KR100747592B1 - Method for transmitting data adopted variable inter frame space at a variable data transfer rate in wireless LAN system - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for transmitting data by variably changing the time interval between frames according to the data rate in a WLAN system.

2. The technical problem to be solved by the invention

The present invention checks whether the access point supports a variable interframe time interval when receiving an registration request from a station, and if the station supports a variable interframe time interval, the access point transmits data including data rate information at the station. If a variable inter-frame time interval is received and the station does not support the variable inter-frame time interval, the access point commands the use of the fixed inter-frame time interval to all stations using the variable inter-frame time interval. It is an object of the present invention to provide a method for transmitting data by varying a time interval between frames according to a data rate in a WLAN system for transmitting and receiving data.

3. Summary of Solution to Invention

The present invention provides a method for transmitting data by varying the time interval between frames in an access point of a WLAN system, the first step of confirming whether the station supports a variable time interval between frames when receiving a registration request from a station; ; If the station supports a variable interframe time interval, instructing the newly requested station to use the variable interframe time interval; Transmitting data rate information for determining a variable interframe time interval to the station so that the station varies and transmits the interframe time interval according to the data rate; And a fourth step of instructing all stations currently registered to use the fixed interframe time interval if the newly registered station does not support the variable interframe time interval.

4. Important uses of the invention

The present invention is used in a wireless LAN system.

WLAN, Fixed IFS, Variable IFS, Backoff Time, DIFS, PIFS, SIFS

Description

Method for transmitting data adopted variable inter frame space at a variable data transfer rate in wireless LAN system}

1 is a diagram illustrating an embodiment of a relationship between time intervals between fixed frames in a conventional DCF connection environment.

2 is a diagram illustrating an embodiment of a relationship between time intervals between variable frames in a DCF connection environment to which the present invention is applied;

3 is a diagram illustrating an embodiment of a data transmission process using a variable interframe time interval to which the present invention is applied;

4 is a flowchart illustrating a method for transmitting data by variably changing a time interval between frames according to a data rate in a WLAN system according to the present invention.

* Explanation of symbols on the main parts of the drawing

10; First station

20; Access point

30; Second station

The present invention relates to a method for transmitting data by variably changing the time interval between frames according to the data rate in a wireless LAN system. More specifically, the access point supports a variable time interval when receiving an registration request from a station. If the station supports the variable interframe time interval, the access point transmits data including data rate information to receive the data with the variable interframe time interval from the station, and the station transmits the variable interframe time interval. If it is not supported, the access point transmits and receives data by instructing the use of a fixed interframe time interval to all stations using the interframe time interval. to It relates to a method of the same to transmit data.

A wireless LAN system allows a station (eg, PDA, notebook, etc.) to transmit and receive data within a certain distance around an access point.

The WLAN system has been proposed by the IEEE 802.11 WLAN Committee to transmit data wirelessly in a local area environment, and currently wireless LAN products are used.

In the WLAN system, collision between stations sharing the same channel is inevitable, which may occur when several stations simultaneously transmit data because the stations may not know when other stations competing with each other will transmit. Because there is.

The IEEE 802.11 specification uses Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) technology to reduce the collision probability.

In addition, the structure of the medium access control (MAC) layer of the IEEE 802.11 standard proposes a distributed coordination function (DCF) and a point coordination function (PCF) as an access method, and the representative access method is a DCF based on CSMA / CA. There is a random approach to the channel through competition between stations.

1 is a diagram illustrating an embodiment of a relationship between time intervals between fixed frames in a conventional DCF connection environment.

Before describing FIG. 1, the time interval between frames is hereinafter referred to as "IFS (Inter Frame Space).

The IFS is defined as follows. That is, the IFS used for the ACK frame is referred to as " SIFS (Short IFS) " hereinafter, and the IFS operating under the PCF is referred to as " PIFS (PCF IFS) " The IFS used by a station to transmit a packet is hereinafter referred to as "DIFS (DCF IFS), and the IFS used when a transmission error occurs is called" EIFS "(Extended IFS). .

In addition, slot time is a time required for backoff time. In this case, the description of the EIFS is omitted.

Hereinafter, for convenience of description, the fixed IFS will be referred to collectively as SIFS, PIFS, DIFS, and slot time.

As shown in FIG. 1, a first station to transmit data in a conventional WLAN system waits if the second station is busy, and during DIFS when the second station terminates channel use. After confirming that the channel is idle, a random backoff time is generated to avoid collision with the third station to which data is to be transmitted. In other words, the first station waits for a " DIFS + backoff time " to transmit data.

Thereafter, when the backoff time decreases to 0, the first station transmits data (MSDU packet). In this case, the first station may check whether the data has been successfully transmitted by receiving the ACK frame within the SIFS time.

The first station also waits for "DISF + Backoff Time" to transmit the next frame.

Meanwhile, the fixed IFS is a fixedly defined value according to a physical layer protocol (PHY). For example, in IEEE 802.11a, SIFS is 16 ms, PIFS is 25 ms, DIFS is 34 ms, slot time is 9 ms. In IEEE 802.11b, SIFS is 10 ms, PIFS is 30 ms, DIFS is 50 ms, slot. The time is 20 seconds.

