KR101322509B1 - AN ADAPTIVE ADMISSION CONTROL FOR FRAME BASED MULTIMEDIA TRAFFIC IN IEEE 802.11 WLANs - Google Patents

Abstract

The present invention relates to a technique for allocating a transmission opportunity (TXOP) period so that each station (STA) can transmit data to satisfy a quality of service (QoS) of multimedia data in an IEEE 802.11 WLAN.

To this end, the present invention is a distributed control method in an IEEE 802.11 WLAN for performing a admission control so that a plurality of stations (QSTA: Quality of service aware STAtion) can transmit a flow or frame during the TXOP period assigned to them, A first step of allocating the TXOP period for each frame constituting the flow when the transmission of the multimedia flow is requested from the QSTA; And a second process of allocating the TXOP period so that the idle TXOP period is added to the TXOP period of the frame received in the following order when the idle TXOP period occurs in the TXOP period allocated for each frame.

Description

Distributed reception control method in IEEE 802.11 wireless LAN {AN ADAPTIVE ADMISSION CONTROL FOR FRAME BASED MULTIMEDIA TRAFFIC IN IEEE 802.11 WLANs}

1 is a diagram illustrating an example of a Group Of Pocture (GOP) configuration of a general multimedia flow.

2 is a network configuration diagram of a wireless LAN to which the present invention is applied.

3 to 4 are flowcharts for explaining a distributed acceptance control method in an IEEE 802.11 WLAN according to the present invention.

5 is a frame structure diagram of a super frame in a WLAN to which the present invention is applied;

6 is a diagram illustrating a frame transmission schedule of a multimedia flow applied to the present invention.

7 is a view for explaining an idle TXOP sharing process according to the present invention.

Description of the Related Art

10, 12: HC (Hybrid Coordinator)

20, 30: BSS (Basic Service Se)

22, 24, 24, 31, 32: QSTA (Quality of service aware STAtion)

The present invention relates to a distributed acceptance control method in an IEEE 802.11 WLAN, and more particularly, TXOP so that each station (STA) can transmit data to satisfy a quality of service (QoS) of multimedia data in an IEEE 802.11 WLAN. (Transmission Opportunity) relates to a technique for allocating a period.

Wireless LAN is a communication network that can send and receive data without wires, and the number of users is increasing every year due to advantages such as mobility and ease of installation. Types of information that can be transmitted and received using wireless LANs have been mainly used for document information and information for using the Internet.

However, in recent years, research has been actively conducted to accommodate a voice call service, a multi-party video conferencing service, a real-time video transmission service, and the like, which require real time. Accordingly, in recent years, a wireless LAN phone capable of connecting and receiving a phone call to a wireless LAN has been commercialized.

In order to smoothly provide various application services requiring real-time performance, the WLAN has a procedure for providing a quality of service (QoS) to a terminal / user using such a service or supplementing related functions. Going through.

The basic operation of the MAC (Media Access Control) defined in the WLAN system to which the IEEE 802.11 standard is applied is performed by a hybrid coordination function (“HCF”). The HCF is an EDCA (Enhanced Distributed Channel Access) method, which is a contention-based operation method according to its operation rules, and a hybrid coordinator (hereinafter referred to as "HC") in a wireless LAN polls a station (STA) for media access. It may be classified into an HCF controlled channel access (HCCA) operation method, which is a polling-based operation method controlled by a polling) method. Here, the AP (Access Point) of the wireless LAN plays a role of the HC. In the polling method, the HC controls transmission and reception time periods and durations for specific traffic of a station QSTA.

The IEEE 802.11 polling-based HCCA scheme provides a parameterized QoS (Parameterized QoS) service, and the QoS specification of a traffic stream (hereinafter referred to as "TS") to be serviced in this parameterized QoS service is specified in the traffic specification. (Traffic SPECification, hereinafter referred to as "TSPEC"). The information contained in the QoS parameters of this TSPEC includes traffic patterns indicating whether the traffic to be serviced is periodic or not, mean data rate (ρ), which is the average data rate, and size of frames transmitted on average by the MAC. Normal MSDU Size (L), Service Interval (SI) which is the transmission service interval, Physical Transmission Rate (R) which is the transmission rate of the physical medium, Maximum Allowable Size of MSDU (M) which is the maximum frame size that can be transmitted by the MAC, and one Overhead in time unit (O), which is an additional time required for the transmission of a frame.

