Wireless communication system and wireless communication device

Abstract

This enables continuous communication without pause in a wireless communication system with a maximum communication time of three minutes, where responses are repeated within two seconds of the end of transmission (continuous communication) and can continue without carrier sense (CS), with a two-second pause after three minutes. [Solution] Each wireless communication device has two receiver-demodulators with different channels, chA and chB, a modulator-transmitter that can switch between these channels, and a player that synthesizes the output of each receiver-demodulator to play audio, and when 2 minutes and 30 seconds have passed since the start of communication on chA, the receiver-demodulator on the chB side repeatedly performs CS, and if the most recent CS check result is an idle state when transmission stops or the device becomes unresponsive, the channel of the modulator-transmitter is switched from chA to chB to continue continuous communication. By alternately switching channels while managing time, it is possible to talk in continuous communication with no time limit without being restricted by downtime.

Description

[Technical field]

[0001] This document relates to a wireless communication system and wireless communication device that, in a wireless station standard specification, stipulates that when communication time in a simplex communication method exceeds a predetermined time limit, the communication must be terminated and a predetermined pause must be provided before communication can be resumed. This document relates to a wireless communication system and wireless communication device that avoids the restrictive condition without violating the provisions and spirit of the standard specification and ensures 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 and other work sites, and indoors at relatively large restaurants and home improvement centers with large spaces, for business-related communication between employees.

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

[0004] In addition, as a line connection procedure in a simplex system between radio stations, an example of the procedure shown in Figure 6 (same in both Volumes 1 and 2) is shown. In principle, however, each radio station is required to perform 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 there are exceptions to this rule, such as "a function that automatically limits communication time to three minutes or less and does not initiate any further communication until two seconds have elapsed since the end of the previous communication." Most radio stations in actual use are equipped with the latter exceptional function, which has more relaxed limiting conditions. As mentioned above, the maximum communication time is set at three minutes, but communication in which a response is repeated within two seconds after the end of transmission is considered to be one continuous communication, and as long as the communication time is within three minutes, there is no need to perform carrier sensing each time a call is transmitted, allowing for smooth communication without cutting off 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 imposed. Then, carrier sensing must be performed again to ensure that no interference is caused to other communications before transmission can be resumed.

[0006] The above relates to wireless communication devices that meet specific low-power standards. However, digital simplex radio devices use a digital communication method, which gives them good sound quality and high confidentiality, and they can also output antenna power up to 5W. As a result, they are widely used for communication at event venues and leisure facilities, as well as for security services.

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

[0008] As with the specific low power standard, registered stations among digital simplex radio stations are required, in principle, to 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 receiving input voltage of 7 μV or more.

[0009] The general conditions for registered stations include that "they must be equipped with a transmission time limiting device that automatically stops transmission if the time for a single transmission exceeds five minutes, and does not allow transmission to resume until a transmission pause of at least one minute has elapsed." However, the line connection procedures stipulate that "if carrier sensing is performed and radio waves are transmitted, carrier sensing may be omitted for five consecutive minutes from the time the radio waves were transmitted, unless the transmission stop and deadlock 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 the end of transmission is considered to be one continuous communication, and so long as it is within 5 minutes, there is no need to perform carrier sensing each time a call is transmitted. 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 inserted. Then, carrier sensing is performed again to confirm that the communication is not interfering with other communications before transmission is resumed.

[0010] As described above, the communication time for specific low-power radio stations / digital simplex radio stations (registered stations) is limited to three and five minutes, respectively, and if the communication time exceeds the time limit, the communication must be terminated and a pause of at least two seconds and one minute must be allowed before it 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, which relate to a mobile communication system related to PHP (Personal Handy Phone) in 1993, 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, automatically initiates a call to the party that was on the line before the call was disconnected. [Prior art documents] [Patent documents]

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

[0013] [Non-Patent Document 1] Association of Radio Industries and Businesses, "Standard for Specified Low-Power Radio Stations / Radio Equipment for Wireless Telephones", RCR STD-20, Version 5.1, revised October 29, 2021 [Non-Patent Document 2] Association of Radio Industries and Businesses, "Radio Equipment / Standards 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 it detects that a predetermined call time (3 minutes) has elapsed, 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 / no-signal state every 3 minutes.

