Transmission control circuit for digital radio communication system

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a transmission control circuit in a digital wireless communication communication system that communicates while coexisting with an interference wave transmitted at a high output in the same frequency band, and is particularly suitable for a CSMA / CA communication system and is affected by mutual interference. It relates to a transmission control circuit that segregates time with less time.

【0002】

[Conventional technology]

Conventionally, the transmission control circuit of the communication method used for time segregation using the same frequency includes a transmission control circuit for TAMA (Time Division Multiple Access) and carrier sense based on the received signal level. , There is a transmission control circuit for CSMA / CA (Carrier Sence Multiple Access / Collision Aviodance) that determines whether the frequency used is not used by other stations and performs transmission. Since the CSMA / CA communication method is a method of observing the desired transmission frequency for each transmitted packet, measuring whether it can be used, and then transmitting it, it is frequently used as a best-effort communication access method used in packet communication. It came to be used.

【0003】

A model of the conventional CSMA / CA communication method is shown in Fig. 6 (Reference: Draft International Standard ISO / IEC 8802-11, IEEE P802, 11 / D8, 0, 1 May 1998). In the CSMA / CA communication method, the desired transmission frequency can be observed before transmission, and the packet can be transmitted if another station is not transmitting. Immediately after the packet transmission of a certain radio station is completed and the radio channel changes from busy (in use) to idle (free), the collision probability of simultaneous packet transmission by a plurality of radio stations that have been suspended for transmission increases. In order to reduce this, each radio station stops the random time transmission, and after the random time elapses, it is confirmed that the channel is idle, and then the packet transmission is performed.

【0004】

In FIG. 6, the antenna circuit 601 receives the received signal (a), and the antenna circuit output signal (b) is input to the switch circuit 602. After that, it is input to the received signal level detection circuit 603 as a switch circuit output signal (c). In the received signal level detection circuit 603, the received signal level signal (d) is output and supplied to the received signal threshold circuit 604. The received signal threshold circuit 604 outputs the threshold circuit output signal (e) when the received signal level signal (d) is larger than the set threshold. The CSMA / CA transmission control circuit 605 determines that another station is transmitting when the threshold circuit output signal (e) is input, and transmits when the threshold circuit output signal (e) is not input. Is possible, and the control signal (f) is output to the signal transmission circuit 606. In the signal transmission circuit 606, the transmission signal (g) is transmitted according to the control signal (f), or the transmission signal (h) is transmitted based on the competitive control of CSMA / CA such as transmission stop. As described above, in the conventional transmission control circuit for CSMA / CA shown in FIG. 6, in order to transmit a packet after observing the usage state of another station at a desired transmission frequency, a packet collision on the transmission path occurs. This can be avoided, and transmission control suitable for best-effort communication can be performed.

【0005】

[Problems to be Solved by the Invention]

As described above, when communicating while competingly controlling lines at the same frequency, the CSMA / CA communication method avoids collisions and has excellent characteristics. However, when an interference wave is added to this transmission frequency, there is a problem that the collision avoidance function of the CSMA / CA communication method does not operate properly and the throughput decreases. This has a significant effect when the interference wave is intermittently transmitted as a pulse wave.

【0006】

For example, consider the case where a certain interference wave is transmitted as a pulse signal. In this case, if carrier sense is performed by the transmission control circuit of the CSMA / CA communication method, it is determined that there is no transmission signal from another station at the desired transmission timing, and the packet is transmitted, and then the packet length is long, During that time, interference wave pulses are transmitted, causing frequent problems of collision with packets. Especially in the case of long packets, the effect is remarkable. When a collision occurs, the packet does not reach the partner station, so the retransmission function of the upper layer operates, resulting in a decrease in throughput. As described above, there is a problem of interference that is affected by the interference station as seen from the CSMA / CA communication system side, such as a decrease in throughput.

【0007】

On the contrary, from the standpoint of the station transmitting the interference wave, when the packet is transmitted based on the CSMA / CA communication method when transmitting with a predictive pulse signal. This pulse signal is not received by the partner station in the correct form, and the packet signal becomes an interference wave for the interfering station. Therefore, when viewed from the CSMA / CA communication system side, there arises a problem of interference that causes deterioration of characteristics on the interference station side.

