JP2001024546A - Radio communication device, control of radio communication, radio communication system, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably and efficiently avoid collision of communication by an inexpensive constitution. SOLUTION: A radio communication device for asynchronously transmitting/ receiving signals by using the same frequency is provided with a receiving level detection means for detecting the existence of a received signal on the basis of a signal intensity level and a correlation detection means for detecting the existence of a received signal on the basis of the existence of a correlation between a signal or the like used by the radio communication device with the received signal. When a received signal is detected by the receiving level detection means, the correlation detection means is allowed to execute detection processing, and when correlation exists, detection processing is executed again from the detection processing of the receiving level detection means after the lapse of previously set back-off time from the moment no received signal is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission control technique in a communication device which performs asynchronous and time-division communication.

[0002]

2. Description of the Related Art Conventionally, in a wireless data communication apparatus in which a plurality of stations asynchronously wirelessly communicate with a partner station using carrier waves of the same frequency, particularly in a wireless data communication apparatus using a spread spectrum communication system, each station has a short time. TDMA (Time Division Multi) that performs divisional communication
(IP Access) system is often used.
In this TDMA system, wireless medium access control is usually performed based on state monitoring of a wireless medium (hereinafter, referred to as carrier sense) in order to avoid collision of communication with another station.

For example, in a wireless LAN system,
CSMA / CA (CarrierSense Multi)
iple Access with Collisio
nAvoidance), and by performing access control using a randomly selected back-off time,
Multiple asynchronous communication stations coexist.

[0004] In the CSMA / CA procedure, when performing transmission, the state of the medium is confirmed by carrier sense, and data is transmitted to the wireless medium only when no carrier is detected for a certain specified time. If a carrier is detected during carrier sense, the transmission operation is immediately stopped with carrier sense continued, and transmission is waited for a randomly defined back-off time after the carrier is no longer detected. After that, the transmission operation including the carrier sense is restarted.

[0005] In this carrier sensing, when a radio wave having a level exceeding a predetermined reception electric field strength is received, a level carrier sensing method for determining that a carrier has been detected or a spread code used by the own station is used. A correlation carrier sensing method or the like is used in which a wave is correlated and a carrier is detected when a correlation value with the spreading code is obtained.

[0006] In the level carrier sense system, a signal received via an antenna is detected, and carrier sense is performed based on the signal level. Further, in the correlated carrier sense method, SAW (Sur
face Acoustic Wave) A correlation operation is performed by a matched filter, and carrier detection is performed at high speed by detecting the correlation peak signal, or a correlation operation is performed by a digital matched filter and carrier sense is performed based on the calculation result. are doing.

In many wireless data communication apparatuses using the spread spectrum method, usually, in order to achieve miniaturization and cost reduction, a correlation peak is obtained using a digital matched filter, or based on the output of the digital matched filter. Carrier sense.

[0008]

However, conventionally, as described above, when a carrier is detected during carrier sense, the transmission operation is immediately interrupted while carrier sense is continued, and the carrier is detected. After disappearing, it waits for transmission for the time of the backoff time specified at random, and then resumes the transmission operation including carrier sense, but since the control program intervenes to start the random backoff timer, The accuracy of the back-off time cannot be obtained. Therefore, in order to guarantee the operation, the minimum unit of the back-off time must be increased, and if the number of selectable steps of the back-off time is increased, the transmission interval of the radio frame becomes empty, and the decrease in the throughput is reduced. There is a problem of inviting.

In addition, in the case of monitoring the state of a wireless medium only by level carrier sense, in the case of an application in which long-distance data transmission is performed between buildings using a directional antenna, the transmitting station may be caused by a microwave oven or the like. When an interfering wave is detected, the data transmission is interrupted even if the receiving station is not affected by the interfering wave, so that the throughput similarly decreases.

On the other hand, when monitoring the state of a wireless medium by correlated carrier sensing, a configuration using a SAW matched filter can perform correlated carrier sensing at high speed, but it is difficult to reduce the size and cost of the apparatus. In the case of using a digital matched filter, a long calculation time for detecting a correlation peak is required, so that there is a problem that a carrier sensing time is long, a packet transmission interval is widened, and a throughput is reduced.

Further, if there is no reception at the start of carrier sense and another station signal is received during carrier sense, if the carrier sense time is completed before a calculation result for obtaining a correlation is obtained, the received signal becomes There is also a problem that the transmission operation is started in spite of the existence.

