KR20060100081A - Method and apparatus for dynamically managing a retransmission persistence - Google Patents

Abstract

  According to the present invention, in order to solve the problem of the ARQ scheme using the fixed fixed retransmission persistence, the data frame received from the buffer input terminal of the transmitting node is received according to the amount of data accumulated in the ARQ buffer. We propose a method of dynamically setting the number of retransmission allowances of the ARQ according to the time until the ACK signal is received from the node (transmission delay time). That is, when the amount of data waiting for transmission in the buffer of the ARQ transmitter is small, a large number of high-persistence is allowed, and when the amount is large, only a relatively low low-persistence is allowed. In particular, when the amount of data accumulated in the ARQ buffer exceeds the congestion threshold, retransmission is not performed. The amount of traffic imposed on the ARQ is based on the amount of data accumulated in the buffer, and the number of retransmission attempts for one frame is inversely proportional to the amount of data stored in the buffer.

ARQ, Permit Permit for Retransmission

Description

Method and apparatus for dynamically adjusting the number of retransmissions allowed in the ARR system {METHOD AND APPARATUS FOR DYNAMICALLY MANAGING A RETRANSMISSION PERSISTENCE}

 Figure 1 (a) is a diagram of a stop-standby ARQ scheme.

 Figure 1 (b) is a diagram of a GBN ARQ scheme.

 1 (c) is a diagram related to the SR ARQ scheme.

 2 is a flowchart illustrating a method of adjusting a number of retransmission allowances according to an embodiment of the present invention.

 3 is a flowchart illustrating a method of adjusting a number of retransmission allowances according to another embodiment of the present invention.

 4 is a flowchart illustrating a method of adjusting a number of retransmission allowances according to another embodiment of the present invention.

 5 is a diagram illustrating an example of adjusting the number of retransmission allowances in a stop-standby ARQ system according to an embodiment of the present invention.

 6 is a diagram illustrating a configuration of a transmitting node having an apparatus for adjusting the number of retransmission allowances according to an embodiment of the present invention.

 7 (a)-(c) are diagrams showing simulation results implemented in a stop-standby ARQ to analyze the performance of an existing error control scheme and an error control scheme according to the present invention.

 8 (a)-(c) are simulation results showing the relationship between reliability, delay time, and average buffer length, respectively, for a packet error rate in an RLP connection.

[1] G. Fairhurst and L. Wood, “Advice to Link Designers on Link Automatic Repeat reQuest (ARQ),” RFC 3366, Aug. 2002.

[2] Don Towsley and Jack K. Wolf, “On the Statistical Analysis of Queue Lengths and Waiting Times for Statistical Multiplexers with ARQ Retransmission Schemes,” IEEE / ACM Transactions on Networking, vol. com-27, no. 4, Apr. 1979.

[3] Shu Lin, Daniel J. Costello. Jr and Michael J. Miller, “Automatic-Repeat-Request Error Control Schemes,” IEEE Communications Magazine, vol. 22, no. 12, 1984.

[4] Lin, S. and D. Costello, Error Control Coding: Fundamentals and Applications, Prentice Hall, 1993.

[5] Kwang-Sik Kim, Dong-Min Kim, Beum-Joon Kim and Jaiyong Lee, “Improving TCP performance using theadaptive link layer retransmission algorithm over wireless channel,” ICT’2003, Feb. 2003.

[6] William Stallings, High-Speed Networks and Internets, 2nd Ed., Prentice Hall, 2002.

[7] Y. Bai, A. T. Ogielski and Gang Wu, “Interactions of TCP and Radio Link ARQ Protocol,” VTC’99, 1999.

[8] J. Robinson, “Reliable Link Layer Protocols,” RFC 935, Jan. 1985.