【0008】

As an example in which it is necessary to consider the case where such a CSMA / CA communication method and interference waves coexist at the same frequency, fixed wireless access between a base station and a fixed subscriber station outdoors ( FWA: Fixed Wireless Access) is conceivable. FWA is considering the application of the CSMA / CA communication method as an access method. Outdoors, various interference waves exist, and the period and transmission interval of the transmission signal fluctuate. Therefore, it is desired to apply a CSMA / CA communication method that can control packet transmission according to the communication environment.

【0009】

However, as described above, when an interference wave that transmits a pulse signal at an arbitrary transmission interval is added, the influence on each other is large. One of the sources of this interference is weather radar. The transmission output of the weather radar is very large, reaching about 250kW (about 84dBm). In addition, weather radar usually uses a parabolic antenna with sharp directivity while rotating at regular intervals to transmit pulses with a width of several microseconds toward the target hundreds of times per second. By receiving and averaging the reflected waves, the target is accurately captured. Since the radar wave is transmitted as a pulse wave in this way, the influence of interference and interference on the CSMA / CA communication method is significant.

【0010】

The present invention has been made in view of the above circumstances, and the transmission power difference between the transmitting station used in the CSMA / CA communication method and the interfering station represented by a weather radar or the like is large, and the pulse signal is repeatedly transmitted. In addition to the fact that the signal of the interfering station has a sharp directivity and is transmitted from an antenna that rotates at a constant cycle, it interferes separately from the threshold for receiving signal level detection used in the CSMA / CA communication method. It is equipped with a circuit equipped with a threshold for wave detection, and when an interference wave with a level exceeding the threshold for interference wave detection is applied, it is controlled to stop the transmission of the packet signal for a preset period, resulting in a large output. When communicating using the CSMA / CA communication method in the presence of the interference wave of, the influence of the interference is suppressed to avoid a decrease in throughput, and the influence of interference is suppressed to be characteristic of the interference station. An object of the present invention is to provide a transmission control circuit in a digital wireless communication system with suppressed deterioration.

【0011】

[Means for solving problems]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a received signal level detection circuit that detects the level of a received signal and outputs the received signal level information, and an output signal of the received signal level detection circuit. It is said that the received signal threshold circuit that is input and outputs a signal when this input signal exceeds a preset threshold, and that another station is transmitting when the output signal of the received signal threshold circuit is input. A digital radio including a first control circuit that determines and outputs a control signal that stops transmission of a signal, and a signal transmission circuit that stops transmission of the signal based on the control signal of the first control circuit. In the transmission control circuit in the communication system, a threshold value for interference waves different from the threshold value of the received signal is set, and when the output signal of the received signal level detection circuit is input and exceeds the threshold value for the interference wave, a signal is signaled. And a second control circuit that outputs a control signal that determines that an interference wave exists when the output signal of the interference signal threshold circuit is input and stops transmission of the signal. Therefore, when the output signal of the second control circuit is input to the signal transmission circuit, control is performed to stop the transmission. With the above configuration, the level judgment for interference wave detection is performed separately from the carrier sense level judgment in the CSMA / CA communication method, and when the interference wave level exceeds this, the signal transmission circuit stops the signal transmission. To do. As a result, when performing transmission-controlled packet communication using the CSMA / CA communication method, if a large output interference wave is added to the transmission frequency, the effects of interference and interference between the systems will be affected. It is possible to realize a digital wireless communication system that avoids this and suppresses the deterioration of throughput.

【0012】

The signal transmission control circuit in the digital wireless communication system according to claim 2 is the device according to claim 1, wherein a counter is provided between the interference signal threshold circuit and the second control means, and the counter is provided. Outputs a signal to the second control circuit when the output signal of the interference signal threshold circuit is input and a plurality of signals are input within a predetermined period, and the second control circuit causes the signal to be output. It was decided to stop the signal transmission. With the above configuration, a level judgment for interference wave detection is performed separately from the carrier sense level judgment in the CSMA / CA communication method, and when the interference wave level exceeds this, the counter circuit is operated multiple times in a predetermined period. When the interference wave pulse of is detected, the signal transmission circuit can stop the transmission of the signal. As a result, it is possible to realize a digital wireless communication system in which the influence of interference and interference between mutual systems is avoided when a large output interference wave is applied to the transmission frequency, and the deterioration of throughput is suppressed.

