JP2000350246A - Radio telephone call system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio telephone call system by a time-division duple radio equipment with which a wide telephone call area can be easily obtained by switching plural base stations. SOLUTION: A mobile station sends a synchronizing request signal at a specific frequency and a base station receiving it sends an identification response synchronizing signal. The mobile station sends a telephone call switching synchronizing signal including the identification code of a base station having a higher reception level of the identification response synchronizing signal and the base station enters a telephone mode when the identification code included in the telephone call switching synchronizing signal is the code indicating itself or a monitor mode when not. Plural base stations can automatically be switched according to the intensity of an electric field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time-division communication method in which a speech signal is compressed in the time axis and bidirectionally time-division-transmitted to enable a pseudo-duplex communication by a simplex radio. The present invention relates to a duplex wireless device, and more particularly to a time-division duplex wireless communication system for making a call via a plurality of base stations.

[0002]

2. Description of the Related Art Conventionally, a simplex wireless device has
A so-called time-division duplex wireless communication system that enables a pseudo-duplex communication by simply using a channel wireless transmission system is known, and an example thereof can be found in Japanese Patent No. 2765619. .

[0003] The system disclosed in this publication is also called a single frequency simultaneous transmission / reception system. In this communication system, the radio device that has started a call first becomes a calling station first, and performs time division synchronization. A signal (hereinafter, the time-division synchronization signal transmitted by the calling station is referred to as a synchronization A signal) is transmitted, followed by a time-compressed audio signal.

[0004] On the other hand, at this time, when another wireless device in standby (simplex) receives the synchronization A signal, the wireless device is switched from the standby state to a duplex communication operation, and a call is established. . Here, a radio device that is in a duplex communication operation and is not transmitting is called a monitor station, and when this monitor station becomes a communication partner of the calling station and starts transmitting, it is called a called station. .

The called station transmits another time-division synchronization signal in which the pattern of the frame synchronization signal constituting the synchronization A signal is changed (hereinafter, the time-division synchronization signal transmitted by the called station is referred to as a synchronization B signal). ), Followed by a time-compressed audio signal.

The principle of the duplex communication by the time-division duplex transceiver will be described in more detail. As shown in FIG. 4, each of the radio stations A and B includes a time axis compression circuit A1 and B1.
And transmission circuits A2 and B2, changeover switches A3 and B3, reception circuits A4 and B4, and time-axis expansion circuits A5 and B5. In the time axis shown in FIG. As shown in the figure, signals such as audio signals that are temporally continuous are sequentially converted by time axis compression circuits A1 and B1 for a period (time division cycle) t.
_In the same figure, the time is compressed to the period t ₂ <t _1/2
Create a burst signal as shown in (c).

Then, this burst signal is transmitted to a transmission circuit A
2, and B2, so as to transmit from one to the other in each period t ₁ by the change-over switch A3, B3, thereby period t
_By setting the period t ₂ <t _1/2 created in _{1 as} the reception period of the signal from the other party, a pseudo two-way simultaneous transmission and reception under a carrier signal of a single frequency f ₁ , that is, ,
This makes it possible to perform a pseudo duplicate call.

As shown in FIG. 6, a burst signal to be actually transmitted in this system is transmitted from a bit synchronization and a frame synchronization to the beginning of an audio signal time-compressed in a period t ₂ using an MSK system modem or the like. A time-division synchronization signal (synchronization A signal or synchronization B signal) is added to form a frame and then transmitted.

[0009] As described above, the pattern of the frame synchronization signal constituting the synchronization A signal is changed in synchronization B.
Signal, and the synchronization A signal and the synchronization B signal are both
Subcarrier is M by bit synchronization signal and frame synchronization signal.
It is customary to construct the signal by SK (Minimum Shift Keying) modulation.

[0010] Here, the bit synchronization signal is composed of a signal in which 1 and 0 are repeated several times to several tens of times, and is a signal for establishing bit synchronization in MSK demodulation. This signal is composed of a random pseudo-noise (PN) code having a specific pattern of several bits, and is used for time-division timing and time expansion timing of a time-compressed audio signal.

[0011] Then, in the radio equipment on the receiving side, the synchronizing signal is identified from the burst signal received by the receiving circuit A4 or B4, and the time-compressed audio signal following the synchronizing signal is taken out. By B5, FIG.
As shown in (d), the extended signal which has been compressed in the period t ₂ to time t _1, is adapted to reproduce temporally consecutive original speech signal.

Here, the role of the synchronization signal will be described below. Identify the head position of time-compressed audio signals to smooth the joints of audio signals during playback. Synchronization necessary for switching operation between transmission and reception between opposing wireless devices must be achieved.

