Autonomous repeat request enhancement method

Abstract

The invention provides an autonomous repeat request enhancement method. The method comprises: determining whether a value of a countdown timer is less than a threshold; and in response to the value of the countdown timer being less than the threshold, if a protocol data unit (PDU) has not been confirmed in the status report, performing retransmission for the PDU. Another method includes: determining whether a value of a countdown timer is less than a threshold; in response to the value of the countdown timer being less than the threshold, including polling in the PDU; and transmitting the PDU. Other methods include: determining whether a value of a countdown timer is greater than or equal to a threshold; and in response to the fact that the value of the countdown timer is smaller than the threshold value, if a negative acknowledgement for the PDU is received, stopping retransmission for the PDU.

Description

Technical Field

[0001] The present invention relates to an autonomous repeat request (ARQ) enhancement method. Background Art

[0002] like Figure 1 As shown, the radio link control (RLC) sublayer in the user plane protocol stack 10 of a wireless communication system provides key functions for data transmission. The RLC sublayer operates in three modes: transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM). TM is used to control protocol data units (PDUs). UM is used for live or real-time applications where low latency is critical. AM is used for reliable data transmission, such as file transfer protocol (FTP). AM can perform error correction through ARQ. Although ARQ enhances reliability, the ARQ time required for each RLC service data unit (SDU) can be as long as hundreds of milliseconds (e.g., 300ms). Emerging immersive and interactive extended reality (XR) applications require an excellent user experience, and strict latency and reliability are necessary. To meet these requirements, the ARQ mechanism needs to be enhanced and take latency factors into account. Summary of the Invention

[0003] The present disclosure provides an ARQ enhancement method that can perform timely retransmission at the RLC layer and avoid unnecessary RLC AM retransmission.

[0004] The present disclosure is directed to a method for enhancing autonomous repeat request for a radio link control (RLC) entity of a user equipment. The method includes: determining whether a countdown timer value is less than a threshold; and, in response to the countdown timer value being less than the threshold, retransmitting a protocol data unit (PDU) if the PDU has not been acknowledged in a status report.

[0005] The present disclosure is directed to a method for enhancing autonomous repeat request for a radio link control entity of a user equipment. The method comprises: determining whether a countdown timer value is less than a threshold; in response to the countdown timer value being less than the threshold, including a poll in a protocol data unit (PDU); and transmitting the PDU.

[0006] The present disclosure is directed to a method for autonomous repeat request enhancements for radio link control entity applicable to user equipment. The method includes determining whether a value of a countdown timer is greater than or equal to a threshold value; and in response to the value of the countdown timer being less than the threshold value, stopping performing retransmission for a protocol data unit (PDU) if a negative acknowledgement of the PDU is received in a status report.

[0007] In order to make the foregoing more readily understood, the following will describe in detail several embodiments, with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0008] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain principles of the present disclosure.

[0009] Figure 1 A diagram illustrating a user plane protocol stack.

[0010] Figure 2 A diagram illustrating ARQ in RLC AM according to an embodiment of the present disclosure.

[0011] Figure 3 A diagram illustrating triggering of status report according to an embodiment of the present disclosure.

[0012] Figure 4 A diagram illustrating triggering of retransmission according to an embodiment of the present disclosure.

[0013] Figure 5 A diagram illustrating delay-based retransmission according to an embodiment of the present disclosure.

[0014] Figure 6 A diagram illustrating enhanced retransmission according to an embodiment of the present disclosure.

[0015] Figure 7 A diagram illustrating delay-based retransmission according to an embodiment of the present disclosure.

[0016] Figure 8 A diagram illustrating delay-based retransmission according to an embodiment of the present disclosure.

[0017] Figure 9 A diagram illustrating delay-based polling according to an embodiment of the present disclosure.

[0018] Figure 10 A diagram illustrating enhanced polling according to an embodiment of the present disclosure.

[0019] Figure 11 A diagram illustrating enhanced polling according to an embodiment of the present disclosure.

[0020] Figure 12A diagram illustrating a timer-based status reporting according to an embodiment of the disclosure is shown.

[0021] Figure 13 A diagram illustrating an enhanced status reporting according to an embodiment of the disclosure is shown.

[0022] Figure 14 A diagram illustrating an enhanced status reporting according to an embodiment of the disclosure is shown.

[0023] Figure 15 A diagram illustrating a delay-based RLC AM discard according to an embodiment of the disclosure is shown.

[0024] Figure 16 A flowchart of a method of ARQ enhancement according to an embodiment of the disclosure is shown.

[0025] Figure 17 A flowchart of a method of ARQ enhancement according to an embodiment of the disclosure is shown.

[0026] Figure 18 A flowchart of a method of ARQ enhancement according to an embodiment of the disclosure is shown.

[0027] Figure 19 A diagram illustrating a communication device according to an embodiment of the disclosure is shown. DETAILED DESCRIPTION

[0028] Reference will now be made in detail embodiments of the application, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

[0029] Figure 2 A diagram illustrating ARQ in RLC AM according to an embodiment of the disclosure is shown. For uplink (UL) transmission, a user equipment (UE) 100 can transmit a poll to a network 200 (e.g., a next generation radio access network (NG-RAN)). A poll can be triggered if the number of PDUs transmitted since the last poll bit transmission (i.e., counter PDU_WITHOUT_POLL) is greater than or equal to a threshold pollPDU, or the number of bytes transmitted since the last poll bit transmission (i.e., counter BYTE_WITHOUT_POLL) is greater than or equal to a threshold pollByte. A poll can also be triggered if a timer t-PollRetransmit expires. The network 200 can perform a status report for the UE 100 upon receiving the poll. If the status report indicates that retransmission is needed, the UE 100 can retransmit data to the network 200.