【0013】

The signal transmission control circuit in the digital wireless communication system according to claim 3 inputs the output signal of the second control circuit a plurality of times in the same device according to claim 1 or 2, and has a predetermined period cycle. An interference wave period estimation circuit that estimates the period of the incoming interference wave, and a timing estimation circuit that estimates the next stop start timing for stopping the transmission of the signal according to the estimation period estimated by the interference wave period estimation circuit. Further, the output signal of the timing estimation circuit is input to the signal transmission circuit to control the period of the next transmission stop. With the above configuration, the output signal of the second control circuit that indicates the stop timing is stored multiple times and averaged to estimate the rotation cycle that the interference wave arrives and affects the transmitting station of the CSMA / CA communication method. To do. Using this estimated value, the next stop start timing can be determined, and the signal transmission circuit can stop the signal transmission at this timing. As a result, it is possible to realize a digital wireless communication system in which the influence of interference and interference between mutual systems is avoided when a large output interference wave is applied to the transmission frequency, and the deterioration of throughput is suppressed.

【0014】

In the signal transmission control circuit in the digital wireless communication system according to claim 4, the output signal of the received signal level detection circuit is input in the same device according to claim 1 or 2, and the peak timing of the received signal is obtained. A peak timing detection circuit that outputs the timing signal, and an interference wave period estimation circuit that estimates the period of the interference wave that arrives at a predetermined period period from the timing signals input multiple times by the peak timing detection circuit. A timing estimation circuit that estimates the next stop start timing for stopping the transmission of the signal according to the estimation cycle estimated by the interference wave period estimation circuit is further provided, and the output signal of the timing estimation circuit is input to the signal transmission circuit. By doing so, it was decided to control the period of the next transmission suspension. With the above configuration, by detecting the peak timing of the received signal level and averaging the peak timing multiple times, it is possible to estimate the rotation cycle of the interference wave that affects the transmitting station of the CSMA / CA communication method. The estimated value is used to determine the next stop timing, at which time the signal transmission circuit stops transmitting the signal. As a result, it is possible to realize a digital wireless communication system in which the influence of interference and interference between mutual systems is avoided when a large output interference wave is applied to the transmission frequency, and the deterioration of throughput is suppressed.

【0015】

The signal transmission control circuit in the digital wireless communication system according to claim 5 is the same device according to claim 3 or 4, wherein the interference wave period estimation circuit has an interference wave period with an arbitrarily settable fixed time. It was decided to repeat the estimation and update. With the above configuration, the interference wave period estimation circuit that estimates the arrival period of the interference wave is repeatedly repeated and updated at a fixed time, so that interference between the mutual systems occurs when a high-power interference wave is added to the transmission frequency. , It is possible to realize a digital wireless communication system that avoids the influence of interference and suppresses the deterioration of throughput.

【0016】

The signal transmission control circuit in the digital wireless communication system according to claim 6 is the same device according to claim 3 or 4, wherein the transmission stop timing signal which is an output signal of the second control circuit and the transmission stop timing signal are used. By inputting the estimated transmission stop timing signal, which is the output signal of the timing estimation circuit, the difference between the stop start timings of both inputs is compared, and when the timing difference is large, the comparison circuit outputs an update signal. It is decided to have the interference wave period estimation circuit in which the update signal output by the comparison circuit is input and the interference wave period is estimated again. With the above configuration, the measured current signal transmission stop timing, which is the output signal of the second control circuit, and the transmission stop timing signal, which is the output signal of the timing estimation circuit, estimated based on the past start timing, are obtained. In comparison, if the difference is large, the interference wave period estimation circuit that estimates the arrival period of the interference wave is updated again. Therefore, when a high-output interference wave is added to the transmission frequency, the mutual systems are used. It is possible to avoid the influence of interference and interference and suppress the deterioration of throughput.

