JP2002111677A - Communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a communication apparatus of CSMA system for transmitting information of its own station periodically to other station in which throughput is enhanced by lowering the possibility of collision. SOLUTION: Based on the demodulation results of a receiving signal when a specified processing delay time has elapsed after transmitting information of its own station, a decision is made whether transmission information of its own station collided against transmission information from other station or not (8A, 18A). At every update period (U) of transmission information, a transmittable time is detected (7A) based on the results of carrier sense, the detected transmittable time is stored and a transmission time in next update period of transmission information is determined (6A) based on the collision decision results at the update period of transmission information and the detected transmittable time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a CSMA (carrie)
The present invention relates to a communication device using a r sense multiple access (r sense multiple access) method, and particularly to a communication device suitable for inter-vehicle communication.

[0002]

2. Description of the Related Art As a prior art of this kind, there is one disclosed in the following document. Reference 1: Atsushi Matsushita and Masao Nakagawa, "Wireless LAN Architecture", Kyoritsu Publishing. Reference 2: Matsushita Atsushi, "Wireless LAN Technology Course", SRC
Handbook.

[0003] In the conventional CSMA system, each station (station) senses a carrier to check the use state of a channel, and determines whether to transmit a packet according to whether the channel is idle. The CSMA scheme is classified into a non-persistent CSMA scheme and a p-persistent CSMA scheme according to the manner of carrier sensing. In the standby CSMA system, when carrier sense is performed, transmission is not performed if the channel is busy, and carrier sense is performed again after a while. When carrier sense is performed again, transmission can be performed if the channel is in an idle state. On the other hand, if the channel is busy, carrier sense is performed after a while again. On the other hand, the P-immediate CSMA system is a system in which, when the channel is in a busy state, carrier sense is continued and the system waits until the channel becomes an idle state. When it detects that the channel has changed from the busy state to the idle state, it transmits with a probability of p and withdraws with a probability of 1-p.

[0004]

SUMMARY OF THE INVENTION However, CSM
Since the A system is a contention system, a collision may occur. In order to exchange control information between vehicles, it is necessary to periodically update information at vehicle control intervals. Waiting type CS
In the MA system, if the channel for which carrier sense is performed is busy, the next carrier sense time is set and carrier sense is performed again. As a result of the carrier sense at the next carrier sense time, if the time from the time when the channel is busy to the next carrier sense time is set to be longer, the number of vehicles that cannot be transmitted within the cycle of updating the vehicle control information increases. I will. On the other hand, if the time from the time when the channel is busy to the next carrier sense time is set short as a result of carrier sense, each vehicle frequently performs carrier sense, finds an idle state section of the channel, and performs transmission. As a result, collisions increase, and the throughput, which is a substantial information transmission amount per unit time, decreases.

An object of the present invention is to provide a communication device which has a low possibility of collision and has a high throughput.

[0006]

According to the present invention, there is provided a communication apparatus comprising:
In the SMA communication apparatus, a transmission request generating means for generating a transmission request control signal (103A) for each transmission information update cycle of its own station, (3A), and the transmission request control signal (10
3A) means for updating the information to be transmitted and generating own station information (1A, 2A); and a transmission start control signal (10A).
6A), the transmission control means (5A) for transmitting the generated own station information, and after the own station transmits the information,
Collision determination means (8A, 18A) for determining whether or not transmission information of the own station has collided with transmission information from another station based on a demodulation result of a reception signal when a predetermined delay time has elapsed; And a carrier sense means (7A) for detecting a transmittable time based on the carrier sense result for each transmission information update cycle, and a transmittable time detected by the carrier sense means (7A). And determines the carrier sense time in the next transmission information update cycle based on the determination result by the collision determination means and the transmittable time detected by the carrier sense means in each transmission information update cycle. The carrier sense means (7A) performs carrier sense at the carrier sense time, and it is confirmed that the carrier sense means (7A) is in an idle state as a result of the carrier sense. It is Once, characterized by comprising a carrier sensing time setting means (6A) for generating the transmission start control signal (106A).

