Methods for discarding RLC sdus, and user equipment

Abstract

Provided in the present invention are methods for discarding RLC SDUs, which are executed by an RLC entity of a base station or of a user equipment, and a user equipment. A method provided by one aspect of the present invention comprises: when a discard indication instructing to discard RLC SDUs is received from an upper layer, for each RLC SDU that should be discarded as indicated by the discard indication, if the RLC SDU that should be discarded or a segment of the RLC SDU that should be discarded has been delivered to a lower layer, updating a first state variable, such that the value of the first state variable is not equal to the sequence number of the RLC SDU that should be discarded, the first state variable indicating the sequence number of a next RLC SDU requiring positive acknowledgment from a peer.

Description

Method for discarding RLC SDU and user equipment Technical Field

[0001] The present invention relates to the field of wireless communication technology, and more particularly, to a method for discarding an RLC SDU executed by an RLC entity of a user equipment, and a corresponding base station and user equipment. Background Art

[0002] The RLC layer transmission can be divided into three modes: AM, UM, and TM. In the AM mode, the ARQ transmission mechanism ensures the reliability of data transmission.

[0003] However, in order to achieve this reliability, the UE will continue to send data packets that have not been correctly received by the other end until the transmission is successful or the maximum number of times allowed is reached, which will cause data transmission delay problems. For service data types that are not sensitive to delay, such transmission is reliable, but for service data that is sensitive to delay, such transmission method is less effective. In particular, in some transmission scenarios, some service data becomes irrelevant after exceeding a certain transmission time, and can even be discarded. However, the existing RLC AM transmission mode will cause such data to be transmitted again and again, wasting transmission resources. Therefore, it is necessary to solve the above problems to achieve reliable and efficient transmission. Summary of the Invention

[0004] The object of the present invention is to provide a method and user equipment for discarding RLC SDUs that can avoid wasting transmission resources.

[0005] According to one aspect of the present invention, a method for discarding RLC SDU performed by an RLC entity of a base station or a user equipment is provided, the method comprising: when a discard indication indicating the discard of an RLC SDU is received from an upper layer, for each RLC SDU to be discarded indicated by the discard indication, if the RLC SDU to be discarded or a fragment of the RLC SDU to be discarded has been delivered to a lower layer, updating a first state variable so that the value of the first state variable is not equal to the sequence number of the RLC SDU to be discarded, the first state variable representing the sequence number of the next RLC SDU that requires positive confirmation from the other end.

[0006] According to another aspect of the present invention, a method for discarding RLC SDUs performed by an RLC entity of a base station or a user equipment is provided, comprising: receiving discard indication information, the discard indication information including indication information of the RLC SDUs that have been discarded by the transmitting end; and for each discarded RLC SDU indicated by the indication information, updating a second state variable based on the sequence number of the discarded RLC SDU so that a positive confirmation generation process is not performed for the discarded RLC SDU, the second state variable including at least one of a maximum value between the sequence number of the last RLC SDU that has been completely received by the receiving end and the sequence number of the RLC SDU for which a positive confirmation has been generated.

[0007] According to another aspect of the present invention, a user equipment is provided, comprising: a processor; and a memory storing instructions; wherein the instructions, when executed by the processor, execute the method described above.

[0008] According to another aspect of the present invention, a base station is provided, comprising: a processor; and a memory storing instructions; wherein the instructions, when executed by the processor, execute the method described above.

[0009] According to the present invention, when an RLC SDU has been discarded, repeated data transmission due to failure to receive a positive acknowledgement for the discarded RLC SDU can be avoided, thereby avoiding waste of transmission resources.

[0010] In addition, according to the present invention, it is possible to avoid the receiving end from still generating and sending a positive acknowledgement for the RLC SDU when the transmitting end has discarded the RLC SDU, thereby avoiding waste of transmission resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG1 is a schematic diagram for explaining the RLC AM mode.

[0012] FIG2 is a flow chart of a method for discarding an RLC SDU executed by a user equipment at a transmitting end.

[0013] FIG3 is a flowchart of a method for discarding an RLC SDU performed by a receiving end.

[0014] FIG4 is a simplified structural block diagram of a user equipment UE according to the present invention. DETAILED DESCRIPTION

[0015] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the present invention is not limited to the specific embodiments described below. In addition, for the sake of simplicity, detailed descriptions of known technologies that are not directly related to the present invention are omitted to prevent confusion in understanding the present invention.

[0016] Before the detailed description, the following explanations are given for several terms mentioned in the present invention. Unless otherwise specified, the terms involved in the present invention have the following meanings.

[0017] UE User Equipment

[0018] NR New Radio Next Generation Wireless Technology

[0019] LTE Long Term Evolution

[0020] eLTE Enhaced Long Term Evolution

[0021] RRC Radio Resource Control (layer)

[0022] MAC Medium Access Control (layer)

[0023] PUSCH Physical Uplink Shared Channel Physical Uplink Shared Channel

[0024] PDCCH Physical Downlink Control Channel

[0025] RNA RAN-based Notification Area Notification area based on radio access network

[0026] SDAP Service Data Adaptation Protocol Service Data Adaptation Layer Protocol

[0027] AM Acknowledged Mode

[0028] AMD AM Data confirms model data

[0029] ARQ Automatic Repeat request Automatic Repeat request

[0030] gNB the next Generation Node B, next generation base station

[0031] PDU Protocol Data Unit

[0032] RLC Radio Link Control

[0033] SDU Service Data Unit

[0034] SN Sequence Number

[0035] The following describes multiple embodiments of the present invention using the NR mobile communication system and its subsequent evolutionary versions as example application environments, and base stations and UE devices supporting NR as examples. However, it should be noted that the present invention is not limited to the following embodiments, but is applicable to more other wireless communication systems, such as eLTE, communication systems, or NB-Iot systems, or LTE-M systems. It can also be applied to other base stations and UE devices, such as base stations and UE devices supporting eLTE / NB-Iot / LTE-M.