Hybrid ARQ (ARQ) using Automatic Retransmit Request (ARQ) and Forward Error Correction (FEC), or both, to ensure the reliability of the wireless link Are considered [1] and [3]. ARQ detects the loss of frames in the link layer and performs a function for retransmission. The lost frame is detected by a retransmission timer or by an acknowledgment (Ack) or polling from the receiver. This enables ARQ to recover lost frames quickly, effectively guaranteeing the reliability of the radio link for higher transport protocols [1]. However, the conventional ARQ has a disadvantage in that it cannot effectively cope with the change of network state because it always uses a fixed number of retransmission allowances. In particular, performing multiple retransmissions when the wireless link is in a congested state will greatly reduce the performance of the link layer. This is a big problem in that the ARQ performance of the link layer seriously affects the overall throughput of the upper layer (eg, TCP throughput) [5]. Therefore, the present specification proposes a dynamic adjustment method of ARQ retransmission allowance considering the number of frames stored in the buffer. The proposed scheme can greatly increase the efficiency of ARQ because it can limit the maximum transmission delay time due to ARQ retransmission and reflect the state of radio link properly.

 The present invention relates to a method and apparatus for dynamically adjusting a retransmission persistence of a transmitting node based on a buffer size and / or a delay time in an ARQ system.

  The ARQ transmission scheme can be largely divided into a stop-and-wait scheme and a sliding window scheme [4].

 Figure 1 (a) is a diagram of a stop-standby ARQ scheme. The pause-wait method transmits only one frame at a time, and then transmits the next frame after confirming that the frame has been successfully delivered. This method has the advantage of being easy to implement, but has the disadvantage of low efficiency because the frame cannot be transmitted until one frame is transmitted and an Ack thereof is received. The sliding window method is very efficient when a sufficiently large transmission window is used as the transmission source manages the transmission window and continuously transmits several frames. On the other hand, since the sequence number must be assigned and managed for each frame, the implementation can be relatively complicated. Representative sliding window methods include GBN (go-back-n) and SR (selective repetition).

FIG. 1 (b) is a diagram illustrating a GBN ARQ scheme. When the transmitter receives a NAK, it returns to the block in which an error occurs and retransmits all subsequent blocks.

FIG. 1 (c) is a diagram illustrating an SR ARQ scheme. When the transmitting side receives a NAK, it finds an error block and retransmits the corresponding block. However, although the transmission efficiency is good, a complicated circuit and a large capacity buffer are compared with other ARQ schemes. It is necessary and the receiver must rearrange the data.

ARQ performance is evaluated by transmission reliability, delay and delay variation, and transmission rate, which are closely related to the size of the frame transmission method and the number of retransmission allowances. Retransmission Persistence refers to the degree to which ARQ attempts retransmission, and is generally defined as a time unit allocated to processing one frame. If the propagation delay of the link is constant, it may be set to the number of retransmissions [1]. The larger the retransmission tolerance, the higher the reliability of the link, while the higher the transmission delay and jitter that a frame suffers from frequent retransmissions. Therefore, in order to satisfy the performance of an efficient link layer, it is important to determine an appropriate number of retransmission allowances.

Depending on the size of the retransmission allowance, the ARQ may be classified into a perfectly repetitive retransmission ARQ, a high repetition re-transmission ARQ, and a low repetition re-transmission ARQ [1], [1]. 2], [3], [6].

Perfectly-persistence ARQ completely guarantees the link reliability by attempting to retransmit the frame indefinitely until the frame transmission is successful [1], [2]. However, because there is no limit on frame retransmission, if the link is in poor condition and frame loss occurs continuously, a large delay and delay variation occur and the maximum transmission delay of the link cannot be limited. In particular, delays and delay variations due to link layer retransmission may affect the performance of higher transport protocols. In the case of TCP, a large delay variation at the link layer can reduce the accuracy of the TCP retransmission timer, and in the worst case, can cause an unnecessary retransmission timeout (RTO), which can drastically reduce the TCP transmission rate. [5] and [7]. In addition, excessive retransmission at the link layer for services that are more sensitive to delay and delay variation than transmission reliability, such as voice and video services, is a factor of degrading service quality [1].