[0007] When the carrier sense time setting means determines that a collision has occurred in a certain transmission information update cycle, the carrier sense time setting means sets the transmission possible time detected in the certain transmission information update cycle in the next transmission information update cycle. One of them may be selected at random and set as the carrier sense time in the next transmission information update cycle.

When the carrier sense time setting means determines that no collision has occurred in a certain transmission information update cycle, the same time as the transmission time in the certain transmission information update cycle is set in the next transmission information update cycle. , May be selected as the carrier sense time in the next update cycle.

The collision judging means (8A) compares the transmission information transmitted by its own station with the demodulation result of the received signal at the time when the predetermined delay time has elapsed since the transmission information was transmitted. Alternatively, it may be determined whether or not a collision has occurred.

The collision judging means (18A) detects an error detection code from the demodulation result of the received signal at the time when the predetermined delay time has elapsed since the own station transmitted the signal, and based on the result, It may determine whether or not a collision has occurred.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a block diagram showing a communication device according to the first embodiment of the present invention. This communication device is used for inter-vehicle communication. The vehicle-to-vehicle communication is performed between communication devices mounted on a plurality of vehicles. An inter-vehicle communication system is usually composed of a large number of communication devices.
Two communication devices, that is, communication devices in vehicle A and vehicle B are shown.

As shown, the communication device in the vehicle A includes a host vehicle control unit 1A, a host vehicle information generation unit 2A, a transmission request generation unit 3A, a packet generation unit 4A, and a transmission control unit 5A.
, A carrier sense time setting unit 6A, a carrier sense unit 7A, a collision determination unit 8A, a modulation unit 9A, a transmission antenna 10A, a reception antenna 11A, and a demodulation unit 12A.
And a reception information demodulation unit 13A and a delay unit 14A.

The transmission request generator 3A generates a transmission request control signal 103A. This transmission request control signal 103A
Are the own vehicle control unit 1A and the carrier sense time setting unit 6A
And transmitted to the carrier sense section 7A.

The own vehicle control section 1A transmits a transmission request control signal 1
When receiving 03A, the vehicle control information 101A is generated. The own vehicle control information 101A is sent to the own vehicle information generating unit 2A.

The host vehicle information generation unit 2A includes the host vehicle control unit 1
A own vehicle control information 101A is received from A, and based on this, a predetermined data series 102A representing own vehicle information is generated. The packet generation unit 4A includes a host vehicle information generation unit 2A.
, And generates and outputs a packet 104A.

The transmission control unit 5A receives the packet 104A from the packet generation unit 4A, and outputs a transmission signal 105A when the transmission start control signal 106A is transmitted from the carrier sense time setting unit 6A.

The modulation section 9A receives the transmission signal from the transmission control section 5A and performs carrier modulation by multiplying the transmission signal by a carrier from a carrier generator (not shown). The transmitting antenna 10A transmits the signal from the modulator 9A to the air. The receiving antenna 11A receives a signal from the air. The demodulation unit 12A receives the reception signal received by the reception antenna 11A, and performs carrier demodulation by multiplying the reception signal by a carrier from a carrier generator (not shown).

The received information demodulation unit 13A receives the output of the demodulation unit 12A, performs demodulation, and outputs received demodulated data 113A. The received demodulated data 113A is the own vehicle control unit 1A.
And sent to the collision determination unit 8A. The own vehicle control unit 1A includes:
Other vehicle information is extracted from the received demodulated data 113A, and based on this, the own vehicle control information 101A is generated as described above.

The delay section 14A delays the own vehicle information output from the own vehicle information generating section 2A by a predetermined delay time and outputs it. This delay time corresponds to the vehicle information generation unit 2A.
Is transmitted from the transmission antenna 19A through the packet generation unit 4A, the transmission control unit 5A, and the modulation unit 9A, is further received by the reception antenna 11A, and is transmitted through the demodulation unit 12A and the reception information demodulation unit 13A. Thus, the time until it appears on the output side of the reception information demodulation unit 13A is set to be substantially equal to the time.

