JP7731258B2 - Wireless communication device and wireless communication system - Google Patents

Description

The present invention relates to a wireless communication device that complies with, for example, the standard for radio equipment for specified low-power radio stations and radio telephones, and a wireless communication system that includes the wireless communication device.

In recent years, as we have been hit by disasters such as earthquakes and typhoons, some local governments have introduced disaster prevention radio systems or disaster prevention administrative radio systems (hereinafter referred to as disaster prevention radio systems) and have installed dedicated receivers in every household. However, while disaster prevention radio systems must "reach residents without fail," they require dedicated frequency allocations from the Ministry of Internal Affairs and Communications to prevent interference, and require complex line design, making them difficult, time-consuming, and costly to implement, making them difficult to implement.

For example, by operating a disaster prevention radio system using specific low-power radio equipment, it can be operated in a limited area, but there is no need to apply to government agencies and the actual equipment can be prepared relatively inexpensively, lowering the hurdle to introducing the system.

Patent No. 4828396

Association of Radio Industries and Businesses, "Standard for Radio Equipment for Specified Low-Power Radio Stations and Radio Telephones," RCR-STD-20, Version 5.0, revised September 28, 2020

However, there were the following challenges:

National technical standards are established to ensure efficient use of frequencies and avoid interference with other users. In addition, the "Standards for Radio Equipment for Specified Low-Power Radio Stations and Radio Telephones" are established in Non-Patent Document 1 to ensure the appropriate quality and compatibility of radio equipment, thereby providing convenience to radio equipment manufacturers and users. These specified low-power radio stations are widely used nationwide because they do not require a radio station license. However, the standard stipulates that when configuring a wireless communication device with an antenna power of, for example, 10mW, "it must have the function of automatically limiting communication time to three minutes, and in that case, not to communicate again until two seconds have elapsed."

Furthermore, on page 13 of Non-Patent Document 1, the following definition is given regarding "carrier sense" (former Ministry of Posts and Telecommunications Notification No. 49 of 1989). Hereinafter, this will be referred to as the "carrier sense provisions."

"(3) Carrier sense: Radio equipment shall be equipped with carrier sense. Carrier sense means that, when radio waves from another radio station are received prior to the establishment of a radio communication line, the radio equipment shall not emit radio waves of the same frequency as the radio waves emitted by that radio station (in the case of duplex and semi-duplex systems, the transmission frequency corresponding to the receiving frequency)."

Figure 11 is a timing chart showing an example of operation to explain the issues in a conventional wireless communication system. This wireless communication system is configured with a wireless transmitter and a wireless receiver.

In Figure 11, the wireless transmitter transmits an audio signal intermittently and repeatedly over a predetermined time limit of three minutes, and performs carrier sense (CS) before each wireless transmission. In response, the wireless receiver receives and demodulates the wireless signal from the wireless transmitter to output an audio signal. As a result, the wireless receiver receives the audio signal intermittently over the air, causing the audio signal to be interrupted.

In other words, as mentioned above, when transmitting with an antenna power of 10 mW in a specified low-power radio system, there is a transmission time limit of 3 minutes, making it impossible to implement in disaster prevention radio systems, which require continuous radio transmission of audio signals for long periods of time without interruption.

The object of the present invention is to solve the above problems and to provide a wireless communication device that, when applied to, for example, a specified low-power wireless system, does not interrupt the audio signal even if the audio signal transmission time exceeds a predetermined time limit, such as three minutes, and a wireless communication system equipped with such a wireless communication device.

A wireless communication device according to a first aspect of the present invention comprises:
a first wireless receiving unit that wirelessly receives a wireless signal modulated in accordance with an audio signal on a first channel and demodulates the wireless signal into a first audio signal;
a second wireless receiving unit that wirelessly receives, via a second channel, a wireless signal modulated in accordance with the audio signal and demodulates the wireless signal into a second audio signal;
an audio output unit that selectively switches between and outputs the first audio signal and the second audio signal in conjunction with the start of wireless reception by the first and second wireless receiving units, or adds and outputs the first audio signal and the second audio signal;
a first control unit that controls the first and second wireless receiving units,
The first control unit controls the audio output unit to switch to and output the second audio signal when the second wireless receiving unit receives a radio signal while the first wireless receiving unit is receiving a radio signal.

A wireless communication device according to a second aspect of the present invention comprises:
a first wireless transmitting unit that wirelessly transmits a wireless signal modulated in accordance with an audio signal over a first channel within a predetermined first time limit and intermittently;
a second wireless transmission unit that is a wireless transmission unit separate from the first wireless transmission unit, and that wirelessly transmits a wireless signal modulated in accordance with the audio signal on a second channel within a predetermined second time limit and intermittently;
and a second control unit that controls the first and second wireless transmission units, wherein the second control unit starts wireless transmission of the second wireless transmission unit before the wireless transmission of the first wireless transmission unit ends due to the first time limit, thereby controlling the wireless transmission of the wireless signal modulated according to the audio signal by the first wireless transmission unit and the wireless transmission of the wireless signal modulated according to the audio signal by the second wireless transmission unit to be performed simultaneously for a predetermined time.

