KR20060078223A - Medium access control method for providing qos of voip in public wireless lan and apparatus thereof - Google Patents

Abstract

The present invention relates to a medium access control (MAC) method for guaranteeing a service quality of real-time traffic such as VoIP in an IEEE 802.11-based public wireless LAN.

According to the configuration of the present invention, the access point receives the MAC frame from the wireless terminal, examines the voice call identification field of the frame, and determines the activation of the voice call. If the voice call is deactivated, the wireless terminal is added to the inactive node list, the inactivity timer is started, and when the inactivity timer ends, the wireless terminal is added to the adaptive node list. The wireless terminal included in the adaptive node list attempts to access the medium through the PCF scheme, which is a non-competitive scheme.

WLAN, Access Point, PCF, DCF, MAC

Description

Medium access control method for providing voice over IP quality of service in public WLAN and its control device

1 is a schematic diagram illustrating a relationship between a terminal and an access point in a public WLAN service.

2 illustrates a superframe structure supporting resource allocation and synchronization of an access point.

3 is a block diagram illustrating a WLAN network system according to an embodiment of the present invention.

4 is a frame diagram illustrating the structure of a MAC frame header and a frame control field in an embodiment of the present invention.

5 is a diagram illustrating the operation of an inactivity timer in an embodiment of the present invention.

6 illustrates a polling list for PCF mode operation according to an embodiment of the present invention.

7 is a diagram illustrating a process of switching an active node into an inactive node to maintain an adaptive polling list according to an embodiment of the present invention.

8 is a diagram illustrating a process of switching an inactive node into an active node in order to maintain an adaptive polling list according to an embodiment of the present invention.

9 is a flowchart illustrating a medium access control method according to an embodiment of the present invention.

The present invention relates to a medium access control (MAC) method for guaranteeing the quality of service of real-time traffic such as VoIP in an IEEE 802.11-based public wireless LAN, and an apparatus supporting the same.

In the current public WLAN, the medium access control of the wireless section uses the CSMA / CA (Carrier Sense Medium Access / Collision Avoidance) method. In this scheme, the medium access control is basically implemented by contention between terminals. In the CSMA / CA scheme, when the number of competing terminals or traffic increases in one access point (AP), the delay time for accessing the medium increases.

In the IEEE 802.11 standard, media access is controlled using a distributed coordination function (DCF) of contention and a point coordination function (PCF) of polling.

In the DCF operation, a distributed coordination function is performed to share a wireless medium between an AP having a compatible physical layer and an AP, and a medium is controlled by avoiding collision between terminals by checking whether a detected channel is empty.

In the PCF operation, the point coordinator of the AP transmits a Contention-Free Poll (CF Poll) frame to each terminal, and the terminal, which responds thereto, preferentially accesses the medium and transmits the frame during the non-competition period.

1 is a schematic diagram illustrating a relationship between a terminal and an access point in a public WLAN service.

 In a WLAN, a basic network unit is composed of a basic service set (BSS). One BSS has an access point to manage resource allocation and synchronization between terminals.

The plurality of wireless terminals 20 perform wireless communication with the access point 10, and the access point supports access to a network within the BSS or a network with an external Internet network.

2 illustrates a superframe structure supporting resource allocation and synchronization of an access point.

 The superframe is divided into a PCF operation mode section P1 and a DCF operation mode section P2. The start of a super frame is initiated by a periodic BEACON frame from the access point.

In the PCF operation mode (P1), the access of the terminal is basically controlled by a polling method when the network connection of the terminal is managed at the access point. The end of the PCF operation section is known to all radio terminals in the BSS by the CF-END frame. After that, all terminals including the access point are operated in the DCF operation mode based on CSMA / CA, which is a competitive approach.                         

The contention period is the remaining time except for the contention-free period in the PCF repetition interval.

Currently, an access point of a public WLAN allows an access of a terminal in DCF mode when processing a voice packet. Therefore, there is a problem in that a delay jitter is large and a delay is also increased according to channel access when the UE increases or traffic increases in the BSS. This is because a discontinuous transmission or reception delay is a factor that degrades the quality of service due to the characteristics of voice communication that requires real-time data transmission and reception.