[0030] When the lower layer informs of transmission opportunities, for each AM data (AMD) PDU that causes the AMD PDU to contain an RLC SDU or RLC SDU segment that has not been previously transmitted (e.g., contains a segment that has not been previously transmitted byte segment) for transmission submission, the transmitting side (e.g., UE 100) of the AM RLC entity shall: increment PDU_WITHOUT_POLL by one; and increment BYTE_WITHOUT_POLL by each new byte of the data field elements of the data field of the AMD PDU. If PDU_WITHOUT_POLL ≥ pollPDU or BYTE_WITHOUT_POLL ≥ pollByte, the transmitting side can include a poll in the AMD PDU. The counter PDU_WITHOUT_POLL is initially set to 0, which counts the number of AMD PDUs sent since the last poll bit transmission. The counter BYTE_WITHOUT_POLL is initially set to 0, which counts the number of data bytes sent since the last poll bit transmission.

[0031] To include a poll in an AMD PDU, the transmitting side of the AM RLC entity shall: set the P- field (i.e., poll field) of the AMD PDU to “1”; set PDU_WITHOUT_POLL to 0; and set BYTE_WITHOUT_POLL to 0. When submitting the AMD PDU containing a poll to the lower layer, the transmitting side of the AM RLC entity shall: if t-PollRetransmit is not running: start t-PollRetransmit; else restart t-PollRetransmit. Upon expiry of t-PollRetransmit, the transmitting side of the AM RLC entity shall: if both the transmission buffer and the retransmission buffer are empty (contain no transmitted RLC SDU or RLC SDU segment pending acknowledgement) or if no new RLC SDU or RLC SDU segment can be transmitted (e.g., due to window stalling), include a poll in an AMD PDU as described in section 5.3.3.2 of TS 38.322.

[0032] Figure 3A diagram illustrating triggering of status reporting according to one embodiment of the disclosure is shown. The initialization of triggering of status reporting can include: a poll from the peer AM RLC entity; or expiry of t-PollRetransmit. When generating a status PDU, the AM RLC entity shall: for RLC SDUs with serial numbers (SNs) (parameter RX_Next < SN < parameter RX_Highest_Status) that have not been completely received, in ascending SN order of the RLC SDUs and ascending byte segment order within the RLC SDUs, starting from SN = RX_Next, until the generated status PDU still fits into the total size of RLC PDUs indicated by lower layers: for RLC SDUs for which no byte segment has been received, include in the status PDU a parameter NACK_SN set to the SN of the RLC SDU. When generating a status PDU, the AM RLC entity shall: set the parameter ACK_SN to the SN of the next RLC SDU that has not been indicated as missing in the generated status PDU.

[0033] Figure 4 A diagram illustrating triggering of retransmission according to one embodiment of the disclosure is shown. When receiving a negative acknowledgement (NACK) of a RLC SDU or RLC SDU segment from the peer AM RLC entity through a status PDU, the transmitting side of the AM RLC entity shall: consider retransmitting the RLC SDU or RLC SDU segment corresponding to the received NACK if the SN of the corresponding RLC SDU falls within the parameter range TX_Next_Ack < SN < the highest SN of the AMD PDUs submitted to lower layers. When considering retransmitting the RLC SDU or RLC SDU segment, the transmitting side of the AM RLC entity shall: if it is the first time to consider retransmitting the RLC SDU or RLC SDU segment, set the counter RETX_COUNT associated with the RLC SDU to zero; otherwise, if the RLC SDU or RLC SDU segment considered for retransmission has not been waiting for retransmission, increase the RETX_COUNT; if RETX_COUNT = parameter maxRetxThreshold, indicate to the upper layer that the maximum number of retransmissions has been reached. The RETX_COUNT counts the number of retransmissions of the RLC SDU or RLC SDU segment as described in subclause 5.3.2 of TS 38.322. One RETX_COUNT counter is maintained per RLC SDU.

[0034] When retransmitting a RLC SDU or a RLC SDU segment, the transmitting side of the AM RLC entity shall: segment the RLC SDU or RLC SDU segment, if necessary; form a new AMD PDU that will fit the total size of AMD PDU indicated by lower layers at a particular transmission opportunity; and submit the new AMD PDU to lower layers. When forming a new AMD PDU, the transmitting side of the AM RLC entity shall: only map the original RLC SDU or RLC SDU segment to the data field of the new AMD PDU; modify the header of the new AMD PDU according to the description in subclause 6.2.2.4 of TS 38.322; and set the P field according to subclause 5.3.3 of TS 38.322.

[0035] SDU discard procedure: When instructed by upper layers (e.g., packet data convergence protocol (PDCP)) to discard a particular RLC SDU, the transmitting side of the AM RLC entity or the transmitting UM RLC entity shall discard the indicated RLC SDU if neither the RLC SDU nor a RLC SDU segment is submitted to lower layers. The transmitting side of the AM RLC entity shall not introduce an RLC SN gap when discarding a RLC SDU.

[0036] Figure 5 A diagram illustrating delay-based retransmission is shown according to one embodiment of the disclosure. The transmitting side (e.g., UE 100) can perform autonomous retransmission for urgent data according to a new triggering manner. The RRC layer can control the retransmission procedure by transmitting a radio resource control (RRC) reconfiguration message from the network 200 to the UE 100, where the RRC reconfiguration message can include a parameter retransmissionTimeThreshold, where retransmissionTimeThreshold is a threshold of the delay time for retransmitting an AMD PDU. The transmitting side can perform enhanced retransmission according to retransmissionTimeThreshold.

