JP2001358721A - Transmitter circuit for digital wireless communication - Google Patents

Abstract

(57) [Summary] [Problem] To perform communication while coexisting with the same system and another system different from the own system at the same frequency, to surely detect the reception level value of the interference wave and to interfere with the other system. Avoid giving. An interference signal level detection circuit for detecting a reception level of an interference signal from another system, and a transmission permission period for permitting transmission are calculated based on the interference signal reception level obtained by the interference signal level detection circuit. A transmission permission period calculation circuit 105, a signal transmission circuit 106 that receives a transmission signal and an output signal of the transmission permission period calculation circuit 105, and is capable of transmitting a transmission signal in a period permitted by the output signal of the transmission permission period calculation 105; A frame setting circuit 107 receives a frame synchronization signal between the own system stations, and periodically sets an interference wave detection period in which frames are synchronized between the stations based on the synchronization signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system used in a digital radio communication system for performing communication by sharing the same frequency with another station, and in particular, coexistence with another system different from its own system at the same frequency. The present invention relates to a transmission circuit for digital wireless communication for performing transmission by time segregation in order to suppress mutual influence.

[0002]

2. Description of the Related Art Conventionally, when sharing the same frequency with another system using the same frequency, interference between one system and another system or interference from another system to the own system occurs between the systems. There was a problem. In the present specification, as another example of the interference,
Description will be made assuming a weather radar in which an interference wave is intermittently transmitted as a pulse wave. Since the transmission output of a weather radar is very large and is about 250 KW (about 84 dBm), the interference of the own system is great.

A weather radar transmits a pulse wave having a width of several microseconds several hundred times a second toward a target using a parabolic antenna or the like having a sharp directivity while rotating it at a constant period, and reflecting the reflected wave. A system that accurately captures targets by receiving and averaging waves. Therefore, when an interference wave from the own system is received by the radar receiving station, erroneous rainfall information is generated, and it is essential that interference is not given to the radar receiving station.

[0004]

Therefore, in order to suppress the interference and interference between the radar and the own system, the radar directivity is controlled by utilizing the operation of the radar while rotating the antenna. The operation of prohibiting (stopping) the transmission of the own system when facing the station is an effective measure for avoiding interference and interference. One way to achieve this is to measure the reception level of the radar reception wave,
It is conceivable that the wave stops when the reception level value is large.

[0005] When sharing with another system while avoiding general interference using the same frequency, communication of the own system is stopped, that is, wave interruption is performed to prevent interference and interference between the systems. As a method of reducing the power consumption, the present inventor has already proposed in Japanese Patent Application No. 2000-046510 a “transmission control circuit in a digital radio communication system”. FIG. 9 shows the configuration of this transmission control circuit. In the figure, a reception signal s1 is received by an antenna circuit 1,
The output signal s2 of the antenna circuit 1 is input to the switch circuit 2. After that, the output signal s3 of the switch circuit 2 is input to the interference signal level detection circuit 3, and the interference signal level detection circuit 3 detects the signal of the interference wave transmitted at the same frequency as the own system.

The interference signal level detection circuit 3 outputs a detection signal s 4 indicating the level of the detected interference signal to the interference signal level determination circuit 4. The interference signal level determination circuit 4 outputs a level determination output signal s5 when the detection signal s4 exceeds a set threshold. When the level determination output signal s5 is input to the transmission control circuit 5, the transmission control signal s6 for performing control to stop transmission is transmitted to the signal transmission circuit 6.
Output to When the level determination output signal s5 is not input, the transmission control circuit 5 transmits a transmission control signal s6 for controlling transmission of the transmission signal s7 to the signal transmission circuit 6.
Output to The signal transmission circuit 6 obtains a transmission signal s8 whose transmission has been controlled in accordance with the transmission control signal s6. As described above, in the transmission circuit for digital wireless communication shown in FIG. 9, by interrupting the own system before affecting other systems, interference with other systems and interference received from other systems can be prevented. Can be avoided.

In order to ensure that no interference is caused when a stop operation is performed based on the reception level of an interference wave, a margin is set in consideration of a detection error, and reception is started to cause interference between systems. It is conceivable that the wave stops when a level lower than the level is detected. But,
In this case, the required propagation loss for not giving interference to each other increases, and the use area of the own system decreases. Further, since the time during which the wave stops is increased, there is a problem that the throughput is reduced.

In order to avoid this, there is also a technique for detecting the reception level of the interference signal from the output signal of the interference level detection circuit and performing transmission control so as to set a period in which transmission is permitted according to the detected reception level. Have been proposed by other inventors. In this case, it is possible to calculate the period until the reception level of the interference wave reaches the level at which each system causes interference. Avoid or
Transmission control for suppressing a decrease in throughput is also conceivable.

