SN value and in response to the 1st parameter information including the 1st offset value related to the 1st SN value of the 1st packet; and

(4) not to store the 3rd packet into the receiving buffer and to discard the 3rd packet, in response to “the 3rd SN value minus the 1st offset value” being less than or equal to the first SN value.

In some embodiments of the present application, the apparatus 200 may be an RLC transmitting entity (e.g., RLC UM/AM Tx entity 520 or RLC AM Tx entity 620 as shown and illustrated in FIG. 5 or FIG. 6) . The processor 204 of the RLC transmitting entity may be configured: to detect a packet loss or to receive, via the transceiver 202 from an RLC receiving entity (e.g., RLC UM/AM Rx entity 510 or RLC AM Rx entity 610 as shown and illustrated in FIG. 5 or FIG. 6) , parameter information regarding a discarding operation of the RLC transmitting entity, wherein the packet loss or the discarding operation is associated with a packet; and to stop transmitting a further packet related to the packet in a transmitting buffer and to perform the discarding operation to discard the further packet, in response to detecting the packet loss or in response to receiving the parameter information. The parameter information may be carried via at least one of PUCCH signalling, a MAC CE, or an RLC control PDU.

For example, in an AM data transfer procedure, the processor 204 of the RLC transmitting entity may be configured to detect the packet loss. In an AM or UM data transfer procedure, the processor 204 of the RLC transmitting entity may be configured to receive the parameter information regarding the discarding operation of the RLC transmitting entity. Specific examples are described in embodiments of FIGS. 5 and 6 as follows.

In following text, the packet may be named as “the 1st packet” , and the further packet is named as “the 2nd packet” , for simplicity. According to some embodiments, each of the 1st packet and the 2nd packet is at least one of: (1) an RLC UMD PDU; (2) an RLC AMD PDU; (3) an RLC UMD SDU; (4) an RLC AMD SDU; (5) an RLC UMD segment; or (6) an RLC AMD segment. In some embodiments, the 1st packet and the 2nd packet belong to one ADU or one GOP. For example, the 1st packet and the 2nd packet have the same ADU index value or the same GOP index value.

According to some embodiments, the processor 204 of the RLC transmitting entity may be configured to receive, via the transceiver 202 from the network node, at least one of:

(1) configuration information regarding whether the discarding operation of the RLC transmitting entity is supported for a radio bearer; or

(2) configuration information regarding an RLC retransmission failure number for triggering the discarding operation of the RLC transmitting entity, wherein the RLC retransmission failure number is different from a maximum RLC retransmission number of the RLC transmitting entity.

In some embodiments, the discarding operation of the RLC transmitting entity is performed after the RLC transmitting entity performing a certain number of an RLC retransmission attempt operation for the 1st packet. In an embodiment, the discarding operation of the RLC transmitting entity is performed in response to the certain number of an RLC retransmission attempt operation for the 1st packet exceeding a maximum RLC retransmission number of the RLC transmitting entity.

According to some embodiments, in response to detecting the packet loss associated with the 1st packet, during performing the discarding operation of the RLC transmitting entity, the processor 204 of the RLC transmitting entity may be configured:

(1) to check whether “an index value (which is marked as “the 2nd index value” for simplicity) of an ADU (which is marked as “the 2nd ADU” for simplicity) to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” (e.g., ADUIndexToDiscard) ; and

(2) to discard the 2nd packet in the transmitting buffer, in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU.

(1) to check whether “the 2nd index value of the 2nd ADU to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” (e.g., ADUIndexToDiscard) ;

(2) to check whether “an index number (which is marked as “the 2nd index number” for simplicity) of the 2nd packet in the group of packets belonging to the 1st ADU” is greater than “the 1st index number of the 1st packet in a group of packets belonging to the 1st ADU” (e.g., NumberInUnitToDiscard) , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

(3) to discard the 2nd packet in the transmitting buffer, in response to the 2nd index number of the 2nd packet being greater than the 1st index number of the 1st packet.

(3) to discard the 2nd packet in the transmitting buffer, in response to the 2nd importance level being less than the 1st importance level.

(1) to determine a SN value (which is marked as “the 2nd SN value” for simplicity) of the 2nd packet and an offset value (which is marked as “the 2nd offset value” for simplicity) related to the 2nd SN value based on packet header information of the 2nd packet;

(3) to check whether “the 2nd SN value minus the 2nd offset value related to the 2nd SN value” is less than or equal to “the 1st SN value of the 1st packet” (e.g., ‘SN –Offset’ <= SNToDiscard) , in response to the 2nd SN value being greater than the 1st SN value; and

(4) to discard the 2nd packet in the transmitting buffer, in response to “the 2nd SN value minus the 2nd offset value” being less than or equal to the 1st SN value.

According to some embodiments, the processor 204 of the RLC transmitting entity may be configured to transmit, via the transceiver 202 to an RLC receiving entity, further parameter information regarding a discarding operation of the RLC receiving entity. The discarding operation of the RLC receiving entity is associated with the 1st packet. The further parameter information may be carried via at least one of PUCCH signalling, a MAC CE, or an RLC control PDU. The further parameter information may include at least one of:

(1) the 2nd index value of the 2nd ADU to which the 2nd packet belongs;

(2) the 2nd index number of the 2nd packet;

(3) the 2nd importance level of the 2nd packet;

(4) the 2nd SN value of the 2nd packet; or

(5) the 2nd offset value related to the 2nd SN value.

According to some embodiments, in response to discarding the 2nd packet in the transmitting buffer, the processor 204 of the RLC transmitting entity may be configured to set an acknowledgement state variable (e.g., TX_Next_Ack in embodiments in FIG. 6) to a SN value of a non-discarded packet with a smallest SN value in the transmitting buffer, in response to the SN value of the not discarded packet being equal to or greater than the acknowledgement state variable (e.g., TX_Next_Ack <= SN <= TX_Next in embodiments in FIG. 6) and in response to the SN value of the not discarded packet being equal to or greater than a transmitting state variable (e.g., TX_Next in embodiments in FIG. 6) .

According to some embodiments, the parameter information received by the RLC transmitting entity includes at least one of:

(1) An index value (which is marked as “the 1st index value” for simplicity) of an ADU (which is marked as “the 1st ADU” for simplicity) to which the 1st packet belongs, e.g., “ADUIndexToDiscard” in embodiments in FIGS. 5 and 6.

(2) An index number (which is marked as “the 1st index number” for simplicity) of the 1st packet in a group of packets belonging to the 1st ADU, e.g., “NumberInUnitToDiscard” in embodiments in FIGS. 5 and 6.

(3) An importance level (which is marked as “the 1st importance level” for simplicity) of the 1st packet, e.g., “ImportanceToDiscard” in embodiments in FIGS. 5 and 6. For instance, the importance level is configured by a network node.

(4) A SN value (which is marked as “the 1st SN value” for simplicity) of the 1st packet, e.g., “SNToDiscard” in embodiments in FIGS. 5 and 6.

(5) An offset value (which is marked as “the 1st offset value” for simplicity) related to the 1st SN value of the 1st packet, e.g., “Offset” in embodiments in FIGS. 5 and 6.

In some embodiments, in response to receiving the parameter information from the RLC receiving entity and in response to the parameter information including the 1st index value of the 1st ADU (e.g., ADUIndexToDiscard) , during performing the discarding operation of the RLC transmitting entity, the processor 204 of the RLC transmitting entity is configured:

(1) to check whether “an index value (which is marked as “the 2nd index value” for simplicity) of an ADU (which is marked as “the 2nd ADU” for simplicity) to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU” (e.g., ADUIndexToDiscard) ; and

In some embodiments, in response to receiving the parameter information from the RLC receiving entity and in response to the parameter information including the 1st index value of the 1st ADU (e.g., ADUIndexToDiscard) and the 1st index number of the 1st packet (e.g., NumberInUnitToDiscard) , during performing the discarding operation of the RLC transmitting entity, the processor 204 of the RLC transmitting entity is configured:

(2) to check whether “an index number (which is marked as “the 2nd index number” for simplicity) of the 2nd packet in the group of packets belonging to the 1st ADU” is greater than “the 1st index number of the 1st packet” (e.g., NumberInUnitToDiscard) , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

In some embodiments, in response to receiving the parameter information from the RLC receiving entity and in response to the parameter information including the 1st index value of the 1st ADU (e.g., ADUIndexToDiscard) and the 1st importance level of the 1st packet (e.g., ImportanceToDiscard) , during performing the discarding operation of the RLC transmitting entity, the processor 204 of the RLC transmitting entity is configured:

In some embodiments, in response to receiving the parameter information from the RLC receiving entity and in response to the parameter information including the 1st SN value of the 1st packet (e.g., SNToDiscard) and the 1st offset value related to the 1st SN value (e.g., Offset) , during performing the discarding operation of the RLC transmitting entity, the processor 204 of the RLC transmitting entity is configured:

(1) to check whether “a SN value (which is marked as “the 2nd SN value” for simplicity) of the 2nd packet” is greater than “the 1st SN value of the 1st packet” (e.g., SN > SNToDiscard) ;

(2) to check whether “the 2nd SN value minus the 1st offset value related to the 1st SN value” is less than or equal to the 1st SN value, in response to the 2nd SN value being greater than the 1st SN value (e.g., ‘SN –Offset’ <= SNToDiscard) ; and

(3) to discard the 2nd packet in the transmitting buffer, in response to “the 2nd SN value minus the 1st offset value” being less than or equal to the 1st SN value.