In the case of low-persistence ARQ, the number of retransmission allowances of a frame is usually set to a small value, such as 2 to 5, so that the delay at the link layer is limited to a small value and the effect on the higher transmission protocol is small. We can't guarantee the reliability of a perfectly-persistence ARQ.

Using a fixed number of retransmission allowances is not suitable for Internet networks where the communication environment changes frequently. When the amount of traffic is small, the high link reliability can be ensured by performing multiple retransmissions regardless of the state of the radio link. As the amount of traffic increases, the ARQ's performance changes sensitively with the condition of the radio link.If the link's frame loss rate is low, the ARQ can successfully transmit a frame through one or two retransmissions, while the frame's loss rate In this high case, a large number of retransmissions are required, which leads to a sharp increase in transmission delay and delay variation in the link layer [2]. This is because it takes longer to process one frame, leading to a decrease in the ARQ service rate.

In addition, the amount of data accumulated in the ARQ buffer increases more rapidly, resulting in a vicious cycle that increases the latency of the frame. Using a small number of retransmission allowances can reduce this phenomenon to some extent, which makes it suitable for an ARQ overload condition, but does not provide sufficient link reliability even when the amount of data waiting for transmission in the ARQ sender's buffer is small. Have. In particular, the degradation of throughput due to frame retransmission in the congestion situation of the link increases the congestion condition of the link, which causes the data coming into the node to be lost without being attempted to be transmitted. In a congested state, a lot of data that could not be processed immediately is stored in the node's buffer, and when the limit of the buffer is reached, most of the incoming frames are tail-dropped at the end of the buffer.

Accordingly, there is a need for a method and apparatus that can dynamically adjust the number of such retransmission allowances according to the system environment.

An object of the present invention is to provide a method and apparatus capable of dynamically adjusting the number of retransmission allowances according to a system environment by overcoming the problems of the conventional ARQ scheme using the fixed number of allowable retransmissions.

  According to the present invention, in order to solve the problem of the ARQ scheme using the fixed number of retransmission allowances, an ACK signal is received from the receiving node according to the amount of data accumulated in the ARQ buffer or a data frame inputted into the buffer from the input node of the transmitting node. We propose a method for dynamically setting the number of retransmission allowances of ARQ according to the time until transmission (transmission delay time). That is, when the amount of data waiting for transmission in the buffer of the ARQ transmitter is small, a large number of high-persistence is allowed, and when the amount is large, only a relatively low low-persistence is allowed. In particular, when the amount of data accumulated in the ARQ buffer exceeds the congestion threshold, retransmission is not performed. The amount of traffic imposed on the ARQ is based on the amount of data accumulated in the buffer, and the number of retransmission attempts for one frame is inversely proportional to the amount of data stored in the buffer.

2 is a flowchart illustrating a method of adjusting a number of retransmission allowances according to an embodiment of the present invention.

In Fig. 2, the number of frames in the buffer of the transmitting node is compared with the overflow risk boundary of the buffer, so that if the number of frames in the buffer exceeds the overflow risk boundary, the number of retransmission allowances is reduced; Is taking.

In step 200 a retransmission allowance adjustment mechanism is initiated, which can be initiated automatically at predetermined time intervals or can be done manually as required by the user.

In step 210 the number of frames in the buffer is evaluated and the evaluated result is compared with a predetermined value in step 220. The predetermined value is a value (overflow risk boundary value) set to prevent the overflow of the buffer.

As a result of the comparison, when the number of frames in the buffer exceeds the overflow risk threshold, the number of retransmission allowances is reduced (230), and when the number of the frames in the buffer is less than the overflow risk threshold, the number of retransmission allowances is increased (240). ).

The process then ends at step 250 and the processes resume at step 200 if a predetermined time interval arrives or at the request of a user.

 3 is a flowchart illustrating a method of adjusting a number of retransmission allowances according to another embodiment of the present invention.

