JPH0865733A - Wireless communication system - Google Patents

Abstract

PURPOSE: To perform comparatively long distance transmission when direct connection is disabled in communication equipment such as a digital cordless telephone, etc.. by relaying communication between plural communication equipment by using an antenna for relay connected with a coaxial cable. CONSTITUTION: In a digital cordless telephone system provided with two master sets 1, 2. the master sets 1, 2 are set as the master set and a slave master set, respectively, and they are connected to an exchange with a separate telephone line. The master sets 1, 2 are provided with communicable slave sets 4, 5,... The communication can be performed between the master sets 1, 2 even when they are installed at comparatively separated places. In other words, a control signal outputted from the antenna 1a for transmission of the master set 1 can be received by the antenna 51 for relay near by, and radiated from the antenna 52 for relay via the coaxial cable 53. The signal is received by the antenna 2a for transmission/reception of the master set 2 in the neighborhood of the antenna 52. In such a way, the distance between the master sets 1, 2 can be separated compared with direct transmission between the master sets 1, 2 by performing relaying and transmission by using the antennas 51, 52 and the cable 53.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system suitable for application to, for example, a digital cordless telephone device in which communication between a master unit and a slave unit is performed by transmitting / receiving digital data.

[0002]

2. Description of the Related Art A digital cordless telephone system is constructed, for example, as shown in FIG. In FIG. 3, reference numeral 1 denotes a base unit serving as a base station. The base unit 1 is connected to a telephone line and includes an antenna 1a for communicating with a handset. A plurality of (three in this case) slaves capable of communicating with the master 1 are prepared. That is, the slaves 4, 5, 6 are prepared, the antennas 4a, 5a, 6a are attached to the slaves 4, 5, 6 respectively, and the antenna 1a of the master 1 and the antennas of the slaves 4, 5, 6 are installed. 4a, 5a, 6
Wireless transmission is performed with a.

When a call is made with each of the slaves 4, 5 and 6 to the master 1 (or the other party connected to the master 1 via a telephone line), the master 1 sends a connection control signal of a predetermined format.
Then, the voice data converted into digital data is transmitted to the base unit 1 in a time division manner with the base unit 1 to make a call.

In such a digital cordless telephone device, transmission and reception are performed at the same frequency, and so-called ping-pong transmission is performed in a TDD system (time division duplex system) or a TDMA / TDD system (time division multiple access / time division). There are some that are adopted.

That is, in the case of the TDD system, for example, A in FIG.
, One channel (frequency) is temporally divided into a transmission slot T and a reception slot R, these slots T and R are alternately repeated, and a guard is provided between these slots T and R. A time (not shown) is provided. In this case, for example, each slot T and R is set to 1 msec and the guard time is set to several tens of microseconds. And
The mobile phone (slave unit) communicates with the base station (parent device) in the transmission slot T and receives from the base station in the reception slot R.

In the case of the TDMA / TDD system,
As shown in FIG. 4B, a transmission slot T and a reception slot R in one channel are used for communication between one slave unit and the master unit.
, Are used only once every several cycles, and other transmission slots T and reception slots R in the same channel are used for communication between another slave unit and the master unit, and a plurality of units are used for one channel. It is multiplexed so that communication between communication devices can be performed.

By being multiplexed in this way, the frequency band prepared for the cordless telephone can be used efficiently.

By the way, as a system configuration for such a digital cordless telephone, a system having a plurality of parent devices as shown in FIG. 5 is considered. That is,
In FIG. 5, reference numerals 1, 2 and 3 denote cordless telephone master units, and the respective master units 1, 2 and 3 are individually connected to a telephone line and communicate with a slave unit. It is provided with transmitting / receiving antennas 1a, 2a, 3a for performing. Then, the child device 4, which can communicate with each of the parent devices 1, 2, and 3,
It is assumed that 5, 6, 7, 8 ... Are prepared. At this time, each of the slave units 4, 5, ...
3 is also capable of wireless communication so that a call can be made via any of the base units. With this configuration, each cordless handset can send an outside line through which parent handset, and can also respond when any of the parent handset receives an incoming call. The range expands.