In order to suppress interference with other systems,
It is effective to stop the wave of the own system, but to stop the wave, it is necessary to measure the reception level of the interference wave and detect the value. Here, looking at the relationship between other systems and the own system, frequency segregation with other systems is possible, and frequency segregation is impossible because the frequency used by other systems is always shared. 2 with the case
Can be divided into two. If frequency segregation is possible, it is possible to measure the reception level of interference waves during transmission and reception of the own system, but if frequency segregation is not possible, measure interference waves from other systems. In this case, the transmission / reception signal of the own system affects the measured value of the interference wave level, so that it is difficult to detect the reception level of the interference wave from another system while transmitting / receiving the own system.

As a specific example, assuming that the other system is a weather radar, when the transmitting direction of the weather radar and the own system approach a close relationship, it is attempted to stop the own system station. However, since the radar wave is transmitted using a directional antenna having a steep directivity, there is a fluctuation in the reception level of up to 10 dB per one pulse period. It is relatively long, about 4 ms, and is difficult to detect. As described above, when the signal of the own system is transmitted and received at the same frequency, it is very difficult to detect the reception level of the interference wave from another system that has a large level fluctuation and arrives at a low frequency in time. become.

That is, during transmission to the own system station, the reception level of the interference wave output from the other system cannot be measured, and the reception level of the own system station equal to or higher than the reception level of the interference wave cannot be measured. There is a problem that it is difficult to measure the reception level of the interference wave while receiving the transmitted signal. The present invention has been made in view of such circumstances, and when performing communication while coexisting with the other system different from the own system at the same frequency, it is possible to reliably detect the reception level value of the interference wave. It is an object of the present invention to provide a transmission circuit for digital wireless communication that can perform the operation and avoid interference with other systems.

[0012]

SUMMARY OF THE INVENTION In the present invention, when frequency segregation is not possible between systems, the above-mentioned problem is solved by the following means for accurately measuring the reception level of an interference wave from another system. Has been resolved. 1. Perform time division and periodically set the interference wave detection period, detect the reception level of the interference wave, or perform the carrier sense for the interference wave over the interference wave cycle time,
To detect the reception level of the interference wave. 2. Do not transmit from the own station during the interference wave detection period. It is a feature of the present invention that by using this solution, it is possible to detect an interference wave even when sharing the same frequency with another system.

When the reception level of the interference wave is measured during the interference wave detection period, a period in which transmission is possible according to the reception detection level is calculated, and transmission is enabled within the calculated period. By performing the control, the use area is prevented from decreasing. If no interference wave is detected, the maximum allowable transmission period can be set based on the parameters of the other system to be shared. By performing interference wave detection for each transmission allowable period, a decrease in throughput can be prevented. Preventing. FIG. 5 shows the relationship of the transmission permission period when the interference wave output from the radar is detected.
In FIG. 5, the transmission permission period is set after performing radar carrier sensing for one or more interference wave periods, but the next transmission permission period is Ta transmission according to the detected interference wave reception level. It shows a state where it is reduced by the time.

According to the first aspect of the present invention, there is provided an interference signal level detecting means for receiving a received signal and detecting a reception level of an interference signal from another system, and the interference signal level detecting means. An output signal is input, and transmission permission period calculation means for calculating a transmission permission period for permitting transmission based on the interference signal reception level obtained by the interference signal level detection means; and a transmission signal and the transmission permission period calculation means. An output signal is input, and a transmission circuit for a digital radio communication system having a signal transmission unit capable of transmitting the transmission signal in a period permitted by the output signal of the transmission permission period calculation unit. Frame setting means for receiving a frame synchronization signal and periodically setting an interference wave detection period frame-synchronized between the stations based on the synchronization signal A, the transmission permission period calculating means, the output signal of the frame setting means is input, and controlling the signal transmission means to perform a transmission other than the interference wave detection period.

According to the first aspect of the invention, the synchronized interference wave detection period is periodically set at each station of the own system, and the communication is performed by switching the interference wave detection period and the transmission / reception period of each station at the same timing. Therefore, since no signal arrives from the own system during the interference wave detection period, the reception level of the interference wave can be detected with high accuracy.

According to a second aspect of the present invention, there is provided an interference signal level detecting means for receiving a received signal and detecting a reception level of an interference signal from another system, and an output signal of the interference signal level detecting means. A transmission permission period calculating means for calculating a transmission permission period for permitting transmission based on the interference signal reception level obtained by the interference signal level detecting means; a transmission signal and an output signal of the transmission permission period calculation means; A transmission circuit for a digital wireless communication system having a signal transmission unit capable of transmitting the transmission signal in a period permitted by an output signal of the transmission permission period calculation unit, wherein the signal transmission unit terminates transmission. Timer means which is reset at and starts measurement for a predetermined period,
A receiving signal level detecting means for receiving a receiving signal and detecting a signal receiving level of the own system, and an output signal of the receiving signal level detecting means being input, and determining whether or not the input signal exceeds a set threshold value Receiving signal level determination means to perform, the timer means, the output signal of the reception signal level determination means is input, reset the time measured when it is determined that the reception signal of its own system has arrived, The transmission permission period calculating unit receives the output signal of the timer unit, and when the period measured by the timer unit is equal to or longer than the predetermined period, reduces the interference signal reception level obtained by the interference signal level detecting unit. The transmission permission period is calculated based on the transmission permission period.