[0036] The functions of the RLC layer are implemented by the RLC entity. An RLC entity can receive one or more RLC SDUs from its upper layer, usually the PDCP layer, and then send the RLC PDUs corresponding to these RLC SDUs to the peer RLC entity via the lower layers, usually the MAC layer and the physical layer. An RLC entity can also receive one or more RLC PDUs from its peer RLC entity via the lower layers, and then deliver the RLC SDUs corresponding to these RLC PDUs to the upper layer.

[0037] RLC AM mode

[0038] As shown in Figure 1, in RLC AM mode, there is a transmitter and a receiver. Generally, the transmitter can be located on the gNB / UE side, while the receiver is located on another UE side, or vice versa.

[0039] The RLC data PDUs (RLC data PDUs) transmitted or received by an AM RLC entity are called AMD PDUs. An AMD PDU contains a complete RLC SDU or a segment of an RLC SDU (RLC SDU segment). The RLC control PDUs (RLC control PDUs) transmitted or received by an AM RCL entity include STATUS PDUs

[0040] The transmitting side of an AM RLC entity

[0041] The transmitting side maintains a transmission window according to the status variable TX_Next_Ack:

[0042] If TX_Next_Ack <= SN < TX_Next_Ack + AM_Window_Size, then this SN falls within the transmission window; otherwise, this SN falls outside the transmission window.

[0043] For SNs that fall outside the transmission window, the transmitting side will not deliver them to the lower layer for transmission.

[0044] For each RLC SDU received from the upper layer (PDCP), the RLC entity operating in the AM mode associates an SN with this RLC SDU. It can be considered that this SN is the SN of this RLC SDU or the SN associated with it. This SN is the value of the current variable TX_Next. Then an AMD PDU is generated, and the SN of this AMD PDU is set to the value of the current variable TX_Next. Then the value of the variable TX_Next is incremented by 1, that is, a new variable TX_Next is obtained, and its value is the value of the current variable TX_Next plus 1.

[0045] When delivering an AMD PDU containing an RLC SDU segment to the lower layer for transmission, the transmitting side of the AM RLC entity will set the SN of this AMD PDU to the SN associated with this RLC SDU.

[0046] The transmitting side of an AM RLC entity can receive a STATUS PDU sent from the RLC entity on the peer side (i.e., the receiving side of the AM RLC entity). This STATUS PDU is used by the RLC entity on the peer side to confirm to the transmitting side the successful reception of an RLC SDU, that is, to provide a positive acknowledgement (ACK) for an RLC SDU. When an RLC SDU is successfully received by the peer side or a positive acknowledgement for an RLC SDU is received from the peer side, the transmitting side of the RLC entity will indicate to the upper layer that the RLC SDU has been successfully transmitted, and then update the value of the variable TX_Next_Ack, setting its value to the smallest SN among one or more SNs that fall within the range TX_Next_Ack <= SN <= TX_Next and have not been successfully received and confirmed.

[0047] The receiving side of the RLC entity

[0048] The receiving side of an AM RLC entity

[0049] The receiving side maintains a receive window based on the status variable RX_Next.

[0050] If RX_Next <= SN < RX_Next + AM_Window Size, then this SN falls within the receive window; otherwise, it falls outside the receive window.

[0051] For the received AMD PDU, the receiving side of the AM RLC entity either discards the AMD PDU or stores it in the reception buffer.

[0052] For SNs that fall outside the receive window, the receiving side can discard the AMD PDU; in addition, for an AMD PDU that contains segments of an RLC SDU, if it is confirmed that the segment has been received, the receiving side can also discard the AM PDU.

[0053] For the AMD PDUs stored in the reception buffer, the receiving side can perform the following processing

[0054] Update one or more status variables, reassemble the RLC SDU, and deliver the reassembled RLC SDU to the upper layer, and if necessary, stop or start the corresponding timer.

[0055] Specifically, for an AMD PDU with SN=X, when it is stored in the receiving buffer,

[0056] If x>=RX_Next_Highest, then the value of RX_Next_Highest is updated, and the new value of RX_Next_Highest is the current value of RX_Next_Highest plus one.

[0057] If all segments of the RLC SDU associated with SN=X have been received, reassemble the segments into an RLC SDU and deliver the reassembled RLC SDU to the upper layer;

[0058] If x = RX_Highest_Status, then the value of RX_Highest_Status is updated, and the new value of RX_Highest_Status is: among all one or more SNs whose SN values ​​are greater than the current RX_Highest_Status value, select the SNs associated with the RLC SDUs for which all segments (or all bytes) have not been received, and then select the SN associated with the RLC SDU that ranks first. Here, the first in order can refer to sorting by the size of the SNs, with the SN with the smallest value ranked first. Then the updated value of RX_Highest_Status is the value of the SN with the smallest value.