The collision judging unit 8A outputs the output 1 of the delay unit 14A.
14A is compared with the output 113A of the received information demodulation unit 13A. If the correlation value between the two is higher than a predetermined threshold value, it is determined that no collision has occurred. Otherwise, it is determined that a collision has occurred. I do. In other words, the collision determination unit 8A compares the vehicle information transmitted by the own vehicle with the demodulation result of the received signal at the time when the predetermined delay time has elapsed since the transmission of the vehicle information, and the transmission information It is determined whether or not demodulation is performed correctly. If demodulation is performed correctly, it is determined that no collision has occurred. If demodulation is not correctly performed, it is determined that transmission information from the own vehicle has collided with transmission information from another vehicle. .

The signal output from the host vehicle information generation unit 2A is transmitted to the packet generation unit 4A and the transmission control unit 5A.
A and the time from the transmitting antenna 19A via the modulating unit 9A to the receiving antenna 11A, and then to the output side of the receiving information demodulating unit 13A via the demodulating unit 12A and the receiving information demodulating unit 13A. " Although is not exactly constant, the determination as to whether or not the transmission information has been correctly demodulated is made after confirming the identification information of the own station, so that it is not necessary to know the exact time. That is, at the time when the transmission information is expected to appear on the output side of the reception information demodulation unit 13A,
The output of the reception information demodulation unit 13A is checked, and the information of the part having the identification information of the own station is compared with the output of the delay unit 14A to determine whether or not a collision has occurred. Also, at a time when the transmission information is expected to appear at the output side of the reception information demodulation unit 13A, the output of the reception information demodulation unit 13A is checked, and if the identification information of the own station does not appear, a collision has occurred. Make a decision.

The carrier sense unit 7A receives the received signal 112A output from the demodulation unit 12A, always performs carrier sense (detection of a carrier wave) of the received signal, and transmits a carrier sense request from a carrier sense time setting unit 6A described later. In response to signal SDA, signal SRA indicating the carrier sense result at that time is output. In addition, for each transmission information update cycle, a transmittable time (a relative time within the cycle, for example, an elapsed time from the start of the cycle) is detected based on the result of the carrier sense, and the detection result is indicated. The data is sent to the carrier sense time setting section 6A.

The carrier sense time setting unit 6A receives the transmission request control signal 103A from the transmission request generation unit 3A,
This is recognized as a cycle signal of the vehicle information update cycle (time interval). That is, the time at which the transmission request control signal 103A is received is recognized as the start time of the vehicle information update cycle. The carrier sense time setting section 6A also has a memory 6A1. The memory 6A1 stores a result of the collision determination in the collision determination unit 8A. The carrier sense section 7A
And stores the transmittable time detected by. further,
A carry request signal SDA is generated. This signal SD
A is sent to the carrier sense section 7A. When a signal SRA indicating that the idle state has been confirmed by the carry sense unit 7A is sent to the carrier sense request signal SDA, the carrier sense time setting unit 6A generates a transmission start control signal 106A.

The communication device in the vehicle B is also configured in the same manner, and its constituent members are indicated by the same reference numerals as those of the corresponding constituent members in the vehicle A (reference numerals with B added instead of A at the end). ing.

As described above, the transmission request control signal 103A generated from the transmission request generation unit 3A is transmitted to the own vehicle control unit 1A.
Is supplied to the host vehicle information generation unit 2A from the host vehicle control unit 1A, and the host vehicle information generation unit 102A generates a predetermined data sequence representing the host vehicle information. It is packetized by the generation unit 4A and sent to the transmission control unit 5A, and the transmission control unit 5A waits for the transmission start control signal 106A sent from the carrier sense time setting unit 6A.

