JP3334869B2 - Transmission rate control method for packet communication using polling method and base station communication apparatus for packet communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission rate control method for packet communication using a polling method, and more particularly to, for example, a standardization group for a wireless LAN system including transmission of a single frame having a plurality of logical destinations. IEEE Std 802.11-1997 “Wireless
LAN Medium Access Control (MAC) and Physical Layer
(PHY) specification, which relates to a transmission rate control method suitable for a polling method or the like that is optionally adopted.

[0002]

2. Description of the Related Art Conventionally, in packet communication, a distributed control type access system and a centralized control type access system are widely used.

In the former, each communication station controls transmission, and CSMA / CD (Carr) used in Ethernet is used.
ier Sense Multiple Access / Collision Detection). This method can be implemented relatively easily, but during high traffic, retransmission occurs frequently due to packet collisions and communication efficiency is reduced.

[0004] In the latter, a base station controls a transmission request of each communication station to realize mutual communication without collision, and a method using polling is generally known. This method is effective especially during high traffic, and does not cause a decrease in communication quality. However, on the other hand, a complicated control process is required for the base station, and a communication path is shared by data packets and control packets such as polling, thereby causing overhead.

[0005] As described above, both types have advantages and disadvantages, and are properly used depending on the traffic situation, the characteristics of the system, and the type of frame.

For example, IEEE Std 802.11-1997 by the standardization group of the wireless LAN system
“Wireless LAN Medium Access Control (MAC) and Phys
icalLayer (PHY) specification ”, the default is CSMA / CA (Carr
Although it adopts ier Sense Multiple Access / Collision Avoidance, PCF (Point Cordination Function), which is a centralized control type access method, is optionally defined. This is a method using the above-mentioned polling, and an operation outline thereof will be described below.

FIG. 5 shows a network configuration, and FIG. 6 shows communication between a base station and a slave station when PCF is used. Respectively,
This is an example of a case where three base stations (STAs) belong to one base station (AP: Access Point). A
P has a polling list in which STA1-STA2-STA3 are registered, and according to this, CF-Po
11 frames are transmitted in the order of registration.

[0008] The STA that has received CF-Poll means that the transmission right has been granted. First, CF-Poll
Upon receiving the frame, the STA1 recognizes that the own station has a transmission right, and transmits the Data frame stored in the own station. Next, the AP follows the polling list and
Send CF-Poll to TA2. At this time, S
CF meaning confirmation of arrival of Data frame from TA1
-Send ACK at the same time.

[0009] Here, AP is CF-Poll and CF-A
Each CK is configured as a different frame, and STA2
Transmission to the STA1 and the STA1 individually increases the traffic and decreases the use efficiency of the communication path. Therefore, the above-mentioned IEEE Std 802.1
No. 1 defines a CF-Poll + CF-ACK frame. This is a single frame with two meanings.

[0010] Upon receiving the CF-Poll + CF-ACK frame, STA1 recognizes that the Data frame transmitted by its own station has arrived by CF-ACK. Also,
STA2 that has received CF-Poll + CF-ACK,
The CF-Poll recognizes that the own station has the transmission right, and transmits the Data frame stored in the own station.

[0011] Next, the AP, according to the polling list, S
Send CF-Poll to TA3. At this time, it is necessary to transmit a CF-ACK to STA2 as in the previous example. Further, the figure shows a case where a Data frame addressed to STA3 is stored in the AP. In this case, the AP sends a CF-ACK to STA2,
Then, a Data + CF-Poll + CF-ACK frame having three meanings, Data and CF-Poll, is transmitted.

[0012] Thus, IEEE Std 802.1
In the PCF of No. 1, several frames having a plurality of meanings are defined. In this case, these frames will logically have multiple destinations.

It is known that, in conventional packet communication, by performing communication at a low speed, the receiving accuracy of a modem is improved. In a communication system having a plurality of transmission rates, fallback control for improving communication efficiency by controlling the transmission rate according to a propagation situation is used. The fallback control generally involves a method of increasing the transmission rate when transmission to a certain destination station is successful, and decreasing the transmission rate when the transmission fails.

