JPH0568001A - Method for digital mobile communication - Google Patents

Abstract

PURPOSE:To realize the excellent method for digital mobile communication in which synchronization between connected devices is established even when radio communication between the connected device is difficult and no exclusive receiver is needed. CONSTITUTION:An exchange station 1 is provided with a means sending timing information to a connected device, a delay buffer adjusting a communication start time, and a means which detects the timing information returned from connected devices 3a, 3b through communication lines 5a, 5b and controls a delay of the delay buffer based on the result of detection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system composed of a plurality of connecting devices connected to a switching center by a communication line and a plurality of mobile stations communicating in a wireless zone formed by the connecting devices. The present invention relates to a digital mobile communication method.

[0002]

2. Description of the Related Art In a digital mobile communication method having a structure typified by a car telephone system, signals can be transmitted from a plurality of connection positions at the same frequency. In addition, when the channel is switched between the connection devices forming the wireless zone, it is necessary to reduce the instantaneous interruption time. However, since the transmission delay time of the communication line between the switching center and each connection device is different, a synchronization shift occurs between each connection device. Therefore, a technique of synchronizing the transmission timing between the connection devices is used. With conventional technology,
A method is provided in which a dedicated receiver for receiving a signal transmitted from an adjacent connection device is provided and synchronization is established between the connection devices based on the reception timing.

[0003]

However, the above-mentioned conventional method has a drawback that radio communication is difficult and synchronization cannot be established when there is an object such as a radio interference between connecting devices. Also, in order to ensure normal wireless communication, restrictions on the installation location of the connection device become large, and it is not applicable to small-scale systems and low-antenna systems. There was a problem that it was easily affected by the building. Furthermore, there is a problem that it is economically disadvantageous to install a dedicated receiver.

The present invention solves the above-mentioned problems and enables synchronization to be established between connecting devices even when wireless communication between connecting devices is difficult, and requires a dedicated receiver. It is an object of the present invention to provide an excellent digital mobile communication method that does not.

[0005]

In order to solve the above object, the present invention has the following first and second configurations.

In the first configuration, a means for transmitting timing information to the connecting device, a delay buffer for adjusting the signal transmission start time, and timing information returned from the connecting device via the communication line to the exchange. And a means for controlling the delay amount of the delay buffer based on the detection result.

The second configuration is a means for transmitting timing information to the connection device, a delay buffer for adjusting the communication start time, and synchronous phase information transmitted from the connection device via the communication line to the exchange. Means for controlling the delay amount of the delay buffer based on the above, and each of the connection devices, means for receiving a radio wave signal from a mobile station in communication with another adjacent connection device, and this radio wave signal. And a means for detecting the phase difference between the synchronization timing signal included in the above and the synchronization timing signal of its own apparatus, and a means for transmitting the phase information according to the detected phase difference to the exchange.

[0008]

The present invention has the following actions due to the above-mentioned configuration.

In the first configuration, the connection device sends a radio wave signal to the mobile station and returns the received timing information to the exchange station in synchronization with the timing information from the exchange station. The switching center detects the timing information returned from the connection device via the communication line, and controls the delay amount of the delay buffer based on the detection result, thereby establishing frame synchronization in the wireless section. it can.

In the second configuration, the connection device transmits a radio wave signal to the mobile station in synchronization with the timing information from the exchange, and at the same time, from the mobile station communicating with another adjacent connection device. Of the wireless radio wave signal, and transmits the synchronous phase information according to the phase difference between the synchronous timing signal included in the wireless radio wave signal and the synchronous timing signal of the own device to the exchange. The switching center can establish frame synchronization in the wireless section by controlling the delay amount of the delay buffer based on the synchronization phase information transmitted from the connection device via the communication line.

[0011]

1 is a diagram showing the configuration of a first embodiment of the present invention. In FIG. 1, reference numeral 1 is an exchange. There are a plurality of subscriber circuits 2a to 2n in the exchange. For example, the subscriber circuits 2a and 2b accommodate the connection devices 3a and 3b via the communication lines 5a and 5b, respectively. The connection devices 3a and 3b send out radio wave signals synchronized with the exchange,
It constitutes a wireless zone. Mobile stations 4a and 4b are housed in a connection device via a wireless line. The subscriber circuit 2a includes a transmission unit 2a-1, a line interface 2a-2, a reception unit 2a-3, and delay adjustment control means 2a-4.
Composed of. The other subscriber circuits have the same configuration.