SUMMARY OF THE INVENTION The present invention has been made under such a background, and an object of the present invention is to make it possible to reliably and efficiently avoid communication collisions with an inexpensive configuration.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a radio communication apparatus for transmitting and receiving asynchronously using the same frequency. Reception level detection means for detecting, correlation detection means for detecting the presence or absence of a reception signal based on the presence or absence of a correlation between the reception signal and a signal or the like used by the wireless communication device; When a signal is detected, the detection process is performed by the correlation detection unit, and after a preset back-off time after the reception signal is no longer detected when there is a correlation,
A transmission control unit for executing the detection process again from the detection process by the reception level detection unit.

Further, the present invention provides a radio communication apparatus for asynchronously transmitting and receiving using the same frequency, a reception level detecting step of detecting the presence or absence of a reception signal based on a signal strength level, and A correlation detection step of detecting the presence or absence of a received signal based on the presence or absence of a correlation between the signal or the like used and the received signal, and when the received signal is detected by the reception level detection step, the correlation detection step A transmission control step of executing a detection process, and performing a detection process again from the detection process by the reception level detection process after a preset back-off time after the reception signal is not detected when there is a correlation. ing.

Further, the present invention relates to a radio communication system for asynchronously transmitting and receiving using the same frequency, a reception level detecting means for detecting the presence or absence of a reception signal based on a signal strength level, and a radio communication system comprising: Correlation detecting means for detecting the presence or absence of a received signal based on the presence or absence of a correlation between the signal or the like used and the received signal, and when the received signal is detected by the reception level detecting means, the correlation detecting means Transmission control means for executing a detection process, and after a predetermined back-off time from when the reception signal is no longer detected when there is a correlation, the detection process is again performed from the detection process by the reception level detection device. ing.

The present invention is also a storage medium for storing a program to be executed by a wireless communication apparatus that performs asynchronous transmission and reception using the same frequency, wherein the program is a program for receiving a signal based on a signal strength level. A reception level detection routine for detecting the presence / absence of a received signal, a correlation detection routine for detecting the presence / absence of a received signal based on the presence / absence of a correlation between a signal or the like used by the wireless communication device and the received signal, When the reception signal is detected by the routine, the detection processing by the correlation detection routine is executed, and when there is a correlation, the reception level detection routine is executed after a preset back-off time after the reception signal is not detected. And a transmission control routine for executing the detection process again from the detection process by

Further, according to the present invention, the transmission control means / step / routine also performs the detection processing by the reception level detecting means / step / routine when the detection processing by the correlation detection means / step / routine is executed. Run at the same time,
When the reception signal is no longer detected by the reception level detecting means, step, and routine, the detection processing by the correlation detecting means, step, and routine is interrupted, and the process is shifted to detection processing by the reception level detecting means, step, and routine. I have.

In the present invention, the transmission control means / step / routine stores a plurality of previously generated random back-off times in a memory as the back-off time, -The next back-off time stored in the memory is set each time the routine shifts to the detection processing.

In the present invention, the plurality of random back-off times are generated in advance by software.

In the present invention, the plurality of random back-off times are generated in advance by hardware.

Further, in the present invention, the transmission control means / step / routine may include a step of repeating detection processing for a predetermined transmission signal when a correlation reception signal is detected by the correlation detection means / step / routine. And the transmission process is stopped.

In the present invention, the transmission control means / step / routine transmits the transmission signal when the reception level detection means / step / routine does not detect the reception signal within a predetermined time.

Further, according to the present invention, even if a reception signal is detected by the reception level detecting means / step / routine, the transmission control means / step / routine may have a correlation by the correlation detecting means / step / routine. If not, the transmission signal is transmitted.

In the present invention, the correlation detecting means / step / routine detects whether there is a correlation between a signal used by the wireless communication apparatus (system) and a received signal using a digital matched filter. are doing.

In the present invention, the transmission control means / step / routine modulates and transmits a transmission signal by a spread spectrum modulation method.

[0026]

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

FIG. 1 is a block diagram showing a schematic configuration of a wireless communication apparatus to which the present invention is applied. FIG. 2 is a transmission timing chart when an unnecessary radio wave does not exist in a wireless medium when the wireless communication apparatus performs a transmitting operation. FIG. 3 is a diagram illustrating noise exceeding a threshold level or other noise on the wireless medium at the start of a transmitting operation. FIG. 4 is a timing chart showing transmission control when a system radio wave is present, FIG. 4 is a timing chart showing transmission control when a correlation value is obtained by receiving radio waves of the same system, and FIG. 5 is a timing chart showing a transmission value when a correlation value is obtained. 12 is a timing chart showing transmission control when a received wave is no longer detected.