In some embodiments, in response to receiving the parameter information from the RLC receiving entity and in response to the parameter information including the 1st SN value of the 1st packet (e.g., SNToDiscard) , during performing the discarding operation of the RLC transmitting entity, the processor 204 of the RLC transmitting entity is configured:

(1) to determine the 2nd SN value of the 2nd packet and the 2nd offset value related to the 2nd SN value based on packet header information of the 2nd packet;

(2) to check whether “the 2nd SN value of the 2nd packet” is greater than “the 1st SN value of the 1st packet” ;

(3) to check whether “the 2nd SN value minus the 2nd offset value related to the 2nd SN value” is less than or equal to “the 1st SN value of the 1st packet” , in response to the 2nd SN value being greater than the 1st SN value; and

(4) to discard the 2nd packet in the transmitting buffer, in response to “the 2nd SN value minus the 2nd offset value” being less than or equal to “the 1st SN value of the 1st packet” .

In some embodiments of the present application, the apparatus 200 may include at least one non-transitory computer-readable medium. In some embodiments of the present disclosure, the non-transitory computer-readable medium may have stored thereon computer-executable instructions to cause a processor to implement the method with respect to an RLC receiving entity or an RLC transmitting entity as described above. For example, the computer-executable instructions, when executed, cause the processor 204 interacting with the transceiver 202, so as to perform operations of the methods, e.g., as described in view of FIGS. 3-6.

FIG. 3 illustrates an exemplary flow chart for a packet discarding operation according to some embodiments of the present application. The method 300 may be performed by an RLC receiving entity (e.g., RLC UM/AM Rx entity 510 or RLC AM Rx entity 610 as shown and illustrated in FIG. 5 or FIG. 6) . Although described with respect to an RLC receiving entity, it should be understood that other devices may also be configured to perform the method as shown and illustrated in FIG. 3.

In the exemplary method 300 illustrated in FIG. 3, in operation 301, an RLC receiving entity (e.g., RLC UM/AM Rx entity 510 as shown and illustrated in FIG. 5) detects a packet loss (which is marked as “the 1st packet” for simplicity) or receives, from an RLC transmitting entity (e.g., RLC UM/AM Tx entity 520 as shown and illustrated in FIG. 5) , parameter information regarding a discarding operation of the RLC receiving entity. The packet loss or the discarding operation is associated with the 1st packet. In operation 302, the RLC receiving entity determines to perform the discarding operation to discard a further packet (which is marked as “the 2nd packet” for simplicity) related to the 1st packet in a receiving buffer, in response to detecting the packet loss or in response to receiving the parameter information from the RLC transmitting entity.

For example, in an AM or UM data transfer procedure, the RLC receiving entity may detect the packet loss. In an AM data transfer procedure, the RLC receiving entity may receive the parameter information regarding the discarding operation of the RLC receiving entity. Specific examples are described in embodiments of FIGS. 5 and 6 as follows.

According to some embodiments of the method 300 illustrated in FIG. 3, each of the 1st packet and the 2nd packet is at least one of: (1) an RLC UMD PDU; (2) an RLC AMD PDU; (3) an RLC UMD SDU; (4) an RLC AMD SDU; (5) an RLC UMD segment; or (6) an RLC AMD segment. In some embodiments, the 1st packet and the 2nd packet belong to one ADU, e.g., the 1st packet and the 2nd packet have the same ADU index value. In some other embodiments, the 1st packet and the 2nd packet belong to one GOP, e.g., the 1st packet and the 2nd packet have the same GOP index value.

According to some embodiments of the method 300 illustrated in FIG. 3, the parameter information may be carried via at least one of PUCCH signalling, a MAC CE, or an RLC control PDU. The parameter information received by the RLC receiving entity may include at least one of following parameters.

(3) An importance level (which is marked as “the 1st importance level” for simplicity) of the 1st packet, e.g., “ImportanceToDiscard” in embodiments in FIGS. 5 and 6. For instance, the 1st importance level is configured by a network node.

(4) A sequence number (SN) value (which is marked as “the 1st SN value” for simplicity) of the 1st packet, e.g., “SNToDiscard” in embodiments in FIGS. 5 and 6.

In some embodiments of the method 300 illustrated in FIG. 3, in the method 300 illustrated in FIG. 3, in response to receiving the parameter information from the RLC transmitting entity and in response to the parameter information including the 1st index value (e.g., ADUIndexToDiscard) of the 1st ADU to which the 1st packet belongs, during performing the discarding operation, the RLC receiving entity further checks whether “an index value (which is marked as “the 2nd index value” for simplicity) of an ADU (which is marked as “the 2nd ADU” for simplicity) to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU” (e.g., ADUIndexToDiscard) . In response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU, the RLC receiving entity may discard the 2nd packet in the receiving buffer.

In some further embodiments of the method 300 illustrated in FIG. 3, in response to receiving the parameter information from the RLC transmitting entity and in response to the parameter information including the 1st index value of the 1st ADU (e.g., ADUIndexToDiscard) and the 1st index number of the 1st packet (e.g., NumberInUnitToDiscard) , during performing the discarding operation, the RLC receiving entity may:

(1) check whether “the 2nd index value of the 2nd ADU to which the 2nd packet belongs” is equal to the 1st index value of the 1st ADU;

(2) check whether “an index number (which is marked as “the 2nd index number” for simplicity) of the 2nd packet in the group of packets belonging to the 1st ADU” is greater than “the 1st index number of the 1st packet” , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

(3) discard the 2nd packet in the receiving buffer, in response to the 2nd index number of the 2nd packet being greater than the 1st index number of the 1st packet.

In some other embodiments of the method 300 illustrated in FIG. 3, in response to receiving the parameter information from the RLC transmitting entity and in response to the parameter information including the 1st index value of the 1st ADU (e.g., ADUIndexToDiscard) and the 1st importance level of the 1st packet (e.g., ImportanceToDiscard) , during performing the discarding operation of the RLC receiving entity, the RLC receiving entity may:

(1) check whether “the 2nd index value of the 2nd ADU to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU” (e.g., ADUIndexToDiscard) ;

(2) check whether “an importance level (which is marked as “the 2nd importance level” for simplicity) of the 2nd packet” is less than “the 1st importance level of the 1st packet” (e.g., ImportanceToDiscard) , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

(3) discard the 2nd packet in the receiving buffer, in response to the 2nd importance level of the 2nd packet being less than the 1st importance level of the 1st packet.

In some additional embodiments of the method 300 illustrated in FIG. 3, in response to receiving the parameter information from the RLC transmitting entity and in response to the parameter information including the 1st SN value of the 1st packet (e.g., SNToDiscard) and the 1st offset value related to the 1st SN value (e.g., Offset) , during performing the discarding operation of the RLC receiving entity, the RLC receiving entity may:

(1) check whether a SN value (which is marked as “the 2nd SN value” for simplicity) of the 2nd packet is greater than the 1st SN value of the 1st packet (e.g., SN >SNToDiscard) ;

(2) check whether “the 2nd SN value of the 2nd packet minus the 1st offset value related to the 1st SN value” is less than or equal to “the 1st SN value of the 1st packet” (e.g., ‘SN –Offset’ <= SNToDiscard) , in response to the 2nd SN value of the 2nd packet being greater than the 1st SN value of the 1st packet; and

(3) discard the 2nd packet in the receiving buffer, in response to “the 2nd SN value of the 2nd packet minus the 1st offset value” being less than or equal to the 1st SN value of the 1st packet.

