Wireless communication system and wireless communication device

Abstract

To enable continuous communication without a pause time in a radio communication system in which communication (continuous communication) in which the longest communication time is three minutes and a response is repeated within two seconds after the end of transmission can be continued without carrier sense (CS), and a pause time of two seconds is provided when three minutes are exceeded.SOLUTION: Each radio communication equipment is provided with two reception demodulation parts setting different channels chA and chB, a modulation transmission part capable of switching and setting the channels, and a reproduction part synthesizing the output of each reception demodulation part and reproducing the voice, and when continuous communication is performed by switching the channel of the modulation transmission part from chA to chB when two minutes and thirty seconds elapse from the start of communication on the channel chA, the CS is repeatedly performed by the reception demodulation part on the side of chB, and when the transmission stop and the dead state are generated, the channel is switched to the channel chB. By alternately switching the channels while performing time management, it is possible to perform a call in continuous communication without time limitation without being restricted by a pause time.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This document relates to a wireless communication system and a wireless communication device that, when a standard specification for a wireless station stipulates that if the communication time in a simplex communication system exceeds a predetermined time limit, the communication must be terminated and a predetermined pause must be set before the communication can be resumed. This document provides a method for avoiding this limiting condition without violating the provisions and intent of the standard specification, thereby ensuring substantial continuity of communication. [Background technology]

[0002] Wireless communication devices that comply with the specified low-power standard are used for short-distance voice communication using the 400 MHz band, and are also license-free radio stations, so they are used outdoors at various construction sites such as building sites, and indoors at relatively large restaurants and spacious home improvement stores for business-related communication between employees.

[0003] The radio stations of this standard are based on the established standards in Non-Patent Document 1 below. Volume 1 of the same document specifies that for simplex communications with an antenna power of 10mW or less in multiple emission types such as F3E, a total of 20 channels can be selected and used: channel numbers 20 to 30 in Table 3-3 and channel numbers 41 to 49 in Table 3-5. Also, Volume 2 of the same document specifies that for radio stations of the same standard, 4-value FSK digital systems can be selected and used from channel numbers 1 to 38 in Table 3-2 (however, channel number 15 is the paging channel) for simplex communications with an antenna power of 10mW or less in emission types F1D or F1E.

[0004] In addition, an example of the procedure shown in Figure 6 (same in Volumes 1 and 2) is given as a line connection procedure between radio stations in a simplex system. In principle, each radio station is required to perform a carrier sense for at least 0.2 seconds on the channel related to the transmission before transmitting, and to confirm that there are no radio waves from other radio stations whose received input power value is -96 dBm or more at the input point of the power feeder before transmitting.

[0005] In principle, radio stations are required to be equipped with a transmission time limiting device, but as an exception, there are those that "have the function of automatically limiting communication time to within three minutes and not communicating again until two seconds have passed since the end of communication," in which case the installation of the transmission time limiting device is not required. Most radio stations that are actually in use have the latter exceptional function, which has more relaxed restriction conditions. As mentioned above, the maximum communication time is set at 3 minutes, but communication in which a response is repeated within 2 seconds after the transmission is completed is considered to be one continuous communication, and as long as the communication time is within 3 minutes, there is no need to perform carrier sensing each time a call is sent, allowing for smooth communication without any cut-off at the beginning of each call. On the other hand, if the communication time exceeds the three-minute limit, the transmission must be automatically terminated and a pause of at least two seconds must be allowed, after which carrier sensing must be performed again to ensure that no interference is caused to other communications before transmission can be resumed.

[0006] The above applies to radio communication devices that meet specific low-power standards, but digital simplex radio devices use a digital communication method, which means they have good sound quality and high confidentiality, and they can also output antenna power up to 5W, so they are widely used for communication at event venues and leisure facilities, as well as for security work.

[0007] The digital simplex radio station is based on the standard established in Non-Patent Document 2 below. The standard is formulated to separate three modulation methods (π / 4 shift quadrature phase shift keying, real zero-point single sideband modulation, and four-level frequency shift keying), each of which uses a different radio wave format, but the number of channels available to registered stations is 97 (divided by operating area), and the number of channels available to licensed stations is 113 (divided by allocated frequency band).

[0008] As with the specific low-power standard, registered stations of digital simplex radio stations are required to, in principle, perform a carrier sense of at least 0.2 seconds, and transmit only after confirming that there are no radio waves from other radio stations with a received input voltage of 7 μV or more.

[0009] The general conditions for registered stations are that they "must be equipped with a transmission time limiting device that automatically stops transmission if the transmission time exceeds five minutes, and that will not allow transmission to resume until a transmission pause of at least one minute has passed," but the line connection procedures also stipulate that "if carrier sense is performed and radio waves are transmitted, carrier sense can be omitted for five consecutive minutes from the time the radio waves are transmitted, unless the transmission pause and inactivity state continues for three seconds or more." Therefore, the maximum communication time is set at 5 minutes, and communication in which a response is repeated within 3 seconds after transmission is completed is considered to be one continuous communication, and as long as it is within 5 minutes, there is no need to perform carrier sensing each time a call is sent. On the other hand, if the communication time exceeds five minutes, the transmission is automatically terminated and a pause of at least one minute is set. Carrier sensing is then performed again to confirm that the transmission is not interfering with other communications before resuming transmission.

[0010] As described above, the communication time for specific low-power radio stations and digital simplex radio stations (registered stations) is limited to 3 minutes and 5 minutes, respectively, and if the communication time exceeds the time limit, the communication must be terminated and a pause of at least 2 seconds and at least 1 minute must be allowed before communication can be resumed.

[0011] In relation to the operation of resuming communication after the expiration of this communication time limit, the following Patent Documents 1 and 2 relate to a mobile communication system based on PHP (Personal Handy Phone) in 1993, and disclose a wireless communication system in which, when a predetermined time (3 minutes) has elapsed between mobile wireless terminals without going through a base station, the terminal automatically disconnects the call, and after a predetermined pause time (2 seconds) has elapsed since the call was disconnected, the terminal automatically initiates a call to the party with whom the call was being made before the call was disconnected. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 7-107560 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-32568 [Non-patent literature]

[0013] [Non-Patent Document 1] Association of Radio Industries and Businesses, "Specific Low-Power Radio Stations / Radio Equipment for Radio Telephones / Standard Specifications," RCR STD-20 Version 5.1, revised October 29, 2021 [Non-patent document 2] Association of Radio Industries and Businesses, "Radio Equipment / Standard for Digital Simple Radio Stations," ARIB STD-T98 Version 2.0, revised October 4, 2023 Summary of the Invention [Problem to be solved by the invention]

[0014] According to the wireless communication systems of Patent Documents 1 and 2, when a predetermined time (3 minutes) of call time is detected, the communication is forcibly terminated and a call to the previous communication destination is automatically initiated. However, since the call is initiated after a 2-second transmission pause, communication is naturally not possible for at least those 2 seconds, and in long-term communications, there is always a 2-second transmission pause / deadband state every 3 minutes.