In the parameterized QoS service, the station (QSTA) requests the HC for service for traffic defined as TSPEC, and the HC determines whether to accept the traffic service of the requested TSPEC. If the HC accepts the traffic service of the TSPEC, the HC schedules the service time and interval for the traffic so as to satisfy the QoS requirements such as the service period and the data transmission rate required by the TSPEC.

Efficient classification for QoS traffic and efficient operation of the MAC layer of the WLAN device to guarantee the QoS characteristics required for the classified traffic are required for efficient QoS support in a wireless network employing the IEEE 802.11 WLAN. . As such, the method for classifying traffic to guarantee QoS service and the optimized operation method at the MAC level in serving the traffic have a great influence on the performance of the WLAN network.

Meanwhile, when a TXOP allocation request for transmission of a multimedia corresponding to a video is requested from a station QSTA, the HC allocates a TXOP for transmission of a flow corresponding to the multimedia to the station.

Multimedia flows generated by video coding such as MPEG-4 and H.263 corresponding to VBR (Variable Bit Rate) traffic are classified into groups consisting of I frames, P frames, and B frames, as shown in FIG. Is generated. For reference, information on the entire screen is stored in the I frame, motion correction information with the I frame or P frame screen information before the frame is stored in the P frame, and in the B frame, the previous I or P frame with the previous frame of the frame is stored. The motion correction information with the subsequent I or P frame is stored.

The P frame records only the change value from the previous I frame or the P frame (①, ②), and the B frame records only the conversion value between the I frame and the P frame (③, ④). The size of the frame is the smallest.

Although the size of the transmitted data varies depending on the type of each frame constituting the flow, the HC allocates a TXOP period of the same size to all frames in the admission control so that the frame having a large data size (eg, I In the case of a frame), the allocated TXOP time becomes insufficient, and in the case of a frame having a small data size (for example, a B frame), the TXOP period remains, so that TXOP is not efficiently allocated.

In addition, in one GOP (Group of picture) as shown by the arrows (①, ②, ③, ④) shown in FIG. 1, the B frame is decoded with reference to the P frame and the I frame, and the P frame is referred to the I frame. Because decoding, when a frame to be referred to is lost, normal decoding of an image corresponding to the corresponding GOP is impossible. As such, even in the same data flow, there is a difference in importance depending on the type of frame. This has a similar structure in H.263 as well as MPEG-4.

Therefore, in order to guarantee QoS for multimedia data, it is necessary to give priority to and process the same data flow even in the same data flow.

The present invention was created in view of the above circumstances, and the TXOP (Transmission Opportunity) period is differentiated according to the characteristics of the frame constituting the flow for the multimedia flow to be transmitted from each station (QSTA) configured in the IEEE 802.11 WLAN. It is an object of the present invention to provide a distributed acceptance control method in an IEEE 802.11 WLAN that can be allocated by guaranteeing quality of service (QoS) of multimedia data.

In addition, the present invention in the EEE 802.11 WLAN that can guarantee the quality of service (QoS) of multimedia data by assigning a priority according to the characteristics of each frame constituting the flow to be assigned a TXOP period according to the priority It is another object to provide a distributed acceptance control method.

In order to achieve the above object, the distributed acceptance control method in the IEEE 802.11 WLAN according to the present invention, performing the admission control so that a plurality of stations (QSTA) can transmit the flow or frame during the TXOP period assigned to them In the distributed control method in an IEEE 802.11 WLAN, when the transmission of a multimedia flow is requested from the QSTA, the TXOP period is allocated for each frame constituting the flow.

Preferably, the flow is characterized in that the I frame, P frame, and B frame.

Preferably, the present invention is characterized by generating a schedule based on the frame structure of the flow, and assigning a TXOP period for each frame according to the schedule.

Preferably, in the present invention, the frame structure of the flow is characterized in that the extractable from the GOP information included in the TXOP allocation request message transmitted from the QSTA.