[0059] If x=RX_Next, then the value of RX_Next is updated, and the new value of RX_Next is: among all one or more SNs whose SN values ​​are greater than the current RX_Next value, select the SNs associated with the RLC SDUs for which all segments (or all bytes) have not been received, and then select the SN associated with the RLC SDU that ranks first. Here, the first in order can refer to sorting by the size of the SNs, with the SN with the smallest value ranked first. Then the updated value of RX_Next is the value of the SN with the smallest value.

[0060] ARQ transmission

[0061] The transmitting end of the RLC entity can obtain a notification of reception failure or a negative acknowledgement (NACK) of the RLC SDU and RLC SDU segments by receiving a STATUS PDU from the other end.

[0062] When a negative acknowledgment is received for an RLC SDU, or a negative acknowledgment is received for a segment of an RLC SDU, if the SN value of the RLC SDU is greater than or equal to TX_Next_Ack and less than or equal to the maximum SN value in the AMD PDU delivered to the lower layer for transmission, then the RLC SDU or the segment of the RLC SDU is considered to need to be retransmitted.

[0063] When retransmitting an RLC SDU or a segment of an RLC SDU, a new AMD PDU may be generated and then delivered to the lower layer for transmission.

[0064] Discarding of RLC SDUs in Existing Mechanisms

[0065] When the UE's upper layer, the PDCP layer, instructs the RLC layer to discard a specific RLC SDU, the transmitting end of the RLC entity determines whether the RLC SDU or a segment of the RLC SDU has been delivered to the lower layer for transmission. If the RLC SDU or a segment of the RLC SDU has not been delivered to the lower layer for transmission, which means that all segments of the RLC SDU have not been delivered to the lower layer, then the transmitting end of the RLC entity can discard the RLC SDU; if the RLC SDU or a segment of the RLC SDU has been delivered to the lower layer for transmission, which means that at least one of the multiple segments has been delivered to the lower layer, then the transmitting end of the RLC entity does not perform any operation, but allows the RLC SDU or its segment to be sent to the other end according to the aforementioned process.

[0066] State variables

[0067] The value of the variable TX_Next_Ack is equal to the SN of the next RLC SDU for which a positive acknowledgment is to be received in-sequence. It also represents the acknowledgment starting sequence number of the sending window.

[0068] The value of the TX_Next variable is equal to the SN AM_Window_Size window size of the next newly generated AMD PDU

[0069] The value of the variable RX_Next is equal to the value of the SN following the last in-sequence completely received RLC SDU. It also represents the starting sequence number of the receive window.

[0070] RX_Next_Highest The highest sequence number received

[0071] RX_Highest_Status When constructing a STATUS PDU, the maximum or highest SN value indicated by the ACK_SN field in the STATUS PDU that is positively acknowledged by the receiver, that is, the highest sequence number in the STATUS PDU

[0072] The value of the variable RX_Next_Highest is equal to the highest sequence number in the status report of the value of the SN following the SN of the RLC SDU with the highest SN among received RLC SDUs.

[0073] Hereinafter, an outline of an embodiment of the present invention will be described with reference to FIG. 2 and FIG. 3 .

[0074] Figure 2 is a flow chart of a method for discarding an RLC SDU executed by a base station or user equipment. Specifically, the method is executed by a transmitting end of an RLC entity of the base station or user equipment.

[0075] As shown in FIG2 , in step 201 , the RLC entity receives a discard indication from an upper layer indicating that an RLC SDU should be discarded.

[0076] Then, in step 203, the RLC entity determines whether the RLC SDU or the segment thereof indicated by the discard indication to be discarded has been delivered to the lower layer.

[0077] If the RLC SDU or its fragment to be discarded has been delivered to the lower layer, the first state variable is updated so that the value of the first state variable is not equal to the sequence number of the RLC SDU to be discarded. Here, the first state variable represents the sequence number of the next RLC SDU that requires positive acknowledgment from the peer end.

[0078] As a specific example of updating the first state variable, RLC SDUs whose sequence numbers are within a given window starting from the current value of the first state variable and have not been positively confirmed and instructed to be discarded can be screened out, and then the minimum value among the sequence numbers of these RLC SDUs is assigned to the first state variable.

[0079] Furthermore, in step 207, a discard report is generated and sent to the opposite end, where the discard report includes indication information of the RLC SDU discarded by the user equipment at the transmitting end.

[0080] The discard report may include information indicating that the sequence number of the RLC SDU is within a given window starting from the current value of the first state variable. Although step 207 is shown after step 205 in FIG2 , step 207 may also be performed before step 205. In the case shown in FIG2 , the current first state variable is the updated first state variable. If step 207 is performed before step 205, the current first state variable is the first state variable before the update.

[0081] In addition, when the discard indication indicates a plurality of RLC SDUs to be discarded, the operations of steps 203 and 205 are respectively performed for each RLC SDU to be discarded.

[0082] If the RLC SDU or its fragment to be discarded has not been delivered to the lower layer, then in step 209, the sequence number of the RLC SDU to be discarded is removed.

[0083] In addition, although FIG2 shows that the RLC SDU to be discarded or its fragment has been delivered to the lower layer, the RLC SDU is discarded by updating the first state variable, the discarding method can also be selected according to the specific situation. This will be described in detail in the third embodiment described below.