[0015] This is also true for the communication standards related to specific low-power radio stations / digital simplex radio stations in Non-Patent Documents 1 and 2, where communication is forcibly terminated after the 3-minute / 5-minute communication limit has elapsed, respectively, followed by a 2-second / 1-minute pause, respectively, and then a carrier sense time (0.2 seconds or more) for the call operation, and communication can then begin provided that the carrier sense result indicates an idling state.

[0016] Therefore, even in wireless communication systems using specific low-power radio stations / digital simplex radio stations, there may be cases where communications are repeated in which a response is made within 2 seconds / 3 seconds after transmission is completed, and the communication state in which carrier sense is not required may exceed 3 minutes / 5 minutes. In such cases, a 2-second / 1-minute pause must be inserted, respectively, and the call will naturally be interrupted.

[0017] Therefore, the present invention aims to provide a wireless communication system and a wireless communication device therefor, in which, when a wireless communication device (wireless station) is subject to a communication standard that imposes a limit on accumulated communication time and a setting of a pause time as described above, each wireless communication device is provided with two receiving and demodulating units, so that communication that does not require carrier sense can be performed without an intervening pause time while still complying with the communication standard. [Means for solving the problem]

[0018] The first invention is a wireless communication system configured by arranging a plurality of wireless communication devices, which are conditioned as follows as a standard specification for wireless stations: when one channel is selected from a group of available channels and simplex communication is performed, the communication time is automatically limited to within a predetermined time T1 from the start of communication, and when communication is terminated based on this limitation, subsequent communication is not performed until a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required within the communication time from the first transmission after carrier sense has been performed, and communication is terminated if a transmission stop or dead state continues for a predetermined time t or more. Each of the wireless communication devices comprises two receiver-demodulators set to different channels, a modulator-transmitter that is switchable to one of the channels of each of the receiver-demodulators, and an audio player that combines the demodulated signals of each of the receiver-demodulators to play audio. a reset means for terminating communication on the channel set by the modulation / transmission unit when a transmission stop and dead state continues for the predetermined time t or more after communication has started, and returning to a standby state while maintaining the set channel; and a channel changing means for terminating communication on the channel set by the modulation / transmission unit when the communication time has passed the predetermined time T1, and switching the set channel to another channel, wherein each of the wireless communication devices, when it becomes a calling terminal after the communication time has passed the predetermined time T1 but before the predetermined time T2 has passed, performs carrier sense in the receiving / demodulating unit for the same channel as the set channel of the modulation / transmission unit after the channel changing means has switched, and starts transmission if an idle state is confirmed.

[0019] As seen in the [Background Art] section above, according to the radio station standard, if a communication involves repeated responses within a predetermined time t after the completion of one transmission, there is no need to perform carrier sensing for each transmission, and continuous communication can be carried out smoothly without any cut-off at the start of transmission. However, since the maximum call duration is set to a predetermined time T1 from the start of communication, the continuous communication is also forcibly terminated if the predetermined time T1 from the start is exceeded, and communication cannot be resumed until a predetermined time T2 has elapsed. The purpose of imposing such a limit on communication time is to prevent one communication channel from being occupied for a long period of time by a particular group's communication, thereby preventing use by other groups.

[0020] In the wireless communication system of the first invention, each wireless communication device has two receiving and demodulating units set to different channels, and always combines the demodulated signals to reproduce audio, while the modulating and transmitting unit is switched and set to one of the two channels. Each wireless communication device manages the predetermined times t and T1 using a timing means, and when communication not requiring carrier sensing continues for the predetermined time T1 after the start of transmission accompanied by carrier sensing, it automatically terminates communication on the currently set channel of the modulation / transmission unit, changes the currently set channel to the other channel, immediately performs carrier sensing in the receiving / demodulation unit set to the other channel, and if an idle state is confirmed, transitions to transmission operation on that channel. According to the radio station standard, when communication not requiring carrier sensing continues for a predetermined time T1, a transmission pause of a predetermined time T2 must be inserted. However, in this invention, the channel is automatically changed and transmission resumes, so this restriction does not apply and there is no need to insert a pause. Furthermore, the demodulated signals from the two receiving and demodulating sections are always combined in the audio reproducing section to reproduce the audio, so there is no interruption in the received audio.

[0021] A wireless communication device applied to a wireless communication system according to a first aspect of the present invention has the following configuration. In a wireless communication device that meets the following conditions as a standard for wireless stations, when one channel is selected from a group of available channels and simplex communication is performed, the communication time is automatically limited to within a predetermined time T1 from the start of communication, and when communication is terminated based on this limitation, subsequent communication is not performed until a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required within the communication time from the first transmission after carrier sense has been performed, and communication is terminated if transmission is stopped or a dead state continues for a predetermined time t or more, the device has two receiver / demodulator units set to different channels, and the channel of each receiver / demodulator unit is set to the same channel. a modulation / transmission unit that switches to one of the channels, an audio reproduction unit that combines the demodulated signals of the reception / demodulation units to reproduce audio, a timing unit that times the predetermined times t and T1, a reset unit that terminates communication on the channel set by the modulation / transmission unit and returns to a standby state while maintaining the set channel when a transmission stop and dead state continues for the predetermined time t or more after communication has started, and a channel change unit that terminates communication on the channel set by the modulation / transmission unit and switches the set channel to the other channel when communication time has elapsed the predetermined time T1.

[0022] In the wireless communication system of the first invention, if the result of carrier sense after channel switching by the channel change means is a busy state, it is desirable that the wireless communication device return to a standby state while maintaining the set channel of the modulation transmission unit. If the wireless communication device is a specified low-power wireless station, the predetermined time T1 is set to 3 minutes, the predetermined time T2 is set to 2 seconds, and the predetermined time t is set to 2 seconds. If the wireless communication device is a digital simplex wireless station (registered station), the predetermined time T1 is set to 5 minutes, the predetermined time T2 is set to 1 minute, and the predetermined time t is set to 3 seconds.