FIG. 6 is a flowchart showing an outline of transmission control by a radio communication device (a control unit 101 described later).
FIG. 7 is a state transition diagram of hardware (transmission timing generation circuit 102 described later) at the time of transmission control. FIG. 8 shows FIG.
It is a state transition diagram which shows another state transition example.

As shown in FIG. 1, the present wireless communication device
Level detection circuit 104, radio section 107, modem section 10
8. It has a communication controller 109.

The modulation / demodulation unit 108 includes a demodulation circuit 106, a modulation circuit 112, an A / D converter 110, and a D / A converter 11
4. A digital matched filter 105 is provided in addition to the synchronization circuit 113. This digital matched filter 1
05 performs a correlation operation between the received signal and the spread spectrum code used in the wireless communication apparatus, and when a correlation value indicating that there is a correlation is obtained, the transmission timing generation circuit 102 to be described later detects the correlation carrier. Output a signal. Further, the modulation circuit 106 includes the transmission timing generation circuit 102
Spread spectrum modulation of transmission data according to the transmission instruction signal from. The transmission data subjected to the spread spectrum modulation is transmitted as a radio wave via the D / A converter 114 and the radio unit 107.

The level detection circuit 104 compares a signal received from the wireless medium with a predetermined threshold level, and when there is a received wave exceeding this level,
Transmission timing generation circuit 10 for transmitting level carrier detection signal
Send to 2.

The communication controller 109 has the transmission timing generation circuit 102 and the control unit 101 that controls the transmission / reception operation in the wireless section as a whole. Further, the transmission timing generation circuit 102 includes a timer register 103 that stores a plurality of back-off times randomly generated by the control unit 101, and a back-off timer 115 that measures the set random back-off time. I have.

The control unit 101 includes a CPU 101a,
A CPU having a ROM 101b and a RAM 101c;
101a controls various processes to be described later while using the RAM 101c as a work area or the like in accordance with a program preset in the ROM 101b. Also,
Although not shown, the transmission timing generation circuit 102
It has a U, a ROM, and a RAM, and executes various processes described later using these devices.

2 to 5, reference numeral 201 denotes the control unit 10;
1, a timing at which a transmission operation start command is output to the transmission timing generation circuit 102; 202, a level carrier detection signal output from the level detection circuit 104;
3 is a correlation carrier detection signal output from the digital matched filter 105, 204 is a level carrier sense time measured in the transmission timing generation circuit 102, 20
5 is a transmission instruction signal output from the transmission timing generation circuit 102, 206 is a radio transmission signal output from the radio unit 107, 207 is a correlation carrier sense time measured in the transmission timing generation circuit 102, and 208 is a radio unit 10
7, a signal 209 indicating the measurement operation of the back-off timer 115, and 210 and 211 indicate back-off times having different values.

In FIG. 6, step S301 is a process for determining whether a transmission signal is a data signal or a control signal, and step S302 is a plurality of back-off times used in a retransmission operation when the transmission signal is a data signal. Back-off generation processing for randomly generating the
3 is a writing process of writing a random back-off time into the timer register 103 in the transmission timing control circuit 102;
Step S304 is a data transmission flag writing process for indicating that the transmission signal is a data signal, and step S30.
Reference numeral 5 denotes a control signal transmission flag writing process for indicating that the transmission signal is a control signal.

Step S307 is a process for judging the presence or absence of a carrier sense completion signal output from the transmission timing generation circuit 102. Step S309 is a process after the transmission timing generation circuit 102 detects a carrier.
Judgment processing for determining processing according to the type of transmission signal,
Step S310 is a transmission canceling process performed when the transmission signal is a control signal. Step S313 is a transmission signal transfer for causing the modulation circuit 106 to perform the DMA transfer of the transmission signal after the carrier sense time has elapsed while the carrier is not detected. The instruction processing is shown.

In FIG. 7, reference numeral 401 denotes a level carrier sense and level carrier time measurement state; 402, a correlation carrier sense and correlation carrier sense time measurement state;
03 is a state in which the control unit 101 is notified of the carrier detection and is waiting for a subsequent instruction;
A state in which the back-off time set to 5 is being counted, a step 406 for setting the next back-off time written in the timer register 103 to the back-off timer 115 after the elapse of the back-off time, and a step 407 for transmitting data D
This shows a state in which MA transfer and transfer time measurement are being performed.

