WO2007121635A1

WO2007121635A1 - Retransmission method of the control data unit of the wireless link control protocol in the acknowledgment mode

Info

Publication number: WO2007121635A1
Application number: PCT/CN2006/003680
Authority: WO
Inventors: Yunxiang X?
Original assignee: Zte Corporation
Priority date: 2006-04-24
Filing date: 2006-12-29
Publication date: 2007-11-01
Also published as: CN101064587A

Abstract

A retransmission method of the control data unit of the wireless link control protocol in the acknowledgment mode includes: adding a state variable into the control data unit, putting a system time tag on the state variable during the transmission of the control data unit every time; if the negative answer of the control data unit is received, the different value between the current system time and the time tag is calculated, the retransmission control of the control data unit is made by the different value, and the retransmission frequency is reduced. The problem of wasting retransmission resource in the WCDMA system can be resolved effectively, the bandwidth usage frequency can be increased, and the system resource is saved.

Description

TECHNICAL FIELD The present invention relates to a wideband code division multiple access system, and more particularly to a retransmission of a 4-space data unit in a wireless network controller protocol acknowledgement mode. Strategy. BACKGROUND In a WCDMA (Wideband Code Division Multiple Access) system, there are three data transmission methods in the RLC (Radio Link Control) protocol layer of an RNC (Radio Network Controller) network element: Transparent mode (TM), unacknowledged mode (UM), and acknowledge mode (Acknowledged mode, ΑΜ). The AM mode ensures the reliable transmission of data through the transmission confirmation process between the data sender and the data receiver. The protocol architecture is shown in Figure 1. The data transmission process is: a) Sender (transmitter) receives RLC SDU (Service Data Unit service data unit) sent from higher layer > generates RLC PDU (Protocol Data Unit control data unit); b) Sender sends RLC according to transmission capability PDU, update the send window, and the LC PDU is stored in the retransmission sequence until the send window closes to stop sending the AMD PDU; c) The Receiver RLC protocol layer receives the RLC AMD PDU, and if properly received, the Receiver sends an ACK (acknowledgement) status to the Sender. ACK STATUS REPORT, otherwise send NACK (NACK STATUS REPORT); d) Sender receives Receiver status report, according to the type of status report, if it is ACK, it will retransmit the corresponding sequence The RLC PDU is deleted, and the transmission window is updated. If it is a NACK, the corresponding RLC PDU is retransmitted, and the retransmitted RLC PDU has a higher priority than the first transmitted RLC PDU.

The number of AMD PDUs sent by the Sender is controlled by the TFC (Transport Format). Therefore, the effective rate of the transmission is limited by the number of retransmitted AMD PDUs. When the number of retransmitted AMD PDUs increases, the effective data transmission rate decreases. . Receiver status report (STATUS REPORT) according to 3GPP TS 25.322 protocol

] Triggered by three cases: a) When the received Polling bit in the AMD PDU is 1 b) When an AMD PDU is detected to be lost c) When the Timer-Status-Stop timer expires, the condition is only one of them, and Status #艮告禁止 Timer

