WO2006069534A1

WO2006069534A1 - A method for adjusting the size of the transmission buffer of rlc sub-layer

Info

Publication number: WO2006069534A1
Application number: PCT/CN2005/002336
Authority: WO
Inventors: Zhenghua Tang; Weifeng Shen; Hua Zhang; Hua Qiu; Zhiyuan Chu
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2004-12-28
Filing date: 2005-12-28
Publication date: 2006-07-06
Also published as: CN1798085A; CN100421413C

Abstract

A method for adjusting the size of the transmission buffer of RLC sub-layer comprises: detecting the transmission delay of the air interface of the wireless communication network, and adjusting the size of the transmission buffer of RLC sub-layer according to the transmission delay of the air interface. The present invention can adjust the space of the transmission buffer of RLC sub-layer dynamically and feasibly according to the transmission delay of the air interface. The phenomenon of the decline of the data throughput of the air interface and the judder due to the transmission buffer set too small is avoided. On the other hand, the phenomenon of the waste of the memory resource in RLC sub-layer and the data transmission delay by added factitiously due to the transmission buffer set too big is avoided. It makes the present invention to save the memory resource in RLC sub-layer and improve the data transmission rate while ensuring sufficiently the throughput of the air interface in order to save the communication system resource and improve the communication system performance.

Description

The present invention relates to the field of network communication technologies, and in particular, to a method for adjusting a transmission buffer size of a radio link control sublayer.

Background technique

In UTRAN (Universal Terrestrial Radio Access Network), in order to ensure reliable data transmission, the RLC (Radio Link Control) sublayer often uses AM (Acknowledged Mode) for data transmission. As shown in Figure 1.

In Figure 1, the upper layer transmits the PDU (Protocol Data Unit) to its corresponding transmitting entity.

A PDU may be referred to as an SDU (Service Data Unit) for a transmitting entity. The transmitting entity assembles the PDUs transmitted by the upper layer into AMD (Acknowledgment Mode Data) PDUs, and then stores them in a transmission buffer such as a transmission buffer, and then transmits them to the corresponding receiving entity through the underlying wireless channel. After receiving the status report of the correct reception transmitted by the receiving end, the sending entity deletes the corresponding stored AMD PDU in the sending buffer according to the information carried in the status report.

Due to the large delay of the air interface transmission of the wireless network and the high bit error rate, when the data transmitted by the transmitting entity cannot be confirmed by the receiving entity in time, the new data packet transmitted by the upper layer can only be stored in the RLC sublayer of the transmitting entity. In the cache. If the application layer uses the TCP protocol, according to the slow start mechanism of TCP: During the exponential growth of TCP transmission data, the amount of data received by the RLC sublayer from the upper layer is greater than its own transmission capability, which also causes more data to stay in the RLC sub. The layer is sent in the cache. When the TCP transmission data grows linearly, TCP can only send one segment for each acknowledgement. At this time, the RLC sublayer receives the data rate from the upper layer and the RLC sublayer transmission rate is basically the same, so that the RLC sublayer sends the buffer. Always keep a certain amount of data.

It is very important to set the size of the RLC sublayer send buffer reasonably. The RLC sublayer transmit buffer setting is too small. When the wireless network air interface transmission delay is large, the air interface throughput rate is reduced and jittered. If the RLC sublayer transmit buffer setting is too large, the RLC memory resources are wasted, which is more important. The transmission buffer setting is too large, and the throughput of the air interface is not improved. Since the data of the application layer temporarily exists in the RLC sublayer for 2 transmissions, the data is artificially increased. 6

-2- Transmission delay.

The relationship between the simulated RLC sublayer transmit buffer size and the air interface data throughput rate and data transmission delay is shown in Figure 2.

In Figure 2, the horizontal axis is the RLC sublayer transmit buffer size, the left vertical axis is the air interface data throughput rate, and the right vertical axis is the packet transmission delay. From the lower curve of the two curves in the figure, when the allocation rate is 384k bits and the RLC sublayer transmission buffer is larger than 48k bits, the data transmission delay will rise sharply, but the air interface data throughput rate is not too large. Improvement.