A wireless communication system according to a third aspect of the present invention comprises:
a wireless communication device according to the first aspect of the present invention;
The wireless communication device according to the second aspect of the present invention.

Therefore, the wireless communication device etc. according to the present invention can provide a wireless communication device that can be applied, for example, to a specified low-power wireless system, for example, to a disaster prevention wireless system, and a wireless communication system equipped with the wireless communication device. In particular, when a wireless communication device for a specified low-power wireless system is applied, for example, to a disaster prevention wireless system, the audio signal will not be interrupted even if the audio signal transmission time exceeds a predetermined time limit, such as three minutes.

1 is a block diagram showing an example of the configuration of a wireless transceiver device for a wireless communication system according to a first embodiment; 2 is a block diagram showing an example of the configuration of a wireless receiving device that receives a wireless signal from the wireless transmitting/receiving device of FIG. 1 . 2 is a flowchart showing a first part of a transmission/reception control process executed by the wireless transmission/reception device of FIG. 1 . 10 is a flowchart showing a second part of the transmission/reception control process executed by the wireless transmission/reception device of FIG. 3 is a flowchart showing a first part of a reception control process executed by the wireless receiving device of FIG. 2 . 10 is a flowchart showing a second part of the reception control process executed by the wireless receiving device of FIG. 2 . 3 is a timing chart showing an example of operation of a wireless communication system including the wireless transmitting/receiving device of FIG. 1 and the wireless receiving device of FIG. 2 . 10 is a flowchart showing a first part of a transmission/reception control process executed by a wireless transmission/reception device for a wireless communication system according to a second embodiment. 10 is a flowchart illustrating a second part of the transmission/reception control process executed by the wireless transmission/reception device according to the second embodiment. 10 is a flowchart illustrating a first part of a reception control process executed by a wireless receiving device according to a second embodiment. 10 is a flowchart illustrating a second part of the reception control process executed by the wireless receiving device according to the second embodiment. FIG. 10 is a block diagram illustrating an example of the configuration of a wireless receiving device for a wireless communication system according to a third embodiment. 11 is a flowchart showing a first part of a transmission/reception control process of a wireless transmission/reception device used in a wireless communication system according to a third embodiment. 11 is a flowchart showing a second part of the transmission/reception control process of the wireless transmission/reception device used in the wireless communication system according to the third embodiment. 9 is a flowchart showing a first part of a reception control process executed by the wireless receiving device of FIG. 8 . 10 is a flowchart showing a second part of the reception control process executed by the wireless receiving device of FIG. 8 . 10 is a timing chart showing an example of operation for explaining a problem in a wireless communication system according to a conventional example.

Embodiments of the present invention will be described below with reference to the drawings. Note that identical or similar components are designated by the same reference numerals.

(Embodiment 1)
Fig. 1 is a block diagram showing an example of the configuration of a wireless transmitting/receiving device for a wireless communication system according to embodiment 1. Fig. 2 is a block diagram showing an example of the configuration of a wireless receiving device that receives a wireless signal from the wireless transmitting/receiving device of Fig. 1. The wireless communication system is, for example, a disaster prevention wireless system, and is configured to include the wireless transmitting/receiving device of Fig. 1 and the wireless receiving device of Fig. 2 that are connected to each other by a wireless line, and each device is a wireless communication device that complies with the standard for radio equipment for specified low-power radio stations and radio telephones, with an antenna transmission power of, for example, 10 mW or less.

In FIG. 1, the wireless transmitter/receiver device comprises antennas 1-3, modulation/transmission units 11 and 12, a reception/demodulation unit 13, an operation unit 14 having a PTT (Push To Talk) key 14p, a microphone 15, an audio signal input unit 16, an audio signal amplifier 17, an audio signal level measurement unit 18, a received wireless signal level measurement unit 19, and a control unit 10 that controls these processing units. Here, antennas 1-3 may comprise, for example, at least one or two antennas, and may be configured to share a bandpass filter or a circulator. The audio signal input unit 16 and audio signal level measurement unit 18 are processing units used in a modified version of embodiment 1, which will be described in detail below.

In FIG. 1, the receiver/demodulator 13 receives a radio signal received by the antenna 3 to perform carrier sensing (CS) on a specified channel among multiple channels, and performs low-noise amplification, low-band frequency conversion, intermediate amplification, etc., before outputting the processed signal to the received radio signal level measurement unit 19. The receiving channel of the receiver/demodulator 13 is controlled by the control unit 10. The received radio signal level measurement unit 19 compares the input signal with a specified threshold value to determine whether a radio signal is being received for carrier sensing (CS) on a specified channel among multiple channels, and outputs a determination result signal to the control unit 10.