[0023] The second invention is a wireless communication device having a standard specification for a wireless station, in which when one channel is selected from a group of available channels and simplex communication is performed, the communication time is automatically limited to within a predetermined time T1 from the start of communication, and when communication is terminated based on the limitation, subsequent communication is not performed until a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required within the communication time from the first transmission after carrier sense has been performed, and communication is terminated when transmission is stopped and a dead state continues for a predetermined time t or more. In the wireless communication system, each of the wireless communication devices comprises two receiver-demodulators set to different channels, a modulator-transmitter that is switched to one of the channels of the receiver-demodulators, an audio player that synthesizes the demodulated signals of the receiver-demodulators to play audio, a timer that measures the predetermined time t, T1, and a predetermined time T3 (where T1-6 seconds ≥ T3 ≥ T1-60 seconds), and a timer that terminates communication on the channel set by the modulator-transmitter and maintains the set channel when a transmission stop and dead state continues for the predetermined time t or more after the start of communication. and a reset means for resetting the state of the modulation / transmission unit to a standby state while holding the state of the modulation / transmission unit; a carrier sense implementation means for repeatedly implementing carrier sense by the reception / demodulation unit to which the other channel other than the currently set channel of the modulation / transmission unit is set; a status monitoring means for monitoring whether or not a transmission stop or dead state occurs on the currently set channel of the modulation / transmission unit after the communication time has elapsed the predetermined time T3; a carrier sense confirmation means for confirming the result of the carrier sense implementation immediately before the input of a transmission instruction when the status monitoring means detects the transmission stop or dead state and before the predetermined time t has elapsed; a reception confirmation means for confirming whether or not a signal is received by the reception / demodulation unit to which the other channel is set before the predetermined time t has elapsed after the status monitoring means detects the transmission stop or dead state; and a channel changing means for switching the currently set channel of the modulation / transmission unit to the other channel when an idle state is confirmed by the carrier sense confirmation means or when the presence of reception is confirmed by the reception confirmation means;The wireless communication system is characterized in that, in a wireless communication device in which the state monitoring means detects a transmission stop and a dead state and a transmission instruction is input within the predetermined time t from the time of detection, the channel change means switches the currently set channel of the modulation / transmission unit to the other channel whose idle state has been confirmed by the carrier sense confirmation means and starts transmission, while in another wireless communication device, when reception is detected by the reception / demodulation unit to which the other channel is set, the channel change means switches the currently set channel of the modulation / transmission unit to the other channel and starts reception.

[0024] In the wireless communication system of the second invention, each wireless communication device has two receiving and demodulating units set to different channels, and always combines the demodulated signals to reproduce audio, and the modulating and transmitting unit is switched and set to one of the two channels, just like the first invention. The carrier sense implementing means of each wireless communication device repeatedly implements carrier sense in the receiving / demodulating section to which the other channel, which is not the currently set channel of the modulating / transmitting section, is set. The timing means measures the predetermined times t and T1 and the predetermined time T3. Here, the predetermined time T3 is the time from the start of communication, just like the predetermined time T1, and is set within a predetermined time period before the predetermined time T1 has elapsed (i.e., from 60 seconds to 6 seconds before). For example, if the wireless communication device is a specified low-power wireless station (see Non-Patent Document 1), T1 is 3 minutes, so the predetermined time T3 is selected within the time period from 2 minutes to 2 minutes 54 seconds after the start of communication, and if it is a digital simplex wireless station (registered station), T1 is 5 minutes, so the predetermined time T3 is selected within the time period from 4 minutes to 4 minutes 54 seconds after the start of communication. When the timer has counted a predetermined time T3 from the start of communication, the status monitor monitors whether a transmission stop or dead state occurs on the currently set channel. In this second invention, the detection of a transmission stop and a dead state by the status monitoring means is used as the starting event, and if a transmission instruction is input before a predetermined time t has elapsed from the time of detection, the carrier sense confirmation means checks the results of the most recent carrier sense performed by the carrier sense implementation means at that time, and if an idle state is confirmed, the channel change means switches the currently set channel of the modulation transmission unit to the other channel. However, the series of operations that occur after the transmission stop and the detection of the dead state are related to the wireless communication device that received the transmission instruction input, i.e., the operations that occur when the device becomes a transmitting terminal, and other terminals will receive the radio waves from that transmitting terminal. In the wireless communication device corresponding to the other terminal, after the status monitoring means detects that transmission has stopped and that a dead state has occurred, if an input is confirmed in the receiving and demodulating unit (carrier sensing is being performed) related to the other channel before the lapse of a predetermined time t, the channel changing means immediately switches the currently set channel of the modulating and transmitting unit to the other channel. In communications in which transmissions and responses are continuous and the dead state does not continue for more than the predetermined time t, if the predetermined time T3, which is the timing at which the status monitoring means stops transmission and starts monitoring the dead state, is set within the range of 60 seconds to 6 seconds before the predetermined time T1 has elapsed from the start of communications, then regardless of whether the wireless communication device is a transmitting terminal or a receiving terminal, the change from the currently used channel to the other channel will be completed and voice communications can begin before the predetermined time T1 has elapsed from the start of communications and before the predetermined time t has elapsed from the time when transmission stopped and the dead state was detected. In particular, in the case of the second invention, carrier sensing is repeatedly performed before inputting a transmission instruction, and simply by confirming that the most recent result is an idle state, it is possible to immediately switch channels and proceed to voice transmission. As a result, unlike the first invention, there is no delay in starting communication on the changed channel due to the time required for carrier sensing, and smooth communication can be continued without any audio cutoff.

[0025] A wireless communication device applied to a wireless communication system according to the second aspect of the present invention has the following configuration. In a radio communication device according to a standard specification for a radio station, when one channel is selected from a group of available channels and simplex communication is performed, the communication time is automatically limited to within a predetermined time T1 from the start of communication, and when communication is terminated based on this limitation, subsequent communication is not performed until a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required within the communication time from the first transmission after carrier sense has been performed, and communication is terminated if a transmission stop or dead state continues for a predetermined time t or more. The device comprises two receiver-demodulators set to different channels, a modulator-transmitter that is switched to one of the channels of each receiver-demodulator, an audio player that combines the demodulated signals of each receiver-demodulator to play audio, a timer that measures the predetermined times t and T1 and a predetermined time T3 (where T1-6 seconds ≥ T3 ≥ T1-60 seconds), and when a transmission stop or dead state continues for the predetermined time t or more after communication has started, the device terminates communication on the channel set by the modulator-transmitter and maintains the set channel. a reset means for resetting the state of the receiving and demodulating unit to a standby state without changing the setting of the modulation and transmitting unit; a carrier sense implementation means for repeatedly implementing carrier sense by the receiving and demodulating unit to which the other channel other than the currently set channel of the modulation and transmitting unit is set; a status monitoring means for monitoring whether a transmission stop or a dead state occurs on the currently set channel of the modulation and transmitting unit after the communication time has elapsed the predetermined time T3; a carrier sense confirmation means for, if a transmission instruction is input before the predetermined time t has elapsed after the status monitoring means detects the transmission stop or dead state, confirming the result of the carrier sense implementation immediately before the input; a reception confirmation means for confirming whether a signal is received by the receiving and demodulating unit to which the other channel is set before the predetermined time t has elapsed after the status monitoring means detects the transmission stop or dead state; and a channel changing means for switching the currently set channel of the modulation and transmitting unit to the other channel when the carrier sense confirmation means confirms an idle state or when the reception confirmation means confirms the presence of reception.