At the same time, when the RLC sub-layer sending buffer setting is too large, if the network or user needs to immediately stop the current service or initiate a new service request, the RLC sub-layer sends a buffered FIFO (First In First Out) mechanism. Causes a stop request or a new business request to be unresponsive.

Currently, the control method for the size of the RLC sub-layer transmission buffer is mainly as follows: According to the protocol of the 3GPP (3rd Generation Partnership Project), the RLC sub-layer can configure the discarding time of the timeout, that is, if the RLC sub- If the data stored in the layer sending buffer exceeds the discarding time and has not been sent yet, the data is discarded. Therefore, the RLC sublayer sending buffer is not set too large by the discarding time control.

However, since the discard time is a static value defined by the protocol and must be specified when the service is established, the amount of data stored in the RLC sublayer transmit buffer is closely related to the radio network air interface transmission delay, if one is used The static value is used to set the size of the RLC sub-layer send buffer. The air interface data throughput rate drops, jitter or waste of memory resources, and artificially increased data transmission delay.

In summary, the existing control method of the RLC sublayer transmission buffer size cannot reasonably adjust the size of the RLC sublayer transmission buffer, and has the disadvantages that the communication system resources cannot be effectively saved, and the performance of the communication system cannot be effectively improved.

Summary of the invention

An object of the present invention is to provide a method for adjusting a transmission buffer size of a radio link control sublayer, and dynamically and reasonably adjust a radio link control sublayer transmission buffer size according to an air interface transmission delay to save communication system resources. Improve communication system performance. To achieve the above objective, the method for adjusting a transmission buffer size of a radio link control sublayer provided by the present invention includes:

a. detecting an air interface transmission delay of the wireless communication network;

b. Adjusting the size of the radio link control sublayer transmission buffer according to the air interface transmission delay.

among them:

The radio link control sublayer transmitting entity determines the air interface transmission delay based on the loopback time of the data.

The loopback time average of the data of the predetermined number of data by the transmitting entity determines the air interface transmission delay.

The loopback time of the data is: the time when the sending entity receives the data of the corresponding upper layer transmission and the state that the sending entity receives the data transmitted by the peer end that has been correctly received by the peer end. Time difference.

The data includes: a service data unit.

The average value of the loopback time is determined by the following method:

The sending entity records the time of receiving the service data unit transmitted by its corresponding upper layer;

The sending entity determines, according to the information reported by the peer end, the service data unit that has been completely and correctly received by the opposite end, and records the time when the corresponding status report is received; the sending entity determines the predetermined number of services. When the data unit has been completely and correctly received by the opposite end, the average loopback time of the service data unit is determined according to the recording time corresponding to each of the service data units and the predetermined number.

The method further includes:

Obtaining a maximum rate of service between the sending entity and an upper layer thereof;

The size of the radio link control sublayer transmit buffer is adjusted according to the product of the maximum rate of the service and the air interface transmission delay.

Or, set the delay scale factor;

The size of the radio link control sublayer transmission buffer is adjusted according to the product of the maximum rate of service, the delay ratio factor, and the air interface transmission delay. According to the description of the foregoing technical solution, the present invention dynamically adjusts the size of the radio link control sublayer transmission buffer according to the air interface transmission delay. When the air interface transmission delay is large, the radio link control sublayer transmission buffer can be correspondingly increased. The space avoids the air interface throughput rate drop and jitter caused by the transmission buffer setting being too small. When the air interface transmission delay is small, the transmission buffer space can be reduced correspondingly, and the wireless transmission caused by the excessive transmission buffer setting is avoided. Link control sub-layer memory resource waste, artificially increase data transmission delay phenomenon; method for determining air interface transmission delay by loopback time of service data unit that has been completely and correctly received, so as to detect air interface transmission delay It is easy to implement; the size of the sending buffer is determined according to the maximum rate of service transmitted to the sending entity by the upper layer, the delay scale factor, and the average loopback time, so that the size of the sending buffer is reasonably set, so that the present invention ensures the air interface data. At the same time, the radio link control is avoided Layer waste memory resources, data transmission phenomenon of artificially increasing the delay; thereby achieving the purpose of saving radio link control sub-layer memory resources, to improve the performance of the communication system by the technical solution provided by the invention.