In yet some additional embodiments of the method 300 illustrated in FIG. 3, in response to receiving the parameter information from the RLC transmitting entity and in response to the parameter information including the 1st SN value of the 1st packet (e.g., SNToDiscard) , during performing the discarding operation of the RLC receiving entity, the RLC receiving entity may:

(1) determine “the 2nd SN value of the 2nd packet” and “an offset value (which is marked as “the 2nd offset value” for simplicity) related to the 2nd SN value” based on packet header information of the 2nd packet;

(2) check whether “the 2nd SN value of the 2nd packet” is greater than “the 1st SN value of the 1st packet” (e.g., SN > SNToDiscard) ;

(3) check whether “the 2nd SN value of the 2nd packet minus the 2nd offset value related to the 2nd SN value” is less than or equal to “the 1st SN value of the 1st packet” (e.g., ‘SN –Offset’ <= SNToDiscard) , in response to the 2nd SN value of the 2nd packet being greater than the 1st SN value of the 1st packet; and

(4) discard the 2nd packet in the receiving buffer, in response to “the 2nd SN value of the 2nd packet minus the 2nd offset value” being less than or equal to “the 1st SN value of the 1st packet” .

According to some embodiments of the method 300 illustrated in FIG. 3, in response to detecting the packet loss associated with the 1st packet, during performing the discarding operation of the RLC receiving entity, the RLC receiving entity may:

(1) check whether “the 2nd index value of the 2nd ADU to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” ; and

(2) discard the 2nd packet in the receiving buffer, in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU.

According to some further embodiments of the method 300 illustrated in FIG. 3, in response to detecting the packet loss associated with the 1st packet, during performing the discarding operation of the RLC receiving entity, the RLC receiving entity may:

(1) check whether “the 2nd index value of the 2nd ADU to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” ;

(2) check whether “the 2nd index number of the 2nd packet in the group of packets belonging to the 1st ADU” is greater than “the 1st index number of the 1st packet in a group of packets belonging to the 1st ADU” , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

According to some other embodiments of the method 300 illustrated in FIG. 3, in response to detecting the packet loss associated with the 1st packet, during performing the discarding operation of the RLC receiving entity, the RLC receiving entity may:

(2) check whether “the 2nd importance level of the 2nd packet” is less than “the 1st importance level of the 1st packet” , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

(3) discard the 2nd packet in the receiving buffer, in response to the 2nd importance level being less than the 1st importance level.

According to some additional embodiments of the method 300 illustrated in FIG. 3, in response to detecting the packet loss associated with the 1st packet, during performing the discarding operation of the RLC receiving entity, the RLC receiving entity may:

(1) determine “the 2nd SN value of the 2nd packet” and “the 2nd offset value related to the 2nd SN value” based on packet header information of the 2nd packet;

(3) check whether “the 2nd SN value minus the 2nd offset value” is less than or equal to “the 1st SN value” (e.g., ‘SN –Offset’ <= SNToDiscard) , in response to the 2nd SN value being greater than the 1st SN value; and

(4) discard the 2nd packet in the receiving buffer, in response to “the 2nd SN value minus the 2nd offset value” being less than or equal to the 1st SN value.

According to some embodiments of the method 300 illustrated in FIG. 3, the RLC receiving entity may generate further parameter information regarding a discarding operation of the RLC transmitting entity, and transmit the further parameter information to the RLC transmitting entity. The further discarding operation is associated with the 1st packet. The further parameter information may be carried via at least one of PUCCH signalling, a MAC CE, or an RLC control PDU. The further parameter information may include at least one of:

(5) the 2nd offset value related to the 2nd SN value of the 2nd packet.

According to some embodiments of the method 300 illustrated in FIG. 3, in response to discarding the 2nd packet in the receiving buffer, the RLC receiving entity may perform at least one of:

According to yet some additional embodiments of the method 300 illustrated in FIG. 3, the RLC receiving entity may receive, from a network node, configuration information regarding whether the discarding operation of the RLC receiving entity is supported for a radio bearer.

According to some embodiments of the method 300 illustrated in FIG. 3, the RLC receiving entity may receive, from a network node, configuration information regarding a reception failure number threshold for the RLC receiving entity (e.g., NumberOfReceptionFailure in embodiments in FIGS. 5 and 6) . The discarding operation of the RLC receiving entity may be performed upon meeting the reception failure number threshold for the RLC receiving entity.

According to some embodiments of the method 300 illustrated in FIG. 3, the RLC receiving entity may:

(1) check whether “an index value (which is marked as “the 3rd index value” for simplicity) of another ADU (which is marked as “the 3rd ADU” for simplicity) to which another packet (which is marked as “the 3rd packet” for simplicity) belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” (e.g., ADUIndexToDiscard) , in response to receiving the 3rd packet from the RLC transmitting entity; and

(2) “not store the 3rd packet into the receiving buffer” and “discard the 3rd packet” , in response to the 3rd index value of the 3rd ADU being equal to the 1st index value of the 1st ADU.

According to some other embodiments of the method 300 illustrated in FIG. 3, the RLC receiving entity may:

(1) check whether “the 3rd index value of the 3rd ADU to which the 3rd packet belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” , in response to receiving the 3rd packet from the RLC transmitting entity;

(2) check whether “an index number (which is marked as “the 3rd index number” for simplicity) of the 3rd packet in a group of packets belonging to the 3rd ADU” is greater than “the 1st index number of the 1st packet in a group of packets belonging to the 1st ADU” , in response to the 3rd index value of the 3rd ADU being equal to the 1st index value of the 1st ADU; and

(3) “not store the 3rd packet into the receiving buffer” and “discard the 3rd packet” , in response to the 3rd index number of the 3rd packet being greater than the 1st index number of the 1st packet.

According to some further embodiments of the method 300 illustrated in FIG. 3, the RLC receiving entity may:

(1) check whether “the 3rd index value of the 3rd ADU to which the 3rd packet belongs” is equal to “the 1st index value of a first ADU to which the 1st packet belongs” , in response to receiving the 3rd packet from the RLC transmitting entity;

(2) check whether “an importance level (which is marked as “the 3rd importance level” for simplicity) of the 3rd packet” is less than “the 1st importance level of the 1st packet” , in response to the 3rd index value of the 3rd ADU being equal to the 1st index value of the 1st ADU; and

(3) “not store the 3rd packet into the receiving buffer” and “discard the 3rd packet” , in response to the 3rd importance level being less than the 1st importance level.

According to some additional embodiments of the method 300 illustrated in FIG. 3, the RLC receiving entity may:

(1) determine a SN value (which is marked as “the 3rd SN value” for simplicity) of the 3rd packet and a offset value (which is marked as “the 3rd offset value” for simplicity) related to the 3rd SN value based on packet header information of the 3rd packet, in response to receiving the 3rd packet from the RLC transmitting entity;

(2) check whether “the 3rd SN value of the 3rd packet” is greater than “the 1st SN value of the 1st packet” ;

(3) check whether “the 3rd SN value minus the 3rd offset value” is less than or equal to the 1st SN value of the 1st packet, in response to the 3rd SN value being greater than the 1st SN value; and

According to yet some additional embodiments of the method 300 illustrated in FIG. 3, the RLC receiving entity may:

(1) determine “the 3rd SN value of the 3rd packet” based on packet header information of the 3rd packet, in response to receiving the 3rd packet from the RLC transmitting entity;

(3) check whether “the 3rd SN value minus the 1st offset value related to the 1st SN value of the 1st packet” is less than or equal to “the 1st SN value of the 1st packet” , in response to the 3rd SN value being greater than the 1st SN value and in response to the 1st parameter information including the 1st offset value related to the 1st SN value of the 1st packet; and

(4) not to store the 3rd packet into the receiving buffer and to discard the 3rd packet, in response to “the 3rd SN value minus the 1st offset value” being less than or equal to the 1st SN value.

It is contemplated that the method 300 illustrated in FIG. 3 may include other operation (s) not shown, for example, any operation (s) described with respect to FIGS. 2 and 4-6.

Details described in all other embodiments of the present application (for example, details regarding a mechanism for supporting a packet discarding operation in RLC layer due to a packet loss) are applicable for the embodiments of FIG. 3. Moreover, details described in the embodiments of FIG. 3 are applicable for all embodiments of FIGS. 1, 2, and 4-6. It should be appreciated by persons skilled in the art that the sequence of the operations in exemplary procedure in the embodiments of FIG. 3 may be changed and some of the operations in exemplary procedure in the embodiments of FIG. 3 may be eliminated or modified, without departing from the spirit and scope of the disclosure.

FIG. 4 illustrates a further exemplary flow chart for a packet discarding operation according to some embodiments of the present application. The embodiments of FIG. 4 may be performed by an RLC transmitting entity (e.g., RLC UM/AM Tx entity 520 or RLC AM Tx entity 620 as shown and illustrated in FIG. 5 or FIG. 6) . Although described with respect to an RLC transmitting entity, it should be understood that other devices may be configured to perform a method similar to that of FIG. 4.