When a plurality of master units are provided in this way, a common system call code is set for each master unit 1, 2, 3 and control transmitted from each master unit 1, 2, 3 This common system call code is added to the signal,
The fact that each slave unit is commonly used can be determined by this system call code. Explaining the configuration of the system call code, first, the downlink control signal transmitted from each master unit is configured as shown in FIG. That is, the preamble PR that is the synchronization data is first followed by a fixed pattern for a predetermined period, and in the following, a unique word UW of a specific pattern indicating a control signal,
It includes a channel type C1 for communication, control data CAC indicating control contents, and error detection parity CRC.

Then, the identification code shown in FIG. 7 is transmitted by using a predetermined bit in the control data CAC. As the identification code, the system call code is transmitted using the first half 29 bits, and the additional ID is transmitted using the second half 13 bits. With this additional ID, an ID set individually for each parent device is transmitted. Note that FIG.
The control signal shown in (1) is transmitted once in 625 μsec.

In this example, the first master unit 1 of the three master units prepared is the master master unit, and the other master units 2 and 3 are slave master units. Then, the slave master units 2 and 3 receive the control signal transmitted from the master master unit 1, and the control signals from the slave master units 2 and 3 are synchronized with the reception timing of the control signal. I am trying to send you.

Here, FIG. 8 shows the configuration of the slaves 4, 5, ... Used in such a digital cordless telephone. In FIG. 8, reference numeral 11 denotes an antenna, and the data received by the antenna 11 from the master unit or another slave unit is transmitted to the wireless unit 1.
Reception processing is performed at 2, and the data is supplied to the modulation / demodulation unit 13 to demodulate the received data. Then, the demodulated received data is sent to the communication control unit 1
4 is supplied to the ADPCM codec unit 15 via 4, and the received ADPCM digital data is converted into an analog audio signal, and the analog audio signal is output from the speaker 16.

The audio signal picked up by the microphone 17 is AD
It is supplied to the PCM codec section 15 to be ADPCM digital data, and this digital data is sent to the communication control section 14
The data is supplied to the modulation / demodulation unit 13 via the wireless LAN and modulated for transmission, and the modulated data is wirelessly transmitted from the antenna 11 connected to the wireless unit 12.

Further, the key input section 18 is connected to the ADPCM codec section 1 via the man-machine interface section 19.
5, and the operation information of the key input unit 18 is supplied to the communication control unit 14 side. Further, the display unit 20 is connected to the man-machine interface unit 19 so that the operating state and the like are displayed.

Then, the communication control section 14 controls the receiving operation so as to receive only the control signal transmitted from the master unit on a predetermined control channel at a predetermined interval when in the standby state. . In this case, the system call code included in the control signal is discriminated to judge whether or not it is the control signal of the system to which this slave belongs. Further, the control signal transmitted from the master base unit 1 is discriminated by the additional ID transmitted after the system call code, and the control signal is periodically transmitted based on the reception timing of the control signal from the master base unit 1. It is designed to perform intermittent reception. This receiving process will be described later.

When the received control signal is the control signal of the system to which the slave unit belongs, the content of the received control signal is discriminated and the slave unit receives the connection request signal included in the control signal. When it is determined that it has been called, this slave unit is caused to perform the corresponding operation. When each cordless handset is called by this connection request signal, it communicates with the base unit for internal or external telephone calls, and communicates with other cordless handsets for internal telephone calls. There are cases when In addition, when you want to make a call from each cordless handset for an external call or an extension call (extension call with the base unit and call between the handset), use the control channel to send a connection request signal to the base unit. I am sending it.

Next, the configuration of each of the master units 1, 2, and 3 will be described. The master unit 1 of the master and the master units 2 and 3 of the slave have the same configuration and are configured as shown in FIG. That is, as in the case of the slave unit, the wireless unit 32 receives and processes the data received from the slave unit by the antenna 31, supplies the data to the modem unit 33, and demodulates the received data. Then, the demodulated received data is sent to the ADPCM codec unit 3 via the communication control unit 34.
5, the digital data of ADPCM obtained by receiving the data is converted into an analog voice signal, and the analog voice signal is supplied to the line interface section 36 and sent to the analog telephone line connection terminal 37 side.

An analog voice signal obtained from the analog telephone line connection terminal 37 side is supplied to the ADPCM codec unit 15 via the line interface unit 36, and A
The DPCM digital data is supplied to the modulation / demodulation unit 33 via the communication control unit 34 to be modulated for transmission, and the modulated data is wirelessly transmitted from the antenna 31 connected to the wireless unit 32.

