JP2006217110A - Radio lan system and multi-rate control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent each radio terminal station from repeating retransmission at a high rate impossible to communicate or from occupying a band at a rate lower than actually communicable rate. <P>SOLUTION: A radio terminal station 8-3 having received a beacon frame from a radio base station 1 transmits an assignment request frame (S4) in which transmission rate information usable in its own station is set. The radio base station 1 transmits a support rate in transmission to the radio terminal station 8-3 at the assignment response frame (S5) on the basis of the support rate of the received assignment request frame (S4). After the transmission of data frame from the radio terminal station 8-3 to the radio base station 1 is performed at the possible maximum rate, the support rate of the base station is reset on the basis of the maximum rate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wireless LAN system in which one wireless base station and a plurality of wireless terminal stations perform bidirectional communication using a specific wireless frequency, and in particular, transmission of wireless terminal stations according to a wireless line environment. The present invention relates to multi-rate control for switching rates.

  The wireless LAN system uses a configuration in which one wireless base station and a plurality of wireless terminal stations perform bidirectional communication as a basic service unit (BSS; Basic Service Set), between the wireless base station and each wireless terminal station. It has a function of switching the transmission rate, and this function is called multirate control.

  Hereinafter, the base station is an abbreviation for a radio base station, and the terminal station is an abbreviation for a radio terminal station.

An example of conventional multi-rate control will be described with reference to FIG.
The wireless LAN system includes a base station 1 and three terminal stations 8-1, 8-2, and 8-3. The frame transmission / reception rates supported by the base station 1 are assumed to have four levels of R1, R2, R3, and R4 in order of increasing speed (in order of higher rate). Here, it is assumed that each terminal station determines that transmission is successful when it receives a response from the base station 1 in response to its own transmission.

  When a certain terminal station, for example, the terminal station 8-3, fails to transmit to the base station 1 with the transmission rate set to R1, the transmission rate is reduced to R2 one step lower and retransmitted. Next, when transmission at the transmission rate R2 fails, the transmission rate is further lowered to R3, which is one step lower, and retransmitted.

  If the base station 1 can receive the transmission when the terminal station 8-3 reduces the transmission rate to R4, the base station 1 transmits subsequent transmission data including a response to the terminal station 8-3. Transmit at rate R4. When receiving a response from the base station 1 to the transmission performed at the transmission rate R4, the terminal station 8-3 transmits subsequent transmission data to the base station 1 at the transmission rate R4.

  Such control makes it possible for the base station and the terminal station in FIG. 12 to realize communication at a transmission / reception rate corresponding to the wireless channel environment.

  As an example of a wireless base station that performs multi-rate control, Patent Literature 1 describes a device that has a plurality of transmission queues and can improve the performance of the entire wireless LAN.

  Patent Document 2 describes a base station that can increase the use efficiency of frequency resources of the entire wireless communication system in consideration of the transmission speed of the terminal station and the total traffic volume.

Japanese Patent Laid-Open No. 2003-110575 (first page, FIG. 1) JP 2003-18647 (first page, FIG. 1)

  However, in the above-described conventional wireless LAN system, the transmission rate at which each terminal station first attempts transmission when performing multi-rate control is the highest (fastest) rate among the supported rates. For this reason, when the wireless network environment is poor, transmission is performed at a reduced rate until the communication is actually possible. When transmission at such a rate at which communication is actually impossible is repeated, there is a problem that the radio line is occupied and the use efficiency of the radio line is lowered.

  In addition, depending on the multi-rate control method of the terminal station, when the transmission rate is lowered to a rate lower than the actual communication rate as a result of the temporary deterioration of the wireless circuit environment due to an obstacle that has accidentally passed, Some control the transmission rate so as to maintain a low rate as it is. Compared with communication at a high rate, communication at a low rate requires a longer transmission time when the same amount of data is transmitted, so the line usage rate is higher than communication at a high rate. Therefore, in such a case, there is a problem that the use efficiency of the radio line is reduced.