[0037] Figure 6A diagram 600 illustrating enhanced retransmission according to one embodiment of the disclosure is shown. The RLC entity of the transmitting end can determine whether the value of the countdown timer is less than the threshold. If the value of the countdown timer is less than the threshold and the PDU (or the transmission data corresponding to the countdown timer) has not been acknowledged in the status report, the RLC entity can perform retransmission for the PDU (e.g., AMD PDU) corresponding to the countdown timer. The countdown timer can be started or reset when the PDU is obtained by the PDCP entity, which is an entity operating as an upper layer of the RLC entity. For example, when the PDCP entity receives PDU 1-1, the countdown timer PDCPdiscardTimer corresponding to PDU 1-1 can be started or reset. Assume that the PDCP PDU 1-1 is segmented into two AMD PDUs 1-1-1 and 1-1-2, the initial value of the PDCP discardTimer associated with PDU 1-1 is 30 ms, and the retransmissionTimeThreshold is 15 ms. After the PDCP discardTimer is started for 16 ms, the RLC layer can determine that the remaining value of the PDCP discardTimer is 30-16 = 14 ms. Since 14 ms is less than the retransmissionTimeThreshold = 15 ms, the RLC layer can perform retransmission for PDU 1-1-1 and PDU 1-1-2.

[0038] On the other hand, the countdown timer PDCPdiscardTimer corresponding to PDU 1-2 can be started or reset when the PDCP entity receives PDU 1-2. If the transmitting end receives an acknowledgement (ACK) of PDU 1-2 before the remaining value of the PDCP discardTimer falls below the retransmissionTimeThreshold, the RLC layer can not perform retransmission for PDU 1-2.

[0039] In one embodiment, when a negative acknowledgement of a RLC SDU or a RLC SDU segment is received by the transmitting side of an AM RLC entity from its peer AM RLC entity through a status PDU, or when the remaining value of a timer (e.g., PDCP discardTimer) associated with an AMD PDU that has not been acknowledged in the status report falls below retransmittionTimeThreshold, the transmitting side of the AM RLC entity shall consider the RLC SDU or RLC SDU segment for which the negative acknowledgement is received, or the AMD PDU associated with the timer (e.g., PDCP discardTimer) whose remaining time falls below retransmissionTimeThreshold for retransmission if the SN of the corresponding RLC PDU is within the range TX_Next_Ack < SN < the highest SN of the AMD PDUs that have been submitted to lower layers.

[0040] In one embodiment, the autonomous retransmission by the transmitting side can be triggered based on the PDCP indication of the corresponding AMD PDU. Specifically, assume that a PDU is submitted from a PDCP entity to an RLC entity. The RLC entity can receive the indication from the PDCP entity and can perform retransmission for the PDU according to the indication.

[0041] In one embodiment, when a negative acknowledgement of a RLC SDU or a RLC SDU segment is received by the transmitting side of an AM RLC entity from its peer AM RLC entity through a status PDU, or when the upper layer (e.g., PDCP) indicates retransmission of a particular RLC SDU or a particular RLC SDU segment that has not been acknowledged in the status report, the transmitting side of the AM RLC entity shall consider the RLC SDU or RLC SDU segment for which the negative acknowledgement is received, or the particular RLC SDU or particular RLC SDU segment that the upper layer indicates for retransmission if the SN of the corresponding RLC SDU is within the range TX_Next_Ack < SN < the highest SN of the AMD PDUs that have been submitted to lower layers.

[0042] In one embodiment, when the discardTimer or discarTimerForLowImportance of a PDCP SDU falls below retransmissionTimeThreshold, the transmitting PDCP entity shall instruct the lower layer to retransmit the corresponding PDCP PDU if the PDCP PDU has been submitted to the lower layer.

[0043] In one embodiment, the RLC entity at the transmitting end can identify the importance of a PDU according to the importance of the RLC layer (e.g., PDU set importance (PSI) setting) or the RLC entity can receive an importance indication from the PDCP layer. If the importance of the PDU is high, the RLC entity can perform PSI-based retransmission for the PDU. It is noted that the PSI identification of a PDU set and the determination of a low / high importance PDU set can be left to UE implementation.

[0044] In one embodiment, if a PDCP SDU is identified as a high importance PDCP SDU and if the corresponding PDCP data PDU has been submitted to lower layers, the importance identification (or importance indication) of the PDCP data PDU is provided to the lower layers.

[0045] In one embodiment, the PSI identification of a PDU set and the determination of a low / high importance PDU set at the RLC layer are left to UE implementation.

[0046] Figure 7 A diagram 700 of delay-based retransmission is illustrated according to one embodiment of the disclosure. Delay-based ARQ retransmission can trigger a delay status reporting (DSR) in the MAC entity. The RLC entity can trigger the MAC entity to transmit the DSR. The DSR can be transmitted from the transmitting end (e.g., UE) to the receiving end (e.g., NG-RAN) through a media access control (MAC) control element (CE). In one embodiment, if remainingTimeThreshold-r18 < retransmissionTimeThreshold (scenario: 10 ms < 15 ms), the DSR can be triggered by delay-based retransmission. If remainingTimeThreshold-r18 ≥ retransmissionTimeThreshold (scenario: 10 ms = 10 ms), the DSR can be triggered according to subclause 5.4.9 in TS 38.321.

[0047] In one embodiment, if a logical channel group (LCG) is configured for delay status reporting, the MAC entity shall, for each logical channel within the LCG: 1> if the minimum remaining value of the running PDCP discard timer among all PDCP SDUs buffered for the logical channel that have not been transmitted in any MAC PDU and have not been reported as data volume in a DSR MAC CE falls below remainingTimeThreshold for the LCG, or if delay-based retransmission is indicated by the associated RLC entity for at least one logical channel (LCH) of the LCG; and 1> if the logical channel has no pending DSR: 2> trigger a DSR for the logical channel.