[0015] This is also the case for the communication standards related to specific low-power radio stations / digital simplex radio stations in Non-Patent Documents 1 and 2, where after the communication is forcibly terminated after the 3-minute / 5-minute communication limit has elapsed, respectively, there is a 2-second / 1-minute pause, and then the carrier sense time (0.2 seconds or more) related to the call operation is added, and communication can be resumed 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 / 5 minutes. In such cases, a pause of 2 seconds / 1 minute, respectively, must be inserted, and naturally the call will 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 pause time setting as described above, each wireless communication device is provided with two receiving and demodulating units, thereby enabling communications that do not require carrier sense to be performed without an intervening pause time while still complying with the communication standard. [Means for solving the problem]

[0018] The first invention relates to a wireless communication system including a plurality of wireless communication devices, the standard specifications of which are as follows: 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 unless 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 a transmission stop and 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 resetting means for terminating communication on the channel set by the modulation-transmission unit and returning 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 changing means for terminating communication on the channel set by the modulation-transmission unit and switching the set channel to another channel when the communication time has elapsed beyond the predetermined time T1, wherein each of the wireless communication devices 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 mentioned in the [Background Art] section above, according to the standard specifications for wireless stations, if a communication involves repeated responses within a predetermined time t after the end of one transmission, there is no need to perform carrier sensing after each transmission, and continuous communication can be carried out smoothly without cutting off the beginning of the transmission. However, since the maximum call time 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 of communication is exceeded, and communication cannot be resumed until the predetermined time T2 has elapsed. The purpose of imposing such a limit on communication time is to prevent one communication channel from being monopolized 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 play 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 sense continues for the predetermined time T1 after the start of transmission accompanied by carrier sense, the device automatically terminates communication on the currently set channel of the modulation / transmission unit, changes the currently set channel to the other channel, and immediately performs carrier sense 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 standard for wireless stations, when communication not requiring carrier sensing has continued 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 is resumed, so that restriction is not imposed and there is no need to insert a pause. In addition, the demodulated signals from the two receiving and demodulating sections are always combined in the audio reproducing section and audio is reproduced, 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 for which the standard specification for a wireless station requires 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 the restriction, subsequent communication is not performed unless 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 and dead state continues for a predetermined time t or more. The wireless communication device has two receiver / demodulator units set to different channels, and the channel of each receiver / demodulator unit is set to the channel of each receiver / demodulator unit. a modulation / transmission unit which is switched to one of the channels set by said modulation / transmission unit and set to one of the channels set by said modulation / transmission unit; a voice reproduction unit which combines the demodulated signals of said reception / demodulation units and reproduces voice; a timing means which measures said predetermined times t and T1; a reset means which, when a transmission stop and an insensitive state continue for more than said predetermined time t after communication has started, terminates communication on the channel set by said modulation / transmission unit and returns to a standby state while maintaining said set channel; and a channel changing means which, when communication time has elapsed beyond said predetermined time T1, terminates communication on the channel set by said modulation / transmission unit and switches said set channel to the other channel.