Preferably, in the present invention, the size of the TXOP period for each frame is in the order of I frame> P frame> B frame.

Preferably, in the present invention, the frame has priority in the order of I frame> P frame> B frame.

In addition, the distributed acceptance control method in the IEEE 802.11 WLAN according to the present invention, a plurality of stations (QSTA) in the IEEE 802.11 WLAN that performs the admission control to transmit the flow or frame during its assigned TXOP period A distributed control method comprising: a first step of allocating the TXOP period for each frame constituting the flow when a transmission of a multimedia flow is requested from the QSTA; And a second process of allocating the TXOP period so that the idle TXOP period is added to the TXOP period of the frame received in the following order when the idle TXOP period occurs in the TXOP period allocated for each frame.

Preferably, the flow is characterized in that the I frame, P frame, and B frame.

Preferably, the first step of the present invention comprises the steps 1-1 of generating a schedule based on the frame structure of the flow; And a step 1-2 of allocating a TXOP period for each frame according to the schedule.

Preferably, the second step of the present invention is a step of receiving the size information of the frame to be transmitted in the next order when a predetermined frame is transmitted from the QSTA; If the size of the frame to be transmitted in the next order is larger than the TXOP period allocated according to the characteristics of the frame and the idle TXOP period occurs in the TXOP period of the currently transmitted frame, the idle TXOP period is added to the TXOP period to the Allocating a TXOP period for frames to be transmitted in the next order; And if the size of the frame to be transmitted in the next order is less than or equal to the TXOP period allocated according to the characteristics of the frame, assign the allocated TXOP period as the TXOP period for the frames to be transmitted in the next order. Characterized in having a process to.

Preferably, the present invention is characterized in that the I frame is preferentially processed by allocating a TXOP period for the I frame on the basis of the I frame SI by fixing the service interval (SI) for the I frame.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating a structure of a wireless network to which a distributed acceptance control method is applied in an EEE 802.11 WLAN according to an embodiment of the present invention.

As shown in FIG. 2, a wireless network is formed between Basic Service Sets (BBSs) 20 and 30 through HCs 10 and 12.

Each component shown in FIG. 2 will be described in more detail.

The HC (10, 12) is a module that performs the role of an access point (AP) in IEEE 802.11e, and is connected to other HC through a wired network to relay traffic of wireless users. Each HC (10, 12) operates as one station to combine the WLAN and each BSS (20, 30). Particularly, in the present invention, when the HC 10 requests TXOP allocation for multimedia transmission from the QSTA 22, 23, and 24, the TX 10 allocates a TXOP period to each frame in consideration of characteristics of each frame constituting the multimedia flow. It performs the function. For reference, the TXOP period is a time given to transmit a frame to a specific QSTA. The HCs 10 and 12 analyze the TSPECs transmitted from each STA, so that the frame structure constituting the multimedia flow can be confirmed based on the flow characteristics and the GOP information, and according to the identified frame structure, the I frame, the P frame, And differentially assign TXOP periods for B frames.

The QSTAs 22, 23, and 24 are connected to the HC 10 through a wireless medium, request polling to the HC 10, receive a TXOP period, and transmit a corresponding frame in the allocated TXOP period. In particular, the QSTAs 22 and 32 define TSPECs for the GOP information so that the HC 10 can differentially allocate the TXOP periods for the frames of the multimedia flows in the admission control.

The QSTAs 31 and 32, which are connected to the HC 10 via a wireless medium, perform the same functions as the QSTAs 22, 23 and 24 described above.

On the other hand, each BSS 20, 30 is formed by a plurality of QSTAs 22, 23, 24, 31, 32, respectively, and each BSS 20, 30 is a group of stations (STAs) in communication with each other. If a station is in an area within the same BSS, communication with other devices in the BSS area is possible. BSS is a group of terminals using radio radius of the same frequency.

Next, the distributed acceptance control method in the IEEE 802.11 WLAN according to an embodiment of the present invention will be described in detail with reference to the flowcharts shown in FIGS. 3 to 4.