  Therefore, the object of the present invention is to solve the above-mentioned problem and prevent the wireless terminal station from repeating retransmission at a high rate at which communication is impossible, or transmitting at a rate lower than the rate at which communication is actually possible, An object of the present invention is to provide a wireless LAN system that can efficiently use a bandwidth of a wireless line and a multirate control method thereof.

The wireless LAN system of the present invention is a wireless LAN system in which one wireless base station and a plurality of wireless terminal stations perform bidirectional communication at a variable rate using a specific wireless frequency. Based on the transmission / reception rate of the highest rate when the link between the terminal stations is established, the radio base station has a notification means for selecting a support rate corresponding to each radio terminal station and notifying each radio terminal station. is doing.

  The multi-rate control method of the present invention performs variable control of communication rate in a wireless LAN system in which one wireless base station and a plurality of wireless terminal stations perform bidirectional communication at a variable rate using a specific wireless frequency. A multi-rate control method for performing a support rate corresponding to each wireless terminal station based on a transmission / reception rate of the highest rate when a link between the wireless base station and the wireless terminal station is established. Select and notify each wireless terminal station.

  A radio base station according to the present invention is a wireless LAN system in which one radio base station and a plurality of radio terminal stations perform bidirectional communication at a variable rate using a specific radio frequency. And a notification means for selecting a support rate corresponding to each wireless terminal station and notifying each wireless terminal station based on the highest transmission / reception rate when the link is established.

  In the wireless terminal station of the present invention, one wireless base station and a plurality of wireless terminal stations perform bidirectional communication at a variable rate using a specific wireless frequency, and a link between the wireless base station and the wireless terminal station is established. A wireless terminal of a wireless LAN system having a notification means for selecting a support rate corresponding to each wireless terminal station and notifying each wireless terminal station based on the transmission / reception rate of the highest rate when established After receiving the attribution release frame from the base station and temporarily releasing the link, the station requests the notification of the support rate by the notification means by transmitting the attribution request frame again.

  In the wireless terminal station of the present invention, one wireless base station and a plurality of wireless terminal stations perform bidirectional communication at a variable rate using a specific wireless frequency, and a link between the wireless base station and the wireless terminal station is established. A wireless terminal of a wireless LAN system having a notification means for selecting a support rate corresponding to each wireless terminal station and notifying each wireless terminal station based on the transmission / reception rate of the highest rate when established The station requests the notification of the support rate by the notification means by transmitting a probe request frame.

  According to the present invention, by setting a support rate based on a transmission rate that has succeeded in actual communication between a radio base station and a radio terminal station, it is possible to repeat retransmission at a high rate at which communication is impossible, Therefore, it is possible to suppress transmission at a rate lower than the rate at which communication is actually possible. For this reason, there is an effect that it is possible to efficiently use the band of the radio line that is commonly used between the radio base station and the plurality of radio terminal stations.

Next, a preferred embodiment of the present invention will be described with reference to the drawings.
1 to 3 show the system and apparatus configuration of the present invention.
FIG. 1 is a configuration diagram of a wireless LAN system to which multi-rate control of the present invention is applied. The basic service unit (BSS) is a BSS 20 managed by the base station 1, and is composed of the base station 1 and a plurality (N stations) of terminal stations 8 (terminal stations 8-1 to 8-N). Here, N is an integer greater than or equal to 2, and FIG. 1 illustrates a case where N is 3 as an example.

  Two-way communication is performed between the base station 1 and the terminal station 8 (terminal stations 8-1 to 8-N) using a specific radio frequency F1. In a wireless LAN system, a base station is generally a device called a wireless LAN access point (AP) and a terminal station is a device called a wireless LAN terminal (STA: Station).

