JPH1168649A - Mobile communication system, exchange used for the system and method for controlling synchronization between base stations - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain synchronization between base stations with excellent stability at a reduced cost in a mobile communication system. SOLUTION: A single synchronizing signal generator 15 and a plurality of radio base stations 2-1-2-n are interconnected receptively by channels wherein a synchronizing signal is delivered to the radio base stations 2-1-2-n via the channels. Thus, there is no need for exclusive circuits such as a multiplexer circuit and a multiplexer/demultiplexer circuit, and the synchronizing signal is transmitted to each radio base station through a standard speech communication IF. Thus, the synchronization between the base stations is attained at reduced cost with excellent stability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system for performing TDMA radio communication, a switching device used in this system, and a method for controlling synchronization between base stations, and more particularly to synchronizing TDMA frames between base stations (synchronization between base stations). ) For control technology.

[0002]

2. Description of the Related Art Generally, in a mobile communication system for performing TDMA radio communication, inter-base-station synchronization for synchronizing TDMA frame timing between radio base stations is performed. This inter-base-station synchronization synchronizes TDMA frame timings transmitted by adjacent base stations to prevent collision of transmission data due to frame timing deviation and interference with adjacent slots, so that frequency resources can be used effectively. The technology to do.

[0003] Conventional inter-base station synchronization can be classified into the following two systems depending on the frame timing signal source to be referred to. (1) Radio synchronization: Each radio base station is provided with a radio receiver for receiving a radio signal from a standard radio receiver or a similar radio base station in the vicinity, generates a reference timing signal based on the received signal, and refers to the reference timing signal. A method for synchronizing a TDMA frame timing with a timing signal.

(2) Wire synchronization: A reference timing signal is generated inside a communication control device (exchange) accommodating a radio base station, and is superimposed on a signal on a wire communication path and supplied to each radio base station. Each radio base station demultiplexes the reference timing signal from the received signal, and adds T
Synchronize DMA frame timing.

[0005]

These conventional synchronous systems have the following problems, respectively. (1) Radio synchronization: Since it is necessary to provide a radio receiver for receiving a reference signal for each base station, the cost increases. It cannot be used where reference radio waves cannot be received. Further, when the wireless base station of the reference happens to stop transmitting at the time of performing the synchronization processing or when the state of the wireless communication path is deteriorated, the synchronization processing cannot be performed. Also, in order to avoid such a situation, the reference wireless base station may be switched. However, in this case, the timing of the TDMA frame becomes unstable, and it becomes difficult to provide a stable wireless service.

(2) Wire synchronization: The same reference timing signal can be stably supplied to all the radio base stations accommodated in the switching device, but a multiplexing circuit for superimposing and transmitting the reference timing signal is provided. And a demultiplexing circuit for demultiplexing and extracting the reference timing signal, the applicable communication path and the interface for accommodating the radio base station become special, and a system using a standard communication interface such as an ISDN station line. Not applicable to Further, when a network is constructed with a plurality of switching devices, it is not possible to synchronize between base stations between wireless base stations accommodated in different switching devices.

As described above, in the inter-base station synchronization method applied to the conventional mobile communication system, the use of radio synchronization increases the cost and makes it difficult to ensure the stability and reliability of the reference timing signal. In addition, the use of wired synchronization has a disadvantage that a standard communication IF cannot be used.

The present invention has been made in view of such a point, and realizes a stable wired reference timing signal by realizing a new wired synchronization system that can use a standard communication IF. It is an object of the present invention to provide a mobile communication system capable of supplying power to a station, performing low-cost and highly stable inter-base station synchronization, a switching device used in this system, and an inter-base station synchronization control method. And

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a plurality of radio base stations distributed in a specific area, each of which forms a radio zone in the area;
In a mobile communication system including a plurality of wireless base stations accommodated via a wired line and a switching device connected to an external communication network via a central office line or a dedicated line,
The switching device includes: a synchronization signal generation unit that generates a synchronization signal and transmits the synchronization signal to a communication path; and a connection control unit that connects and disconnects a communication path between the synchronization signal generation unit and each of the wireless base stations. , Each of the radio base stations, a call control means for requesting connection to the synchronization signal generation means, and a synchronization signal received from the synchronization signal generation means via the communication path,
Synchronization control means for synchronizing TDMA frame timing for transmission and reception of a radio signal.

In this mobile communication system, in response to a connection request from the radio base station, a communication path between the requesting radio base station and the synchronization signal generating means is connected, and synchronization is performed via the communication path. The signal is delivered to the radio base station. By distributing the synchronization signal using the communication path in this way,
There is no need to provide a dedicated circuit such as a multiplexing circuit or a demultiplexing circuit, and a highly reliable synchronization signal can be transmitted to each wireless base station using a standard communication IF for a call. Therefore, it is possible to perform low-cost and highly stable inter-base-station synchronization.

Further, instead of providing the synchronization signal generating means in the switching device, the synchronization signal generating means can be realized as one communication terminal accommodated in the switching device via a wired line.