[0084] In this embodiment, through the above-mentioned update operation, the value of the first state variable will not be locked to the sequence number of the discarded RLC SDU, so that data will not be repeatedly sent due to failure to receive a positive acknowledgement of the discarded RLC SDU.

[0085] Figure 3 is a flow chart of a method for discarding an RLC SDU executed by a base station or user equipment. Specifically, the method is executed by a receiving end of an RLC entity of the base station or user equipment.

[0086] As shown in Figure 3, in step 301, discard indication information is received, which includes indication information of RLC SDUs discarded by the transmitting end. The discard indication information can be received by receiving a discard report, which is sent from the user equipment or base station that sends data.

[0087] In step 303, for each discarded RLC SDU indicated by the indication information, the second state variable is updated based on the sequence number of the discarded RLC SDU, so that a positive acknowledgement generation process is not performed for the discarded RLC SDU.

[0088] The second state variable may be the sequence number (RX_Next) of the last RLC SDU that has been completely received by the receiving end. In this case, if the sequence number of the discarded RLC SDU is not less than the current second state variable, the second state variable is increased by a given value, thereby updating the second state variable.

[0089] The second state variable may also be the maximum value (RX_Highest_Status) among the sequence numbers of RLC SDUs for which positive acknowledgments have been generated. In this case, if the sequence number of the discarded RLC SDU is equal to the current value of the second state variable, the second state variable is updated so that the value of the second state variable is not equal to the sequence number of the discarded RLC SDU, thereby updating the second state variable. Specifically, RLC SDUs whose sequence numbers are greater than the current value of the second state variable and which have not been completely received or discarded can be screened out, and the minimum value among the sequence numbers of these RLC SDUs is assigned to the second state variable.

[0090] In one example, the second state variable may include both RX_Next and RX_Highest_Status. Upon receiving discard indication information, for each discarded RLC SDU, a determination may be made as to whether the sequence number of the discarded RLC SDU is not less than RX_Next. If so, a further determination may be made as to whether the sequence number of the discarded RLC SDU is equal to RX_Highest_Status. Alternatively, a determination may be made as to whether the sequence number is equal to RX_Highest_Status first. If not, a further determination may be made as to whether the sequence number is not less than RX_Next. The second state variable may also include only one of RX_Next and RX_Highest_Status, in which case only one of the aforementioned determinations may be performed.

[0091] Hereinafter, several embodiments of the present invention are described in detail.

[0092] It should be noted that the transmitting end and receiving end of the RLC entity in this article can be located at different UE sides, or at the base station and UE sides, or at the UE side and the base station side. In this article, the UE side is taken as an example.

[0093] Example 1

[0094] When the upper layer of the UE, such as the PDCP layer, instructs the RLC layer to discard a specific RLC SDU, the transmitting end of the RLC entity determines whether the RLC SDU or a segment of the RLC SDU is delivered to the lower layer for transmission:

[0095] In one case, if the RLC SDU or a segment of the RLC SDU is not delivered to the lower layer for transmission, or if the RLC SDU or any segment of the RLC SDU is not delivered to the lower layer for transmission, the transmitting end of the RLC entity may discard the RLC SDU. Preferably, the SN associated with the discarded RLC SDU may be released, and the SN may be associated with another RLC SDU.

[0096] In one case, the RLC SDU or a segment of the RLC SDU (which may be at least one of multiple segments) has been delivered to the lower layer for transmission, then the transmitting end of the RLC entity may perform one or more of the following operations:

[0097] Operation 1: Determine the value of the SN associated with the RLC SDU. This operation is optional. The UE may have determined the SN associated with the RLC SDU when determining whether the RLC SDU or a segment of the RLC SDU is delivered to the lower layer for transmission.

[0098] Operation 2: Update the value of the variable TX_Next_Ack so that the value of TX_Next_Ack skips or is not equal to the sequence number of the RLC SDU to be discarded. A possible update method may be:

[0099] First, one or more RLC SDUs that meet the conditions are determined. The conditions that need to be met here can be that the SN value associated with this or these RLC SDUs needs to be greater than or equal to the current TX_Next_Ack value and less than or equal to the current TX_Next value (TX_Next_Ack<=SN<=TX_Next);

[0100] Secondly, among these RLC SDUs that meet the conditions, the RLC SDUs that have not been confirmed to be successfully received (i.e., RLC SDUs for which ACK has not been received) are selected, and this RLC SDU or RLC SDUs are RLC SDUs that have not been instructed to be discarded. RLC SDUs that have not been confirmed to be successfully received but have been instructed to be discarded do not need to be considered / are not selected.

[0101] Then, sort these selected RLC SDUs according to the values of their associated SNs, select the one with the smallest SN value, and assign its value to TX_Next_Ack.

[0102] In this way, there is no need to re - transmit the RLC SDUs indicated to be discarded.

[0103] Another possible update method can be:

[0104] For the RLC SDUs whose SN values fall within the range of TX_Next_Ack <= SN <= TX_Next, if they have not been successfully acknowledged and have not been indicated to be discarded, then select the RLC SDU with the smallest SN value among them, and assign the value of its SN to TX_Next_Ack.

