JPH06169312A - Communication controller - Google Patents

Abstract

PURPOSE:To optimize the transmission delay time of a communication controller in accordance with the using state of a communication circuit and to improve the throughput of a radio LAN, etc., which applies a contention system by providing such a communication controller that can evade too much collisions of communication circuits when the large load is applied to these circuits and can quickly catch an idle communication circuit when the small load is applied to the communication circuit respectively. CONSTITUTION:A wait time type CSMA system is used as a circuit access system of a radio LAN, etc., applying a contention system. Then the maximum transmission delay time of a communication controller is selectively set in a step ST2 in response to the using state, i. e., the carrier detection rate, etc., of a communication circuit. Thus the maximum transmission delay time is increased when the carrier detection rate is large and the large load is applied to the communication circuit. So that too much collisions of communication circuits can be evaded. Meanwhile the maximum transmission delay time is reduced when the carrier detection rate is small and the small load is applied to the circuit. So that an idle communication circuit can be quickly caught.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control device,
For example, a wireless LAN (Loc
al Area Network) as well as a technology that is particularly effective when used for a transmission / reception buffer thereof.

[0002]

2. Description of the Related Art There is a so-called wireless LAN which uses a wireless line as a communication line. The wireless LAN includes a plurality of host computers and input / output devices that are connected to a wireless line via corresponding host-side transmission / reception buffers or input / output device-side transmission / reception buffers. The host side transmission / reception buffer and the input / output device side transmission / reception buffer function as a communication control device, and have a function of monitoring the usage state of the wireless line and capturing it as necessary.

On the other hand, when a common communication line such as a wireless line is accessed by a plurality of stations, there is a so-called contention system in which each station performs a link process for capturing the communication line and taking measures against congestion. Further, as a means for increasing the throughput of a communication system adopting such a contention system, a so-called immediate type in which the usage state of a communication line is monitored depending on the presence or absence of a carrier (carrier signal) and the communication line is immediately captured when there is no carrier. CSMA (Car
rier Sense Multiple Acces
s) method and so-called waiting type C in which the transmission delay time of each station is set by random number generation when the communication line becomes idle
There is an SMA method.

The immediate CSMA system and the standby CSMA system are described, for example, in 1984, "Introduction to Local Area Neck Work", pages 121 to 124, issued by Modern Science Co., Ltd.

[0005]

Prior to the present invention, the inventors of the present application have adopted a contention type wireless LAN.
, And considered adopting the immediate or standby CSMA method as the line access method. However, the former has a problem that excessive collisions are caused especially when many stations, that is, transmission / reception buffers desire transmission and the load on the wireless line is large, and the throughput of the system reaches a peak. In the latter case, step S in FIG.
As shown in T32, the transmission delay time is determined by random number generation within a fixed maximum value range, so that the transmission delay time may unnecessarily increase even if the load on the wireless line is small. ,
There is a problem that the wireless line in the idle state cannot be quickly accessed.

An object of the present invention is to prevent excessive collision when the load on the communication line is large, and to quickly catch the communication line in the idle state when the load on the communication line is small. To provide. Another object of the present invention is to optimize the transmission delay time of the communication control device according to the usage status of the communication line, and increase the throughput of a wireless LAN or the like adopting the contention system.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0008]

The outline of the representative one of the inventions disclosed in the present application will be briefly described as follows. That is, the standby CSMA method is adopted as a line access method for a wireless LAN or the like that adopts the contention method, and the maximum value of the transmission delay time of the communication control device is
It is selectively set according to the usage status of the communication line, that is, the carrier detection rate or the number of communication frames or the number of communication stations per unit time.

[0009]

According to the above means, when the load on the communication line is large, the maximum value of the transmission delay time can be increased to avoid excessive collision, and when the load on the communication line is small, the transmission can be performed. By reducing the maximum value of the delay time, it is possible to quickly capture a communication line that has become idle. This optimizes the transmission / reception buffer, that is, the transmission delay time of the communication control device, according to the usage status of the communication line,
Throughput of a wireless LAN or the like that adopts the contention method can be increased.

[0010]

1 is a system configuration diagram of an embodiment of a wireless LAN including a communication control device (transmission / reception buffer) to which the present invention is applied. First, an outline of the system configuration and operation of the wireless LAN of this embodiment will be described with reference to FIG.

