CN101064663A - Method for retransmitting data in wireless link control protocol - Google Patents

Abstract

The invention discloses a data retransmission method in a wireless link control protocol, which is characterized in that the sending end sends the protocol data unit in the confirmation mode of the wireless link control protocol, and sets a timer corresponding to the data unit, if The sending end receives the status report that the data unit has not been received correctly from the receiving end, then the sending end puts the data unit into the retransmission buffer, and detects the timing corresponding to the data unit during the retransmission buffer scheduling process Whether the timer times out, if yes, send the data unit and start the corresponding timer, otherwise wait for the next buffer scheduling. The invention solves the problem of bandwidth waste caused by multiple retransmissions of the protocol data unit in the case of frequent state reports, reduces invalid retransmission times, and improves bandwidth utilization efficiency.

Description

A method for data retransmission in radio link control protocol

technical field

The invention relates to a wireless link control protocol in the third generation mobile communication system, in particular to an improved method of the data retransmission mechanism in the confirmation mode of the protocol.

Background technique

In the radio link control protocol (RLC), the RLC acknowledgment mode (AM) entity enables the sending end to obtain the receiving status of the receiving end through a mechanism in which the receiving end feeds back a status report to the sending end. For the data PDUs that are not correctly received in the status report ( Protocol Data Unit, protocol data unit), the sender needs to retransmit these PDUs. In the Release 6 version of the RLC protocol, there are three mechanisms for triggering the status report of the receiving end: 1) receiving the polling from the sending end; 2) the upper layer is configured with a mechanism for detecting lost PDUs; 3) the upper layer is configured with a mechanism for sending status reports at regular intervals . There is only one mechanism to prevent the status report from being sent: the upper layer configures a status report prohibition timer.

If the RLC AM receiving end entity does not configure the status report prohibition timer, or the status report prohibition timer is configured relatively short, the triggering of the receiving end status report may be relatively frequent, especially when the polling density of the sending end is relatively high when. In this case, once a data PDU is lost or received incorrectly, multiple status reports will be triggered continuously, and these status reports all indicate that the same data PDU has not been received correctly. For example, if the receiving end finds that the data PDU with the sequence number (SN) of 0 has not been received correctly, it will trigger a status report, instructing the sending end to retransmit the data PDU with SN=0. If both ends have received the poll, the receiving end will send a status report within each TTI that receives the polling, also indicating that the data PDU with SN=0 is lost, until the receiving end correctly receives the retransmitted SN=0 from the sending end of data PDUs. Due to the relatively large round-trip time (RTT) in the mobile communication system, from the receiving end sending the first status report indicating that the data PDU is lost, to receiving the data PDU retransmitted by the sending end, the middle passes through For a long period of time, the receiving end may send multiple status reports during this period, and the sending end retransmits the PDU correspondingly multiple times. The process is shown in Figure 1. In fact, only one retransmission may be required, and the receiving end can correctly receive the PDU, and the rest of the retransmissions are wasteful, reducing the utilization efficiency of valuable wireless bandwidth. On the other hand, if the number of transmissions of the same data PDU reaches the maximum number of transmissions (MaxDAT-1) configured by the upper layer, it will cause SDU (service data unit) discarding or RESET process, resulting in unnecessary data discarding.

Contents of the invention

The technical problem to be solved by the present invention is to provide a data retransmission method in the wireless link control protocol, which solves the problem of bandwidth waste caused by multiple retransmissions of data PDUs in the case of frequent status reports in the prior art.

In order to achieve the above object, the present invention provides a method for retransmitting data in a radio link control protocol, which is characterized in that the sending end sends the protocol data unit in the confirmation mode of the radio link control protocol, and sets the corresponding data unit A timer, if the sending end receives a status report that the data unit has not been received correctly from the receiving end, the sending end puts the data unit into the retransmission buffer, and detects the retransmission buffer scheduling process Whether the timer corresponding to the data unit times out, if so, send the data unit and start the corresponding timer, otherwise wait for the next buffer scheduling.