Next, a specific operation of the wireless communication apparatus will be described. First, when a signal to be transmitted exists in the control unit 101, the control unit 101 generates header information including address information and control information necessary for signal transmission (step S300 in FIG. 6) and transmits the header information. It is determined whether the signal is a data signal or a control frame (control signal) used in a wireless protocol (step S301). As a result, if the signal to be transmitted is a data signal, control section 101 randomly generates a plurality of back-off times to be used in a retransmission operation procedure when a carrier is detected (step S30).
2) The back-off time is determined by the transmission timing generation circuit 1
02 in the timer register 103 (step S30).
3).

When the writing of all back-off times is completed, "1" is written to a data transmission flag (not shown) of the control register in the transmission timing generation circuit 102 (step S304). If the signal to be transmitted is a control signal used in the wireless control protocol, "1" is written in a control signal transmission flag (not shown) of a control register in the transmission timing generation circuit 102 (step S30).
5).

When the writing of these flags is completed, the control unit 101 sends the header information of the transmission signal to the modulation unit 106
An MA (Direct Memory Access) transfer is performed (step S306), and the process waits until either the carrier sense completion display signal or the carrier detection display signal is received from the transmission timing generation circuit 102.

On the other hand, the transmission timing generation circuit 102
When "1" is written in the data transmission flag or the control data transmission flag, the transmission timing control operation is started at this write timing (see 201 in FIGS. 2 to 5), and the state is changed from the transmission standby 400 to the level carrier sense. A transition is made to 401 (see 400 → 401 in FIG. 7), and measurement of the level carrier sense time 204 and monitoring of the level carrier detection signal 202 are started. Here, if the written flag is a data transmission flag, the transmission timing generation circuit 102 loads the back-off time written in the first area of the timer register 103 into the back-off timer 115.

As shown in FIG. 2, if the level indicating that the level carrier detection signal 203 has not been detected (the low level here) remains until the level carrier sensing time 204 elapses, the transmission timing The generation circuit 102 changes the state to the transmission data transfer state 407 (refer to 401 → 407 in FIG. 7), displays the completion of carrier sense on the control unit 101, and sets the transmission instruction signal 205 to the modulation unit 106 to high level. To instruct transmission of a transmission signal. Modulation section 1 receiving transmission instruction signal 205
In step 06, spread spectrum modulation is performed in order from the pre-written header information, and the radio unit 1 is transmitted via the D / A converter 114.
07, and the radio transmission signal 206 is transmitted by radio waves.

Upon receiving the carrier sense completion indication from the transmission timing generation circuit 102 (step S307), the control unit 101 instructs the transmission timing generation circuit 102 to transfer the transmission signal so as to continue transmission of the transmission signal. (Step S313). The transmission timing generation circuit 102 that has received the transfer instruction starts the DMA transfer of the transmission signal in the transmission signal transfer state 407. Then, if the transfer is completed within the transfer time during the measurement, the transmission timing generation circuit 102 sends a transfer completion display signal to the control unit 1.
01 and transits to the transmission standby state 400 (4 in FIG. 7).
If the transfer cannot be completed within the transfer time, a transfer error display signal is output to the control unit 101 as time over, and a transition is made to the transmission standby state 400 (see 407 → 408 → 400 in FIG. 7). ).

When receiving the transfer completion display signal from the transmission timing generation circuit 102, the control section 101 performs a predetermined transmission completion process (step S314 → S31).
8), end. If a transfer error indication signal is received, the transmission interruption flag is set to "1" (step S).
(315 → S316), a predetermined transmission interruption process is performed (step S317), and the process ends.

As shown in FIG. 3, when a signal 208 such as noise is received at the start of transmission timing control 201 and the level carrier detection signal 202 is at a high level, the state of the transmission timing generation circuit 102 is Before the level carrier sense time 204 elapses, the level carrier sense state 401 is changed to the correlated carrier sense state 40.
2 (see 401 → 402 in FIG. 7).

In the correlated carrier sense state 402, the transmission timing generation circuit 102 starts counting the correlated carrier sense time 207 and monitors the correlated carrier detection signal 203. Until the correlation carrier sense time 207 elapses, the correlation carrier detection signal 20
3 is a level indicating that it has not been detected (temporarily low level)
In the case where the signal remains at the low level after the lapse of the correlation carrier sense time 207, the state shifts from the correlation carrier sense state 402 to the transmission signal transfer state 407 in the same manner as in the above-described level carrier sense end operation (402 in FIG. 7). 40
7), the completion of carrier sense is displayed on the control unit 101, the transfer time is measured, and the transmission instruction signal 205 to the modulation unit 106 is set high to instruct transmission of the transmission signal.