【0017】

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram showing an embodiment of a transmission control circuit in the digital wireless communication system of the present invention. In FIG. 1, the transmission control circuit includes an antenna circuit 101, a switch circuit 102, a received signal level detection circuit 103, a received signal threshold circuit 104, a CSMA / CA control circuit 105, a signal transmission circuit 106, an interference signal threshold circuit 107, and an interference wave. It is composed of a transmission control circuit 108.

【0018】

In the above configuration, first, the antenna circuit 101 receives the received signal (a) and supplies it to the switch circuit 102 as the antenna circuit output signal (b). In the switch circuit 102, the antenna circuit output signal (b) is further supplied to the received signal level detection circuit 103 as the switch circuit output signal (c). The received signal level detection circuit 103 supplies the received signal level signal (d) to the received signal threshold circuit 104. The reception signal threshold circuit 104 outputs the threshold circuit output signal (e) when the reception signal level signal (d) is larger than the preset threshold. In the CSMA / CA transmission control circuit 105, when the threshold circuit output signal (e) is input, it is determined that another station is transmitting, and when the threshold circuit output signal (e) is not input, the CSMA / CA transmission control circuit 105 determines that the signal is being transmitted. It is determined that transmission is possible, and a control signal (f) is output to the signal transmission circuit 106 to that effect, and CSMA / CA is controlled based on this signal. The operation up to this point is the same as the conventional example shown in FIG.

【0019】

On the other hand, the output signal (d) of the received signal level detection circuit 103 is also supplied to the interference signal threshold circuit 107. Here, unlike the received signal threshold circuit 104, a threshold for an interference wave having a large value is set in advance. The interference signal threshold circuit 107 compares with the threshold value for the interference wave, and when a signal having a level higher than the threshold value for the interference wave is input, the signal (i) by the interference signal threshold circuit 107 is output. To do. When this signal is input, the interference wave transmission control circuit 108 determines that the interference wave is being transmitted, and outputs a control signal (j) for stopping transmission to the signal transmission circuit 106. In the signal transmission circuit 106, CSMA / CA such as transmission of transmission signal or stop of transmission is performed according to the control signals (f) and (j) output by the CSMA / CA transmission control circuit 105 and the interference wave transmission control circuit 108, respectively. Competitive control and transmission control based on interference wave detection are performed, and the transmission signal (h) is output.

【0020】

FIG. 2 is a block diagram showing another embodiment of the present invention. In FIG. 2, the transmission control circuit includes an antenna circuit 201, a switch circuit 202, a received signal level detection circuit 203, a received signal threshold circuit 204, a CSMA / CA control circuit 205, a signal transmission circuit 206, an interference signal threshold circuit 207, and an interference wave. Transmission control circuit 208 Consists of counter circuit 209. The structural difference from the embodiment shown in FIG. 1 is that the counter circuit 209 is provided between the interference signal threshold circuit 207 and the interference wave transmission control circuit 208.

【0021】

In the above configuration, the antenna circuit 201 receives the received signal (a). The antenna circuit output signal (b) is input to the switch circuit 203, and then is input to the received signal level detection circuit 203 as the switch circuit output signal (c). The received signal level detection circuit 203 outputs the received signal level signal (d). The reception signal threshold circuit 204 outputs the threshold circuit output signal (e) when the reception signal level signal (d) is larger than the set threshold. In the CSMA / CA transmission control circuit 205, when the previous threshold circuit output signal (e) is input, it is determined that another station is transmitting, and when the threshold circuit output signal (e) is not input. Determines that transmission is possible, outputs a control signal (f) to the signal transmission circuit 206, controls CSMA / CA based on this signal, and outputs a transmission signal (h).