[0105] Operation 3 generates an RLC control PDU, here called a Discard PDU. Information is carried in this Discard PDU, directly or indirectly indicating the SNs associated with one or more RLC SDUs indicated to be discarded. Preferably, the values of the SNs here fall within the transmission window, that is, TX_Next_Ack <= SN < TX_Next_Ack + AM_Window_Size, where TX_Next_Ack is the value before the update operation in Operation 2. This operation can also be an optional operation, which can be performed before or after Operation 2. The generated RLC control PDU will be handed over to the lower layer for transmission and received and processed by the peer end.

[0106] A feasible indication method can be to directly include the SNs of the RLC SDUs indicated to be discarded in this Discard PDU. Preferably, if there are multiple RLC SDUs indicated to be discarded, then the SN - x of the RLC SDU with the smallest SN value among them and a range value discard - RANG can also be included in this RLC control PDU, so that SN - x + discard - RANG - 1 = SN - y, where SN - y is the SN value of the RLC SDU with the largest SN value among the multiple RLC SDUs indicated to be discarded.

[0107] In this embodiment, the transmitting end of the RLC entity can be located not only on the UE side but also on the base station side.

[0108] Embodiment 2

[0109] Corresponding to the operation of the transmitting end of the RLC entity in the first embodiment, the receiving end of the RLC entity, upon receiving the Discard PDU sent in the first embodiment, may perform the following operations:

[0110] For each SN carried in the Discard PDU, assuming that the SN value is x, then

[0111] In one case, if x>=RX_Next_Highest, the variable RX_Next_Highest is updated so that the upper limit of the receiving window can move forward. A feasible update operation may be to set the value of RX_Next_Highest to x+1.

[0112] In one case, x=RX_Highest_Status, the variable RX_Highest_Status is updated so that the positive acknowledgement generation process is not performed for the discarded RLC SDU. A feasible update operation may be:

[0113] Preferentially determining an RLC SDU that meets the conditions, where the conditions that need to be met are that the SN associated with this or these RLC SDUs needs to be greater than the current RX_Highest_Status value (SN>current RX_Highest_Status);

[0114] Then, among the RLC SDUs that meet the conditions, the RLC SDU or RLC SDUs that have not been completely received (not all bytes have been received) and are not instructed to be discarded are selected. Here, instructed to be discarded refers to the RLC SDUs indicated to be discarded in the Discard PDU. RLC SDUs that have not been completely received but have been instructed to be discarded do not need to be considered / are not selected.

[0115] Then, the SNs associated with these selected RLC SDUs are sorted according to their values, and the SN with the smallest SN value is selected and assigned to RX_Highest_Status.

[0116] Another possible update method could be:

[0117] For RLC SDUs whose SN values ​​fall within the range of SN>current RX_Highest_Status, if they have not been completely received and have not been instructed to be discarded, the RLC SDU with the smallest SN value is selected and its SN value is assigned to RX_Highest_Status.

[0118] In one case, when x=RX_Next, the value of the variable RX_Next is updated so that the lower limit of the receiving window can move forward. A feasible update operation may be:

[0119] First, determine the RLC SDUs that meet the conditions. The SN value associated with this or these RLC SDUs must be greater than the current RX_Next value.

[0120] Then, the RLC SDU or RLC SDUs that have not been completely received and have not been instructed to be discarded are selected from the RLC SDUs that meet the conditions. Here, the RLC SDU instructed to be discarded refers to the RLC SDU indicated to be discarded in the Discard PDU. For the RLC SDU that has not been completely received but is instructed to be discarded, it does not need to be considered / not selected.

[0121] Then, the SNs associated with these selected RLC SDUs are sorted according to their values, and the SN with the smallest SN value is selected and assigned to RX_Next.

[0122] Another possible update method could be:

[0123] For RLC SDUs whose SN values ​​fall within the range of SN>current RX_Next, if they have not been completely received and have not been instructed to be discarded, the RLC SDU with the smallest SN value is selected and its SN value is assigned to RX_Next.

[0124] In this way, there is no need to wait for reception of the RLC SDU instructed to be discarded.

[0125] The receiving end of the RLC entity in this embodiment may be located at the UE side or at the base station side.

[0126] In this embodiment, the discard indication of the RLC SDU received by the RLC entity receiving end may not only be included in the Discard PDU described in the first embodiment, but may also be obtained from other channels. For example, a UE including the RLC entity receiving end receives an RRC message from a base station, wherein the message indicates or includes relevant information about the RLC SDU to be discarded, such as the SN. Based on the discard indication, the UE may independently perform the operations in this embodiment to implement the discard operation.

[0127] Example 3

[0128] A new RLC SDU discarding method is introduced in the first embodiment. However, there are still existing RLC SDU discarding methods in the existing mechanism. Therefore, the method that the RLC layer should use to discard the RLC SDU upon receiving the discard indication is also a problem that needs to be solved.

[0129] One possible solution is for the RLC's upper layer, such as the PDCP layer, to indicate a discarding method when instructing the RLC to discard an RLC SDU. It is assumed here that the discarding method in Example 1 is Method 2, and the RLC SDU discarding method in the existing mechanism is Method 1. Therefore, when the PDCP layer instructs the RLC entity to discard one or more RLC SDUs, it also indicates the discarding method. The RLC entity can then discard the RLC SDUs according to the indicated discarding method.