If any QSTA 22 generates multimedia data to be transmitted, the QSTA 22 transmits a TXOP allocation request message for transmitting the multimedia data to the HC 10. The TXOP allocation request message includes a characteristic of a flow corresponding to the multimedia data and GOP information of the flow and is transmitted.

Receiving the TXOP allocation request message from the QSTA 22, the HC 10 analyzes the TSPEC from the TXOP allocation request message to extract the total size of the flow and GOP (Group of Picture) information of the flow (S4), A frame schedule for the flow is generated based on the extracted GOP information (S6).

Typically, the GOP may be composed of 9, 12, 15, etc., for example, when the GOP is "9", the frame structure is configured as "I0 B1 B2 P3 B4 B5 P6 B7 B8 (I9)", and the QSTA 22 In order to transmit the flow, the buffer stores I0 frames, P3 frames, B1 frames, B2 frames, P6 frames, B4 frames, B5 frames, (I9) frames, B7 frames, and B8 frames.

The HC 10 recognizes the frame structure and generates a schedule (S6), and allocates a TXOP period for each frame for the flow according to the schedule (S8), and the schedule is a frame in a buffer of the QSTA 22. This is done in the same order as the stored order. Accordingly, the HC 10 may allocate a TXOP period for a frame to be transmitted in the QSTA 22.

The TXOP period determined by the HC 10 is calculated by [Equation 1].

[Equation 1]

L: Normal MSDU size

SI: Service Interval

R: Physical Transmission Rate

M: Maximum Allowable size of MSDU

O: Overhead in time units

N: Number of normal MSDU in SI

ρ: Mean data rate

In the HC 10 of the present invention, the value of ρ is adjusted for each frame so that a TXOP period is allocated for each frame.

The value of p is determined as follows.

I frame: Maximum frame size (Burst frame size)

P frame: Mean frame size

Frame B: Normal frame size (smallest frame size, smallest value of TXOP)

As described above, as the value of ρ is determined for each frame, different TXOP periods are allocated to I frames, P frames, and B frames. The TXOP period size for each frame is in order of I frame> P frame> B frame.

In the state where the TXOP period for each frame is determined, the HC 10 transmits a TXOP assignment response message including the TXOP period information for the I frame to the QSTA 22, and the QSTA 22 transmits the POLL frame (from the HC 10). When the QoS CF-Poll) is transmitted, the I frame is transmitted to the HC 10 (see FIG. 5). While transmitting the I frame, the QSTA 22 transmits the size information of the frame stored in the buffer together with the I frame to be transmitted in the next order (S10).

The HC 10 receiving the I frame determines whether there is an idle TXOP period remaining after the I frame is transmitted among the allocated TXOP periods (S12), and as a result of the determination, TXOP of the I frame as shown in FIG. 7. If there is an idle TXOP period I _I for the period I _T (Yes in S12), the size of the frame to be transmitted in the next order is compared by comparing the size of the frame to be transmitted in the next order with the TXOP period for each frame. It is determined whether the frame is larger than the TXOP period (S14).

As a result of the determination, if the size of the frame to be transmitted in the next order is larger than the TXOP period for each frame (YES in S14), the HC 10 indicates that the additional TXOP period I _B corresponding to the idle TXOP period I _I is determined. In addition to the TXOP period I _P of the next frame (eg, P frame), TXOP periods for frames to be transmitted in the next order are allocated (S16 and S18).

On the other hand, if the idle TXOP period does not exist (No in S12), or if the size of the frame to be transmitted in the next order is not larger than the TXOP period for each frame (No in S14), the HC 10 determines each frame according to the schedule. Allocate the TXOP period for (S18).

Subsequently, the corresponding frame is received from the QSTA 22 (S20), and the HC 10 determines whether the I frame SI has been reached (S22).

In the present invention, as shown in FIG. 6, in order to give priority to each frame type in order of I frame-> P frame-> B frame, the SI of the I frame is fixed and always According to the SI, I frame is transmitted without delay. Preferably, since the GOP is repeated twice for one second, the SI of the I frame is 0.5 seconds. For reference, according to the priority, the P frame is ranked after the I frame, but if there is no I frame transmission, the scheduling strategy is maintained to be transmitted before the B frame. The HC 10 determines the polling list order to allow POLL in the SI according to the schedule strategy.