【0022】

On the other hand, the output signal (d) of the received signal level detection circuit 203 is also input to the interference signal threshold circuit 207. Here, unlike the received signal threshold circuit 204, a threshold for an interference wave having a large value is set. The interference signal threshold circuit 207 compares with the threshold value for the interference wave, and when a signal having a level higher than the threshold value for the interference wave is input, the output signal (i) of the interference signal threshold circuit 207 is output. To do. In the counter circuit 209, once the output signal (i) of the interference signal threshold circuit 207 is received, the output signal (i) is further input from the interference signal threshold circuit 207 for a certain period of time after the timer starts counting. If it is observed, it is determined that the interference wave has arrived at the CSMA / CA communication station, and the interference wave transmission control circuit 208 is operated by the counter circuit 209 output (k). When the counter circuit output signal (k) is input, the interference wave transmission control circuit 208 determines that the interference wave is being transmitted, and sends a control signal (j) to the signal transmission circuit 208 to stop transmission. Output. In the signal transmission circuit 206, CSMA / CA such as transmission of transmission signal or stop of transmission is performed according to the respective control signals (f) and (j) output by the CSMA / CA transmission control circuit 205 and the interference wave transmission control circuit 208. Competitive control and transmission control based on interference wave detection are performed, and the transmission signal (h) is output.

【0023】

FIG. 3 is a block diagram showing still another embodiment of the present invention. In FIG. 1, the transmission control circuit includes an antenna circuit 301, a switch circuit 302, a received signal level detection circuit 303, a received signal threshold circuit 304, a CSMA / CA control circuit 305, a signal transmission circuit 306, an interference signal threshold circuit 307, and an interference wave. It is composed of a transmission control circuit 308, an interference cycle estimation circuit 309, and a timing estimation circuit 310. The difference from the embodiment shown in FIG. 1 is that the interference period estimation circuit 309 and the timing estimation circuit 310 are further added to the components of the embodiment shown in FIG.

【0024】

In the above configuration, first, the antenna circuit 301 receives the received signal (a). The antenna circuit output signal (b) is input to the switch circuit 302, and then is input to the received signal level detection circuit 303 as the switch circuit output signal (c). The received signal level detection circuit 303 detects and outputs the received signal level signal (d). The reception signal threshold circuit 304 outputs the threshold circuit output signal (e) when the reception signal level signal (d) is larger than the preset threshold. In the CSMA / CA transmission control circuit 305, when the threshold circuit output signal (e) is input, it is determined that another station is transmitting, and when the threshold circuit output signal (e) is not input, it is determined that another station is transmitting. It is determined that transmission is possible, a control signal (f) is output to the signal transmission circuit 306, and CSMA / CA is controlled based on this signal.

【0025】

On the other hand, the output signal (d) of the received signal level detection circuit 303 is also input to the interference signal threshold circuit 307. Here, unlike the received signal threshold circuit 304, a threshold for an interference wave having a large value is set. The interference signal threshold circuit 307 compares with the threshold value for the interference wave, and when a signal having a level higher than the threshold value for the interference wave is input, the output signal (i) of the interference signal threshold circuit 307 is output. To do. When this signal is input, the interference wave transmission control circuit 308 determines that the interference wave is being transmitted, and outputs a control signal (j) for stopping transmission to the signal transmission circuit 306.

【0026】

Here, the control signal (j) is separately input to the interference wave period estimation circuit 309. In the interference wave period estimation circuit 309, the interference wave period is estimated by averaging the transmission stop timing indicated by the control signal (j) multiple times, and the estimation signal (l) is output by this to output the timing estimation circuit. Supply to 310. The timing estimation circuit 310 calculates and generates a signal that is the next transmission stop timing signal at the present time from the estimation signal (l), outputs the signal, and supplies the signal to the signal transmission circuit 306 as the transmission stop timing (m). .. In the signal transmission circuit 306, the transmission stop timing signal (m) output by the timing estimation circuit 310, the control signals (f) output by the CSMA / CA transmission control circuit 305, and the interference wave transmission control circuit 308, respectively, ( According to j), CSMA / CA competition control such as transmission or transmission stop of the transmission signal (g) and transmission control based on interference wave detection are performed, and the transmission signal (h) is output.

【0027】

FIG. 4 is a block diagram showing still another embodiment of the present invention. In FIG. 4, the transmission control circuit includes an antenna circuit 401, a switch circuit 402, a received signal level detection circuit 403, a received signal threshold circuit 404, a CSMA / CA control circuit 405, a signal transmission circuit 406, an interference signal threshold circuit 407, and an interference wave. It is composed of a transmission control circuit 408, an interference wave period estimation circuit 409, a timing estimation circuit 410, and a peak timing detection circuit 411. The difference from the embodiment shown in FIG. 3 is that the peak timing detection circuit 411 is provided between the received signal level detection circuit 403 and the interference cycle estimation circuit 409.