In addition, although PCF may be used for voice packet processing, the IEEE 802.11 standard does not present a procedure for processing a voice packet using PCF.

Therefore, there is a problem that can not guarantee the transmission quality of a service requiring real-time transmission, such as VoIP service in the current public WLAN.

The present invention provides a PCF operation method and related procedures for saving wireless resources and satisfying service quality requirements in processing voice calls in an access point to solve the above problems in a public WLAN environment.

More specifically, the present invention proposes a method for processing a voice call in a medium access control (MAC) layer that manages media access control in an access point and a terminal, and based on the statistical characteristics of the voice call in the PCF operation mode. The purpose of the present invention is to provide a protocol operation method for satisfying a transmission quality required by a voice call by tracking call activity and inactivity and managing a polling list of the AP.

In accordance with an aspect of the present invention, a method for controlling a medium access in a public WLAN includes: a) an access point receiving a MAC frame from a wireless terminal; b) checking the voice call identification field of the frame to determine activation of the voice call; c) if the voice call is deactivated, adding the wireless terminal to the list of inactive nodes and initiating operation of an inactivity timer; d) adding the wireless terminal to the adaptive node list when the inactivity timer expires; And e) transmitting a poll frame to a wireless terminal included in the adaptive node list.

A method for controlling access to a medium according to a feature of the present invention, f) after step c), determining whether a voice packet is received before the timer expires; And g) when the voice packet is received, adding the wireless terminal to the adaptive node list.

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. (When a part is connected to another part, this includes not only a directly connected part but also an electrically connected part with another element in between.)

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

The embodiment of the present invention also uses the structure of the super frame consisting of the PCF mode and DCF mode shown in FIG.

In the super frame, the PCF operation section is divided into a downlink transmission section and an uplink transmission section.

The downlink operation section of the PCF operation section is used as a section for transmitting voice packets destined for the terminal from the access point, and the uplink section is received by the access point on a polling basis to transmit the voice packet generated from the terminal to a remote talker. Used as a section.

At this time, the access point polls each wireless terminal in a predetermined order using a polling-based medium access control method. In the DCF mode, all wireless terminals including an access point compete for access of a medium.

3 is a block diagram illustrating a WLAN network system according to an embodiment of the present invention.                     

The access point 100 and the terminals 20 and 21 have separate queues for processing voice packets V and data packets D separately.

In addition, the access point 100 includes a voice call inactivity timer 110, a voice call activation detector 120, and a point adjuster 130.

The voice call activation detecting unit 120 detects whether to activate or deactivate the voice call based on the information of the voice call activation field included in the frames received from the terminals 20 and 21.

If the voice call inactivation timer 110 deactivates the voice call, after the predetermined time timer is operated, the voice call inactivity timer 110 performs an operation of adding the terminal to the voice call activation node list or the adaptive node list defined in the present invention.

The point adjuster 130 updates and controls the voice call activation node list for polling according to the response of the voice call activation detector 120 and the voice call inactivity timer 110.

That is, the access point 100 according to the present invention manages the polling list managed by the access point into active and inactive states for processing voice calls, thereby not transmitting unnecessary poll frames to inactive nodes. Do not When the present invention is applied, the number of voice calls that can be accommodated in one access point is increased, and the delay time according to the medium access is also reduced by eliminating unnecessary poll frames.

The operation of the access point apparatus will be described in detail with reference to the following specific examples.

4 is a frame diagram illustrating the structure of a MAC frame header and a frame control field in an embodiment of the present invention.

The structure of the frame shown in FIG. 4 further includes a More Data field further defined by an embodiment of the present invention, in addition to the structure of the MAC frame header and frame control field recommended by IEEE 802.11.

In the embodiment of the present invention, the More data field is called a voice call identification field (F1) and is used for transferring voice call status between an access point and a terminal.