In FIG. 1, the wireless LAN of this embodiment
Are m host computers HCOM1 to HCOMm
And n input / output devices IOD1 to IODn.
Of these, the host computers HCOM1 to HCOMm
Is a so-called intelligent terminal such as a workstation and is connected to the wireless line RL via the corresponding communication control device, that is, the host side transmission / reception buffers HBUF1 to HBUFm. On the other hand, the input / output device IOD1
˜IODn are input devices or output devices such as laser printers and XY plotters that are compatible with the Centronics interface, and correspond to corresponding communication control devices, that is, input / output device side transmission / reception buffers DBUF1 to DBUFn.
Is connected to the wireless line RL via.

Host computers HCOM1 to HCOM
The m executes a predetermined arithmetic processing and stores the result in a built-in storage device. These calculation results are output from the corresponding host-side transmission / reception buffers HBUF1 to HBUFm via the wireless line RL, and designated by the arbitrary input / output device IOD1.
~ Output to IODn.

Host side transmission / reception buffers HBUF1 to HB
UFm and input / output device side transmission / reception buffer DBUF1
~ DBUFn acts as a communication control device, and monitors the use state of the wireless line RL depending on the presence / absence of a carrier. Then, according to the instructions of the host computers HCOM1 to HCOMm, the corresponding host computer is connected to the designated input / output devices IOD1 to IODn and the corresponding input / output device side transmission / reception buffers DBUF1 to DBUFn to connect the host computer and the input / output devices. Controls data exchange between output devices. At this time, the host side transmission / reception buffer and the input / output device side transmission / reception buffer coupled via the wireless line RL process control data and communication data exchanged between the corresponding host computer and the input / output device according to a predetermined protocol. Then, modulation / demodulation is performed according to a predetermined carrier.

In this embodiment, the wireless LAN adopts a contention system, and link processing for accessing the wireless line RL is left to each station connected to the wireless line RL, that is, each transmission / reception buffer. Therefore, as described above, the host-side transmission / reception buffers HBUF1 to HBUFm and the input / output device-side transmission / reception buffers DBUF1 to DBUFn act as communication control devices, respectively, and it is necessary to monitor the use state of the wireless line RL depending on the presence or absence of a carrier. In response, it has a function of capturing and accessing the wireless line RL.
Further, the wireless LAN of this embodiment adopts a waiting CSMA method as a retry method when access to the wireless line RL is congested by a plurality of host side or input / output device side transmission / reception buffers, and the wireless line RL becomes idle. After that, the transmission delay time from when access is restarted to each transmission / reception buffer is randomly determined within the maximum value specified by random number generation.

FIG. 2 is a partial block diagram of a first embodiment of the host side transmission / reception buffer HBUF1 included in the wireless LAN of FIG. An outline of the configurations and operations of the host side transmission / reception buffers HBUF1 to HBUFm and the input / output device side transmission / reception buffers DBUF1 to DBUFn will be described with reference to FIG. In the following description, the host side transmission / reception buffer HBUF1 will be taken as an example, but other host side transmission / reception buffers HBUF2 to HBU.
Fm and input / output device side transmission / reception buffer DBUF1
By analogy with DBUFn.

In FIG. 2, the host side transmission / reception buffer H
The BUF1 is not particularly limited, but is a central processing unit CPU of a stored program method and a storage device MEM coupled to the central processing unit CPU via an internal bus IBUS.
Also, a transmission data control unit TDC and a reception data control unit RDC are provided. Among them, the memory device MEM is used for temporarily storing the control program necessary for the operation of the central processing unit CPU, the calculation result thereof, communication data and the like.

Next, the transmission data control unit TDC serially converts the transmission data supplied in parallel via the internal bus IBUS, and adds a error check code and a control frame to these transmission data. Apply processing. The transmission data output from the transmission data control unit TDC is transmitted to the transmission line control unit TLC via the transmission delay unit TDL. The transmission delay unit TDL receives the carrier detection signal C supplied from the reception line control unit RLC.
D determines that the wireless line RL is in an idle state, generates a pseudo random number according to a predetermined algorithm, and transmits based on the generated random number and the carrier detection rate DR output from the carrier detection rate determination unit CDT. Determine the delay time. Then, the transmission line control unit TLC is activated at the time when this transmission delay time elapses after the availability of the radio line RL is determined, and the radio line RL is captured. The transmission line control unit TLC captures the radio line RL in accordance with an instruction from the transmission delay unit TDL, modulates the transmission data output from the transmission data control unit TDC with a predetermined carrier, and outputs the modulated transmission data to the radio line RL.