[0048] Figure 8 A diagram 800 of delay-based retransmission is illustrated according to one embodiment of the present disclosure. The transmitting end can determine whether there is latency critical data in the LCH buffer, where the latency critical data can be indicated by the upper layer, and the latency critical data can use a configured higher priority for transmission of the LCH during logical channel prioritization (LCP) operation. For example, the RLC entity can transmit an indication to the LCH corresponding to the LCH buffer.

[0049] In one embodiment, the MAC entity shall, when performing a new transmission: 1> allocate resources to logical channels as follows: 2> if a logical channel is indicated that its logical channel buffer has latency critical data (e.g., from the upper layer (i.e., RLC)), this logical channel is allocated resources first or with a configured higher logical channel priority (if there are multiple logical channels with latency critical data, in decreasing order of priority).

[0050] Figure 9A diagram illustrating delay-based polling is shown according to one embodiment of the present disclosure. In addition to data-based triggers, a transmitting end (e.g., UE 100) can perform delay-based polling triggers according to a new triggering manner. The RRC layer can control the polling procedure by transmitting an RRC reconfiguration message from the network 200 to the UE 100, where the RRC reconfiguration message can include a parameter pollDelay. The parameter pollDelay is a threshold of the delay time for including a poll in an AMD PDU. The variable DELAY_WITHOUT_POLL is a counter (or countdown timer) that is initially set to a configured or specified value, and DELAY_WITHOUT_POLL can be configured by the RRC reconfiguration message. DELAY_WITHOUT_POLL counts the elapsed time since the last poll bit transmission. That is, the RLC entity of the transmitting end can reset DELAY_WITHOUT_POLL when a previous poll is transmitted from the transmitting end to the receiving end (e.g., network 200). The RLC entity can determine whether the value of DELAY_WITHOUT_POLL is less than the threshold pollDelay. If DELAY_WITHOUT_POLL is less than pollDelay, the RLC entity can include a poll in a PDU and transmit the PDU to the receiving end.

[0051] Figure 10 A diagram illustrating enhanced polling is shown 1000 according to one embodiment of the present disclosure. Assume that the initial value of DELAY_WITHOUT_POLL is 30 ms and pollDelay is 15 ms. The RLC layer can reset DELAY_WITHOUT_POLL in response to transmitting a poll. When the lower layer informs of a transmission opportunity (e.g., of AMD PDU 1-2), if DELAY_WITHOUT_POLL (e.g., 30-16 = 14 ms) < pollDelay (e.g., 15 ms), the RLC layer can include a poll in AMD PDU 1-2, and can transmit AMD PDU 1-2 to the receiving end.

[0052] In one embodiment, to include a poll in an AMD PDU, the transmitting end of the AM RLC entity should: set the P field of the AMD PDU to “1”; set PDU_WITHOUT_POLL to 0; set BYTE_WITHOUT_POLL to 0; and set DELAY_WITHOUT_POLL to DELAY_WITHOUT_POLL (e.g., a preset value such as 30 ms).

[0053] In one embodiment, upon a lower layer informing of a transmission opportunity, for each submitted transmission, the transmitting side of the AM RLC entity shall: decrease DELAY_WITHOUT_POLL by the time elapsed since the last decrease of DELAY_WITHOUT_POLL; increase PDU_WITHOUT_POLL by one; increase BYTE_WITHOUT_POLL with each new byte of the data field element, such that BYTE_WITHOUT_POLL corresponds to the data field of the AMD PDU; or include a poll in the AMD PDU if DELAY_WITHOUT_POLL < pollDelay (e.g., if the time remaining falls below a threshold), if PDU_WITHOUT_POLL >= pollPDU, or if BYTE_WITHOUT_POLL >= pollByte.

[0054] In one embodiment, autonomous polling of emergency data can be triggered. Figure 11 A diagram 1100 illustrating enhanced polling according to one embodiment of the disclosure is shown. The RRC layer can control the polling procedure by transmitting an RRC reconfiguration message from the network 200 to the UE 100, where the RRC reconfiguration message can include a parameter pollTimeThreshold, and pollTimeThreshold is a threshold of the delay time of polling. A timer can be started or reset when a PDU is acquired by a PDCP entity, where the PDCP entity is an entity operating as an upper layer of the RLC entity. If the countdown timer PDCP discardTimer is less than pollTimeThreshold, the RLC entity can include a poll in the PDU and can transmit the PDU to the receiving side.

[0055] For example, the countdown timer PDCP discardTimer corresponding to PDU 1-1 can be started or reset when PDU 1-1 is received at the PDCP layer. Assume that the initial value of the PDCP discardTimer associated with PDU 1-1 is 30 ms, and pollTimeThreshold is 20 ms. Upon a lower layer informing of a transmission opportunity (e.g., the transmission opportunity of AMD PDU 1-2), if the remaining value of the PDCP discardTimer associated with AMD PDU 1-1-1 (e.g., 30-11 = 19 ms) < pollTimeThreshold (e.g., 20 ms), the RLC layer can include a poll in AMD PDU 1-2, and can transmit AMD PDU 1-2 to the receiving side.

[0056] In one embodiment, upon a lower layer informing of a transmission opportunity, for each submitted transmission, the transmitting side of the AM RLC entity shall include a poll in the AMD PDU if the remaining value of at least one timer (e.g., PDCP discardTimer) associated with the AMD PDU for which no ACK / NACK status has been received falls below pollingTimeThreshold, if PDU_WITHOUT_POLL≥ pollPUD, or if BYTE_WITHOUT_POLL≥ pollByte.