  The base station 1 is also connected to a wired network 40 based on a standard such as Ethernet (registered trademark), thereby enabling mutual connection between the wireless LAN system and the wired network. The wired network 40 accommodates other communication devices such as the host 30 and is connected via a bridge (or router) 50 to another wired network 41 that accommodates the host 31 and the host 32.

  In FIG. 1, only the BSS 20 which is one basic service unit is shown as the wireless LAN system, but a plurality of basic service units can be provided.

  FIG. 2 is a configuration diagram of the base station (base station 1 in FIG. 1) in the present invention.

  The base station 1 includes a wireless transmission / reception circuit 2, a medium access control circuit 3, a transmission / reception data buffer unit 4, a wired I / F (interface) circuit 5, a base station control unit 6, and a transmission rate control unit 7. Have.

  The radio transmission / reception circuit 2 establishes a radio line with the terminal station 8, performs transmission / reception of radio frequency signals, and modulates / demodulates signals to be transmitted / received.

  The medium access control circuit 3 controls access to a wireless line as a communication medium through the wireless transmission / reception circuit 2.

  The transmission / reception data buffer unit 4 temporarily stores (buffers) transmission / reception data transmitted / received through the medium access control circuit 3 and the wired I / F circuit 5.

  The wired I / F circuit 5 performs connection control and data transmission / reception with the wired network 40.

  The base station control unit 6 is a control circuit configured by a circuit including, for example, a microprocessor (MPU: Micro Processing Unit), and controls each unit and each circuit in the base station 1.

  The transmission rate control unit 7 switches the transmission rate of each transmission frame in the medium access control circuit 3 under the control of the base station control unit 6.

  Note that the medium access control circuit 3 according to the present embodiment performs medium access control conforming to IEEE 802.11, which is one of the wireless LAN standard protocols.

FIG. 3 is a block diagram of the terminal station (terminal station 8 in FIG. 1) in the present invention.
In FIG. 3, the terminal station 8 is illustrated on the assumption that the terminal station 8 is a device that is mounted on or built in an OA device (office automation device) such as a personal computer (PC) or a printer, or a household electrical appliance. The device or the home appliance itself may be a device that incorporates the function of the terminal station 8.

  Here, the terminal station 8 includes a radio transmission / reception circuit 9, a medium access control circuit 10, a transmission / reception data buffer unit 11, an internal I / F (interface) circuit 12, a terminal station control unit 13, and a transmission rate control unit. 14.

  The radio transmission / reception circuit 9 transmits / receives a radio frequency signal through a radio line established with the base station 1 and modulates / demodulates a signal to be transmitted / received.

  The medium access control circuit 10 controls access to a wireless line as a communication medium through the wireless transmission / reception circuit 9.

  The transmission / reception data buffer unit 11 temporarily stores (buffers) transmission / reception data respectively transmitted / received through the medium access control circuit 10 and the internal interface circuit 12.

  The internal I / F circuit 12 performs connection control and data transmission / reception with a circuit in a device mounted on the PC or the like.

  The terminal station control unit 13 is a control circuit configured by a circuit including a microprocessor (MPU), for example, and controls each unit and each circuit in the terminal station 8.

  The transmission rate control unit 14 switches the transmission rate of each transmission frame in the medium access control circuit 10 according to the control of the terminal station control unit 13.

  Note that the medium access control circuit 10 performs medium access control conforming to IEEE 802.11.

  Next, an embodiment using the system configuration and apparatus configuration of FIGS.

4 to 6 show frame formats used in this embodiment.
FIG. 4 is an example of a frame format exchanged between the base station 1 and the terminal station 8 (terminal stations 8-1 to 8 -N) when the radio link is connected. Note that each address in the following description is a MAC (Media Access Control) address.

  (A) is an attribution request frame format 21 transmitted from the terminal station 8, and includes transmission rate information, a frame identifier (attribute request), a destination address (base station), a source address (terminal station), It consists of a support rate set, other attribution request information, and FCS (frame check sequence).

