KR20100060853A - Method and system for reporting status at radio link control protocol - Google Patents

Abstract

PURPOSE: A method and a system for reporting status in a wireless link control protocol are provided to increase the throughput of a sending end and a receiving end by taking care of a re-transmission request of the sending end that results from the reception delay phenomenon of the receiving end. CONSTITUTION: Data is received from a sending end(S405). Any loss of the received data is determined(S415). A reception confirmation status reporting message is transmitted when there are no damages to the data(S425). The operation of a confirmation timer is initiated(S430). The termination of the confirmation timer is verified(S440). The following reception confirmation status reporting message is transmitted to the transmitting end(S445). A re-transmission request status reporting message is transmitted when the data is damaged(S455). The operation of a re-transmission timer is initiated(S460). The following re-transmission request status reporting message is transmitted to the transmitting end(S475).

Description

METHOOD AND SYSTEM FOR REPORTING STATUS AT RADIO LINK CONTROL PROTOCOL}

The present invention relates to a status reporting method and system in a radio link control protocol. More specifically, the present invention provides a status reporting method in a radio link control protocol for determining whether a data loss received by a receiver is reported to a transmitter and separately setting a transmission time limit for the next status report according to the status report. And to the system.

Wideband-Code Division Multiple Access (W-CDMA) is a code division-based wireless mobile communication technology, and is capable of transmitting information such as voice, circuit data, and packet data. It is possible. In a wireless mobile communication technology such as W-CDMA, data loss may occur during data transmission due to signal degradation in a wireless section. Therefore, a method for reliable data transmission between a transmitter and a receiver performing wireless communication is needed.

In W-CDMA, a Radio Link Control (RLC) protocol is specified to ensure reliable data transmission between a transmitter and a receiver. The RLC protocol is located between a medium access control (MAC) layer and a radio resource control (RRC) layer. In particular, in RLC's Acknowledgment Mode, various procedures and Control Protocol Data Units (PDUs) are used to transmit data in sequence number order. do.

Meanwhile, in the RLC protocol, the receiver periodically reports a status PDU report to the transmitter for reliable data transmission. The status report includes an acknowledgment or data retransmission request. The acknowledgment is a message confirming that the receiving end has received all the received data. The data retransmission request is a message for which a receiving end requests retransmission to the transmitting end because a loss occurs during data receiving.

In this case, the receiving end limits the retransmission request at the receiving end for a predetermined time in order to prevent repetition of unnecessary data retransmission requests. This is called a transmission timeout (Status_Prohibit_Timer). However, in the related art, there is a problem that the throughput of the RLC protocol and the receiver reduce the throughput by not distinguishing the transmission time limit according to the acknowledgment and the retransmission request.

Disclosure of Invention The present invention is to solve the above problems, and to increase the throughput of the transmitter and the receiver by separately setting the transmission time limit of the next status report according to the status report type of the acknowledgment and retransmission request in the RLC protocol. have.

In the radio link control protocol of the present invention for solving the above problems, a status report method of a receiving end receives data transmitted from a transmitting end to determine whether data is lost or not, and when data is lost, acknowledgment Transmitting a status report message and starting an operation of a confirmation timer; when reporting the next acknowledgment status, transmitting the next acknowledgment status report message to the transmitting end when the end of the confirmation timer is confirmed; Transmitting a status report message and initiating operation of a retransmission timer and transmitting a next retransmission request status report message to the transmitting end when the retransmission timer is confirmed when the next retransmission request status is reported. .

According to another aspect of the present invention, a method for reporting a status of a receiver in a radio link control protocol transmits a status report message according to whether data is lost or not, and sets a transmission time limit of a timer according to a status report type separately. Starting an operation of the controller, determining whether a transmission time limit of a timer according to the status report type has elapsed when reporting the next state, and transmitting a next status report message to the transmitter when the transmission time limit has elapsed. Characterized in that.

In addition, the state reporting system of the radio link control protocol including a transmitting end and a receiving end of the present invention for solving the above problems is the transmitting end and the transmission data for sequentially transmitting the data having a sequence number to the receiving end whether And a receiving end generating a status report message according to the present invention and transmitting the same to the transmitter, separately setting a transmission time limit of a timer according to the status report type, and starting the timer.

According to the status reporting method and system therefor in the radio link control protocol of the present invention, the transmission time limit of the status report can be separately set according to the status report type of the acknowledgment and retransmission request. Therefore, if data loss occurs frequently due to radio link deterioration, the sender repeatedly solves the problem of requesting retransmission by repeatedly transmitting data of the same sequence number in the sender, which is caused by a delay in the receiving end after sending data from the sender. And increase the throughput of the receiving end.