In the exemplary method 400 as shown in FIG. 4, in operation 401, an RLC transmitting entity (e.g., RLC UM/AM Tx entity 520 as shown and illustrated in FIG. 5) detects a packet loss (which is marked as “the 1st packet” for simplicity) or receives, from an RLC receiving entity (e.g., RLC UM/AM Rx entity 510 as shown and illustrated in FIG. 5) , parameter information regarding a discarding operation of the RLC transmitting entity. The packet loss or the discarding operation is associated with the 1st packet. In operation 402 as shown in FIG. 4, the RLC transmitting entity stops transmitting a further packet (which is marked as “the 2nd packet” for simplicity) related to the 1st packet in a transmitting buffer and performs the discarding operation to discard the further packet, in response to detecting the packet loss or in response to receiving the parameter information.

For example, in an AM data transfer procedure, the RLC transmitting entity may detect the packet loss. In an AM or UM data transfer procedure, the RLC transmitting entity may receive the parameter information regarding the discarding operation of the RLC transmitting entity. Specific examples are described in embodiments of FIGS. 5 and 6 as follows.

According to some embodiments of the method 400 illustrated in FIG. 4, each of the 1st packet and the 2nd packet is at least one of: (1) an RLC UMD PDU; (2) an RLC AMD PDU; (3) an RLC UMD SDU; (4) an RLC AMD SDU; (5) an RLC UMD segment; or (6) an RLC AMD segment. In some embodiments, the 1st packet and the 2nd packet belong to one ADU, e.g., the 1st packet and the 2nd packet have the same ADU index value. In some other embodiments, the 1st packet and the 2nd packet belong to one GOP, e.g., the 1st packet and the 2nd packet have the same GOP index value.

According to some embodiments of the method 400 illustrated in FIG. 4, the parameter information may be carried via at least one of PUCCH signalling, a MAC CE, or an RLC control PDU.

In some embodiments of the method 400 illustrated in FIG. 4, the RLC transmitting entity may receive, from the network node, at least one of:

(2) configuration information regarding an RLC retransmission failure number for triggering the discarding operation of the RLC transmitting entity. The RLC retransmission failure number is different from a maximum RLC retransmission number of the RLC transmitting entity.

In some embodiments of the method 400 illustrated in FIG. 4, the discarding operation of the RLC transmitting entity is performed after the RLC transmitting entity performing a certain number of an RLC retransmission attempt operation for the 1st packet. In an embodiment, the discarding operation of the RLC transmitting entity is performed in response to the certain number of an RLC retransmission attempt operation for the 1st packet exceeding a maximum RLC retransmission number of the RLC transmitting entity.

According to some embodiments of the method 400 illustrated in FIG. 4, in response to detecting the packet loss associated with the 1st packet, during performing the discarding operation of the RLC transmitting entity, the RLC transmitting entity may:

(1) check whether “an index value (which is marked as “the 2nd index value” for simplicity) of an ADU (which is marked as “the 2nd ADU” for simplicity) to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” (e.g., ADUIndexToDiscard) ; and

(2) discard the 2nd packet in the transmitting buffer, in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU.

(1) check whether “the 2nd index value of the 2nd ADU to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU to which the 1st packet belongs” (e.g., ADUIndexToDiscard) ;

(2) check whether “an index number (which is marked as “the 2nd index number” for simplicity) of the 2nd packet in the group of packets belonging to the 1st ADU” is greater than “the 1st index number of the 1st packet in a group of packets belonging to the 1st ADU” (e.g., NumberInUnitToDiscard) , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

(3) discard the 2nd packet in the transmitting buffer, in response to the 2nd index number of the 2nd packet being greater than the 1st index number of the 1st packet.

(3) discard the 2nd packet in the transmitting buffer, in response to the 2nd importance level being less than the 1st importance level.

(1) determine a SN value (which is marked as “the 2nd SN value” for simplicity) of the 2nd packet and an offset value (which is marked as “the 2nd offset value” for simplicity) related to the 2nd SN value based on packet header information of the 2nd packet;

(3) check whether “the 2nd SN value minus the 2nd offset value related to the 2nd SN value” is less than or equal to “the 1st SN value of the 1st packet” (e.g., ‘SN –Offset’ <= SNToDiscard) , in response to the 2nd SN value being greater than the 1st SN value; and

(4) discard the 2nd packet in the transmitting buffer, in response to “the 2nd SN value minus the 2nd offset value” being less than or equal to the 1st SN value.

According to some embodiments of the method 400 illustrated in FIG. 4, the RLC transmitting entity may transmit, to an RLC receiving entity, further parameter information regarding a discarding operation of the RLC receiving entity. The discarding operation of the RLC receiving entity is associated with the 1st packet. The further parameter information may be carried via at least one of PUCCH signalling, a MAC CE, or an RLC control PDU. The further parameter information may include at least one of:

(1) the 2nd index value of the 2nd ADU to which the 2nd packet belongs;

(2) the 2nd index number of the 2nd packet;

(3) the 2nd importance level of the 2nd packet;

(4) the 2nd SN value of the 2nd packet; or

(5) the 2nd offset value related to the 2nd SN value.

According to some embodiments of the method 400 illustrated in FIG. 4, in response to discarding the 2nd packet in the transmitting buffer, the RLC transmitting entity may set an acknowledgement state variable (e.g., TX_Next_Ack in embodiments in FIG. 6) to a SN value of a non-discarded packet with a smallest SN value in the transmitting buffer, in response to the SN value of the not discarded packet being equal to or greater than the acknowledgement state variable (e.g., TX_Next_Ack <=SN <= TX_Next in embodiments in FIG. 6) and in response to the SN value of the not discarded packet being equal to or greater than a transmitting state variable (e.g., TX_Next in embodiments in FIG. 6) .

According to some embodiments of the method 400 illustrated in FIG. 4, the parameter information received by the RLC transmitting entity includes at least one of:

In some embodiments of the method 400 illustrated in FIG. 4, in response to receiving the parameter information from the RLC receiving entity and in response to the parameter information including the 1st index value of the 1st ADU (e.g., ADUIndexToDiscard) , during performing the discarding operation of the RLC transmitting entity, the RLC transmitting entity may:

(1) check whether “an index value (which is marked as “the 2nd index value” for simplicity) of an ADU (which is marked as “the 2nd ADU” for simplicity) to which the 2nd packet belongs” is equal to “the 1st index value of the 1st ADU” (e.g., ADUIndexToDiscard) ; and

In some embodiments of the method 400 illustrated in FIG. 4, in response to receiving the parameter information from the RLC receiving entity and in response to the parameter information including the 1st index value of the 1st ADU (e.g., ADUIndexToDiscard) and the 1st index number of the 1st packet (e.g., NumberInUnitToDiscard) , during performing the discarding operation of the RLC transmitting entity, the RLC transmitting entity may:

(2) check whether “an index number (which is marked as “the 2nd index number” for simplicity) of the 2nd packet in the group of packets belonging to the 1st ADU” is greater than “the 1st index number of the 1st packet” (e.g., NumberInUnitToDiscard) , in response to the 2nd index value of the 2nd ADU being equal to the 1st index value of the 1st ADU; and

In some embodiments of the method 400 illustrated in FIG. 4, in response to receiving the parameter information from the RLC receiving entity and in response to the parameter information including the 1st index value of the 1st ADU (e.g., ADUIndexToDiscard) and the 1st importance level of the 1st packet (e.g., ImportanceToDiscard) , during performing the discarding operation of the RLC transmitting entity, the RLC transmitting entity may:

In some embodiments of the method 400 illustrated in FIG. 4, in response to receiving the parameter information from the RLC receiving entity and in response to the parameter information including the 1st SN value of the 1st packet (e.g., SNToDiscard) and the 1st offset value related to the 1st SN value (e.g., Offset) , during performing the discarding operation of the RLC transmitting entity, the RLC transmitting entity may:

(1) check whether “a SN value (which is marked as “the 2nd SN value” for simplicity) of the 2nd packet” is greater than “the 1st SN value of the 1st packet” (e.g., SN > SNToDiscard) ;

(2) check whether “the 2nd SN value minus the 1st offset value related to the 1st SN value” is less than or equal to the 1st SN value, in response to the 2nd SN value being greater than the 1st SN value (e.g., ‘SN –Offset’ <= SNToDiscard) ; and

(3) discard the 2nd packet in the transmitting buffer, in response to “the 2nd SN value minus the 1st offset value” being less than or equal to the 1st SN value.

