JP2003078532A - Transmission control method, communication system, communication equipment and communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make equal the transmission chances of the data of a plurality of communication terminals sharing a transmission path without decreasing the through-put of the transmission path. SOLUTION: A base station 30 counts the number of communication terminals 40 present in a basic server area 35, and decides a back-off time since a frame is transmitted from each communication terminal 40 to the base station 30 until the next frame is transmittable according to the counted number of terminals. The base station 30 transmits information related with the decided back-off time to the basic server area 35 by including it in a beacon, and the communication terminal 40 sets the back-off time according to the information included in the received beacon, and transmits data to the base station 30 according to the back-off time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission control method, a communication system, a communication device, and a communication terminal suitable for use when a plurality of communication terminals share a transmission line for communication.

[0002]

2. Description of the Related Art For example, when a mobile computer having a wireless communication function performs wireless communication with a base station of a communication network providing a wireless communication service, or when a plurality of computers communicate with other computers via the same wired communication line. When a plurality of communication terminals share a transmission line and perform communication, such as when performing wired communication, it is necessary to perform some kind of access control regarding the use of the transmission line. Therefore, for example, CDM
Various access control methods such as A method, FDMA method, TDMA method, polling method, ALOHA method, and CSMA method have been put into practical use.

Here, in the CSMA method, carrier communication is performed on the transmission path before the communication terminal transmits a frame (unit of data transmission), and it is confirmed that the transmission path is not used by another communication terminal. The frame is transmitted later. For example, in a wireless LAN compliant with the IEEE802.11 standard, the access control method is the CSMA method with a frame collision avoidance function added to the CSMA method.
The SMA / CA method is adopted. In addition, in Ethernet (registered trademark) which is a wired LAN, a CSMA / CD obtained by adding a transmission frame collision detection function to the above CSMA method.
The method is adopted.

[0004]

By the way, in a communication system adopting the CSMA system, for example, a large amount of data is transmitted, that is, frames are transmitted one after another to a plurality of communication terminals sharing a transmission line. If there are more than a certain number of communication terminals that are in use, it is difficult to obtain a frame transmission opportunity when another communication terminal that shares the transmission path tries to transmit data during the data transmission period of these communication terminals. However, there was a problem that it took time to send data.

On the other hand, for example, the access control method T
In a communication system that employs the DMA method, data transmission time slots are assigned in advance to each communication terminal that shares a transmission path, so that the data transmission opportunity of each communication terminal is completely guaranteed. However, in this case, when the number of communication terminals that are actually transmitting data is small among the plurality of communication terminals that share the transmission path, the throughput of the transmission path decreases, and the required data transmission of the communication terminals is required. Many losses are included in time.

The present invention has been made in view of the circumstances described above, and makes it possible to equalize the data transmission opportunities of a plurality of communication terminals sharing a transmission line without lowering the throughput of the transmission line. An object of the present invention is to provide a transmission control method, a communication system, a communication device, and a communication terminal that can be performed.

[0007]

In order to solve the above problems, the transmission control method of the present invention determines the number of communication terminals capable of receiving a signal transmitted from a communication device and transmitting data to the communication device. A counting process performed by the communication device, a signal transmission process in which the communication device transmits a signal based on the number of vehicles counted in the counting process to the communication terminal, and a signal transmitted in the signal transmission process. The receiving process received by the communication terminal, and the communication terminal receiving the signal in the receiving process transmits data to the communication device based on the signal and then transmits the next data to the communication device. And a transmission control step of transmitting data to the communication device in accordance with this waiting time.

According to the present invention, the communication terminal obtains the waiting time based on the number of the communication terminals indicated by the signal received from the communication device, and transmits the data to the communication device according to the waiting time.

Further, the communication system of the present invention is a communication system having a communication device and a communication terminal capable of transmitting data to the communication device, wherein the communication device receives a signal transmitted from the communication device. The communication terminal has counting means for counting the number of possible communication terminals, and signal transmitting means for transmitting a signal based on the number counted by the counting means to the communication terminal, wherein the communication terminal is the signal transmitting means. Receiving means for receiving the signal transmitted by the device, and based on the signal received by the receiving means, until it becomes possible to transmit the next data to the communication device after transmitting the data to the communication device. And a transmission control means for transmitting data to the communication device according to the waiting time.

According to the present invention, the communication terminal obtains the waiting time based on the number of communication terminals indicated by the signal received from the communication device, and transmits the data to the communication device according to the waiting time.

Further, the communication device of the present invention includes counting means for counting the number of communication terminals capable of receiving the signal transmitted from the communication device and transmitting data to the communication device, and the counting means. It is possible for the communication terminal to transmit data to the communication device, and then to transmit the next data to the communication device And a transmission means for transmitting to the communication terminal as information for the communication terminal to obtain the standby time until the above.

According to the present invention, the communication device generates a signal for notifying the number of communication terminals capable of receiving the signal transmitted from the communication device and capable of transmitting data to the communication device, and communicates this signal. The terminal transmits to the communication terminal as information for obtaining the waiting time.

Further, the communication device of the present invention includes counting means for counting the number of communication terminals capable of receiving a signal transmitted from the communication device and transmitting data to the communication device, and the counting means. Based on the number of units, the communication terminal obtains a waiting time from when data is transmitted to the communication device until it becomes possible to transmit the next data to the communication device, and a signal for notifying the waiting time is transmitted. It has a generating means for generating and a transmitting means for transmitting the signal generated by the generating means to the communication terminal.

According to the present invention, the communication device obtains the waiting time of the communication terminal based on the number of communication terminals capable of receiving the signal transmitted from the communication device and capable of transmitting the data to the communication device. A signal notifying the waiting time is transmitted to the communication terminal.