According to the second aspect of the present invention, the detection of the interference wave is realized by performing the carrier sense for the interference wave without requiring the frame synchronization between the stations. When a predetermined interference wave detection period in which no interference wave is detected can be secured, communication is performed with a transmission permission period provided.

The invention described in claim 3 is the same as the invention described in claim 2.
3. The transmission circuit for a digital radio communication system according to claim 1, further comprising the step of starting the transmission permission period based on a control signal output from said transmission permission period calculating means and instructing the transmission permission period to start. A permission signal generating means for outputting a signal known to the signal transmitting means to the signal transmitting means, wherein the transmission permission period calculating means is configured to, when the time period measured by the timer means is equal to or longer than the predetermined time period, cause the interference signal The transmission permission period is calculated based on the interference signal reception level obtained by the level detection unit, and a signal indicating the transmission permission period is output to the signal transmission unit, and the transmission permission period starts at the start of the transmission permission period. An instruction control signal is output to the permission signal generation means, and the signal transmission means starts the transmission permission period output from the transmission permission period calculation means. And transmitting an output signal of the first to the permission signal generation means of the transmission grant period based on Shimesuru control signal.

According to the invention of claim 3, according to claim 2,
Has the same features as the invention described in (1). That is, the detection of the interference wave is realized by performing the carrier sense for the interference wave without the need for the frame synchronization control between the stations.

The invention described in claim 4 is the third invention.
A digital radio communication system comprising a base station having a transmission circuit for a digital radio communication system according to claim 1 and a plurality of subscriber stations under the jurisdiction of the base station, wherein the subscriber station is An interference signal level detecting means for receiving a reception signal and detecting a reception level of an interference signal from another system, and receiving an interference signal obtained by the interference signal level detection means and receiving an output signal of the interference signal level detection means A transmission permission period calculating means for calculating a transmission permission period for permitting transmission based on the level, a transmission signal and an output signal of the transmission permission period calculation means being inputted, and a period permitted by the output signal of the transmission permission period calculation means A signal transmitting means capable of transmitting the transmission signal; and a timer which is reset when the signal transmitting means ends transmission and starts measurement for a predetermined period. Means, a reception signal level detection means for receiving a reception signal and detecting a signal reception level of the own system, and an output signal of the reception signal level detection means is inputted, and whether or not this input signal exceeds a set value Receiving means for determining whether the received signal is received, and demodulating means for receiving and demodulating the received signal. The timer means receives the output signal of the received signal level determining means and receives the received signal of the own system. When it is determined that the time has been measured, the time measured is reset, and the transmission permission period calculating means determines that the period measured by the timer means is equal to or longer than the predetermined period, and that the input output signal of the demodulation means is permitted. When indicating that the reception of the signal has been confirmed, the transmission permission period is calculated based on the interference signal reception level obtained by the interference signal level detecting means, and the transmission permission period is calculated. Characterized in that it has a digital radio communication system transmitter circuit that facilitates transmission from said signal transmitting means at between.

The invention according to claim 4 has the same features as the invention according to claim 2. That is, the frame synchronization between the stations is not required, and the detection of the interference wave is realized by performing the carrier sense for the interference wave for each transmission permission period. When the interference wave is not detected and the predetermined detection period can be secured, communication is performed with a transmission permission period provided.

According to the invention set forth in claims 1 to 4, by providing the means described in each claim, when performing communication while coexisting with the own system and another system different from each other at the same frequency, A transmission circuit for digital wireless communication and a subscriber station of a digital wireless communication system capable of reliably detecting an interference wave reception level value and avoiding interference with other systems can be realized.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a transmission circuit for digital wireless communication according to a first embodiment of the present invention. In the figure, a transmitting circuit for digital wireless communication according to the present embodiment includes an antenna circuit 101 and a switch circuit 102.
Signal level detection circuit 103 for receiving a reception signal and detecting the reception level of an interference signal from another system.
And an output signal of the interference signal level detection circuit 103, and a transmission permission period calculation circuit 105 for calculating a transmission permission period for permitting transmission based on the interference signal reception level obtained by the interference signal level detection circuit 103; The signal and the output signal of the transmission permission period calculation circuit 105 are input, and during the period permitted by the output signal of the transmission permission period calculation 105, the signal transmission circuit 106 capable of transmitting the transmission signal and the frame synchronization signal between the own system station are transmitted. And a frame setting unit 107 for periodically setting an interference wave detection period that is input and frame-synchronized between the stations based on the synchronization signal. The transmission permission period calculation circuit 105 receives the output signal of the frame setting circuit 107 and controls the signal transmission circuit 106 to perform transmission during a period other than the interference wave detection period.

In the above configuration, the received signal s101 is received by the antenna circuit 101, and the output signal s102 of the antenna circuit 101 is input to the interference signal level detection circuit 103 via the switch circuit 102 as the output signal s103 of the switch circuit 102. . On the other hand, the frame setting circuit 1
To 07, a frame synchronization signal s109 between the own system is input. Based on this signal s109, frame synchronization of an interference detection period is obtained, and a control signal s110 indicating the timing and the interference detection period is output. The interference signal level detection circuit 103 detects the signal level of the interference wave, and outputs a level detection signal s104 indicating the level of the interference signal to the transmission permission period calculation circuit 105.