In some embodiments of the method 400 illustrated in FIG. 4, in response to receiving the parameter information from the RLC receiving entity and in response to the parameter information including the 1st SN value of the 1st packet (e.g., SNToDiscard) , during performing the discarding operation of the RLC transmitting entity, the RLC transmitting entity may:

(1) determine the 2nd SN value of the 2nd packet and the 2nd offset value related to the 2nd SN value based on packet header information of the 2nd packet;

(2) check whether “the 2nd SN value of the 2nd packet” is greater than “the 1st SN value of the 1st packet” ;

(3) check whether “the 2nd SN value minus the 2nd offset value related to the 2nd SN value” is less than or equal to “the 1st SN value of the 1st packet” , in response to the 2nd SN value being greater than the 1st SN value; and

(4) discard the 2nd packet in the transmitting buffer, in response to “the 2nd SN value minus the 2nd offset value” being less than or equal to “the 1st SN value of the 1st packet” .

It is contemplated that the method illustrated in FIG. 4 may include other operation (s) not shown, for example, any operation (s) described with respect to FIGS. 2, 3, 5, and 6.

Details described in all other embodiments of the present application (for example, details regarding a mechanism for supporting a packet discarding operation in RLC layer due to a packet loss) are applicable for the embodiments of FIG. 4. Moreover, details described in the embodiments of FIG. 4 are applicable for all embodiments of FIGS. 1-3, 5, and 6. It should be appreciated by persons skilled in the art that the sequence of the operations in exemplary procedure in the embodiments of FIG. 4 may be changed and some of the operations in exemplary procedure in the embodiments of FIG. 4 may be eliminated or modified, without departing from the spirit and scope of the disclosure.

FIGS. 5 and 6 show some specific embodiments of the methods as shown and illustrated in FIGS. 2-4. The embodiments of FIGS. 5 and 6 assume that the packets are related to one XR service and correlated with each other. For example, each packet (i.e., an RLC PDU) is associated with an ADU or GOP index, number in the unit (i.e., the number of frames in the same ADU or GOP) , and an importance level. One ADU or GOP has multiple frames correlated to each other. Packets belonging to the same ADU or GOP are correlated to each other, e.g., for instance, if the 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 are of different importance levels, e.g., the I-frame packets are of a higher importance level than P-frames and B-frames. In the embodiments of FIGS. 5 and 6, a packet can be an UMD PDU, an AMD PDU, a segment of a PDU, an UMD SDU, an AMD SDU, or a segment of a SDU.

In step 501 as shown in FIG. 5, RLC UM/AM Rx entity 510 makes a packet discarding decision. In step 502, RLC UM/AM Rx entity 510 transmits “parameter information regarding a discarding operation of RLC UM/AM Tx entity 520” to RLC UM/AM Tx entity 520.

For instance, if RLC UM/AM Rx entity 510 (e.g., which may be an RLC UM receiving entity) determines a packet loss in an RLC UM data transfer procedure or decides to discard relevant received packets in the receiving buffer (which may also be named as a reception buffer) , RLC UM/AM Rx entity 510 may transmit “parameter information regarding the packet loss and a discarding operation of RLC UM/AM Rx entity 510” to RLC UM/AM Tx entity 520 (e.g., which may be an RLC UM transmitting entity) . The parameter information can be transmitted via PUCCH signalling, a MAC CE or an RLC control PDU (e.g., RLC status report or new RLC control PDU) . The parameter information may include “ADUIndexToDiscard” value, and optionally “NumberInUnitToDiscard” value or “ImportanceToDiscard” value.

In step 503 as shown in FIG. 5, upon receiving the parameter information from RLC UM/AM Rx entity 510, RLC UM/AM Tx entity 520 will discard packet (s) (e.g., UM PDU (s) ) in the transmitting buffer which is correlated to the discarded packet (s) indicated by RLC UM/AM Rx entity 510. For instance, RLC UM/AM Tx entity 520 may perform one of:

1) Stop transmitting and discard the rest packets (including both packets in the current transmission buffer and future arriving packets) associated with the ADU index same as ADUIndexToDiscard.

2) Stop transmitting and discard the rest packets (including both packets in the current transmission buffer and future arriving packets) associated with the ADU index same as ADUIndexToDiscard and with number in unit greater than NumberInUnitToDiscard, if provided.

3) Stop transmitting and discard the rest packets (including both packets in the current transmission buffer and future arriving packets) associated with the ADU index same as ADUIndexToDiscard and with importance level lower than ImportanceToDiscard, if provided.

In the embodiments illustrated in FIG. 5, there may be different operations of RLC UM/AM Rx entity 510 in an RLC UM data transfer procedure or an RLC AM data transfer procedure, which are described as below.

According to some embodiments of FIG. 5, in an RLC UM data transfer procedure, RLC UM Rx entity 510 may detect a packet loss or perform a packet discarding operation. For example, RLC UM Rx entity 510 detects a packet loss in case that segments associated with one SN are discarded before all received due to an expiry of timer t-Reassembly. For an RLC UM data transfer procedure, RLC UM Tx entity 520 does not know any packet loss of RLC UM Rx entity 510, and thus a packet discarding operation of RLC UM Rx entity 510 can be only triggered by RLC UM Tx entity 520.

In some embodiments, when RLC UM Rx entity 510 detects UMD PDU loss for an RLC UM data radio bearer, RLC UM Rx entity 510 may discard one or multiple received UMD PDUs that are dependent on the lost UMD PDU (e.g., belong to the same ADU or GOP) .

According to some embodiments, whether a packet discarding operation according to ADU or GOP is allowed to a given data radio bearer is configured by a network node. It might also imply whether the RLC PDU header will include information about ADU or GOP, a number in unit, or importance level information. For example, once RLC UM Rx entity 510 makes a packet discarding decision, RLC UM Rx entity 510 also notifies RLC UM Tx entity 520 about the packet discarding decision, e.g., by indicating the ADUIndexToDiscard.

According to some embodiments, if the lost packet is associated with a certain ADU or GOP indicated by an ADU or GOP index and is the number “N” packet in the ADU or GOP indicated by the number in the unit, RLC UM Rx entity 510 will discard other packet (s) belonging to the same ADU or GOP and with the number of unit greater than “N” . The information about the lost packet may be indicated by an upper layer of RLC UM Rx entity 510.

In some embodiments, when an UMD PDU is received from a lower layer, RLC UM Rx entity 510 shall check whether the associated ADU index equals to ADUIndexToDiscard and whether the associated number in the unit is greater than NumberInUnitToDiscard. If so, RLC UM Rx entity 510 shall discard the received UMD PDU. One specific embodiment may be as follows:

● When an UMD PDU is received from a lower layer, RLC UM Rx entity 510 shall:

- if the associated ADU index equals to ADUIndexToDiscard and the associated number in the unit is greater than NumberInUnitToDiscard.

- discard the received UMD PDU.

- if the UMD PDU header does not contain an SN:

- remove the RLC header and deliver the RLC SDU to upper layer.

- else if (RX_Next_Highest –UM_Window_Size) <= SN < RX_Next_Reassembly:

- discard the received UMD PDU.

- else:

- place the received UMD PDU in the reception buffer.

In some embodiments, when RLC UM Rx entity 510 discards UMD PDUs with packet (s) outside a reassemble window, RLC UM Rx entity 510 discards other UMD PDU (s) in the RLC receiving buffer with an ADU index which is equal to an ADU index associated with the lost UMD PDU and (optionally) the associated number in the unit which is greater than the number in unit associated with the lost UMD PDU. RLC UM Rx entity 510 may update or set values of ADUIndexToDiscard and NumberInUnitToDiscard. For example, the value of ADUIndexToDiscard may be updated or set to the largest ADU index associated with the discarded UMD PDU (s) , and the value of NumberInUnitToDiscard may be updated or set to the largest number in unit value associated with the discarded UMD PDU (s) . Then, RLC UM Rx entity 510 may transmit information including ADUIndexToDiscard and/or NumberInUnitToDiscard to RLC UM Tx entity 520.

In an embodiment, upon discarding the relevant UMD PDU (s) , RLC UM Rx entity 510 updates or sets an UM receiving state variable (e.g., RX_Next_Reassembly) to a SN value of the first packet that has not been reassembled. One specific embodiment may be as follows:

● When t-Reassembly expires, the RLC UM receiving entity shall:

- update RX_Next_Reassembly to the SN of the first SN >= RX_Timer_Trigger that has not been reassembled;

- discard all segments with SN < updated RX_Next_Reassembly;

- update ADUIndexToDiscard to the largest ADU index associated with the discarded segments (e.g., UMD PDUs)

- update NumberInUnitToDiscard the largest number in unit value associated with the discarded segments (e.g., UMD PDUs)

- discard other UMD PDUs in the RLC reception buffer with ADU index equals to ADUIndexToDiscard and the associated number in the unit is greater than the NumberInUnitToDiscard

- if RX_Next_Highest > RX_Next_Reassembly + 1; or

- if RX_Next_Highest = RX_Next_Reassembly + 1 and there is at least one missing byte segment of the RLC SDU associated with SN = RX_Next_Reassembly before the last byte of all received segments of this RLC SDU:

- start t-Reassembly;

- set RX_Timer_Trigger to RX_Next_Highest.