If it is determined in step S22 that the SI of the I frame has been reached (Yes in S22), the HC 10 proceeds to step S8 to allocate a TXOP period for the I frame and repeatedly proceeds to steps S8 to S20 described above.

On the other hand, if it is determined in step S22 that the SI of the I frame has not been reached (No in S22), the HC 10 determines whether the reception of the multimedia flow has ended (S24), and the reception of the multimedia flow is not confirmed. If not (No in S24), it is determined whether an idle TXOP period exists in the frame received in step S20 (S26).

As a result of the determination, when it is determined that there is an idle TXOP period (Yes in S26), the size of the frame to be transmitted in the next order is compared with the size of the frame to be transmitted in the next order and the TXOP period in the corresponding frame. It is determined whether it is larger (S28).

As a result of the determination, if the size of the frame to be transmitted in the next order is larger than the TXOP period for each frame (Yes in S28), the HC 10 indicates that an additional TXOP period I _B corresponding to the idle TXOP period I _I is determined. After adding to the TXOP period I _B of the next frame (for example, B frame) (S30), the process proceeds to step S18 to allocate a TXOP period for frames to be transmitted in the next order (S18).

When the idle period of TXOP (I _I) present in the TXOP period of the I frame as shown in Figure 7 by the above-described operation been added to this P frame the idle TXOP period (I _I) TXOP period (I _B ) Is added to the assigned TXOP period for the P frame, the idle TXOP period the TXOP period of the P-frame (I _I) is added to the B frame wherein the idle period of TXOP (I _I) is present when TXOP period (I _B In addition, the TXOP period is added to allow the idle TXOP period to be used efficiently. As described above, in the present invention, TXOP periods are differentially allocated in consideration of frame characteristics by distributing TXOP periods of the same size for each frame and distributing the TXOP periods for each frame. You will be assigned a period.

As described above, even if each frame shares the TXOP period, it does not exceed the total allocated TXOP period, and thus does not affect the TXOP period of another node or flow.

This not only effectively allocates the TXOP period but also increases the likelihood that the flow or node requesting the TXOP allocation can receive the accept request.

As described above, according to the distributed acceptance control method in the IEEE 802.11 WLAN according to an embodiment of the present invention, it is possible to allow the TXOP allocation to minimize the quality of service (QoS) of the multimedia flow, sharing scheduling and TXOP sharing Through this, there is an effect that can increase the utilization efficiency (utilization) of the wireless network than the conventional method.

On the other hand, the present invention is not limited to the above-described embodiment, but can be modified and modified within the scope not departing from the gist of the present invention, such modifications and changes should be regarded as belonging to the following claims. will be.

Claims (18)

In the distributed control method in the IEEE 802.11 WLAN for performing a admission control so that a plurality of stations (QSTA: Quality of service aware STAtion) can transmit the flow or frame during the TXOP period assigned to them, When the transmission of the multimedia flow from the QSTA is requested, the TXOP period is allocated for each frame constituting the flow Distributed Acceptance Control Method in IEEE 802.11 WLAN. The method of claim 1, The flow is characterized in that the I frame, P frame, and B frame Distributed Acceptance Control Method in IEEE 802.11 WLAN. The method of claim 2, Generate a schedule based on the frame structure of the flow, Allocating a TXOP period for each frame according to the schedule Distributed Acceptance Control Method in IEEE 802.11 WLAN. 4. The frame structure of claim 3, wherein the frame structure of the flow is Characterized in that it can be extracted from the GOP (Group Of Picture) information included in the TXOP allocation request message transmitted from the QSTA Distributed Acceptance Control Method in IEEE 802.11 WLAN. The method according to any one of claims 2 to 4, wherein the size of each frame TXOP period is I frame> P frame> B frame order Distributed Acceptance Control Method in IEEE 802.11 WLAN. The frame according to any of claims 2 to 4, wherein the frame is I frame> P frame> B frame in the order of priority Distributed Acceptance Control Method in IEEE 802.11 WLAN. The TXOP period according to any one of claims 1 to 4, wherein It is determined by [Equation 1], the value of [rho] of [Equation 1] is applied differently for each frame, characterized in that the TXOP period for each frame is allocated differently Distributed Acceptance Control Method in IEEE 802.11 WLAN. [Equation 1]