The above-mentioned method is characterized in that if the sending end receives a status report from the receiving end that the data unit is correctly received, the timer corresponding to the data unit is turned off and the data unit is deleted.

Above-mentioned method is characterized in that, further comprises the following steps:

Step 1, the sending end entity of RLC protocol confirmation mode sends the protocol data unit to the lower layer;

Step 2, setting a timer corresponding to the data unit;

Step 3, if a status report from the receiving end is received, indicating that the data unit has been correctly received, then go to step 8, otherwise, the data unit needs to be retransmitted, go to step 4;

Step 4, putting the data unit that needs to be retransmitted into the retransmission buffer;

Step 5: When the retransmission buffer is scheduled, if the data unit is still in the retransmission buffer, check whether the timer corresponding to the data unit has timed out, if yes, enter step 7, otherwise enter step 6;

Step 6, wait for the next retransmission buffer scheduling and then process the data unit, and turn to step 5;

Step seven, sending the data unit to the lower layer, starting the timer corresponding to the data unit after sending the data unit, and turning to step three;

Step 8: Turn off the timer corresponding to the data unit, and wait for the data unit to be deleted.

The above-mentioned method is characterized in that, in said step 2, said setting the timer corresponding to said data unit further includes: judging whether said data unit is a data unit sent normally for the first time, and if so, does not start timing If a status report from the receiving end is received, indicating that the data unit sent normally for the first time has been correctly received, the sending end deletes the data unit, otherwise the sending end sends the protocol data unit again and starts a timer.

The above method is characterized in that the value of the timer is determined according to the data round-trip time between the sending end and the receiving end.

The above method is characterized in that the value of the timer is equal to the round trip time.

Technical effect of the present invention is:

The invention provides an improved method for the RLC AM data PDU retransmission mechanism, which reduces the waste of bandwidth caused by unnecessary data retransmission, improves the utilization efficiency of the bandwidth, and simultaneously reduces the probability of causing SDU discarding or RESET process.

Description of drawings

Figure 1 is a schematic diagram of the current status of the RLC AM mode data retransmission mechanism;

Fig. 2 is the flow chart of the method for improving RLC AM mode data retransmission provided by the present invention.

Detailed ways

Specific embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The invention provides an improved method for the RLC AM data PDU retransmission mechanism, which can solve the problem of bandwidth waste caused by multiple retransmissions of the data PDU in the case of frequent status reports, reduce the number of invalid retransmissions, and improve Bandwidth utilization efficiency.

Concrete scheme of the present invention is as follows:

For a certain RLC AM data PDU, denote it as PDU(i). After the PDU(i) is sent or retransmitted to the lower layer, a timer Timer_Retransmit_Prohibit is started for the PDU(i), denoted as Timer_trp(i). If a status report from the receiving end is received indicating that the PDU(i) has not been received correctly, the sending end will put the PDU(i) into the retransmission buffer and wait for retransmission. When scheduling the retransmission buffer, check whether the Timer_trp(i) corresponding to the PDU(i) times out. If not, the PDU(i) cannot be sent to the lower layer, and will be processed after the next scheduling. If after Timer_trp(i) expires, PDU(i) is still in the retransmission buffer, then when the retransmission buffer is scheduled, PDU(i) can be sent to the lower layer, after sending, start Timer_trp(i) again.

For the purpose of reducing the number of timers, the timer can be started after the first retransmission of the PDU, and it will not be started when the PDU is sent normally. In this way, it is not necessary to start the timer for most PDUs that do not need to be retransmitted, which can reduce Use of timers.

The value of Timer_Retransmit_Prohibit may be equal to or close to the value of RTT (round trip time), but is not limited thereto. For example, assume that the RTT is 140ms, the TTI (transmission time interval) of the uplink transmission channel is 20ms, the downlink Poll (poll) is relatively intensive, and the downlink receiver is not configured with a status packet prohibition mechanism, so once a PDU is lost, from When the sender retransmits the PDU for the first time and receives the ACK (confirmation) of the PDU from the receiver, it will receive multiple status reports indicating that the PDU is lost, and it needs to retransmit at least 7 times; if Timer_Retransmit_Prohibit Set to 140ms, you may only need one retransmission; if Timer_Retransmit_Prohibit is set to 80ms, you may need two retransmissions; and so on. In addition, it can be seen that if the status packet prohibition timer is configured and its value is greater than the value of Timer_Retransmit_Prohibit, the status packet prohibition timer plays a major role.