According to some embodiments, if the lost packet is associated with a certain ADU or GOP indicated by an ADU or GOP index and is of importance level “M” , RLC UM Rx entity 510 will discard other packet (s) belonging to the same ADU or GOP and of a lower importance level than the lost packet importance level “M” . The information about the lost packet may be indicated by an upper layer of RLC UM Rx entity 510.

In some embodiments, when an UMD PDU is received from a lower layer, RLC UM Rx entity 510 shall check whether the associated ADU index equals to ADUIndexToDiscard and whether the associated importance level is less than ImportanceToDiscard. If so, RLC UM Rx entity 510 shall discard the received UMD PDU. For example, the value of ImportanceToDiscard is configured by a network node via radio resource control (RRC) signalling.

In some embodiments, when RLC UM Rx entity 510 discards UMD PDUs with packet (s) outside a reassemble window, RLC UM Rx entity 510 discards the other UMD PDUs in the RLC receiving buffer with “an ADU index equals to the ADU index associated with the lost UMD PDU” and “the associated importance level less than ImportanceToDiscard” . Then, RLC UM Rx entity 510 may update or set the value of ADUIndexToDiscard. In an embodiment, the value of ADUIndexToDiscard may be updated or set to the largest ADU index associated with the discarded UMD PDU (s) . Then, RLC UM Rx entity 510 may transmit information including ADUIndexToDiscard to RLC UM Tx entity 520. In an embodiment, upon discarding the relevant UMD PDU (s) , among the remaining RLC UMD PDU (s) in the RLC receiving buffer, an UM receiving state variable (e.g., RX_Next_Reassembly) may be updated or set to a SN value of the first packet that has not been reassembled.

According to some other embodiments of FIG. 5, in an RLC AM data transfer procedure, RLC AM Rx entity 510 may the RLC AM receiving entity may discard one or multiple received AMD PDU (s) that are dependent on the lost AMD PDU and belonging to the same ADU or GOP without causing an RLC failure. For an RLC AM data transfer procedure, both RLC AM Rx entity 510 and RLC AM Tx entity 520 know the packet loss, and thus a packet discarding operation of RLC AM Rx entity 510 can be only triggered by any side and inform the peer side.

In some embodiments, an AMD PDU discard operation is triggered by RLC AM Rx entity 510. Whether the AMD PDU discard operation according to the lost AMD PDU is allowed to a given data radio bearer is configured by a network node. It might also imply whether the RLC PDU header will include information about correlation with other AMD PDU (s) (e.g., an offset value means that it depends on an offset number of AMD PDUs before it, an ADU or a GOP, a number in unit, or importance level information) .

In some embodiments, RLC AM Rx entity 510 receives an indication from the peer RLC AM transmitting entity, i.e., RLC AM Tx entity 520, about an AMD PDU discarding operation triggered by RLC AM Tx entity 520. For example, the indication may imply at least one of:

1) SNtoDiscard value and optionally an Offset value related to SNtoDiscard value.

2) ADUIndexToDiscard value, and optionally NumberInUnitToDiscard value or ImportanceToDiscard value decided by RLC AM Tx entity 520.

In some embodiments, once RLC AM Rx entity 510 performs the AMD PDU discarding operation, RLC AM Rx entity 510 also notifies information about the AMD PDU discarding operation, e.g., by indicating ADUIndexToDiscard, to RLC AM Tx entity 520.

In an embodiment, the RLC AM packet contains an offset value, which means that the current RLC AM packet has dependency on the offset number of an RLC AM packet before it, and any loss of the previous offset number of RLC AM packet will make the current RLC AM packet useless.

In an example, when an RLC AM packet is received from a lower layer, RLC AM Rx entity 510 shall check whether the associated SN value (e.g., SN1) and Offset value fulfill “SN1 > SNToDiscard” and “ ‘SN1 –Offset’ <= SNToDiscard” . If so, RLC AM Rx entity 510 shall discard the received RLC AM packet.

For instance, assuming that there are 8 RLC packets (SDU or PDU or segment) with SN values “1, 2, 3, 4, 5, 6, 7, 8” and offset values of these 8 RLC packets are “0, 1, 2, 3, 4, 0, 1, 2” , if the RLC packet with “SN value = 2” and “Offset = 1” is lost, SNToDiscard = 2. Then, for each RLC packet within other 7 RLC packets, RLC AM Rx entity 510 shall check whether the RLC packet fulfills “the associated SN value > SNToDiscard” and “ ‘SN –offset’ <= SNToDiscard” . In particular:

1) Regarding the RLC packet with “SN value = 1” and “Offset = 0” , since “SN value = 1” is less than “SNToDiscard = 2” , it does not fulfill “the associated SN value > SNToDiscard” . Thus, RLC AM Rx entity 510 will not discard this RLC packet.

2) Regarding the RLC packet with “SN value = 3” and “Offset = 2” , it fulfills “the associated SN value > SNToDiscard” ( “SN value = 3” is greater than “SNToDiscard = 2” ) and “ ‘SN –Offset’ <= SNToDiscard” (3 –2 = 1, which is less than 2) . Thus, RLC AM Rx entity 510 will discard this RLC packet. Similarly, RLC AM Rx entity 510 will discard both the RLC packet with “SN value = 4” and “Offset = 3” and the RLC packet with “SN value = 5” and “Offset = 4” .

3) Regarding the RLC packet with “SN value = 6” and “Offset = 0” , since 6 –0 = 6, which is greater less than 2, it does not fulfill “ ‘SN –Offset’ <= SNToDiscard” . Thus, RLC AM Rx entity 510 will not discard this RLC packet. Similarly, RLC AM Rx entity 510 will not discard both the RLC packet with “SN value = 7” and “Offset = 1” and the RLC packet with “SN value = 8” and “Offset = 2” .

In a further example, if RLC AM Rx entity 510 determines a loss of an RLC AM packet with a SN value marked as “SNLost” , RLC AM Rx entity 510 will discard relevant RLC AM packet (s) with associated SN value (e.g., SN2) and Offset value fulfilling “SN2 > SNLost” and “ ‘SN2 –Offset’ <= SNLost” in the receiving buffer. For instance, assuming that an RLC AM data PDU header contains “SN value = 100” and “an offset value = 10” , any loss of an RLC AM packet with a SN value within a range of “90 ～ 99” will make the current RLC AM PDU useless and thus the current RLC AM PDU can be discarded.

In some embodiments, RLC AM Rx entity 510 will update or set SNToDiscard to the largest SN value associated with the discarded RLC AM packets. Then, RLC AM Rx entity 510 may transmit information including SNToDiscard to RLC AM Tx entity 520.

In some further embodiments, upon discarding the relevant RLC AM packet (s) , among the remaining RLC AM packets in the reception buffer, a receiving state variable (e.g., RX_Next) is updated to the SN value of the first RLC SDU with “SN > current RX_Next” and for which not all bytes have been received. A receiving state variable status trigger value (e.g., RX_Next_Status_Trigger) may be updated to “RX_Next + 1” .

In some embodiments, if the lost packet is associated with a certain ADU or GOP indicated by an ADU or GOP index and is the number “N” packet in the ADU or GOP indicated by the number in the unit, the RLC AM receiving entity will discard the other packets belonging to the same ADU or GOP and (optionally) with the number of unit greater than “N” .

In an embodiment, when an AMD PDU is received from a lower layer, RLC AM Rx entity 510 shall check whether the associated ADU index equals to ADUIndexToDiscard and whether the associated number in the unit is greater than NumberInUnitToDiscard. If so, RLC AM Rx entity 510 shall discard the received AMD PDU. One specific embodiment may be as follows:

● When an AMD PDU is received from a lower layer, where the AMD PDU contains byte segment numbers y to z of an RLC SDU with SN = x, the receiving side of an AM RLC entity shall:

- if x falls outside of the receiving window; or

- if the associated ADU index equals to ADUIndexToDiscard and the associated number in the unit is greater than the NumberInUnitToDiscard

- if byte segment numbers y to z of the RLC SDU with SN = x have been received before:

- discard the received AMD PDU.

- else:

- place the received AMD PDU in the reception buffer;

- if some byte segments of the RLC SDU contained in the AMD PDU have been received before:

- discard the duplicate byte segments.

