KR20050066301A - A method for controlling acceptance of traffic stream in wireless lan system and computer-readable medium including the program thereof - Google Patents

Abstract

The present invention relates to a traffic stream admission control method in IEEE 802.11e in consideration of available service bandwidth and service requirements of a new traffic stream.

According to the configuration of the present invention, the currently requested service rate is calculated based on a predetermined maximum data rate PRi, a transmission delay time limit DBi, and a maximum burst size Li from the traffic stream addition message. Accept the traffic stream if the service rate is less than the redundant service rate. If the traffic stream is accepted, the extra service rate is subtracted by the required service rate.

Therefore, according to the configuration of the present invention, efficient traffic stream admission control can be performed in consideration of both the total service rate currently available and the service rate required in the traffic stream addition message.

Description

A method for controlling acceptance of traffic stream in wireless LAN system and computer-readable medium including the program

The present invention relates to a traffic stream admission control method in IEEE 802.11e in consideration of available service bandwidth and service requirements of a new traffic stream.

IEEE 802.11e defines a Quality of Service (QoS) mechanism for wireless devices that support bandwidth-sensitive applications such as voice and video.

The early IEEE 802.11 Media Access Control (MAC) protocol was designed based on the Distributed Coordination Function (DCF) using carrier sensing for collision avoidance. The DCF could perform a coordination function by detecting a collision by waiting a predetermined time before transmitting data. However, the DCF did not provide any priority for access of the wireless medium.

Therefore, another option, Point Coordination Function (PCF), is provided to allow selective use of time-limited non-competitive frame forwarding in the MAC layer. In the PCF mode of operation, a point coordinator resides in an access point (AP) to control frame transmission from stations. Thus, all stations are under the control of the point coordinator by setting their Network Allocation Vector (NAV) values at the beginning of each non-competitive transmission period. In addition, stations may optionally respond to a contention-free poll (CF poll) frame.

However, since the DCF and the PCF cannot differentiate traffic types, the IEEE has proposed an improved scheme for improving the QoS of the two modes in the 802.11e standard.

The new channel access method proposed by the IEEE is a hybrid coordination function (HCF) and an enhanced DCF (EDCF), which use a contention-based access method and a polling method together.

EDCF complements the existing DCF and is a method for differentiating services by traffic category by differentiating IFD (Inter Frame Space) and initial competition window (CWmin) for each of four traffic categories.

The HCF polling method defines the service level for each traffic category using the traffic specification element, and based on this, polling for each station is performed according to the HC (Hybrid Coordination) defined level. In addition, for services that are sensitive to time delays such as voice, the ACK frame may not be transmitted to make it more suitable for real-time services.

Meanwhile, according to the HCF protocol, for the traffic stream transmission service between a station and an access point, an access point receives a traffic stream addition message from the station and transmits a response message to the station.

At this time, the access point receiving the traffic stream addition message from the station should decide whether or not to allow the traffic stream requested by the station to its basic service set (BSS), and notify the station of the decision as a response message. .

Meanwhile, in order to efficiently perform such traffic stream admission control, a traffic stream admission control algorithm considering the service requirements of the new traffic stream and the currently available service bandwidth is required. However, the current IEEE 802.11e standard does not propose an admission control scheme considering the available service bandwidth and the service requirements of the new traffic stream in the wireless LAN system.

Accordingly, the present invention provides a traffic stream admission control method in consideration of the current available service bandwidth in the BSS and the service requirements of the new traffic stream in the IEEE 802.11e WLAN system in order to solve the problems of the prior art.

In order to solve the above technical problem of the present invention, a traffic stream control method according to a feature of the present invention,

Initializing the total available service rate to an extra service rate;

Waiting to receive a traffic stream addition message or a traffic stream deletion message;

When the traffic stream addition message is received, a service rate currently required is calculated based on a predetermined maximum transmission rate PRi, a transmission delay time limit DBi, and a maximum burst size Li included in the traffic stream addition message. Doing;

Comparing the service rate with the redundant service rate to determine whether to accept a traffic stream; And

And if accepting the traffic stream, subtracting the calculated service rate from the redundant service rate to update the redundant service rate.