Operation unit 14 has PTT key 14p, a transmission key for issuing transmission instructions, and when PTT key 14p is turned on, outputs a control signal indicating this to control unit 10. Audio input to microphone 15 is converted into an audio signal, which is then amplified by audio signal amplifier 17 and output to modulation transmitters 11 and 12. Modulation transmitters 11 and 12 each modulate a carrier signal of a predetermined channel from among multiple channels in accordance with the input audio signal to generate a modulated radio signal, which is then power-amplified and radiated from antennas 1 and 2. The transmission channels of modulation transmitters 11 and 12 are controlled by control unit 10.

Modulation transmission units 11 and 12 comply with the radio equipment standard for specified low-power radio stations with an antenna transmission power of, for example, 10 mW or less. After performing carrier sense (CS) to confirm that no radio signals from other radio communication devices are received on the transmitting channel, they intermittently transmit radio signals using that channel for a limited time (a maximum transmission time, for example, 3 minutes (or 5 minutes). Transmission may be within the time limit. The transmission time limits for modulation transmission units 11 and 12 may be the same or different). After modulation transmission unit 11 transmits, when modulation transmission unit 12 next transmits, wireless transmission begins on a channel different from that of modulation transmission unit 11, starting, for example, 5 seconds (a predetermined time that is sufficiently shorter than the 3-minute limit) before the 3-minute transmission time (time limit) of modulation transmission unit 11 has elapsed (thus, carrier sense (CS) is performed from the previous time).

The control unit 10 includes three-minute timers T1 and T2, which are set to a timeout (transmission time limit) of, for example, three minutes when reset, and then subtract the timeout held at the start of timing. Based on control signals from the processing units 14, 18, and 19, the control unit 10 uses the three-minute timers T1 and T2 to execute the transmission and reception control process shown in Figures 3A and 3B (described below), thereby controlling the operation of the processing units 11 to 18.

In FIG. 2, the wireless receiving device is configured with antennas 4 and 5, reception demodulation units 21 and 22, an audio signal switching unit 23, an audio signal amplifier 24, and a speaker 25. Here, antennas 4 and 5 may be configured as a single shared antenna.

In FIG. 2, reception demodulation units 21 and 22 each receive radio signals received by antennas 4 and 5 on a predetermined channel from among multiple channels, and after performing processing such as low-noise amplification, low-band frequency conversion, and intermediate frequency amplification, demodulate the processed signal into an audio signal and output it to audio signal switching unit 23. Note that each reception channel of reception demodulation units 21 and 22 is controlled by control unit 20. Audio signal switching unit 23 selectively switches one of two input audio signals and outputs it to audio signal amplifier 24. Audio signal amplifier 24 amplifies the input audio signal and outputs it to speaker 25, where it is output as audio. Control unit 20 controls the operation of each processing unit 21 to 23 by executing the reception control processing shown in FIGS. 4A and 4B, which will be described later.

The receiver/demodulator 22 in Figure 2 starts wireless reception on another channel 2 at a time (times t2 and t4 in Figure 5) that is, for example, 5 seconds before the time when 3 minutes have elapsed since the time of wireless reception by the receiver/demodulator 21 (times t1, t3, and t5 in Figure 5), and the audio signal switching unit 23 switches the output from the audio signal on channel 1 to the audio signal on channel 2 at time t2, thereby allowing the two receiver/demodulators 21 and 22 to output audio signals without interruption for more than 3 minutes.

Figures 3A and 3B are flowcharts showing the transmission and reception control process executed by the wireless transmission and reception device of Figure 1.

In step S1 of FIG. 3A, the PTT 14p is awaited to be turned on (or, in a variant described below, the audio signal is awaited from the audio signal input unit 16). The receiver/demodulator 13 enters a reception standby state on channel 1 for carrier sense (CS), and the three-minute timers T1 and T2 are reset to 0 seconds. Next, in step S2, it is determined whether the three-minute timer T1 has reached 0 seconds. If the determination is YES, the process proceeds to step S3; if the determination is NO, the process proceeds to step S4. In step S3, the modulation/transmission unit 11 stops wireless transmission and proceeds to step S4. In step S4, it is determined whether the PTT key 14p is on or there is audio input. If the determination is YES, the process proceeds to step S6; if the determination is NO, the process proceeds to step S5. In step S5, the modulation/transmission units 11 and 12 stop wireless transmission and then return to step S2.

In step S6, it is determined whether the time count of the three-minute timer T2 is five seconds or less; if the answer is YES, the process proceeds to step S7; if the answer is NO, the process returns to step S2. In step S7, the receiver/demodulator 13 performs carrier sensing (CS) to determine whether there is an input, for example, on channel 1; if the answer is YES, the process returns to step S2; if the answer is NO, the process proceeds to step S8. In step S8, the modulator/transmitter 11 begins wireless transmission on channel 1, and the receiver/demodulator 13 waits for wireless reception on channel 2 for carrier sensing (CS). In step S9, the three-minute timer T1 starts timing, and the process proceeds to step S11 in Figure 3B.