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

[0023] The second invention is a wireless communication device having a standard specification for a wireless station, which is provided with the following conditions: 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 the communication is terminated based on the limitation, the subsequent communication is not performed unless a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required during the communication time from the first transmission after carrier sense is 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 includes two receiver-demodulators set to different channels, a modulator-transmitter that is switched to one of the channels of the receiver-demodulators, a voice reproducing unit that synthesizes the demodulated signals of the receiver-demodulators to reproduce voice, a timer that measures the predetermined time t and T1 and the predetermined time T3 (where T1-6 seconds ≧ T3 ≧ T1-60 seconds), and a timer that, when a transmission stop and a dead state continue for the predetermined time t or more after the start of communication, ends communication on the channel set by the modulator-transmitter and maintains the set channel. a reset means for resetting the state of the receiving / demodulating unit to a standby state while holding the channel, a carrier sense implementation means for repeatedly implementing carrier sense by the receiving / demodulating 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 in 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, when a transmission instruction input is made before the predetermined time t has elapsed after the status monitoring means detects the transmission stop or dead state, confirming the result of the implementation of the carrier sense most recently at the time of the input, a reception confirmation means for confirming whether or not a signal is received in the receiving / 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 and setting 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 a signal 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 input is received 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 confirmed to be in an idle state by the carrier sense confirmation means and starts transmission, while in another wireless communication device, when reception is received 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 play audio, while the modulating and transmitting unit is switchably set to one of the two channels, just like in the first invention. The carrier sense implementation means of each wireless communication device repeatedly implements carrier sense in the reception / demodulation section to which a channel other than the currently set channel of the modulation / transmission section is set. The timing means measures the predetermined times t and T1, and the predetermined time T3. Here, the predetermined time T3 is a time from the start of communication, similar to the predetermined time T1, and is set within a predetermined time period before the predetermined time T1 has elapsed (i.e., 60 seconds before 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 means has timed a predetermined time T3 from the start of communication, the status monitor means monitors whether a transmission stop and a dead state occur on the currently set channel. In this second invention, the detection of a transmission stop and an unresponsive state by the status monitoring means is used as a starting event, and when a transmission instruction is input before a predetermined time t has elapsed from the time of detection, the carrier sense confirmation means checks the result of the most recent carrier sense performed by the carrier sense implementation means at that time, and when 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 above-mentioned transmission stop and 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 radio waves from that transmitting terminal. In a wireless communication device corresponding to the other terminal, after the status monitoring means detects a stop of transmission and an unresponsive state, if an input is confirmed in the receiving and demodulating unit (carrier sense being performed) related to the other channel before a predetermined time t has elapsed, 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 their responses are continuous and the dead state does not continue for more than the specified time t, if the specified time T3, which is the timing at which the status monitoring means stops transmission and starts monitoring for the dead state, is set within a range from 60 seconds to 6 seconds before the specified 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 be started before the specified time T1 has elapsed from the start of communications and before the specified time t has elapsed from the time the transmission stop and dead state were detected. In particular, in the case of the second invention, carrier sensing is repeatedly performed before a transmission instruction is input, and by simply confirming that the most recent result is an idle state, it is possible to immediately switch to a new channel and transmit voice. This means that, unlike the first invention, there is no delay in the start of communication on the changed channel due to the time required for carrier sensing, and smooth communication can be continued without any cut-off in the voice.

[0025] A wireless communication device applied to a wireless communication system according to a second aspect of the present invention has the following configuration. In a wireless communication device for which the standard specification for a wireless station specifies that when one channel is selected from a group of available channels and simplex communication is performed, communication time is automatically limited to within a predetermined time T1 from the start of communication, and when communication is terminated based on the restriction, subsequent communication is not performed unless 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 a transmission stop and dead state continues for a predetermined time t or more, the device comprises two receiver / demodulator units set to different channels, a modulator / transmitter unit which is switched to and set to one of the channels of each receiver / demodulator unit, an audio player which synthesizes the demodulated signals of each receiver / demodulator unit to play audio, a timer for timing each of the predetermined times t and T1 as well as a predetermined time T3 (where T1-6 seconds ≧ T3 ≧ T1-60 seconds), and when a transmission stop and dead state continues for the predetermined time t or more after the start of communication, the device terminates communication on the channel set by the modulator / transmitter unit and maintains the set channel. a reset means for returning the state to a standby state as it is, a carrier sense implementation means for repeatedly implementing carrier sense by the receiving and demodulating means to which the other channel other than the currently set channel of the modulation and transmitting means is set, a status monitoring means for monitoring whether or not a transmission stop or dead state occurs in 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 input is received before the predetermined time t has elapsed after the status monitoring means detects the transmission stop or dead state, confirming the result of the execution of the carrier sense most recently at the time of the input, a reception confirmation means for confirming whether or not there is a reception in the receiving and demodulating means 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 and setting the currently set channel of the modulation and transmitting unit to the other channel when an idle state is confirmed by the carrier sense confirmation means or when there is a reception by the reception confirmation means.