When the transmission start control signal 106A is generated, a transmission signal 105A is output from the transmission control unit 5A. The transmission signal 105A is transmitted to the air via the transmission antenna 10A via the modulation unit 9A. Other vehicles,
For example, a signal is transmitted from the transmission antenna (for example, the transmission antenna 10B) in the vehicle B in the same manner. The receiving antenna 11A receives not only a signal from another vehicle but also a signal transmitted from the transmitting antenna 10A of the own vehicle. The signal received by the receiving antenna 11A is
After that, it is sent to the received information demodulation unit 13A and the carrier sense unit 7A.

In the reception information demodulation unit 13A, the demodulation unit 12A
And demodulates the received signal to generate received demodulated data 113A. The received demodulated data 113A includes not only the information (other vehicle information) transmitted from the transmission antenna (10B) of the other vehicle (for example, the vehicle B) but also the transmission antenna (10B) of the own vehicle.
The information sent from A) is also included. For example, when the own vehicle is not transmitting and another vehicle is transmitting, only the other vehicle information is included. Conversely, when the own vehicle is transmitting and the other vehicle is not transmitting, the own vehicle information is transmitted. Only. When both the own vehicle and the other vehicle are transmitting, a collision has occurred.

The demodulated data 113A is sent to the host vehicle control section 1A, and the host vehicle control section 1A extracts other vehicle information and generates control information based on the extracted information. The received demodulated data 113A is also sent to the collision determination unit 8A. The own vehicle information output from the own vehicle information generating unit 2A is
4A, and after the predetermined delay time, the delay unit 14A
Output from

In the collision determination section 8A, the own vehicle information generation section 2
A, and compares the own vehicle information 102A (which is obtained by delaying the own vehicle information by a predetermined delay time) supplied from the delay unit 14A with the signal from the reception information demodulation unit 13A. If the correlation value is higher than a predetermined threshold value, it is determined that no collision has occurred. Otherwise, it is determined that a collision has occurred. The result of the collision determination is written to the memory 6A1 provided in the carrier sense time setting section 6A.

The carrier sense time setting unit 6A that has received the transmission request control signal 103A from the transmission request generation unit 3A
Then, this is recognized as a cycle start signal of the vehicle information update cycle. That is, the time at which the transmission request control signal 103A is received is recognized as the start time of the vehicle information update cycle.

Upon receiving the transmission request control signal 103A, the carrier sense section 7A performs carry sensing, detects a transmittable time within the current vehicle information update cycle, and sets the start time of each transmittable time to the carrier time. The data is written to the memory 6A1 in the sense time setting unit 6A.

FIG. 3 is a timing chart showing the operation of the apparatus according to the first embodiment. In the figure, (a) shows the transmission / reception status of the channel viewed from the vehicle A, and (b) shows the vehicle A
(C) indicating the carrier sense and transmission available time as viewed from
Indicates the transmission / reception status of the channel viewed from the vehicle B,
(D) shows the carrier sense and transmission available time as seen from the vehicle B, and (e) shows the transmission reception status and transmission available time of the channel of the third vehicle (vehicle C) not shown in FIG. Is shown.

In the example shown in FIG. 3, the left end of 〜 in FIG. 3B indicates the start time of the transmission enabled time, and these are stored in the memory 6A1. Note that the width of represents the time obtained by adding the processing delay time to the packet length. In the vehicle B, similarly, the carrier sense time setting unit 6
The time at the left end of 〜 in FIG.

Upon receiving transmission request control signal 103A, carrier sense time setting section 6A sets a carrier sense time for transmission. The method of setting the carrier sense time differs according to each case, as described below.

1) When it is determined that "collision has occurred" in the previous vehicle information update cycle For example, such a determination is made at timing PA1 in FIG. 3 (a) and timing PB1 in FIG. 3 (c).

In the vehicle A, the previous vehicle information update cycle U
In A1, when such a determination is made at timing PA1 in FIG. 3A, the transmission possible time detected during the period UA1 and stored in the memory 6A1 (for the vehicle A, FIG. b) 1 at random from left end of ~)
One is selected, and the selected time is set as the carrier sense time of the current vehicle information update cycle UA2.