The terminology described in the present invention conforms to the definition defined in the standard document 3GPP (The 3rd Generation Partnership Project) TS 25.322. However, it is not necessarily limited to this, and for ease of explanation, it should be noted that some terms may be redefined and used herein.

RLC, the W-CDMA air interface protocol of the present invention, is located between the MAC layer and the RRC layer. The RLC may operate in three modes, a transparent mode, an unacknowledged mode, and an acknowledgment mode. Transparent mode primarily provides voice services, while Unacknowledge Mode provides video conferencing and video telephony services. Acknowledgment mode (hereinafter referred to as AM mode of RLC protocol) is mainly used in interactive or background services for packet data, and can also be used in streaming services.

In the AM mode of the RLC protocol, data (or 'data PDU', hereinafter identical) is transmitted in a sequential transmission method (or 'in-sequence delivery', hereinafter identical). In other words, in the AM mode of the RLC protocol, data is sequentially transmitted from the transmitting end to the receiving end in sequence number order. The RLC protocol of the embodiment of the present invention described below is assumed to operate in AM mode, but is not necessarily limited thereto.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that, in the drawings, the same components are denoted by the same reference symbols as possible. Further, the detailed description of well-known functions and constructions that may obscure the gist of the present invention will be omitted.

In general, a round trip time delay (RTT) occurs until the receiver sends a status report message to the transmitter. The RTT is generated between the transmitting end and the receiving end due to protocol-specific processing time, relay line delay, and wireless delay.

If data loss (or 'Missing Data', hereinafter, the same) occurs continuously due to radio degradation, such data may be lost while the receiver is in the process of retransmitting the retransmission request from the receiver due to this RTT factor. The re-occurrence of may cause an inefficient retransmission mechanism for repeatedly transmitting data retransmission requests for the same sequence number to the transmitting end.

For example, it is assumed that after receiving data having sequence numbers 1, 2, 4, and 5 at the receiving end, data retransmission of sequence number 3, which is lost data, is requested to the transmitting end. Thereafter, when the receiving end receives data having a sequence number of 7 while the transmitting end does not receive the retransmission request, loss of data having a sequence number of 6 occurs. Then, the transmitting end requests data retransmission of sequence number 3 and sequence number 6, which are lost data. In this case, there is a problem that the transmitting end repeatedly receives the retransmission request for the data having sequence number 3.

In addition, the RLC entity on the receiving end side in the downlink direction not only receives data and reports a status thereof, but also performs a role of transmitting end transmitting data on the uplink. In this case, if the receiving end frequently transmits a status report, the uplink data transmission processing as the transmitting end is delayed, resulting in a decrease in throughput.

Therefore, in order to maximize the throughput between RLC entities, a transmission time limit for prohibiting the transmission of the status report message for a predetermined time in consideration of the RTT is required when transmitting the status report message.

1 is a diagram illustrating a process of transmitting a status report (or 'Status PDU Report', hereinafter, identically) message after a transmission time limit, in order to solve the problem of repeatedly requesting retransmission by repeatedly repeating the same sequence number data. Flowchart.

In step S110, the receiving end determines whether a data loss occurs in the data being transmitted. The receiving end may recognize that data loss has occurred when receiving data having a sequence number having a value larger than the expected sequence number of data.

If the data loss is not detected, the receiver determines whether the polling period has elapsed in step S120. Here, the polling period means a period during which a polling identifier for transmitting a request for confirmation whether a transmitting end has lost data transmission to the receiving end is transmitted. The receiving end receiving the polling identifier determines whether data lost before the identifier is received and reports the result to the transmitting end.

If data loss is detected or the polling period has elapsed, the receiving end generates a status report message in step S130. In this case, when no data loss occurs, the receiver generates an acknowledgment status report (or 'ACK Status PDU', hereinafter identical) message indicating that all data transmitted by the transmitter has been received. On the other hand, when data loss occurs, a retransmission request status report (or 'Retransmission Status PDU', hereinafter identical) message requesting retransmission of lost data is generated. The receiving end transmits the generated status report message to the transmitting end.

In step S140, the receiving end transmitting the status report operates a timer to check whether the transmission time limit has elapsed. In operation S150, the receiving end determines whether the timer has expired, that is, whether the transmission time limit has elapsed.

When the transmission time limit has not elapsed, the receiver does not transmit a status report message to the transmitter even if data loss occurs among the received data. On the other hand, when the transmission time limit elapses, the receiving end generates a status report to be transmitted next in step S160 and transmits it to the transmitting end.