Further, the handset 38 is directly connected to the line interface section 36 so that the handset 38 can communicate with the outside line side through the analog telephone line connection terminal 37 and the connection with the ADPCM codec section 15 side enables the child. It is possible to make extension calls with the machine. Further, the key input unit 39 is connected to the line interface unit 36 so that various controls such as transmission to an outside line can be performed.

Then, in the communication control unit 34 of this base unit,
A dedicated channel (frequency band) prepared for control signal transmission is used to transmit control signals at predetermined intervals, and this control signal is used to call other slave units. In this case, the same system call code is added to the control signal transmitted from each master unit, and the distinction between the master and the slave is notified by the additional ID transmitted following the system call code.

Then, the communication control units 34 of the slave master units 2 and 3 are controlled so as to receive the control signal transmitted from the master master unit 1. That is, the control signal including the system call code to which the master ID is added is received and determined. Then, in synchronization with the timing of receiving the control signal from the master, the control signals are periodically transmitted from the master units 2 and 3 of the respective slaves.
It is controlled by the communication control unit 34. In this case, the master units 2 and 3 of the respective slaves are synchronized with each other based on the timing of receiving the preamble as the synchronization data which is the first signal transmitted as the control signal.

Next, each master unit 1, 2, 3 having such a configuration
An example of the state in which the control signal is transmitted from the master unit 1 of the master unit 1 in which each slave unit is in the standby state
The transmission is performed in the state shown in A of FIG. That is,
The transmission of the control signal once for 625 μs is continuously performed at a cycle of 125 ms. The period in which the waveform of A in FIG. 10 rises is the period in which the control signal is transmitted.

The slave master units 2 and 3 receive the control signal transmitted from the master master unit 1 and transmit the control signal in synchronization with the reception timing. Here, the control signal is transmitted from the second master unit 2 after 5 m seconds from the start of receiving the master control signal (see B in FIG. 10) and 10 m.
The control signal is transmitted from the third master unit 3 after a second (see C in FIG. 10). Therefore, [10 ms + 625
μsec], control signals are continuously transmitted from the three master units 1, 2, and 3.

In each of the slave units 4, 5, ... In the standby state, the power supply of the receiving section (the wireless section 12 or the like) is turned on only at the transmission timing when this series of control signals is continuously transmitted. It is turned on periodically. Here, as shown in D of FIG. 10, a period T _{ON in which} the transmission of the control signal from the third master unit 3 ends after the transmission of the control signal from the first (master) master unit 1 is started. Just turn on the power of the receiver. However, since it actually takes some time (for example, 25 μs) for the receiving unit to start up,
The time to turn on T _ON is the time [10 msec + 62
5 μsec], plus a rise time of about 25 μsec.

In order to perform such control in each slave unit 4, 5, ..., Each slave unit 4, 5, ... Detects the timing when the control signal transmitted from the master unit 1 is received. Then, the signal is intermittently received for the period T _{ON based} on this timing. Then, the reception of this period T _ON is intermittently performed in a predetermined cycle. As a period for performing the intermittent reception of the period T _{ON, since} the period for transmitting the control signal is 125 msec, it may be an integral multiple of this 125 msec. For example,
When the same control signal is repeatedly transmitted from each of the parent devices 1, 2, and 3 for 1.5 seconds, the reception cycle of this child device may be set to 1.5 seconds. .

By performing the communication control in this way, the timing of intermittent reception in the standby state in the slave unit can be made substantially the same as in the case of one master unit, even if there are multiple master units. It is possible to reduce the power consumption of the slave unit in the standby state.

[0027]

By the way, in a digital cordless telephone apparatus having a plurality of base units for which such communication control is performed, the master base unit 1 transmits a control signal to the slave base units 2, 2. If 3 cannot be received, each master cannot send a control signal in synchronization with each other, so that each master can be installed only within a range where direct wireless communication can be performed. Therefore, even if a plurality of parent devices are provided, the range that can be used as a cordless telephone system is not expanded.

In the case of a cordless telephone, the transmission output is limited and the transmission output cannot be increased just because the distance between the base units is large. In addition, by connecting each base unit directly with a signal line and transmitting a control signal via this signal line, it is possible to increase the distance between the base units. It is forbidden to provide an antenna terminal and a terminal for inputting and outputting a control signal, etc., and cannot be directly connected.

In view of the above point, the present invention has an object to make it possible to transmit a signal in a relatively long distance in a communication device such as a digital cordless telephone when a direct connection cannot be established.