The transmission permission period calculation circuit 105 calculates a transmission permission period according to the reception level of the input level detection signal s104, and performs transmission control for permitting transmission of the own system within the period. The signal s106 is output to the signal transmission circuit 106. In the signal transmission circuit 106,
According to the transmission control signal s106, the transmission signal s107 is transmitted from the antenna circuit 101 via the switch circuit 102 only during the transmission permission period.

FIG. 6 shows an operation state of the transmission circuit for digital wireless communication according to the first embodiment of the present invention. In the figure, one cycle of the interference wave detection period Tr and the transmission permission period Ttx is shown. The reference signal for frame synchronization between the own systems may be known from the base station by radio or wire. In addition, each station is GPS (Gl
Obviously, synchronization may be provided with a time reference such as an obal positioning system. The interference signal level detection circuit 103, the transmission permission period calculation circuit 105, the signal transmission circuit 106, and the frame setting circuit 107 are respectively an interference signal level detection unit, a transmission permission period calculation unit,
It corresponds to a signal transmitting unit and a frame setting unit.

According to the transmission circuit for digital radio communication according to the first embodiment of the present invention, the interference wave detection period synchronized with each station of the own system is periodically set, and the interference wave detection period of each station and the transmission / reception period are set. Since the switching is performed at the same timing and the communication is performed, no signal arrives from the own system during the interference wave detection period, so that the reception level of the interference wave can be detected with high accuracy.

FIG. 2 shows the configuration of a transmission circuit for digital wireless communication according to a second embodiment of the present invention. The transmission circuit for digital wireless communication according to the present embodiment does not require frame synchronization between stations, and realizes detection of an interference wave by performing carrier sensing for the interference wave. When a predetermined measurement period during which no interference wave is detected can be secured, communication is performed with a transmission permission period provided.

In FIG. 2, a transmitting circuit for digital radio communication according to the present embodiment includes an antenna circuit 201, a switch circuit 202, and an interference circuit which receives a received signal and detects a reception level of an interference signal from another system. A signal level detection circuit 203 and an output signal of the interference signal level detection circuit 203 are input, and a transmission permission period calculation for calculating a transmission permission period for permitting transmission based on the interference signal reception level obtained by the interference signal level detection circuit 203. A circuit 205;
The signal transmission circuit 2 capable of transmitting the transmission signal and the output signal of the transmission permission period calculation circuit 205 during a period when the output signal of the transmission permission period calculation circuit 205 permits.
06, a timer circuit 21 that is reset when the signal transmission circuit 206 completes transmission and starts measurement for a predetermined period.
1, a reception signal level detection circuit 209 that receives a reception signal and detects a signal reception level of the own system, and an output signal of the reception signal level detection circuit 209, and determines whether the input signal exceeds a set threshold value. And a reception signal level judgment circuit 210 for judging whether or not the signal is received.

The timer circuit 211 receives the output signal of the reception signal level determination circuit 210 and resets the time measured when it is determined that the reception signal of the own system has arrived. Timer circuit 21
When the output signal of “1” is input and the period measured by the timer circuit 211 is equal to or longer than the predetermined period, the transmission permission period is calculated based on the interference signal reception level obtained by the interference signal level detection circuit 203.

In the above configuration, the reception signal s201 is received by the antenna circuit 201, and the output signal s202 of the antenna circuit 201 is input to the interference signal level detection circuit 203 via the switch circuit 202 as the output signal s203 of the switch circuit 202. . Interference signal level detection circuit 2
At 03, the signal level of the interference wave is detected, and a level detection signal s204 indicating the level of the interference wave is output to the transmission permission period calculation circuit 205. Transmission permission period calculation circuit 20
In 5, when the time measured by the timer circuit 211 is equal to or longer than the set time, the transmission permission period is calculated from the reception level of the input level detection signal s204 and s204, and the control for permitting the transmission during this period is performed. Is transmitted to the signal transmission circuit 206.

On the other hand, the reception signal level detection circuit 209 detects the level of the reception signal, and outputs a level detection signal s211 indicating the level of the reception signal to the reception signal level determination circuit 210. Received signal level determination circuit 210
Then, when the level detection signal s211 exceeds the set threshold, the level determination signal s212 is set to the timer circuit 211.
Output to In the timer circuit 211, the level determination signal s
When 212 is input and the received signal of the own system is received, the measurement time is reset. Also, the timer circuit 211 has a transmission signal s from the signal transmission circuit 206.
Even after the output of 207, the reset signal s213 is input, and the measurement time is reset.