In step S11 of Figure 3B, it is determined whether the time count of the 3-minute timer T2 is 0 seconds; if YES, the process proceeds to step S12; if NO, the process proceeds to step S13. In step S12, the modulation transmission unit 12 stops wireless transmission and proceeds to step S13. In step S13, it is determined whether the PTT key 14p is on or whether there is voice input; if YES, the process proceeds to step S15; if NO, the process proceeds to step S14. In step S14, the modulation transmission units 11 and 12 stop wireless transmission, and then the process returns to step S2 of Figure 3A.

In step S15, it is determined whether the time count of the three-minute timer T1 is five seconds or less; if YES, the process proceeds to step S16; if NO, the process returns to step S11. In step S16, the receiver/demodulator 13 performs carrier sensing (CS) to determine whether there is an input, for example, on channel 2; if YES, the process returns to step S11; if NO, the process proceeds to step S17. In step S17, the modulator/transmitter 12 begins wireless transmission on channel 2, and the receiver/demodulator 13 waits for wireless reception on channel 1 for carrier sensing (CS). In step S18, the three-minute timer T2 begins timing, and the process returns to step S2 in FIG. 3A.

Figures 4A and 4B are flowcharts showing the reception control process executed by the wireless receiving device of Figure 2.

In step S21 of FIG. 4A, the receiver/demodulator 21 waits for incoming radio reception, for example, on channel 1, and the receiver/demodulator 22 waits for incoming radio reception, for example, on channel 2. Next, in step S22, the receiver/demodulator 21 determines whether or not there is incoming radio signal; if YES, the process proceeds to step S23; if NO, the process returns to step S22. In step S23, the audio signal switching unit 23 switches to select output of the audio signal from the receiver/demodulator 21, and begins outputting the received audio signal in step S24.

In step S25, the receiving and demodulating unit 21 determines whether a wireless signal is being received. If the answer is YES, the process proceeds to step S27; if the answer is NO, the process proceeds to step S26. In step S26, the output of the received audio signal is stopped, and the process returns to step S22. In step S27, the receiving and demodulating unit 22 determines whether a wireless signal is being received. If the answer is YES, the process returns to step S25; if the answer is NO, the process proceeds to step S28. Also, in step S28, the receiving and demodulating unit 21 determines whether a wireless signal is being received. If the answer is YES, the process proceeds to step S30; if the answer is NO, the process proceeds to step S29. In step S29, the output of the received audio signal is stopped, and the process returns to step S22. In step S30, the receiving and demodulating unit 22 determines whether a wireless signal is being received. If the answer is YES, the process proceeds to step S31 of FIG. 4B; if the answer is NO, the process returns to step S28.

In step S31 of Figure 4B, the audio signal switching unit 23 switches to select the output of an audio signal from the reception and demodulation unit 22, and in step S32, it is determined whether or not a radio signal is being received by the reception and demodulation unit 22. If the answer is YES, the process proceeds to step S34, and if the answer is NO, the process proceeds to step S33. In step S33, the output of the received audio signal is stopped, and the process returns to step S22 of Figure 4A. In step S34, it is determined whether or not a radio signal is being received by the reception and demodulation unit 21. If the answer is YES, the process returns to step S32, and if the answer is NO, the process proceeds to step S35. Also, in step S35, it is determined whether or not a radio signal is being received by the reception and demodulation unit 22. If the answer is YES, the process proceeds to step S37, and if the answer is NO, the process proceeds to step S36. In step S36, the output of the received audio signal is stopped, and the process returns to step S22 of Figure 4A. In step S37, the reception/demodulation unit 21 determines whether a wireless signal is being received; if YES, the process proceeds to step S38; if NO, the process returns to step S35. In step S38, the audio signal switching unit 23 switches to select the output of an audio signal from the reception/demodulation unit 21, and the process returns to step S25.

Figure 5 is a timing chart showing an example of the operation of a wireless communication system equipped with the wireless transmitter/receiver of Figure 1 and the wireless receiver of Figure 2. The wireless communication system is composed of a wireless transmitter/receiver equipped with modulation/transmission units 11 and 12 and a receiver/demodulator unit 13, and a wireless receiver equipped with receiver/demodulator units 21 and 22.

In Figure 5, before the transmission time (t1) of the modulation transmission unit 11, the reception/demodulation unit 13 performs carrier sense (CS) to confirm that channel 1 is free, and the modulation transmission unit 11 begins transmitting a radio signal on channel 1 at time t1. Next, at time t2, for example, 2 minutes and 55 seconds after the expiration of the 3-minute limit after the transmission of the modulation transmission unit 11, the modulation transmission unit 12 begins transmitting a radio signal on channel 2. However, carrier sense (CS) for channel 2 is performed before time t2. Then, at time t11, when the 3-minute limit has expired, the modulation transmission unit 11 stops transmitting.

Next, similarly, at time t3, for example, 2 minutes and 55 seconds after the three-minute limit has expired since the modulation transmission unit 12 began wireless transmission, the modulation transmission unit 11 begins transmitting wireless signals on channel 1. However, carrier sense (CS) for channel 1 is performed before time t3. Thereafter, at time t21, when the three-minute wireless transmission has expired, the modulation transmission unit 12 stops wireless transmission. This process can be repeated thereafter, allowing the wireless transmission/reception device of Figure 1 to continue transmitting the same series of audio signals.