Next, the operation of the first embodiment will be described. From the subscriber circuit 2a in the exchange 1, the transmitter 2a
-1 generates a frame, and the line interface 2a-
2. A downlink TCM frame is transmitted as timing information to the connection device 3a via the communication line 5a. The connection device 3a receives a signal from the communication line, sends a radio wave to the wireless zone in synchronization with the signal, and sends an upstream TCM frame to the exchange. This TCM
A frame is a data frame of a time-axis compression direction control transmission system called a ping-pong transmission system. In the subscriber circuit 2a, the receiver 2a-3 receives the TCM frame from the connection device, and the delay adjustment control means 2a-
Notify 4. In the 2a-4 delay adjustment control means, the TCM
The time for the frame to make a round trip in the communication line 5a, that is, the transmission delay amount of the communication line 5a is detected, and the transmission timing of the TCM frame is changed.

FIG. 2 shows a phase synchronization control method in the first embodiment. FIG. 2A shows a subscriber circuit 2
The connection devices 3a, 3b which have transmitted the downlink TCM frames from the a, 2b to the connection devices 3a, 3b all at once and have received this
6 is a timing chart in one TCM frame cycle when an upstream TCM frame is returned from the subscriber to the subscriber circuits 2a and 2b. As shown in this figure, in communication with the connection device 3a having a short communication distance, the round trip transmission delay amount td of the communication line 5a is td = t1. Communication line 5b
The round trip transmission delay amount td is td = t2 (t2> t1). However, this transmission delay amount td includes the response delay time tr of the connection device itself. Since each connection device transmits the radio wave signal in synchronization with the frame synchronization signal of the TCM frame from the exchange, the radio wave signal transmitted by the connection device 3b is lower than the radio wave signal transmitted by the connection device 3a. That is, it is delayed by the time of the difference in the amount of transmission delay in one way, that is, the time of (t2-t1) / 2. Assuming that the difference in communication distance between the connection devices 3a and 3b is 2 km, a difference in transmission delay amount of about 10 μsec, that is, a phase difference occurs.

After the end of one TCM frame period, the next TCM frame starts, so that the downlink data and the uplink data do not collide with each other on the communication line.
Assuming that the signal transmission time of the frame (time from the start of transmission to the end of transmission) is ts and the 1TCM frame period is T0, the transmission delay amount td must satisfy the condition of td <T0 -2ts. Therefore, when the communication distance becomes long, the 1TCM frame period T0 must be made long.

FIG. 2 (b) is a timing chart in which the transmission start time delay is adjusted for each connection device so that the radio wave signal is transmitted in a cycle of half the TCM frame cycle T0. .. The delay adjustment time τ is obtained from τ = T0 / 2-ts-td / 2, and delay adjustment control means 2a-4, 2b-4 (not shown) for the signals sent from the subscriber circuits 2a, 2b. No)
Thus, the timings of the frame synchronization signals of the connection devices 3a and 3b are adjusted by adding delays of τ1 and τ2, respectively.

As described above, according to the first configuration, the delay adjustment control means detects the delay amount of the transmission signal and the reception signal, and adjusts the timing of the frame synchronization signal between each connection device in the system. As a result, the deviation of frame synchronization in the wireless section can be eliminated.

Although the delay adjustment control means is placed in the subscriber circuit in the above embodiment, the delay adjustment control means may be provided in the common part of the exchange to adjust the delay. In this case, the frame of the entire exchange can be synchronized.

However, in the first configuration, in order to detect the transmission delay amount of the communication line itself, it is a condition that the response delay time tr in each connection device is the same.