[0026] In the wireless communication system of the second invention, it is desirable that the carrier sense implementation means of each wireless communication device repeatedly implements carrier sense using the receiving and demodulating unit to which the other channel other than the currently set channel of the modulating and transmitting unit is set from the point when the communication time has elapsed the predetermined time T3, and that a carrier sense stop means be provided that stops the repeated implementation of carrier sense by the carrier sense implementation means when the carrier sense confirmation means confirms the result of the implementation of carrier sense or when the reception confirmation means confirms that reception has occurred. Carrier sensing is not performed repeatedly all the time, but is performed only during required time periods, thereby reducing the operational load on the wireless communication device. Furthermore, in each wireless communication device, if the carrier sense confirmation means checks the results of the most recent carrier sense at the time of inputting a transmission instruction and finds that the device is busy, it is desirable for the device to return to a standby state while maintaining the set channel of the modulation transmission unit. In addition, if the wireless communication device is a specified low-power wireless station, the predetermined time T1 is set to 3 minutes, the predetermined time T2 is set to 2 seconds, and the predetermined time t is set to 2 seconds, and if the wireless communication device is a digital simplex wireless station (registered station), the predetermined time T1 is set to 5 minutes, the predetermined time T2 is set to 1 minute, and the predetermined time t is set to 3 seconds, as in the first invention. [Effects of the Invention]

[0027] In a simplex communication network consisting of radio communication devices that are specified low-power radio stations / digital simplex radio stations (registered stations), the standard specifications for radio stations stipulate that the maximum communication time is a specified time T1 (3 minutes / 5 minutes), and for communications that repeat responses within a specified time t (2 seconds / 3 seconds) after a single transmission is completed, carrier sense is required only for the first transmission, and communication can continue without carrier sense for subsequent transmissions, but if the communication also exceeds the specified time T1, a pause of a specified time T2 (2 seconds / 1 minute) must be provided before communication can be resumed. The wireless communication system of the present invention provides a wireless communication device with two receiver / demodulator units set to different channels, and when a voice call is made that involves repeated transmission and response so that communication can continue without the above-mentioned carrier sense, the communication channel is switched from the currently set channel to the other channel when a predetermined time T1 has elapsed from the start of communication or by the predetermined time before that, thereby realizing smooth voice communication that is essentially not limited by the maximum communication time T1 (and therefore has no downtime of the predetermined time T2). [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a block diagram of a wireless communication device applied to an embodiment of a wireless communication system of the present invention. [Figure 2] A simplified schematic diagram showing a state in which two wireless communication devices are communicating using a simplex method in a wireless communication system according to an embodiment [(A) shows the case where the channel used is chA, and (B) shows the case where the channel used is chB]. [Figure 3] 1 is a timing chart showing the state of continuous communication using a simplex method under the communication time limit based on the standard specifications of a radio station, where (A) shows the communication state in the conventional technology, (B) shows the communication state in embodiment 1, and (C) shows the communication state in embodiment 2. [Figure 4] 3 is a diagram showing an operation sequence of two wireless communication devices and a communication sequence between the wireless communication devices in the wireless communication system of the first embodiment. [Figure 5A] 10 is a flowchart showing an operation sequence of each wireless communication device in the wireless communication system of the second embodiment. [Figure 5B] 10 is a flowchart showing an operation sequence of each wireless communication device in the wireless communication system of the second embodiment. [Figure 6] This is a communication sequence diagram when wireless communication terminals serving as specified low-power wireless stations establish a line connection in simplex communication, and then return to standby mode due to the application of a communication cumulative time limit. DETAILED DESCRIPTION OF THE INVENTION

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a wireless communication system and a wireless communication device applied to the system of the present invention will be described in detail with reference to the drawings. <Embodiment 1> This embodiment relates to a wireless communication system in which simplex communication is carried out between a plurality of wireless communication devices that are specified low-power wireless stations, and the wireless communication devices have a configuration as shown in FIG.

[0030] In the receiving system of the wireless communication device in Figure 1, radio waves received by antenna 10 are input to receiving demodulation units RX1-chA and RX2-chB, which are set to two different channels chA and chB, and the received signals corresponding to each set channel are demodulated. Each demodulated signal (received audio signal) is then combined in signal combiner 11, amplified in amplifier 12, and played back as audio in speaker 13.

[0031] On the other hand, in the transmission system, when the transmission mode is set by the PTT button on the operation unit 18, the input audio signal from the microphone 14 is amplified by the amplifier 15, and in the modulation transmission unit TX, the carrier of the channel switched to chA or chB is modulated with the amplified audio signal, power-amplifying it, and the modulated signal is transmitted by radio waves from the antenna 16.

[0032] The entire system of the wireless communication device is controlled by a system control unit 17, which receives operation signals from an operation unit 18 and operation signals from each module to perform mode settings, channel settings, etc., and also controls the information display on a display unit (liquid crystal display unit) 19.

[0033] Next, Figure 2 abstractly represents two wireless communication devices 100, 200 each consisting of only a modulation transmission unit TX and two reception demodulation units RX1-chA and RX2-chB, and the demodulated signals of each reception demodulation unit RX1-chA and RX2-chB are always combined to play audio. Therefore, each wireless communication device 100, 200 can enter a simplex communication state using channel chA [Figure 2(A)] or a simplex communication state using channel chB [Figure 2(B)] simply by synchronizing the setting channels of its modulation transmission units TX with each other and switching them to chA and chB.

[0034] Incidentally, according to the above-mentioned Non-Patent Document 1, which defines the standard specifications for specified low-power radio stations, as mentioned above, the maximum communication time is a predetermined time T1 (= 3 minutes), and in the case of communication in which responses are repeated within a predetermined time t (= 2 seconds) after one transmission is completed (hereinafter referred to as "continuous communication"), carrier sense is required only at the first transmission, and communication can continue without carrier sense for subsequent transmissions, but this communication must also be terminated after the predetermined time T1 has elapsed, and transmission cannot be resumed unless a pause of a predetermined time T2 (= 2 seconds) is provided. This results in a communication state as shown in Figure 3(A) in terms of time series, where even if communication is continuous, the communication is immediately terminated after three minutes have passed since the start of communication, and after a two-second pause, a new carrier sense is performed, and if an idle state is confirmed, transmission can be resumed and the system will transition back to a continuous communication state.