Next, the actual time distribution of the time compression / expansion will be described. In _one example, the period t ₁ is about 375.
In ms, the time compression ratio, t ₂ / t _{1, is set} to 1 / 2.2, and the gap time caused by setting the compression ratio to more than 、 corresponds to the synchronization signal and the transmission rise of the transmission circuit. The necessary time and the time for switching from transmission to reception by the changeover switch are embedded, and are _１ ／ of the period t ₁ , that is, 18
7.5 ms are allocated so as to be approximately the transmission period and the reception period, respectively.

Therefore, in a system using such a time division duplex radio, the calling station and the called station each divide one cycle of the time division into half, and transmit and receive the time division synchronization signal and the voice signal. Therefore, as is clear from FIG. 6, if the time-division synchronization signal becomes longer, the time allocated to the audio signal decreases accordingly, and it is necessary to increase the time compression ratio of the audio signal. This leads to a decrease in call quality.

Therefore, in order to prevent the deterioration of the sound quality, the prior art usually uses three points from the viewpoint of preventing malfunction due to noise.
The pattern of the frame synchronization signal of the time-division synchronization signal that requires one bit is reduced to, for example, 16 bits.

According to experiments, when the frame synchronization signal is 16 bits, a malfunction due to noise occurs about once every 60 seconds. As a result, even if the calling station does not exist, Regardless, a situation occurs in which the simplex station is switched to the monitor station due to noise.

In order to prevent such a situation from occurring, in the prior art, for example, when a time-division synchronization signal is received twice consecutively, switching to the monitor station is performed for the first time. Take measures such as returning to a simplex station when the state of non-reception exceeds a predetermined duplex holding time, thereby suppressing the malfunction rate at a rate of about once every 45 times. Have to be able to.

On the other hand, a selective calling function is required, and in order to maintain compatibility, a format shown in FIG. 6D in which a part of bit synchronization is replaced with a selection code is also employed.

By the way, a type of wireless telephone system having a plurality of base stations is a cellular system (car telephone system or portable telephone system). In this system, when the position of a mobile station changes during a call, The call is maintained by switching the call channel with the base station of the call partner.

At this time, in the analog type cellular system, a method of switching between the base station and the communication channel by monitoring the electric field strength of the communication channel transmitted by the mobile station in the surrounding base station has been adopted. With the reduction in size, an increase in the number of cells to be monitored in the base station and an increase in the frequency of channel switching have caused a problem of an increase in control load on the base station.

Therefore, time division multiple access (TDMA)
In the cellular system of the system, peripheral base stations sequentially transmit using an empty slot among slots that are time-divided into a transmission (mobile station transmission) slot, a reception (mobile station transmission) slot and an empty slot, and receive this. A mobile station-assisted channel switching method (Mobil assisted handoff) in which a mobile station measures the electric field strength, transmits the measurement result to the base station, and switches between the base station and the communication channel has been used.

In the case of this method, an empty slot is about 20 m
Since the slots are allocated at intervals of s, unless the empty slot is used for another purpose, the interval at which the neighboring base stations can transmit is about (20 × n) ms. (However, n is the number of peripheral base stations) In view of the above, in recent years, even in a radio communication system in which a call is made between a mobile station and a base station by the above-described time division duplex radio system, a plurality of There is an increasing demand for a system that has a base station of the type described above and enables a call to be made in a wide call area.

[0023]

The prior art using the above-described time division duplex radio apparatus does not particularly consider application to a radio communication system having a plurality of base stations. There was a problem with switching.

That is, in recent years, as described above, even when a time-division duplex radio device is used, application to a communication system capable of covering a relatively large communication area by providing a plurality of base stations is provided. As desired, the prior art does not show anything about switching base stations or switching channels with base stations, which causes problems in application.

An object of the present invention is to provide a radio communication system using a time-division duplex radio device in which a wide communication area can be easily obtained by switching a plurality of base stations.

[0026]