[0057] In one embodiment, the poll by the transmitting side can be triggered based on a PDCP indication of the corresponding AMD PDU. Specifically, assume a PDU is submitted from the PDCP entity to the RLC entity. The RLC entity can receive the indication from the PDCP entity and can include a poll in the PDU and transmit the PDU to the receiving side.

[0058] In one embodiment, the RLC entity of the transmitting side can determine the importance of a PDU according to the importance indication (e.g., PSI) of the RLC layer, or the RLC entity can receive the importance indication from the PDCP layer. If the importance of the PDU is high, the RLC entity can perform a PSI-based poll on the PDU. That is, the RLC entity can include a poll in the PDU and transmit the PDU to the receiving side. Note that the PSI identification of the PDU set and the determination of the low / high importance PDU set can be left to UE implementation.

[0059] Figure 12 A diagram illustrating timer-based status reporting according to one embodiment of the present disclosure is shown. The receiving side (e.g., network 200) can perform timer-based status reporting after each preset period, where the preset period can be set based on timer T-ReassemblyForStatusReport := ENUMERATED {ms0, ms5, ms10, ms15, ms20, ms25, ms30, ms35, ms40, ms45, ms50, ms55, ms60, ms65, ms70, ms75, ms80, ms85, ms90, ms95, ms100, ms110, ms120, ms130, ms140, ms150, ms160, ms170, ms180, ms190, ms200, sparel}.

[0060] Figure 13A diagram 1300 illustrating enhanced status reporting according to one embodiment of the disclosure is shown. When the RLC entity of the receiving end receives the first segment of an SDU, which can contain multiple pending segments, T-ReassemblyForStatusReport can be started. If T-ReassemblyForStatusReport does not expire, T-ReassemblyForStatusReport can be stopped when the receiving end completely receives the SDU. However, if T-ReassemblyForStatusReport expires, the RLC entity of the receiving end can trigger a status report.

[0061] Assuming T-ReassemblyForStatusReport is set to "20 ms", and segments (e.g., AMD PDU 1-1-1, AMD PDU 1-1-2 of PDCP PDU 1-1) are submitted from the PDCP entity of the transmitting end to the RLC entity. The RLC entity of the receiving end can start T-ReassemblyForStatusReport in response to receiving AMD PDU 1-1-1. After 20 ms (i.e., when T-ReassemblyForStatusReport expires), if one or more PDU segments corresponding to PDCP PDU 1-1 are pending and have not been received by the receiving end, the RLC entity can transmit a status report of the pending PDU segments to the transmitting end (e.g., UE 100).

[0062] In one embodiment, triggers to start a status report include: a poll from the peer AM RLC entity; and detection of a reception failure of an AMD PDU: the receiving end of the AM RLC entity should trigger a status report upon expiry of the timer t-Reassembly or ReassemblyForStatusReport.

[0063] In one embodiment, the RRC layer can control the ARQ procedure by reconfiguring the following parameters: statusReportInterval: the interval threshold for RLC AM status reporting, where statusReportInterval is reset to the configured or specified value when the receiving end transmits a status PDU. In one embodiment, statusReportInterval := ENUMERATED {ms5, ms10, ms15, ms20, ms25, ms30, ms35, ms40, ms45, ms50, ms55, ms60, sparel}. statusReportInterval can be started when a status PDU is transmitted. statusReportInterval can be stopped when the next status PDU is transmitted. A status report can be triggered when statusReportInterval expires.

[0064] Figure 14 A diagram 1400 illustrating enhanced status reporting is shown, in accordance with one embodiment of the present disclosure. Assume that statusReportInterval is set to "20ms". 20ms after the first status PDU is transmitted (i.e., when statusReportInterval expires), the receiving end's RLC entity can transmit a second status PDU to the transmitting end.

[0065] In one embodiment, the triggers to start a status report include: a poll from its peer AM RLC entity; detection of a reception failure of an AMD PDU; the receiving end of the AM RLC entity shall trigger a status report upon expiry of timer t-Reassembly; and the receiving end of the AM RLC entity shall trigger a status report upon expiry of statusReportInterval.

[0066] In one embodiment, with respect to UL transmission, and hybrid automatic repeat request (HARQ) behavior of a new radio (NR) UE, a gNB can send a retransmission request. If the gNB does not send a retransmission request (i.e., a downlink control information (DCI) 0_0 / 0_1 with no new data indicator (NDI) toggling) within a certain time (for configured grant (CG)), the UE assumes that the physical uplink shared channel (PUSCH) has been successfully received and decoded by the gNB. For configured grant, for the initial transmission of a transport block by the UE in a PUSCH configured by ConfiguredGrantConfig, if the UE receives CG- downlink feedback information (DFI) that provides HARQ-ACK information for the transport block, if the HARQ-ACK information value is ACK, the UE assumes that the transport block has been correctly decoded; otherwise, the UE assumes that the transport block has not been correctly decoded. With respect to maximum retransmission, the total transmission time of a MAC transport block (TB) is 4 (i.e., 1 + 3, then discarded).

[0067] With respect to a UE as a transmitting end (i.e., UL transmission), a method is needed for the MAC entity of the UE to determine whether there is a HARQ residual error in a HARQ process. A new indicator can indicate that the gNB wants to give up the HARQ retransmission of the HARQ process. The new indicator can be carried in a newly designed DL signal in the physical (PHY) layer, can be carried in a DCI used to schedule a new transmission for the HARQ process, or can be carried in an existing DL signal in the PHY (e.g., CG-DFI). Upon receiving the new indicator, the MAC entity of the UE should consider that there is a HARQ residual error in the HARQ process, and the MAC entity can inform the corresponding RLC entity of the UE to speed up the ARQ retransmission.