[0014]

In the radio communication, the distance between the stations and the propagation condition dynamically change due to the characteristic that the mobile station can move. Therefore, it is necessary to control the transmission rate for each station in order to always efficiently communicate under various communication line conditions. IEEEStd above
802.11-1997 “Wireless LAN Medium Acce
ss Control (MAC) and Physical Layer (PHY) specificat
ion "is also configured as a system with multiple transmission rates.

The plurality of transmission rates are composed of a default rate set for all stations and an optional rate set for each station. However, the above-mentioned IEEE Std 802.11-1997
“Wireless LAN Medium Access Control (MAC) and Physi
The cal Layer (PHY) specification "does not clearly describe how to control the transmission rate.

In particular, the multi-rate control method for a frame having a plurality of destinations used in the PCF is more complicated than the transmission rate control for a single destination frame.
Necessary for system realization.

An object of the present invention is to provide a wireless LAN standardized IEEE.
It is an object of the present invention to provide a method for easily realizing multi-rate control of a single frame having a plurality of logical destinations when realizing a system using the PCF as defined in EE802.11.

[0018]

According to the present invention, there is provided a transmission rate control method for packet communication using a polling method, which comprises a base station for packet communication using a polling method and including a single frame having a plurality of logical destinations. When the transmission frame transmitted from the station is a single frame having the plurality of logical destinations, the transmission frame is set to be equal to or less than the minimum transmission rate among the current transmission rates set for the plurality of destinations. Is transmitted at the maximum transmission rate that satisfies the condition (1) and that is indispensably implemented in all stations.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram of a base station communication apparatus showing an embodiment of the present invention, FIG. 2 is a flowchart for determining an optimum transmission rate from a destination of a transmission frame, and FIG. FIG. 4 is a time chart showing the processing of the communication device.

In FIG. 1, when a user data frame is input from an input terminal 110, a frame generator 1
50 generates a transmission frame according to the managed polling list. The transmission rate control unit 160 determines an optimal transmission rate from the destination of the transmission frame according to the algorithm shown in the flowchart of FIG.

After transmitting the frame from the transmission terminal 120 to the communication channel, the transmitter 170 notifies the protocol controller 180 of the completion of the transmission. The protocol control unit 180 controls the transmitter 1
In accordance with the transmission completion notification from 70 and the frame reception notification from receiver 190, transmission rate control section 160 is instructed to increase or decrease the transmission rate.

The protocol control unit 180 instructs the frame generation unit 150 to transmit or retransmit the next frame according to the transmission completion notification from the transmitter 170 and the frame reception notification from the receiver 190.

Next, the operation of the present invention will be described with reference to FIGS.

The frame generator 150 buffers user data generated by a data frame generator (not shown) as needed. At the start of polling, frame generation section 150 generates a CF-Poll addressed to STA1 and requests transmission to transmission rate control section 160.

The transmission rate control section 160 determines a transmission rate according to the destination of the transmission frame according to the algorithm shown in FIG. That is, it is determined whether or not the destination of the frame requested to be transmitted from the frame generation unit 150 is singular or plural (step 600). If the destination is singular, the transmission rate currently set for the destination STA is directly used as the transmission rate. The determination is made and the transmission start is instructed to the transmitter 170 (step 620).

On the other hand, when there are a plurality of destinations of the frame requested to be transmitted from the frame generation unit 150 (destination A and destination B), the currently set transmission rates CRa and CRb of the destinations A and B are checked. (Step 610) The transmission rate that is the maximum rate that satisfies TxR ≦ min (CRa, CRb) and that is indispensably implemented in all stations is changed to a new transmission rate Tx
R is determined (step 630), and the transmitter 170 is instructed to start transmission (step 640).

As shown in FIG. 3, the rate set table managed by the transmission rate control unit 160 indicates that some of the plurality of transmission rates (rate 1, rate 3, and rate 5 in FIG. 3) are all stations. It must be implemented indispensably, and other rates (rate 2, rate 4) can be selected as optional. Therefore, when there are a plurality of frame destinations, rate 1, rate 3, rate 5
The rate that satisfies the above condition is determined from the above.