Similarly, in the vehicle B, the timing PB1 shown in FIG.
When such a determination is made, the left end of the time の in FIG. 3D detected in the cycle UB1 and stored in the memory 6B1 (not necessarily coincident with the left end of 〜 in FIG. , One is selected at random, and the selected time is set as the carrier sense time of the current vehicle information update cycle UB2.

When the carrier sense time comes, a carrier sense request signal SDA is sent to carrier sense section 7A, carrier sense is performed in carrier sense section 7A, and a signal (SR) indicating the carrier sense result is provided.
A) is sent from the carrier sense section 7A to the carrier sense time setting section 6A. When signal SRA indicates that the idle state of the channel has been confirmed, transmission start control signal 106A is transmitted from carrier sense time setting section 6A to transmission control section 5A and collision determination section 8A.

The transmission start control signal 106 is transmitted by the transmission control unit 5A.
When A is received, the packet is sent to the modulation unit 9A, modulated by the modulation unit 9A, and then transmitted from the transmission antenna 10A. On the other hand, the collision determination unit 8A determines a collision.

2) When it is determined that "a collision did not occur" in the previous vehicle information update cycle For example, the timing PA2 in FIG. 3A, the timing PB2 in FIG. 3C, and the timing in FIG. Timing PC1
Such a determination is made by the PC 2 or the PC 2.

In the vehicle A, the previous vehicle information update cycle U
In A2, when such a determination is made at timing PA2 in FIG. 3A, the previous vehicle information update cycle UA2
After confirming the idle state of the channel by carrier sense, the same time as the transmission time (relative time in the update cycle) is set as the carrier sense time in the current vehicle information update cycle (the next cycle of UA2). When the carrier sense time comes, the carrier sense unit 7A performs carrier sense, confirms the idle state of the channel, and sends a transmission start control signal 106A from the carrier sense time setting unit 6A to the transmission control unit 5A and the collision determination unit 8A. . When the transmission start control signal 106A is received by the transmission control unit 5A, a packet is sent to the modulation unit 9A, and after being modulated by the modulation unit 9A,
It is transmitted from the transmitting antenna 10A. The collision determination unit 8A determines a collision.

The timing P in FIG.
Similar processing is performed when the same determination is made at timings PC1 and PC2 in FIG.

3) Initial state Since the determined transmittable time is not written in the memory 6A1 in the carrier sense time setting section 6A, the carrier sense time is set at random, and when the carrier sense time comes, the carrier sense section is set. Carrier sensing is performed at 7A, transmission is performed in the idle state, and the carrier sense time is set again in the busy state. This operation is repeated until it can be transmitted once within the vehicle information update cycle.
(It is not always possible to transmit within the vehicle information update period.) If the channel is in the idle state, the transmission start control signal 106A is transmitted from the carrier sense time setting unit 6A to the transmission control unit 5A and the collision determination unit 8A. Transmission control unit 5
When receiving the transmission start control signal 106A at A, the modulation unit 9
The packet is sent to A, modulated by the modulator 9A, and then transmitted from the transmitting antenna 10A. In the collision determination unit 8A,
A collision determination is made.

The vehicle information update cycle of vehicles A, B and C is the same for all vehicles, ie, UA1, UA2, UB
1, UB2, UC1, and UC2 have the same length,
It is assumed that the vehicle information update cycle is not synchronized. In the vehicle information update periods UA1 and UB1, vehicles A and B
Are colliding. Carrier sense is always performed, and when the vehicle information update cycle becomes new due to the transmission request control signals 103A and 103B, each vehicle causes the built-in timers in the carrier sense units 7A and 7B and the like to start a counting operation, and the channel is changed. In the idle state, the timer continues counting. When the count value becomes a time obtained by adding the processing delay time to the packet length, the counting is stopped, and the start time of this count is written to the memory 6A1 in the carrier sense time setting unit 6A as the transmittable time. Then, the count value is returned to the initial value and the count is restarted.
If the channel becomes busy while the timer is counting, stop counting. Thereafter, when the channel enters an idle state, the count value is returned to the initial value and the counting is restarted. When the count value becomes the time obtained by adding the processing delay time to the packet length even after the restart, the counting is stopped, and the start time of this count is written to the memory 6A1 in the carrier sense time setting unit 6A as the transmittable time. Is reset to the initial value and counting is restarted. By repeatedly performing such a process, for the vehicle A, for example, the transmittable time represented by the left end of to in FIG. 3B is written to the memory 6A1.