[0130] A possible solution may also be to configure the RLC entity, directly configuring the discarding method it adopts to always be one of method one or method two, or configuring the discarding method it adopts to be method two. If the configuration is not enabled, the default discarding method is method one. Alternatively, an indirect configuration method may be used. For example, if the DRB associated with an RLC entity belongs to a specific service type, then correspondingly, the discarding method adopted by the RLC entity is always method two. If it does not belong to a specific service type, then the discarding method adopted by the RLC entity is always method one. For another example, if the PDCP layer associated with the RLC entity is configured with a specific function or feature, such as PDU group discard, then the RLC SDU discard indicated by the PDCP always adopts method two. Correspondingly, if the PDCP layer associated with the RLC entity is not configured with the specific function or feature, then the RLC SDU discard indicated by the PDCP always adopts method one. The configuration here can be achieved by receiving an RRC configuration message and determined by the configuration information provided in the RRC configuration message.

[0131] Another possible solution may be that the RLC entity adopts the second method of discarding specific RLC SDUs. The specific RLC SDU here may refer to an RLC SDU containing data of a specific service type, such as a delay-critical service, or a time-sensitive service. A feature of this type of service is that it has high requirements for data transmission delay, reliability, etc. within a certain period of time, but beyond this period of time, these data may be regarded as expired or unnecessary to transmit. For example, when the upper layer of RLC, such as the PDCP layer, delivers data, i.e., an RLC SDU, to the RLC, it may also indicate that the RLC SDU is a delay-sensitive RLC SDU, or provide corresponding information to let the RLC know that the RLC SDU carries or contains data of a delay-sensitive service, referred to as an RLC SDU belonging to a delay-sensitive service. When PDCP instructs RLC to discard an RLC SDU, the RLC entity determines whether the RLC SDU belongs to a delay-sensitive service type. If the RLC SDU is a delay-sensitive service type, it is discarded using Method 2; if it is not a delay-sensitive service type, it is discarded using Method 1. That is, the RLC entity determines which method to use for discarding based on the indicated RLC SDU type. Preferably, RLC can obtain the type of an RLC SDU through indication information from an upper layer.

[0132] This solution can be used in combination with Example 1 or alone to solve the problem of how to determine the discarding mode of RLC SDU.

[0133] Example 4

[0134] When the upper layer of the UE, such as the PDCP layer, instructs the RLC layer to discard a specific RLC SDU, the transmitting end of the RLC entity determines whether the RLC SDU or a segment of the RLC SDU is delivered to the lower layer for transmission:

[0135] In one case, if the RLC SDU does not exist or a segment of the RLC SDU is not delivered to the lower layer for transmission, or if the RLC SDU or a segment of the RLC SDU is not delivered to the lower layer for transmission, the transmitting end of the RLC entity may discard the RLC SDU. Preferably, the SN associated with the discarded RLC SDU may be released, and the SN may be associated with another RLC SDU.

[0136] In one case, the RLC SDU or the segment of the RLC SDU has been delivered to the lower layer for transmission, then the transmitting end of the RLC entity can perform the following operations: for each RLC SDU that is instructed to be discarded, generate an RLC PDU (AMDPDU), which only contains the header field values ​​of the RLC PDU (header fields) and does not contain data, that is, does not contain the RLC SDU. Among them, the header field values ​​of such an RLC PDU are set as follows

[0137] - Set the value of the Sequence Number (SN) field to the value of the SN associated with the RLC SDU that is instructed to be discarded:

[0138] - If the RLC SDU is not segmented when it is delivered to the lower layer for transmission, then the Segmentation Info (SI) field is set to "00":

[0139] -If the segment of this RLC SDU has been delivered to the lower layer for transmission, then in one way, the SI value can be set to "10", indicating that the last segment is included, and optionally, the SO (Segment Offset (SO) field) value can also be set. Preferably, the SO value is different from the previously set value, where "before" refers to the value set in one or more segments of the RLC SDU delivered to the lower layer for transmission.

[0140] -An alternative implementation is to always set the SI value to "00" regardless of whether the RLC SDU is segmented or not.

[0141] Example 5

[0142] Based on the fourth embodiment, when to send such an RLC PDU containing only a header is a problem that needs to be solved.

[0143] A possible sending timing may be: when the upper layer instructs to discard the RLC SDU, the sending end of the RLC entity generates the above RLC PDU and delivers it to the lower layer for sending. Preferably, such RLC PDU can be sent first.

[0144] Another possible transmission timing can be when, after the upper layer indicates to discard the RLC SDU, when the transmitting end of the RLC entity performs retransmission, for the RLC SDU indicated to be discarded, the above-mentioned RLC PDU containing only the header is transmitted. The moment to generate this RLC PDU can be generated when receiving the upper layer indication to discard the RLC SDU, or can be generated and transmitted when performing retransmission. The specific implementation method can be that after the transmitting end of the RLC entity determines the RLC SDU to be retransmitted, for example, determines the SN of the RLC SDU to be retransmitted, if it is determined that this RLC SDU is the RLC SDU indicated to be discarded by the upper layer, then generate the RLC PDU as described in Embodiment 4, and then hand it over to the lower layer for transmission, so as to be sent to the peer end.