Further, the communication terminal of the present invention includes a receiving means for receiving a signal from the communication device housing the communication terminal under the control of the number of the communication terminals housed under the communication device, Based on the number of signals indicated by the signal received by the receiving means, the waiting time from when the communication terminal can transmit data to the communication device until the next data can be transmitted to the communication device is determined. And a transmission control means for transmitting data to the communication device in accordance with the waiting time determined by the determining means.

According to the present invention, the communication terminal determines the waiting time based on the number of the communication terminals indicated by the signal received from the communication device, and transmits the data to the communication device according to the waiting time.

Further, in the communication terminal of the present invention, a communication device that accommodates the communication terminal under its control can transmit data to the communication device and then transmit the next data to the communication device. Receiving means for receiving a signal notifying the waiting time until it becomes possible, deciding means for deciding the waiting time of the communication terminal according to the signal received by the receiving means, and waiting time decided by the deciding means Transmission control means for transmitting data to the communication device.

According to the present invention, the communication terminal transmits data to the communication device according to the waiting time indicated by the signal received from the communication device.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In addition, the same reference numerals are given to common portions in each drawing. Further, such an embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily modified within the scope of the present invention.

[A-1. Configuration of Embodiment] <1. Configuration of Wireless LAN> FIG. 1 is a block diagram illustrating a configuration of a wireless LAN 1 including base stations 30a and 30b and communication terminals 40a to 40d according to the present invention. As shown in the figure, the wireless LAN 1 includes a gateway server 10, a control server 20, a base station 30a,
30b and communication terminals 40a-40d. Also,
The communication terminals 40a to 40d use CSMA as a media access control method in a wireless transmission path (wireless channel) for transmitting data to the base stations 30a and 30b.
/ CA (Carrier Sense Multiple Access / Collision
Avoidance) method is adopted.

In FIG. 1, in order to prevent the drawing from becoming complicated, predetermined base stations 30a and 30b constituting the wireless LAN 1 and predetermined communication terminals 40a to 40a accommodated in the extended service area 36 of the wireless LAN 1 to Only 40d is shown. Further, in the present specification, unless otherwise specified, the base stations 30a and 30b are the base station 30, the communication terminals 40a to 40d are the communication terminals 40, and the basic service areas 35a and 35b are the basic service areas 3 unless otherwise specified.
It is described as 5.

The gateway server 10 is a wireless LAN 1
And has a function for interconnecting the Internet. In addition, the control server 20 includes a wireless LAN 1
For each communication terminal 40 that subscribes to the packet communication service provided by, the terminal ID of the communication terminal 40 and the basic service area 3 in which the communication terminal 40 is currently located.
5 is registered in association with the base station ID of the base station 30 that covers No. 5.

The base station 30 performs wireless communication with the communication terminal 40 located in the basic service area 35 covered by the base station 30 and transmits / receives packet data. The base station 30 has a function of counting the number of communication terminals 40 in the basic service area 35. The communication terminal 40 in the basic service area 35 transmits a frame (unit of data transmission) to the base station 30. From the next frame until the next frame can be transmitted according to the counted number of communication terminals 40, and a signal including information about the determined backoff time is used as the basic service area 35. It has a function of transmitting (broadcasting) inside.

The communication terminal 40 is a mobile device that receives a packet communication service provided by the wireless LAN 1, and is, for example, a mobile computer having a wireless communication function. The communication terminal 40 has a function of performing wireless communication with the base station 30 covering the basic service area 35 in which the own device 40 is located, and performing packet communication with various communication devices connected to the Internet via the wireless LAN 1. is doing.

In this embodiment, the plurality of communication terminals 40 existing in the same basic service area 35 are
A frame is transmitted by sharing one radio channel with the base station 30 that covers the basic service area 35.

Therefore, the communication terminal 40 adopts the CSMA / CA method as the media access control method as described above, performs carrier sense of the radio channel before transmitting the frame to the base station 30, and It is determined whether the communication terminal 40 is transmitting a frame to the base station 30 using the wireless channel, that is, whether the wireless channel is in the idle state. Then, when the communication terminal 40 determines that the wireless channel is in the idle state as a result of the carrier sense, the communication terminal 40 executes the frame transmission, completes the transmission of the frame, and then transmits a plurality of predetermined types of back packets. After waiting for the back-off time designated by the base station 30 in the off-time, carrier sense for transmitting the next frame is performed. On the other hand, if the communication terminal 40 determines that the wireless channel is not in the idle state as a result of carrier sensing, the communication terminal 40 performs carrier sensing for transmitting a frame after waiting for a predetermined transmission delay time, for example.

<2. Configuration of Base Station> FIG. 2 is a block diagram illustrating a hardware configuration of base station 30 shown in FIG. As shown in the figure, the base station 30 has a wired communication interface 301, a storage unit 302, a wireless communication unit 306, and a CPU 307, and these units are connected by a bus 308. In addition, the storage unit 302
ROM 303, RAM 304, HD (Hard Dis
k) and the like non-volatile memory 305.

The wired communication interface 301 controls wired communication between the base station 30, the gateway server 10, the control server 20 and other base stations 30. Further, the ROM 303 stores programs and the like that control basic control of each unit of the base station 30.

The RAM 304 is used as a work area for the CPU 307, and temporarily stores programs executed by the CPU 307 and various data. Also,
The RAM 304 has a control bit storage area 304a. In the control bit storage area 304a, the communication terminal 40 determined by the base station 30 according to the number of spheres of the communication terminal 40 in the basic service area 35 of the own station 30.
Control bit data for designating the back-off time of is stored.

The non-volatile memory 305 stores an operating system for the base station 30. Further, the non-volatile memory 305 has a control bit table 30.
5a. This control bit table 305a contains
As shown in FIG. 3, the number of spheres of the communication terminal 40 in the basic service area 35 and the control bit data designating the back-off time of the communication terminal 40 are stored in association with each other. In the example shown in the figure, for example, when the number of communication terminals 40 in the basic service area 35 is “0” to “3”, the control bit data “0” is the communication terminal in the basic service area 35. When the number of resident areas of 40 is “4” to “7”, the control bit data “1” is associated and stored.