SUMMARY OF THE INVENTION It is an object of the present invention to sequentially divide a continuously input audio signal at predetermined time intervals, compress the time for each of the divided periods, and add a time-division synchronization signal. By performing transmission and reception alternately before and after the fixed period, and by time-expanding the time-compressed audio signal based on the time-division synchronization signal, a pseudo-carrier using the same frequency carrier is used. A time-division duplex wireless device for a mobile station in a wireless communication system using a time-division duplex wireless device capable of simultaneous transmission / reception and switching between a plurality of base stations to communicate between a fixed station and a mobile station. Means for replacing the time division synchronization signal with a transmission request synchronization signal at a predetermined frequency and transmitting the transmission request synchronization signal; and when a predetermined identification response synchronization signal is received, transmitting the signal from the received identification response synchronization signal. Base station Separately, means for transmitting the time-division synchronization signal including the identification code representing the base station is provided, and the time-division duplex wireless device of the base station, in response to the reception of the transmission request synchronization signal, Means for transmitting an identification response synchronization signal including the identification data of the own station, and means for switching from the monitor mode to the communication mode when a communication switching synchronization signal including the identification data of the own station is received, The switching of the plurality of base stations is achieved by the automatic response of each base station.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a radio communication system according to the present invention will be described in detail with reference to the illustrated embodiments. First, an example of a wireless communication system to which the present invention is applied will be described with reference to FIG. 2. In this system, a plurality of base stations A and X composed of time-division duplex wireless devices are provided as fixed equipment. Thus, a call service area including a plurality of call areas ZA and ZX is set, and a mobile station M including a time-division duplex wireless device is used in the call service area.

Each of the base stations A and X is commonly connected to the telephone terminal T via the control device C, whereby the mobile station M
At any position within the call service area, the telephone terminal T
, A telephone call with the same duplex as a normal telephone can be made.

At this time, each of the base stations A and X and the mobile station M are all constituted by a radio apparatus of the time division duplex system using radio waves of the same frequency f. With this, a duplex wireless communication can be performed.

When the position of the mobile station M changes between the communication area ZA and the communication area ZX, the communication from one base station to the other base station is automatically performed according to the electric field strength in each area. Is switched, so that even when the mobile station M moves between the plurality of call areas ZA and ZX, the call can be continuously made without interruption.

Next, FIG. 3 shows an example of a time division duplex radio device used in each station in the embodiment of the present invention, which is representative of the device used in the mobile station M. In FIG. 1, reference numeral 1 denotes a microphone, the output of which is connected to a microphone amplifier 2, and the output of the microphone amplifier 2 is connected to a scrambler 3 and an analog switch 4.

First, the output of the scrambler 3 is input to the time companding unit 7, and the compression signal output terminal CA of the time companding unit 7 is connected to a BPF (band-pass filter) 8 and a differentiating circuit 9
Is connected to an IDC (Instantaneous Deviation Control) circuit 6 via an analog switch. On the other hand, the output of the analog switch 4 is directly connected to the IDC circuit 6 via a differentiating circuit 5.

The data output terminal DA of the time compander 7 is connected to the parallel input of the synchronizing signal generator 10, and the synchronous transmission start signal output terminal ST is connected to the synchronous transmission start signal input of the MSK modulator 11. The serial output of the synchronization signal generator 10 is connected to the input of the MSK modulator 11, the output of which is connected to the IDC circuit 6, and the output of the IDC circuit 6 is connected to the FM modulation input of the high-frequency transmitter 12.

The high-frequency output of the high-frequency transmitter 12 is connected to an antenna 13, which is also connected to a high-frequency receiver 14. FM of high frequency receiving unit 14
The demodulated output is the BPF 15, MSK demodulator 16, HPF
(High-pass filter) 17. On the other hand, a squelch signal output of the high frequency receiving unit 14 is connected to a compression squelch signal input of the time companding unit 7 and a squelch signal input of the control unit 18.

First, the output of the BPF 15 is input to the compression signal input terminal CO of the time companding unit 7 via the integrating circuit 19, whereby the signal output expanded by the time compensating unit 7 is output to the descrambler 20. The analog switch 21 is connected to the input of the low-frequency amplifier 22.

The output of the MSK demodulator 16 is connected to the input of the shift register 23 on the input side of the two cascaded shift registers 23 and 24. And
First, the parallel outputs of the shift register 23 are commonly connected to four PN (pseudo noise) code detection units 25 to 28.

Then, the PN code detecting unit 25 uses the TDD
(Time division duplex) Synchronization A signal is detected and PN code detection unit 2
6, a TDD synchronization B signal is detected, a PN code detection unit 27 detects a transmission request synchronization signal, and a PN code detection unit 28 detects an identification response synchronization signal.
The outputs of 28 are the synchronous input terminals TA,
Connected to TB, TC, TD.

Each of the PN code detectors 25 to 28 is an AND gate that outputs a coincidence signal when the parallel output pattern of the shift register 23 matches the pattern of the PN code. , PN code patterns are different. On the other hand, the shift register 24
Are output from the identification data input terminal DI of the time companding section 7
It is connected to the.

Next, the output of the HPF 17 is connected to the input of the low-frequency amplifier 22 via an integrating circuit 29 and an analog switch 30. The output of the low-frequency amplifier 22 is connected to the electronic volume 31 and the receiving amplifier 32. The signal is also output to the receiver 33 via the electronic volume 34 and the speaker 36 via the speaker amplifier 35 in parallel.