Timer—Status_Prohibit is in an invalid or timeout state. Receiver sends a status report to Sender. Sender determines the total number of AMD PDUs (including retransmitted AMD PDUs) sent in the next scheduling period based on the status. In the actual application, for the high-speed service, since the maximum transmission window of the RLC AM mode is limited to 4096, in order to avoid the closing of the transmission window, the Receiver is usually required to send a STATUS REPORT to the Sender in time, so that the Sender can update the sliding window in time to ensure that the Sender can update the sliding window in time. Normal delivery of business data. Assuming the traffic rate is V, the valid data payload of the AMD PDU is b, and the transmission window is W. Then, for the transmit window, the latest time to receive the first STATUS is Wb/V, so if the traffic rate is larger, the required time interval is shorter. Correspondingly, for Receiver, after receiving the first AMD PDU, STATUS REPORT is issued at the latest after the Wb/V - T interval, where T is the network loopback delay. Calculated by Τ100ms (compared network loopback delay in LC AM mode), let W be 4096 (maximum window), b = 320bit (3 GPP 4 recommended RLC PDU payload), service rate is 7Mbps, then , Receiver is required to send STATUS REPORT to Sender at the latest 80ms, to ensure that the send window is not closed, set this value to R. Otherwise, after 180 seconds, Sender will cause the data to be sent to 0 because the send window is closed. Sender assumes that the Sender received the NACK status of the A PDU at time t1, and then resends the A PDU. For Sender, the status report of this retransmission will be received after 180ms, and for Receiver, the status report will be sent to Sender after 80ms at the latest, and the A PDU will still be reported to Sender, and the Sender A PDU will be notified to be lost. The status report will be received 130 minutes after Sender resends the A PDU (assuming Sender to Receiver ό network delay and Receiver to Sender network delay λ then, for Sender, the A PDU is unnecessarily retransmitted Processing, wasting transmission bandwidth. Under normal circumstances, the AMD PDU has a maximum polling bit interval of 128 pdu, when tti = 10ms, rlc pdu size = 320, when the service rate is 4M, every 10ms, Sender will trigger the Receiver's status 4 (STATUS REPORT) by setting the Polling bit in the AMD PDU, and the Receiver's status. The report prohibits the timer from being generally set to 20ms, and the network delay is calculated by 100ms, which is at least 6 times the network error rate. SUMMARY OF THE INVENTION The technical problem to be solved by the present invention is to provide a method for retransmitting control data units of a radio link control protocol in an acknowledgement mode, and to solve the problem of waste of retransmission resources of the prior art in high-rate services. In order to achieve the above object, the present invention provides a retransmission method of a control data unit of a radio link control protocol in an acknowledge mode, which is characterized in that it comprises: adding a state variable in a control data unit, and transmitting a control data unit each time The state variable is marked with a system time label; if a negative answer of the control data unit is received, a difference between the current system time and the time label is calculated, and the control data is performed by the difference Retransmission control of the unit to reduce the retransmission frequency. The above method is characterized in that: performing retransmission control of the control data unit by using the difference, comprising: determining whether the difference is greater than a threshold, and retransmitting the control data unit, otherwise giving up hair. The above method is characterized in that it further includes the following steps: Step 1: The transmitter of the radio link control protocol layer receives the control data unit from the upper layer; Step 2, the transmitter adds the state variable to the control data unit And the state variable is marked with a system time label; Step 3, the transmitter sends the control data unit to a receiver of a radio link control protocol layer, and stores the control data unit in a retransmission sequence; Step 4: The transmitter receives a status report from the receiver, and if the status report is a negative response of the control data unit, calculating a difference between a current system time and the time label; Step 5: If it is determined whether the difference is greater than a threshold value, the system time label of the control data unit is updated and the process proceeds to step 3 to resend the control data unit, otherwise the retransmission is abandoned. The above method is characterized in that the threshold value is set according to a status report interval t and a network loopback delay T in the radio link control protocol. The above method is characterized in that, if t > T, the threshold value is set to -1, and in the step 5, the method further includes: if the threshold value is -1, exiting the processing flow; If t < τ, the threshold is set to Χ%Τ, where the parameter X is a value configured according to the actual application. The above method is characterized in that the parameter X is 80. The above method is characterized in that, in the step 4, the method further includes: if the status is a confirmation response of the control data unit, and 4 is updated according to the sequence number of the control data unit that is correctly received. Window, ensuring that the send window does not close. The above method is characterized in that, in the step 2, the transmitter further comprises: determining, according to a status of the current sending window and a system transmission format, the number of control data units that can be currently sent. The technical effect of the present invention is as follows: The present invention adopts a method of time stamping a PDU in a retransmission queue, and when a retransmission is required, calculating a difference between a current time and a time cu of the PDU, when the threshold of the difference is greater than a certain threshold Retransmission is performed, otherwise the retransmission is abandoned to reduce the overhead of network retransmission. By adopting the method of the invention, the problem of waste of high-speed service RLC PDU retransmission resources in the RLC AM mode in the WCDMA system can be effectively solved, and the bandwidth utilization can be effectively improved, and system resources can be saved. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a structure of a mode of operation of a mode 8; FIG. 2 is a flow chart of a method for retransmitting an RLC AM mode provided by the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The implementation of the technical solution will be further described in detail below with reference to the accompanying drawings. The method of the present invention mainly adds an RLC State Variable (VT), when the AMD PDU is sent (including retransmission), Put VT (TAG) on the system time stamp. If the NACK of the PDU is received, the difference between the current system time and the time label VT (TAG) is calculated. If the difference is greater than the threshold TimeThreshold, the AMD PDU is retransmitted, and the update status is changed. Volume VT (TAG), otherwise give up resend. In this way, the retransmission frequency of AMD PDUs is reduced, and system resources and bandwidth utilization are improved. For the setting of the threshold TimeThreshold, it is related to the Status Report interval network loopback delay in the RLC AM protocol. The Status and the Polling related parameters in the protocol are related to the Status Report related parameters. Assuming the Status Report interval is t and the network loopback delay is Τ, then the following setting strategy can be used:

^口果 t > Τ, that is, the Status Report interval is greater than the network loopback delay, then set the TimeThreshold to -1, indicating that the processing of the data is not processed in the processing of data transmission and reception (that is, if the status report interval If the network loopback delay is greater than the network loopback delay, then the correlation processing performed by the present invention is not performed, that is, when the lost PDU is retransmitted, it is necessary to judge the ratio of the time interval between the last retransmission and the retransmission to the threshold); if t < T , that is, the Status Report interval is less than the network loopback delay, then set TimeThreshold = T* 80%, where the percentage is a configurable value to be flexible in practical applications. 2 is a flowchart of the RLC AM mode retransmission method provided by the present invention. As shown in the figure, the method of the present invention includes the following steps: Step 201: The Sender RLC protocol layer receives a high-level RLC AMD PDU (numbered a); Step 202 Sender sends the RLC AMD PDU to the Receiver and stores it in the retransmission sequence. Step 203: The status variable VT (TAG) of the currently sent AMD PDU will be updated. Step 204: Determine whether the Sender receives the status report sent by the Receiver. (Status Report), yes, go to step 205, otherwise go back to step 204; Step 205: Determine whether it is NACK, if yes, go to step 206, otherwise go back to step 201; Step 206: According to the status 4 report content, you need to renumber AMD PDU for a; Sender determines whether SystemTime - VT(TAG) > TimeThreshold, yes, jump to step 201, Sender resends the a number AMD PDU, and updates the value of the state variable VT(TAG); otherwise, jumps to step 204 to wait Receive the next status 4 report. The method of the present invention can also be subdivided into the following steps: l) The Sender AM RLC entity receives the RLC SDU sent from the upper layer.

