WO2004112407A1 - A method of controlling radio link layer send window - Google Patents

Abstract

A method of controlling radio link layer send window, include: RLC receiver detect if there is any Window Size SUFI information activity, if there is send Window Size SUFI information to RLC sender start the timer; after RLC sender received Window Size SUFI information send response information to RLC receiver; RLC receiver detect whether receive the right response information during the timer period, if receive the right response information, then stop the timer otherwise active Window Size SUFI information. The present invention feedback the receive information of Window Size SUFI information to receiver in time via the response information, even if Window Size SUFI information lose, it would send Window Size SUFI information continuously to adjust the send window avoid decreasing the radio link control protocol bandwidth efficiently.

Description

 Control method of wireless link layer transmission window TECHNICAL FIELD

 The present invention relates to wireless link control in a cellular mobile communication system, and more particularly, to a method for controlling a transmission window of a wireless link layer.

Background technique

 The radio link control (RLC) protocol is a sliding window-based control protocol used to control the transmission of radio link data packets. As shown in Figure 1, the block with a crossed diagonal line at the RLC sender means that the peer has confirmed Packets that have not been received and need to be resent. Shaded squares indicate packets that are waiting for acknowledgement from the peer, blank squares indicate no buffers are occupied; squares with crossed slashes at the RLC receiver indicate that the peer has lost transmission and needs to be re-received Of the data packets, the shaded squares indicate data packets that have been received, and the blank squares indicate no buffers are occupied.

 The basic variables in the RLC protocol are described as follows:

 Configured— Tx-Window-Size: It is the initial value of the sending window configured by the upper protocol layer to the RLC sender, and it is also the maximum size of the sending window; the unit is expressed by the number of PDUs in the protocol data unit; the RLC sender requests a send buffer according to this variable .

 VT (S): is the transmission status variable, which indicates the sequence number of the next protocol data unit PDU to be transmitted, excluding the retransmitted protocol data unit PDU.

 VT (A): is the acknowledgement state variable, which indicates the sequence number of the next consecutive protocol data unit PDU waiting to be acknowledged by the receiver.

 VT (MS): is the maximum transmission state variable. When the serial number of the protocol data unit PDU is greater than or equal to this value, the protocol data unit will not be allowed to be transmitted, and VT (MS) = VT (A) + VT (WS) .

VT (WS): represents the size of the sending window, and its initial value is also the maximum value Configured_Tx_Window_Size, the minimum value is 1 or other upper-layer configured values, and VT (WS) changes within this range.

 Configured— Rx— Window— Size: is the size of the initial receive window configured by the upper protocol layer to the RLC receiver; the unit is the number of PDUs in the protocol data unit; the RLC receiver requests a receive buffer based on this variable.

 VR (R): is the reception status variable, which indicates the sequence number of the next consecutive protocol data unit PDU to be received.

 VR (H): is the highest expected reception state variable, which indicates the sequence number of the highest protocol data unit PDU expected to be received.

 VR (MR): It is the maximum state variable that can be received. When the serial number of the protocol data unit PDU is greater than or equal to this value, the protocol data unit PDU will be rejected by the RLC receiver; and VR (MR) = VR (R) + Conf igured— Rx— Window_Size.

 The RLC receiver informs the RLC sender that some packets have been received and some packets are not received through the status packet PDU. When the RLC sender receives these status packet PDUs, it changes the acknowledgement status variable VT (A). Value, thereby pushing forward the maximum transmission state variable VT (MS) to ensure that data is continuously transmitted.

 When the RLC sender detects that a certain protocol data unit PDU has not been answered by the peer, as shown by the cross-hatched block in the RLC sender in Figure 1, the value of the transmission state variable VT (S) will increase continuously until The value of the maximum transmission state variable VT (MS) is reached, and then data with a sequence number greater than or equal to the maximum transmission state variable VT (MS) is no longer transmitted.

When the RLC receiver detects that a certain protocol data unit PDU has not been received, as shown by the cross-hatched block at the RLC receiver, the value of the highest expected reception state variable VR (H) will increase continuously until it reaches The maximum allowable state variable VR (MR), and then no longer receive data with a serial number greater than or equal to the maximum allowable state variable VR (MR). It is stipulated in the existing protocol that the RLC receiving end controls the window size of the data sent by the RLC sending end according to its own receiving buffer, thereby controlling the bandwidth usage of the wireless link. The method is to send a status packet PDU containing the window size indication (Window Size SUFI) information to the RLC sender. The structure of the Window Size SUFI information is as follows:

 TYPE = WINDOW

 WSN

Among them, the length of TYPE is 4 bits, when TYPE-0001, it means the window WINDOW; the length of WSN is 12 bits, which is used to change the size of the send window of the RLC sender.