As described above, the conventional WLAN system has a disadvantage in that the waste of the channel is caused by the fixed IFS. That is, the fixed IFS may be changed according to radio frequency (RF) performance, media access control (MAC) device performance, modem performance.

In addition, in the conventional wireless LAN system, data rates supported by IEEE 802.11a are 1, 2, 5.5, and 11 Mbps, and data rates supported by IEEE 802.11b are 6, 9, 12, 18, 24, 36, 48, and 54. Mbps, where the fixed IFS has a fixed value for such a data rate. For this reason, the conventional WLAN system has a disadvantage that the entire channel is not used efficiently according to the data rate.

The present invention has been proposed to solve the above-mentioned problem. When the access point receives a registration request from a station, the present invention checks whether a variable interframe time interval is supported, and if the station supports a variable interframe time interval, the access point transmits data rate information. All stations that use the variable interframe time interval are transmitted from the station by transmitting the data including the data, and if the station does not support the variable interframe time interval, the access point uses the time interval between the station and the variable frame. It is an object of the present invention to provide a method for transmitting data by varying the time interval between frames in accordance with the data rate in a WLAN system for transmitting and receiving data by instructing the use of a fixed interframe time interval.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. It will also be appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

In order to achieve the above object, the present invention provides a method for transmitting data by varying an interframe time interval in an access point of a WLAN system, and when the station receives a registration request, the station supports a variable interframe time interval. Verifying that the first step is made; If the station supports a variable interframe time interval, instructing the newly requested station to use the variable interframe time interval; Transmitting data rate information for determining a variable interframe time interval to the station so that the station varies and transmits the interframe time interval according to the data rate; And a fourth step of instructing all stations currently registered to use the fixed interframe time interval if the newly registered station does not support the variable interframe time interval.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating an embodiment of a relationship between variable IFS in a DCF connection environment to which the present invention is applied.

As shown in Fig. 2, under the DCF connection environment to which the present invention is applied, the relationship of the variable IFS is formed according to the IFS which is variably determined according to the data rate.

Hereinafter, for convenience of description, the variable IFS will be collectively referred to as a variable SIFS (vSIFS), a variable PIFS (vPIFS), a variable DIFS (vDIFS), and a variable slot time.

Referring to Equations 1 to 4, the fixed IFS has a relationship represented by the above equations.

As shown in Equation 1 to Equation 4, since the SIFS and the slot time are different according to the physical layer (PHY), the reception RF delay, the physical layer reception preamble delay, the medium access control processing delay, and the reception transmission conversion delay are different. The fixed and fixed values are shown, and the PIFS and DIFS are values determined by SIFS and slot time.

In addition, the backoff time is a value determined by the slot time since the slot time of Equation 2 is used.

As described above, SIFS and slot time are fixed by determining the reception RF delay, physical layer reception preamble delay, media access control processing delay, transmission transmission conversion delay, etc. according to the technology level at the time of IEEE 802.11 standard (1999). It is possible to set the SIFS and slot time variably by improving the radio frequency performance, the performance of the medium access control device, and the modem performance by the improved technology level compared to the time when the IEEE 802.11 standard was enacted. Here, since PIFS, DIFS, and backoff time are also values determined by SIFS and slot time, they may also be set variably.

3 is a diagram illustrating an embodiment of a data transmission process using a variable IFS to which the present invention is applied.

As shown in FIG. 3, a station occupying a channel in a wireless LAN system using a variable IFS to which the present invention is applied transmits an MSDU at a transmission rate of 6 Mbps and at a transmission rate of 6 Mbps in response thereto after the first vSIFS. Receive an ACK frame.

Subsequently, the station occupying the channel transmits an MSDU at a transmission rate of 54 Mbps by performing a backoff time using a first variable slot time after the first vDIFS, and receives an ACK frame at a transmission rate of 54 Mbps in response thereto. . In this case, it can be seen that the intervals of the second SIFS, the second DIFS, and the second variable slot time are narrower than the first SIFS, the second DIFS, and the first variable slot time.

In addition, a station that does not occupy a channel may set a network allocation vector (NAV) to prevent data transmission.

In particular, the access point 20 transmits a frame of a physical layer header including data rate information to every station that supports variable IFS every time the MSDU is transmitted. The station sets a variable IFS to be applied at the next frame transmission / reception using data rate information included in the physical layer header upon receiving the MSDU.

As described above, the variable IFS to which the present invention is applied is applied variably according to the data rate, so that the channel can be efficiently used while inducing fair competition in the contention period.

Table 1 is an example of the value of the variable IFS according to the data rate in the case of IEEE 802.11a to which the present invention is applied.

Data rate (Mbps) Value of Variable IFS vSIFS vPIFS vDIFS Variable slot time 6 16 25 34 9 9 16 25 34 9 12 15 23 31 8 18 15 23 31 8 24 14 21 28 7 36 14 21 28 7 48 13 19 25 6 54 13 19 25 6

In Table 1, the variable IFS is determined differently depending on the WLAN system to be implemented or determined using experimental data.