DRAWINGS

1 is a schematic diagram of the prior art RLC AM mode operation;

2 is a schematic diagram showing the relationship between the size of the simulated RLC sublayer transmit buffer and the air interface data throughput rate and data transmission delay;

Fig. 3 is a flow chart showing a method of controlling the transmission buffer size of the radio link control in the embodiment of the present invention.

detailed description

The air interface transmission delay of the wireless network generally changes with the error, transmission bearer and other factors. Since the radio link control sublayer transmission buffer is extended on the air interface of the wireless network, a large amount of storage is stored. Data, when the air interface transmission delay of the wireless network is small, the stored data is correspondingly reduced. Then, if the size of the radio link control sublayer transmission buffer is adjusted according to the air interface transmission delay, the air interface can be effectively avoided. Data throughput rate drops, jitter, waste of wireless link control sub-layer memory resources, and artificially increased data transmission delay. Therefore, the present invention adjusts the size of the radio link control sublayer transmission buffer according to the air interface transmission delay by detecting the air interface transmission delay of the wireless network.

The technical solutions provided by the present invention are further described below. The detection of the air interface transmission delay of the present invention can be determined by acquiring the data loopback time, and the data loopback time can be obtained by the sending entity receiving the data transmitted by the upper layer and the transmitting entity receiving the data transmitted by the peer end has been correctly The difference in the time of the received status report is determined.

In order to avoid sudden fluctuations in the transmission delay of the air interface and to frequently adjust the size of the transmission buffer, the present invention uses an average of a predetermined number of data loopback times to determine the air interface transmission delay of the wireless network over a period of time.

The method of the present invention will now be described by taking the data loopback time of a Service Data Unit (SDU) as an example.

The receiving entity records the time when the SDU is received when receiving the SDU transmitted by the upper layer, and the transmitting entity records the time when the receiving status report is received when receiving the receiving status report transmitted by the opposite end.

The sending entity determines whether a complete SDU is correctly received by the opposite end according to the information carried in the receiving status report, such as the serial number. If a complete SDU is correctly received by the opposite end, the sending entity may correct according to the record. The difference between the two times of the received SDU obtains the correctly received SDU loopback time. The present invention can determine the air interface transmission delay based on a predetermined number of averages of the SDU loopback times that are correctly and correctly received by the peer. The predetermined number can be determined by the actual situation of the communication system.

After determining the air interface transmission delay, a corresponding predetermined value may be uniquely determined according to the air interface transmission delay, where the predetermined value is the size of the transmission buffer in the RLC sublayer sending entity, and the transmission buffer is buffered according to the predetermined value. Size is adjusted.

The method for uniquely determining a corresponding predetermined value according to the air interface transmission delay may be: determining the maximum rate of service between the upper layer and the transmitting entity of the sending entity, and transmitting data to the upper layer

The RLC sublayer sends the maximum rate of the service of the entity, multiplies the maximum rate of the service by the air interface transmission delay, and the obtained value can be used as the size of the sending buffer of the sending entity, and the size of the sending buffer is adjusted according to the value.

Considering the data transmission delay of the wired network, the present invention can also set a delay scale factor, multiply the service maximum rate and the delay scale factor by the air interface transmission delay, and obtain the value as the size of the sending cache of the sending entity. Adjust the RLC sublayer send buffer according to the value Size.

The present invention can adjust the size of the RLC sublayer transmission buffer each time a predetermined number of SDUs that are correctly received by the opposite end are determined, so that the storage space of the RLC sublayer transmission buffer can be based on the air in a period of time. The interface transmission delay is dynamically and reasonably set. On the one hand, the air interface throughput rate drop and jitter caused by the RLC sublayer transmission buffer setting being too small are avoided, and on the other hand, the RLC sublayer transmission buffer setting is prevented from being too large. The wireless link controls the waste of memory resources in the sub-layer and artificially increases the delay of data transmission.

The method for adjusting the size of the RLC sublayer transmission buffer of the present invention will be described in detail below with reference to FIG.

In FIG. 3, step 300, setting a delay scale factor Factor, obtaining a service maximum rate MaxRate transmitted by the upper layer to the sending entity and a predetermined number of WindowSize ₀ starting from a predetermined number of counts, if using a counter, the predetermined number The counter is reset, and the initial value of the counter is set to a predetermined number.