[0145] Embodiment 6

[0146] Based on Embodiments 4 and 5, when the receiving end of the RLC entity receives the RLC PDU described in Embodiment 4, the following operations can be performed:

[0147] When receiving an AMD PDU from the lower layer, if the SN of this AMD PDU = x, and this AMD PDU contains only the header, or this AMD PDU does not contain data or an RLC SDU, then the receiving end of the RLC entity stores this AMD PDU in the receive buffer. Preferably, the receiving end of the RLC entity can determine whether this SN falls within the receive window, that is, if x satisfies X_Next <= x < RX_Next + AM_Window_Size, indicating that it falls within the receive window, then the receiving end of the RLC entity stores this AMD PDU in the receive buffer; if x does not satisfy X_Next <= x < RX_Next + AM_Window_Size, that is, x is less than X_Next or x is greater than or equal to RX_Next + AM_Window_Size, then the receiving end of the RLC entity stores this AMD PDU in the receive buffer.

[0148] For the AMD PDU placed in the receive buffer, if this AMD PDU contains only the header, or this AMD PDU does not contain data or an RLC SDU, then the receiving end can consider that all bytes of the RLC PDU with SN = x have been received.

[0149] And optionally, the parameter RX_Highest_Status is updated. A possible updating method may be: among all the SN values ​​​​that are greater than the current RX_Highest_Status value, select the SNs associated with the RLC SDUs that have not yet received all segments (or all bytes), and then select the SN associated with the RLC SDU that ranks first. Here, the first ranking may refer to sorting by the size of the SNs, with the SN with the smallest value ranked first. Then the updated RX_Highest_Status value is the value of the SN with the smallest value.

[0150] Optionally, the parameter RX_Next is updated. A possible updating method may be: among all the SN values ​​​​that are greater than the current RX_Next value, select the SNs associated with the RLC SDUs that have not yet received all segments (or all bytes), and then select the SN associated with the RLC SDU that ranks first. Here, the first ranking may refer to sorting by the size of the SNs, with the SN with the smallest value ranked first. Then the value of the updated RX_Highest_Status is the value of the SN with the smallest value.

[0151] Example 7

[0152] On the basis of embodiment 3, after determining the discarding mode of the RLC SDU, the UE may perform the operations in embodiments 4 to 6. Here, the solutions in embodiments 4 to 6 may be considered as one discarding mode and may be considered as mode 2.

[0153] Example 8

[0154] On the basis of the above embodiment, the receiving end of the RLC entity may further perform the following processing when constructing the STATUS PDU.

[0155] Because the STATUS PDU provides information about the SNs associated with negatively acknowledged RLC SDUs and positively acknowledged RLC SDUs, when the receiving end of the RLC entity constructs a STATUS PDU, the value of the ACK_SN contained in the STATUS PDU can be set to the value of the SN corresponding to the next RLC SDU that has not been received, where this RLC SDU is not indicated as lost and is not indicated as discarded. Discarding here may refer to the RLC SDU that is determined to be discarded based on the information provided in the received Discard PDU described in the first embodiment.

[0156] Alternatively, when the receiving end of the RLC entity constructs a STATUS PDU, for that or those RLC SDUs whose associated SN value is greater than or equal to RX_Next and less than RX_Highest_Status (RX_Next <= SN < RX_Highest_Status), select those RLC SDUs that have not been fully received and have not been indicated to be discarded, arrange them in ascending order according to the value of their SN, and process them one by one. Among the selected RLC SDU or SDUs, for an RLC SDU that has not been segmented, if it has not been received, then set the value of NACK_SN included in the STATUS PDU to the value of the SN of this RLC SDU; for a group of consecutive RLC SDUs that have not been received, then the NACK_SN and the NACK range included in the STATUS PDU, where the value of NACK_SN is the first RLC SDU in this group of consecutive unreceived RLC SDUs, that is, the RLC SDU with the smallest SN value, and the SN value of the last RLC SDU in this group of RLC SDUs is NACK_SN + NACK range - 1.

[0157] Embodiment Nine

[0158] Based on the foregoing embodiments, as the sending end of the RLC entity, when receiving a STATUS PDU, the following processing can also be performed: For the negative acknowledgment of a certain RLC SDU or RLC SDU segment indicated in the STATUS PDU, and if the RLC SDU has not been indicated to be discarded, then it can be considered that the RLC SDU or RLC SDU segment needs to be retransmitted. The discard here can refer to the RLC SDU determined to be discarded according to the indication of the upper layer.

[0159] Figure 4 is a schematic block diagram of a user equipment UE according to the present invention. As shown in Figure 4, the user equipment UE400 includes a processor 401 and a memory 402. The processor 401 can include, for example, a microprocessor, a microcontroller, an embedded processor, etc. The memory 402 can include, for example, a volatile memory (such as a random access memory RAM), a hard disk drive (HDD), a non-volatile memory (such as a flash memory), or other memories. Program instructions are stored on the memory 402. When the instructions are run by the processor 401, the above methods performed by the user equipment described in detail in the present invention can be executed.

[0160] The program running on the device according to the present invention can be a program that controls the central processing unit (CPU) to enable the computer to implement the functions of the embodiments of the present invention. The program or the information processed by the program can be temporarily stored in a volatile memory (such as a random access memory RAM), a hard disk drive (HDD), a non-volatile memory (such as a flash memory), or other memory systems.

[0161] The program for realizing each embodiment of the present invention function can be recorded on a computer-readable recording medium. Can realize corresponding function by making a computer system read the program recorded on the recording medium and executing these programs. So-called "computer system" herein can be the computer system embedded in the device, can include operating system or hardware (such as peripheral device). "Computer-readable recording medium" can be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a short-term dynamic storage program recording medium or any other recording medium that is computer-readable.