The conventional transmission time limit is commonly applied to the acknowledgment status report and the retransmission request status report.

However, in order to maximize the transmission throughput at the transmitting end, the acknowledgment status report message at the receiving end should be transmitted to the transmitting end as soon as possible. Similarly, in order to maximize the transmission throughput of the transmitting end, the retransmission request status report message of the receiving end needs to delay the retransmission request such that the data of the same sequence number is not retransmitted in consideration of the RTT.

Therefore, it is necessary to maximize the transmission throughput of the transceiver by separately setting the transmission time limit according to the type of status report.

2 is a conceptual diagram illustrating a concept of an AM mode operation process of the RLC protocol of the present invention.

In step S230, the transmitting end 210 sequentially transmits data to be transmitted to the receiving end 220 in sequence number order. When the polling period has elapsed, the transmitter 210 transmits a polling identifier to the receiver 220 in step S235 and requests the receiver 220 to report its status.

The receiver 220 first transmits an acknowledgment or retransmission request message for a plurality of data through the status report in step S240. In this case, the receiver 220 may use a bitmap, a list, a related list, a related list, or the like for the retransmission request. The bit map may indicate ACK / NACK information as 0 or 1 to report up to 128 data states. In addition, the list may indicate how many data have been lost continuously from the data in which an error occurs, and may report a state of the plurality of data. In an embodiment of the present invention, it is possible to make a request for retransmission of lost data using any one of a bitmap, a list, and a related list.

The receiver 220 may transmit an acknowledgment status report or a retransmission request status report message according to whether data is lost. In operation S245, the receiving end 220 which transmits the first status report message starts the operation of a timer according to the status report type. In other words, when the receiver 220 transmits the acknowledgment status report message, the acknowledgment timer (or 'ACK_STATUS_PROHIBIT_TIMER', which is the same below) is operated. The acknowledgment timer refers to a timer that counts a period of transmitting an acknowledgment status report message.

In addition, when the receiving end 220 transmits the retransmission request status report message, the retransmission timer (or 'Retx_Status_Prohibit_Timer', which is the same below) is operated. The retransmission timer refers to a timer that counts a period for transmitting a retransmission request status report message.

The receiver 220 continuously receives the data transmitted from the transmitter 210 after transmitting a status report message in step S240. In addition to receiving the data, the receiver 220 counts whether the transmission time limit of each timer has elapsed according to the status report type.

In addition, the receiving terminal 220 may detect the need for an acknowledgment status report in step S260. This may be the case when a polling identifier is received from the transmitter 210 and data loss is not confirmed until the reception. Then, the receiving end 220 determines whether the timer for the acknowledgment status report, that is, the transmission time limit of the acknowledgment timer, has elapsed in operation S265. The receiver 220 transmits an acknowledgment status report message to the transmitter 210 only when the transmission time limit elapses.

Similarly, the receiving end 220 may detect the necessity of retransmission request status report in step S270. This may be the case when a polling identifier is received from the transmitter 210 and data loss is confirmed until the reception. The retransmission request status report may occur when data loss is detected, even if the receiver 220 does not receive the polling identifier as described above. Then, the receiving end 220 determines whether the timer for the retransmission request, ie, the retransmission timer, has elapsed before the operation has been started in step S275. The receiver 220 transmits a retransmission request status report message to the transmitter 210 only when the transmission time limit elapses.

FIG. 3 is a diagram illustrating a method of managing data by setting a window at a transmitting end 210 and a receiving end 220 in the AM mode of the RLC protocol of the present invention. In this case, a window set in the transmitter 210 is called a transmission window 310, and a window set in the receiver 220 is called a receiving window 320.

The transmitter 210 manages the transmission data in the transmission window 310 until it receives an acknowledgment status report message for the data transmitted by the transmitter 210 from the receiver 220. Similarly, the receiver 220 processes the sequence numbers of the data transmitted from the transmitter 210 in order and stores and manages data in which the sequence numbers are not continuously received in the reception window 320 in order to transmit them to the higher protocol.

Parameters for managing the transmission window 310 and the reception window 320 shown in FIG. 3 and their uses will be described below.

The VT (A) of the transmission window 310 is the next value of the sequence number of the data that received the acknowledgment status report last. The initial value of the VT (A) is zero. The acknowledgment status report is transmitted separately from the retransmission request status report.

The VT (S) of the transmission window 310 refers to a sequence number of data (excluding data to be retransmitted) to be transmitted to the lower protocol in the next order among the service data units (SDUs) received by the higher protocol. The VT (S) is updated with every new data transmission and the initial value is zero.