[0035] The forced termination of continuous communication and the two-second pause described above result in an abrupt interruption of the call, lasting for those two seconds plus at least 0.2 seconds required for carrier sensing, and often necessitates the retransmission of the content of the call during the interruption after communication resumes. Therefore, in this embodiment, as shown in Figure 3(B), when the maximum communication time of 3 minutes has elapsed since the start of continuous communication, the channel chA used in the continuous communication up to that point is switched to the other channel chB, and if a carrier sense is performed on the switched channel chB and an idle state is confirmed, the continuous call is transitioned to using channel chB. In other words, the standard limits the communication time when one channel is used continuously, and if the channel is changed after the specified time T1 (= 3 minutes), which is the maximum communication time, has elapsed, the obligation to insert a pause of the specified time T2 (= 2 seconds) can be avoided, and call and transmission operations can be started immediately on the changed channel.

[0036] Here, we will use as an example a wireless communication system in which the two wireless communication devices 100, 200 in Figure 2 switch the setting channel of the modulation transmitter TX between chA and chB, thereby continuing continuous communication by alternating between states (A) and (B) in the same figure, and Figure 4 shows the operation sequence of each wireless communication device 100, 200 and the communication sequence between them.

[0037] In FIG. 4, first, each of the wireless communication devices 100 and 200 is in a standby state (S1, S11), and the channel of the modulation transmission unit TX of both devices is set to chA. Here, it is assumed that the PTT button on the operation unit 18 on the wireless communication device 100 side is turned on to make it a calling terminal, and the system control unit 17 of the wireless communication device 100 immediately performs carrier sense to check the received input power of the receiving and demodulating unit RX1-chA, and if it is in an idle state, the modulating and transmitting unit TX-chA proceeds to transmitting operation on channel chA (S2 to S5). Furthermore, at the time when the transmission operation is started, the system control unit 17 of the wireless communication device 100 starts counting time using an internal timer to measure the longest communication time T1 (=3 minutes) (S5).

[0038] Meanwhile, in the wireless communication device 200, the radio waves transmitted from the wireless communication device 100 are received in the receiving and demodulating unit RX1-chA in the standby state, and at the start of the reception, the system control unit 17 starts counting the internal timer to measure the maximum communication time T1 (= 3 minutes) (S11, S12). In steps S1 and S11, the wireless communication devices 100 and 200 are in standby mode and their respective modulation transmission units TX are set to channel chA. However, if the system control unit 17 is configured to automatically switch the set channel of the modulation transmission unit TX to the other channel when each wireless communication device 100 and 200 receives radio waves from the other side at a receiving and demodulating unit that is set to a channel different from the set channel of the modulation transmission unit TX, there is no need to initially align the set channels of the modulation transmission units TX of both wireless communication devices 100 and 200.

[0039] After transmission and reception between the wireless communication devices 100, 200 has begun, continuous communication using channel chA will continue under the supervision of each system control unit 17 unless a transmission stop or dead state occurs for a predetermined time period t (= 2 seconds) or longer. However, when the timer in each wireless communication device 100, 200 counts up the maximum communication time T1 (= 3 minutes), the system control unit 17 will forcibly terminate the continuous communication even if a call is in progress (S6 to S9 / S13 to S16). Furthermore, each of the wireless communication devices 100 and 200 immediately switches the set channel of the modulation transmission unit TX from chA to chB and goes into a standby state (S10, S11 / S17, S18).

[0040] In addition, if channel chA is busy when carrier sensing is performed upon initial call (S3, S4:N), or if transmission stops or an insensitive state occurs for a predetermined time t (=2 seconds) or longer during continuous communication (S6, S7:Y / S13, S14:Y), the set channel chA of the modulation transmitter TX is returned to the standby state (S4 → S1, S7 → S1 / S14 → S11).

[0041] Through the above procedure, each wireless communication device 100, 200 enters a standby state after the longest communication time T1 (= 3 minutes) has elapsed since the start of continuous communication (S5 to S11 / S12 to S18). However, in this embodiment, even though the continuous communication has violated the limit of the longest communication time T1 of the standard, by switching the communication channel (the set channel of the modulation transmitter TX of each wireless communication device 100, 200) from chA to chB, one of the wireless communication devices 100, 200 can immediately switch from the standby state to become the first calling terminal and resume communication without considering the pause time of the predetermined time T2 (= 2 seconds) as a penalty (S17, S18 → S21 to S23).

[0042] The operating procedure (S21 to S29) of the wireless communication device that has become the first called terminal is the same as the operating procedure (S3 to S10) of the wireless communication device 100 that originally became the calling terminal, except that the communication channel is chB or chA, and the operating procedure (S31 to S37) of the other wireless communication device that has become the called terminal is the same as the operating procedure (S12 to S18) of the wireless communication device 200 that originally became the called terminal, except that the communication channel is chB or chA.

[0043] Furthermore, even thereafter, each time continuous communication is continuously performed from the start point until the longest communication time T1 (= 3 minutes), the currently set channel (chA or chB) of the modulation transmitting unit TX is alternately switched to the other channel (chB or chA) to connect to a new continuous communication, so that there is no pause of the predetermined time T2 (= 2 seconds) and, in principle, continuous communication can be performed without time restrictions. As mentioned above, if transmission stops or a dead state occurs for a predetermined time t (= 2 seconds) or more during continuous communication, or if the terminal becomes the first to call and the carrier sense result is a busy state, the terminal will return to standby mode with the currently set channel at that point, and continuous communication will be interrupted.

[0044] Now, when looking at the wireless communication system of this embodiment and the wireless communication system of the prior art from the perspective of voice calls, as is clear from comparing Figures 3(A) and (B), if continuous communication is interrupted at the longest communication time T1 (= 3 minutes), in the prior art of Figure 3(A), even if a call is made immediately, there will be a call interruption time of at least T2 (= 2 seconds) and 0.2 seconds required for carrier sense, totaling 2.2 seconds, and the call will be completely interrupted and its continuity will be lost. On the other hand, in Figure 3(B) of this embodiment, the channel of the modulation transmission unit TX is switched, and the call interruption time is only the 0.2 seconds required for carrier sense by the reception demodulation unit RX on the channel side after the switch, which is only an extremely short interruption, and furthermore, voice reproduction is always performed using a signal obtained by combining the demodulated signals of the reception modulation units RX1-chA and RX2-chB, so there is almost no loss of call continuity.