Further, as shown in FIG.
Is a signal of the same system as the wireless communication apparatus, or a signal for which a correlation value is detected, first, at the start of transmission timing control 201, the level carrier detection signal 202 is detected as described above. Then, a transition is made from the level carrier sense state 401 to the correlation carrier sense state 402 (401 → 402 in FIG. 7), and the correlation carrier detection signal 203 is monitored within the correlation carrier sense time 207.

When the correlation carrier detection signal 203 goes high during the monitoring, the state is changed from the correlation carrier sense state 402 to the carrier detection display 403 (402 → 403 in FIG. 7). Outputs carrier detection display signal. The control unit 101 that has received the carrier detection display signal determines that the carrier has been detected by the communication state detection determination process (step S308 in FIG. 6), and determines the type of the transmission signal (step S309).
As a result, if the transmission signal is a data signal, the control unit 10
1 clears the carrier detection display signal to the transmission timing generation circuit 102. When the carrier detection display signal is cleared, the transmission timing generation circuit 102
The state transits to the detected carrier monitoring state 404 (4 in FIG. 7).
03 → 404), and monitor the correlation carrier detection signal.

If the control unit 101 determines that the transmission signal is a control signal used in the wireless control protocol (step S309), the state on the program may change due to the reception signal. “1” is written into the transmission interruption flag in the generation circuit 102 (step S310), transmission cancellation processing is performed (step S311), and the process ends. Also, the control unit 101
If the transmission signal is determined to be a data signal in step S309, the transmission timing generation circuit 102
Is instructed to wait for transmission (step S31).
2), end.

In this embodiment, the transmission cancel operation is performed for all control signals. However, the cancel operation is performed only for a specific control signal, or the cancel operation is performed for all signals (including data signals). It may not be necessary. Also, the transmission suspension flag is set to “1”.
Is written, the transmission timing generation circuit 102
The transmission operation is immediately suspended, and the state transits to the transmission standby state 400. At this time, it goes without saying that the header information already transferred is cleared.

In the detected carrier monitoring state 404, the detected carrier is monitored until the correlation carrier detection signal 203 becomes low level or until the control unit 101 writes "1" in the transmission interruption flag. Then, upon detecting that the correlation carrier detection signal 203 has become low level, the state immediately transits to the backoff time count state bear 405 (refer to 404 → 405 in FIG. 7), and the already set random backoff time is calculated. Back-off timer 115
Count by

When the counting of the set back-off time is completed, the back-off time written in the next area in the timer register 103 is loaded into the back-off timer, and the state transits to the level carrier sense state 401. , And again enters the level carrier sense operation (405 → 406 in FIG. 7).
→ See 401). In the level carrier sense state 401, the level carrier detection signal 202 is monitored within the range of the level carrier sense time, and when the level carrier detection signal 202 is at the low level as shown in FIG. I do.

As shown in FIG. 5, when the count of the back-off time 210 ends and the state transits to the level carrier sense state 401, the level carrier detection signal 202
Is already at the high level, the state immediately transits to the correlation carrier sense state 402 (see 401 → 402 in FIG. 7),
The correlation carrier detection signal 203 is monitored within the range of the correlation carrier sense time 207. When the correlation carrier detection signal 203 becomes high level during this monitoring, the state transits to the detection carrier monitoring state 404, and the correlation carrier detection signal is monitored. Next, when the correlated carrier detection signal has not been detected, the state transitions to the backoff time counting state 405 according to the above-described procedure, and a series of retransmission operations such as counting the backoff time are repeated. This series of retransmission operations is repeated by control section 101 until "1" is written in the transmission interruption flag.

As described above, in the present embodiment, at the start of the transmission operation, level carrier sense is first performed within a predetermined time range, and if a received signal is not detected within that time period, transmission is immediately performed. When the state of the wireless medium is empty, a short carrier sense is required and the throughput can be improved.