Transmission by the signal transmission circuit 206 is performed during a transmission permission period permitted by the control signal s206, and an output signal s208 of the signal transmission circuit 206 is transmitted from the antenna circuit 201 via the switch circuit 202. . FIG. 7 shows an operation state of the transmission circuit for digital wireless communication according to the present embodiment. The figure shows a state in which carrier sensing is performed until a fixed period length Tr is secured before signal transmission, and then transmission is performed. If a carrier sense period over the fixed period length Tr can be secured, a transmission permission period is set.

As shown in FIG. 2, when a received signal from another station of the own system arrives during the interference wave detection period, the carrier sense period measured by the timer circuit is reset. Carrier sense is performed again until the measurement period Tr is secured. Alternatively, the carrier sense circuit is reset also when the own system has completed the transmission.
Also, in the present embodiment, frame synchronization control between stations is not necessary, but if operation is performed such that an interference wave detection period at substantially the same time is set between the own systems, reception from other stations of the own system can be performed. Since the effect of suppressing the reset of the timer circuit can be expected by the signal, it is preferable that the radar carrier sense circuit operates continuously during the transmission permission period.

The interference signal level detection circuit 203, the transmission permission period calculation circuit 205, the signal transmission circuit 206, the timer circuit 211, the reception signal level detection circuit 209, and the reception signal level determination circuit 210 are each an interference signal of the present invention. These correspond to level detecting means, transmission permission period calculating means, signal transmitting means, timer means 211, received signal level detecting means, and received signal level determining means.

Next, a transmission circuit for digital wireless communication according to a third embodiment of the present invention will be described. The transmission circuit for digital wireless communication according to the present embodiment has the same features as the second embodiment. That is, the detection of the interference wave is realized by performing the carrier sense for the interference wave without requiring the frame synchronization control between the stations. When the own system signal is not detected and the predetermined measurement period can be secured, communication is performed with a transmission permission period provided.

The transmitting circuit for digital wireless communication according to the third embodiment of the present invention also has the operation state of the transmitting circuit for digital wireless communication according to the second embodiment as shown in the timing chart of FIG. Then, before signal transmission, carrier sensing is performed until a fixed period length Tr is secured, and then transmission is performed. Also, as shown in FIG. 7, when a received signal from another station of the own system arrives during the carrier sense period for interference waves, the carrier sense period measured by the timer circuit is reset. Then, the carrier sense is performed again until the measurement period Tr is secured. Or,
The carrier sense circuit is also reset when the own system ends transmission.

FIG. 3 shows the configuration of a transmission circuit for digital wireless communication according to a third embodiment of the present invention. The transmission circuit for digital wireless communication according to the present embodiment differs in configuration from the transmission circuit for wireless communication according to the second embodiment shown in FIG. A permission signal generation unit 312 for outputting a signal notifying the start of the transmission permission period to a subscriber station in the own cell to the signal transmission circuit 306 based on a control signal instructing the start of the permission period; If the period measured by the timer circuit 311 is equal to or longer than a predetermined period, the circuit 305 calculates a transmission permission period based on the interference signal reception level obtained by the interference signal level detection circuit 303, and determines the transmission permission period. Is output to the signal transmission circuit 306, and at the start of the transmission permission period, a control signal instructing the start of the transmission permission period is output to the permission signal generation circuit 312. Is the point that you configured, other configurations are the same.

In the above configuration, the reception signal s301 is received by the antenna circuit 301, and the output signal s302 of the antenna circuit 301 is input to the interference signal level detection circuit 303 via the switch circuit 302 as the output signal s303 of the switch circuit 302. . Interference signal level detection circuit 3
At 03, the signal level of the interference wave is detected, and a level detection signal s304 indicating the level of the interference signal is output to the transmission permission period calculation circuit 305. Transmission permission period calculation circuit 3
In 05, when the time measured by the timer circuit 311 is secured for the set time or more, the transmission permission period is calculated from the reception level of the input level detection signal s304, and the control for permitting the transmission during this period is performed. Do.

When the transmission permission period has been secured,
The transmission permission period calculation circuit 305 includes a permission signal generation circuit 312.
A control signal s315 for instructing the transmission of a permission signal is output to the signal transmission circuit 306 after the output of the permission signal. On the other hand, the reception signal level detection circuit 309 detects the level of the reception signal, and outputs a level detection signal s311 indicating the level of the reception signal to the reception signal level determination circuit 310. The reception signal level determination circuit 310 outputs a level determination signal s312 to the timer circuit 311 when the level detection signal s311 exceeds the set threshold.

The level determination signal s312 is input to the timer circuit 311 and the measurement period is reset when a reception signal of the own system is received. The reset signal s313 is input to the timer circuit 311 after the transmission signal s307 is output from the signal transmission circuit 306, and the measurement period is reset.

In the signal transmission circuit 306, after transmitting the permission signal s316 that informs the start of the transmission permission period output from the permission signal generation circuit 312, the transmission signal s307 is transmitted in the transmission permission period permitted by the control signal s306. You. An output signal s308 of the signal transmission circuit 306 is transmitted from the antenna circuit 301 via the switch circuit 302.