 When the RLC sender receives the Window Size SUFI message, it changes the size of the send window VT (WS) to WSN. If the WSN is equal to 0, the SUFI information is discarded; if the WSN is greater than the maximum transmission window size Configured_Tx_Window_Size, the size of the transmission window VT (WS) is taken as Configured_Tx_Window_Size. When the wireless link deteriorates, data loss may occur, causing the RLC receiver to increase its cache. At this time, the RLC receiver uses Window Size SUFI information to reduce the data sent by the RLC sender, and notifies the RLC sender to reduce the size of the send window. VT (WS), thereby reducing the sending window and avoiding data congestion. When the RLC receiver detects that the available space in the receive buffer is increasing and reaches certain thresholds, as shown in Figure 2, all retransmitted packets have been received at this time, and the RLC receiver does not occupy a buffer. The Window Size SUFI message informs the RLC sender to increase the size of the send window VT (WS), thereby increasing the send window and avoiding a decrease in the bandwidth utilization efficiency of the data link.

 According to the actual measurement of different services, the PDU drop rate of some non-real-time data services can reach 10%. Under a good wireless environment, the drop rate specified by the RLC protocol does not exceed 0.7%, so the probability of window size SUFI information loss is higher.

Window Size SUFI information is critical to the bandwidth use of the wireless link, but RLC The protocol does not provide protection for such a critical message to ensure that the RLC sender can receive the message. The triggering mechanism of different Window Size SUFI information has different effects on the bandwidth utilization efficiency of wireless links. There is no uniform standard for triggering Window Size SUFI information in the RLC protocol. Currently, the triggering method generally used is: the remaining space of the receiving buffer Relative change ratio trigger mode and fixed-point trigger mode. When the receiving end determines that it is necessary to send the Window Size SUFI information, it only triggers the sending of the Window Size SUFI information once. It may take a long time to trigger it later. If the sending end does not receive it, the window cannot be adjusted. Especially when the wireless link transitions from a bad state to a good state, the RLC receiver requires the RLC sender to increase the Window Size SUFI information of the send window size only once. Once this information is lost, the send window cannot be adjusted, especially When the wireless quality becomes better and the packet loss rate decreases, the RLC receiver will no longer trigger the Window Size SUFI message. During this period, even if the wireless link is good, the sending window will still maintain the state when the link is bad. Wireless link Sending data at a very low rate causes a serious drop in the speed of the wireless link.

Summary of the Invention

 The technical problem to be solved by the present invention is to provide a wireless link layer transmission window control method, which effectively overcomes the prior art when the Window Size SUFI information is lost, the RLC receiving end cannot know whether the transmitting end receives the transmission window adjustment information, The inability to continue to send Window Size SUFI information to adjust the sending window causes a defect that the bandwidth use efficiency of the radio link control protocol is reduced.

 The method for controlling a transmission window of a wireless link layer according to the present invention includes the following steps: Step 1. The RLC receiving end sets a timer;

Step 2: The RLC receiver detects whether a Window Size SUFI message is triggered. If a Window Size SUFI message is triggered, it sends a Window Size to the RLC sender. SUFI information, start timer;

 Step 3: After receiving the Window Size SUFI information, the RLC sender sends a response message to the RLC receiver;

 Step 4. The RLC receiver detects whether the correct response message is received during the timer. If the correct response message is received, the timer is stopped. Otherwise, the Window Size SUFI message is triggered, and the process returns to step 2.

 The response information sent by the RLC sender to the RLC receiver includes WSN information in the Window Size SUFI information received by the RLC sender.

 After receiving the response information, the RLC receiver parses the WSN information in it, and if it is consistent with the WSN information in the Window Size SUFI information sent last time, it is regarded as the correct response information.

 According to the present invention, the receiving status of the Window Size SUFI information is fed back to the receiving end in time by the response information. Even if the Window Size SUFI information is lost, the Window Size SUFI information can continue to be sent, and the sending window can be adjusted in time to effectively avoid the decline in the efficiency of the wireless link control protocol bandwidth usage .

BRIEF DESCRIPTION OF THE DRAWINGS

 Figure 1 is a schematic diagram of a radio link control protocol;

 FIG. 2 is a schematic diagram of a conventional RLC receiving end notifying an RLC sending end to change a sending window size through a status packet PDU including Window Size SUFI information;

 FIG. 3 is a flowchart of an RLC transmitting end in the method of the present invention;

 FIG. 4 is a flowchart of the RLC receiving end in the method of the present invention.

detailed description

 The method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

The present invention receives Window by setting Window Ack SUFI as the RLC sender. After the Size SUFI message is returned to the RLC receiver, the RLC receiver can learn and resend the Window Size SUFI message even if the Window Size SUFI message is lost.