[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 performs carrier sense using the receiving and demodulating unit to which the other channel other than the currently set channel of the modulation and transmission unit is set from the point when the communication time has elapsed the specified time T3, and that a carrier sense stop means be provided for stopping 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. Carrier sensing is not performed repeatedly all the time, but is performed only during required time periods, thereby reducing the operational burden on the wireless communication device. In addition, 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, it is desirable for the wireless communication device to return to a standby state while maintaining the set channel of the modulation transmission unit. In addition, when 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 when 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. Effect of the Invention

[0027] In a simplex communication network composed of radio communication devices that are specific 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 sensing is required only for the first transmission, and communication can be continued without carrier sensing for subsequent transmissions. However, if the communication 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 in which transmission and response are repeated so that communication can be continued 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 not substantially limited by the maximum communication time T1 (and therefore has no downtime of the predetermined time T2). [Brief description 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. [Diagram 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]. [Diagram 3] 1 is a timing chart showing the state of continuous communication in a simplex mode under the communication time limit based on the standard specifications of a wireless station, where (A) shows the communication state in the conventional technology, (B) shows the communication state in the first embodiment, and (C) shows the communication state in the second embodiment. [Figure 4] 4 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] 11 is a communication sequence diagram in which wireless communication terminals serving as specific low-power wireless stations establish a line connection in simplex communication, and then return to standby due to the application of a communication integrated time limit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred 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 which are specific 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 and demodulating units RX1-chA and RX2-chB, which are set to two different channels chA and chB, and the receiving signals corresponding to each of the set channels are demodulated. Each of these demodulated signals (received audio signals) is then combined in signal combiner 11, amplified in amplifier 12, and reproduced as audio in speaker 13.

[0031] On the other hand, in the transmission system, when the transmission mode is set by the PTT button of 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 that is switched to and set as 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, in Figure 2, the two wireless communication devices 100, 200 are abstractly represented by only a modulation transmission unit TX and two reception demodulation units RX1-chA, RX2-chB, and the demodulated signals of each reception demodulation unit RX1-chA, RX2-chB are always synthesized to play audio. Therefore, each wireless communication device 100, 200 can enter a simplex communication state using channel chA [Figure 2(A)] and 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 specific 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 be continued without carrier sense for subsequent transmissions. However, that 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. In terms of time, this results in a communication state as shown in Figure 3(A), where even if the communication is continuous, it will be terminated immediately after three minutes have elapsed since the start of communication, and after a two-second pause, a new carrier sense will be performed. If an idle state is confirmed, transmission can be resumed and the communication 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 need to repeat the content of the call during the interruption after communication is resumed. Therefore, in this embodiment, as shown in FIG. 3(B), when the longest communication time of 3 minutes has elapsed since the start of the 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 above standard is a restriction on 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 / 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 transmission unit TX between chA and chB, thereby continuing continuous communication by alternating between the 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, 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 of the wireless communication device 100 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 receiving input power of the receiving and demodulating unit RX1-chA, and if it is in an idle state, the modulation and transmitting unit TX-chA transitions directly 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 measuring time using a built-in timer to measure the longest communication time T1 (=3 minutes) (S5).

[0038] Meanwhile, in the wireless communication device 200, in the standby state, the receiving and demodulating unit RX1-chA receives the transmitted radio waves from the wireless communication device 100, and at the start of the reception, the system control unit 17 starts counting the time of the built-in timer to measure the maximum communication time T1 (=3 minutes) (S11, S12). In the above 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 of the wireless communication devices 100 and 200 receives radio waves from the other side at a receiving and demodulating unit to which a channel different from the set channel of the modulation transmission unit TX is set, there is no need to initially set the same channels for 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 monitoring 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 longest 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). Moreover, in each of the wireless communication devices 100 and 200, the setting channel of the modulation transmission unit TX is immediately switched from chA to chB and the device goes into a standby state (S10, S11 / S17, S18).