The transmission circuit for a digital radio communication system according to the present embodiment does not require frame synchronization control between stations, but operates so that the interference wave detection period is set at substantially the same time between its own systems. In this case, the effect of suppressing the reset of the timer circuit can be expected by a signal received from another station of the own system. Therefore, it is preferable that the radar carrier sense circuit operates continuously during the transmission permission period. Here, a significant feature of the transmission circuit for a digital wireless communication system according to the third embodiment is that the transmission period for
When Tr is secured, a permission signal is transmitted.

FIG. 8 shows a case where the transmission circuit for a digital radio communication system according to the third embodiment is applied to a base station constituting a digital radio communication system. The base station secures a Tr measurement period, and thereafter transmits a permission signal to set a transmission permission period (transmission / reception period) 1. If it is assumed that the radar carrier sense circuit continues to operate even during the transmission permission period, if a new Tr measurement period can be secured, the permission signal is transmitted again to transmit the transmission permission period (transmission / reception period) 2. And the transmission is started.

The transmission circuit for a digital radio communication system according to the third embodiment applies the transmission circuit for a digital radio communication system according to the third embodiment to a base station of each cell in the digital radio communication system. The effect is great when the transmission circuit for a digital wireless communication system according to the fourth embodiment shown in FIG. Here, the start timing of the transmission permission period depends on the base station using the permission signal, but the reception level detection of the interference wave is performed for each station, so that the response according to the reception level of the interference wave at each station is performed. Becomes possible. A configuration is also conceivable in which an interference wave level detection function is provided only in the base station, and the subscriber station sets a transmission permission period on the condition of a permission signal coming from the base station. The permission signal generation circuit 312, the transmission permission period calculation unit 305, and the signal transmission circuit 306 correspond to a permission signal generation unit, a transmission permission period calculation unit, and a signal transmission unit, respectively.

Next, a transmitting circuit for a digital radio communication system according to a fourth embodiment of the present invention will be described. The transmission circuit for a digital radio communication system according to the present embodiment has the same features as the transmission circuit for a digital radio communication system according to the second embodiment. That is, the detection of the interference wave is realized by performing the carrier sense for the interference wave for each transmission permission period without requiring the frame synchronization between the stations. If no interference wave is detected and the predetermined measurement period can be secured, communication is performed with a transmission permission period provided.

The transmission circuit for digital radio communication according to the fourth embodiment of the present invention also has the operation state of the transmission circuit for digital radio communication according to the second embodiment, as shown in the timing chart of FIG. Then, before signal transmission, carrier sensing is performed until a fixed period length Tr is secured, and then transmission is performed. As shown in FIG. 7, when a received signal from another station of the own system arrives during the carrier sense period for the interference wave, the carrier sense period that has been measured by the timer circuit is reset and again. Carrier sense is performed until the measurement period Tr is secured. Alternatively, the carrier sense circuit is reset also when the own system has completed the transmission.

FIG. 4 shows a configuration of a transmission circuit for a digital radio communication system according to a fourth embodiment of the present invention. In the present embodiment, a digital radio communication system including a base station having a transmission circuit for a digital radio communication system according to claim 3 and a plurality of subscriber stations under the control of the base station is assumed. 1 shows a transmission circuit for a digital radio communication system applied to a subscriber station of the digital radio communication system.

The transmission circuit for a digital radio communication system according to this embodiment differs from the transmission circuit for a digital radio communication system according to the second embodiment shown in FIG. Performing received signal demodulation circuit 4
13 and the transmission permission period calculation circuit 40
5 indicates that the period measured by the timer circuit 411 is equal to or longer than a predetermined period, and that the input output signal of the reception signal demodulation circuit 413 has confirmed that the base station has received the permission signal output from the base station. The transmission permission period is calculated based on the interference signal reception level obtained by the interference signal level detection circuit 403, and the transmission from the signal transmission circuit 406 is enabled during the transmission permission period. The other configuration is the same. .

In the above configuration, the reception signal s401 is received by the antenna circuit 401, and the output signal s402 of the antenna circuit 401 is input to the interference signal level detection circuit 403 as the output signal s403 of the switch circuit 402 via the switch circuit 402. . Interference signal level detection circuit 4
In 03, the signal level of the interference wave is detected, and the level detection signal s404 indicating the level of the interference signal is output to the transmission permission period calculation means 405.

On the other hand, the output signal s4 of the switch circuit 402
03 is also input to the reception signal demodulation circuit 413. When the permission signal output from the base station is demodulated by the reception signal demodulation circuit 413, an arrival confirmation signal S417 indicating that the permission signal has been received from the reception signal demodulation circuit 413 is input to the transmission permission period calculation 405. .

In the transmission permission period calculation circuit 405, when the time measured by the timer circuit 411 is maintained for the set time or more, the level detection signal s404 of the input interference signal is obtained.
The transmission permission period is calculated from the reception level of. here,
The transmission permission period calculation circuit 405 confirms the arrival confirmation signal s417 indicating the arrival of the permission signal from the base station, and
When the transmission permission period has been secured, a transmission control signal s 406 for controlling transmission in the calculated transmission permission period is output to the signal transmission circuit 406.