As can be seen from FIG. 3, in the control bit table 305a, the larger the number of communication terminals 40 in the basic service area 35, the larger the amount of backoff time designated by the control bit data. Designed to be value. The "back-off time data" item shown by the dotted line in FIG.
The backoff time designated by the control bit data is described for reference, and the original control bi
It is not a data item forming the t table 305a.

Returning to FIG. 2, the wireless communication section 306 controls wireless communication with the communication terminal 40. This wireless communication unit 306 is controlled by the control bit under the control of the CPU 307.
A beacon including the control bit data stored in the storage area 304 a is generated, and this beacon is transmitted in the basic service area 35. In addition, the wireless communication unit 306
Communication terminal 40 located in basic service area 35
A wireless signal is generated by superimposing the packet data addressed to the communication terminal 40, and the wireless signal received from the communication terminal 40 is demodulated to obtain packet data and the like.

Here, the beacon is a radio signal periodically transmitted by the base station 30 into the basic service area 35, and is transmitted, for example, at a rate of several times per second.
The beacons are not always transmitted in the same cycle, and may be transmitted at a transmission timing deviating from a predetermined transmission cycle. This beacon is originally used for each communication terminal 40 in the basic service area 35 to specify the base station 30 to access, or to establish synchronization with each other. It is a signal. In the present invention, the control bit data designating the back-off time is transmitted to the communication terminal 40 using this beacon.

The CPU 307 executes the various programs stored in the storage unit 302 to cause the bus 30
Control each part of the device connected via 8. This C
The PU 307 performs control b as processing peculiar to this embodiment.
The it determination process (see FIG. 6) and the beacon transmission process (see FIG. 7) are executed.

<3. Configuration of Communication Terminal> FIG. 4 is a block diagram illustrating a hardware configuration of communication terminal 40 shown in FIG. As shown in FIG.
Has a wireless communication unit 401, an operation input unit 402, a liquid crystal display unit 403, a storage unit 404, and a CPU 408, and these units are connected by a bus 409.
The storage unit 404 includes a ROM 405 and a RAM 406.
And a non-volatile memory 407 such as an SRAM, an EEPROM or a hard disk.

The wireless communication section 401 controls wireless communication with the base station 30. This wireless communication unit 401
Under the control of the CPU 408, generates a wireless signal on which, for example, packet data is superimposed and transmits the wireless signal to the base station 30. In addition, the wireless communication unit 401 receives a wireless signal such as a beacon transmitted from the base station 30, demodulates the wireless signal, and control bit data included in the beacon,
The packet data addressed to the own device 40 is obtained.

The operation input section 402 is provided with a keyboard for inputting characters and operation instructions, a pointing device, etc., and outputs an operation signal corresponding to the operation of these input devices.
Output to the PU 408. Further, the liquid crystal display unit 403 has a liquid crystal display panel and a drive circuit for performing display control of this liquid crystal display panel.

The ROM 405 stores programs and the like that control the basic control of each unit of the communication terminal 40. RAM
406 is used as a work area of the CPU 408, and temporarily stores programs executed by the CPU 408 and various data. A backoff time storage area 406a is provided in the RAM 406. Backoff time data used by the communication terminal 40 to transmit data to the base station 30 is stored in the backoff time storage area 406a.

The non-volatile memory 407 stores various programs and data such as an operating system and application programs for the communication terminal 40. The non-volatile memory 407 has a backoff time table 407a. In the backoff time table 407a, as shown in FIG. 5, a plurality of types of backoff time data are stored in association with the control bit data. In the example shown in the figure, for example, the control bit data “0” is associated with the backoff time data “25”, and the control bit data “1” is associated with the backoff time data “40”. There is.

Here, the back-off time (waiting time) is the time from when the communication terminal 40 transmits a frame to the base station 30 until the next frame can be transmitted, as described above. Now, when a plurality of communication terminals 40 in the same basic service area 35 share a wireless channel and perform wireless communication with the base station 30, if the backoff time is set to a sufficiently large value, the communication terminals 40 will be Another communication terminal 40 that shares the wireless channel in the backoff period from the transmission of a frame to the transmission of the next frame.
Can send frames.

However, if the amount of backoff time is fixed to a sufficiently large value, the same basic service area 3
When the number of communication terminals 40 in 5 is small, that is, when the number of communication terminals 40 sharing a wireless channel is small, the throughput of the wireless channel decreases, and the time required for data transmission of the communication terminal 40 is large. Loss will be included.

Therefore, in the present invention, an appropriate amount of backoff time is set according to the number of communication terminals 40 in the basic service area 35. More specifically, when the number of communication terminals 40 in the basic service area 35 is small, the number of other communication terminals 40 that try to transmit the frame is small in the above-described backoff period. It is not necessary to set the amount of off time to a very large value. On the other hand, when the number of communication terminals 40 in the basic service area 35 is large, the number of other communication terminals 40 that try to transmit the frame in the above-mentioned backoff period is also large, so It is necessary to set the amount of backoff time to a larger value as compared with the case where the number is small. From the above,
The communication terminal 40 in the present embodiment performs data transmission to the base station 30 using a larger amount of backoff time as the number of communication terminals 40 located in the same basic service area 35 increases.

The backoff time data stored in the backoff time table 407a is not limited to the number of communication terminals 40 in the basic service area 35, for example, the maximum per transmission to the base station 30. DIFS (Distributed In) for frame interval and distributed control
ter frame space), PIFS (Point Int) for centralized control
er Frame Space), SIFS (Short Inte
r Frame Space) and other necessary times required for frame transmission.

Note that, for example, only the back-off time of DIFS is variably controlled, only the back-off time of PIFS is variably controlled, or the back-off time of SIFS used for an Ack response is fixed and DIFS and PIFS are fixed. Variable control of back-off time, DIF
It is possible to variably control all back-off times of S, DIFS, and PIFS.