When a carrier is detected by level carrier sensing, correlation carrier sensing is performed within a predetermined time range, and when a correlation carrier (correlation peak) is detected within that time, the transmission operation is temporarily stopped. The procedure of suspending and monitoring the correlation carrier, and when no correlation carrier is detected, continues transmission standby for the back-off time, and after the back-off time has elapsed, repeats the procedure of performing level carrier sense again. . Therefore, the transmission operation is not interrupted by noise as in the case where only the level carrier sense is performed, and the throughput can be improved also in this regard.

Further, since a plurality of random back-off times are generated in advance and stored in the memory, and the stored back-off times are sequentially set in the back-off timer, the back-off timer is started quickly. In addition to this, the minimum unit of the back-off time can be reduced to shorten the transmission hold time, and in this regard, the throughput can be improved.

Further, since the transmission efficiency can be increased even if a digital matched filter is used for the correlator, the SAW
Compared to the case where a matched filter is used, downsizing, low power consumption, and low cost can be achieved.

Further, for example, for a transmission signal such as a radio section control signal which does not need to be transmitted because the state of the control program changes depending on the received signal, the above transmission processing is repeated and the transmission processing is stopped. ,
Useless transmission processing can be avoided.

The present invention is not limited to the above embodiment. For example, the generation process of the back-off time is not performed by the control unit 101 by software, but is performed by the transmission timing generation circuit 102 or the like in a hardware manner. It is also possible. As described above, when the back-off time is generated by hardware, the back-off time is generated in parallel with the level carrier sense time 201 and the correlation carrier sense time 207 at the timing when “1” is written in the data transmission flag. This allows the control unit 101 to start the transmission operation more quickly.

In the above embodiment, the level carrier signal 202 is not monitored in the carrier sense state 402, but the level carrier detection signal 203 is simultaneously monitored in the correlation carrier sense state 402 as shown in FIG. When the level carrier detection signal 203 becomes low level, it is possible to transition to the level carrier detection state 401 again and start from the level carrier sensing operation.

In this case, after a carrier is detected by the level carrier sense, the time required for the correlation carrier sense can always be secured, and it is possible to avoid erroneous transmission when there is a received signal, and to uselessly. Retransmission can be eliminated. Also, when the level carrier detection signal temporarily becomes high level due to noise when the transmission operation start command is output, and when the mode shifts to the correlation carrier sense, the carrier can be returned to the level carrier sense quickly. Even if an erroneous detection is made, the process immediately returns to the level carrier sense that can quickly perform the detection process, and the extra transmission standby time can be reduced.

[0062]

As described above, according to the present invention,
In a wireless communication device that performs transmission and reception asynchronously using the same frequency, a reception level detection unit that detects the presence or absence of a reception signal based on the signal strength level, a signal used by the wireless communication device, and a reception signal Correlation detection means for detecting the presence or absence of a received signal based on the presence or absence of a correlation with the received signal. When a reception signal is detected by the reception level detection means, the detection processing by the correlation detection means is executed. If there is, after a preset back-off time after the reception signal is no longer detected, transmission control means for performing the detection processing again from the detection processing by the reception level detection means, so that it is surely inexpensive configuration, In addition, it is possible to efficiently avoid communication collision.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a wireless communication device to which the present invention has been applied.

FIG. 2 is a timing chart showing transmission control when unnecessary radio waves do not exist in a wireless medium when performing a transmission operation.

FIG. 3 is a timing chart showing transmission control when noise or the like exceeding a threshold level exists on a wireless medium at the start of a transmission operation.

FIG. 4 is a timing chart showing transmission control when a correlation value with a received signal is obtained.

FIG. 5 is a timing chart showing transmission control when a received signal is no longer detected once a correlation value is obtained.

FIG. 6 is a flowchart showing an outline of transmission control by a control unit.

FIG. 7 is a state transition diagram during transmission control of a transmission timing generation circuit.

FIG. 8 is a state transition diagram showing an example of state transition at the time of transmission control of a transmission timing generation circuit different from that of FIG. 7;

[Explanation of symbols]

 101: Control unit 101a: CPU 101b: ROM 101c: RAM 102: Transmission timing control circuit 103: Timer register 104: Level detection circuit 105: Digital matched filter 106: Modulation circuit 107: Radio unit 115: Back-off timer 400: Transmission standby State 401: Level carrier sense state 402: Correlated carrier sense state 404: Detected carrier monitoring state 405: Backoff time count state 406: Backoff time update state 407: Transmission signal transfer state.