[0068] In one embodiment, a retransmission indication from HARQ to ARQ is designed if the number of retransmission requests received from gNB exceeds the maximum number of retransmission for HARQ operation. When a negative acknowledgement of a RLC SDU or RLC SDU segment is received through a status PDU from its peer AM RLC entity, or when a retransmission indication of a RLC SDU or RLC SDU segment is received from lower layer, the transmitting side of an AM RLC entity shall: consider the retransmission of the RLC SDU or RLC SDU segment for which a negative acknowledgement is received or from which a retransmission indication is received from lower layer, if the SN of the corresponding RLC SDU is within the range TX_Next_ACK ≤ SN ≤ the highest SN of the AMD PDU(s) submitted to lower layer. It is noted that the retransmission indication of a RLC SDU or RLC SDU segment from lower layer can be left to UE implementation (e.g. the number of HARQ retransmission of a transport block containing a RLC SDU or RLC SDU segment has reached the maximum number of retransmission (e.g. 4)).

[0069] In one embodiment, the above-mentioned retransmission indication is only applied to AMD PDU with high importance. The RLC entity of the transmitting side can identify the importance of a PDU according to the importance identification (e.g. PSI) of RLC layer, or the RLC entity can receive the importance indication from PDCP layer. If a PDCP PDU is identified as a high importance PDCP SDU, and if the corresponding PDCP data PDU has been submitted to lower layer, the importance indication of the PDCP data PDU is provided to lower layer. It is noted that the PSI identification of a PDU set and the determination of low / high importance PDU set at PDCP layer or RLC layer can be left to UE implementation.

[0070] Regarding the UE as a receiving side (i.e. DL transmission), a HARQ to ARQ indication is designed to trigger a status report if the number of HARQ NACKs of a transport block exceeds the maximum retransmission threshold.

[0071] In one embodiment, the triggers to initiate a status report include: a poll from its peer AM RLC entity; a detection of a failure of AMD PDU reception: the receiving side of an AM RLC entity shall trigger a status report upon expiry of t-Reassembly; or a HARQ indication. It is noted that the HARQ indication from lower layer can be left to UE implementation (e.g. the number of HARQ NACKs of a code block group (CBG) containing a RLC SDU or RLC SDU segment has reached the maximum number of HARQ NACKs (e.g. 4)).

[0072] In one embodiment, the above-mentioned HARQ indication is only applied to AMD PDUs with high importance. The transmitting side RLC entity can identify the importance of a PDU according to the importance indication (e.g., PSI) of the RLC layer, or the RLC entity can receive the importance indication from the PDCP layer. If a PDCP PDU is identified as a high importance PDCP SDU, and if the corresponding PDCP data PDU has been submitted to lower layers, the importance indication (e.g., HARQ indication) of the PDCP data PDU is provided to the lower layers. It is noted that the PSI identification of a PDU set and the determination of low / high importance PDU set at the PDCP layer or the RLC layer is left to UE implementation.

[0073] When a specific RLC SDU is indicated to be discarded from the upper layer (e.g., PDCP), if neither the RLC SDU nor its segments have been submitted to lower layers, the transmitting side AM RLC entity or the transmitting UM RLC entity shall discard the indicated RLC SDU. If the data in the transmission window is too old (i.e., the remaining value of the PDCP discardTimer is below a threshold), the AM RLC entity can refuse to consider the data for retransmission. The AM RLC entity can receive the indication from the PDCP entity, and if a negative acknowledgement of the PDU is received in a status report, stop performing retransmission for the PDU according to the indication.

[0074] Figure 15 A diagram illustrating delay-based RLC AM discard is shown according to one embodiment of the present disclosure. The RLC entity of the transmitting side (e.g., UE 100) can perform delay-based RLC AM discard. Specifically, the transmitting side can determine whether the value of the countdown timer (e.g., PDCP discardTimer) is greater than or equal to a threshold (e.g., earlyDiscardTimerForAMRLC: threshold of delay time for discarding AMD PDUs in the retransmission buffer). If the value of the countdown timer is less than the threshold, the RLC entity can discard the PDU in the retransmission buffer. If the value of the countdown timer is greater than or equal to the threshold and the RLC entity has received a NACK for the PDU (or the PDU has not been acknowledged by the RLC entity), the RLC entity can perform retransmission for the PDU in the retransmission buffer.

[0075] In one embodiment, when receiving a negative acknowledgement of a RLC SDU or RLC SDU segment from its peer AM RLC entity through a status PDU, the transmitting side of the AM RLC entity shall: if the SN of the corresponding RLC SDU falls within the range TX_Next_ACK < SN < the highest SN of the AMD PDU(s) already submitted to lower layers, and the remaining value of the timer (e.g., PDCP discardTimer) associated with the AMD PDU(s) is greater than or equal to earlyDiscardTimerForAMRLC, consider the RLC SDU or RLC SDU segment for which the negative acknowledgement is received for retransmission.

[0076] For example, assume that the discardTimer (i.e., the preset value of the counter discardTimer) in the PDCP entity is configured as 50 ms, and the earlyDiscardTimerForAMRLC in the AM RLC entity is configured as 15 ms. When the remaining value of the PDCP discardTimer associated with the AMD PDU(s) is higher than the earlyDiscardTimerForAMRLC, it means that the AMD PDU(s) is still fresh and eligible to be considered for retransmission. The RLC entity can perform retransmission for the AMD PDU(s).