In some embodiments, when RLC AM Rx entity 510 detects an AMD PDU reception failure, when timer t-Reassembly expires, RLC AM Rx entity 510 discards the other AMD PDUs in the RLC reception buffer with “an ADU index equals to an ADU index associated with the lost AMD PDU” and “the associated number in the unit is greater than the number in unit associated with the lost AMD PDU” . Then, RLC AM Rx entity 510 updates or sets the value of ADUIndexToDiscard and/or NumberInUnitToDiscard. For example, the value of ADUIndexToDiscard is updated to the largest ADU index associated with the discarded AMD PDU (s) , and the value of NumberInUnitToDiscard is updated to the largest number in unit value associated with the discarded AMD PDU (s) . After that, RLC UM Rx entity 510 may transmit information including ADUIndexToDiscard and/or NumberInUnitToDiscard to RLC UM Tx entity 520.

In an embodiment, upon discarding the relevant AMD PDU (s) , among the remaining RLC AMD PDU (s) in the reception buffer, a receiving state variable (e.g., RX_Next) is updated to the SN value of the first RLC SDU with “SN > current RX_Next” and for which not all bytes have been received. A receiving state variable status trigger value (e.g., RX_Next_Status_Trigger) may be updated to “RX_Next +1” .

In some embodiments, if the lost packet is associated with a certain ADU or GOP indicated by an ADU or GOP index and is of importance level value “M” , RLC AM Rx entity 510 will discard the other packets belonging to the same ADU or GOP and of a lower importance level than importance level value “M” of the lost packet.

In an embodiment, when an AMD PDU is received from a lower layer, the receiving AM RLC entity shall check whether the associated ADU index equals to ADUIndexToDiscard and whether the associated importance level is below ImportanceToDiscard. If so, RLC AM Rx entity 510 shall discard the received AMD PDU. ImportanceToDiscard may be configured by a network node.

In a further embodiment, when RLC AM Rx entity 510 detects an AMD PDU reception failure upon timer t-Reassembly expiry, RLC AM Rx entity 510 discards relevant AMD PDU (s) in the RLC reception buffer with “ADU index equals to ADU index associated with the lost AMD PDU” and “the associated number in the unit is greater than the number in unit associated with the lost AMD PDU” . Then, RLC AM Rx entity 510 update or set the value of ADUIndexToDiscard. For instance, the value of ADUIndexToDiscard is updated to the largest ADU index associated with the discarded AMD PDU (s) . After that, RLC AM Rx entity 510 may transmit information including ADUIndexToDiscard to RLC AM Tx entity 520. In an example, upon discarding the relevant AMD PDU (s) , among the remaining RLC AMD PDU (s) , a receiving state variable (e.g., RX_Next) is updated to the SN of the first RLC SDU with “SN > current RX_Next” and for which not all bytes have been received. A receiving state variable status trigger value (e.g., RX_Next_Status_Trigger) may be updated to “RX_Next + 1” .

In some embodiments, NumberOfReceptionFailure is configured to RLC AM Rx entity 510 by a network node. When the number of reception failure detected for the same RLC AMD PDU exceeds NumberOfReceptionFailure, e.g., “timer t-Reassembly expires a number of times greater than NumberOfReceptionFailure” and “the same missing RLC AMD PDU has not been received yet” , RLC AM Rx entity 510 will discard the relevant RLC AMD PDUs, e.g., based on conditions related to “SNToDiscard and/or Offset” or “ADUIndexToDiscard and/or NumberInUnitToDiscard” or “ADUIndexToDiscard and/or ImportanceToDiscard” described in any of the abovementioned embodiments.

In some embodiments, if RLC AM Rx entity 510 determines a packet loss and decides to discard relevant received packet (s) , RLC AM Rx entity 510 may also indicate the packet loss and a packet discarding decision to RLC AM Tx entity 520. In an embodiment, RLC AM Rx entity 510 can transmit such indication information via a PUCCH signalling, a MAC CE, or an RLC control PDU (e.g., an RLC status report or a new RLC control PDU) . The information may imply or include:

1) SNToDiscard value and optionally an Offset value; and/or

2) ADUIndexToDiscard value, and optionally NumberInUnitToDiscard or ImportanceToDiscard value decided by RLC AM Tx entity 520.

In some embodiments, upon receiving indication information about a packet discard operation from RLC AM Tx entity 520, RLC AM Rx entity 510 will discard those RLC AM packets in the reception buffer which is correlated to the discarded RLC AM packet (s) indicated by RLC AM Tx entity 520. For example:

1) For AMD PDU (s) in the reception buffer, RLC AM Rx entity 510 may discard those with the associated SN value and an offset value fulfilling “SN >SNToDiscard” and “ ‘SN -Offset’ <= SNToDiscard” .

2) For AMD PDU (s) in the reception buffer, RLC AM Rx entity 510 may discard those associated with “the ADU index which is the same as ADUIndexToDiscard” .

3) For AMD PDU (s) in the reception buffer, RLC AM Rx entity 510 may discard those associated with “the ADU index which is the same as ADUIndexToDiscard” and with “a number in unit which is greater than NumberInUnitToDiscard, if applicable” .

4) For AMD PDU (s) in the reception buffer, RLC AM Rx entity 510 may discard those associated with “the ADU index which is same as ADUIndexToDiscard” and with “an importance level which is lower than ImportanceToDiscard” , if applicable.

In some embodiments, upon discarding the relevant AMD PDU (s) , among the remaining RLC AMD PDU (s) , RX_Next is updated to the SN of the first RLC SDU with SN > current RX_Next and for which not all bytes have been received. RX_Next_Status_Trigger is updated to “RX_Next + 1” . In some embodiments, SNToDiscard, ADUIndexToDiscard, NumberInUnitToDiscard, ImportanceToDiscard are set to the values indicated by RLC AM Tx entity 520.

Details described in all other embodiments of the present application (for example, details regarding a mechanism for supporting a packet discarding operation in RLC layer due to a packet loss) are applicable for the embodiments of FIG. 5. Moreover, details described in the embodiments of FIG. 5 are applicable for all the embodiments of FIGS. 1-4 and 6.

FIG. 6 illustrates an exemplary flow chart of a packet discarding operation in an RLC AM transmitting entity according to some embodiments of the present application. In the legacy, for an RLC AM transmitting entity, if a maximum RLC retransmission number is exceeded, an RLC failure event will be triggered, and it may cause a connection re-establishment procedure. In the embodiments of FIG. 6, after few times RLC retransmission attempts for one RLC AMD PDU, RLC AM Tx entity 620 of an AM data radio bearer (DRB) may decide to discard relevant RLC AMD PDU (s) in its transmitting buffer (which may also be named as a transmission buffer) .

In step 601 as shown in FIG. 6, RLC AM Tx entity 620 makes a packet discarding decision. In step 602, RLC AM Tx entity 620 transmits “parameter information regarding a discarding operation of RLC AM Rx entity 610” to RLC Rx entity 610. In step 603, RLC AM Rx entity 610 discard relevant packets.

According to some embodiments, it is upon NW configuration whether RLC packet discard is supported for the radio bearer, such that offset, ADU/GOP information is carried in the RLC packet header. Besides, the number of RLC retransmission failure which triggers packet discard at the RLC AM transmitting entity is configured by the network and is a different value than the maximum number of RLC AM retransmission.

According to some embodiments, if the number of RLC retransmission attempts exceeds the maximum number of RLC retransmission, instead of triggering an RLC failure and connection reestablishment, the RLC transmitting entity will discard the relevant RLC AMD PDU (s) .

In some embodiments, it is upon NW configuration (e.g., via RRC message) , whether exceeding the maximum number of RLC retransmission will lead to RLC failure or discarded RLC AMD PDU. For instance, RLC AM Tx entity 620 may perform one of:

1) Stop transmitting and discard the rest packets in the current transmission buffer (which does not impact future arriving packets) with associated SN and offset value fulfilling “SN > SNToDiscard” and “ ‘SN-offset’ <=SNToDiscard” .

2) stop transmitting and discard the rest packets (including both packets in the current transmission buffer and future arriving packets) associated with the ADU index same as ADUIndexToDiscard.

3) stop transmitting and discard the rest packets (including both packets in the current transmission buffer and future arriving packets) associated with the ADU index same as ADUIndexToDiscard and with number in unit greater than NumberInUnitToDiscard, if applicable.

4) stop transmitting and discard the rest packets (including both packets in the current transmission buffer and future arriving packets) associated with the ADU index same as ADUIndexToDiscard and with importance level lower than ImportanceToDiscard, if applicable.

According to some embodiments, if the RLC AMD PDU discard is triggered by RLC AM Tx entity 620 itself:

1) SNToDiscard is set to the SN value associated with the RLC packet in the transmission buffer which triggers the RLC packet discarding operation.

2) ADUIndexToDiscard is set to the ADU index value associated with the RLC AMD PDU in the transmission buffer which triggers the RLC AMD PDU (s) discarding operation.

3) NumberInUnitToDiscard is set to the number in unit value associated with the RLC AMD PDU in the transmission buffer which triggers the RLC AMD PDU (s) discarding operation.