[0162] The various features or functional modules of the devices used in the above embodiments can be implemented or executed by circuits (e.g., single-chip or multi-chip integrated circuits). The circuits designed to perform the functions described in this specification may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination of the above devices. The general-purpose processor may be a microprocessor, or any existing processor, controller, microcontroller, or state machine. The above circuits may be digital circuits or analog circuits. In the event that new integrated circuit technologies have emerged to replace existing integrated circuits due to advances in semiconductor technology, one or more embodiments of the present invention may also be implemented using these new integrated circuit technologies.

[0163] Furthermore, the present invention is not limited to the above-described embodiments. Although various examples of the embodiments have been described, the present invention is not limited thereto. Fixed or non-mobile electronic devices installed indoors or outdoors can be used as terminal devices or communication devices, such as AV equipment, kitchen equipment, cleaning equipment, air conditioners, office equipment, vending machines, and other household appliances.

[0164] As described above, embodiments of the present invention have been described in detail with reference to the accompanying drawings. However, the specific structure is not limited to the above-described embodiments, and the present invention also includes any design changes that do not deviate from the main purpose of the present invention. In addition, various modifications can be made to the present invention within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. In addition, components with the same effect described in the above embodiments can be replaced with each other.

Claims

1. A method for discarding RLC SDUs performed by an RLC entity of a base station or a user equipment, the method comprising: When receiving a discard indication indicating to discard RLC SDUs from an upper layer, for each RLC SDU to be discarded indicated by the discard indication, if the RLC SDU to be discarded or a fragment of the RLC SDU to be discarded has been delivered to a lower layer, update a first status variable such that the value of the first status variable is not equal to the sequence number of the RLC SDU to be discarded. The first status variable represents the sequence number of the next RLC SDU that requires positive acknowledgement from the peer end.

2. The method according to claim 1, wherein, Updating the first status variable includes: For RLC SDUs whose sequence numbers are within a given window starting from the current value of the first status variable, and that have not been positively acknowledged and have not been indicated to be discarded, assign the minimum value among the sequence numbers of these RLC SDUs to the first status variable.

3. The method according to claim 1, further comprising: Generating a discard report and sending the discard report to the peer end, the discard report including indication information of RLC SDUs discarded by the user equipment.

4. The method according to claim 3, wherein, The discard report includes indication information of RLC SDUs whose sequence numbers are within a given window starting from the current value of the first status variable.

5. The method according to claim 3, wherein The discard report includes indication information of multiple RLC SDUs discarded by the user equipment. The indication information includes the minimum or maximum value of the sequence numbers among the multiple RLC SDUs, and a value representing the range of the sequence numbers of the discarded RLC SDUs.

6. The method according to any one of claims 1 to 5, wherein The discard indication further includes discard mode indication information for indicating whether to use a first discard mode or a second discard mode to perform the processing of discarding RLC SDUs, and the RLC entity uses the discard mode indicated by the discard mode indication information to perform the processing of discarding RLC SDUs, or The RLC entity decides whether to use a first discard mode or a second discard mode to perform the processing of discarding RLC SDUs according to the configuration regarding the discard mode for the RLC entity, or The RLC entity decides whether to use a first discard mode or a second discard mode to perform the processing of discarding RLC SDUs according to the service type and / or function corresponding to the data being sent. The second discard mode is a discard mode implemented by updating the first status variable for each RLC SDU to be discarded indicated by the discard indication, if the RLC SDU to be discarded or a fragment of the RLC SDU to be discarded has been delivered to a lower layer. The first discard mode includes: for each RLC SDU to be discarded indicated by the discard indication, if the RLC SDU to be discarded or a fragment of the RLC SDU to be discarded has been delivered to a lower layer, the RLC entity no longer performs any discard processing for the RLC SDU to be discarded.

7. A method for discarding RLC SDUs performed by an RLC entity of a base station or a user equipment, comprising: Receiving discard indication information, where the discard indication information includes indication information of RLC SDUs that have been discarded by the sender; And For each discarded RLC SDU indicated by the indication information, updating a second state variable based on the sequence number of the discarded RLC SDU, such that no positive acknowledgement generation processing is performed for the discarded RLC SDU, The second state variable includes at least one of the maximum value among the sequence number of the last RLC SDU that has been completely received by the receiver and the sequence number of the RLC SDU for which a positive acknowledgement has been generated.

8. The method according to claim 7, wherein When the second state variable is the sequence number of the last RLC SDU that has been completely received by the receiver, updating the second state variable includes: If the sequence number of the discarded RLC SDU is not less than the current second state variable, increasing the second state variable by a given value, Or, When the second state variable is the maximum value among the sequence numbers of the RLC SDUs for which positive acknowledgements have been generated, updating the second state variable includes: If the sequence number of the discarded RLC SDU is equal to the value of the current second state variable, updating the second state variable such that the value of the second state variable is not equal to the sequence number of the discarded RLC SDU.

9. The method according to claim 8, wherein Updating the second state variable such that the value of the second state variable is not equal to the sequence number of the discarded RLC SDU includes: For RLC SDUs whose sequence numbers are greater than the value of the current second state variable, and that have not been completely received and not been discarded, assigning the minimum value among the sequence numbers of these RLC SDUs to the second state variable.

10. A user equipment, comprising: A processor; And A memory storing instructions; Wherein, the instructions, when run by the processor, execute the method according to any one of claims 1 to 9.

Images