[0077] In one embodiment, the discarding of the PDU(s) in the retransmission buffer of the transmitting side can be triggered based on the PDCP indication of the corresponding AMD PDU(s). Specifically, assume that a PDU is submitted from the PDCP entity to the RLC entity. The RLC entity can receive the indication from the PDCP entity, and can discard the PDU(s) in the retransmission buffer or can stop performing retransmission for the PDU(s) according to the indication.

[0078] In one embodiment, when the discardTimer or discarTimerForLowImportance of a PDCP SDU is lower than a threshold (e.g., earlyDiscardTimerForAMRLC), the transmitting PDCP entity shall indicate the lower layer to discard the corresponding PDCP PDU(s) in the retransmission buffer, or stop performing retransmission for the PDCP PDU(s) if the PDCP PDU(s) has been submitted to the lower layer (or if a NACK for the PDU(s) is received in a status report).

[0079] In one embodiment, the discard of the AMD PDU can be triggered based on a parameter psd-SetAMRLC included in an RRC reconfiguration message transmitted from a receiving end (e.g., network 200) to a transmitting end (e.g., UE 100). If psd-SetAMRLC is set (e.g., set to true), the transmitting end can perform PDU set based discard for the AM RLC entity. If psd-SetAMRLC is not set or set to false, the transmitting end can not perform PDU set based discard for the AM RLC entity.

[0080] In particular, assume that psd-SetAMRLC is set to true, and a PDU corresponding to a particular PDU set is submitted from a PDCP entity to an RLC entity. The RLC entity can receive an indication from the PDCP entity. The RLC entity can discard one or more PDUs (e.g., one or more PDUs corresponding to the same particular PDU set) in the retransmission buffer in response to a remaining value of a PDCP discardTimer associated with the AMD PDU being less than an earlyDiscardTimerForAMRLC. Otherwise, if the remaining value of the PDCP discardTimer is less than the earlyDiscardTimerForAMRLC, the RLC entity can only discard submitted PDUs in the retransmission buffer.

[0081] In one embodiment, the RLC entity of the transmitting end can determine the importance of a PDU according to a significance indication (e.g., PSI) of the RLC layer, or the RLC entity can receive an importance indication from the PDCP layer. If the PDU is less important, the RLC entity can perform PSI based discard for the PDU. That is, the RLC entity can discard the PDU in the retransmission buffer in response to a remaining value of a PDCP discardTimer associated with the AMD PDU being less than an earlyDiscardTimerForAMRLC and the PDU being less important. Otherwise, the RLC entity can perform retransmission for the PDU in the retransmission buffer in response to the remaining value of the PDCP discardTimer associated with the AMD PDU being greater than or equal to the earlyDiscardTimerForAMRLC or the PDU being more important.

[0082] In one embodiment, when receiving a negative acknowledgement of an RLC SDU or RLC SDU segment from its peer AM RLC entity through a status PDU, the transmitting side of the AM RLC entity shall: if the SN of the corresponding RLC SDU falls within the range TX_Next_Ack < SN < the highest SN of an AMD PDU submitted to lower layers, and the remaining value of the timer (e.g., PDCP discardTimer) associated with the AMD PDU is greater than or equal to earlyDiscardTimerForAMRLC: consider retransmitting the RLC SDU or RLC SDU segment for which the negative acknowledgement is received; otherwise, if pdu-SetAMRLC is configured: consider not retransmitting all RLC SDUs or RLC SDU segments in the PDU set to which the RLC SDU or RLC SDU segment belongs.

[0083] Figure 16 A flowchart of a method of ARQ enhancement is illustrated, according to one embodiment of the present disclosure, wherein the method can be implemented by an RLC entity of a communication device (e.g., UE 100). At step S161, it is determined whether the value of the countdown timer is less than a threshold. At step S162, in response to the value of the countdown timer being less than the threshold, retransmission is performed for a protocol data unit (PDU) if the PDU has not been acknowledged in a status report.

[0084] Figure 17 A flowchart of a method of ARQ enhancement is illustrated, according to one embodiment of the present disclosure, wherein the method can be implemented by an RLC entity of a communication device (e.g., UE 100). At step S171, it is determined whether the value of the countdown timer is less than a threshold. At step S172, in response to the value of the countdown timer being less than the threshold, a poll is included in a protocol data unit (PDU). At step S173, the protocol data unit is transmitted.

[0085] Figure 18 A flowchart of a method of ARQ enhancement is illustrated, according to one embodiment of the present disclosure, wherein the method can be implemented by an RLC entity of a communication device (e.g., UE 100). At step S181, it is determined whether the value of the countdown timer is greater than or equal to a threshold. At step S182, in response to the value of the countdown timer being less than the threshold, retransmission is stopped for a protocol data unit (PDU) if a negative acknowledgement of the PDU is received in a status report.

[0086] Figure 19 A schematic diagram of a communication device is illustrated, according to one embodiment of the present disclosure. The communication device 300 can include a processor 310, a storage medium 320, and a transceiver 330. The processor 310 is coupled to the storage medium 320 and the transceiver 330, and is configured to implement at least Figures 1-18The method described above and example embodiments and alternatives thereof. In one embodiment, the communication device can be implemented by the UE 100 or the network 200.

[0087] The processor 310 can be implemented using a programmable unit, such as a microprocessor, a microcontroller, a digital signal processor (DSP) chip, a field programmable gate array (FPGA), or the like. The functions of the processor 310 can also be implemented by a separate electronic device or IC. It should be noted that the functions of the processor 310 can be implemented by hardware or software.

[0088] The storage medium 320 can be, for example, any type of fixed or removable random access memory (RAM), read-only memory (ROM), flash memory, hard disk drive (HDD), solid state drive (SSD), or the like, or a combination thereof, configured to record a plurality of modules or various applications executable by the processor 310.