The VT (MS) of the transmission window 310 represents the size of the transmission window 310, and the size (TX_WND_SZ) of the transmission window is designated by the upper protocol. Therefore, when VT (S) is greater than or equal to VT (MS), the transmitting end 210 does not transmit data having a sequence number greater than or equal to VT (MS). That is, the transmitter 210 transmits only data corresponding to the sequence number of 'VT (MS) -1'.

The VR (R) (Receive State Variable) of the reception window 320 refers to a sequence number following a sequence number of data last received by the receiver 220. That is, when data having the same sequence number as VR (R) is received, VR (R) is updated to 'received sequence number + 1'. Since the initial value of the VR (R) is 0, it is not updated until data having a sequence number of 0 is received, and thereafter, if the data is not received in sequence number order (that is, data loss occurs), it is not updated. . When a data loss occurs, the VR (R) is updated when the receiver 220 requests retransmission for the lost data and re-receives the requested data. In this case, the retransmission request of the receiver 220 occurs after the transmission time limit for the retransmission request has elapsed, which is processed separately from the transmission time limit for the acknowledgment.

VR (H) (Highest Expected State Variable) of the reception window 320 indicates a value after the largest value among the sequence numbers of the received data and has an initial value of 0.

Maximum Acceptable Receive State Variable (VR) of the reception window 320 represents an upper limit of the reception window 320 and the size of the reception window (RCV_RCV_WND_SZ) is specified in the higher protocol. If the receiver 220 receives data having a sequence number greater than VR (MR), the reception is rejected. The VR (MR) is updated at the same time when the VR (R) is updated, and the initial value is set by the user.

The transmitter 210 moves VT (A) and VT (MS) values of the transmission window 310 when the acknowledgment status report message is received from the receiver 220 with respect to the data already transmitted. In this case, the period for receiving the acknowledgment status report message is processed separately from the period for receiving the retransmission request status report message. Then, the transmitter 210 may transmit new data having a sequence number larger than that of the conventional VT (MS).

Meanwhile, in the AM mode of the RCL protocol, data is transmitted in a sequential transmission method. Accordingly, the receiving end 220 recognizes that data loss has occurred when data having a sequence number of a value greater than VR (R) is not received while data having a sequence number expected to be received next is VR (R). The receiving end 220 then stores the received data in the receiving window 320, and does not pass the received data to the upper layer of the RCL protocol. When the transmission time limit for the retransmission request elapses, the receiving end 220 requests the transmitting end 210 to retransmit the lost data.

4 is a flowchart illustrating a process of transmitting a next status report message by separately setting a transmission time limit according to a status report type according to an exemplary embodiment of the present invention.

First, the receiver 220 receives the data transmitted from the transmitter 210 in step S405. Since the present invention can operate in the AM mode of the RLC protocol, the received data is sequentially transmitted according to the sequence number, and the transmitted data unit may be a PDU.

In addition, the receiving terminal 220 determines whether there is a need to report the status of the data received so far in step S410. This may be the case when the receiving end 220 receives a polling identifier from the transmitting end 210 or a data loss occurs. If there is no need for status reporting, the receiving end 220 continues to receive data.

On the other hand, if there is a need for status reporting, the receiver 220 determines whether a loss has occurred for the data received so far in step S415. The receiving end 220 according to an embodiment of the present invention may determine that data is not received as a sequence number as a case where data loss occurs.

If no data loss occurs, the receiver 220 determines whether the confirmation timer is operating in step S420. If the acknowledgment timer is not operated, the receiver 220 transmits an acknowledgment status report (ACK Status PDU) message in step S425. In operation S430, the receiving end 220 starts the operation of the acknowledgment timer Ack_Status_Prohibit_Timer.

Thereafter, when the receiving end 220 detects a situation in which the acknowledgment status report should be transmitted in step S435, it is determined whether the transmission time limit of the confirmation timer that has previously started operation in step S440 has elapsed. If the transmission time limit has not elapsed, the receiving end 220 does not transmit an acknowledgment status report message until the transmission time limit elapses. After receiving the transmission time limit for the acknowledgment status report, the receiving end 220 transmits the next acknowledgment status report message in step S445.

On the other hand, if the confirmation timer is already in operation in step S420, the receiver 220 proceeds to step S440. And the receiving end 220 transmits the next acknowledgment status report message after the transmission time limit of the acknowledgment timer that started operation has elapsed.