On the other hand, the reception data transmitted via the radio line RL is demodulated by the reception line control unit RLC and then transmitted to the reception data control unit RDC. Then, after being subjected to an error check, control frame extraction, address collation, etc. by the reception data control unit RDC, they are converted into parallel and output to the internal bus IBUS. In this embodiment, the reception line control unit RLC constantly monitors the carrier on the radio line RL even when the host side transmission / reception buffer HBUF1 is in the standby state, and based on this, monitors the use state of the radio line RL. Have a function. As a result, the carrier detection signal C supplied to the transmission delay unit TDL
D is selectively set to an effective level on the condition that a carrier exists on the radio line RL, in other words, on the condition that the radio line RL is in use by another transmission / reception buffer.

Host side transmission / reception buffer HB of this embodiment
The UF1 further includes a carrier detection rate determination unit CDT that receives the carrier detection signal CD. The carrier detection rate determination unit CDT is not particularly limited, but a timer circuit that forms a counter reset signal of a predetermined cycle based on a clock signal and a counter reset signal that resets the carrier detection signal CD to an effective level. At this time, it includes a counter circuit that counts up according to a clock signal, and a register that captures the count value immediately before the counter circuit is reset by the counter reset signal. The output signal of this register is supplied to the transmission delay unit TDL as the carrier detection rate DR. As a result, the output signal of the register, that is, the carrier detection rate DR
Corresponds to the rate at which the carrier detection signal CD is set to the effective level within the unit time, in other words, the rate at which the wireless line RL is in use.

FIG. 3 shows a processing flow chart of an embodiment of frame transmission processing in the host side transmission / reception buffer HBUF1 of FIG. The frame transmission processing of the host side transmission / reception buffers HBUF1 to HBUFm and the input / output device side transmission / reception buffers DBUF1 to DBUFn will be described with reference to FIG. In the following description, the host-side transmission / reception buffer HBUF1 is similarly taken as an example, but other host-side transmission / reception buffers HBUF2 to HB are used.
UFm and input / output device side transmission / reception buffer DBUF1
-Please analogize about DBUFn.

In FIG. 3, the transmission delay unit TDL of the host side transmission / reception buffer HBUF1 which is about to start frame transmission first determines in step ST1 whether or not there is a carrier on the radio line RL based on the carrier detection signal CD. At this time, when the carrier detection signal CD is set to the effective level, the transmission delay unit TDL considers that the radio line RL is in use by another transmission / reception buffer,
stand by.

On the other hand, when the carrier detection signal CD becomes invalid and the radio line RL becomes idle, the transmission delay unit T
DL captures the carrier detection rate DR output from the carrier detection rate determination unit CDT in step ST2,
Based on this, the state of use within the unit time immediately before the wireless line RL is determined, and the maximum value of the transmission delay time is selectively set. That is, when the carrier detection rate DR is a or less, the transmission delay unit TDL sets the maximum value of the transmission delay time to the minimum level 0, and the carrier detection rate DR is a + 1 to a + 1.
If it is within the range of b, it is set to the next level 1. Hereinafter, the maximum value of the transmission delay time is sequentially increased according to the carrier detection rate DR, and when the carrier detection rate DR is x or more, the maximum level X is set.

Next, the transmission delay unit TDL operates in step ST.
In 3, the pseudo random number is generated according to a predetermined algorithm, and the transmission delay time is randomly determined according to the generated random number and within the set maximum value range. After waiting for the transmission delay time determined in step ST4, the presence / absence of a carrier on the radio line RL based on the carrier detection signal CD is determined again in step ST5. As a result, when the wireless line RL is still in an idle state, the transmission delay unit TDL activates the transmission line control unit TLC to execute frame transmission, but the wireless line RL becomes in use within the transmission delay time. In this case, the process returns to step ST1 and the above process is repeated.

As described above, in the wireless LAN of this embodiment, the host side transmission / reception buffers HBUF1 to HBUFm and the input / output device side transmission / reception buffers DBUF1 to DBU are provided.
The radio link R is determined by the carrier detection rate determination unit CDT of Fn.
The carrier detection rate of L, that is, the usage thereof, is monitored, and the transmission delay unit TDL of the transmission / reception buffer which is about to start frame transmission determines the transmission delay time according to the output signal of the carrier detection rate determination unit CDT, that is, the carrier detection rate DR. Selectively set the maximum value of. As a result, when the carrier detection rate DR becomes a large value and the load on the wireless line RL serving as a communication line is large, the maximum value of the transmission delay time can be increased to avoid excessive collision and the carrier detection rate DR is small. When the load on the wireless line RL is small, the maximum value of the transmission delay time can be reduced to quickly acquire the idle wireless line RL. As a result, it is possible to optimize the transmission delay time of the transmission / reception buffer for starting frame transmission according to the usage status of the wireless line RL and increase the throughput of the wireless LAN.