[0030]

The present invention relates to a wireless communication system for performing wireless communication between antennas 1a and 2a provided in two or more communication devices 1 and 2 as shown in FIG. 1, for example. , Near each antenna 1a, 2a,
The relay antennas 51 and 52 are provided, and the relay antennas 51 and 52 are connected by the coaxial cable 53.

Further, in this case, as shown in FIG. 2, for example, as one communication device, one master communication device 1 is used.
And two or more slave communication devices 2 and 3, and a relay antenna 61 installed near the slave communication device 1 includes a duplexer 64 and coaxial cables 65 and 66.
The wireless signal from the master communication device 1 is connected to the other relay antennas 62 and 63 via 67.
The relay antenna and the coaxial cable are relayed so that the data can be transmitted to each of the slave communication devices 2 and 3.

Further, in this case, it is composed of a plurality of masters and slaves, and the masters and slaves transmit and receive digital data to talk with each other and to communicate with each master. A common system call code is set so that each master unit of a digital cordless telephone device that enables communication between all master units and slave units is used as a communication device, and synchronization is established between each master unit. The control data is transmitted by the relay antenna and the coaxial cable.

[0033]

According to the present invention, a relay antenna connected by a coaxial cable is used to relay communication between a plurality of communication devices, so that even if a plurality of communication devices cannot be directly wirelessly transmitted, a plurality of communication devices can be used. It becomes possible to communicate with the communication device.

In this case, since the signal relayed by the relay antenna is demultiplexed by the demultiplexer and transmitted from the master communication device to the plurality of slave communication devices, a plurality of slave devices are simultaneously transmitted. Can be relayed to other communication devices.

Further, by applying to the transmission of control data between a plurality of parent devices of the digital cordless telephone device, as in the case where the plurality of parent devices are installed apart from each other, a plurality of parent devices can be connected to each other. Even if there is a failure in the direct wireless transmission of the same, it can be used as a digital cordless telephone device of the same system.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. In FIG. 1, FIG. 3 described in the conventional example
The parts corresponding to those in FIG. 10 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this example, a TD having a plurality of parent devices
It is applied to a MA / TDD system digital cordless telephone system and is configured as shown in FIG. That is, in this example, a digital cordless telephone system having two base units 1 and 2 is used, where the base unit 1 is a master base unit and the base unit 2 is a slave base unit. In this case, a common system call code is set for the master devices 1 and 2, and the distinction between the master and the slave is indicated by the additional ID of the identification code transmitted as the control signal (see FIG. 7). Each of the base units 1 and 2 is connected to the exchange side by an individual telephone line.

An arbitrary number of slave units 4, 5 ... Which can communicate with any of the master units 1 and 2 are prepared.

In the case of this example, the master base unit 1 and the slave base unit 2 are installed at relatively distant locations. Then, the relay antenna 51 is installed in the vicinity of the transmission / reception antenna 1a of the master unit 1. Further, a relay antenna 52 is installed near the transmission / reception antenna 2a of the slave master device 2. Then, each relay antenna 51, 5
2 are connected by a coaxial cable 53. The coaxial cable 53 has a central conductor shielded so that a signal received by one relay antenna 51 can be efficiently transmitted to the other relay antenna 52.

Other parts are shown in FIGS. 5 to 1 as a conventional example.
The configuration is similar to that of the digital cordless telephone system described in 0.

According to the digital cordless telephone system of the present embodiment thus configured, even if the master base unit 1 and the slave base unit 2 are installed at relatively distant places, the master base unit 1 and the slave base unit Communication can be performed with the master unit 2, and the master units 1 and 2 can be operated in synchronization with each other. That is, the control signal output from the transmission / reception antenna 1a of the master base unit 1 is received by the relay antenna 51 installed in the vicinity of the transmission / reception antenna 1a, passes through the coaxial cable 53, and is transmitted from the relay antenna 52. Is emitted. Then, the slave master unit 2 can receive the control signal received by the transmission / reception antenna 2a of the slave master unit 2 near the relay antenna 52 and output from the master master unit 1. By relaying and transmitting using the relay antennas 51 and 52 and the coaxial cable 53 as described above, a parent used as the same system as compared with the case where direct wireless transmission is performed between the parent devices 1 and 2. The distance between the machines 1 and 2 can be increased. Alternatively, even when the base unit 1 and the base unit 2 are installed in different rooms or floors and there is an obstacle such as a wall that shields radio waves, the base unit 1 and the base unit 2 are treated as the same system. You can use it.