[0045] <Embodiment 2> This embodiment also relates to a wireless communication system in which simplex communication is carried out between a plurality of wireless communication devices that are specified low-power wireless stations, and the configuration of the wireless communication devices is the same as in the first embodiment, as shown in FIG. Furthermore, the receiving system of the wireless communication device is provided with receiving demodulation units RX1-chA and RX2-chB which are set to two different channels chA and chB, and the receiving signals corresponding to each of these set channels are demodulated by the receiving demodulation units RX1-chA and RX2-chB, and each of these demodulated signals is synthesized by a signal synthesizer 11 and reproduced as audio by a speaker 13. The transmitting system is also the same as in the first embodiment, in that the audio signal input from a microphone 14 is amplified, and in a modulating transmission unit TX, the carrier of the channel which is switched to and set as chA or chB is modulated with the amplified audio signal and power-amplified, and the modulated signal is transmitted by radio waves from an antenna 16.

[0046] Furthermore, the entire system of the wireless communication device is controlled by a system control unit 17, which receives operation signals from an operation unit 18 and operation signals from each module to perform mode setting, channel setting, etc., and also controls the information display on a display unit (liquid crystal display unit) 19, just like in the first embodiment.

[0047] The wireless communication system of this embodiment differs from embodiment 1 in that, as shown in FIG. 3(C), the communication channel is not switched when the longest communication time T1 (= 3 minutes) has elapsed, but rather, carrier sensing is performed in advance from the point when a predetermined time T3 (= 2 minutes 30 seconds) has elapsed from the start of continuous communication (30 seconds before the elapse of T1), and the occurrence of a transmission stop or dead state within the longest communication time T1 (= 3 minutes) is used as the initiating event to switch the communication channel, thereby executing communication channel switching control that ensures no call interruption and call continuity.

[0048] Here, as in the case of embodiment 1, we will explain an example of a wireless communication system in which the two wireless communication devices 100, 200 in Figure 2 switch the setting channel of the modulation transmission unit TX between chA and chB, thereby continuing continuous communication by alternating between states (A) and (B) in the same figure, and Figures 5A and 5B show the operation sequences of each wireless communication device 100, 200. However, while Figures 5A and 5B relate to the operation of one of the wireless communication devices, the operation of the other wireless communication device will be explained using the series of steps in Figures 5A and 5B instead, as the transmission and reception are simply reversed.

[0049] In FIG. 5A, first, the wireless communication devices 100 and 200 are in a standby state (S41), and the channel of the modulation transmission unit TX of both devices is set to chA. Here, assuming that the PTT button on the operation unit 18 on the wireless communication device 100 side is turned on and the device becomes a calling terminal, the system control unit 17 of the wireless communication device 100 immediately performs carrier sense to check the received input power of the receiving and demodulating unit RX1-chA, and if it is in an idle state, the modulating and transmitting unit TX-chA proceeds to transmitting operation on channel chA (S41 to S45). In addition, when the transmission operation is started, the system control unit 17 of the wireless communication device 100 starts a timer to measure the longest communication time T1 (= 3 minutes) and the time T3 (= 2 minutes 30 seconds) until the start of the preparatory operation for channel switching (S45).

[0050] After starting the transmission operation, the wireless communication device 100 performs continuous communication (using channel chA) with the wireless communication device 200, repeating responses within a predetermined time t (=2 seconds) from the end of one transmission (S46). If this continuous communication stops transmission or becomes insensitive for a predetermined time t (= 2 seconds) or more during the communication, the communication is terminated and the system returns to the standby state with the same channel setting (S47 → S41). However, if the continuous communication continues and the timer reaches time T3 (= 2 minutes 30 seconds), the system control unit 17 repeatedly performs carrier sensing using the receiving and demodulating unit RX2-chB, which is set to the other channel chB that is not the set channel of the modulating and transmitting unit TX-chA (S48, S49).

[0051] In normal continuous communication, responses are exchanged in about 5 to 20 seconds in most cases, and transmission stops and dead states inevitably occur during such communication. In this embodiment, the system control unit 17 starts a timer that measures a predetermined time t (= 2 seconds) when transmission stops and dead states occur as a starting event (S51), and monitors whether the PTT button on the operation unit 18 of the device itself is turned on and a transmission instruction is input or whether reception is made in the receiving demodulation unit RX2-chB within the predetermined time t (S52 to S54 → S52).

[0052] Here, if a transmission instruction is input within the predetermined time t, the system control unit 17 checks whether channel chB is in an idle state in the most recent carrier sense at the time of input, and if it is in an idle state, stops the repetition of carrier sense and resets all timers, and immediately switches the setting channel of the modulation transmission unit TX from chA to chB to start audio transmission (S52 → S55 to S58). The system control unit 17 also starts the reset timer to measure new predetermined times T1 and T3 at the start of voice transmission (S58). In other words, the procedure of steps S52 → S55 to S58 corresponds to the case where the wireless communication device 100 first becomes the calling / transmitting terminal and starts continuous communication, and then starts continuous communication again from the state of being the transmitting terminal after switching channels.

[0053] On the other hand, if the system control unit 17 confirms reception at the receiving and demodulating unit RX2-chB within the predetermined time t, it stops repeating the carrier sense and resets all timers, immediately switches the setting channel of the modulating and transmitting unit TX from chA to chB, starts receiving audio, and starts the timer at the start time to measure new predetermined times T1 and T3 (S53 → S59 to S61). In other words, the procedure of steps S53 → S59 to S61 corresponds to the case where the wireless communication device 100 first becomes the calling / sending terminal and starts continuous communication, and then, after switching channels, starts continuous communication from the state of becoming the receiving terminal.

[0054] In addition, when the carrier sense using the receiving demodulation unit RX1-chA at the time of the first call indicates a busy state (S44:N), when a transmission stop or dead state occurs for a predetermined time t (=2 seconds) or more during continuous communication and the continuous communication ends (S47:Y), or when a transmission stop or dead state occurs after the timer has counted the predetermined time T3 and thereafter there is no transmission command input or reception to the receiving demodulation unit RX2 and the predetermined time t (=2 seconds) or more has passed (S54:Y), the settings of the modulation transmitting unit TX-chA remain the same and return to the initial standby state (S44:N, S47:Y, S54:Y → S41).

[0055] As is clear from comparing FIG. 5B with FIG. 5A, the flow of the operation procedure is the same as that in FIG. 5A, except that the handling of channels chA and chB is reversed. Therefore, in order to explain the operation procedure of FIG. 5B, it is sufficient to understand the explanation of the operation procedure of FIG. 5A by reversing chA and chB, and therefore the explanation will be omitted here.