In FIG. 3, the delay time (delay time) for a frame input into the buffer of the transmitting node to reach the receiving node successfully is measured or monitored, and if the value exceeds the maximum allowable delay value, the number of retransmission allowances is reduced, otherwise If not, a mechanism to reduce the number of retransmissions is taken.

In step 300 a retransmission allowance adjustment mechanism is initiated, which can be initiated automatically at predetermined time intervals or can be done manually as required by the user.

In step 310 the delay time is evaluated. The evaluation of the delay time can be made in two ways.

The first method is to estimate the delay time based on the number of frames in the buffer.

In the case of the stop-standby ARQ scheme, if the number of frames in the buffer is n, the number of retransmission allowances is p, and the round trip delay between the transmitting node and the receiving node is r, the delay time can be estimated by n * p * r. have.

For SR (Selective Repeat) ARQ schemes, the number of frames in the transmit buffer, the number of frames in the retransmit buffer, the round trip delay between the transmitting node and the receiving node, and the received frame to the uplink (e.g. TCP) The delay time can be estimated by considering all of the resequencing delays that must be waited for delivery.

The second method is to directly measure the delay time by monitoring the delay time of previously transmitted frames.

That is, in order to estimate the maximum delay time of the n-th frame, it is a method of estimating the delay time of the n-th frame based on this value by monitoring the delay time of a frame that has been previously transmitted and received (ACK received). .

The delay time measured in the delay time evaluation step 310 is compared with the maximum allowable delay value in step 320.

The maximum allowable delay value is a value separately defined according to each data type and whether or not it is a real time communication.

For example, the maximum allowable delay value is set small in the case of real-time communication requiring fast signal processing rather than the correct signal processing, and the maximum allowable delay value is set large in the communication in which the accurate signal processing is prior to the prompt signal processing request. Can be.

As a result of the comparison, when the estimated delay time exceeds the maximum allowable delay time, the number of retransmission allowances is decreased (330), and when the estimated delay time is less than the maximum allowable delay time, the number of retransmission allowances is increased (340).

The process then ends at step 350, where the process resumes at step 300 if a predetermined time interval arrives or at the request of a user.

4 is a method for adjusting the number of retransmission allowances according to another embodiment of the present invention, which combines the methods shown in FIGS. 2 and 3.

 In step 400 a retransmission allowance adjustment mechanism is initiated, which can be initiated automatically at predetermined time intervals or can be done manually as required by the user.

In step 410 the number of frames in the buffer is evaluated, and the evaluated result is compared with a predetermined value in step 420. The predetermined value is a value (overflow risk threshold value) set to prevent the overflow of the buffer.

As a result of the comparison, if the number of frames in the buffer exceeds the overflow risk threshold, the number of retransmission allowances is reduced (430), and the process ends in step 480. If the result of the comparison is that the number of frames in the buffer is below the overflow risk threshold, the delay time is estimated at step 440, and the estimated delay value is compared with the maximum allowable delay value at step 450.

If the estimated delay value exceeds the maximum allowable delay value, the number of retransmission allowances is decreased in step 460. If the estimated delay value is less than the maximum allowable delay value, the number of retransmission allowances is increased in step 470.

 The process then ends at step 480 and the process resumes at step 400 if a predetermined time interval arrives or at the request of a user.

5 is a diagram illustrating an example of adjusting the number of retransmission allowances in a stop-standby ARQ system according to an embodiment of the present invention.

In FIG. 5, the size of the buffer is set to N, the maximum retransmission allowance is set to K, and the overflow risk threshold is set to 2 / N.

The number of retransmission allowances is dynamically adjusted according to the number of frames in the buffer. For example, when the number of frames in the buffer is between N / 3 and N / 2, the number of retransmission allowances is set to two.

6 is a diagram illustrating a configuration of a transmitting node having an apparatus for adjusting the number of retransmission allowances according to an embodiment of the present invention.