In contrast, the wireless receiving device is configured with receiving and demodulating units 21 and 22 and an audio signal switching unit 23, and the wireless receiving device can be, for example, a small wireless receiver for a disaster prevention radio system, or the speaker 25 can be a large disaster prevention radio speaker for broadcasting.

In FIG. 5, when the receiving and demodulating unit 21 receives a radio signal on channel 1 at time t1, the audio signal received on channel 1 is output from the speaker 25. Thereafter, when the receiving and demodulating unit 22 receives a radio signal on channel 2, the audio signal switching unit 23 switches to the audio signal received on channel 2 and outputs it from the speaker 25. Next, when the receiving and demodulating unit 21 receives a radio signal on channel 1 again, the audio signal switching unit 23 switches to the audio signal received on channel 1 and outputs it from the speaker 25. By repeating this operation, it is possible to continue receiving radio signals on two channels and output a series of audio signals from the speaker 25 without interruption.

As described above, the control unit 10 of the wireless transceiver device controls the modulation transmission unit 12 to start wireless transmission before the wireless transmission by the modulation transmission unit 11 ends. The control unit 10 also controls the modulation transmission unit 11 to start wireless transmission before the wireless transmission by the modulation transmission unit 12 ends. Furthermore, the control unit 20 of the wireless receiver device controls the audio signal switching unit 23 to switch to and output the audio signal from the reception demodulation unit 22 if the reception demodulation unit 22 receives wireless signals during wireless reception by the reception demodulation unit 21. The control unit 20 also controls the audio signal switching unit 23 to switch to and output the audio signal from the reception demodulation unit 21 if the reception demodulation unit 21 receives wireless signals during wireless reception by the reception demodulation unit 22.

By combining the wireless transmitter/receiver device of Figure 1 described above with the wireless receiver device of Figure 2, the transmitting wireless transmitter/receiver device continues to transmit the same series of audio signals, and the receiving wireless receiver device receives either channel 1 or 2 in overlapping fashion, allowing for uninterrupted wireless transmission of audio signals regardless of a time limit of, for example, three minutes.

In Figure 5, at time t3, the modulation transmission unit 11 is transmitting wirelessly on channel 1, but if no other wireless signals are detected by carrier sense (CS), it may transmit wirelessly on another channel, for example, channel 3. Also, at time t4, the modulation transmission unit 12 is transmitting wirelessly on channel 2, but if no other wireless signals are detected by carrier sense (CS), it may transmit wirelessly on another channel, for example, channel 4.

(Modification of the first embodiment)
A modification of the first embodiment is characterized in that the wireless transmitting/receiving device of Fig. 1 is applied to a broadcast transmission facility of a disaster prevention radio system, and the wireless receiving device of Fig. 2 is applied to a broadcast reception facility of the disaster prevention radio system. Here, the speaker 25 of Fig. 2 is configured as a large broadcast speaker.

In Figure 1, the audio signal level measurement unit 18 compares the audio signal of the disaster prevention radio broadcast audio input from the audio signal input unit 16 with a predetermined threshold value to determine whether the audio signal has been input. If the answer is YES, the process proceeds to S6 in the case of step S4 in Figure 3A, or to S15 in the case of step S13 in Figure 3B.

In other words, outdoor disaster prevention speakers installed by local governments and other organizations broadcast emergency broadcasts during disasters, but residents often cannot hear the sound from the speakers and are unable to understand the content because they have closed windows or the sound of wind and rain makes it difficult to hear. By replacing the transmission start condition (step S4 in FIG. 3A, step S13 in FIG. 3B) of the wireless transceiver device of FIG. 1 in embodiment 1 with the PTT key 14p on the operation unit and transmitting wirelessly when an audio signal is input from the audio signal input unit 16 and an audio input exceeding a certain threshold level occurs, wireless transmission can be initiated by the audio signal from the disaster prevention speaker, and audio from the speaker 25 in FIG. 2 can be transmitted uninterrupted regardless of the three-minute time limit.

By using the wireless receiving device of Figure 2 to receive the wireless signal transmitted from the wireless transmitting/receiving device of Figure 1, it is possible to receive the sound from the disaster prevention speaker without interruption, regardless of whether the window is open or closed, or whether it is exposed to wind or rain, and regardless of the three-minute time limit.

(Embodiment 2)
6A and 6B are flowcharts showing transmission and reception control processing executed by a wireless transmission/reception device for a wireless communication system according to embodiment 2. Also, Fig. 7A and 7B are flowcharts showing reception control processing executed by a wireless reception device according to embodiment 2. Here, the wireless communication system according to embodiment 2 has the same configuration as the wireless transmission/reception device in Fig. 1 and the wireless reception device in Fig. 2, but has the following operational differences.