The transmission / reception switching input of the high-frequency transmission unit 12 and the high-frequency reception unit 14 includes a transmission / reception switching output terminal SW of the time companding unit 7.
Is connected. As described above, the control unit 18 is connected to the time companding unit 7, and outputs various control signals such as a transmission / reception switching signal and a call / call reception / simplex mode switching signal. The companding unit 7 outputs a synchronization detection signal, a decompressed squelch signal, and response signals to various control signals.

The control unit 18 includes a duplex switch 3
7. A PTT (press-to-talk) switch 38 is connected, and a notification sound output terminal of the control unit 18 is connected to an input of the low-frequency amplification unit 22.

In the apparatus shown in FIG. 3, the parallel output of the shift register 24 is connected to the selection identification signal input terminal DI of the time companding section 7, the control section 18 and the time compensating section 7 are connected.
Other than the point that the control contents are different, the other hardware configuration is almost the same as that of the conventional time-division duplex radio according to the above-mentioned Japanese Patent No. 2765619, so that detailed description of each component is omitted. .

By the way, the above description is for a mobile station, but for a base station, the microphone 1 is only a handset transmitter of the telephone terminal T, and the receiver 33 is also just a handset receiver. The other configuration is the same. Since the telephone line is a two-wire system, the wireless device of each base station actually connects the telephone terminal T via a so-called hybrid circuit that connects the four-wire system and the two-wire system to each other. Will be connected.

Next, the operation of the embodiment of the present invention using the time division duplex radio apparatus will be described. As described above, in this embodiment, the PTT switch 38 is provided, and thus, by the press-to-talk operation, the PTT switch 38 is configured to operate as a simplex system similarly to a general transceiver. Therefore, first, the operation as a simplex station will be described. This is as follows, which is also the same as the prior art.

The FM demodulation output of the high-frequency receiving unit 14 includes an HPF 17 for removing a tone squelch tone and an integrating circuit 2.
9. The signal is output to the low frequency amplifier 22 via the analog switch 30. The output of the low frequency amplifying unit 22 is output to the receiver 33 via the electronic volume 31 and the receiving amplifier 32, and is similarly output to the speaker 38 via the electronic volume 34 and the speaker amplifying unit 36.

The squelch signal output from the high frequency receiving unit 14 controls the analog switch 30 by being delayed by the control unit 18 or the like. When the PTT switch 38 is pressed, the control unit 18 sets the time companding unit 7 to the simplex transmission mode until it is released, switches the transmission / reception switching output terminal SW to transmission, and starts the high-frequency transmission unit 12.

At this time, the time companding section 7 stops the time-compressed audio signal output CA, and the controller 18 sets the analog switch 4 to the passing state, whereby the output of the microphone amplifier 2 is sent to the IDC circuit 6. It is directly input and transmitted from the high-frequency transmission unit 12. Therefore, it is possible to operate as a simplex station as described above.

Next, the operation according to the duplex system of this embodiment will be described. In this embodiment, in the case of the duplex system, there are two types of operation modes: a talk mode and a monitor mode. The call mode is established by a call operation by one station and a call operation performed in response to the call operation. In the simplex mode, a TDD synchronization signal is received and a duplex communication operation is performed. And the monitor mode is entered when returning from the call mode.

Therefore, these modes are basically the same as the above-mentioned prior art, but in this embodiment, a part of the operation contents of the mobile station and the base station in the call mode, and the mobile station and A part of the operation when a call is established between one base station and another base station is in the monitor mode is different from that in the related art.

First, a general monitor mode will be described. When no call is made in the system, all stations including the mobile station M are in the simplex mode, and the mobile station M
When one of the base stations A and X is busy, the remaining base stations are in the monitor mode.

At this time, when returning from the call mode to the monitor mode, in order to prevent a malfunction due to noise, the monitor mode is returned only by receiving once a synchronization signal which does not include a selection code of the own station (described later). It is configured so that there is no.

When the TDD synchronizing signal is inputted from the synchronizing input terminal TA or the synchronizing input terminal TB, the time companding section 7
A selection code is read from the selection identification signal input terminal DI, and when the selection code of the own station is not included, the TDD synchronization signal is received as a timing signal for opening a timing window.

When the TDD synchronizing signal is received again in the same manner as described above, the time companding unit 7 informs the control unit 18 that there is another station in communication, and the control unit 18 sets the time. The companding unit 7 is set to the monitor mode.

Thus, once in the monitor mode,
When the state in which no time division synchronization signal is received continues for a predetermined duplex holding time or more, the time companding section 7 returns to the simplex mode. Then, even during the monitor mode, the sampling and decompression operations of the compressed voice signal and the compressed squelch signal are performed by performing both the calling operation and the incoming call operation described below, so that both the stations in the communication mode can be used. A signal can be received.