6 includes a transmission buffer 600, a retransmission number management unit 630, and a transmitter 690.

The transmit buffer 600 includes a transmit buffer 610 and a retransmission buffer 620.

The retransmission buffer 620 may be omitted in stationary and standby ARQ systems, while it will be appreciated by those skilled in the art that in a selective repetitive ARQ system, frames in the retransmission buffer are transmitted preferentially over frames in the transmit buffer.

The retransmission allowance number management unit 630 includes a frame number calculation unit 640, a delay time calculation unit 650, a first comparator 660, a second comparator 670, and a controller 680.

The frame number calculation unit 640 counts the number of frames in the transmission and retransmission buffers in the buffer, and provides the counted result to the first comparator 660 and the delay calculation unit 650.

The first comparator compares the counted result with the first threshold (overflow risk threshold) and provides the result to the controller 680.

The delay calculation unit 650 calculates a delay time estimate based on the number of frames received from the frame number calculation unit 680 and provides it to the second comparator 670. The second comparator compares the delay time estimate with a second threshold (maximum allowable delay time) and provides the result to the controller 680.

The controller 680 provides an adjustment signal to the buffer 600 and / or the transmitter 680 to adjust the retransmission allowable repetition number based on the first comparison result value and the second comparison result value.

The controller generates a control signal to reduce the number of retransmissions when the first comparison result exceeds the first threshold value, and adjusts the number of retransmissions according to the second comparison result value when the first comparison result value is less than the first threshold value. do.

In FIG. 6, the delay calculation unit 650 is determined based on the number of frames in the buffer, but in another embodiment the delay calculation unit is not the number of frames in the buffer, but rather the actual delay time of the previously transmitted frame. It is also possible to estimate the delay time by monitoring the time from the input time to the buffer input end until receiving the ACK signal from the receiving node.

7 (a)-(c) are diagrams showing the result values simulated in stop-and-wait ARQ to analyze the performance of the existing error control scheme and the proposed scheme. The number of retransmission allowances did not limit the size for perfectly-persistence ARQ, and low-persistence ARQ was set to 2 to perform two retransmissions. The retransmission allowance size of the proposed scheme is set as shown in FIG. In the simulation environment, it is assumed that the frame throughput is 2Mbps, and the time required to transmit one frame normally and receive an Ack from the receiver is 2ms. Loss of frames can only be detected through the time-out of the sender's timer. At this time, the size of the timer is set to twice the frame transmission RTT. The buffer size of the source and the congestion boundary of the proposed scheme are set to 1024 kbytes and 512 kbytes, respectively, and it is assumed that the frames are randomly lost in the radio link. Traffic to the source is generated by the Poisson model and the frame size is set to 512 bytes. The traffic load (offered load) is defined as the ratio of traffic entering the source to the frame rate of the source and simulated by varying the traffic load. Since the proposed scheme has a relatively large number of retransmission allowances when the traffic load is small, when the frame loss rate of the radio link is less than 0.1, the performance is close to perfectly-persistence ARQ in terms of transmission reliability.

As shown in Fig. 7 (a), the average delay time is the same when the frame loss rate is very low (0.01), and when the frame loss rate is 0.1, the higher the amount of traffic charged to the transmitter, the lower the low-persistence and perfectly-persistence. The result was smaller. This is because as the amount of traffic added to the sender increases and the amount of data accumulated in the sender's buffer increases, the number of retransmission allowances is set to a small value, which allows only fewer frame retransmissions than the fixed retransmission allowance method. to be. Fig. 7 (b) shows the average delay time of the three error control schemes when the frame loss rate of the radio link is very high as 0.5. Both schemes, which use a fixed number of retransmission allowances, dramatically degrade performance in terms of transmission delay and stability even when the traffic load is relatively small. That is, since an average of two or more transmissions is required to successfully deliver one frame, the transmission delay increases very rapidly and easily becomes congested (ie, buffer overflow). On the other hand, when the traffic load is less than 0.4, the proposed method maintains the number of retransmission allowances higher than the low-persistence, providing reliability close to perfectly-persistence, and the transmission delay is not more than several times the link transmission delay (RTT). As the traffic load increases from 0.4 to 0.6, we can reduce the transmission delay by 50% of the low-persistence ARQ by performing only one retransmission by reducing the number of retransmission allowances.