(1) Step S1 in Fig. 3A is replaced with step S1A in Fig. 6A. In step S1A, the PTT 14p is awaited to be turned on (or, in a modified example, the audio signal is awaited from the audio signal input unit 16), the receiver/demodulator 13 enters a reception standby state on any channel for carrier sense (CS), and the three-minute timers T1 and T2 are reset to 0 seconds.
(2) The processing of step S10 in Fig. 6A is inserted between YES in step S7 and step S2 in Fig. 3A. In step S10, the receiver/demodulator 13 switches to a channel for wireless reception that is different from the channel on which the wireless signal was received in step S7.
(3) Step S8 in Fig. 3A is replaced with step S8A in Fig. 6A. In step S8A, the modulation/transmission unit 11 starts wireless transmission on the same channel as the reception/demodulation unit 13, which did not receive a wireless signal in step S7.
(4) The process of step S19 in Fig. 6B is inserted between YES in step S16 in Fig. 3B and step S11. In step S19, the receiver/demodulator 13 switches to a radio receiving channel different from the channel on which the radio signal was received in step S16.
(5) Step S17 in Fig. 3B is replaced with step S17A in Fig. 6B. In step S17A, the modulation/transmission unit 12 starts wireless transmission on the same channel of the reception/demodulation unit 13 where no wireless signal was detected in step S16.

(6) Step S21 in Fig. 4A is replaced with step S21A in Fig. 7A. In step S21A, the receiver/demodulator 21 waits for incoming radio reception, for example, on a predetermined arbitrary channel, and the receiver/demodulator 22 waits for incoming radio reception, for example, on a channel different from the predetermined channel.
(7) The processing of step S22A in Fig. 7A is inserted between step S22 NO in Fig. 4A and step S22. In step S22A, if there is no signal in step S22, the receiving and demodulating unit 21 switches the channel and receives radio signals.
(8) The process of step S30A in Fig. 7A is inserted between NO in step S30 in Fig. 4A and step S28. In step S30A, if there is no signal in step S30, the receiving and demodulating unit 22 switches channels and performs wireless reception.
(9) The processing of step S37A in Fig. 7B is inserted between NO in step S37 in Fig. 4B and step S35. In step S37A, if there is no signal in step S37, the receiving and demodulating unit 21 switches channels and performs wireless reception.

The problems to be solved by the second embodiment configured as described above are as follows:

After the modulation transmission unit 11 of the wireless transceiver device of Figure 1 in embodiment 1 wirelessly transmits on channel 1, the modulation transmission unit 12 attempts to wirelessly transmit on channel 2 before the three-minute time limit expires. However, if carrier sense (CS) detects that channel 2 is in use, the carrier sense function activates, preventing the modulation transmission unit 12 from transmitting on channel 2, and the transmission of the same voice signal is interrupted.

Therefore, before the modulation transmission unit 12 starts transmitting, the reception/demodulation unit 13 is used to scan unused channels, switch to a channel that can be transmitted, and the modulation transmission unit 12 then transmits wirelessly. And/or, before the modulation transmission unit 11 starts transmitting, the reception/demodulation unit 13 is used to scan unused channels, switch to a channel that can be transmitted, and the modulation transmission unit 11 then transmits wirelessly. This prevents the wireless transmission of the same audio signal from being interrupted due to carrier sensing.

In addition, since the wireless receiving device according to embodiment 2 receives a wireless signal from the wireless transmitting/receiving device according to embodiment 2, the receiving/demodulating unit 22 scans channels and demodulates and outputs the audio signal received on the channel on which the audio signal is received. And/or the receiving/demodulating unit 21 scans channels and demodulates and outputs the audio signal received on the channel on which the audio signal is received. This makes it possible to receive and output the audio signal of the transmitted wireless signal from the wireless transmitting/receiving device according to embodiment 2 without interruption, regardless of a time limit of, for example, three minutes.

(Embodiment 3)
Fig. 8 is a block diagram showing an example of the configuration of a wireless receiving device for a wireless communication system according to embodiment 3. In Fig. 8, the wireless transmitting/receiving device and the wireless receiving device according to embodiment 3 have the following differences compared to the wireless transmitting/receiving device in Fig. 1 and the wireless receiving device in Fig. 2.
(1) The wireless transmitter/receiver shown in FIG. 1 is used, but the modulation transmitters 11 and 12 wirelessly transmit an end code when the time limit expires.
(2) In FIG. 8, instead of the audio signal switching unit 23, an audio signal adding unit 23A and received audio signal muting units 31 and 32 are provided.

In Figure 8, the audio signal addition unit 23A adds the audio signals from the reception demodulation units 21 and 22 and outputs the resulting audio signal to the audio signal amplification unit 24. The control unit 20 mutes (silences) the audio signal from the original reception demodulation unit 21 or 22 in response to an end code from the wireless transceiver at the next reception start time of the reception demodulation unit 22 or 21 (t2, t3, t4, t5 in Figure 5). Here, the end code is an example of an end signal indicating the expiration of a time limit of, for example, three minutes for the audio signal, and is, for example, a predetermined pattern of a digital binary signal.