4) ImportanceToDiscard is either set to the importance level value associated with the RLC AMD PDU in the transmission buffer which triggers the RLC AMD PDU (s) discarding operation, or set to an ImportanceToDiscard value configured by a network node in advance.

In some embodiments, if RLC AM Tx entity 620 determines the packet loss and decides to discard relevant packet (s) , RLC AM Tx entity 620 may also indicate the packet discard to RLC AM Rx entity 610. For example, such indication information can be sent via PDCCH signalling, a MAC CE, or a new RLC control PDU. The indication information may imply or include:

1) SNToDiscard value and optionally an offset value; and/or

2) ADUIndexToDiscard value, and optionally NumberInUnitToDiscard or ImportanceToDiscard value decided by RLC AM Tx entity 620.

According to some embodiments, if the RLC AMD PDU discard is triggered by receiving the RLC AMD PDU discard decision from RLC AM Rx entity 610, SNToDiscard, ADUIndexToDiscard, NumberInUnitToDiscard, ImportanceToDiscard are set to the values as indicated by RLC AM Rx entity 610.

In some embodiments, upon discarding the relevant RLC AMD PDUs, among the remaining RLC AMD PDUs in the transmission buffer, an acknowledgement state variable (e.g., TX_Next_Ack) may be set to be equal to the SN value of the RLC SDU with the smallest SN value, whose SN value falls within the range “TX_Next_Ack <= SN <= TX_Next” and for which a positive acknowledgment has not been received yet.

Details described in all other embodiments of the present application (for example, details regarding a mechanism for supporting a packet discarding operation in RLC layer due to a packet loss) are applicable for the embodiments of FIG. 6. Moreover, details described in the embodiments of FIG. 6 are applicable for all the embodiments of FIGS. 1-5.

The method (s) of the present disclosure can be implemented on a programmed processor. However, controllers, flowcharts, and modules may also be implemented on a general purpose or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a hardware electronic or logic circuit such as a discrete element circuit, a programmable logic device, or the like. In general, any device that has a finite state machine capable of implementing the flowcharts shown in the figures may be used to implement the processing functions of the present disclosure.

While this disclosure has been described with specific embodiments thereof, it is evident that many alternatives, modifications, and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added, or substituted in the other embodiments. Also, all of the elements of each figure are not necessary for operation of the disclosed embodiments. For example, those having ordinary skills in the art would be enabled to make and use the teachings of the disclosure by simply employing the elements of the independent claims. Accordingly, embodiments of the disclosure as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure.

In this document, the terms "includes, " "including, " or any other variation 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 to such process, method, article, or apparatus. An element proceeded by "a, " "an, " or the like does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that includes the element. Also, the term "another" is defined as at least a second or more. The term "having" and the like, as used herein, are defined as "including.

Claims

A radio link control (RLC) receiving entity, comprising:

a processor; and

a transceiver coupled to the processor,

wherein the processor is configured:

to detect a packet loss or to receive, via the transceiver from an RLC transmitting entity, first parameter information regarding a first discarding operation of the RLC receiving entity, wherein the packet loss or the first discarding operation is associated with a first packet; and

to perform the first discarding operation to discard a second packet related to the first packet in a receiving buffer, in response to detecting the packet loss or in response to receiving the first parameter information.
The RLC receiving entity of Claim 1, wherein the first packet and the second packet belong to one application data unit (ADU) or one group of picture (GOP) .
The RLC receiving entity of Claim 1, wherein the first parameter information includes at least one of:

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 sequence number (SN) value of the first packet; or

a first offset value related to the first SN value of the first packet.
The RLC receiving entity of Claim 3, wherein in response to receiving the first parameter information and in response to the first parameter information including the first SN value of the first packet, during performing the first discarding operation, the processor of the RLC receiving entity is configured:

to determine a second SN value of the second packet and a second offset value related to the second SN value based on packet header information of the second packet;

to check whether the second SN value of the second packet is greater than the first SN value of the first packet;

to check whether the second SN value minus the second offset value related to the second SN value is less than or equal to the first SN value, in response to the second SN value being greater than the first SN value; and

to discard the second packet in the receiving buffer, in response to the second SN value minus the second offset value being less than or equal to the first SN value.
The RLC receiving entity of Claim 1, wherein in response to detecting the packet loss, during performing the first discarding operation, the processor of the RLC receiving entity is configured:

to determine a second SN value of the second packet and a second offset value related to the second SN value based on packet header information of the second packet;

to check whether the second SN value of the second packet is greater than a first SN value of the first packet;

to check whether the second SN value minus the second offset value is less than or equal to the first SN value, in response to the second SN value being greater than the first SN value; and

to discard the second packet in the receiving buffer, in response to the second SN value minus the second offset value being less than or equal to the first SN value.
The RLC receiving entity of Claim 5, the processor of the RLC receiving entity is configured:

to generate second parameter information regarding a second discarding operation of the RLC transmitting entity, wherein the second discarding operation is associated with the first packet, and wherein the second parameter information includes at least one of:

a largest one between the first index value of the first ADU and the second index value of the second ADU;

a largest one between the first index number of the first packet and the second index number of the second packet;

a largest one between the first importance level of the first packet and the second importance level of the second packet;

a largest one between the first SN value of the first packet and the second SN value of the second packet; or

the second offset value related to the second SN value; and

to transmit the second parameter information via the transceiver to the RLC transmitting entity.
The RLC receiving entity of Claim 1, wherein the processor of the RLC transmitting entity is configured to receive, via the transceiver from a network node, configuration information regarding whether the first discarding operation is supported for a radio bearer.
The RLC receiving entity of Claim 1, wherein the processor of the RLC receiving entity is configured:

to determine a third SN value of a third packet and a third offset value related to the third SN value based on packet header information of the third packet, in response to receiving the third packet from the RLC transmitting entity;

to check whether the third SN value of the third packet is greater than a first SN value of the first packet;

to check whether the third SN value minus the third offset value is less than or equal to the first SN value, in response to the third SN value being greater than the first SN value; and

not to store the third packet into the receiving buffer and to discard the third packet, in response to the third SN value minus the third offset value being less than or equal to the first SN value.
A radio link control (RLC) transmitting entity, comprising:

a processor; and

a transceiver coupled to the processor,

wherein the processor is configured:

to detect a packet loss or to receive, via the transceiver from an RLC receiving entity, first parameter information regarding a first discarding operation of the RLC transmitting entity, wherein the packet loss or the first discarding operation is associated with a first packet; and

to stop transmitting a second packet related to the first packet in a transmitting buffer and to perform the first discarding operation to discard the second packet, in response to detecting the packet loss or in response to receiving the first parameter information.
The RLC transmitting entity of Claim 9, wherein the first packet and the second packet belong to one application data unit (ADU) or one group of picture (GOP) .
The RLC transmitting entity of Claim 9, wherein the processor of the RLC transmitting entity is configured to receive, via the transceiver from a network node, at least one of:

configuration information regarding whether the first discarding operation is supported for a radio bearer; or

configuration information regarding an RLC retransmission failure number for triggering the first discarding operation, wherein the RLC retransmission failure number is different from a maximum RLC retransmission number of the RLC transmitting entity.
The RLC transmitting entity of Claim 9, wherein the first discarding operation is performed after the RLC transmitting entity performing a certain number of an RLC retransmission attempt operation for the first packet.
The RLC transmitting entity of Claim 9, wherein in response to detecting the packet loss, during performing the first discarding operation, the processor of the RLC transmitting entity is configured:

to determine a second SN value of the second packet and a second offset value related to the second SN value based on packet header information of the second packet;

to check whether the second SN value of the second packet is greater than a first SN value of the first packet;

to check whether the second SN value minus the second offset value related to the second SN value is less than or equal to the first SN value, in response to the second SN value being greater than the first SN value; and

to discard the second packet in the transmitting buffer, in response to the second SN value minus the second offset value being less than or equal to the first SN value.
The RLC transmitting entity of Claim 9, wherein the first parameter information includes at least one of:

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 sequence number (SN) value of the first packet; or

a first offset value related to the first SN value of the first packet.
The RLC transmitting entity of Claim 14, wherein in response to receiving the first parameter information and in response to the first parameter information including the first SN value of the first packet, during performing the first discarding operation, the processor of the RLC transmitting entity is configured:

to determine a second SN value of the second packet and a second offset value related to the second SN value based on packet header information of the second packet;

to check whether the second SN value of the second packet is greater than the first SN value of the first packet;

to check whether the second SN value minus the second offset value related to the second SN value is less than or equal to the first SN value, in response to the second SN value being greater than the first SN value; and

to discard the second packet in the transmitting buffer, in response to the second SN value minus the second offset value being less than or equal to the first SN value.