2) According to the system parameter setting, the AM RLC entity divides or cascades the RLC SDU to construct the LC AMD PDU. 3) Determine the number of PDUs that can be currently sent according to the current transmission window status and the system transmission format.

4) Put the status variable VT (TAG) of the retransmitted PDU into the system time label.

5) Send the PDUs to the Receiver, and store the sent AMD PDUs in the retransmission sequence.

6) After Receiver receives the PDU sent by Sender, Receiver sends Status Report to Sender according to the setting of status report system parameters.

7) After receiving the Receiver, the Sender updates the sending window according to the sequence number of the correctly received PDU, ensuring that the sending window does not close.

8) For AMD PDUs (NAC) in the retransmission queue that are not correctly received, Sender calculates SystemTime - VT(TAG), where SystemTime is the current time of the system, and VT(TAG) is the time stamp sent when the AMD PDU is sent.

9) If SystemTime - VT(TAG) > TimeThreshold, retransmit the current PDU, otherwise, it does not respond to the NACK in the Status Report, where TimeThreshold is the time threshold, set with network delay, Polling in RLC AM mode, and The setting of the related parameters of the status is related to setting the network uplink delay to 80ms, the downlink delay to 60ms, and the Status Report reporting interval to 20ms. At the 46th TTI (TTI = 10ms), the receiver receives the error RLC AMD PDU with the Sequence Number of 113. Send Status Report to inform the receiver that this PDU is missing. The receiver receives this status report at the 54th TTI and retransmits the No. 113 RLC AMD PDU. Since the status report interval is 20ms, starting from the 46th TTI, 48, 50, 52, 54, 56, 58 TTI The status report is sent. At the 60th TTI, the receiver receives the 113 AMD PDU retransmitted by the sender at 54 TTI, and informs the sender in the status report that the AMD PDU No. 113 is not retransmitted. The sender will receive a status report of the lost A13 PDU at 56, 58, 60, 62, 64, 66 TTI for retransmission. At the 68th TTI, the receiver will receive the sender's transmission at 60 TTI. The ACK of the No. 113 PDU is not retransmitted in 4亍. Therefore, the sender does not retransmit the 113 AMD PDIL at the 68th TTI. For the sender, retransmission of the 113 AMD PDU at 56 to 66 TTI is repeated, wasting system bandwidth. In summary, the method can effectively solve the problem of resource waste and bandwidth utilization caused by retransmission in the WCDMA high-rate service by setting the AMD PDU time label. The above are only the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention; all equivalent variations and modifications of the present invention are covered by the scope of the present invention.

Claims

Claim

A method for retransmitting a control data unit of a radio link control protocol in an acknowledgement mode, comprising: adding a state variable to a control data unit, said state being transmitted each time a control data unit is transmitted The variable is marked with a system time label; if the denied response of the control data unit is received, the difference between the current system time and the time label is calculated, and the retransmission control of the control data unit is performed by the difference, Resend the frequency.

The method according to claim 1, wherein the retransmission control of the control data unit by the difference comprises: determining whether the difference is greater than a threshold, and retransmitting the Control the data unit, otherwise give up resending.

The method according to claim 2, further comprising the following steps: Step 1: The transmitter of the radio link control protocol layer receives the control data unit from the upper layer;

Step two, the transmitter adds a state variable to the control data unit, and marks the state variable with a system time label;

Step three, the transmitter sends the control data unit to a receiver of a radio link control protocol layer, and stores the control data unit in a retransmission sequence;

Step 4: The transmitter receives a status report from the receiver, and if the status report is a negative response of the control data unit, calculating a difference between a current system time and the time stamp;

Step 5: Determine whether the difference is greater than a threshold. If yes, update the system time label of the control data unit and go to step 3 to resend the control data unit, otherwise discard the retransmission.

The method according to claim 2 or 3, wherein the threshold value is set by a status report interval t and a network loopback delay T in a radio link control protocol.

The method according to claim 4, wherein if t > T, the threshold is set to -1, and in the step 5, the method further includes: if the threshold is -1 Then exit the steps of the process flow; If t < T, the threshold is set to Χ%Τ, where the parameter X is a value configured according to the actual application. The method according to claim 5, characterized in that said parameter X is 80. The method according to claim 3, wherein the step 4 further comprises: if the status 4 is an acknowledgement of the control data unit, the control data unit is correctly received The serial number, update the send window, to ensure that the send window does not close. The method according to claim 3, wherein the step 2 further comprises: the transmitter determining the number of control data units that can be currently sent according to the current status of the transmission window and the system transmission format.