Fig. 2 is the flow chart of the RLC AM mode data retransmission improvement method provided by the present invention, as shown in the figure, the concrete steps of the inventive method are as follows:

Step 210: The RLC AM sending end entity sends or retransmits the PDU(i) to the lower layer;

Step 220: Start Timer_trp(i) corresponding to PDU(i);

Step 230: If a status report from the receiving end is received, indicating that the PDU(i) has been received correctly, then proceed to step 280, otherwise, proceed to step 240;

Step 240: when the PDU(i) needs to be retransmitted, put the PDU(i) into the retransmission buffer;

Step 250: During retransmission buffer scheduling, if PDU (i) is still in the retransmission buffer, check whether the Timer_trp (i) of PDU (i) is overtime, if not overtime, then enter step 260, otherwise, enter step 270 ;

Step 260: PDU(i) waits for the next retransmission buffer scheduling and then proceeds to step 250;

Step 270: Send PDU(i) to the lower layer, that is, retransmit PDU(i), and then enter step 220;

Step 280: Turn off the timer Timer_trp(i), and PDU(i) waits to be deleted.

As can be seen from the above, the present invention provides a method for improving the retransmission mechanism of RLC AM data PDUs, which reduces the waste of bandwidth caused by unnecessary data retransmissions, improves the utilization efficiency of bandwidth, and reduces the risk of causing SDUs to be discarded or RESET processes simultaneously. The probability.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the implementation scope of the present invention; all equivalent changes and modifications made according to the present invention are covered by the patent scope of the present invention.

Claims (6)

1. A method for retransmitting data in a radio link control protocol, characterized in that the sending end sends a protocol data unit in the radio link control protocol confirmation mode, and a timer is set corresponding to the data unit, if the sending end After receiving the status report that the data unit has not been received correctly from the receiving end, the sending end puts the data unit into the retransmission buffer, and detects whether the timer corresponding to the data unit is in the retransmission buffer scheduling process Timeout, if yes, send the data unit and start the corresponding timer, otherwise wait for the next buffer scheduling. 2. The method according to claim 1, wherein if the sending end receives a status report of correctly receiving the data unit from the receiving end, closing the timer corresponding to the data unit and deleting the data unit. 3. The method according to claim 1 or 2, further comprising the following steps: Step 1, the sending end entity of RLC protocol confirmation mode sends the protocol data unit to the lower layer; Step 2, setting a timer corresponding to the data unit; Step 3, if a status report from the receiving end is received, indicating that the data unit has been correctly received, then go to step 8, otherwise, the data unit needs to be retransmitted, go to step 4; Step 4, putting the data unit that needs to be retransmitted into the retransmission buffer; Step 5: When the retransmission buffer is scheduled, if the data unit is still in the retransmission buffer, check whether the timer corresponding to the data unit has timed out, if yes, enter step 7, otherwise enter step 6; Step 6, wait for the next retransmission buffer scheduling and then process the data unit, and turn to step 5; Step seven, sending the data unit to the lower layer, starting the timer corresponding to the data unit after sending the data unit, and turning to step three; Step 8: Turn off the timer corresponding to the data unit, and wait for the data unit to be deleted. 4. The method according to claim 3, wherein in said step 2, said setting the timer corresponding to said data unit further comprises: judging whether said data unit is the data sent normally for the first time unit, if it is, the timer will not be started. If a status report from the receiving end is received, indicating that the data unit sent normally for the first time has been correctly received, the sending end will delete the data unit, otherwise the sending end will send the protocol data unit again. data unit and start the timer. 5. The method according to claim 3, wherein the value of the timer is determined according to the data round-trip time between the sending end and the receiving end. 6. The method according to claim 5, wherein the value of the timer is equal to the round trip time.

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