  In the frame identifier, a value indicating that it is an attribution request frame is set. The destination address is set to the address of the base station 1 that is the counterpart (attribute request destination). When the terminal station 8 that is the attribution request source is, for example, the terminal station 8-N, the address of the terminal station 8-N is set as the transmission source address, and the terminal station 8-N is used as the support rate set. Possible transmission / reception rates are set. The transmission rate information indicates the transmission rate of the frame actually used. Other related information is set in other attribution request information.

  Next, (B) is an attribution response frame format 22 transmitted from the radio base station 1, and includes transmission rate information, a frame identifier (attribute response), a destination address (terminal station), and a source address (base). Station), support rate set, other attribution permission information, and FCS (frame check sequence).

  In the frame identifier, a value indicating that it is an attribution response frame is set. Further, when the terminal station 8 serving as a response destination (attribute request source) is the terminal station 8-N, the address of the terminal station 8-N is set as the destination address. Then, the address of the base station 1 that is the attribution response source is set in the transmission source address, and the transmission / reception rate that can be used by the base station 1 is set in the support rate set. The transmission rate information indicates the transmission rate of the frame actually used. Other related information is set in other attribution permission information.

  Each terminal station 8 (terminal stations 8-1 to 8 -N) that desires connection to the base station 1 transmits the attribution request frame format 21 to the address of the base station 1. When the base station 1 that has received the attribution request frame format 21 permits the connection of the terminal station that has transmitted the attribution request frame format 21, the base station 1 sends the attribution request frame format 21 to the address of the terminal station that has transmitted the attribution request frame format 21. A response frame format 22 is transmitted. At this time, the base station and the terminal station notify each other of transmission / reception rates that they can use as a support rate set included in the attribution request frame format 21 and the attribution response frame format 22.

  FIG. 5 is an example of a disassociation frame format transmitted from the base station 1 to the terminal station 8 (terminal stations 8-1 to 8-N). Note that each address in the following description is a MAC (Media Access Control) address.

  The attribution cancellation frame format 23 includes transmission rate information, a frame identifier (affiliation cancellation), a destination address (terminal station), a source address (base station), a reason code for attribution cancellation, and an FCS (frame check sequence). It consists of.

  In the frame identifier, a value indicating that it is an attribution release frame is set. Further, for example, the address of the wireless terminal station 8-N that is the counterpart (attribute response destination) is set as the destination address. And the address of the base station 1 which becomes an attribution response origin is set to a transmission source address. The transmission rate information indicates the transmission rate of the frame actually used. In addition, the reason for attribution cancellation is set in the reason code for attribution cancellation.

  The attribution cancellation frame is transmitted when the base station requests the attribution cancellation of the corresponding terminal station and when it requests the resetting of the attribution. There is no response frame in the attribution release frame. Therefore, the terminal station that has received the attribution cancellation frame addressed to itself transmits the attribution request frame in the format of (A) of FIG. 4 again when it is necessary to continue communication with the base station. .

  FIG. 6 is a format example of a data frame exchanged between the base station 1 and the terminal station 8. Note that each address in the following description is a MAC (Media Access Control) address.

  The data frame format 26 includes transmission rate information, a frame identifier (data), a destination address, a transmission source address, a data body (IP packet), and an FCS (frame check sequence).

  In the frame identifier, a value indicating a data frame is set. The destination address is set to the address of the terminal station 8 or base station 1 that is the destination. Then, the address of the base station 1 or the terminal station 8 serving as the transmission source is set as the transmission source address. The transmission rate information indicates the transmission rate of the frame actually used. The data body contains IP packet data.

  Next, the operation of the present embodiment using the above formats will be described.

  FIG. 7 is a first sequence diagram in which the base station uses the multi-rate control of the present invention to control the transmission rate of the terminal station, and is explained by communication between the base station 1 and the terminal station 8-3. To do.