L: Normal MSDU size SI: Service Interval R: Physical Transmission Rate M: Maximum Allowable size of MSDU O: Overhead in time units N: Number of normal MSDU in SI ρ: Mean data rate The method of claim 7, wherein the p value is Apply Maximum frame size (Burst frame size) for I frames, Mean frame size for P frames, and B frame: Normal frame size (for smallest frames). Size, the smallest size of TXOP) Distributed Acceptance Control Method in IEEE 802.11 WLAN. In the distributed control method in the IEEE 802.11 WLAN for performing a admission control so that a plurality of stations (QSTA: Quality of service aware STAtion) can transmit the flow or frame during the TXOP period assigned to them, A first step of allocating the TXOP period for each frame constituting the flow when the transmission of the multimedia flow is requested from the QSTA; And a second process of allocating the TXOP period so that the idle TXOP period is added to the TXOP period of the frame received in the following order when the idle TXOP period occurs for the TXOP period allocated for each frame. Distributed Acceptance Control Method in IEEE 802.11 WLAN. The method of claim 9, The flow is characterized in that the I frame, P frame, and B frame Distributed Acceptance Control Method in IEEE 802.11 WLAN. The method of claim 10, wherein the first process A step 1-1 of generating a schedule based on the frame structure of the flow; And a step 1-2 of allocating a TXOP period for each frame according to the schedule. Distributed Acceptance Control Method in IEEE 802.11 WLAN. 12. The frame structure of claim 11, wherein the flow structure of the flow Characterized in that it can be extracted from the GOP (Group Of Picture) information included in the TXOP allocation request message transmitted from the QSTA Distributed Acceptance Control Method in IEEE 802.11 WLAN. The method according to any one of claims 10 to 12, wherein the size of each frame TXOP period is I frame> P frame> B frame order Distributed Acceptance Control Method in IEEE 802.11 WLAN. The method according to any one of claims 10 to 12, wherein the frame is I frame> P frame> B frame in the order of priority Distributed Acceptance Control Method in IEEE 802.11 WLAN. The TXOP period according to any one of claims 9 to 12, wherein the TXOP period for each frame is determined by [Equation 1], and the p value of [Equation 1] is applied differently for each of the frames. Characterized in that the periods are differentially assigned Distributed Acceptance Control Method in IEEE 802.11 WLAN. [Equation 1]

L: Normal MSDU size SI: Service Interval R: Physical Transmission Rate M: Maximum Allowable size of MSDU O: Overhead in time units N: Number of normal MSDU in SI ρ: Mean data rate The method of claim 15, wherein the p value is Apply Maximum frame size (Burst frame size) for I frames, Mean frame size for P frames, and B frame: Normal frame size (for smallest frames). Size, the smallest size of TXOP) Distributed Acceptance Control Method in IEEE 802.11 WLAN. The method of claim 9, wherein the second process is Receiving size information of a frame to be transmitted in a next order when a predetermined frame is transmitted from the QSTA; If the size of the frame to be transmitted in the next order is larger than the TXOP period allocated according to the characteristics of the frame, and the idle TXOP period occurs in the TXOP period of the currently transmitted frame, the idle TXOP period is added to the TXOP period. Allocating a TXOP period for frames to be transmitted in the next order; And  If the size of the frame to be transmitted in the next order is less than or equal to the TXOP period allocated according to the characteristics of the frame, the allocated TXOP period according to the characteristics of the frame is allocated as the TXOP period for the frames to be transmitted in the next order. Characterized in that it comprises a process Distributed Acceptance Control Method in IEEE 802.11 WLAN. The method of claim 10 or 11, By fixing a service interval (SI) for the I frame to allocate the TXOP period for the I frame based on the I frame SI to process the I frame preferentially Distributed Acceptance Control Method in IEEE 802.11 WLAN.

Images