FIG. 4 shows a partial block diagram of a second embodiment of the host side transmission / reception buffer HBUF1 included in the wireless LAN of FIG. 1, and FIG. 5 shows an embodiment of the frame transmission processing thereof. The processing flow diagram of is shown. Based on these drawings, the outline and characteristics of the second embodiment of the host side transmission / reception buffers HBUF1 to HBUFm and the input / output device side transmission / reception buffers DBUF1 to DBUFn to which the present invention is applied will be described. It should be noted that this embodiment basically follows the embodiments of FIGS. 2 and 3, and therefore, only the portions different from this will be described.

In FIG. 4, the host side transmission / reception buffer HBUF1 of this embodiment has a frame counting unit FRC in place of the carrier detection rate determination unit CDT of FIG. A frame detection signal FD is supplied from the reception data control unit RDC to the frame counting unit FRC, and its output signal is
The number of received frames FN is supplied to the transmission delay unit TDL. The transmission delay unit TDL further includes a reception line control unit RL.
The carrier detection signal CD is supplied from C.

In this embodiment, the reception data control unit R
As described above, the DC has the function of identifying the received frame, and temporarily sets the frame detection signal FD to the effective level every time the received frame is identified. Further, the frame counting unit FRC is not particularly limited, but a timer circuit that forms a counter reset signal of a predetermined cycle, a counter circuit that is reset by the counter reset signal and counts up according to the frame detection signal FD,
A register that captures the count value immediately before the counter circuit is reset by the counter reset signal.
The output signal of this register is supplied to the transmission delay unit TDL as the received frame number FN. As a result, the output signal of the register, that is, the number of received frames FN, corresponds to the rate at which received frames are detected on the wireless line RL within a unit time, in other words, the usage status of the wireless line RL.

The transmission delay unit TDL of the host side transmission / reception buffer HBUF1 which is about to start frame transmission is shown in FIG.
As shown in, the presence / absence of a carrier is determined in step ST11. Then, in step ST12, the number F of received frames output from the frame counting unit FRC.
After determining the use status of the radio line RL based on N and selectively setting the maximum value of the transmission delay time to level 0 to level X, a pseudo random number is generated in step ST13,
The transmission delay time is randomly determined according to the generated random number and within the set maximum value range. Thereafter, the transmission delay time determined in step ST14 is waited for, the presence or absence of a carrier on the radio line RL is again determined by the carrier detection signal CD in step ST15, and the transmission line control unit TLC is selectively activated to perform frame transmission. To execute.

As described above, in the wireless LAN of this embodiment, the host side transmission / reception buffers HBUF1 to HBUFm and the input / output device side transmission / reception buffers DBUF1 to DBU are provided.
The number of communication frames per unit time transmitted by the frame counting unit FRC of Fn, that is, the usage status thereof is monitored, and the transmission delay unit TDL of the transmission / reception buffer that attempts to start frame transmission is The maximum value of the transmission delay time is selectively set according to the output signal of the unit FRC, that is, the number of received frames FN. As a result, when the number of received frames FN is large and the load on the radio line RL is large, the maximum value of the transmission delay time can be increased to avoid excessive collision, and at the same time the number of received frames FN is a small value. When the load on the RL is small, it is possible to reduce the maximum value of the transmission delay time and quickly capture the vacant wireless line RL. As a result, it is possible to optimize the transmission delay time of the transmission / reception buffer for starting frame transmission according to the usage status of the wireless line RL and increase the throughput of the wireless LAN. In this embodiment, since the usage status of the radio line RL is determined by the number of communication frames, the transmission delay time of each transmission / reception buffer is
Compared with the embodiment of FIGS. 2 and 3, the setting is made according to a more substantial usage situation of the radio line RL.

FIG. 6 shows a partial block diagram of a third embodiment of the host side transmission / reception buffer HBUF1 included in the wireless LAN of FIG. 1, and FIG. 7 shows an example of the frame transmission processing thereof. The processing flow diagram of is shown. Based on these drawings, the outline and features of the third embodiment of the host side transmission / reception buffers HBUF1 to HBUFm and the input / output device side transmission / reception buffers DBUF1 to DBUFn to which the present invention is applied will be described. It should be noted that this embodiment basically follows the embodiment of FIGS. 2 to 5, and therefore only the portions different from this will be described.