In addition, the traffic stream admission control method of the present invention comprises the steps of: receiving a traffic stream deletion message, and adding the service rate of the traffic stream corresponding to the traffic stream addition message to the extra service rate to obtain the extra service rate. The method further includes the step of updating.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

Now, a traffic stream method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a timing diagram illustrating the arrival time of a traffic stream in accordance with an embodiment of the present invention.

As shown in Fig. 1, in the present invention, the traffic stream TSi is modeled as continuously arriving at a constant interval Di (seconds). In FIG. 1, Li (bits) and Pi (seconds) represent the magnitude of the burst and the length of the burst interval, respectively, and one burst is composed of several MAC Protocol Data Units (MPDUs).

In general, the burst size Li and the burst duration length Pi are variable, and as Li and Pi increase, the quality of service of the transmission delay time of the traffic stream is worse. In the present invention, the worst case transmission delay time is to satisfy the quality of service of the traffic stream by always lowering the transmission delay time limit DBi defined in the traffic stream addition message transmitted from the station.

To this end, if the burst size Li is defined as the maximum burst size defined in the traffic stream addition message, the length Pi of the burst period may be defined as in Equation 1.

In Equation 1, PRi means a maximum bit rate (bits / second) defined in the traffic stream addition message. Accordingly, the burst interval length Pi may be defined as the minimum time required to transmit the maximum burst size.

Then, the burst arrival interval Di (seconds) can be obtained as shown in Equation 2 from the average transmission rate MRi (bits / second) specified in the traffic stream addition message.

In other words, the burst arrival interval corresponds to the difference between the time taken at the average rate and the time taken at the maximum rate for the same traffic size.

In the present invention, it is intended to provide a transmission service by allocating a constant service bit rate (Si) to each traffic stream.

If the service rate Si of the traffic stream TSi is greater than or equal to the average rate MRi and less than the maximum rate PRi, the state Bi of the transmission buffer of the traffic stream TSi may fluctuate as shown in FIG. It has a repeating form and changes.

2 is a timing diagram illustrating a buffer state of a transmission buffer according to an embodiment of the present invention.

The state of the buffer here is the number of bits in the transmit buffer.

On the other hand, if the service rate Si of the traffic stream TSi is less than the average rate MRi, the traffic stream TSi experiences an infinite average latency and the service rate Si is greater than the maximum rate PRi. Or the like, there is no transmission latency of the traffic stream TSi.

If the service rate Si of the traffic stream TSi is greater than or equal to the average rate MRi and less than the maximum rate PRi, as shown in FIG. 2, the rising slope and decreasing of the state Bi of the buffer is shown. The slopes are (PRi-Si) and Si, respectively.

Thus the state of the maximum transmit buffer, Can be obtained as in Equation 3.

The state of the maximum transmit buffer in the preceding expression ( ) And Pi, the maximum transmission latency Ti experienced by the traffic stream TSi can be obtained as shown in Equation 4.

From Equation 4, the minimum service rate Si that satisfies the limit DBi of the transmission delay time defined in the traffic stream addition message can be obtained as shown in Equation 5.

If the service rate Si obtained from Equation 5 is smaller than the average rate MRi specified in the traffic stream addition message, the actual service rate used should be the average rate MRi.

This is because, as described above, when serving the traffic stream with a service rate Si smaller than the average rate MRi, the traffic stream TSi experiences an infinite average latency.

Based on the above description, when the total service rate available in a BSS is referred to as R (bits / second), the access point accepts a traffic stream to determine whether to accept or reject the traffic stream after receiving an additional traffic stream message from the station. The control algorithm is described below.

3 is a flowchart illustrating a traffic stream admission control method according to an embodiment of the present invention.

In step S100, the current redundant service rate is defined as AR, and the total available service rate R is initialized to the redundant service rate AR.

After the available total service rate (R) is initialized, the access point waits for a traffic stream addition message or a traffic stream deletion message from the station (S200).

In step S300, if there is a message received from the station, it is determined whether the message is a traffic addition message or a traffic deletion message.

If a traffic stream addition message including a maximum data rate PRi, a transmission delay limit DBi, and a maximum burst size Li is received, the service rate Si is calculated as shown in Equation 6.