Next, the calling operation will be described. To be a calling station, it is necessary that there is no other station on the call or that the base station replaces the base station that has already called, and is therefore shown in FIG. The condition is that various TDD synchronizing signals are not received. These synchronizing signals will be described in detail later, but are detected by the time companding unit 7 and monitored by the control unit 18. Has become.

When the duplex switch 35 is pressed,
The control unit 18 sets the time companding unit 7 to the calling mode and switches to transmission, assuming that there is no feeling of the TDD synchronization signal, whereby the time companding unit 7 switches the transmission / reception switching output terminal. SW is switched to transmission, the high-frequency transmission unit 12 is started, and a series of transmission operations described below is started.

In this series of transmission operations, the time companding unit 7
A bit synchronization signal (a code obtained by repeating 1 and 0), a selection code, and a PN code for the TDD synchronization A signal are transmitted to a data output terminal D.
A, the codes are stored in a shift register in the synchronization signal generator 10, and a synchronous transmission start signal is output to the MSK modulator 11, whereby the synchronization signal generator 10 performs MSK modulation. Sync signal
The operation is output to the high-frequency transmission unit 12 via the IDC circuit 6 and transmitted from the antenna 13.

When the transmission of the TDD synchronization A signal is completed, the time companding section 7 outputs the time-compressed audio signal from the compression signal output terminal CA, and outputs the high-frequency signal through the BPF 8, the differentiation circuit 9, and the IDC circuit 6. Supply to the transmission unit 12,
Send.

When the transmission of the time-compressed audio signal is completed, the time companding section 7 switches the transmission / reception switching output terminal SW to reception, stops the high-frequency transmission section 12, and after a predetermined reception time has elapsed, As long as the control unit 18 does not switch from transmission to reception, the transmission / reception switching output terminal SW is switched to transmission again, the high-frequency transmission unit 12 is started, and the bit synchronization signal
The operation returns to the operation of outputting the selected code and the PN code for the synchronization A signal to the data output terminal.

The time companding section 7 receives the selection identification signal input terminal D at the reception timing of the time division duplex synchronization B signal input to the synchronization input terminal SB during the reception time.
Read the selection code from I and match it with the selection code of the own station,
In addition, only within a predetermined range of timing (hereinafter, referred to as a timing window), by receiving as a TDD synchronization B signal, a selective call is realized and malfunction due to noise is reduced. Here, when the TDD synchronization signal is received, the mode is switched to the call mode.

The time compander 7 starts sampling the time-compressed audio signal output from the integration circuit 19 in synchronization with the TDD synchronization B signal.
Even if the signal cannot be received, sampling of the time-compressed audio signal is started at the center of the timing window.

When receiving the time-compressed audio signal, the time companding unit 7 also samples the compressed squelch signal output from the high-frequency receiving unit 14, and time-expands both the audio signal and the squelch signal. The decompressed audio signal is supplied from a decompression signal output terminal to a descrambler 20, and then input to an analog switch 21.

At this time, since the rise of the squelch signal is delayed with respect to the rise of the carrier, the time companding unit 7 compensates for the rise delay by holding the squelch signal during this delay time along with the elongation of the time axis. Perform, control unit 18
Thus, the control unit 18 receives the expanded squelch signal from the time companding unit 7 and cuts off the expanded audio signal by the analog switch 21.

The audio signal that has passed through the analog switch 21 is output to the receiver 33, while the control unit 18 adjusts the volume of the speaker 36 using the electronic volume 32 in order to prevent howling.

Next, an incoming call operation will be described. In the monitor mode, when the duplex switch 37 or the PTT switch 38 is pressed, the control unit 18 switches the time companding unit 7 to the incoming call operation, whereby the time companding unit 7 reverses the calling operation. The transmission / reception switching output terminal SW is switched to transmission at the timing,
The high-frequency transmission unit 12 is started.

Then, the bit synchronizing signal, the selection code, and the PN code for the TDD synchronizing signal are output from the time companding unit 7 to the data output terminal DA, and stored in the shift register in the synchronizing signal generating unit 10, which is stored in the MSK. Supply to the modulation unit 11,
A synchronous transmission start signal is output, and an MSK-modulated synchronous signal is output from the synchronous signal generator 10 to the high-frequency transmitter 12 via the IDC circuit, and transmitted from the antenna 13.

After completion of the transmission of the TDD synchronizing signal, the time companding section 7 outputs a time-compressed audio signal from the compressed signal output terminal CA instead, and outputs the BPF 8, the differentiating circuit 9,
The signal is supplied to the high-frequency transmitting unit 12 via the DC circuit 6 and transmitted from the antenna 13.