Here, it will be explained that the transmission relayed by using the relay antennas 51 and 52 and the coaxial cable 53 is more efficient than the direct wireless transmission between the master units 1 and 2. It is assumed that the distance from the transmission / reception antenna 1a on the device 1 side to the relay antenna 51 is equal to the distance from the transmission / reception antenna 2a on the slave master device 2 side to the relay antenna 52, and the distance is d. , The propagation loss L [dB] of the radio wave of wavelength λ in free space is expressed by the following equation.

[0043]

## EQU1 ## L = 20 log (4πd / λ)

If the frequency used for communication by this digital cordless telephone device is about 2 GHz, the wavelength λ
Is given by the following equation.

[0045]

[Formula 2] λ = 300/2000 = 0.15 [m]

Substituting this wavelength into the formula [1] and setting the distance d between the transmitting / receiving antenna and the relay antenna to 1.2 m, the propagation loss L becomes about 40 [dB].

On the other hand, the power Pr at which the downlink control signal transmitted from the master base unit 1 is input to the slave base unit 2 is
It is shown by the following formula.

[0048]

## EQU00003 ## Pr = Pt-2L-la-lc where Pt is transmission power, la is loss in all antennas, and lc is loss in coaxial cable.

Here, the transmission power Pt is set to 80 [mW] (1
9 dBm), propagation loss L = 40 [dB], antenna loss la = 6 [dB], coaxial cable loss lc
= 10 [dB], the power Pr received by the slave master device 2 is expressed by the following equation.

[0050]

## EQU00004 ## Pr = 19-80-6-10 = -77 [dBm]

Personal Handy Phone System (PH
In the digital cordless telephone device called S), the receiving sensitivity is defined as 16 dBμV (−97 dBm) in the standard, and in this case, there is a margin of about 20 [dB]. Therefore, the control signal transmitted from the master unit 1 of the master can be received by the slave unit 2 of the slave in a perfect state (that is, in the error-free state).

In the above description, the case of transmitting the control signal from the master unit 1 of the master to the master unit 2 of the slave has been described. However, even when other signals are transmitted between the master units 1 and 2, the relay is performed. It goes without saying that the antennas 51, 52 for use and the coaxial cable 53 can be used for relay and transmission. Also,
Depending on the conditions, communication between the master unit and the slave unit may be performed by relay using the relay antennas 51 and 52 and the coaxial cable 53. For example, when there is a slave unit 4 near the master unit 1 of the master and the master unit 1 is in use for an outside line call and wants to make an outside line call from the slave unit 4, the slave unit 4 and the slave unit 2 of the slave unit 2 It is also possible to perform communication with and by relay using the relay antennas 51 and 52 and the coaxial cable 53, and to perform outside line transmission from the slave unit 4 via the slave master unit 2.

Next, a second embodiment of the present invention will be described with reference to FIG. Also in this FIG. 2, FIG. 1 and FIG.
Portions corresponding to those in FIG. 10 are designated by the same reference numerals, and detailed description thereof will be omitted.

Also in the case of this example, a TD having a plurality of parent devices
The present invention is applied to the MA / TDD system digital cordless telephone system, but here, it is assumed that the system uses three parent devices. FIG. 2 is a diagram showing the configuration of the base unit 1.
Is a master master unit, and master unit 2 and master unit 3 are slave master units. A common system call code is set for each master unit 1, 2, and 3, and the master and slave are distinguished by a control signal. It is indicated by the additional ID of the transmitted identification code. The respective base units 1, 2 and 3 are connected to the exchange side by individual telephone lines.

An arbitrary number of slave units (not shown) capable of communicating with any of the master units 1, 2, and 3 are prepared.

A relay antenna 61 is installed near the transmitting / receiving antenna 1a of the master unit 1 of the master, and the transmitting / receiving antennas 2 of the master units 2 and 3 of the slaves are installed.
Relay antennas 62 and 63 are installed near a and 3a. Then, one ends of the coaxial cables 65, 66, 67 are connected to the relay antennas 61, 62, 63, and the other ends of the coaxial cables 65, 66, 67 are connected to the duplexer 64. The demultiplexer 64 divides the signal transmitted from the relay antenna 61 side through the coaxial cable 65 into the coaxial cables 66 and 67 evenly in half. .