Returning to FIG. 4, the CPU 408 has the storage unit 40.
By executing the various programs stored in No. 4, each unit of the apparatus connected via the bus 409 is controlled. The CPU 408 executes a beacon reception process (see FIG. 8) and a data transmission process (see FIG. 9) as processes unique to this embodiment. The above is the configuration of the wireless LAN 1 according to the present embodiment.

[A-2. Operation of Embodiment] Next, the operation of the present embodiment will be described. <1. Control bit determination process> First, the control bit determination process executed by the CPU 307 in the base station 30 will be described with reference to the flowchart shown in FIG. This control bit determination process is performed by the communication terminal 40 within the basic service area 35, for example, at regular intervals based on a timer interrupt or when a new communication terminal 40 enters the basic service area 35 of the base station 30. When it is detected that the number has increased or decreased, the CPU 30
7 is executed.

As shown in the figure, first, the base station 30
CPU 307 is the basic service area 35 of the own station 30.
The number of communication terminals 40 in the area is counted (step S101). For example, in FIG. 1, in the basic service area 35b of the base station 30b, the communication terminals 40b, 40
There are a total of 3 units of c and 40d. Therefore, in this case, the number of existing areas counted by the CPU 307 of the base station 30b is “3”.

Next, the CPU 307 acquires control bit data corresponding to the counted number of existing areas from the control bit table 305a of the non-volatile memory 305 (step S1).
02), and stores the acquired control bit data in the control bit storage area 304a of the RAM 304 (step S10).
3), the control bit determination process ends. For example, if the number of resident areas counted in step S101 is “3”,
The CPU 307 uses the control bit table 3 shown in FIG.
The control bit data “0” corresponding to the number of resident areas “3” is read from 05a, and the storage data in the control bit storage area 304a is updated to the control bit data “0”.

As described above, the control bit data is information designating any one of a plurality of types of backoff time data stored in the non-volatile memory 407 of the communication terminal 40. Further, as can be seen from the control bit table 305a shown in FIG. 3, the control bi that specifies a larger amount of time for the backoff time as the number of resident areas increases.
t data is selected. Therefore, by this control bit determination process, the CPU 307 of the base station 30 causes each communication terminal 40 existing in the basic service area 35 of the own station 30 to perform communication.
Of the communication terminal 40 in the basic service area 35 is determined so that the larger the number of existing areas, the larger the amount of time.

<2. Beacon transmission process> Next, the base station 3
The beacon transmission process executed by the CPU 307 at 0 will be described with reference to the flowchart shown in FIG. This beacon transmission process is executed by the CPU 307 at regular intervals based on a timer interrupt, for example.

As shown in the figure, first, the base station 30
The CPU 307 reads out the control bit data stored in the control bit storage area 304a (step S2).
01). Next, the CPU 307 reads the control bi
The beacon signal data including the t data is generated (step S202). Here, in addition to the control bit data, the beacon signal data includes, for example, synchronization establishment information for establishing synchronization with each other for the plurality of communication terminals 40 in the basic service area 35. I'm out.

The CPU 307 then executes the above step S
The beacon signal data generated in 202 is transmitted to the wireless communication unit 306 (step S203). The wireless communication unit 306 generates a beacon based on the beacon signal data received from the CPU 307, and when the transmission timing comes, transmits the beacon in the basic service area 35. For example, when the control bit data “0” is stored in the control bit storage area 304a, the CPU 30
7, the signal data for the beacon including the control bit data “0” is generated, and the wireless communication unit 306 controls the control bi.
A beacon including t data “0” is transmitted.

After the beacon transmission is completed, the wireless communication section 306 also transmits to the CPU 307 a transmission completion notification indicating that the beacon transmission has been completed. Upon receiving the transmission completion notification from the wireless communication unit 306 (step S204), the CPU 307 ends the beacon transmission process.

By this beacon transmission processing, the CPU 307 of the base station 30 can transmit control bit data designating the back-off time to the communication terminal 40 in the basic service area 35 by beacon. In this way, since only the control bit data needs to be included in the beacon for transmission, the amount of transmission data can be reduced compared to the case where the backoff time data itself is included in the beacon and transmitted.

<3. Beacon Reception Processing> Next, the beacon reception processing executed by the CPU 408 in the communication terminal 40 will be described with reference to the flowchart shown in FIG. This beacon reception processing is performed by the CPU 4 when the communication terminal 40 receives the beacon transmitted from the base station 30.
08.

Note that, for example, the base station 30 shown in FIG.
In the case where the basic service area 35a of a and the basic service area 35b of the base station 30b partially overlap, the communication terminal 40 located in the overlapping area receives a beacon from both the base station 30a and the base station 30b. Has
The CPU 408 selects a beacon having a strong radio wave intensity from the received beacons, and transmits the beacon from the base station 30 that is the transmission source of the beacon.
Is determined as the base station 30 to access, and beacon reception processing is executed for the selected beacon.

As shown in the figure, first, the communication terminal 4
The CPU 408 of 0 uses the information for synchronization establishment contained in the beacon received and demodulated by the wireless communication unit 401 to establish synchronization with another communication terminal 40 within the same basic service area 35 (step T101).

Next, the CPU 408 controls the wireless communication section 40.
The control bit data included in the beacon received and demodulated by 1 is extracted (step T102). Then, the CPU 408 acquires backoff time data corresponding to the extracted control bit data from the backoff time table 407a of the non-volatile memory 407 (step T103). After that, the CPU 408 stores the acquired backoff time data in the backoff time storage area 406a of the RAM 406 (step T104), and ends the beacon reception process.