Figure 7 (c) shows that in the proposed scheme, congestion occurs when the traffic load is more than 0.7, and it can operate stably under the traffic load 0.4-0.7 compared to using the fixed number of retransmission allowances.

Table 1 shows the performance (reliability) of the three schemes according to the frame loss rate of the radio link when the traffic load is constant at 0.8. If the frame loss rate is less than 0.1, the proposed scheme maintains a relatively high number of retransmission allowances and 100% reliability for perfectly-persistence ARQ, while low-persistence gives up the retransmission when the frame loss rate is high. Increases. In the case of using a fixed number of retransmission allowances, it can be seen that when the frame loss rate of the radio link increases, the actual number of retransmissions increases, leading to a decrease in the frame rate of the transmitter, thereby easily entering a congestion state. The proposed scheme decreases the number of retransmission allowances and increases the frequency of abandoning retransmissions, but can operate more stably even when the radio link is unstable.

Table 1 (Frame Loss Comparison)

 0.8 provided, total number of frames reached = 230335

Frame loss rate Perfectly retransmitted Low repetition low Dynamic retransmission allowance adjustment method according to the present invention Loss Loss Abandonment Loss Abandonment 0.01 0 0 One 0 0 0.02 0 0 One 0 0 0.03 0 0 5 0 0 0.04 0 0 15 0 0 0.05 0 0 24 0 0 0.06 0 0 48 0 0 0.07 0 0 79 0 0 0.08 0 0 119 0 0 0.09 0 0 179 0 0 0.1 0 0 227 0 0 0.2  confusion  confusion 0 39326 0.3  confusion 0.4 0.5

8 (a)-(c) are simulation results showing the relationship between the reliability, the delay time, and the average buffer length for the packet error rate in the RLP connection.

Here, RLP-Original is a simulation result applied when the number of retransmissions is set to 1 without using the reverse arc method, and RLP-RA-1, RLP-RA-3, and RLP-RA 10 are reverse directions. It is simulation result applied to fixed repetition number method that adopts Ack method and fixed retransmission number to 1, 3 and 10, respectively, and RLP-RA-RPM is a dynamic retransmission allowance adjustment method according to the present invention. This is the simulation result value applied when using Management).

As can be seen in Figure 8 (a), the RPM (retransmission number management) method according to the present invention shows almost the same level of reliability compared to the conventional method using a high number of retransmissions (10), low number of retransmissions ( It can be seen that the reliability is superior to the conventional method using 1 or 3).

In addition, as can be seen in Figure 8 (b), the RPM method according to the present invention has almost the same level of delay time compared to the conventional method using a low number of retransmissions (1 or 3), the high number of retransmissions ( Compared to the existing method using 10), it has a very short delay time.

In addition, as can be seen in Figure 8 (c), the RPM method according to the present invention has a waiting buffer length of approximately the same level as the conventional method using a low number of retransmissions (1 or 3), and a high number of retransmissions Compared to the conventional method using (10), it can be seen that it has a very small waiting buffer length.

Accordingly, it can be seen that the RPM method according to the present invention exhibits superior performance in comparison with the conventional fixed retransmission method in terms of reliability, latency, and buffer length.

The various illustrative logic blocks, modules, and circuits described above are general purpose processors; Digital signal processing (DSP); Application specific integrated circuits (ASIC); Field programmable gate array (FPGA); Or another programmable logic device; Discrete gate or transistor logic; Discrete hardware components; Or through a combination of those designed to implement these functions. A general purpose processor may be a microprocessor; In alternative embodiments, such a processor may be an existing processor, controller, microcontroller, or state machine. A processor may be implemented as a combination of computing devices, such as, for example, a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or a combination of these configurations.