According to this configuration, the synchronization signal generating means, which is an external terminal of the switching device, and each radio base station are connected via a communication path, so that a network is constructed by a plurality of switching devices. Even so, for example, by controlling connection of a communication path across switching apparatuses, it becomes possible to distribute a synchronization signal from a single synchronization signal generation unit to each of the radio base stations accommodated in different switching apparatuses. Therefore, stable inter-base-station synchronization can be achieved even between wireless base stations accommodated in different switching devices.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a mobile communication system according to a first embodiment of the present invention. Here, a private PHS system will be exemplified and a specific configuration thereof will be described.

In FIG. 1, reference numeral 1 denotes an exchange functioning as a PBX of a private PHS system, and a plurality of wireless base stations 2- distributed in a service area of the private PHS system.
1 to 2-n are accommodated via base station connection lines 4-1 to 4-n, respectively. These radio base stations 2-1 to 2-n
Is the PHS within the wireless zone formed by each
It is connected to a plurality of wireless terminals 3-1 to 3-i such as terminals and cordless telephones via wireless channels.

[0015] The access method of this radio channel includes 4
Channel multiplexing multicarrier TDMA (Time Division
Multiple Access) -TDD (Time Division Duplex)
A method or the like is used. In a TDMA frame transmitted / received using this 4-channel multiplex multi-carrier TDMA-TDD system, four slots for transmission and four slots for reception are time-division multiplexed, and one slot for transmission and a corresponding reception slot are used. And one slot constitutes one wireless channel. The frame length of this TDMA frame is 5 ms
The transmission and reception are performed at a period of 200 Hz.

The switching device 1 communicates with the wireless base stations 2-1 to 2-n to which these wireless terminals 3-1 to 3-i are connected in accordance with the outgoing and incoming calls to the wireless terminals 3-1 to 3-i. , To connect to the station 8 connected via the office lines 5-1 to 5-m of the public telephone network and to the radio base stations 2-1 to 2-n. Enable.

As shown in the figure, the switching apparatus 1 includes a central control unit 11, radio base station accommodation interfaces (wireless base station accommodation IFs) 12-1 to 12-1, and a station line accommodation interface (station line accommodation IF). ) 13-1 to 13-j, a communication path switch 14, and a synchronization signal generation device 15. The transmission and reception of the call voice between the devices is performed by call path connection 1
7, and a control signal from the central control unit 11 is sent to other devices via a control bus 18. Each device operates in synchronization with a clock (64 KHz) for network synchronization, and speech voice is transmitted as a PCM data stream having a transmission speed of 64 Kbit / s on the speech path connection 17.

The radio base station accommodating IFs 12-1 to 12-1 are interfaces on the extension side, and are connected to the radio base stations 2-1 to 4-n via base station connection lines 4-1 to 4-n, respectively.
2-n are connected. Wireless base station accommodation IF 12-1
12-1 perform interface operations such as detection of outgoing signals from the radio base stations 2-1 to 2-n and transmission of incoming signals to the radio base stations 2-1 to 2-n, respectively.

The office line accommodating IFs 13-1 to 13-j are interfaces on the outside line side.
It is connected to the station 8 via 1 to 5-m. Office line accommodation I
F13-1 to 13-j are office line interface operations such as detection of an incoming call from the office 8 via office lines 5-1 to 5-m and acquisition of the office lines 5-1 to 5-m and the office 8 at the time of transmission. I do. Further, the office line accommodating IFs 13-1 to 13-j have a function of converting a protocol of a call control signal to be transmitted to the office 8 and a function of transmitting / receiving a signal.

The communication path switch 14 is connected to the office line accommodating IF 13-.
1 to 13-j and the wireless base station accommodating IFs 12-1 to 12-
1 and the connection and release of the respective communication paths of the synchronization signal generation device 15 are performed by a control signal from the central control unit 11.

The synchronizing signal generator 15 is connected to each radio base station 2-
1 to 2-n for generating a synchronization signal serving as a reference for TDMA frame timing. As shown in FIG. 4, a communication path interface (communication path IF) 151, a reference clock generator 152, a synchronization signal generation And a control unit 154. A clock signal is exchanged between the communication path IF 151, the reference clock generator 152, and the synchronization signal generator 153 via the clock connection 155, and a control signal from the control unit 154 is transmitted to the internal control bus 1
56, communication path IF 151, reference clock generator 1
52, and the synchronization signal generator 153.

The communication path IF 151 extracts a clock (PCM highway clock) for network synchronization from the signal waveform received via the communication path connection 17 and sends it to the reference clock generator 152 via the clock connection 155. To send. The frequency of the PCM highway clock is 64 KHz corresponding to the transmission speed of the PCM data transmitted on the communication line connection 17. The communication path IF 151 also receives a synchronization signal for synchronization between base stations, which is received from the synchronization signal generator 153 via the clock connection 155, via the communication path connection 17.
Send up. In this case, the frequency of a synchronization signal serving as a reference for synchronization between base stations is 200 Hz, which is the same as the cycle of a TDMA frame.
A specific bit value of 64 Kbit / s per cycle of Hz
On the data stream. The communication path IF 151 includes a plurality of communication paths, and all of the synchronization signals transmitted to each communication path have the same phase.