For example, when the control bit data "0" is included in the beacon received from the base station 30, the CPU 408 of the communication terminal 40 uses the control bit from the backoff time table 407a shown in FIG. 5 in step T103. Data “0” Corresponding back-off time data “2”
5 "is read out, and C is read at step T104.
The PU 408 updates the data stored in the backoff time storage area 406a to the backoff time data “25”. As a result, the backoff time used in the data transmission process (see FIG. 9) is set to 25 μs.

As described above, the CPU 408 of the communication terminal 40 sets the backoff time of its own terminal 40 according to the control bit data included in the beacon received from the base station 30 by the beacon reception processing.

<4. Data transmission process> Next, the communication terminal 4
The data transmission processing executed by the CPU 408 at 0 will be described with reference to the flowchart shown in FIG. 9 and the schematic diagrams shown in FIGS. 10 and 11. This data transmission process is executed by the CPU 408 when the communication terminal 40 transmits data to the base station 30.

As shown in the figure, first, the communication terminal 4
The CPU 408 of 0 executes carrier sense of the wireless channel before transmitting the frame to the base station 30 (step T201), and another communication terminal 40 is transmitting the frame to the base station 30 using the wireless channel. Or not,
That is, it is determined whether or not the wireless channel is in the idle state (step T202).

As a result of carrier sense, the CPU 408
If you determine that the wireless channel is not idle,
After clearing the timer counter, the timer counter is used to start measuring time t (step T203).
Then, the CPU 408 determines whether or not the measured time t reaches the transmission postponement time T1 stored in advance in the non-volatile memory 407 (step T204), and when the measured time t reaches the transmission postponement time T1, the frame In order to perform the transmission, the process returns to step T201, and carrier sense is started again.

On the other hand, when the CPU 408 determines that the wireless channel is in the idle state as a result of the carrier sense, it executes frame transmission (step T205),
After the transmission of the frame is completed, it is determined whether or not the next frame is transmitted (step T206).

When the CPU 408 determines that there is a next frame to be transmitted, it clears the timer counter and then starts counting the time t using the timer counter (step T207). Then, the CPU 408
It is determined whether or not the measured time t reaches the backoff time T2 stored in the backoff time storage area 406a (step T208), and the measured time t is the backoff time T.
When the number reaches 2, the process returns to step T201 to transmit the next frame, and carrier sense is started.

On the other hand, the CPU 408 executes the above step T2.
When it is determined that the next frame is not transmitted in 06,
That is, when the transmission of all frames is completed, the data transmission process is completed.

10 and 11 are schematic diagrams illustrating a case where each of a plurality of communication terminals 40 located in the same basic service area 35 executes the above-described data transmission processing and transmits data to the base station 30. It is a figure.

Here, FIG. 10 shows the basic service area 3
5 communication terminals 40a, 40b, 40c, 40d in total
The figure shows a case where a total of three communication terminals 40a, 40b, 40c excluding the communication terminal 40d are transmitting data to the base station 30. In addition, in FIG. 11, a total of two communication terminals 40a and 40b are present in the basic service area 35.
This shows a case where one communication terminal 40a, 40b is transmitting data to the base station 30.

First, the operation of the base station 30 and each of the communication terminals 40a-40d will be described with reference to FIG. In the example shown in the figure, the communication terminal 40d that does not perform data transmission
Although not shown, a total of four communication terminals 40a to 40d are present in the basic service area 35. Therefore, the CPU 307 of the base station 30 reads out the control bit data “1” corresponding to the number of resident areas “4” from the control bit table 305a shown in FIG. Send.

CPU 408 of each communication terminal 40a-40d
When the beacon is received, the corresponding backoff time data “40” is read from the backoff time table 407a shown in FIG. 5 according to the control bit data “1” included in this beacon, and the backoff time is set to 40 μs.
Set to. In this way, the same basic service area 3
The communication terminals 40a to 40d located in the area 5 set the same backoff time designated by the base station 30. In addition, in FIG. 10, the back-off time is described as T2a.

Each of the communication terminals 40a to 40d has, for example, a timing at which data transmission is instructed by the user.
The data transmission process is started at each arbitrary timing. In the example shown in FIG. 10, a total of three communication terminals 40a, 40b, 40c excluding the communication terminal 40d perform data transmission processing to the base station 30, and first, the communication terminal 40a starts data transmission processing. However, prior to the transmission of the frame, the carrier sense of the wireless channel (CS
To indicate).

In the figure, at the timing when the communication terminal 40a performs the first carrier sense, the other communication terminals 40b to 40d have not yet transmitted the frame.
The radio channel is idle. Therefore, the communication terminal 40a transmits the frame, and when the transmission of the frame is completed, the communication terminal 40a transmits the next frame.
Wait for the backoff time T2a specified by Then, the communication terminal 40a has the backoff time T2a.
When elapses, the next frame is transmitted and carrier sense is started. Thereafter, the communication terminal 40a similarly executes frame transmission one after another.

Further, the communication terminal 40b detects the carrier sense of the radio channel based on the start of the data transmission process as shown in FIG.
As shown in 0, this is performed during the period when the communication terminal 40a is transmitting the first frame. Of course, at this timing, since the communication terminal 40a is transmitting the frame, the communication terminal 40b temporarily suspends the carrier sense and waits for the transmission delay time T1, and when the transmission delay time T1 elapses, the frame is transmitted. , Do carrier sense again.

As a result of the carrier sense, when it is detected that the wireless channel is in the idle state, the communication terminal 40
b transmits the frame and backoff time T
After waiting for 2a, carrier sense for transmitting the next frame is performed. Then, thereafter, the communication terminal 40b
Similarly, frame transmission is performed one after another. The communication terminal 40c is also the communication terminal 40 described above.
Frames are sequentially transmitted as shown in FIG. 10 in accordance with the same transmission procedure as a and 40b.