 The steps and algorithms of the method described above can be implemented directly in hardware, in a software module executed by a processor, or by a combination thereof. Software modules include random access memory (RAM); Flash memory; Read-only memory (ROM); Electrically programmable ROM (EPROM); Electrically erasable programmable ROM (EEPROM); register; Hard disk; Removable disks; Compact disc ROM (CD-ROM); Or in any form of known storage media. An exemplary storage medium is coupled to the processor, which reads information from and writes the information to the storage medium. In the alternative, the storage medium may be integral to the processor. Such processors and storage media may reside in an ASIC. The ASIC may be located in the user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

  On the other hand, the above embodiments are presented as examples for those skilled in the art to more easily understand the present invention, but the present invention is not limited to the above embodiments.

 Therefore, the scope of the present invention should be construed to include not only the above-described embodiments but also various modifications of the above-described embodiments.

The dynamic retransmission adjustment method according to the present invention dynamically adjusts the retransmission number according to the buffer capacity and / or the delay time, thereby providing improved performance in terms of reliability and latency compared to the conventional method using the fixed retransmission count. do.

Claims (26)

A method for dynamically adjusting the retransmission allowance in an automatic retransmission request (ARQ) system. Measuring the number of frames in the standby buffer of the transmitting node; And And adjusting the number of retransmission allowances according to the number of frames in the standby buffer of the transmitting node. The method of claim 1, wherein the retransmission allowance adjustment step Comparing the number of frames in the standby buffer of the transmitting node with a predetermined threshold value; If the number of frames in the standby buffer of the transmitting node exceeds the threshold as a result of the comparison, the number of retransmission allowances is decreased, and if the number of frames in the standby buffer of the transmitting node is less than the threshold, the number of retransmission allowance is increased. And adjusting the number of retransmissions allowed by the automatic retransmission request system. The method according to claim 1 or 2, Evaluating the transmission delay of the input frame: Comparing the estimated transmission delay value with the maximum allowable delay value; And Reducing the number of retransmission allowances when the transmission delay value exceeds the maximum allowable delay value; and increasing the number of retransmission allowances when the transmission delay value is less than the maximum allowable delay value as a result of the comparison. How to adjust the number of retransmissions allowed. The method of claim 3, In the evaluation of the transmission delay, the transmission delay value depends on the number n of frames in the wait buffer, the number of retransmission allowances, and the round trip delay time r. How to adjust the number of retransmissions allowed by the requesting system. The method of claim 4, wherein The transmission delay value is determined by the number of frames (n) in the buffer, the number of retransmission allowances (p), and the multiplication value (n * p * r) of the transmission round trip delay time. Adjustment method.  3. The method of claim 2, wherein the threshold value is a buffer overflow risk boundary value.  The method of claim 3, The maximum allowable delay value is changed according to the type of data to be transmitted or whether the transmitted data is real-time data. The method according to claim 1 or 2, The automatic retransmission request (ARQ) system is a Stop-N-Wait ARQ (Stop-N-Wait ARQ) system, characterized in that the automatic retransmission request system adjustment method for retransmission allowance. A method of dynamically adjusting the number of retransmissions allowed in a sliding window ARQ system,  Measuring the number of frames in the transmit wait buffer of the transmitting node; Measuring the number of frames in the retransmission wait buffer of the transmitting node; And And adjusting the number of retransmission allowances according to the number of frames in the transmission wait buffer and the number of frames in the retransmission wait buffer. 10. The method of claim 9, wherein the retransmission allowance adjustment step Comparing a number of frames in the transmission wait buffer with a predetermined threshold value; And reducing the number of retransmission allowances when the number of frames in the transmission wait buffer exceeds the threshold as a result of the comparison. The method of claim 9 or 10,  Evaluating the transmission delay of the input frame: Comparing the estimated transmission delay value with the maximum allowable delay value; And The retransmission request system further comprises the step of reducing the number of retransmissions allowed when the transmission delay value exceeds the maximum allowable delay value, and increasing the number of retransmission allowances when the maximum transmission delay value is less than the maximum allowable delay value as a result of the comparison. How to adjust the number of retransmissions allowed.  