[0040] In addition, if channel chA is busy when carrier sensing is performed due to the initial call (S3, S4:N), or if transmission is stopped or there is a dead state for a predetermined time t (=2 seconds) or longer during continuous communication (S6, S7:Y / S13, S14:Y), the setting channel chA of the modulation transmission unit 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 transmission unit TX of each wireless communication device 100, 200) from chA to chB, one of the wireless communication devices 100, 200 can immediately become a first call terminal from the standby state and resume communication without considering the pause time of the specified time T2 (=2 seconds) as a penalty (S17, S18 → S21 to S23).

[0042] The operating procedures (S21 to S29) of the wireless communication device that has become the first called terminal are similar to the operating procedures (S3 to S10) of the wireless communication device 100 that was originally the calling terminal, except that the communication channel is chB versus chA, and the operating procedures (S31 to S37) of the other wireless communication device that has become the called terminal are similar to the operating procedures (S12 to S18) of the wireless communication device 200 that was originally the called terminal, except that the communication channel is chB versus 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 transmission 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 specified time T2 (=2 seconds) and, in principle, it is possible to perform continuous communication without time restrictions. As mentioned above, if a transmission stop or dead zone occurs for a predetermined period of time t (=2 seconds) or longer 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 according to the prior art from the viewpoint of voice communication, as is clear from a comparison of (A) and (B) of FIG. 3, when continuous communication is interrupted at the longest communication time T1 (=3 minutes), in the prior art of FIG. 3 (A), even if a call is made immediately, there will be a call interruption time equivalent to a total of 2.2 seconds, which is at least the pause time of T2 (=2 seconds) and the 0.2 seconds required for carrier sense, and the call will be completely interrupted for a moment and its continuity will be lost. On the other hand, in FIG. 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 channel switching, which is only an extremely short interruption, and voice reproduction is always performed for a signal obtained by combining the demodulated signals of the reception modulation units RX1-chA and RX2-chB, so that the continuity of the call is hardly lost.

[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 which are specific low-power wireless stations, and similarly to the first embodiment, the configuration of the wireless communication devices is as shown in FIG. In addition, the receiving system of the wireless communication device is equipped with receiving and demodulating units RX1-chA and RX2-chB which are set to two different channels chA and chB, and the receiving signals corresponding to each of the set channels are demodulated by each receiving and demodulating unit RX1-chA and RX2-chB, and each of the demodulated signals is synthesized by a signal synthesizer 11 and reproduced as audio by a speaker 13. In the transmitting system, the audio signal input from a microphone 14 is amplified, and in a modulation transmitting unit TX, the carrier of the channel which is switched to and set to 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, which is the same as in the first embodiment.

[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 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 and dead state within the longest communication time T1 (= 3 minutes) is used as a starting 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 the 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, since 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, it is assumed that the PTT button on the operation unit 18 of the wireless communication device 100 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 receiving input power of the receiving and demodulating unit RX1-chA, and if it is in an idle state, the modulation and transmitting unit TX-chA transitions directly 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 for measuring 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 executes 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). This continuous communication is terminated if a transmission stop or dead state occurs for a predetermined time t (=2 seconds) or more during the communication, and the communication returns to a standby state with the same channel setting (S47 → S41). However, if the continuous communication continues as is 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, which is not the set channel of the modulating and transmitting unit TX-chA (S48, S49).

[0051] In normal continuous communication, responses are usually exchanged within about 5 to 20 seconds, and transmission stoppage and dead zones are inevitable during such communication. In this embodiment, however, the transmission stoppage and dead zone are regarded as the starting event, and the system control unit 17 starts a timer for timing a predetermined time t (=2 seconds) (S51), and monitors whether the PTT button on the operation unit 18 of the own device is turned on and a transmission command is input or whether there is a reception at the receiving and demodulating unit RX2-chB within the predetermined time t (S52 to S54 → S52).

[0052] Here, when 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 a calling / transmitting terminal and starts continuous communication, and then starts continuous communication again from the state of being a transmitting terminal after the channel is switched.