【0028】

In FIG. 4, first, the received signal (a) is received by the antenna circuit 401. The antenna circuit output signal (b) is input to the switch circuit 402, then is input to the received signal level detection circuit 403 as the switch circuit output signal (c), and the received signal level detection circuit 403 detects the received signal level signal. The signal (d) is output. The reception signal threshold circuit 404 outputs the threshold circuit output signal (e) when the reception signal level signal (d) is larger than the set threshold. In the CSMA / CA transmission control circuit 405, when the threshold circuit output signal (e) is input, it is determined that another station is transmitting, and when the threshold circuit output signal (e) is not input, it is determined that another station is transmitting. Judging that transmission is possible, the control signal (f) is output to the signal transmission circuit 406, and CSMA / CA is controlled based on this signal.

【0029】

On the other hand, the output signal (d) of the received signal level detection circuit 403 is also input to the interference signal threshold circuit 407. Here, unlike the received signal threshold circuit 404, a threshold for an interference wave having a large value is set. The interference signal threshold circuit 407 compares with the threshold for the interference wave, and outputs the output signal (i) of the interference signal threshold circuit when a signal having a level higher than the threshold for the interference wave is input. .. When this signal is input, the interference wave transmission control circuit 408 determines that the interference wave is being transmitted, and outputs a control signal (j) for stopping transmission to the signal transmission circuit 406.

【0030】

The output signal of the received signal level detection circuit 403 is also separately input to the peak timing detection circuit 411. The interference wave period estimation circuit 409 estimates the interference wave period by averaging the peak timings indicated by the peak timing detection signal (n) which is the output of the peak timing detection circuit 411, and as a result, the estimated signal ( l) is output. The timing estimation circuit 410 calculates and generates the next transmission stop timing signal at the present time from the previous estimation signal, and uses it as the transmission stop timing signal (m) to be supplied to the signal transmission circuit 406. In the signal transmission circuit 406, the transmission stop timing signal (m) output by the timing estimation circuit 410, the control signals (f) output by the CSMA / CA transmission control circuit 405, and the interference wave transmission control circuit 408, respectively, ( According to j), CSMA / CA competition control such as transmission or transmission stop of the transmission signal (g) and transmission control based on interference wave detection are performed, and the transmission signal (h) is output.

【0031】

FIG. 5 is a block diagram showing still another embodiment of the present invention. In FIG. 5, the transmission control circuit includes an antenna circuit 501, a switch circuit 502, a received signal level detection circuit 503, a received signal threshold circuit 504, a CSMA / CA control circuit 505, a signal transmission circuit 506, an interference signal threshold circuit 507, and an interference wave. It is composed of a transmission control circuit 508, an interference wave period estimation circuit 509, a timing estimation circuit 510, a peak timing detection circuit 511, and a comparison circuit 512. The difference from the embodiment shown in FIG. 4 is that a comparison circuit is provided in which the interference wave transmission control circuit 508 output and the timing estimation circuit 510 output are input and the comparison result is supplied to the interference wave period estimation circuit 509.

【0032】

In the above configuration, first, the received signal (a) is received by the antenna circuit 501. The antenna circuit output signal (b) is input to the switch circuit 502, and then is input to the received signal level detection circuit 503 as the switch circuit output signal (c). The received signal level detection circuit 503 detects and outputs the received signal level signal. The reception signal threshold circuit 504 outputs the threshold circuit output signal (e) when the reception signal level signal (d) is larger than the set threshold. In the CSMA / CA transmission control circuit 505, when the threshold circuit output signal (e) is input, it is determined that another station is transmitting, and when the threshold circuit output signal (e) is not input, it is determined that another station is transmitting. It is determined that transmission is possible, a control signal (f) is output to the signal transmission circuit 506, and CSMA / CA is controlled based on this signal.