[0056] However, the operation procedures in FIG. 5A and FIG. 5B are interconnected, and the circled numbers indicate the connection origins and destinations. Steps S58 and S61 in Figure 5A are procedures related to the start of voice transmission and voice reception after changing the communication channel from chA to chB, but either procedure leads to step S76 in Figure 5B, "Continuation of continuous communication (chB)." Also, steps S88 and S91 in Figure 5B are procedures related to the start of voice transmission and voice reception after changing the communication channel from chB to chA, but either procedure leads to step S46 in Figure 5A, "Continuation of continuous communication (chA)."

[0057] The above describes the operating procedure on the wireless communication device 100 side, but the operating procedure on the wireless communication device 200 side, which is the other end of the communication using simplex, is basically the operating procedure shown in Figures 5A and 5B, except that the transmission and reception are in the opposite relationship. That is, when the standby state is entered for the first time or during the standby state, the relationship between transmission and reception is determined by whether the terminal becomes the calling terminal first, but after the transition to continuous communication (S46, S76) and the timer has elapsed a predetermined time T3 (S48: Y, S78: Y), if a transmission instruction input is made within a predetermined time t (= 2 seconds) from the point at which transmission stopped and the dead state occurred (S50 to S52: Y, S80 to S82: Y), the terminal becomes the transmitting terminal on the newly switched communication channel (S55 to S58, S85 to S88) on the condition that the result of carrier sense is an idle state. Conversely, if there is no transmission instruction input and there is reception in the receiving demodulation unit RX which is set to the other channel other than the currently set channel (S50 to S53: Y, S80 to S83: Y), the channel is switched to a new communication channel and the terminal becomes the receiving terminal (S59 to S61, S89 to S91).

[0058] In this embodiment, carrier sensing is repeatedly performed from the point when the timer reaches a predetermined time T3 (S49, S79), and is stopped (S56, S86, S59, S89) when the terminal becomes a transmitting terminal and uses the result (S55, S85) or when the terminal becomes a receiving terminal and the result is no longer needed (S53, S83). However, since carrier sensing is naturally performed on the other channel than the currently set channel of the modulation transmitting unit TX and does not affect the reproduced sound, it is also possible to perform carrier sensing continuously without managing the execution time by simply controlling which of the two receiving and demodulating units RX1-chA and RX2-chB performs it.

[0059] <Other> In the above embodiments 1 and 2, a wireless communication system in a network made up of wireless communication devices that are specified low-power wireless stations has been described, but the present invention can also be applied to a wireless communication system in a network made up of wireless communication devices that are digital simplex wireless stations (registered stations), in which case the predetermined time T1 is 5 minutes, the predetermined time T2 is 1 minute, and the predetermined time t is 3 seconds, but the predetermined time T3 is the same. [Industrial Applicability]

[0060] The present invention can be applied to a simplex wireless communication system in a network consisting of wireless communication devices such as specified low-power wireless stations and digital simplex wireless stations (registered stations). [Explanation of symbols]

[0061] 10...antenna, 11...signal synthesis unit, 12...amplifier, 13...speaker, 14...microphone, 15...amplifier, 16...antenna, 17...system control unit, 18...operation unit, 19...display unit, TX...modulation transmission unit, RX1-chA...reception demodulation unit, RX2-chB...reception demodulation unit.

Claims

1. In a wireless communication system configured by arranging a plurality of wireless communication devices, the standard specifications for wireless stations are such that, when one channel is selected from a group of available channels and simplex communication is performed, the communication time is automatically limited to within a predetermined time T1 from the start of communication, and when communication is terminated based on this limitation, subsequent communication is not performed until a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required within the communication time from the first transmission after carrier sense has been performed, and communication is terminated if transmission is stopped and a dead state continues for more than a predetermined time t, each of the wireless communication devices comprises two receiving and demodulating units set to different channels, a modulating and transmitting unit which is switched to one of the channels of the receiving and demodulating units, an audio reproducing unit which synthesizes the demodulated signals of the receiving and demodulating units to reproduce audio, a timing means which measures the predetermined times t and T1, a reset means which, when a transmission stop and an inaudible state continues for the predetermined time t or more after communication starts, terminates communication on the channel set by the modulating and transmitting unit and returns to a standby state while maintaining the set channel, and a channel changing means which, when communication time has elapsed beyond the predetermined time T1, terminates communication on the channel set by the modulating and transmitting unit and switches the set channel to the other channel; A wireless communication system characterized in that, when each wireless communication device becomes a calling terminal after the communication time has elapsed the predetermined time T1 but before the predetermined time T2 has elapsed, the receiving and demodulating unit performs carrier sensing on the same channel as the set channel of the modulation and transmitting unit after the channel change means has switched, and starts transmission if an idle state is confirmed.

2. 2. The wireless communication system according to claim 1, wherein, in each of the wireless communication devices, if the result of carrier sense after channel switching by the channel change means is a busy state, the wireless communication device returns to a standby state while maintaining the set channel of the modulation transmission unit.

3. 3. The wireless communication system according to claim 1, wherein the predetermined time T1 is 3 minutes, the predetermined time T2 is 2 seconds, and the predetermined time t is 2 seconds.

4. 3. The wireless communication system according to claim 1, wherein the predetermined time T1 is 5 minutes, the predetermined time T2 is 1 minute, and the predetermined time t is 3 seconds.

5. In a wireless communication device, the standard specifications for a wireless station are such that when one channel is selected from a group of available channels and simplex communication is performed, the communication time is automatically limited to within a predetermined time T1 from the start of communication, and when communication is terminated based on this limitation, subsequent communication is not performed until a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required within the communication time from the first transmission after carrier sense has been performed, and communication is terminated if transmission is stopped and a dead state continues for more than a predetermined time t, two receiving and demodulating units set to different channels; a modulating and transmitting unit that is switched to one of the channels of the receiving and demodulating units; an audio reproducing unit that combines the demodulated signals of the receiving and demodulating units to reproduce audio; a timing means that measures the predetermined times t and T1; a reset means that, when a transmission stop and an inaudible state continues for the predetermined time t or more after communication has started, ends communication on the channel set by the modulating and transmitting unit and returns to a standby state while maintaining the set channel; and a channel changing means that, when communication time has elapsed beyond the predetermined time T1, ends communication on the channel set by the modulating and transmitting unit and switches the set channel to the other channel. A wireless communication device comprising:

6. 6. The wireless communication device according to claim 5, wherein if the result of carrier sense after channel switching by said channel change means is a busy state, the wireless communication device returns to a standby state while maintaining the channel set by said modulation transmission unit.

7. 7. The wireless communication device according to claim 5, wherein the predetermined time T1 is 3 minutes, the predetermined time T2 is 2 seconds, and the predetermined time t is 2 seconds.

8. 7. The wireless communication device according to claim 5, wherein the predetermined time T1 is 5 minutes, the predetermined time T2 is 1 minute, and the predetermined time t is 3 seconds.