Figures 9A and 9B are flowcharts showing the transmission and reception control processing of a wireless transmission/reception device used in a wireless communication system according to embodiment 3. Figures 10A and 10B are flowcharts showing the reception control processing of the wireless reception device of Figure 8. Figures 9A to 10B differ from Figures 3A to 4B in the following ways:

(1) The processing of step S3A in Fig. 9A is inserted between YES in step S2 and step S3 in Fig. 3A. In step 3A, the modulation transmission unit 11 transmits an end code at the end of, for example, a three-minute audio signal.
(2) The process of step S12A in Fig. 9B is inserted between YES in step S11 and step S12 in Fig. 3B. In step S12A, the modulation transmission unit 12 transmits an end code at the end of, for example, a three-minute audio signal.

(3) Step S23A in Fig. 10A is inserted in place of step S23 in Fig. 4A. In step S23A, the audio signal adding unit 23A outputs the audio signal from the receiving and demodulating unit 21.
(4) The processing of steps S27A and S27B in Fig. 10A has been inserted between YES in step S27 and step S25 in Fig. 4A. In step S27A, the reception demodulation unit 21 determines whether or not an end code has been received in the demodulated signal. If YES, the processing proceeds to step S27B, whereas if NO, the processing returns to step S25. In step S27B, the reception audio signal mute unit 31 mutes the input audio signal and outputs it.
(5) Step S31 in Fig. 4B is replaced with step S31A in Fig. 10B. In step S31A, the audio signal adding unit 23A outputs the audio signal from the receiving and demodulating unit 22.
(6) The processing of steps S34A and S34B in Fig. 10B has been inserted between YES in step S34 and step S32 in Fig. 4B. In step S34A, the reception demodulation unit 22 determines whether or not an end code has been received in the demodulated signal. If YES, the processing proceeds to step S34B, whereas if NO, the processing returns to step S32. In step S34B, the reception audio signal mute unit 32 mutes the input audio signal and outputs it.
(7) Step S38 in Fig. 4B is replaced with step S38A in Fig. 10B. In step S38A, the audio signal adding unit 23A outputs the audio signal from the receiving and demodulating unit 21.

In the third embodiment configured as described above, an end code is added at the end of transmission from the wireless transmitter/receiver device of FIG. 1, and the audio signal addition unit 23A of the wireless receiver device of FIG. 8 adds and outputs the audio signals from the reception demodulation units 21 and 22, while the received audio signal mute units 31 and 32 located upstream of this add and output the audio signals upon receiving the end code. This enables continuous wireless transmission without interruption of the audio signal beyond the three-minute time limit, just as in the first and second embodiments.

(Modification of the third embodiment)
Instead of the mute function according to the third embodiment, an AGC (automatic gain control) may be used to maintain the level of the output audio signal at a substantially constant level.

Furthermore, while the end code has been described as an example of an end signal indicating the expiration of a time limit of, for example, three minutes for an audio signal, it is also possible to compare the audio signal with a predetermined threshold value and determine that the audio signal has ended when a predetermined duration (for example, about five seconds) has continued, thereby stopping the output of the audio signal from the received wireless signal and further stopping the reception of the received wireless signal.

(Modification)
The first, second, and third embodiments and their modifications configured as described above may be configured in combination with one another.

Note that the transmission time limit of 3 minutes and the 5 seconds (predetermined time) before the expiration of the transmission time limit for the second or subsequent wireless transmissions are merely example values and can be changed based on design values or regulations, etc.

As described above in detail, the wireless communication device according to the present invention can provide a wireless communication device that can be applied to, for example, a specified low-power wireless system, such as a disaster prevention wireless system, and a wireless communication system equipped with the wireless communication device.

1 to 5 Antenna 10 Control unit 11, 12 Modulation transmission unit 13 Reception demodulation unit 14 Operation unit 14p PTT key 15 Microphone 16 Audio signal input unit 17 Audio signal amplifier unit 18 Audio signal level measurement unit 19 Received radio signal level measurement unit 21, 22 Reception demodulation unit 23 Audio signal switching unit 23A Audio signal addition unit 24 Audio signal amplifier unit 25 Speakers 31, 32 Received audio signal mute units T1, T2 3-minute timer