【0033】

On the other hand, the output signal (d) of the received signal level detection circuit 503 is also input to the interference signal threshold circuit 507. Unlike the reception signal threshold circuit 504, the interference signal threshold circuit 507 is set with a threshold for interference waves having a large value. The interference signal threshold circuit 507 compares with the threshold for the interference wave, and outputs the output signal (i) of the interference signal threshold circuit when a signal having a level higher than the threshold for the interference wave is input. When this signal is input, the interference wave transmission control circuit 508 determines that the interference wave is being transmitted, and outputs a control signal (j) for stopping transmission to the signal transmission circuit 506. Here, the output signal (d) of the received signal level detection circuit 503 is separately input to the peak timing detection circuit 511. The interference wave period estimation circuit 509 estimates the interference wave period by averaging the peak timings indicated by the peak timing signal (n) a plurality of times, and outputs the estimated signal (l) to the timing estimation circuit 510. The timing estimation circuit 510 calculates the next transmission stop timing signal at the present time from this estimated signal, generates and outputs the signal, and sets the transmission stop timing (m) of the signal transmission circuit 506.

【0034】

The control signal (j) indicating the current transmission stop timing and the transmission stop timing signal (m) indicating the transmission stop timing estimated based on the past values are input to the comparison circuit 512. The comparison circuit 512 compares the timing difference between the two inputs, and if the difference is large, the update signal (o) is output again so as to estimate the interference wave period, and the interference wave period estimation circuit 509 outputs the interference wave. The cycle is re-estimated. In the signal transmission circuit 506, the transmission stop timing signal (m) output by the timing estimation circuit 510, the control signals (f) output by the CSMA / CA transmission control circuit 505, and the interference wave transmission control circuit 508, respectively, ( According to j), CSMA / CA competition control such as transmission or transmission stop of the transmission signal and transmission control based on interference wave detection are performed, and the transmission signal (h) is output.

【0035】

[Effect of the invention]

As described above, the present invention has a large difference in transmission power between a transmission station used in the CSMA / CA communication method and an interference station represented by a meteorological radar, and is repeatedly transmitted as a pulse signal. Utilizing the fact that the signal of the interference station has sharp directivity and is transmitted from an antenna that rotates at a fixed cycle, a threshold for interference wave detection is used in addition to the threshold for reception signal level detection used in the CSMA / CA communication method. When an interference wave having a level exceeding the threshold value for detecting the interference wave is applied, the control is performed to stop the transmission of the packet signal for a preset period. As a result, the level for interference wave detection is determined separately from the carrier sense level determination in the CSMA / CA communication method, and when the interference wave level exceeds this, the signal transmission circuit stops transmitting the signal. By doing so, when performing transmission-controlled packet communication using the CSMA / CA communication method, if a large output interference wave is added to the transmission frequency, the effects of interference and interference between the mutual systems will be affected. It is possible to realize a digital wireless communication system that avoids this and suppresses the deterioration of throughput.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows one Embodiment of the transmission control circuit in the digital wireless communication system of this invention.

[Figure 2]

It is a block diagram which shows the other embodiment of the transmission control circuit in the digital wireless communication system of this invention.

[Fig. 3]

It is a block diagram which shows still another embodiment of the transmission control circuit in the digital wireless communication system of this invention.

[Fig. 4]

It is a block diagram which shows still another embodiment of the transmission control circuit in the digital wireless communication system of this invention.

[Fig. 5]

It is a block diagram which shows still another embodiment of the transmission control circuit in the digital wireless communication system of this invention.

[Fig. 6]

It is a block diagram which shows the internal structure of the transmission control circuit in the conventional digital wireless communication system.

[Explanation of symbols]

101 (201, 301, 401, 501) ... antenna circuit, 102 (202, 302, 402, 502) ... switch circuit, 103 (203, 303, 403, 503) ... received signal level detection circuit , 104 (204, 304, 404, 504) ... Received signal threshold circuit, 105 (205, 305, 405, 505) ... CSMA / CA transmission control circuit, 106 (206, 306, 406, 506). .. Signal transmission circuit, 107 (207, 307, 407, 507) ... Interference signal threshold circuit, 108 (208, 308, 408, 508) ... Interference wave transmission control circuit, 209 ... Counter circuit, 309 (409, 509) ... interference wave period estimation circuit, 310 (410, 510) ... timing estimation circuit, 411 (511) ... peak timing detection circuit, 512 ... comparison circuit