When the transmission of the time-compressed audio signal is completed, the time companding unit 7 switches the transmission / reception switching output terminal SW to reception, stops the high-frequency transmission unit 12, and after a predetermined reception time elapses, performs control. As long as the unit 18 does not switch from transmission to reception, the transmission / reception switching output terminal SW is switched to transmission again, the high-frequency transmission unit 12 is started, and the PN code for the bit synchronization signal, the selection code and the synchronization B signal is output to the data output terminal D.
This is repeated by returning to the operation of outputting to A.

Thus, when the TDD synchronization signal is received from the calling station, the mode shifts to the talking mode. At this time,
The time companding unit 7 limits the reception timing of the synchronization A signal to the timing window during the reception time, thereby reducing malfunction due to noise.

The time companding unit 7 starts sampling the time-compressed voice signal transmitted by the calling station in synchronization with the time-division duplex synchronous A signal. Even at the center of the timing window, sampling of the time-compressed voice signal transmitted by the calling station is started.

When receiving the time-compressed audio signal, the time companding section 7 also samples the compressed squelch signal to extend the time of both the audio signal and the squelch signal. The expanded audio signal is output to an expansion signal output terminal, and is input to an analog switch 21 via a descrambler 20.

Here, the rise of the squelch signal is delayed with respect to the rise of the carrier. Therefore, the time companding unit 7 compensates for the rise delay by holding the squelch signal during the delay and elongates the time axis, and outputs the result to the control unit 18.

The control unit 18 receives the expanded squelch signal from the time companding unit 7 and cuts off the expanded audio signal by the analog switch 21. The audio signal that has passed through the analog switch 21 is output to the receiver 31, and the output of the speaker is controlled by the electronic volume 32 to the lowest volume by the electronic volume 32 in order to prevent howling.

Hereinafter, the specific operation of the base station and the mobile station will be described. These are the same for both the calling operation and the incoming call operation.
In the base stations A and X, when the PN detection unit 27 detects the transmission request synchronization signal via the synchronization input terminal TC of the time expansion / compression unit 7, the control unit 18 inputs the transmission request synchronization signal, thereby It requests the expansion unit 7 to transmit the identification response synchronization signal.

The time companding unit 7 that has received the request for transmission of the identification response synchronization signal from the control unit 18 transmits the identification response synchronization signal at the same timing as when the next TDD synchronization signal is transmitted. The high-frequency transmission unit 12 is started.

Then, the bit synchronizing signal, the identification code and the PN code for the identification response synchronizing signal are output to the data output terminal DA, and are thereby stored in the shift register in the synchronizing signal generator 10 and synchronized with the MSK modulator 11. By outputting the transmission start signal, the MSK-modulated identification response synchronization signal is output from the synchronization signal generation unit 10 to the high frequency transmission unit 12 via the IDC circuit 6, and transmitted from the antenna 13.

When the transmission of the identification response signal is completed, the transmission is stopped after transmitting the time-compressed voice signal in the case of the call receiving operation as described above, and the transmission is immediately stopped in the monitor mode.

In the base stations A and X, the time companding section 7 ignores the identification response synchronization signal (described later) input from the synchronization input terminal TD and does not receive it.

On the other hand, in the mobile station M, the time companding unit 7 sets the reception timing of the identification response synchronization signal (described later) input from the synchronization input terminal TD to the timing window in the same manner as the TDD synchronization signal. By limiting, malfunctions due to noise are reduced.

Next, a specific operation in the call mode and the monitor mode in this embodiment will be described with reference to FIG. In FIG. 1 as well, the TDD synchronization signal on the calling side becomes the TDD synchronization A signal and the TDD synchronization B signal on the called side is the same as in the prior art.

First, the control unit 18 of the mobile station M not only repeats the above series of transmission operations in the call mode,
For each predetermined number of times, the PN for the TDD synchronization signal is
The time compander 7 is controlled so that the PN code for the transmission request synchronization signal is output to the data output terminal TA instead of the code. Accordingly, as shown in FIG. 1 (a), the mobile station M outputs a normal T from the mobile station M at a predetermined frequency, for example, every three seconds.
The transmission request synchronization signal is transmitted instead of the DD synchronization signal.

At the same time, the control unit 18 of the mobile station M
Is a timing at which the next TDD synchronization signal is transmitted after the transmission request synchronization signal is transmitted, and a PN code for a call switching synchronization signal is output to the data output terminal DA instead of the normal TDD synchronization signal. The time compander 7 is controlled as described above. Accordingly, as shown in FIG. 1 (a), the mobile station M also transmits a call switching synchronization signal at a predetermined frequency, that is, every three seconds, replacing the ordinary TDD synchronization signal. Will be.