As described above, each communication terminal 40a, 4
As a result of the data transmission processing being performed in 0b and 40c, the communication terminals 40a and 40 on the wireless channel
As shown in the lowermost part of FIG. 10, the transmission frames of b and 40c are not evenly distributed to the transmission frames of the specific communication terminal 40, and the transmission frames of the communication terminals 40a, 40b, and 40c are evenly distributed. . That is, even when a plurality of communication terminals 40a, 40b, 40c share a wireless channel for communication, the specific communication terminal 40 does not occupy the wireless channel. Therefore, it is possible to equally give the frame transmission opportunity to the plurality of communication terminals 40 sharing the wireless channel. In other words, a fair access right to the base station 30 can be provided to the plurality of communication terminals 40 sharing the wireless channel.

On the other hand, FIG. 11 shows the basic service area 35.
2 shows a case where a total of two communication terminals 40a and 40b are present and the two communication terminals 40a and 40b are transmitting data to the base station 30. In the example shown in the figure, since two communication terminals 40a and 40b are located in the basic service area 35, the CPU 307 of the base station 30 controls the control bit shown in FIG.
Control bi corresponding to the number of resident areas “2” from the table 305a
The t data “0” is read out, included in the beacon, and transmitted into the basic service area 35.

CPU 408 of communication terminals 40a and 40b
When receiving the beacon, the corresponding backoff time data “25” is read from the backoff time table 407a shown in FIG. 5 according to the control bit data “0” included in the beacon, and the backoff time is set to 25 μs.
Set to. In addition, in FIG. 11, the back-off time is described as T2b. Further, the procedure of the frame transmission processing of the communication terminals 40a and 40b in the same figure is the same as that shown in FIG.

By the way, the case of FIG. 10 and the case of FIG. 11 differ in the backoff time from when each communication terminal 40 completes the transmission of a frame until the next frame can be transmitted. In the case of FIG. 10, the back-off time T2a is 40 μs because the number of in-zones is “4”, and in the case of FIG. 11, the back-off time T2b is 25 μs because the number of in-zones is “2”. As a result, as can be seen by comparing FIG. 10 and FIG. 11, when the communication terminal 40 transmits the same total amount of frames, the amount of backoff time in FIG. The time required is short. As described above, in this embodiment, by appropriately changing the amount of backoff time according to the number of existing areas, equalization of transmission opportunities of frames of a plurality of communication terminals 40 sharing a wireless channel can be performed. Can be realized without lowering the throughput. Therefore,
It is possible to minimize unnecessary time from the time required for data transmission of each communication terminal 40.

Since the beacon is transmitted, for example, at a cycle of several times per second, the base station 30 immediately determines the back-off time of the communication terminal 40 in accordance with the number of resident areas which changes from moment to moment. It can be changed to an appropriate amount of time. Therefore, it goes without saying that, for example, the back-off time of each communication terminal 40 can be immediately changed according to the increase or decrease in the number of located areas during the series of data transmission processing shown in FIG. 10 or 11.

[B. Modification] Although the embodiment of the present invention has been described above, this embodiment is merely an example, and various modifications can be made without departing from the spirit of the present invention. For example, the following may be considered as modifications.

<Modification 1> In the above embodiment, the base station 3
The backoff time is determined according to the number of communication terminals 40 in the basic service area 35 of 0.
However, for example, even if the number of communication terminals 40 in the basic service area 35 is 20, the communication that is actually transmitting data to the base station 30 among the 20 communication terminals 40. There may be a case where the number of terminals 40 is one. In such a case, if the back-off time is determined only by the number of existing areas, the throughput of the wireless channel is reduced, and the time required for the data transmission of the communication terminal 40 includes many losses.

Therefore, the base station 30 is
Of the communication terminals 40 located in the basic service area 35, the number of communication terminals 40 that are actually transmitting data to the base station 30, that is, the number of communication terminals 40 that are accessing the base station 30 The back-off time may be detected and the back-off time may be determined according to the detected number of communication terminals 40.

In addition, the base station 30 is further provided with a function of detecting the throughput of the radio channel, and the base station 30 backs off according to the number of communication terminals 40 in the basic service area 35 and the throughput of the radio channel. The time may be determined. Basic service area 3
If the throughput of the wireless channel is low even if the number of communication terminals 40 within 5 is large, the basic service area 3
It can be considered that the number of the communication terminals 40 actually transmitting data to the base station 30 is smaller than the number of the communication terminals 40 within 5 areas. Therefore, by reducing the time amount of the back-off time determined according to the number of existing areas within a range in which the equalization of the transmission opportunity of the frame can be sufficiently maintained in consideration of the throughput of the wireless channel, Unnecessary time can be saved as much as possible from the time required for data transmission.

<Modification 2> In the above embodiment, the base station 3
Control b that specifies the backoff time from 0 to the communication terminal 40
It is configured to send it data. However, the backoff time data itself is transmitted from the base station 30 to the communication terminal 4
Of course, it may be configured to transmit to 0. When the backoff time data itself is transmitted from the base station 30 to the communication terminal 40, the base station 30
The back-off time data may be calculated by calculation from the number of communication terminals 40 in the basic service area 35 and the throughput of the wireless channel. With such a configuration, it becomes possible to set a more optimal backoff time according to the number of resident areas and the throughput of the wireless channel.

Furthermore, when transmitting the control bit data and the backoff time data itself from the base station 30 to the communication terminal 40, it goes without saying that a radio signal other than the beacon may be used.

<Modification 3> In the above embodiment, when the wireless channel is not in the idle state as a result of the carrier sense, the carrier sense is temporarily stopped, and the frame is transmitted after waiting for a predetermined transmission delay time. The so-called waiting-type CSMA / that starts carrier sense
The case where the present invention is applied to the CA method has been described.

However, according to the present invention, for example, when the wireless channel is not in the idle state as a result of the carrier sense, or when the wireless channel is in the idle state by continuing the carrier sense, the wireless channel waits for the amount of time determined by the probability. Of course, the present invention is also applicable to a so-called P-immediate type CSMA / CA system, which starts carrier sense for transmitting a frame later.