FIG. 3 is a diagram showing the configuration of the second embodiment of the present invention. In FIG. 3, a plurality of subscriber circuits 2a-2
CPU units 2a-5 to 2n-5 are provided in n. The subscriber circuit 2a accommodates the connecting device 3a via the communication line 5a, and the subscriber circuit 2b accommodates the connecting device 3b via the communication line 5b. The connection device 3a includes a driver / receiver 3a-1, which is connected to the communication line 5a, a reception unit 3a-2 which receives a signal from the exchange, and a wireless transmission / reception unit 3a- which transmits and receives a signal to and from a mobile station via an antenna.
3, a transmission unit 3a-4 for transmitting a signal to the exchange 1, a phase detection unit 3a- for detecting the phase of the radio wave signal from the mobile station
5. Consists of a CPU unit 3a-6 which controls the connection device 3a and exchanges call connection information with the exchange 1, and sends a radio wave signal synchronized with the exchange 1 to form a radio zone. is doing. Although not shown in the figure, the wireless transmission / reception unit 3a-3 includes means for receiving a wireless radio wave signal transmitted from a mobile station communicating with another connection device in an adjacent wireless zone. is doing. The connection device 3b also has the same configuration, and other configurations not shown are the same as those in FIG. 1 and are denoted by the same reference numerals.

Next, the operation of the second embodiment will be described. In the subscriber circuit 2a in the exchange 1, the transmitter 2a-
1 generates a TCM frame, line interface 2
a-2, the downlink TCM frame is transmitted to the connection device 3a via the communication line 5a. The connection device 3a receives the TCM frame from the communication line from the driver / receiver 3a-1.
Also, the reception unit 3a-2 receives the signal, and transmits a radio wave signal to the wireless zone via the wireless transmission / reception unit 3a-3 in synchronization with the TCM frame. The mobile station 4a is present in the wireless zone of the connection device 3a, and the mobile station 4a communicates with the connection device 3a by a radio wave signal to communicate with the other terminal (not shown) via the exchange 1. Communication becomes possible.

Further, the connection device 3a monitors a radio wave signal from the mobile station 4b which is in communication with the connection device 3b forming the adjacent zone during communication with the mobile station 4a. Connection device 3
In the phase detector 3a-5, a compares the timing of the frame synchronization signal, which is the phase of the radio wave signal transmitted by itself, with the timing of the frame synchronization signal, which is the phase of the radio wave signal from the mobile station 4b. Then, the phase difference is detected and phase information is generated. Generally, a mobile station transmits a signal in synchronization with a radio wave signal from the connection device. Therefore, monitoring the phase of the radio signal transmitted from the mobile station 4b is equivalent to monitoring the phase of the radio wave signal transmitted from the connection device 3b. That is, the phase information transmitted from the phase detector 3a-5 is the communication line 5a.
And 5b will represent the difference in transmission delay time.
The phase information from the phase detection unit 3a-5 is the CPU unit 3a-6.
Is supplied to. The CPU unit 3a-6 obtains this phase information, identifies that the adjacent connection device is the connection device 3b, and notifies the exchange 1 of the phase information with the connection device 3b. .. The subscriber circuit 2a of the exchange 1 receives the phase information from the connection device 3a and notifies the common control unit 1a which performs the call connection processing of the information. Common control unit 1a
Then, the phase information from each connection device is received, and the delay adjustment for changing the timing of the transmission signal is instructed to each subscriber circuit from the statistical result so as to suppress the timing deviation with other connection devices. The CPU section 2a-5 of the subscriber circuit 2a which receives the instruction from the common control section 1a controls the delay adjustment control means 2a-4 to delay the transmission reference clock of the transmission section 2a-1.

FIG. 4 shows a phase synchronization control method in the second embodiment. FIG. 4A shows a subscriber circuit 2
TCM from a, 2b to the connection devices 3a, 3b all at once
The connection devices 3a, 3 that have transmitted the frame and received the frame
It is a timing chart in 1 TCM frame period when the upstream TCM frame is returned from subscriber b to subscriber circuits 2a and 2b. As shown in this figure, the difference in the reception time of the TCM frame from the exchange 1 between the connection device 3a having a short communication distance and the connection device 3b having a long communication distance is t (ab). The distance difference between each connection device is 2k
Assuming m, t (ab) has a timing shift of about 10 μsec.