  The terminal station 8-3, which has detected the beacon frame (S1) transmitted from the base station 1 to the terminal station, transmits to the base station 1 an attribution request frame (S2, S3, S4) for requesting a wireless link connection. . It is assumed that the terminal station 8-3 sets four rates R1 to R4 as transmission / reception rates (support rates) that can be used by the own station in these attribution request frames. R1 to R4 are in the order of R1, R2, R3, and R4, with R1 being the highest (faster) rate and R4 being the lowest (slow) rate.

  In FIG. 7, after failing to transmit the attribution request frame (S2) at the highest rate R1, the terminal station 8-3 transmits the attribution request frame (S3) at the next highest rate R2. Also failed. Then, the transmission of the attribution request frame (S4) has succeeded by the transmission with the rate lowered to the rate R3.

  The base station 1 that has received the attribution request frame (S4) permits the attribution if the support rate of the terminal station 8-3 includes at least one transmission / reception rate that can be used by the own station. An attribution response frame (S5) is returned. The base station 1 sets a transmission / reception rate that allows the terminal station 8-3 to use the support rate in the frame.

  In FIG. 7, the base station 1 transmits four rates (R1 to R4) received in the attribution request frame (S4) as support rates in the attribution response frame (S5) to the terminal station 8-3. Permitted to use.

  The rate notified by the terminal station as the support rate is a transmission / reception rate that can be used as the performance of the wireless terminal station. However, in an actual wireless network environment, an error actually occurs on the transmission path even if the transmission rate is included in the support rate due to the distance between the base station and the terminal station and the conditions such as shielding. May not be used. In this case, the terminal station determines that the transmission has failed because there is no delivery confirmation response indicating that it has been normally received from the base station that is the destination of the transmitted frame, and is controlled by the transmission rate controller 14 of the terminal station The frame is retransmitted at a lower transmission rate.

  In FIG. 7, the first data frame (S6) has been successfully transmitted at the transmission rate R3. Although not shown, the base station 1 sends a delivery confirmation response to the terminal station that sent the data frame after receiving the data frame normally, and the same applies to the transmission / reception of the data frame described below. And

  Since the communication at R3, which is lower than the highest rate R1 among the support rates, has succeeded, the terminal station 8-3 increases the rate R2 by one step higher when the next data frame (S7) is transmitted. I am trying to send it up. If the rate has dropped due to a temporary deterioration of the line condition, communication can be successful even with R2, so communication is attempted by increasing the rate to R2, which is one step higher. However, if communication at the rate R2 is impossible in the wireless channel environment where the terminal station 8-3 is located, transmission at the rate R2 fails again and the rate is lowered to R3. In FIG. 7, the transmission of the data frame (S7) at the rate R2 fails, and the data frame (S8) is transmitted with the rate lowered to R3.

  The medium access control circuit 3 of the base station 1 can identify the transmission rate of the data frame received from the terminal station 8-3 from the transmission rate information in the frame. Based on this identification, the base station 1 succeeds in reception when the transmission from the terminal station 8-3 is performed at a rate of R3 or lower, but receives it when it is performed at a rate of R2 or higher. Recognize that it will not succeed.

  Here, in FIG. 7, based on the notification from the medium access control circuit 3, the control unit 6 of the base station 1 determines that communication with the terminal station 8-3 is possible only at a rate of R 3 or less, and the terminal station 8 -3 is transmitted to the terminal station 3 and the terminal station 8-3 is temporarily disconnected.

  The terminal station 8-3 that has received the attribution release frame (S9) transmits an attribution request frame (S10) in order to request the attribution to the base station 1 again. On the other hand, the base station 1 sets only the support rates R3 and R4 and transmits the attribution response frame (S11). In this embodiment, two support rates, R3 and R4, are set. However, only one R3 may be used, and if there is a lower rate available in this embodiment, these are included. It is also possible to set three or more.