[0089] The transceiver 330 can be configured to transmit and receive signals in a radio frequency, respectively. The transceiver 330 can also perform operations such as low noise amplification, impedance matching, frequency mixing, up or down frequency conversion, filtering, amplification, and the like. The transceiver 330 can include one or more digital-to-analog (D / A) converters or analog-to-digital (A / D) converters configured to convert from an analog signal format to a digital signal format during uplink signal processing, and from a digital signal format to an analog signal format during downlink signal processing. The transceiver 330 can include an antenna array, which can include one or more antennas to transmit and receive omnidirectional antenna beams or directional antenna beams.

[0090] Based on the above, the present disclosure can enhance the procedures of ARQ (e.g., retransmission, polling, or status reporting) so that these procedures can be performed according to delay-based or timer-based events. On the other hand, the present disclosure can avoid unnecessary RLC AM retransmission of outdated PDUs.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacements to some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for autonomous repeat request enhancement, applicable to a radio link control entity of a user equipment, characterized in that: include: Determine whether the countdown timer value is less than the threshold; as well as In response to the value of the countdown timer being less than the threshold, retransmission is performed for the protocol data unit if the protocol data unit has not been acknowledged in a status report.

2. The method of claim 1 , wherein performing the retransmission for the protocol data unit comprises: receiving an instruction from a packet data convergence protocol entity; as well as The retransmission is performed according to the instruction.

3. The method of claim 1 , wherein performing the retransmission for the protocol data unit comprises: Determining the importance of the protocol data unit based on an identification from the radio link control layer or an identification from the packet data convergence protocol layer; as well as In response to the importance of the protocol data unit being high, the retransmission is performed.

4. The method according to claim 1, further comprising: Determine whether there is delay-critical data in the logical channel buffer; as well as In response to the presence of the delay-critical data in the logical channel buffer, an indication is transmitted to a logical channel corresponding to the logical channel buffer, wherein the logical channel obtains communication resources according to the indication.

5. The method of claim 1, wherein the countdown timer corresponds to transmitted data, wherein the transmitted data has not yet been acknowledged in the status report.

6. The method of claim 1, wherein the countdown timer is started when the protocol data unit is acquired by a packet data convergence protocol entity, wherein the packet data convergence protocol entity operates as an upper layer of a radio link control entity.

7. The method of claim 6, wherein the countdown timer comprises a Packet Data Convergence Protocol (PDCP) discardTimer.

8. A method for autonomous repeat request enhancement, applicable to a radio link control entity of a user equipment, characterized in that: include: Determine whether the countdown timer value is less than the threshold; In response to the value of the countdown timer being less than the threshold, including a poll in a protocol data unit; as well as The protocol data unit is transmitted.

9. The method according to claim 8, further comprising: In response to transmitting the data protocol unit including the poll, the countdown timer is reset.

10. The method of claim 8, wherein the countdown timer corresponds to transmitted data, wherein the transmitted data has not yet been acknowledged in a status report.

11. The method of claim 8, wherein the countdown timer comprises a Packet Data Convergence Protocol (PDCP) discardTimer.

12. The method of claim 8, wherein the step of including the poll in the protocol data unit comprises: receiving an instruction from a packet data convergence protocol entity; as well as The poll is included in the protocol data unit according to the indication.

13. The method of claim 8, wherein the step of including the poll in the protocol data unit comprises: Determining the importance of the transmitted data based on identification at the radio link control layer; as well as In response to the importance of the transmitted data being high, the poll is included in the protocol data unit.

14. A method for autonomous repeat request enhancement, applicable to a radio link control entity of a user equipment, characterized in that: include: Determine whether the countdown timer value is greater than or equal to the threshold; as well as In response to the value of the countdown timer being less than the threshold, if a negative acknowledgement for a protocol data unit is received in a status report, stopping performing retransmission for the protocol data unit.

15. The method according to claim 14, wherein if the negative acknowledgement of the protocol data unit is received in the status report, stopping the retransmission of the protocol data unit comprises: receiving an instruction from a packet data convergence protocol entity; as well as If the negative acknowledgement for the protocol data unit is received in the status report, stopping the retransmission for the protocol data unit according to the indication.

16. The method of claim 14, wherein the countdown timer comprises a Packet Data Convergence Protocol (PDCP) discardTimer.

17. The method according to claim 14, further comprising: In response to the value of the countdown timer being greater than or equal to the threshold, the retransmission is performed for the protocol data unit if the user equipment receives a negative acknowledgement in a status report or has not been acknowledged in the status report.

18. The method of claim 14, wherein if the negative acknowledgement for the protocol data unit is received in the status report, stopping the retransmission for the protocol data unit comprises: determining the importance of the protocol data unit according to the identification of the radio link control layer; as well as In response to the importance of the protocol data unit being low, if the negative acknowledgement for the protocol data unit is received in the status report, stopping performing the retransmission for the protocol data unit.

19. The method of claim 14, wherein if the negative acknowledgement for the protocol data unit is received in the status report, stopping the retransmission for the protocol data unit comprises: determining whether a radio resource control configuration is set at a radio link control layer of a protocol data unit set; In response to determining that the radio resource control configuration has been set, if the negative acknowledgement for the protocol data unit is received in the status report, stopping the retransmission for the data protocol unit and the remaining one or more data protocol units in the set of data protocol units to which the data protocol unit belongs; as well as In response to determining that the radio resource control configuration is not set, if the negative acknowledgement for the protocol data unit is received in the status report, stopping performing the retransmission for the protocol data unit.

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