<Modification 4> In the above embodiment, the backoff time of the communication terminal 40 is determined by the base station 30. However, for example, the base station 30 uses the communication terminal 40 within the basic service area 35 of the base station 30.
The number of resident areas is counted and information indicating the counted number of resident areas itself or the level of the number of resident areas (for example, the number of resident areas is 1 to 3 for level 1 and the number of resident areas is 4 to 7 for level 2). Etc.) to the communication terminal 40, and the communication terminal 40 may determine the back-off time according to the information indicating the number of existing areas or the level of the number of existing areas received from the base station 30.

In this case, the method of determining the back-off time is, as described in the above embodiment, one of the back-off time data prepared in advance, whichever one of the back-off times is selected in accordance with the information regarding the number of existing areas. A method of selecting the off-time data, a method of calculating the back-off time data by calculation from the information on the number of resident areas, and the like are possible.
Further, a function of detecting the throughput of the wireless channel is added to the base station 30, and the base station 30 transmits the information regarding the number of resident areas and the information regarding the throughput of the wireless channel to the communication terminal 40. The backoff time may be determined according to the information on the number of resident areas and the information on the throughput of the wireless channel received from the station 30.

<Fifth Modification> In the above embodiment, the case where the present invention is applied to the wireless LAN has been described. However, the present invention is, for example, CSMA as a media access control system.
It can also be applied to a wired LAN adopting the method.

In this case, the base station 30 described in this embodiment corresponds to, for example, an access point.
The access point has a function of counting the number of communication terminals accessing the access point and a function of detecting the throughput in the wired communication section shared by the communication terminals under the control of the access point. The backoff time of the communication terminal is determined according to the number of communication terminals being accessed and the throughput of the wired communication section obtained by the function, and information regarding the determined backoff time is transmitted to the communication terminal. Then, the communication terminal sets the backoff time according to the information regarding the backoff time received from the access point, and transmits data to the access point.

As described in Modification 4, the access point counts the number of communication terminals (the number of terminals) accessing the access point, and counts the number of terminals itself or the level of the number of terminals. Is transmitted to the communication terminal, and the access point 3 is transmitted at the communication terminal.
It goes without saying that the backoff time may be determined according to the number of terminals received from 0 or information indicating the level of the number of terminals.

[0093]

As described above, according to the present invention, data transmission opportunities of a plurality of communication terminals sharing a transmission line are
Equalization can be achieved without reducing the throughput of the transmission path.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a wireless LAN including a base station and a communication terminal according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a hardware configuration of a base station according to the same embodiment.

FIG. 3 is a diagram illustrating a data configuration of a control bit table stored in a nonvolatile memory in the base station according to the same embodiment.

FIG. 4 is a block diagram illustrating a hardware configuration of the communication terminal according to the embodiment.

FIG. 5 is a diagram illustrating a data configuration of a back-off time table stored in a nonvolatile memory in the communication terminal according to the same embodiment.

FIG. 6 is a diagram illustrating a flowchart of a control bit determination process executed by a CPU in the base station according to the same embodiment.

FIG. 7 is a diagram illustrating a flowchart of beacon transmission processing executed by a CPU in the base station according to the embodiment.

FIG. 8 shows a CPU in the communication terminal according to the embodiment.
It is a figure which illustrates the flowchart of the beacon reception process performed by.

FIG. 9 shows a CPU in the communication terminal according to the embodiment.
It is a figure which illustrates the flowchart of the data transmission process performed by.

FIG. 10 is a diagram for explaining a case in which each of a plurality of communication terminals existing in a basic service area executes the data transmission process shown in FIG. 9 and transmits data to a base station according to the embodiment. It is a schematic diagram (the 1).

FIG. 11 is a diagram for explaining a case in which each of a plurality of communication terminals existing in a basic service area executes the data transmission process shown in FIG. 9 and transmits data to a base station according to the embodiment. It is a schematic diagram (the 2).

[Short description of code] 1 ... Wireless LAN, 10 ... Gateway server, 20
... control server, 30a, 30b ... base station,
35a, 35b ... Basic service area, 36 ... Extended service area, 40a-40d ... Communication terminal, 301
...... Wired communication interface, 302 …… Storage unit, 30
3 ... ROM, 304 ... RAM, 304a ... Control b
it storage area, 305 ... Non-volatile memory, 305a ...
... control bit table, 306 ... wireless communication unit, 307
... CPU, 308 ... bus, 401 ... wireless communication unit,
402 ... Operation input unit, 403 ... Liquid crystal display unit, 404
...... Memory unit, 405 ... ROM, 406 ... RAM, 4
06a ... back-off time storage area, 407 ... nonvolatile memory, 407a ... back-off time table, 40
8 ... CPU, 409 ... Bus.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5K033 AA01 CA06 CB01 CB06 DA01                       DA03 DA17 DB18 EA07 EC01                       EC02                 5K048 AA16 DB01 DC01 EA11 EB13                       FC01 HA01 HA02 HA37                 5K067 AA13 CC08 DD25 DD30 EE02                       EE10 EE22 FF05 HH23 JJ62

Claims (27)