In FIG. 7, the host side transmission / reception buffer HBUF1 of this embodiment is provided with an address counting unit ADC instead of the carrier detection rate determining unit CDT of FIG. 2 and the frame counting unit FRC of FIG. This address counter ADC
The address detection signal A from the reception data control unit RDC.
D is supplied, and its output signal is supplied to the transmission delay unit TDL as the destination address number AN. Transmission delay unit TDL
Further, the carrier detection signal CD is supplied from the reception line control unit RLC.

In this embodiment, the reception data control unit R
The DC has a function of identifying a destination address in the received control frame, and temporarily sets the address detection signal AD to a valid level every time a different destination address is identified. The address counting unit ADC is not particularly limited, but a timer circuit that forms a counter reset signal of a predetermined cycle, a counter circuit that is reset by the counter reset signal and counts up according to the address detection signal AD, and a counter circuit A register that captures the count value immediately before being reset by the reset signal is included. The output signal of this register is supplied to the transmission delay unit TDL as the destination address number AN. As a result, the output signal of the register, that is, the number of destination addresses AN, corresponds to the rate at which different destination addresses are detected within the unit time, that is, the number of communication stations that use the wireless line RL within the unit time.

The transmission delay unit TDL of the host side transmission / reception buffer HBUF1 which is about to start frame transmission is shown in FIG.
As shown in, the presence / absence of a carrier is determined in step ST21. Then, in step ST22, the number A of destination addresses output from the address counter ADC
After determining the use status of the wireless line RL based on N and selectively setting the maximum value of the transmission delay time to level 0 to level X, a pseudo random number is generated in step ST33,
The transmission delay time is randomly determined according to the generated random number and within the set maximum value range. Thereafter, the transmission delay time determined in step ST34 is waited for, the presence or absence of a carrier on the radio line RL is again determined by the carrier detection signal CD in step ST35, and the transmission line control unit TLC is selectively activated to perform frame transmission. To execute.

As described above, in the wireless LAN of this embodiment, the host side transmission / reception buffers HBUF1 to HBUFm and the input / output device side transmission / reception buffers DBUF1 to DBU are provided.
The address counting unit ADC of Fn monitors the number of communication stations using the wireless line RL per unit time, that is, the usage status thereof, and the transmission delay unit TDL of the transmission / reception buffer which is about to start frame transmission uses the address counting unit ADC.
The maximum value of the transmission delay time is selectively set in accordance with the output signal of, that is, the number AN of destination addresses. As a result, when the number of destination addresses AN is large and the load on the wireless line RL is large, the maximum value of the transmission delay time can be increased to avoid excessive collision, and the number of destination addresses AN is small and the wireless line RL is small. When the load on the RL is small, it is possible to reduce the maximum value of the transmission delay time and quickly capture the vacant wireless line RL. As a result, it is possible to optimize the transmission delay time of the transmission / reception buffer for starting frame transmission according to the usage status of the wireless line RL and increase the throughput of the wireless LAN. In this embodiment, since the usage status of the wireless line RL is determined by the number of destination addresses, the transmission delay time of each transmission / reception buffer is less than that of the embodiments of FIGS. It will be set according to the actual usage situation including the actual load.

As shown in the above embodiment, by applying the present invention to the wireless LAN adopting the contention system, the following operational effects can be obtained. That is, (1) the waiting CSMA method is adopted as a line access method for a wireless LAN or the like that adopts the contention method, and the maximum value of the transmission delay time is calculated by using the communication line, that is, the carrier detection rate or By selectively setting according to the number of communication frames or the number of communication stations, it is possible to avoid excessive collision by increasing the maximum value of the transmission delay time when the load on the communication line is large. When the load on (1) is small, the maximum value of the transmission delay time can be reduced to obtain the effect that the communication line in the idle state can be quickly captured. (2) According to the above item (1), the effect that the transmission delay time of the transmission / reception buffer, that is, the communication control device can be optimized according to the usage status of the communication line is obtained. (3) According to the above items (1) and (2), it is possible to obtain an effect that the throughput of a wireless LAN adopting the contention system can be increased.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say. For example, in FIG. 1, host computers HCOM1 to HCOM
COMm and the input / output devices IOD1 to IODn do not all need to be coupled to the radio line RL. The wireless line RL can be replaced with a wireless communication unit such as infrared rays or laser light, or can be replaced with a wired communication unit such as a digital line or an optical communication line. The system configuration of the wireless LAN is not restricted by this embodiment.