Claims (15)

a first wireless receiving unit that wirelessly receives a wireless signal modulated in accordance with an audio signal on a first channel and demodulates the wireless signal into a first audio signal;
a second wireless receiving unit that wirelessly receives, via a second channel, a wireless signal modulated in accordance with the audio signal and demodulates the wireless signal into a second audio signal;
an audio output unit that selectively switches between and outputs the first audio signal and the second audio signal in conjunction with the start of wireless reception by the first and second wireless receiving units, or adds and outputs the first audio signal and the second audio signal;
a first control unit that controls the first and second wireless receiving units,
A wireless communication device, wherein the first control unit controls the audio output unit to switch to and output the second audio signal when the second wireless receiving unit receives a wireless signal while the first wireless receiving unit is receiving a wireless signal. The wireless communication device of claim 1, wherein the first control unit controls the audio output unit to switch to and output the first audio signal when the first wireless receiving unit receives a wireless signal while the second wireless receiving unit is receiving a wireless signal. The wireless communication device according to claim 1 or 2, wherein the first control unit controls wireless reception by the first wireless receiving unit and wireless reception by the second wireless receiving unit to be alternately repeated. The wireless communication device of claim 3, wherein the first control unit, when controlling the first wireless receiving unit to alternately perform wireless reception and the second wireless receiving unit, controls the first wireless receiving unit to perform wireless reception on the first channel or the third channel after wireless reception by the second wireless receiving unit. A wireless communication device according to any one of claims 1 to 4, wherein the first control unit controls at least one of the first and second wireless receiving units to search for a wireless signal modulated according to an audio signal while scanning channels, and to wirelessly receive the wireless signal on the searched channel. The wireless communication device described in any one of claims 1 to 5, wherein the first control unit controls the first and second wireless receiving units to mute the audio signal output from the wireless receiving unit that received the end signal when the first and second wireless receiving units each receive the end signal. a first wireless communication device that is a wireless communication device according to any one of claims 1 to 6;
a second wireless communication device,
the second wireless communication device,
a first wireless transmission unit that transmits a wireless signal modulated in accordance with an audio signal over the first channel intermittently within a predetermined first time limit;
a second wireless transmission unit that is a wireless transmission unit separate from the first wireless transmission unit, and that wirelessly transmits a wireless signal modulated in accordance with the audio signal over the second channel within a predetermined second time limit and intermittently;
a second control unit that controls the first and second wireless transmission units,
The second control unit controls the wireless transmission of the wireless signal modulated according to the audio signal by the first wireless transmitting unit and the wireless transmission of the wireless signal modulated according to the audio signal by the second wireless transmitting unit to be performed simultaneously for a predetermined time by starting the wireless transmission of the second wireless transmitting unit before the wireless transmission of the first wireless transmitting unit is terminated by the first time limit. a first wireless communication device that is the wireless communication device according to claim 2;
a second wireless communication device,
the second wireless communication device,
a first wireless transmission unit that transmits a wireless signal modulated in accordance with an audio signal over the first channel intermittently within a predetermined first time limit;
a second wireless transmission unit that is a wireless transmission unit separate from the first wireless transmission unit, and that wirelessly transmits a wireless signal modulated in accordance with the audio signal over the second channel within a predetermined second time limit and intermittently;
a second control unit that controls the first and second wireless transmission units,
the second control unit starts wireless transmission of the second wireless transmission unit before the wireless transmission of the first wireless transmission unit is terminated by the first time limit, thereby controlling wireless transmission of the wireless signal modulated in accordance with the audio signal by the first wireless transmission unit and wireless transmission of the wireless signal modulated in accordance with the audio signal by the second wireless transmission unit to be performed simultaneously for a predetermined time;
a second control unit that controls the wireless transmission of the first wireless transmission unit to start before the wireless transmission of the second wireless transmission unit ends due to the second time limit, so that the wireless transmission of the first wireless transmission unit and the wireless transmission of the second wireless transmission unit are performed simultaneously for a predetermined time. The wireless communication system described in claim 7 or 8, wherein the first time limit and the second time limit are the same or different from each other. The wireless communication system described in any one of claims 7 to 9, wherein the second control unit controls wireless transmission by the first wireless transmission unit and wireless transmission by the second wireless transmission unit to be repeated alternately. The wireless communication system described in claim 10, wherein the second control unit, when controlling the wireless transmission of the first wireless transmission unit and the wireless transmission of the second wireless transmission unit to be alternately repeated, controls the first wireless transmission unit to wirelessly transmit on the first channel or the third channel after the wireless transmission of the second wireless transmission unit. A wireless communication system according to any one of claims 7 to 11, wherein the second control unit initiates transmission from the first wireless transmission unit in response to a transmission key being turned on. the audio signal is an audio signal transmitted in a predetermined wireless system,
The wireless communication system according to any one of claims 7 to 11, wherein the second control unit starts transmission of the first wireless transmission unit when the audio signal becomes equal to or greater than a predetermined threshold value. a wireless receiving unit that performs carrier sensing while scanning channels to search for an unused channel before starting wireless transmission of at least one of the first and second wireless transmitting units;
The wireless communication system according to any one of claims 7 to 13, wherein the second control unit controls the first and second wireless transmission units to transmit wirelessly using the searched unused channels. A wireless communication system comprising the wireless communication device according to any one of claims 1 to 5,
the first control unit controls, when the first and second wireless receiving units each receive an end signal, to mute an audio signal output from the wireless receiving unit that has received the end signal;
The wireless communication system according to any one of claims 7 to 14, wherein the second control unit controls the first and second wireless transmission units to wirelessly transmit an end signal at the end of each wireless transmission.