That is, when the field F1 is set to 1, a voice call is generated. When the field F1 is set to 0, a voice call is not generated. Therefore, by checking the field F1, the voice call activation detecting unit 120 can easily detect whether the voice call is activated.

5 is a diagram illustrating the operation of an inactivity timer in an embodiment of the present invention.

The voice call is activated or deactivated depending on whether or not the voice packet is transmitted from the wireless terminal. Voice packets are not generated in the inactive periods T1, T2, and T3 of the voice call. In the active period T4, a voice packet is generated according to a codec used.

On the other hand, after the voice packet is generated, if the More Data defined in the embodiment of the present invention, i.e., the voice call identification field F1 is set to 0 or no response occurs for a predetermined period, a timer for deactivating the voice call Starts the operation.

When the time T2 allocated to the inactivity timer expires, there is a high possibility that the voice packet will be generated again. Thus, the access point starts polling for the PCF operation during the period T3.

If more data is set to 1 before the inactivity timer expires, the point coordinator may start polling by adding the corresponding terminal to the adaptive node list.

6 illustrates a polling list for PCF mode operation according to an embodiment of the present invention.

When the access point indicates all of the pollable terminals as nodes 1 to 7, the active node and the inactive node may be distinguished according to whether the voice packet is generated.

In the embodiment shown in FIG. 6, active nodes are nodes 2, 4, 5, and inactive nodes are represented by nodes 1, 3, 6, 7.

In FIG. 6D, an adaptive polling list according to an embodiment of the present invention is shown. The adaptive polling list includes inactive nodes 3, which are expected to be active sooner or later by the algorithm proposed by the present invention among the current active nodes 2, 4, 5 and inactive nodes 1, 3, 6, 7. .

7 is a diagram illustrating a process of switching an active node into an inactive node to maintain an adaptive polling list according to an embodiment of the present invention.

In FIG. 7, the wireless terminal sets the voice call activity identifier field F1 to '0' using information signaled from the application layer when the voice call is no longer active. The access point deletes the corresponding active node 2 from the adaptive polling list and the active node list and inserts it into the inactive node list when the value of the field F1 of the MAC frame control field is '0'. At the same time, it starts the inactivity timer of the node. The value of the inactivity timer is based on the length of the average inactivity interval extracted from the statistical properties of the voice call. The inactivity timer value can be set to 5% or 10% of the average value.

8 is a diagram illustrating a process of switching an inactive node into an active node in order to maintain an adaptive polling list according to an embodiment of the present invention.

Inactive nodes are inserted into the adaptive polling list in two ways.

First, when the inactivity timer expires, the inactive node 3 is inserted into the adaptive polling list. The inactive node 3 inserted into the adaptive node will then have the access point send a POLL frame. The wireless terminal's response to the POLL frame transmits a voice packet if there is a voice packet to be sent, and transmits a NULL frame if it does not exist. The access point determines that the node has been switched to the active state when the voice packet comes in response to the POLL frame, and inserts it into the active node list.

In the second case, when the inactive node is switched to the active state before the inactivity timer expires, the access point signals to the access point that the inactive node has been switched to the active state by using a competitive DCF mode. In this case, the signaling uses the voice packet, and when the access point receives the voice packet from the inactive node through the DCF mode, the access point recognizes that the node has been switched to the active state, deletes the node 3 from the inactive node list, and adaptively. Insert the node into the polling list and active node list.                     

Therefore, according to the embodiment of the present invention, the access point operates only in the non-competitive PCF mode of the terminal that exists only in the adaptive node list, thereby saving radio resources.

9 is a flowchart illustrating a medium access control method according to an embodiment of the present invention.

In a public WLAN network including a plurality of wireless terminals and an access point, the access point receives a MAC frame transmitted from the wireless terminal (S100).

The access point determines whether a voice call is generated by determining whether a voice call identification field value assigned to a specific field of the MAC frame is 0 or 1 (S110). In this case, when the field value is 0, the voice call inactivity section is operated.

If the voice call identification field value is 1, it operates in the voice call active period, adds the terminal to the active node list, and transmits and receives a voice packet with the terminal in the PCF mode, which is a non-competitive method (S130, S170). .