On the other hand, the reception signal level detection circuit 409 detects the level of the reception signal, and outputs a level detection signal s 411 indicating the level of the reception signal to the reception signal level determination circuit 410. Received signal level determination circuit 410
Then, when the level detection signal s411 exceeds the set threshold value, the level determination signal s412 is set to the timer circuit 411.
Output to The level determination signal s412 is input to the timer circuit 411, and the timer circuit 411 resets the measurement period when a reception signal of the own system is received.

Further, even after the transmission signal s407 is output from the signal transmission circuit 406 to the timer circuit 411, the reset signal s413 is input from the signal transmission circuit 406 and the measurement period is reset. Signal transmission circuit 4
In 06, the transmission signal s407 is transmitted in the transmission permission period permitted by the control signal s406 input from the transmission permission period calculation circuit 405. An output signal s408 of the signal transmission circuit 406 is transmitted from the antenna circuit 401 via the switch circuit 402.

In the transmitting circuit for the digital radio communication system according to the fourth embodiment of the present invention, the frame synchronization control between the stations is not required, but the interference wave detection period is set at substantially the same time between the own systems. With such an operation, the effect of suppressing the resetting of the timer circuit by a received signal from another station of the own system can be expected, so that the radar carrier sense circuit should operate continuously even during the transmission permission period. . Here, a significant feature of the transmission circuit for a digital wireless communication system according to the fourth embodiment of the present invention is as follows.
As shown in FIG. 8, the transmission permission period is set on the condition that the measurement period length Tr has been secured and that the permission signal has been received.

FIG. 8 shows a case where the transmission circuit for a digital radio communication system according to the fourth embodiment is applied to the subscriber A station and the subscriber B station. Therefore, as shown in the example of the subscriber station B in FIG. 8, even if the measurement period Tr in which there is no interference wave is secured, if the arrival of the permission signal is not confirmed, the transmission permission period is not set.

The transmission circuit for a digital radio communication system according to the fourth embodiment is effective when the transmission circuit for a digital radio communication system according to the third embodiment is applied to a subscriber station in a cell using a base station. Is big. This is a base station that can measure the transmission status of all subscriber stations,
By making the transmission permission period of the subscriber station dependent, it is possible to solve the problem that the transmission signal from the hidden terminal in the cell makes it difficult to secure the carrier sense period in the base station.

Further, assuming a cluster configuration composed of a plurality of cells centered on a centralized base station including a wireless relay between base stations, it is assumed that the centralized base station has a digital radio communication system according to the third embodiment. By using the transmitting circuit and the transmitting circuit for the digital radio communication system according to the fourth embodiment for the peripheral base station and the subscriber station, each station in the cluster does not perform frame synchronization, and the hidden terminal in the cluster is not used. Problems can be avoided. The reception signal demodulation circuit 413 and the transmission permission period calculation means 405 correspond to the demodulation means and the transmission permission period calculation means of the present invention, respectively.

Further, in each embodiment, a circuit based on various characteristics of the interference wave can be considered as the interference wave level detection circuit for detecting the reception level of the interference wave. For example, when the interference wave is a radar pulse wave, a method in which the interference level detection circuit performs measurement using an evaluation criterion such as a crest factor, which is a ratio of a reception peak power of the interference wave to a reception average power, may be considered. Further, a method using a filter or the like in accordance with the band of the interference wave is also conceivable.

Transmission and reception of the own system is performed by time division multiple access (TD
MA: Time Division Multiple Acccce) or carrier sense based on the received signal level to judge whether the frequency to be used is not used by another station, and if another station is not transmitting, transmit. CSMA / CA (Carrie
r Sense Multiple Access / Collision Avoidance). Also, it is naturally possible to use another access method.

[0061]

As described above, according to the present invention, when performing communication while coexisting with another system different from the own system at the same frequency, it is possible to reliably detect the interference wave reception level value. Thus, it is possible to realize a transmission circuit for digital wireless communication capable of avoiding interference with other systems.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a transmission circuit for digital wireless communication according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a transmission circuit for digital wireless communication according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a transmission circuit for digital wireless communication according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a transmission circuit for digital wireless communication according to a fourth embodiment of the present invention.

FIG. 5 is a timing chart for explaining processing up to the stoppage of the transmission circuit for digital wireless communication according to the embodiment of the present invention when the transmission permission period before the stoppage is calculated.

FIG. 6 is a timing chart showing an operation state of the transmission circuit for digital wireless communication according to the first embodiment of the present invention.

FIG. 7 is a timing chart showing an operation state in the transmission circuit for digital wireless communication according to the second embodiment of the present invention.

FIG. 8 is a timing chart showing an operation state in the transmission circuit for digital wireless communication according to the third and fourth embodiments of the present invention.

FIG. 9 is a block diagram showing a configuration example of a transmission circuit for digital communication related to the present invention.