On the other hand, when the control unit 18 of the base stations A and X enters the call mode, it repeats only the above series of transmission operations. That is, the wireless device of the base station does not transmit the transmission request synchronization signal, and only the wireless device of the mobile station M replaces the transmission request synchronization signal with the TDD synchronization signal at a predetermined frequency, for example, every three seconds, and transmits the signal. .

Thus, the control units 18 of the base stations A and X
When operating in the call mode and in the monitor mode, the PN signal is input via the synchronization input terminal TC of the time companding unit 7.
The detection of the transmission request synchronization signal from the detection unit 27 is constantly monitored.

Then, when the transmission request synchronization signal is received from the mobile station M, the control unit 18 sets the timing of the reception of the transmission request synchronization signal as shown in FIGS. 1 (b) and (c). Next, the time compander 7 is controlled so that the PN code for the identification response synchronization signal is output to the data output terminal DA at the timing when the TDD synchronization signal is to be transmitted.

Accordingly, first, the base stations A, X
From among the stations operating in the call mode, a normal TD to be transmitted at this timing is transmitted as shown in FIG.
The identification response synchronization signal is transmitted in place of the D synchronization signal, and the station in the monitor mode transmits a normal TDD synchronization signal from another base station as shown in FIG. 1 (c). Similarly, the identification response synchronization signal is transmitted in synchronization with the timing.

Next, after transmitting the identification response synchronizing signal, the control units 18 of the base stations A and X transmit the call switching synchronization signal from the PN detection unit 28 via the synchronization input terminal TC of the time companding unit 7. The detection of the signal is monitored over a period including the timing when the next TDD synchronization signal should appear.

Then, when the TDD synchronization signal transmitted from the mobile station M is received as a signal R as shown in FIGS. 1B and 1C, the identification data contained therein is checked.
It is determined whether or not it is an identification code representing its own station, and a response is made as follows to this determination result. Here, Y is when the determination result is affirmative, that is, when the identification code indicates the own station, and N is when the determination result is negative, that is, when the identification code indicates another station.

[When the base station is in the call mode] Y → The call mode is held as it is. N → Switches to monitor mode. [When the base station is in monitor mode] Y → Switch to call mode. N → Keep monitor mode.

Here, the contents of each of the above signals are as follows. <Transmission request synchronization signal> A PN code different from a normal TDD synchronization signal and a PN code indicating a transmission request without a selection code. <Identification response synchronization signal> A PN code is different from a normal TDD synchronization signal and an identification response is generated. Signal obtained by adding an identification code representing its own station to a PN code representing

Next, the switching operation of the base station according to this embodiment will be described. In the call mode, when the identification response synchronization signal is detected by the synchronization input input terminal TD, if the time is within the same reception timing timing window as the TDD synchronization signal, the time compander 7 of the mobile station M immediately starts. The identification code is read from the identification signal input terminal DI.

Now, it is assumed that the mobile station M is currently talking in the communication area ZA of the base station A as shown in FIG. That is, the mobile station M and the base station A are in the call mode, and the base station X is in the monitor mode. At this time, the mobile station M receives only the identification response synchronization signal of the base station A among the identification response synchronization signals returned from the base stations A and X in response to the transmission of the transmission request synchronization signal from the mobile station M. Is done.

Therefore, at this time, the TDD synchronization signal transmitted from mobile station M contains the identification code indicating base station A, and thus base station A keeps the talk mode as it is. The base station X will stay in the monitor mode.

Next, assuming that the mobile station M moves as indicated by the arrow and moves between the communication area ZA of the base station A and the communication area ZX of the base station X, the mobile station M Both the identification response synchronization signal of the station A and the identification response synchronization signal of the base station X are received.

At this time, in the time companding unit 7 of the mobile station M, when the identification response synchronization signal is detected by the synchronization input input terminal TD, it is detected within the timing window of the same reception timing as the TDD synchronization signal. If there is, the identification code is immediately read from the identification signal input terminal DI. Therefore, despite the fact that both the identification response synchronization signals are sensed, there is no interference, and the higher signal level, that is, Only the identification response synchronization signal having the higher electric field strength can be read.

In this way, the time companding section 7 of the mobile station M which has detected the identification code of the base station having the strongest electric field strength outputs the bit synchronization signal, the selection code and the TDD synchronization A signal (at the time of calling) to the data output terminal DA. Alternatively, when outputting a PN code for a B signal (at the time of an incoming call), the received base station identification code is output instead of the selection code.