If the voice call identification field value is 0, the voice call identification field operation is performed, the terminal is added to the voice call inactivity node list, and the operation of the predetermined voice call inactivity timer is started (S120). ).

Here, when the voice packet is received by the DCF mode or the like before the time specified in the voice call inactivity timer is completely terminated, the node is added to the active node list (S140 and S130). In the case of the step (S140), it is not the case that the voice call is likely to occur any time soon, but since the voice packet has already been generated, it is possible to insert the corresponding node in the active node list, but the illustration is omitted, but the purpose of the present invention Therefore, it is also possible to insert into the adaptive node list.

On the other hand, when the time specified by the inactivity timer expires, the access point adds the terminal to the adaptive node list (S160).

By transmitting a poll frame to the nodes included in the adaptive node list and the transport node list (S170), media access control is performed using a non-competitive PCF method, and the process returns to step S100 to determine whether a voice call is generated. The update of the list will be repeated.

The operation principle according to the embodiment of the present invention described above is based on the mutual operation of the voice call inactivity timer 110, the voice call activation detecting unit 120 and the point adjusting unit 130 in the access point apparatus of the present invention shown in FIG. 3. It will be applied as is.

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.

In the medium access control according to the configuration of the present invention, a predetermined bandwidth is adaptively allocated to a wireless terminal having a voice call in a wireless LAN. That is, a fixed bandwidth is allocated only when a predetermined time elapses after the terminal is active or inactive.

Therefore, in a plurality of voice call processing, only the radio terminal in the adaptive polling list transmits a poll frame for data transmission in an uncompetitive mode, thereby saving radio resources.

In addition, by setting the inactivity timer value smaller than the average inactivity value or signaling to the access point through the DCF mode, the transmission delay time can be guaranteed.

Claims (10)

In the medium access control method in a public wireless LAN, a) the access point receiving a MAC frame from the wireless terminal; b) checking the voice call identification field of the frame to determine activation of the voice call; c) if the voice call is deactivated, adding the wireless terminal to the list of inactive nodes and initiating operation of an inactivity timer; d) adding the wireless terminal to the adaptive node list when the inactivity timer expires; And e) transmitting a poll frame to a wireless terminal included in the adaptive node list Medium access control method comprising a. The method of claim 1, f) after step c), determining whether a voice packet has been received before the timer expires; g) adding the wireless terminal to the adaptive node list when the voice packet is received. The method of claim 2, And determining whether to receive the voice packet through signaling in a DCF mode. The method of claim 2, further comprising adding the wireless terminal to an active node list when the voice packet is received, and transmitting a polling frame to the wireless terminal included in the active node list. 3. The method of claim 2, wherein the time corresponding to the inactivity timer is determined based on an average value of voice call inactivity intervals. The method according to any one of claims 1 to 5, h) adding, by the voice call identification field value, the wireless terminal to the active node list when the voice call is activated; i) transmitting a poll frame to a wireless terminal included in the active node list and the adaptive node list, and returning to step a). An access point apparatus for controlling a medium access in a public WLAN, A first queue for temporarily storing data packets to be transmitted and received; A second queue for temporarily storing voice packets to be transmitted and received; A voice call activation detector for detecting voice call activation from a MAC frame received from the wireless terminal; A voice call inactivity timer for waiting the PCF mode for a predetermined time when the voice call activation detection unit determines that the voice call is inactive; And a point adjusting unit for controlling access to the medium in the PCF mode based on the end of the voice call inactivity timer and the voice call activation detection result of the voice call activation detection unit. The method of claim 7, wherein And the voice call activation detecting unit detects voice call activation based on a specific field value of a MAC frame header. The method of claim 8, And the voice call inactivity timer operates for less than the average voice call inactivity time. The method of claim 8, The point coordinator, the access point device for transmitting a polling frame by adding to the node list a wireless terminal or a terminal that has transmitted a voice packet while waiting for the time specified by the timer, the voice call inactivity timer has expired.

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