Similarly, in the vehicle B, the transmittable time represented by the left end of the symbol in FIG. 3D is written in the memory 6B1. Similar processing is performed for other vehicles such as the vehicle C.

When shifting from the vehicle information update period UA1 to the vehicle information update period UA2, information indicating that a collision has occurred in the memory 6A1 of the vehicle A in the vehicle information update period UA1 is indicated by the left end in FIG. Each transmission start time is stored. Since a collision occurred in the cycle UA1, in the cycle UA2, one of the times represented by the left end of FIG. 3B is randomly selected, and the time (the time represented by the left end of FIG. As a result of your selection,
The time (the time from the beginning of the cycle UA1 to the left end) is t
(A2), and after confirming that the channel is in the idle state by carrier sensing, transmit.

Similarly, since the collision of the vehicle B occurs in the cycle UB1, one of the transmission possible times of the vehicle B in the cycle UB2, that is, one of the times indicated by the left end in FIG. At the time (Fig. 3 (d)
As a result of selecting the time represented by the left end of the above, the time (the time from the beginning to the left end of the period UB1) becomes tB3, and after confirming that the channel is in the idle state by carrier sensing, I do.

In the vehicle C, since no collision has occurred in the cycle UC1, a time tC of the vehicle information update cycle UC1 is selected instead of selecting one of the transmittable times in the cycle UC2.

In the example of FIG. 3, the vehicle information update period UA2,
In UB2 and UC2, since no collision occurs for each vehicle, tA, tB, and tA in the next vehicle information update cycle.
Each vehicle transmits at time C. Unlike FIG. 3, when a collision occurs in the update periods UA2, UB2, and UC2, operations similar to those in the update periods UA1, UB1, and UC1 from UA2, UB2, and UC2 are repeated.

In order to exchange control information between vehicles,
It is necessary to update the information periodically in the vehicle information update cycle, but the time domain of the idle state of the channel is checked in the vehicle information update cycle of each vehicle, and the possibility of a collision may be increased by utilizing it in the next vehicle information update cycle. Decrease.

Embodiment 2 Hereinafter, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram of a communication method according to the second embodiment. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding members.

The difference from the first embodiment is that CRC detectors 18A and 18B are provided instead of the collision judging units 8A and 8B in FIG. 1, and delay units 14A and 14B are not provided. is there. The CRC detection unit performs a CRC (cyclic r
Error detection is performed using codes.

Upon receiving the transmission start request signal 106A, the reception information demodulation unit 13A recognizes that the packet received after a predetermined delay time is a packet of the own vehicle,
The CRC part of the packet is sent to the CRC detector 8A,
The CRC detector 8A determines whether there is an error. The above-described delay time is obtained by transmitting the signal output from the transmission control unit 5A after the transmission start control signal 106A is generated, transmitted from the transmission antenna 10A, received by the reception antenna 11A, demodulated by the demodulation unit 12A, It is determined to be equal to the time until the signal passes through 13A and appears as the output of the received information demodulation unit 13A. However, since this time is extremely short, the demodulation unit 13A immediately after the transmission start control signal 106A is generated.
May be treated as data obtained by demodulating the transmission data.