Claims (40)

[Claims] 1. A wireless communication apparatus that performs asynchronous transmission and reception using the same frequency, wherein the wireless communication apparatus uses reception level detection means for detecting the presence or absence of a received signal based on a signal strength level. A correlation detecting means for detecting the presence or absence of the received signal based on the presence or absence of a correlation between the signal and the received signal; and executing a detection process by the correlation detecting means when the received signal is detected by the reception level detecting means. Transmission control means for executing the detection processing again from the detection processing by the reception level detection means after a preset back-off time after the reception signal is not detected when there is a correlation. A wireless communication device characterized by the following. 2. The transmission control means causes the reception level detection means to simultaneously execute the detection processing when the correlation detection means executes the detection processing, so that no reception signal is detected by the reception level detection means. If
2. The wireless communication apparatus according to claim 1, wherein the detection process by the correlation detection unit is interrupted and the process is shifted to the detection process by the reception level detection unit. 3. The transmission control means stores a plurality of previously generated random back-off times in a memory as the back-off time, and each time the processing shifts to a detection process by the reception level detection means, 2. The next back-off time stored in the storage device is set.
The wireless communication device according to claim 1. 4. The wireless communication apparatus according to claim 3, wherein the plurality of random back-off times are generated in advance by software. 5. The wireless communication device according to claim 3, wherein the plurality of random back-off times are generated in advance by hardware. 6. The transmission control means, when a correlation reception signal is detected by the correlation detection means, stops repetition of detection processing and stops transmission processing for a predetermined transmission signal. The wireless communication device according to claim 1, wherein: 7. The wireless communication apparatus according to claim 1, wherein said transmission control means transmits a transmission signal when a reception signal is not detected within a predetermined time by said reception level detection means. 8. The transmission control means, even if a reception signal is detected by the reception level detection means, transmits a transmission signal if no correlation is obtained by the correlation detection means. The wireless communication device according to claim 1. 9. The apparatus according to claim 1, wherein the correlation detecting means detects presence or absence of a correlation between a signal used by the wireless communication apparatus and a received signal using a digital matched filter. Wireless communication device. 10. The radio communication apparatus according to claim 1, wherein said transmission control means modulates and transmits a transmission signal by a spread spectrum modulation method. 11. A wireless communication apparatus for performing asynchronous transmission and reception using the same frequency, wherein the wireless communication apparatus uses a reception level detecting step of detecting the presence or absence of a received signal based on a signal strength level. A correlation detection step of detecting the presence or absence of a reception signal based on the presence or absence of a correlation between the signal and the reception signal; and performing a detection process by the correlation detection step when the reception signal is detected by the reception level detection step. And a transmission control step of executing the detection processing again from the detection processing by the reception level detection step after a preset back-off time after the reception signal is no longer detected when there is a correlation. Characteristic wireless communication method. 12. The transmission control step, wherein when the detection processing in the correlation detection step is executed, the detection processing in the reception level detection step is also executed at the same time, and the reception signal is not detected in the reception level detection step. 12. The wireless communication method according to claim 11, wherein the detecting process in the correlation detecting process is interrupted and the process shifts to the detecting process in the receiving level detecting process. 13. The transmission control step, wherein a plurality of random back-off times generated in advance are stored in a memory as the back-off time, and each time the processing shifts to a detection process in the reception level detection step, the memory 12. The wireless communication method according to claim 11, wherein a next back-off time stored in the first communication unit is set. 14. The wireless communication method according to claim 13, wherein said plurality of random back-off times are generated in advance by software. 15. The wireless communication method according to claim 13, wherein said plurality of random back-off times are generated in advance by hardware. 16. The transmission control step includes, when a received signal having a correlation is detected in the correlation detection step, stopping the detection process and stopping the transmission process for a predetermined transmission signal. The wireless communication method according to claim 11, wherein: 17. The transmission control step, wherein a transmission signal is transmitted when a reception signal is not detected within a predetermined time by the reception level detection step.