That is, as described above, when the service transmission rate according to Equation 5 is calculated and the calculated service transmission rate is smaller than the average transmission rate, the average transmission rate is adopted as the service transmission rate.

If the received message is the traffic stream deletion message, the service transmission rate corresponding to the traffic stream deletion message is additionally added to the extra service transmission rate to update the excess service transmission rate and return to step S200 again (S400).

On the other hand, when the service transmission rate is calculated in step S500, in step S510, the excess service transmission rate AR is compared with the calculated service transmission rate Si (S510).

If the extra service rate AR is greater than or equal to the calculated service rate Si, the traffic stream corresponding to the received traffic stream addition message is accepted (S520).

If the traffic stream is accepted, the surplus service transfer rate AR is updated by subtracting the accepted service transfer rate Si from the current surplus service transfer rate AR (S530).

On the other hand, if the excess service rate AR is smaller than the calculated service rate Si, the process returns to step S200 without accepting the traffic stream corresponding to the received traffic stream addition message (S540).

Summarizing the embodiment illustrated in FIG. 3, step 500 is a process of calculating a service rate Si for a traffic stream corresponding to a traffic stream addition message received at an access point, and step S530 is currently redundant. Based on the service rate AR and the service rate Si calculated in step 500, the traffic stream corresponding to the traffic stream addition message is accepted to update the extra service rate AR.

In step 400, when the traffic stream deletion message for the currently serving traffic stream is received, the service transfer rate assigned to the traffic stream corresponding to the traffic stream deletion message is converted to the currently available service rate, thereby providing an extra service. Update the transmission (AR).

Therefore, according to an embodiment of the present invention, it is possible to determine whether to accept the traffic stream in consideration of both the currently available service rate and the requirements of the transmitted traffic stream.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, the present invention provides a remarkable capability of accepting a traffic stream that can be efficiently operated in consideration of both a service bandwidth and a requested service rate of a real-time data service in an IEEE 802.11e wireless LAN environment. With effect.

1 is a timing diagram illustrating the arrival time of a traffic stream in accordance with an embodiment of the present invention.

2 is a timing diagram illustrating a buffer state of a transmission buffer according to an embodiment of the present invention.

3 is a flowchart illustrating a traffic stream admission control method according to an embodiment of the present invention.

Claims (7)

A method for controlling acceptance of a traffic stream in a WLAN system; Initializing the total available service rate to an extra service rate; Waiting to receive a traffic stream addition message or a traffic stream deletion message; When the traffic stream addition message is received, a service rate currently required is calculated based on a predetermined maximum transmission rate Pri, a transmission delay time limit DBi, and a maximum burst size Li included in the traffic stream addition message. Doing; Comparing the required service rate with the redundant service rate to determine whether to accept a traffic stream; And Updating the redundant service rate by subtracting the calculated service rate from the redundant service rate when accepting the traffic stream Admission control method of the traffic stream comprising a. The method of claim 1, Receiving a traffic stream deletion message, And adding the service rate of the traffic stream corresponding to the traffic stream addition message to the redundant service rate to update the redundant service rate. The method of claim 1 When the average transmission rate of the traffic stream addition message is MRi, the required service transmission rate is obtained by the following equation. The method of claim 3 The threshold DBi of the transmission delay time is determined from a total service rate currently available and a required service rate. The method according to any one of claims 1 to 4, And when the redundant service rate is updated, returning to waiting for a traffic stream addition message or a traffic deletion message. A computer-readable recording medium having recorded thereon a program including a traffic stream admission control function in a WLAN system, comprising: Initializing the total available service rate to an extra service rate; Waiting for a traffic stream addition message or a traffic stream deletion message to be received; When the traffic stream addition message is received, a service rate currently required is calculated based on a predetermined maximum transmission rate Pri, a transmission delay time limit DBi, and a maximum burst size Li included in the traffic stream addition message. Function; Comparing the service rate with the redundant service rate to determine whether to accept a traffic stream; And A function of updating the extra service rate by subtracting the calculated service rate from the extra service rate when accepting the traffic stream The computer-readable recording medium having the program recorded thereon. The method of claim 6, Receiving a traffic stream deletion message; And adding the service transfer rate of the traffic stream corresponding to the traffic stream addition message to the redundant service transfer rate to update the redundant service transfer rate.