If it is determined by the CRC detection that there is an error, it is determined that there is a collision. Conversely, if there is no error, it is determined that no collision has occurred. This determination result is transmitted to the carrier sense time setting unit 6A, and the internal memory 6
A1 is written.

As described above, in the first embodiment, the collision is determined by the collision determining unit 8A, whereas in the second embodiment, the collision is determined by the CRC detecting unit 18A. Therefore, the determination processing can be simplified as compared with the first embodiment.

Note that error detection may be performed using an error detection code other than CRC.

The case where the present invention is applied to inter-vehicle communication has been described above. However, the present invention can be applied to any communication apparatus other than inter-vehicle communication as long as the communication apparatus uses the CSMA system and transmits data at certain periodic intervals. It is.

[0059]

As described above, according to the present invention, it is possible to reduce the possibility of occurrence of a collision and obtain a communication device having a high throughput.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a configuration according to a second embodiment of the present invention.

FIG. 3 is a time chart showing the operation of the first and second embodiments.

[Explanation of symbols]

1A, 1B: own vehicle control unit; 2A, 2B: own vehicle information generation unit; 3A, 3B: transmission request generation unit;
4A, 4B: packet generator; 5A, 5B:
6A, 6B: carrier sense time setting unit; 7A, 7B: carrier sense unit;
A, 8B: collision determination unit; 9A, 9B: modulation unit;
10A, 10B: transmitting antenna; 11A, 1
1B: receiving antenna: 12A, 12B: demodulation unit; 13A, 13B: reception information demodulation unit;
A, 14B: delay section; 18A, 18B: CRC
Detection unit.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shoichi Nakabayashi 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Inventor Kiyohito Tokuda 1-7-1 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. F term (reference) 5K033 AA01 BA06 CA08 DA19 DB09 5K034 AA02 DD05 EE03 HH10 QQ08

Claims (5)

[Claims] In a communication apparatus of a CSMA system, a transmission request control signal (103) is transmitted every transmission information update cycle of its own station.
A transmission request generating means for generating A), a means for updating information to be transmitted in response to the transmission request control signal, and generating own station information in response to the transmission request control signal.
Transmission control means (5A) for transmitting the generated own station information in response to the transmission start control signal (106A); and reception after a lapse of a predetermined delay time since the own station transmits the information. Collision determination means (8A, 18A) for determining whether or not transmission information of the own station collides with transmission information from another station based on a signal demodulation result; Every,
Carrier sense means (7A) for detecting a transmittable time based on the carrier sense result; and a transmittable time detected by the carrier sense means (7A). Based on the determination result by the collision determination unit and the transmittable time detected by the carrier sense unit, determine the carrier sense time in the next transmission information update cycle,
At the carrier sense time, the carrier sense means (7
A) Carrier sense is performed, and carrier sense time setting means (6A) for generating the transmission start control signal (106A) when the idle state is confirmed as a result of the carrier sense is provided. Communication device. 2. The method according to claim 1, wherein the carrier sense time setting means, when it is determined that a collision has occurred in a certain transmission information update cycle, in the next transmission information update cycle, the transmission enabled time detected in the certain transmission information update cycle is determined. The communication device according to claim 1, wherein one of the times is randomly selected to be a carrier sense time in a next transmission information update cycle. 3. The carrier sense time setting means, when it is determined that no collision has occurred in a certain transmission information update cycle, the carrier sense time setting means sets the same transmission time in the certain transmission information update cycle in the next transmission information update cycle. The communication device according to claim 1, wherein the time is selected as a carrier sense time in a next update cycle. 4. The collision judging means (8A) compares the transmission information transmitted by the own station with a demodulation result of a reception signal at a time when the predetermined delay time has elapsed since the transmission information was transmitted. The communication device according to claim 1, wherein the communication device determines whether or not a collision has occurred. 5. The collision judging means (18A) detects an error detection code from a demodulation result of a received signal at a time when the predetermined delay time has elapsed since the self-station transmits a signal, and The communication device according to claim 1, wherein it is determined whether or not a collision has occurred based on the information.