The method of claim 11, In the step of evaluating the transmission delay, the transmission delay value is dependent on the number of frames in the transmission waiting buffer, the number of frames in the retransmission waiting buffer and the round trip delay time. The method of claim 12, And the number of frames in the retransmission waiting buffer depends on the number of retransmission allowances and the frame error rate.  The method of claim 12, The transmission delay value is a method of adjusting the retransmission allowance number of the automatic retransmission request system, characterized in that further dependent on the resequencing delay time.   The method of claim 9 or 10, And the automatic retransmission request system is a selective repeat ARQ (selective repeat ARQ) system.  The method of claim 11, The maximum allowable delay value is changed according to the type of data to be transmitted or whether the transmitted data is real-time data.  A method for dynamically adjusting the retransmission allowance in an automatic retransmission request (ARQ) system. Measuring an input time of a frame input to a transmission buffer of a transmitting node; Measuring a time for receiving an ACK for the input frame from a receiving node; Calculating a time (delay time) between the input time and the ACK reception time; Comparing the delay time with a maximum allowable delay time; And adjusting the number of retransmission allowances according to the comparison result. The method of claim 17, The adjusting step may reduce the number of retransmission allowances when the delay time exceeds the maximum allowable delay time, and increase the number of retransmission allowances when the delay time is less than the maximum allowable delay time. How to adjust the number of retransmissions allowed. An apparatus for dynamically adjusting the number of retransmissions allowed in an automatic retransmission request (ARQ) system, A transmission wait buffer which sequentially stores frames to be transmitted; And a retransmission allowance number management unit that adjusts the number of retransmission allowances according to the number of frames in the transmission wait buffer. The method of claim 19, The retransmission allowance number adjustment unit A measuring device for measuring the number of frames in the transmission wait buffer; A first comparator for comparing the number of frames in the transmit buffer with a predetermined first threshold; A calculating unit for calculating a transmission delay time; And And a second comparator for comparing a transmission delay time with a second predetermined threshold. The method of claim 20, The first threshold corresponds to a maximum number of frame allowances in the buffer set to prevent overflow of the buffer, And the second threshold corresponds to a maximum allowable delay time. The method of claim 20 or 21, The retransmission allowance number management unit If the number of frames in the transmission buffer exceeds the first threshold, the number of retransmission allowances is decreased, And a controller for adjusting the number of retransmission allowances according to a second comparison result when the number of frames in the buffer is less than the first threshold. The method of claim 22, wherein the controller As a result of the second comparison, when the transmission delay time exceeds the second threshold, the number of retransmission allowances is decreased, and when the transmission delay time is less than the second threshold, the number of retransmission allowances is increased. Adjustment device. The method of claim 20 or 21, And a retransmission allowance adjusting device further including a retransmission buffer for retransmitting lost frames for retransmission of lost frames. A device for dynamically adjusting the retransmission allowance in an automatic retransmission request (ARQ) system.  An apparatus for measuring a time interval between an input time of a frame input to a transmitting buffer of a transmitting node and a time of receiving an ACK for the input frame from a receiving node; A comparator for comparing the time interval with a maximum allowable delay time; And a controller for adjusting the number of retransmission allowances according to the comparison result. The method of claim 25, The controller may be configured to reduce the number of retransmission allowances when the time interval exceeds the maximum allowable delay time, and to increase the number of retransmission allowances when the time interval is less than the maximum allowable delay time. A device for adjusting the number of retransmissions allowed by the requesting system.

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