Accordingly, as shown by the arrow in FIG. 2, the mobile station M moves, and the identification response synchronization signal transmitted from a plurality of base stations, that is, the base station A, and the identification response synchronization signal transmitted from the base station X. Even when the synchronization signal is simultaneously received, only the identification code of the identification response synchronization signal transmitted from the base station having the higher electric field strength is always detected by the mobile station M. As a result, the mobile station M Thereafter, the TDD synchronization signal including the identification code of the base station having the higher electric field strength is always transmitted.

Therefore, when the mobile station M is located in the communication area ZA of the base station A as shown in FIG.
The identification code of the base station A is included in the TDD synchronization signal transmitted from the mobile station M. Next, as shown by the arrow in FIG.
X, and when the electric field strength of the identification response synchronization signal transmitted from the base station X becomes higher, the mobile station M
The identification code of the base station X is included in the TDD synchronization signal transmitted from.

At this point, the base station A automatically switches to the monitor mode, and the base station X automatically switches to the talk mode.
Would make a call.

Therefore, according to this embodiment, the base station having the strongest electric field strength is automatically selected, and the switching between the talk mode and the monitor mode is automatically obtained. Can easily have a large call service area.

As a result, according to this embodiment,
Since there is no need to provide an extra empty slot for detecting the electric field strength, there is no possibility that the communication quality will be degraded, and the base station can be easily switched within a short period of three seconds.

[0102]

According to the present invention, the radio wave of the base station having the highest electric field can be detected in a short time, for example, at intervals of 3 seconds without measuring the electric field intensity, that is, without requiring the electric field intensity measuring section. In addition, the communication area of the wireless communication system using the time-division duplex wireless device can be easily expanded without lowering the communication quality.

[Brief description of the drawings]

FIG. 1 is a timing chart for explaining the operation of an embodiment of a wireless communication system according to the present invention.

FIG. 2 is a system configuration diagram for explaining an operation of one embodiment of the present invention.

FIG. 3 is a block diagram illustrating an example of a time division duplex wireless device used in an embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a radio communication system using a time-division duplex radio according to the related art.

FIG. 5 is a timing chart for explaining the operation principle of the time division duplex radio.

FIG. 6 is a timing chart for explaining the operation principle of the time division duplex radio.

[Explanation of symbols]

 Reference Signs List 1 microphone 2 microphone amplifying unit 3 scrambler 4 analog switch 5 differentiating circuit 6 IDC circuit 7 time compressing / expanding unit 8 BPF 9 differentiating circuit 10 synchronization signal generating unit 11 MSK modulating unit 12 high frequency transmitting unit 13 antenna 14 high frequency receiving unit 15 BPF 16 MSK demodulation unit 17 HPF 18 control unit 19 integration circuit 20 descrambler 21 analog switch 22 low frequency amplification unit 23 shift register 24 shift register 25 PN code detection unit for synchronous A signal 26 PN code detection unit for synchronous B signal 27 transmission request signal PN code detector for identification 28 PN code detector for identification response signal 29 Integrating circuit 33 Handset 34 Electronic volume 35 Speaker amplifier 36 Speaker 37 Duplex switch 38 PTT switch

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 5K028 AA15 BB04 CC05 DD01 DD02 FF12 HH02 KK01 KK23 MM08 MM16 NN01 NN05 SS07 SS17 5K047 AA00 BB01 CC02 CC06 DD01 EE01 GG34 HH01 HH17 KK04 MM02 MM11 DDB25 DD0225 DD67 EE16 EE24 JJ71

Claims (1)

[Claims] 1. A continuously input audio signal is sequentially divided at predetermined time intervals, time-compressed for each of the divided periods, and a time-division synchronization signal is added.
Transmission and reception are alternately performed before and after the period, and the time-compressed audio signal is time-expanded based on the time-division synchronization signal, thereby enabling pseudo simultaneous transmission and reception using the same frequency carrier. Using a time division duplex radio device,
In a wireless communication system of a system in which a call is made between a fixed station and a mobile station by switching a plurality of base stations, a transmission request synchronization signal is transmitted at a predetermined frequency to the time-division duplex wireless device of the mobile station. Means for transmitting the received identification response synchronizing signal, identifying a base station which transmitted the signal from the received identification response synchronizing signal, and including an identification code representing the base station. Means for transmitting the time-division synchronization signal, wherein the time-division duplex wireless device of the base station transmits an identification response synchronization signal including the identification code of its own station in response to the reception of the transmission request synchronization signal. Means for transmitting, and a means for switching from a monitor mode to a communication mode when a time-division synchronization signal including an identification code of the own station is received, wherein the switching of the plurality of base stations is automatically performed by each base station. Done by response A wireless communication system characterized by being configured as described above.