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

[0054] In addition, when the carrier sense using the receiving and demodulating unit RX1-chA at the time of the initial call indicates a busy state (S44:N), when there is a transmission stop and a dead state for a predetermined time t (=2 seconds) or more during continuous communication and the continuous communication ends (S47:Y), and when there is a transmission stop and a dead state after the timer has counted the predetermined time T3 and there is no transmission command input or reception to the receiving and demodulating unit RX2 after the predetermined time t (=2 seconds) or more has passed (S54:Y), the settings of the modulating and transmitting unit TX-chA are left unchanged and the initial standby state is restored (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 similar to that of FIG. 5A, except that the handling of channels chA and chB is reversed. Therefore, with regard to the explanation of the operation procedure in FIG. 5B, it is sufficient to understand the explanation of the operation procedure in FIG. 5A with chA and chB reversed, and the explanation will be omitted here.

[0056] However, the operational procedures in FIG. 5A and FIG. 5B are mutually connected, and the connection origins and destinations are indicated by circled numbers. Steps S58 and S61 in FIG. 5A are procedures relating 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 FIG. 5B, “Continuation of continuous communication (chB).” Also, steps S88 and S91 in FIG. 5B are procedures relating 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 FIG. 5A, “Continuation of continuous communication (chA).”

[0057] Incidentally, the above describes the operating procedure on the wireless communication device 100 side. However, the operating procedure on the wireless communication device 200 side, which is the other end of the simplex communication, is basically the operating procedure shown in Figures 5A and 5B, except that the transmission and reception are in the reversed relationship. That is, when the terminal is in the initial standby state or when it becomes in the standby state during the process, the relationship between transmission and reception is determined depending on whether it becomes a calling terminal first, but after the terminal transitions to continuous communication (S46, S76) and the timer has elapsed a predetermined time T3 (S48:Y, S78:Y), if a transmission instruction input is received within a predetermined time t (=2 seconds) from the time when the transmission is stopped and the dead state occurs (S50 to S52:Y, S80 to S82:Y), the terminal becomes a transmitting terminal on the newly switched communication channel (S55 to S58, S85 to S88) on the condition that the result of the carrier sense is an idle state. Conversely, if there is no transmission instruction input and reception is received in the receiving and demodulating unit RX that 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 a 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 the carrier sensing 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 necessary (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, 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 specific 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 that 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 specific low-power wireless stations and digital simplex wireless stations (registered stations). [Explanation of symbols]

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

Claims

1. In a wireless communication system configured with multiple wireless communication devices, the standard specifications for wireless stations are as follows: 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 unless a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required during the communication time from the first transmission after carrier sense is performed, and communication is terminated if transmission is stopped and a dead state continues for a predetermined time t or more. each of the wireless communication devices comprises two reception / demodulation units set to different channels, a modulation / transmission unit switched to one of the channels of the reception / demodulation units, a voice reproduction unit which synthesizes the demodulated signals of the reception / demodulation units to reproduce voice, a timing means for timing the predetermined times t and T1, a reset means for terminating communication on the channel set by the modulation / transmission unit and returning 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 changing means for terminating communication on the channel set by the modulation / transmission unit and switching the set channel to the other channel when communication time has elapsed beyond the predetermined time T1, A wireless communication system characterized in that, when each of the wireless communication devices becomes a calling terminal after the communication time has elapsed the specified time T1 but before the specified time T2 has elapsed, the wireless communication device performs carrier sense in the receiving / demodulating unit corresponding to the same channel as the set channel of the modulating / transmitting unit after the channel changing 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 changing 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. A wireless communication device that, as a standard specification for a wireless station, when one channel is selected from a group of available channels and simplex communication is performed, automatically limits the communication time from the start of communication to within a predetermined time T1, and when the communication is terminated based on the limit, the communication is not performed until a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required during the communication time from the first transmission after carrier sense is performed, and communication is terminated if a transmission stop and a dead state continue for a predetermined time t or more. a modulation / transmission unit which is switched to one of the channels of the reception / demodulation units; a voice reproduction unit which synthesizes the demodulated signals of the reception / demodulation units to reproduce voice; a timing means which measures the predetermined times t and T1; a reset means which, when a transmission stop and dead state continues for the predetermined time t or more after communication has started, terminates communication on the channel set by the modulation / transmission 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 modulation / transmission 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 a result of carrier sense after channel switching by said channel changing means is a busy state, the wireless communication device returns to a standby state while maintaining the channel set by said modulation transmission section.