FIG. 4B shows a timing chart in which the transmission timing of the TCM frame is delay-adjusted in the exchange 1 based on the phase information obtained from a plurality of connecting devices. As shown in the figure, τb = τ between the delay times τa and τb in the connection devices 3a and 3b.
There is a relation of at (ab). The timing adjustment time of each connecting device is adjusted so that the signal receiving time of the farthest connecting device and the signal receiving time of the closest connecting device in the system match. Therefore, τa and τb are also determined by the phase information from other connecting devices. , Τn are added to the transmitted signals to adjust the timing of the frame synchronization signals of the connection devices 3a, 3b, ..., 3n.

As described above, according to the second embodiment,
Each connecting device detects the phase difference of the received signal from the exchange 1 with respect to the other connecting devices, and notifies the exchange 1 of the phase information, so that the timing of the connection between each connecting device in the system Is adjusted, it is possible to eliminate the deviation of the frame synchronization signal in the wireless section.

In the second embodiment, the delay adjustment control means is provided in the subscriber circuit. However, the delay adjustment control means is provided in the network section 1b that creates a common clock for the exchange and adjusts the overall delay. Good.

Further, in the second embodiment, as in the first embodiment, the signals to be handled are TCs of the ping-pong transmission system.
Although the M frame is used, in the case of the TCM frame, it is necessary that the response delay time in each connection device is the same. However, in the case of the second embodiment, the phase information from each connection device is the difference in the transmission delay time of each communication line, that is, the difference in the arrival time of the downlink signal from the exchange 1. Is independent of the response delay time in.
Therefore, the signal system to be handled is not limited to the TCM frame, and another transmission system may be used.

[0027]

The present invention has the following effects, as is apparent from the first and second embodiments.

The switching center establishes frame synchronization by detecting the timing information returned from the connection device via the communication line and controlling the delay amount of the signal transmission start time. The receiver is unnecessary, and it has the effect of not changing the installation position of the connection device, the height of the antenna, the surrounding environment, etc.It can also handle cases where adjustment via the mobile station is difficult due to channel interference etc. effective.

Further, each connecting device detects the phase difference of the signal received from the switching center with respect to other connecting devices and notifies the switching center of the phase information, so that the switching center can connect between the connecting devices in the system. Since the timing of the frame synchronization signal is adjusted, there is an effect that the deviation of the frame synchronization in the wireless section can be eliminated regardless of the method of the signal to be transmitted.

[Brief description of drawings]

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

FIG. 2 is a timing chart of signal transmission / reception in FIG.

FIG. 3 is a configuration diagram of a second embodiment of the present invention.

FIG. 4 is a timing chart of signal transmission / reception in FIG.

[Explanation of symbols]

 1 Switching Office 2a to 2n Subscriber Circuit 2a-1 Transmitter 2a-2 Line Interface 2a-3 Receiver 2a-4 Delay Adjustment Control Unit 2a-5 CPU Unit 3a to 3b Connection Device 3a-1 Driver / Receiver 3a-2 Receiver 3a-3 Radio transmitter / receiver 3a-4 Transmitter 3a-5 Phase detector 3a-6 CPU 4a-4b Mobile station 5a-5b Communication line

Claims (3)

[Claims] 1. A digital mobile communication system comprising a switching center, a plurality of connecting devices connected to the switching center via a communication line, and a plurality of mobile stations communicating in a wireless zone formed by the connecting devices. A method, wherein the switching center comprises timing information transfer means for transmitting timing information to the connection device, a delay buffer for adjusting a signal transmission start time, and delay adjustment control means, the delay adjustment control means Is a digital mobile communication method, wherein the delay information of the delay buffer is controlled by detecting the timing information returned from the connection device. 2. A digital mobile communication system having a switching center, a plurality of connecting devices connected to the switching center via communication lines, and a plurality of mobile stations communicating in a wireless zone formed by the connecting devices. In the method, the switching center comprises timing information transfer means for transmitting timing information to the connection device, a delay buffer for adjusting a signal transmission start time, and delay adjustment control means, the connection device being A means for receiving another radio wave signal between the mobile station communicating with another connection device and a phase difference between the frame synchronization timing of the other radio wave signal and the frame synchronization timing of the own device. Means for notifying the exchange of information, wherein the delay adjustment control means detects the phase information transmitted from the connection device and controls the delay amount of the delay buffer. Digital mobile communication method characterized. 3. The digital mobile communication method according to claim 1, wherein the timing information is transmitted through a communication line dedicated to the timing information.