On the other hand, if a data loss occurs in step S415, the receiver 220 determines whether the retransmission timer is in operation S450. If the retransmission timer is not operated, the receiver 220 transmits a retransmission request status report (Retransmission Status PDU) message in step S455. In operation S460, the receiving end 220 starts the operation of the retransmission timer Retx_Status_Prohibit_Timer.

Thereafter, when the receiving end 220 detects a situation in which the retransmission request status report should be transmitted in step S465, it is determined whether the transmission time limit of the retransmission timer that has previously started operation in step S470 has elapsed. If the transmission time limit has not elapsed, the receiving end 220 does not transmit the retransmission request status report message until the transmission time limit elapses. The receiver 220 transmits the next retransmission request status report message in step S445 after the transmission time limit for the retransmission request status report has elapsed.

On the other hand, if the retransmission timer is in operation at step S450, the receiver 220 proceeds to step S470. And the receiving end 220 transmits the next retransmission request status report message after the transmission time limit of the retransmission timer that has previously started operation.

As described above, according to the present invention, the next status report transmission time limit is separately set. In other words, the acknowledgment status report message is transmitted as quickly as possible, and the retransmission request status report message is set to separate transmission timeouts so as not to retransmit data of the same sequence number in consideration of RTT. Can maximize transmission throughput.

The embodiments of the present invention disclosed in the present specification and drawings are merely illustrative of specific embodiments of the present invention and are not intended to limit the scope of the present invention in order to facilitate understanding of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

1 is a flowchart illustrating a process of transmitting a status report message after a transmission timeout period is solved in order to solve a problem of repeatedly requesting retransmission of data of the same sequence number.

2 is a diagram illustrating an AM mode operation process of the RLC protocol of the present invention.

3 is a diagram illustrating a method for managing data by setting a window at a transmitting end 210 and a receiving end 220 in the AM mode of the RLC protocol of the present invention.

4 is a flowchart illustrating a process in which the receiving end 220 transmits a next status report message by separately setting a transmission time limit according to a status report type according to an embodiment of the present invention.

Claims (12)

In the status report method of the receiving end in the radio link control protocol, Receiving data transmitted from a transmitter to determine whether data is lost; Sending an acknowledgment status report message and initiating operation of the acknowledgment timer when no data is lost; Transmitting a next acknowledgment status report message to the transmitting end when the end of the acknowledgment timer is confirmed when the next acknowledgment status is reported; Upon data loss, transmitting a retransmission request status report message and starting the retransmission timer; And And transmitting the next retransmission request status report message to the transmitting end when the retransmission request status is confirmed when the next retransmission request status is reported. In the status reporting method of the receiving end in the radio link control protocol, Transmitting a status report message according to whether there is a loss of received data to a transmitter, separately setting a transmission time limit of a timer according to a status report type, and starting an operation of the timer; Determining whether a transmission time limit of a timer according to the status report type has elapsed when the next status report is reported; And And transmitting a next status report message to the transmitting end when the transmission time limit has elapsed. The method of claim 2, The status report is either an acknowledgment status report confirming reception of all data transmitted by the transmitter, or a retransmission request status report requesting retransmission of data lost due to data loss. How to report the status of the receiving end in the protocol. The method of claim 3, The transmission time limit for the acknowledgment status report and the transmission time limit for the retransmission request status report have a different length of time. The method of claim 4, wherein The transmission time limit for the retransmission request status report is set so that a data retransmission request for the same sequence number is not repeatedly transmitted to the transmitting end. The method of claim 2, And the status report message is generated when a polling identifier is received. In the state reporting system of a radio link control protocol comprising a transmitting end and a receiving end, A transmitter for sequentially transmitting data having a sequence number to the receiver; And And a receiving end generating a status report message according to whether the transmitted data is lost and transmitting it to the transmitting end, separately setting a transmission time limit of a timer according to the status report type, and starting the operation of the timer. A status reporting system of a radio link control protocol. The method of claim 7, wherein The receiver determines whether the transmission time limit of a timer according to the status report type has elapsed when reporting the next state, and transmits a next state report message to the transmitting end when the transmission time limit elapses. Status reporting system. The method of claim 8, The status report is either an acknowledgment status report confirming reception of all data transmitted by the transmitter, or a retransmission request status report requesting retransmission of data lost due to data loss. Receive status reporting system in the protocol. 10. The method of claim 9, The transmission time limit for the acknowledgment status report and the transmission time limit for the retransmission request status report have a different length of time. The method of claim 10, The transmission time limit for the retransmission request status report is set so that a data retransmission request for the same sequence number is not repeatedly transmitted to the transmitting end. The method of claim 7, wherein And the status report message is generated when a polling identifier is received.

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