Other parts are shown in FIGS.
The configuration is similar to that of the digital cordless telephone system described in 0.

With this configuration, even when a plurality of slave master units are prepared, the control signals from the master master unit are transmitted to the relay antennas 61, 62 and 63 and the coaxial cable 65 ,. By relaying via 66 and 67, the data can be transmitted to the master units 2 and 3 of each slave. Therefore,
Each master unit 1, 2, 3 can be operated in synchronization,
Similar to the case of the first embodiment described above, there is an effect that the distances between the parent devices 1, 2, 3 used as the same system can be increased.

In the case of the second embodiment, since the demultiplexer 64 demultiplexes, there is a loss due to demultiplexing.
When the / 2 demultiplexing is performed, the loss due to the demultiplexing is about 6
Since it is dB, the received power at each of the slave units 2 and 3 of each slave is about 3d from the value -77 [dBm] shown in the formula [4].
However, when the reception sensitivity is 16 dBμV (-97 dBm), there is still a sufficient margin and transmission can be performed in a good state.

In the second embodiment, the demultiplexer is used to demultiplex into two systems, but it may be demultiplexed into three or more systems.

Further, in each of the above-described embodiments, the communication between the base units of the digital cordless telephone system is relayed, but the relay between the communication devices for other purposes is the same as the above-mentioned relay antenna and the same. You may make it use a coaxial cable.

[0062]

According to the present invention, when a relay antenna connected by a coaxial cable is used to relay communication between a plurality of communication devices, direct wireless transmission between the plurality of communication devices cannot be performed. However, it becomes possible to communicate with a plurality of communication devices, which is suitable when the distance is large or when there is an object that blocks radio waves between the communication devices.

In this case, since the signal relayed by the relay antenna is demultiplexed by the demultiplexer and transmitted from the master communication device to the plurality of slave communication devices, a plurality of slave devices are simultaneously transmitted. The present invention can be applied to a large-scale communication system having a plurality of slave communication devices.

Further, by applying to the transmission of control data between a plurality of base units of the digital cordless telephone device, the plurality of base units can be separated from each other as in the case where the plurality of base units are installed separately. Even if there is a failure in the direct wireless transmission of the same, it can be used as a digital cordless telephone device of the same system.

[Brief description of drawings]

FIG. 1 is a system configuration diagram according to a first embodiment of the present invention.

FIG. 2 is a system configuration diagram according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a system configuration of a cordless telephone device.

FIG. 4 is a configuration diagram showing a communication system.

FIG. 5 is a configuration diagram showing a system configuration of a cordless telephone device having a plurality of parent devices.

FIG. 6 is an explanatory diagram showing a configuration example of a control signal.

FIG. 7 is an explanatory diagram showing a configuration example of an identification code.

FIG. 8 is a configuration diagram showing a slave unit of the digital cordless telephone device.

FIG. 9 is a configuration diagram showing a master unit of a digital cordless telephone device.

FIG. 10 is a timing diagram showing a control signal transmission state of a system having a plurality of parent devices.

[Explanation of symbols]

 1 master master unit 2,3 slave master unit 4,5 slave unit 1a, 2a, 3a transmission / reception antenna 51, 52, 61, 62, 63 relay antenna 53, 65, 66, 67 coaxial cable 64 duplexer

Claims (3)

[Claims] 1. In a wireless communication system for performing wireless communication between antennas provided in two or more communication devices, a relay antenna is provided near each antenna, and a coaxial cable is provided between the respective relay antennas. A wireless communication system to connect with. 2. A communication device serving as one master and a communication device serving as two or more slaves are prepared as the communication device, and a relay antenna installed in the vicinity of the slave communication device, By connecting to another relay antenna via a duplexer and a coaxial cable, the wireless signal from the master communication device can be transmitted to each slave communication device by relaying the relay antenna and the coaxial cable. The wireless communication system according to claim 1, wherein. 3. A plurality of base units and a handset unit, which transmits and receives digital data between the base unit and the handset unit to carry out a call and are common to the respective base units. In order to synchronize each master unit with each master unit of the digital cordless telephone device, which has set the system call code of the above, to enable communication between all the above master units and slave units The wireless communication system according to claim 1 or 2, wherein the control data is transmitted by a relay antenna and a coaxial cable.