For example, when the transmission rate is set as rate 1 <rate 2 <rate 3 <rate 4 <rate 5 and the currently managed rate set table is in the state shown in FIG. 3, a transmission request is received from the frame generation unit 150. Registered frame I
When D includes two destinations “1” and “2”, the transmission rate control unit 160 determines that the current rate of the registration ID “1” is 5
And confirms that the current rate of the registration ID “2” is 4, determines rate 3 as a rate that satisfies the above conditions, and instructs the transmitter 170 to transmit this transmission request frame at rate 3. I do.

After completing the transmission, the transmitter 170 notifies the protocol controller 180 of the completion of the transmission. The protocol control unit 180 recognizes the success of the transmission by being notified of the frame reception from the polled slave station from the receiver 190 within a certain period after the transmission is completed. Protocol control unit 180
When the transmission success is recognized, the transmission rate control unit 160 is instructed to increase the rate, and the frame generation unit 150 is instructed to transmit the next frame.

The transmission rate control section 160 controls the transmittable rate of the STA in accordance with a rate up instruction. The frame generation unit 150 transmits the next frame according to the polling list.

The protocol control unit 180 recognizes that the transmission has failed if the frame reception from the polled slave station has not arrived within a certain period after the transmission is completed. When recognizing the transmission failure, the protocol control unit 180 instructs the transmission rate control unit 160 to reduce the rate and the frame generation unit 150 to retransmit.

When retransmission has continued for a certain number of times, protocol control section 180 instructs frame generation section 150 to discard the frame and transmit the next frame. The upper limit of the number of retransmissions is determined depending on the system and propagation characteristics.

[0033]

According to the present invention, the wireless LAN standardization IE
It is possible to easily realize transmission rate control of a single frame having a plurality of logical destinations, as used in the PCF defined in EEE802.11, and each station can be easily moved. Since it is possible to easily control the transmission rate of each station in which the distance between the stations and the propagation conditions dynamically change, communication can always be efficiently performed under various communication line conditions.

Further, by using the method shown in the present invention, it is possible to easily perform transmission rate control for a frame having a plurality of destinations.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the present invention.

FIG. 3 is a diagram illustrating an example of a rate set table managed by a transmission rate control unit according to the present invention.

FIG. 4 is a time chart showing the operation of the present invention.

FIG. 5 is a diagram showing a conventional example.

FIG. 6 is a diagram illustrating a communication operation between a base station and a slave station when a conventional PCF is used.

[Explanation of symbols]

 110 Transmission Frame Input Terminal 120 Transmission Frame Output Terminal 130 Receive Frame Input Terminal 140 Receive Frame Output Terminal 150 Frame Generation Unit 160 Transmission Rate Control Unit 170 Transmitter 180 Protocol Control Unit 190 Receiver

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/28-12/46 H04L 29/08

Claims (4)

(57) [Claims] In a packet communication using a polling method, which includes a single frame having a plurality of logical destinations, a transmission frame transmitted from a base station is a single frame having a plurality of logical destinations. Sometimes, the transmission frame is the maximum transmission rate that satisfies the condition of the minimum transmission rate or less among the current transmission rates set for each of the plurality of destinations, and is indispensably implemented in all stations. A transmission rate control method for packet communication using a polling method, characterized in that transmission is performed at a certain transmission rate. 2. The packet communication using the polling method is performed by an IE based on a wireless LAN system standardization group.
2. The transmission rate control method for packet communication using a polling method according to claim 1, wherein the packet communication is packet communication defined by EE Std 802.11-1997. 3. A frame generation unit for generating a transmission frame from an input user data frame in accordance with a managed polling list, and when the frame generated by the frame generation unit has a single destination, the frame generation unit The currently set transmission rate is directly determined as the transmission rate and the transmission start is instructed to the transmitter. When the frame generated by the frame generation unit has a plurality of destinations, the destination is set for each of the plurality of destinations. Determine the transmission rate of the frame that is the maximum transmission rate that satisfies the condition of the minimum transmission rate or less in the current transmission rate, and that is indispensably implemented in all stations as the transmission rate of the frame. A base station communication apparatus for packet communication using a polling method, comprising: a transmission rate control unit for instructing a start of transmission. 4. The packet communication using the polling method is performed by an IE based on a standardization group of a wireless LAN system.
4. The base station communication apparatus for packet communication using a polling method according to claim 3, wherein the communication is packet communication defined by EE Std 802.11-1997.