 The composition of the Window Ack SUFI message is as follows:

 TYPE = Window Ack

 WSN

The length of the WSN is 12 bits, which is set to the WSN value in the latest Window Size SUFI information received.

 As shown in FIG. 3, the specific steps of the RLC sender in the method of the present invention are as follows:

 Step 1. The RLC sender checks whether it has received the Window Size SUFI message sent by the RLC receiver. If it receives, it goes to step 2; otherwise, it continues to detect.

 Step 2. The RLC sender parses the WSN value in the received Window Size SUFI information, and sets the WSN in the Window Ack SUFI information to this value.

 Step 3. The RLC sender sends the Window Ack SUFI information to the RLC receiver. Go to step 1.

 As shown in FIG. 4, the specific steps of the RLC receiving end in the method of the present invention are as follows:

 Step 1. Set the timer Timer_Window_Ack on the RLC receiver. The timer can be set to any value from 100ms to 2000ms.

 Step 2. The RLC receiver detects whether a Window Size SUFI message is triggered. If yes, go to step 3; otherwise, go to step 4.

 Step 3. The RLC receiver sends Window Size SUFI information and starts the timer Timer_Window_Ack. Go to step 5.

Step 4. The RLC receiver detects whether the Tinier_Window_Ack timer is running. If it is not running, go to step 2. Otherwise, go to step 5. Step 5. If the RESET process occurs at the RLC receiving end, go to step 10; otherwise, go to step 6.

 Step 6. Determine whether the timer Timer_Window-Ack has timed out. If it is timed out, go to step 9; otherwise, go to step 7.

 Step 7. The RLC receiver detects whether there is a new Window Size SUFI message to be sent. If it has, go to Step 9, otherwise go to Step 8.

 Step 8. The RLC receiver checks whether it has received the correct Window Ack SUFI information. If it receives, go to step 10; otherwise, go to step 9.

 Step 9. Trigger Window Size SUFI message, go to step 2. The window size SUFI information is triggered by setting a trigger flag on the RLC receiver.

 Step 10. Stop the timer Timer—Window—Ack. Go to step 2. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technology of the present invention can be Modifications or equivalent replacements of the solutions without departing from the spirit and scope of the technical solutions of the present invention should be covered by the claims of the present invention.

Claims

Claim  1. A method for controlling a transmission window of a wireless link layer, comprising: Step 1: a RLC receiving end sets a timer;  Step 2: The RLC receiver detects whether a Window Size SUFI message is triggered. If a Window Size SUFI message is triggered, it sends a Window Size SUFI message to the RLC sender to start a timer.  Step 3: After receiving the Window Size SUFI information, the RLC sender sends a response message to the RLC receiver;  Step 4. The RLC receiver detects whether the correct response message is received during the timer. If the correct response message is received, the timer is stopped. Otherwise, the Window Size SUFI message is triggered, and the process returns to step 2.  2. The method for controlling a wireless link layer transmission window according to claim 1, wherein the timer is set to any value from 100ms to 2000ras.  3. The method for controlling a wireless link layer transmission window according to claim 1, wherein the triggering of the Window Size SUFI information in the step 4 is implemented by setting a trigger flag on the RLC receiving end.  4. The method for controlling a wireless link layer transmission window according to claim 1, further comprising detecting whether a reset process occurs by the RLC receiving end, and if the reset process occurs, stopping the timer operation and returning to step 2.  5. The method for controlling a wireless link layer transmission window according to claim 1, wherein the step 4 further comprises: when the RLC receiving end detects whether the correct response information is received during the timer, if the detecting When there is a new Window Size SUFI message to be sent, the Window Size SUFI message is triggered, and the process returns to step two. 6. The wireless link layer transmission window according to any one of claims 1 to 5. The method for controlling an interface is characterized in that, in step 3, the response information sent by the RLC sender to the RLC receiver includes the WSN information in the Window SI SUFI information received by the RLC sender.  7. The method for controlling a wireless link layer transmission window according to claim 6, wherein the step of detecting whether the RLC receiving end receives correct response information during the timer comprises: the RLC receiving end detecting whether the receiving end receives To the response information, if received, parse the WSN information to determine whether the WSN information is consistent with the WSN information in the Window Information SUFI message sent last time; if they are the same, it is considered to be the correct response information; otherwise, Incorrect response message.