[Explanation of symbols]

101, 201, 301, 401 Antenna circuit 102, 202, 302, 402 Switch circuit 103, 203, 303, 403 Interference signal level detection circuit 105, 205, 305, 405 Transmission permission period calculation circuit 106, 206, 306, 406 Signal Transmission circuit 107 Frame setting circuit 209, 309, 409 Received signal level detection circuit 210, 310, 410 Received signal level determination circuit 211, 311, 411 Timer circuit 312 Permit signal generation circuit 413 Received signal demodulation circuit

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Morikura 2-3-1 Otemachi, Hoshida-ku, Tokyo Nippon Telegraph and Telephone Corporation F-term (reference) 5K011 BA01 DA21 DA28 FA07 JA02 KA01 KA05 5K032 AA07 CA08 CA10 CC01 CC13 DA02 DA21 DB18 DB28 EA02 5K033 AA07 CA08 CB01 CB15 DA02 DA17 DB11 DB20 EA02

Claims (4)

[Claims] 1. An interference signal level detection means for receiving a reception signal and detecting a reception level of an interference signal from another system; an output signal of the interference signal level detection means being input; A transmission permission period calculation unit for calculating a transmission permission period for permitting transmission based on the obtained interference signal reception level; a transmission signal and an output signal of the transmission permission period calculation unit; A signal transmission means capable of transmitting the transmission signal during a period permitted by the signal, the transmission circuit for a digital wireless communication system comprising: a frame synchronization signal between own system stations; A frame setting unit for periodically setting an interference wave detection period frame-synchronized between the stations; Is input the output signal of the beam setting unit, a digital radio communication system for transmission circuit and controlling the signal transmission means to perform a transmission other than the interference wave detection period. 2. An interference signal level detection means for receiving a reception signal and detecting a reception level of an interference signal from another system, and an output signal of the interference signal level detection means, A transmission permission period calculation unit for calculating a transmission permission period for permitting transmission based on the obtained interference signal reception level; a transmission signal and an output signal of the transmission permission period calculation unit; A signal transmission means capable of transmitting the transmission signal during a period permitted by the signal, comprising: a transmission circuit for a digital radio communication system, the signal transmission means being reset when the signal transmission means ends transmission and measuring a predetermined period. Timer means for starting reception, a reception signal level detection means for receiving a reception signal and detecting a signal reception level of the own system, Receiving signal level determining means for receiving an output signal of the level detecting means and determining whether or not the input signal exceeds a set threshold value, wherein the timer means includes an output signal of the receiving signal level determining means. Is input, and resets the period measured when it is determined that the reception signal of the own system has arrived.The transmission permission period calculation unit receives the output signal of the timer unit, and measures the time measured by the timer unit. A transmission circuit for a digital radio communication system, wherein when the period is equal to or longer than the predetermined period, the transmission permission period is calculated based on the interference signal reception level obtained by the interference signal level detection means. 3. A signal for informing a subscriber station in the own cell of a start of a transmission permission period based on a control signal output from the transmission permission period calculation means and indicating a start of a transmission permission period. A permission signal generating means for outputting to the transmitting means, wherein the transmission permission period calculating means, when the time period measured by the timer means is equal to or longer than the predetermined period, the interference obtained by the interference signal level detecting means. The transmission permission period is calculated based on the signal reception level, a signal indicating the transmission permission period is output to the signal transmission unit, and the control signal for instructing the start of the transmission permission period at the start of the transmission permission period is set to the permission level. Output to the signal generation means, and the signal transmission means outputs the transmission permission period based on a control signal output from the transmission permission period calculation means and indicating the start of the transmission permission period. First digital radio communication system for the transmission circuit according to claim 2, characterized by transmitting the output signal of the permission signal generation means. 4. A subscriber station of a digital radio communication system comprising a base station having the transmission circuit for a digital radio communication system according to claim 3 and a plurality of subscriber stations under the jurisdiction of said base station. The subscriber station receives a received signal, receives interference signal level detection means for detecting a reception level of an interference signal from another system, receives an output signal of the interference signal level detection means, and receives the interference signal level. A transmission permission period calculation unit for calculating a transmission permission period for permitting transmission based on the interference signal reception level obtained by the detection unit; a transmission signal and an output signal of the transmission permission period calculation unit being input; A signal transmission unit capable of transmitting the transmission signal in a period permitted by an output signal of the unit; and a predetermined period reset when the signal transmission unit ends transmission. Timer means for starting measurement of the received signal, a received signal level detecting means for receiving a received signal and detecting a signal received level of the own system, and an output signal of the received signal level detecting means is inputted, and the input signal is set. Receiving signal level determining means for determining whether the received signal level has exceeded a threshold value, and demodulating means for receiving and demodulating a received signal.The timer means receives an output signal of the received signal level determining means, When it is determined that the received signal of the own system has arrived, reset the time measured, the transmission permission period calculating means, the period measured by the timer means is longer than the predetermined period, and the input said If the output signal of the demodulation means indicates that the reception of the permission signal has been confirmed, the transmission is performed based on the interference signal reception level obtained by the interference signal level detection means. Calculates a variable period, the subscriber station of a digital radio communication system characterized by having a transmitter circuit for a digital radio communication system that facilitates transmission from said signal transmitting means at the transmission grant period.