  Since the terminal station can use only the rate included in the support rate notified by the attribution response frame from the base station, in this embodiment, the terminal station 8-3 can be used in subsequent communications. The only transmission rates are R3 and R4.

  As a result, even if the terminal station 8-3 successfully transmits at the rate R3, the terminal station 8-3 does not increase the rate to the rate R1 or the rate R2 in subsequent transmissions.

  FIG. 8 is a second sequence diagram in which the base station shows control of the transmission rate of the terminal station using the multi-rate control of the present invention, and is explained by communication between the base station 1 and the terminal station 8-2. To do.

  Upon detecting the beacon frame (S101) transmitted from the base station 1 to the terminal station, the terminal station 8-2 transmits to the base station 1 an attribution request frame (S102, S103) that requests connection of a radio link. Here, the terminal station 8-2 has successfully transmitted the attribution request frame at the rate R2. Then, after successfully transmitting the data frame (S105) at the transmission rate R2, the terminal station 8-3 attempts to transmit the data frame (S106) by increasing the rate to the transmission rate R1, but fails. The data frame (S107) is transmitted again at the transmission rate R2.

  With this control, the base station 1 determines that the terminal station 8-2 can communicate with R2, and sends R2 and R3 as support rates in the attribution response frame (S110) to the terminal station 8-2. Notice. Note that the number of support rates is not limited to two, but can be set to one or three or more, but in this embodiment, it is assumed to be set to two.

  As a result, it is possible to prevent the terminal station 8-2 from increasing the rate to R1 and decreasing the rate to R4.

  As described above, according to the present invention, since the support rate is set based on the transmission rate that has succeeded in actual communication between the radio base station and the radio terminal station, It is possible to prevent repeated retransmissions and transmission at a rate lower than the rate at which communication is actually possible.

  Next, Embodiment 2 will be described with reference to FIGS. In the second embodiment, the support rate is reset using a probe request frame and a probe response frame.

  FIG. 9 is a format example of a probe request frame and a probe response frame exchanged between the base station 1 and the terminal station 8. The probe request frame is a frame that is originally transmitted for the purpose of searching for a neighboring base station by a terminal station, and a base station that matches a search condition (network ID, support rate) specified by the terminal station is a response frame. return it. Note that each address in the following description is a MAC (Media Access Control) address.

  (A) is a probe request frame format 24 transmitted from the terminal station 8, and includes transmission rate information, a frame identifier (probe request), a destination address (base station), a source address (terminal station), It consists of a network ID (SSID), a support rate set, and an FCS (frame check sequence).

  A value indicating a probe request frame is set in the frame identifier. In the present embodiment, the destination address is set to the address of the base station 1 that is the counterpart (request destination) for resetting the support rate. When the terminal station 8 serving as the request source is, for example, the terminal station 8-N, the address of the terminal station 8-N is set as the transmission source address, and the SSID (Service Set Identifier) is set as the network ID. A transmission / reception rate is set in the support rate set. The transmission rate information indicates the transmission rate of the frame actually used.

  Next, (B) is a probe response frame format 25 transmitted from the base station 1, and includes transmission rate information, a frame identifier (probe response), a destination address (terminal station), and a transmission source address (base station). ), Network ID (SSID), support rate set, other BSS control information, and FCS (frame check sequence).

  In the frame identifier, a value indicating a probe response frame is set. Further, the address of the terminal station 8, which is a response destination (request source), for example, the terminal station 8-N is set as the destination address. Then, the address of the base station 1 that is the response source is set in the transmission source address, the SSID that is the setting value of the base station 1 is set in the network ID, and the transmission / reception rate that the base station 1 can use in the support rate set Is set. The transmission rate information indicates the transmission rate of the frame actually used. In addition, information related to basic service unit (BSS) control is set in other BSS control information.

  The probe request is originally intended for a newly participating terminal station to search for a base station to connect to, but it is necessary to move to another base station even after assignment to a base station is completed Many wireless terminal stations continue to search for base stations by continuously transmitting probe request frames.