Go to step 310, when the RLC sublayer receives the SDU transmitted by the upper layer, record the current time, that is, ReceiveTime(m), where m represents the mth SDU received by the RLC sublayer sending entity.

The RLC sublayer assembles the SDU into an AMD PDU and transmits it to the RLC sublayer receiving entity of the opposite end through the underlying protocol according to the protocol operation steps. When the RLC sublayer sending entity receives the receiving status report transmitted by the peer receiving entity, to step 320, according to the information carried in the receiving status report, such as sn (serial number), it is determined whether a complete SDU is received by the opposite end. If there is no complete SDU received correctly by the opposite end, the receiving status report received by the RLC sublayer transmitting entity is continuously judged until it is determined that a complete SDU is correctly received by the opposite end.

Go to step 330, the RLC sublayer sending entity records the time when the sequence number is n received status report, that is, ConfirmTime (n), where n indicates that the RLC sublayer transmitting entity receives the nth complete correct reception received by the peer end. status report.

Go to step 340, the RLC sub-layer sending entity determines that the ConfirmTime (n) corresponds to the SDU, and then determines that the sending entity receives the time when the upper layer transmits the SDU, sets it to ReceiveTime(n), and calculates the time difference Delta (n) of the two. :

Delta ( n ) = ConfirmTime ( n ) - ReceiveTime ( n )

At the same time, the value of the counter is reduced by one. Go to step 350 to determine whether the count value of the counter is 0. If the count value is not 0, continue to judge the count value until the count value is 0, and go to step 360 to calculate the average loopback time of the predetermined number of SDUs. AverageTime , ie:

1 WindowSize

AverageTime = ( Confirm Time[n ] - Re ceiveTime[n])

WindowSize ~[ to step 370, calculate the predetermined value MaxBuffer, ie

MaxBuffer = MaxRate x Factor x AverageTime, and adjust the size of the RLC sublayer sending entity's send buffer according to MaxBuffer. The counter is reset and restarts for a predetermined number of counts. Go to step 320, and continue to judge the reception status report received by the RLC sublayer sending entity, and start the next RLC sublayer transmission buffer size adjustment process.

While the invention has been described by the embodiments of the invention, it will be understood that

Claims

Rights request

A method for adjusting a size of a transmission buffer of a radio link control sublayer, which is characterized by comprising:

Adjusting the wireless link control sublayer transmission buffer according to the air interface transmission delay

2. The method for adjusting a size of a transmission buffer of a radio link control sublayer according to claim 1, wherein:

3. The method for adjusting a size of a transmission buffer of a radio link control sublayer according to claim 2, wherein:

The transmitting entity determines an air interface transmission delay based on a loopback time average of a predetermined number of data.

The method for adjusting the size of the transmission buffer of the radio link control sublayer according to claim 2 or 3, wherein the loopback time of the data is: the sending entity receives the corresponding upper layer transmission The time of the incoming data and the time difference of the status report that the transmitting entity receives the data transmitted by the peer end that has been correctly received by the opposite end.

5. The method for adjusting a size of a radio link control sublayer transmission buffer according to claim 4, wherein the data comprises: a service data unit.

6. The method for adjusting a size of a radio link control sublayer transmission buffer according to claim 5, wherein the average value of the loopback time is determined by the following method:

The method for adjusting the size of the transmission buffer of the radio link control sublayer according to claim 6, wherein the method further includes:

The method for adjusting the size of the transmission buffer of the radio link control sublayer according to claim 7, wherein the method further includes:

Set the delay scale factor;

The size of the radio link control sublayer transmit buffer is adjusted according to the product of the maximum rate of the service, the delay scale factor, and the air interface transmission delay.

The method for adjusting a size of a transmission buffer of a radio link control sublayer according to claim 1, 2 or 3, wherein the method further comprises:

The method of claim 9, wherein the method further comprises:

Set the delay scale factor;

The size of the radio link control sublayer transmission buffer is adjusted according to the product of the maximum rate of service, the delay ratio factor and the air interface transmission delay.