9. In a wireless communication system configured by arranging a plurality of wireless communication devices, the standard specifications for wireless stations are such that, when one channel is selected from a group of available channels and simplex communication is performed, the communication time is automatically limited to within a predetermined time T1 from the start of communication, and when communication is terminated based on this limitation, subsequent communication is not performed until a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required within the communication time from the first transmission after carrier sense has been performed, and communication is terminated if transmission is stopped and a dead state continues for more than a predetermined time t, Each of the wireless communication devices comprises two receiver-demodulators set to different channels, a modulator-transmitter unit switchably set to one of the channels of the receiver-demodulators, an audio player unit that synthesizes demodulated signals of the receiver-demodulators to play audio, a timer for timing the predetermined times t and T1 and a predetermined time T3 (where T1-6 seconds ≥ T3 ≥ T1-60 seconds), a reset unit that, when a transmission stop and dead state continues for the predetermined time t or more after communication starts, ends communication on the set channel of the modulator-transmitter and returns to a standby state while maintaining the set channel, a carrier sense implementation unit that repeatedly implements carrier sense by the receiver-demodulator set to the other channel other than the currently set channel of the modulator-transmitter, and a reset unit that resets the set channel when communication time exceeds the predetermined time T3. a status monitoring means for monitoring whether a transmission stop or a dead state occurs in the currently set channel of the modulation / transmission unit after the time when the status monitoring means detects the transmission stop or the dead state; a carrier sense confirmation means for confirming the result of the most recent carrier sense at the time when a transmission instruction is input before the lapse of the predetermined time t after the time when the status monitoring means detects the transmission stop or the dead state; a reception confirmation means for confirming whether a reception is present in the receiving / demodulating unit to which the other channel is set before the lapse of the predetermined time t after the time when the status monitoring means detects the transmission stop or the dead state; and a channel change means for switching the currently set channel of the modulation / transmission unit to the other channel when the carrier sense confirmation means confirms an idle state or when the reception confirmation means confirms the presence of reception. In the case of each of the wireless communication devices, when the status monitoring means detects a transmission stop and a dead state after the communication time has elapsed for the predetermined time T3 but before the predetermined time T1 has elapsed, and a transmission instruction input is received within the predetermined time t from the time of detection, the channel changing means switches the currently set channel of the modulation-transmission unit to the other channel whose idle state has been confirmed by the carrier sense confirmation means and starts transmission, while in the case of other wireless communication devices, when reception is received by the receiving-demodulation unit to which the other channel is set, the channel changing means switches the currently set channel of the modulation-transmission unit to the other channel and starts reception.

10. The wireless communication system described in claim 9, wherein in each of the wireless communication devices, the carrier sense implementation means repeatedly performs carrier sense using the receiving and demodulating unit to which the other channel other than the currently set channel of the modulation and transmitting unit is set from the point when the communication time has elapsed the predetermined time T3, and also includes a carrier sense stop means that stops the repeated performance of the carrier sense by the carrier sense implementation means when the carrier sense confirmation means confirms the result of the carrier sense implementation or when the reception confirmation means confirms that reception has occurred.

11. The wireless communication system described in claim 9, wherein in each wireless communication device, if the carrier sense confirmation means checks the result of the most recent carrier sense at the time of inputting a transmission instruction and finds that the device is busy, the device returns to a standby state while maintaining the set channel of the modulation transmission unit.

12. 12. The wireless communication system according to claim 9, wherein the predetermined time T1 is 3 minutes, the predetermined time T2 is 2 seconds, and the predetermined time t is 2 seconds.

13. 12. The wireless communication system according to claim 9, wherein the predetermined time T1 is 5 minutes, the predetermined time T2 is 1 minute, and the predetermined time t is 3 seconds.

14. In a wireless communication device, the standard specifications for a wireless station are such that when one channel is selected from a group of available channels and simplex communication is performed, the communication time is automatically limited to within a predetermined time T1 from the start of communication, and when communication is terminated based on this limitation, subsequent communication is not performed until a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required within the communication time from the first transmission after carrier sense has been performed, and communication is terminated if transmission is stopped and a dead state continues for more than a predetermined time t, a modulation / transmission unit that is switched to one of the channels of the reception / demodulation units; an audio reproduction unit that synthesizes the demodulated signals of the reception / demodulation units to reproduce audio; a timing unit that measures the predetermined times t, T1, and T3 (where T1-6 seconds ≥ T3 ≥ T1-60 seconds); a reset unit that, when a transmission stop and a dead state continues for the predetermined time t or more after communication has started, terminates communication on the set channel of the modulation / transmission unit and returns to a standby state while maintaining the set channel; a carrier sense implementation unit that repeatedly implements carrier sense by the reception / demodulation unit that is set to the other channel other than the currently set channel of the modulation / transmission unit; a status monitoring means for monitoring whether a transmission stop or a dead state occurs in the currently set channel of the modulation / transmission unit after the time point when the status monitoring means detects the transmission stop or the dead state; a carrier sense confirmation means for confirming the result of the most recent carrier sense at the time point when a transmission instruction is input before the lapse of the predetermined time t after the time point when the status monitoring means detects the transmission stop or the dead state; a reception confirmation means for confirming whether a reception is present in the receiving / demodulating unit to which the other channel is set before the lapse of the predetermined time t after the time point when the status monitoring means detects the transmission stop or the dead state; and a channel change means for switching the currently set channel of the modulation / transmission unit to the other channel when the carrier sense confirmation means confirms an idle state or when the reception confirmation means confirms the presence of reception. A wireless communication device comprising:

15. The wireless communication device described in claim 14, wherein the carrier sense implementation means repeatedly performs carrier sense using the receiving and demodulating unit to which the other channel other than the currently set channel of the modulation and transmitting unit is set from the point when the communication time has elapsed the predetermined time T3, and also includes a carrier sense stop means that stops the repeated performance of the carrier sense by the carrier sense implementation means when the carrier sense confirmation means confirms the result of the carrier sense implementation or when the reception confirmation means confirms that reception has occurred.

16. The wireless communication device according to claim 14, wherein the carrier sense confirmation means checks the result of the most recent carrier sense at the time of inputting the transmission instruction and, if it is found to be in a busy state, returns to a standby state while maintaining the set channel of the modulation transmission unit.

17. 17. The wireless communication device according to claim 14, 15 or 16, wherein the predetermined time T1 is 3 minutes, the predetermined time T2 is 2 seconds, and the predetermined time t is 2 seconds.

18. 17. The wireless communication device according to claim 14, 15 or 16, wherein the predetermined time T1 is 5 minutes, the predetermined time T2 is 1 minute, and the predetermined time t is 3 seconds.

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