  10 is obtained by replacing the attribution release frame (S9), the attribution request frame (S10), and the attribution response frame (S11) of FIG. 7 with a probe request frame (S209) and a probe response frame (210). Is the same as FIG.

  FIG. 11 is obtained by replacing the attribution release frame (S108), the attribution request frame (S109), and the attribution response frame (S110) of FIG. 8 with a probe request frame (S308) and a probe response frame (309). Others are the same as in FIG.

  As shown in FIGS. 10 and 11, when the terminal station 8-2 continues to transmit the probe request frame even after the completion of the assignment to the base station 1, the base station 1 resets the support rate in the probe response frame. Is possible. Therefore, as in the examples of FIG. 7 and FIG. 8, without re-assigning the terminal station once, while maintaining the belonging of the corresponding terminal station, repeating retransmission at a high rate at which communication is impossible, It is possible to prevent transmission at a rate lower than the communicable rate.

  Priorities are set for a plurality of terminal stations 8 (terminal stations 8-1 to 8-N) in advance, and the base station control unit 6 of the base station 1 supports each terminal station based on the priorities. It is also possible to set the rate. In this case, the base station can set different maximum rates and minimum rates of the support rate to be notified using the attribution response frame or the probe response frame for each terminal station.

1 is a configuration diagram of a wireless LAN system to which multi-rate control of the present invention is applied. FIG. It is a block diagram of the base station in this invention. It is a block diagram of the terminal station in this invention. It is a figure which shows the format of the attribution request frame and the attribution response frame concerning Example 1 of this invention. It is a figure which shows the format of the attribution cancellation | release frame concerning Example 1 of this invention. It is a figure which shows the format of the data frame concerning Example 1 of this invention. It is a sequence diagram of the 1st transmission rate control concerning Example 1 of this invention. It is a sequence diagram of the 2nd transmission rate control concerning Example 1 of this invention. It is a figure which shows the format of the probe request frame and probe response frame concerning Example 2 of this invention. It is a sequence diagram of the 1st transmission rate control concerning Example 2 of this invention. It is a sequence diagram of 2nd transmission rate control concerning Example 2 of this invention. It is a sequence which shows the multi-rate control in the conventional wireless LAN system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base station 2 Wireless transmission / reception circuit 3 Medium access control circuit 4 Transmission / reception data buffer part 5 Wired I / F (interface) circuit 6 Base station control part 7 Transmission rate control part 8 Terminal station 9 Wireless transmission / reception circuit 10 Medium access control circuit 11 Transmission / reception Data buffer unit 12 Internal I / F (interface) circuit 13 Terminal station control unit 14 Transmission rate control unit 20 Basic service unit (BSS)
21 Attribute Request Frame Format 22 Attribute Response Frame Format 23 Dissociation Frame Format 24 Probe Request Frame Format 25 Probe Response Frame Format 26 Data Frame Format 30, 31, 32 Host 40, 41 Wired Network 50 Bridge (or Router)

Claims (20)