[Claims] 1. A counting process in which the communication device counts the number of communication terminals capable of receiving signals transmitted from the communication device and capable of transmitting data to the communication device, and the number of devices counted in the counting process. A signal transmitting step in which the communication device transmits a signal based on the signal to the communication terminal, a receiving step in which the communication terminal receives the signal transmitted in the signal transmitting step, and the signal receiving step in the receiving step Based on the signal, the communication terminal determines a waiting time from when data is transmitted to the communication device until it becomes possible to transmit the next data to the communication device, and the waiting time is sent to the communication device according to the waiting time. And a transmission control process for transmitting data. 2. In the signal transmitting process, the communication device obtains the waiting time of the communication terminal based on the number of devices counted in the counting process, and sends a signal notifying the waiting time to the communication terminal. The transmission control method according to claim 1, wherein the transmission is performed. 3. The communication device further comprises a detection step of detecting the throughput of a transmission line shared by the communication terminals for transmitting data to the communication device, wherein the signal transmission step comprises the communication device. Is to obtain the waiting time of the communication terminal based on the number of devices counted in the counting process and the throughput detected in the detecting process, and transmit a signal notifying the waiting time to the communication terminal. The transmission control method according to claim 2, wherein 4. The transmission control method according to claim 1, wherein, in the signal transmission process, the communication device transmits a signal for notifying the number of units counted in the counting process to the communication terminal. 5. The communication device further comprises a detection step of detecting the throughput of a transmission line shared by the communication terminals for transmitting data to the communication device, wherein the signal transmission step comprises the communication device. 5. The transmission control method according to claim 4, wherein a signal notifying the number of vehicles counted in the counting step and the throughput detected in the detecting step is transmitted to the communication terminal. 6. The transmission control method according to claim 1, wherein the communication device wirelessly transmits the signal in the signal transmission process. 7. The communication device periodically transmits the signal in the signal transmitting process.
The described transmission control method. 8. The transmission control method according to claim 6, wherein, in the signal transmission process, the communication device broadcasts the signal in a wireless area covered by the communication device. 9. The method according to claim 6, wherein in the counting step, the communication device counts the number of the communication terminals in a wireless area covered by the communication device.
The transmission control method according to claim 1. 10. The communication device in the counting step,
The transmission control method according to claim 1, wherein the number of communication terminals transmitting data to the communication device is counted. 11. The standby time in the transmission control process, wherein the communication terminal has a larger amount of time as the number of units counted in the counting process is larger based on the signal received in the receiving process. 2. The transmission control method according to claim 1, further comprising the step of obtaining the data, and transmitting the data to the communication device according to the waiting time. 12. A communication system comprising a communication device and a communication terminal capable of transmitting data to the communication device, wherein the communication device is capable of receiving a signal transmitted from the communication device. And a signal transmitting unit that transmits a signal based on the number of units counted by the counting unit to the communication terminal, wherein the communication terminal receives the signal transmitted by the signal transmitting unit. Based on the signal received by the receiving unit and the receiving unit to determine the waiting time from the transmission of data to the communication device until the next data can be transmitted to the communication device,
A transmission control means for transmitting data to the communication device according to the waiting time. 13. A counting unit for counting the number of communication terminals capable of receiving a signal transmitted from the communication device and capable of transmitting data to the communication device, and a signal for notifying the number of the communication terminals counted by the counting unit. Generating means for generating, and a waiting time from when the communication terminal transmits data to the communication device to the signal generated by the generating means until it becomes possible to transmit the next data to the communication device. A communication device, comprising: transmitting means for transmitting to the communication terminal as information required by the communication terminal. 14. The number of units counted by the counting unit is further included in a detection unit that detects a throughput of a transmission line shared by the communication terminals for transmitting data to the communication device. 14. The communication device according to claim 13, wherein the communication device generates a signal for informing of the throughput detected by the detecting means. 15. Counting means for counting the number of communication terminals capable of receiving a signal transmitted from the communication device and capable of transmitting data to the communication device; and based on the number counted by the counting means, A generation unit that obtains a standby time from when the communication terminal transmits data to the communication device until it becomes possible to transmit the next data to the communication device, and generates a signal that notifies the standby time, A communication device comprising: a transmission unit that transmits the signal generated by the generation unit to the communication terminal. 16. The number of units counted by the counting unit is further included in a detection unit that detects throughput of a transmission path shared by the communication terminals for transmitting data to the communication device. 16. The communication apparatus according to claim 15, wherein the waiting time of the communication terminal is obtained based on the throughput detected by the detecting means and the signal notifying the waiting time is generated. 17. The generating means obtains the waiting time, which becomes a larger amount of time as the number of units counted by the counting means increases, and generates a signal notifying the waiting time. Item 15. The communication device according to Item 15. 18. The communication device according to claim 13, wherein the transmitting unit wirelessly transmits the signal generated by the generating unit. 19. The communication device according to claim 18, wherein the transmitting means periodically transmits the signal. 20. The communication device according to claim 18, wherein the transmission means broadcasts the signal in a wireless area covered by the communication device. 21. The communication device according to claim 18, wherein the counting unit counts the number of the communication terminals in a wireless area covered by the communication device. 22. The communication device according to claim 13, wherein the counting unit counts the number of the communication terminals transmitting data to the communication device. 23. Receiving means for receiving a signal from a communication device housing the communication terminal under control of the number of communication terminals under the control of the communication device, and a signal received by the receiving means. Deciding means for deciding a waiting time from when the communication terminal transmits data to the communication device until it becomes possible to transmit the next data to the communication device, based on the number of units indicated by, And a transmission control means for transmitting data to the communication device according to the standby time determined by the means. 24. The receiving means comprises:
The number of communication terminals housed under this communication device,
The communication terminals share a signal, and receive a signal notifying the throughput of a transmission path for transmitting data to the communication device, and the determining means is the number of units indicated by the signal received by the receiving means and the 24. The communication terminal according to claim 23, wherein the waiting time is determined based on throughput. 25. The deciding means decides, based on the number of vehicles indicated by the signal received by the receiving means, a larger amount of the waiting time as the number of vehicles increases. Item 23. A communication terminal. 26. A waiting time from a communication device that houses the communication terminal under control until the communication terminal can transmit the next data to the communication device after transmitting the data to the communication device. Receiving means for receiving a signal for informing, a determining means for determining the standby time of the communication terminal according to the signal received by the receiving means, and data to the communication device according to the standby time determined by the determining means. A communication terminal, comprising: a transmission control unit for transmitting. 27. The communication terminal according to claim 23, wherein the communication terminal uses a CSMA method as a media access control method.