Referring to FIG. 3, when a station supporting variable IFS transmits data at a transmission rate of 6 Mbps and receives an ACK frame at a transmission rate of 6 Mbps, the first vSIFS is 16 ms, the first vPIFS is 25 ms, and the first vDIFS. Is 34 ms and the first variable slot time is set to 9 ms.

On the other hand, when a station supporting variable IFS transmits data at a data rate of 54 Mbps and receives an ACK frame at a data rate of 54 Mbps, the second vSIFS is 13 ms, the second vPIFS is 19 ms, the second vDIFS is 25 ms, The second variable slot time is set to 6 ms.

4 is a flowchart illustrating a method of transmitting data by variably changing IFS according to a data rate in a WLAN system according to the present invention.

As shown in FIG. 4, the data transmission method according to the present invention is described as being performed in a WLAN system including an access point 20, a first station 10, and a second station 20. In this case, the first station 10 is a station supporting variable IFS and fixed IFS, and the second station 20 is a station supporting only fixed IFS.

In addition, the access point 20 is an access point supporting variable IFS and fixed IFS, and registers the first station 10 and the second station 30 to perform data communication in the WLAN system.

First, the access point 20 transmits a beacon frame to the first station 10 to notify the variable IFS support (S100). The first station 10 transmits a registration request message to the access point 20 while notifying the variable IFS support (S101). At this time, the access point 20 checks whether the first station 10 supports the variable IFS (S102).

Thereafter, the access point 20 transmits a registration message of the variable IFS to the first station 10 and transmits a beacon frame including a usage command of the variable IFS (S103). At this time, the first station 10 confirms that the registration request message of the variable IFS has been successfully transmitted to the access point 20 and completes the registration of the variable IFS (S104).

Thereafter, the access point 20 transmits data including data rate information to the first station 10 (S105). At this time, the first station 10 checks the data rate information included in the received data, and transmits the data to the access point 20 by applying a variable IFS according to the confirmed data rate (S106).

Meanwhile, the access point 20 transmits a beacon frame to the second station 30 newly entering the wireless LAN network to notify that it supports variable IFS (S107). The second station 30 transmits a registration request message while notifying the fixed IFS support to the access point 20 (S108). At this time, the access point 20 confirms the registration request of the second station 30 supporting the fixed IFS (S109).

Thereafter, the access point 20 transmits a beacon frame or broadcast message to the first station 10 transmitting and receiving data using the variable IFS, thereby requesting the use of the fixed IFS and using the fixed IFS. Send a command (S110). At this time, the first station 10 completes the registration of the fixed IFS by stopping the use of the variable IFS and using the fixed IFS (S111).

At the same time, the access point 20 transmits a beacon frame including a usage command of the fixed IFS while transmitting a registration message of the fixed IFS to the second station 30 (S112). At this time, the second station 30 confirms that the registration request message of the fixed IFS has been successfully transmitted to the access point 20 and completes the registration of the fixed IFS (S113).

Thereafter, the access point 20 transmits data including data rate information to the first station 10 and the second station 30 (S114). At this time, the first station 10 and the second station 30 transmit data by applying a fixed IFS regardless of the data rate (S115, S116).

As such, the access point 20 uses the variable IFS for all stations even if a station supporting only one fixed IFS, such as the second station 30, is newly entered into the WLAN network to which the variable IFS is applied. Instructs to stop and transfer data using fixed IFS.

On the other hand, when the access point 20 confirms the withdrawal of the registration station and the occurrence of the unregistered station registration request, the access point 20 resumes the aforementioned registration procedure (S117).

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily implemented by those skilled in the art will not be described in more detail.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

The present invention as described above, the conventional WLAN system by compensating for the waste of the channel due to the time interval between fixed frames, and has the effect of minimizing the waste of the channel while being compatible with the conventional WLAN system.

In addition, the present invention has the effect of increasing the efficiency of the entire channel by transmitting data by varying the time interval between frames in accordance with the data rate.

Claims (4)

In the method for transmitting data by varying the time interval between frames in the access point of the WLAN system, A first step of confirming whether the station supports a variable interframe time interval when receiving a registration request from a station; If the station supports a variable interframe time interval, instructing the newly requested station to use the variable interframe time interval; Transmitting data rate information for determining a variable interframe time interval to the station so that the station varies and transmits the interframe time interval according to the data rate; And A fourth step of instructing all stations currently registered to use the fixed interframe time interval if the newly requested station does not support the variable interframe time interval. A method of transmitting data by variably changing the time interval between frames according to the data rate in a WLAN system comprising a. According to claim 1, Prior to the first step, when the station enters a wireless LAN network, the wireless LAN system further comprises the step of notifying the support of the variable frame time interval in the wireless LAN system by varying the inter-frame time interval in accordance with the data rate to change the data How to transfer. According to claim 1, And transmitting data by varying the time interval between the frames in accordance with the data rate in the wireless LAN system, wherein the data rate information is included in the third layer and transmitted in the physical layer header frame of the data. According to claim 1, In the third step, the variable inter-frame time interval according to the data rate is determined by using experimental data in the WLAN system, the method for transmitting data by varying the inter-frame time interval in accordance with the data rate.

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