A wireless LAN system in which one wireless base station and a plurality of wireless terminal stations perform bidirectional communication at a variable rate using a specific wireless frequency,
Based on the transmission / reception rate of the highest rate when the link between the radio base station and the radio terminal station is established, the radio base station selects a support rate corresponding to each radio terminal station, and A wireless LAN system comprising notification means for notifying a wireless terminal station.   2. The wireless LAN system according to claim 1, wherein the notifying means notifies the highest transmission / reception rate when the link is established as the highest transmission rate.   3. The wireless LAN system according to claim 1, further comprising means for pre-assigning a priority order to each wireless terminal station and changing the support rate of each wireless terminal station based on the priority order.   When the attribution request frame transmitted from the wireless terminal station is received by the base station, and the attribution response frame transmitted from the base station corresponding to the attribution request frame is received by the wireless terminal station, the radio 4. The wireless LAN system according to claim 1, wherein the link between the base station and the wireless terminal station is established.   The base station once releases the link by transmitting an attribution release frame to the wireless terminal station, receives the attribution request frame from the wireless terminal station again, and then notifies the support rate by the notification means. The wireless LAN system according to claim 1, wherein: 5. The wireless LAN system according to claim 1, wherein said support rate is notified by said notifying means after receiving a probe request frame from said wireless terminal station. A multi-rate control method for performing variable control of a communication rate in a wireless LAN system in which one radio base station and a plurality of radio terminal stations perform bidirectional communication at a variable rate using a specific radio frequency,
Based on the transmission / reception rate of the highest rate when the link between the radio base station and the radio terminal station is established, the radio base station selects a support rate corresponding to each radio terminal station, and A multirate control method characterized by notifying a wireless terminal station.   8. The multi-rate control method according to claim 7, wherein the notifying means sets the highest transmission / reception rate when the link is established as a maximum transmission rate.   9. The multi-rate control method according to claim 7, wherein a priority is assigned in advance to each wireless terminal station, and the support rate of each wireless terminal station is changed based on the priority.   When the attribution request frame transmitted from the wireless terminal station is received by the base station, and the attribution response frame transmitted from the base station corresponding to the attribution request frame is received by the wireless terminal station, the radio 10. The multirate control method according to claim 7, wherein the link between the base station and the wireless terminal station is established.   The base station once releases the link by transmitting an attribution release frame to the wireless terminal station, receives the attribution request frame from the wireless terminal station again, and then notifies the support rate by the notification means. The multi-rate control method according to claim 7, wherein: 11. The multi-rate control method according to claim 7, wherein the support rate is notified by the notifying unit after receiving a probe request frame from the wireless terminal station. A wireless LAN system in which one wireless base station and a plurality of wireless terminal stations perform bidirectional communication at a variable rate using a specific wireless frequency,
Notification means for selecting a support rate corresponding to each wireless terminal station and notifying each wireless terminal station based on the transmission / reception rate of the highest rate when the link with the wireless terminal station is established. A radio base station comprising:   The radio base station according to claim 13, wherein the notifying means notifies the highest transmission / reception rate when the link is established as a maximum transmission rate.   15. The radio base station according to claim 13, further comprising means for pre-assigning a priority to each radio terminal station and changing the support rate of each radio terminal station based on the priority.   16. The attribution response frame is transmitted corresponding to the attribution request frame after receiving the attribution request frame transmitted from the wireless terminal station in order to establish the link. Radio base station.   The link is temporarily released by transmitting an attribution release frame to the wireless terminal station, and after receiving an attribution request frame from the wireless terminal station again, the support unit notifies the support rate. Item 17. A radio base station according to items 13 to 16. 17. The radio base station according to claim 13, wherein the support rate is notified by the notifying unit after receiving a probe request frame from the radio terminal station. Highest when a link between the radio base station and the radio terminal station is established when one radio base station and a plurality of radio terminal stations perform bidirectional communication using a specific radio frequency at a variable rate. The wireless base station is a wireless terminal station of a wireless LAN system having notification means for selecting a support rate corresponding to each wireless terminal station and notifying each wireless terminal station based on the transmission / reception rate of the rate. And
A wireless terminal station, which receives an attachment cancellation frame from the base station, temporarily releases the link, and then transmits an attachment request frame again to request notification of the support rate by the notification means. One radio base station and a plurality of radio terminal stations perform bidirectional communication at a variable rate using a specific radio frequency, and the highest when a link between the radio base station and the radio terminal station is established The wireless base station is a wireless terminal station of a wireless LAN system having notification means for selecting a support rate corresponding to each wireless terminal station and notifying each wireless terminal station based on the transmission / reception rate of the rate. And
A wireless terminal station that requests notification of the support rate by the notification means by transmitting a probe request frame.

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