In FIG. 2 to FIG. 7, whether or not the radio line RL is in use may be determined by other than the carrier. Further, the redetermination of the carrier performed after the transmission delay time has elapsed in steps ST5, ST15 and ST25 may be omitted. The usage status of the wireless line RL can be determined based on the source address instead of the destination address, or both the destination address and the source address may be used. Further, various embodiments can be adopted as the specific circuit configuration of the host side transmission / reception buffer HBUF1 and the frame transmission procedure.

In the above description, the case where the invention made by the present inventor is applied mainly to the wireless LAN and the transmission / reception buffer which are the fields of application in the background has been described, but the invention is not limited thereto. It can be widely applied to various communication systems adopting the tension system and their communication control devices.

[0039]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows. That is, the standby CSMA method is adopted as a line access method for a wireless LAN or the like that adopts the contention method, and the maximum value of the transmission delay time of the communication control device is
When the load on the communication line is large, the maximum value of the transmission delay time can be set by selectively setting it according to the usage status of the communication line, that is, the carrier detection rate or the number of communication frames or communication stations per unit time. It can be increased to avoid excessive collision, and when the load on the communication line is small, the maximum value of the transmission delay time can be decreased to quickly capture the communication line in the idle state. As a result, the transmission / reception buffer, that is, the transmission delay time of the communication control device can be optimized according to the usage status of the communication line, and the throughput of the wireless LAN or the like adopting the contention system can be increased.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of a wireless LAN including a transmission / reception buffer to which the present invention is applied.

FIG. 2 is a partial block diagram showing a first embodiment of a host side transmission / reception buffer included in the wireless LAN of FIG.

FIG. 3 is a process flow chart showing an embodiment of a frame transmission process in the host side transmission / reception buffer of FIG.

FIG. 4 is a partial block diagram showing a second embodiment of a host-side transmission / reception buffer included in the wireless LAN of FIG.

5 is a processing flow chart showing an embodiment of frame transmission processing in the host side transmission / reception buffer of FIG.

FIG. 6 is a partial block diagram showing a third embodiment of a host-side transmission / reception buffer included in the wireless LAN of FIG.

7 is a process flow chart showing an embodiment of a frame transmission process in the host side transmission / reception buffer of FIG.

FIG. 8 is a processing flowchart showing an example of frame transmission processing in a host side transmission / reception buffer developed by the inventors of the present application prior to the present invention.

[Explanation of symbols]

HCOM1 to HCOMm ... Host computer, H
BUF1 to HBUFm ... Host side transmission / reception buffer,
DBUF1 to DBUFn ... I / O device side transmission / reception buffers, IOD1 to IODn ... I / O devices, RL ...
-Wireless line. CPU ... Central processing unit, TDC ... Transmission data control unit, TDL ... Transmission delay unit, TLC ... Transmission line control unit, RLC ... Reception line control unit, RDC ... Reception data control Department, CDT ... Carrier detection rate determination unit,
FRC ... Frame counter, ADC ... Address counter, MEM ... Memory device, IBUS ... Internal bus.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyoshi Furuhata 5-22-1, Kamisuihoncho, Kodaira-shi, Tokyo Inside Hitachi Microcomputer System Co., Ltd. No. 22-1 Hitachi Microcomputer System Co., Ltd. (72) Inventor Masahiro Watanabe 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Japan Victor Company of Japan, Ltd. (72) Takami Shiramizu Moriya, Kanagawa-ku, Yokohama, Kanagawa 3-12, Machi Within Victor Company of Japan, Ltd.

Claims (5)

[Claims] 1. A communication control apparatus, wherein a transmission delay time when a communication line becomes idle is selectively switched according to the usage status of the communication line. 2. The communication control device is included in a wireless LAN that adopts a contention system, and the maximum value of the transmission delay time is selectively set according to the usage status of the communication line. 2. The communication control device according to claim 1, wherein the communication control device is selectively switched over. 3. The communication control device according to claim 1, wherein the maximum value of the transmission delay time is selectively set according to a carrier detection rate of a communication line. 4. The communication according to claim 1 or 2, wherein the maximum value of the transmission delay time is selectively set according to the number of communication frames per unit time of the communication line. Control device. 5. The communication according to claim 1 or 2, wherein the maximum value of the transmission delay time is selectively set according to the number of communication stations per unit time of the communication line. Control device.