2. The wireless communication method according to 1. 18. The transmission control step, wherein even if a reception signal is detected in the reception level detection step, if a correlation is not obtained in the correlation detection step, a transmission signal is transmitted. The wireless communication method according to claim 11. 19. The correlation detecting step according to claim 11, wherein the correlation detecting step detects, using a digital matched filter, whether or not there is a correlation between a signal or the like used by the wireless communication apparatus and the received signal. Wireless communication method. 20. The radio communication method according to claim 11, wherein said transmission control step modulates a transmission signal by a spread spectrum modulation method and transmits the modulated signal. 21. A wireless communication system for performing asynchronous transmission and reception using the same frequency, wherein the wireless communication system uses reception level detection means for detecting the presence or absence of a received signal based on a signal strength level. A correlation detecting means for detecting the presence or absence of the received signal based on the presence or absence of a correlation between the signal and the received signal; and executing a detection process by the correlation detecting means when the received signal is detected by the reception level detecting means. Transmission control means for performing the detection processing again from the detection processing by the reception level detection means after a preset back-off time after the reception signal is not detected when there is a correlation. A wireless communication system, characterized by: 22. The transmission control means, when executing the detection processing by the correlation detection means, simultaneously executes the detection processing by the reception level detection means, and the reception signal is not detected by the reception level detection means. 22. The wireless communication system according to claim 21, wherein, in the case of detecting, the detection process by the correlation detection unit is interrupted and the process is shifted to the detection process by the reception level detection unit. 23. The transmission control means stores a plurality of previously generated random back-off times in a memory as the back-off time, and stores the memory in the memory every time the processing shifts to a detection process by the reception level detection means. 22. The wireless communication system according to claim 21, wherein the next back-off time stored in is stored. 24. The wireless communication system according to claim 23, wherein the plurality of random back-off times are generated in advance by software. 25. The wireless communication system according to claim 23, wherein the plurality of random backoff times are generated in advance by hardware. 26. The transmission control means, when a correlation reception signal is detected by the correlation detection means, stops repetition of detection processing and stops transmission processing for a predetermined transmission signal. The wireless communication system according to claim 21, wherein: 27. The transmission control device according to claim 2, wherein the transmission signal is transmitted when the reception signal is not detected within a predetermined time by the reception level detection device.
2. The wireless communication system according to 1. 28. The transmission control means, if a correlation is not obtained by the correlation detection means, even if a reception signal is detected by the reception level detection means, transmits the transmission signal. The wireless communication system according to claim 21. 29. The correlation detecting apparatus according to claim 21, wherein the correlation detecting means detects presence or absence of a correlation between a signal used in the wireless communication system and a received signal using a digital matched filter. Wireless communication system. 30. The wireless communication system according to claim 21, wherein said transmission control means modulates and transmits a transmission signal by a spread spectrum modulation method. 31. A storage medium for storing a program executed by a wireless communication device that transmits and receives asynchronously using the same frequency, wherein the program detects the presence or absence of a received signal based on a signal strength level. A reception level detection routine for detecting the presence or absence of a reception signal based on the presence or absence of a correlation between a reception signal and a signal used by the wireless communication device; Is detected, the detection processing by the correlation detection routine is executed, and when there is a correlation, after a predetermined back-off time after the reception signal is no longer detected, the detection processing by the reception level detection routine is performed. A transmission control routine for executing the detection process again. 32. The transmission control routine, when executing the detection processing by the correlation detection routine, simultaneously executes the detection processing by the reception level detection routine,
32. The storage medium according to claim 31, wherein, when the reception signal is no longer detected by the reception level detection routine, the detection process by the correlation detection routine is interrupted and the process proceeds to the detection process by the reception level detection routine. 33. The transmission control routine stores a plurality of previously generated random back-off times in a memory as the back-off time, and stores the plurality of random back-off times in the memory each time the processing shifts to a detection process by the reception level detection routine. 32. The storage medium according to claim 31, wherein the next back-off time stored in the storage medium is set. 34. The storage medium according to claim 33, wherein said plurality of random back-off times are generated in advance by software. 35. The storage medium according to claim 33, wherein said plurality of random back-off times are generated in advance by hardware. 36. The transmission control routine according to claim 26, wherein, when a reception signal having a correlation is detected by said correlation detection routine, the repetition of the detection process and the transmission process are stopped for a predetermined transmission signal. The storage medium according to claim 31, characterized in that: 37. The storage medium according to claim 31, wherein said transmission control routine causes a transmission signal to be transmitted when a reception signal is not detected within a predetermined time by said reception level detection routine. 38. The transmission control routine, if a correlation is not obtained by the correlation detection routine even if a reception signal is detected by the reception level detection routine, a transmission signal is transmitted. The storage medium according to claim 31. 39. The correlation detection routine according to claim 31, wherein the correlation detection routine uses a digital matched filter to detect whether or not there is a correlation between a signal or the like used by the wireless communication system and a received signal. Storage medium. 40. The storage medium according to claim 31, wherein said transmission control routine modulates and transmits a transmission signal by a spread spectrum modulation method.