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 with multiple wireless communication devices, the standard specifications for wireless stations are as follows: 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 unless a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required during the communication time from the first transmission after carrier sense is performed, and communication is terminated if transmission is stopped and a dead state continues for a predetermined time t or more. Each of the wireless communication devices includes two reception / demodulation units set to different channels, a modulation / transmission unit switched to one of the channels of the reception / demodulation units, a voice reproduction unit which synthesizes the demodulated signals of the reception / demodulation units to reproduce voice, 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 which, when a transmission stop and dead state continues for the predetermined time t or more after communication has started, ends 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 which repeatedly implements carrier sense by the reception / demodulation unit set to the other channel other than the currently set channel of the modulation / transmission unit, and a reset unit which, when communication time exceeds the predetermined time T3, a status monitoring means for monitoring whether a transmission stop or dead state occurs in the currently set channel of the modulation transmission unit after the time t has elapsed; a carrier sense confirmation means for, 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 dead state, confirming the result of the most recent carrier sense at the time of the input; a reception confirmation means for confirming whether a reception is present in the receiving and 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 dead state; and a channel change means for switching and setting 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, In the wireless communication device in which the status monitoring means detects a transmission stop and an unresponsive state after the communication time has elapsed for the predetermined time T3 and 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 which has been confirmed to be in an idle state by the carrier sense confirmation means and starts transmission, while in the other wireless communication devices, when reception is received by the receiving / demodulating 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 of claim 9, wherein in each of the wireless communication devices, the carrier sense implementation means repeatedly performs carrier sense by the receiving and demodulating unit to which the other channel other than the currently set channel of the modulation and transmission unit is set from the point when the communication time has elapsed the predetermined time T3, and a carrier sense stop means is provided for stopping 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 of the wireless communication devices, 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 wireless communication 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, 10 or 11, 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, 10 or 11, wherein the predetermined time T1 is 5 minutes, the predetermined time T2 is 1 minute, and the predetermined time t is 3 seconds.

14. A wireless communication device that, as a standard specification for a wireless station, when one channel is selected from a group of available channels and simplex communication is performed, automatically limits the communication time from the start of communication to within a predetermined time T1, and when the communication is terminated based on the limit, the communication is not performed until a predetermined time T2 has elapsed after the predetermined time T1 has elapsed, carrier sense is not required during the communication time from the first transmission after carrier sense is performed, and communication is terminated if a transmission stop and a dead state continue for a predetermined time t or more. a modulation transmission unit which is switched to one of the channels of the reception / demodulation units; a voice reproduction unit which synthesizes the demodulated signals of the reception / demodulation units to reproduce voice; a timing means which measures the predetermined times t and T1 and a predetermined time T3 (where T1-6 seconds ≧ T3 ≧ T1-60 seconds); a reset means which, when a transmission stop and a dead state continue 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 means which repeatedly implements carrier sense by the reception / demodulation unit which is set to the other channel which is not the current set channel of the modulation transmission unit; a status monitoring means for monitoring whether a transmission stop or dead state occurs in the currently set channel of the modulation transmission unit after that time point; a carrier sense confirmation means for confirming a result of the most recent carrier sense at the time point of input 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 dead state; a reception confirmation means for confirming whether there is a reception in the reception demodulation 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 dead state; and a channel change means for switching and setting 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. A wireless communication device comprising:

15. The wireless communication device of claim 14, wherein the carrier sense implementation means repeatedly performs 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 from the point when the communication time has elapsed the predetermined time T3, and further comprises a carrier sense stop means for stopping 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 a transmission instruction and, if it is 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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