The reference clock generator 152 is composed of a PLL, generates a reference clock based on the PCM highway clock from the communication path IF 151, and supplies it to the synchronization signal generator 153 via the clock connection 155. The reference clock is synchronized with the PCM highway clock by dividing the PCM highway clock.
It is generated as a KHz signal.

The synchronizing signal generator 153 is also a kind of PLL, and generates a TDMA frame timing synchronizing signal (2) based on a reference clock supplied from the reference clock generator 152.
00 Hz). This synchronization signal is continuously generated as long as the reference clock is supplied.
The data is transmitted to the communication line connection 17 by 51.

The controller 154 monitors the activation and operation of each device in the synchronization signal generator 15. The central control unit 11 in FIG. 1 controls each unit in the switching device 1. The central control unit 11, in addition to the various control functions related to the switching connection control, transmits a synchronous connection request from the wireless base stations 2-1 to 2-n, and establishes a connection between the requesting wireless base station and the synchronization signal generating device 15. It has a function to connect with an unrestricted digital bearer. Thus, the synchronization signal of the TDMA frame timing is transmitted as unrestricted digital information to the requesting wireless base station via the communication path. Note that the synchronous connection request is a line connection request to the synchronization signal generation device 15 for the purpose of receiving a synchronization signal, and in this example, is realized as, for example, an extension transmission function.

When a synchronous connection request is received from the radio base station 2-2, for example, and the communication paths of the synchronization signal generating device 15 are all in communication, the central control unit 11 sets the communication path switch 14 to ON. FIG. 8 (b) including the requesting wireless base station 2-2 from the two-party connection between the wireless base station 2-1 and the synchronization signal generator 15 as shown in FIG. It has a function to switch to such a three-party (or more) connection. Thereby, even if the synchronization signal generation device 15 is in a call,
A wireless base station that has newly issued a synchronous connection request can be additionally connected, and a synchronous signal can be simultaneously distributed from the synchronous signal generation device 15 to a plurality of wireless base stations.

FIG. 6 shows details of each radio base station.
In FIG. 6, reference numeral 2 denotes a radio base station;
1, a wired line IF 22, a communication path switch 23,
A DMA transmission / reception frame timing generation unit 24 and a radio unit 25 are provided. A communication path between the devices is connected to a communication line connection 26, and a control signal from the control unit 21 is connected to each device via an internal control bus 27.

The wired line IF 22 is connected to the switching device 1 via the base station connection line 4. The wired line IF 22 performs an interface operation such as detection of an incoming signal from the switching device 1 and transmission of an outgoing signal to the switching device 1.

The communication path switch 23 includes a wired line interface (wired line IF) 22, a radio unit 25, a TDM
The respective communication paths with the A transmission / reception frame timing generation unit 24 are connected by a control signal from the base station control unit 21.

The radio unit 25 is connected to a radio terminal such as a PHS via a radio channel by a TDMA-TDD system, and performs radio signal processing for making a call. TDMA-TDD
The transmission / reception timing of T
It is controlled by a timing signal transmitted from the DMA transmission / reception frame timing generation unit 24. An antenna 29 is connected to the wireless unit 25.

FIG. 7 shows the details of the TDMA transmission / reception frame timing generator 24. The TDMA transmission / reception frame timing generation unit 24 includes a communication path signal reception unit 241, a frame timing signal generator 242, a control unit 243,
A phase delay circuit 244 and a phase comparator 245 are provided. The transmission and reception of the timing signal between the respective devices is performed via the timing signal connection 246, and the control signal from the control unit 243 is transmitted to the other devices via the internal control bus 247.

The communication path signal receiving section 241 is connected to the communication path connection 2
, And performs signal conversion from the speech path signal to a timing signal. The timing signal is converted to a phase comparator 24 via an internal timing signal connection 246.
5 is output. Here, in the signal conversion from the communication path signal to the timing signal, a process of extracting a 200 Hz synchronization signal carried from the 64 Kbit / s data stream is performed.

The frame timing signal generator 242 includes:
Generating a TDMA frame timing signal for determining a TDMA frame transmission / reception timing by the radio base station;
It is supplied to the wireless unit 25 via the internal timing signal connection 246 and the timing connection 28. The phase of the TDMA frame timing signal sent to the radio unit 25 is controlled by a control signal output from the control unit 243. The timing signal generated for performing the phase comparison control is also supplied to the phase delay circuit 244 via the internal timing signal connection 246.

The phase delay circuit 244 delays the frame timing signal generated by the frame timing signal generator 242 by a specified time, and
Output to The specified delay time is a variable amount, and the control unit 243 specifies the delay time. The value of the delay time normally set is the signal transmission delay time in the radio base station (the signal delay time from the input end of the wired line interface 22 to the end of the antenna 29 via the TDMA transmission / reception frame timing generation unit 24 and the radio unit 25). ) Is the remainder when the modulo operation is performed at the frame timing period.

The phase comparator 245 is connected to the communication path signal receiving unit 2
The phase difference between the synchronizing signal input from 41 and the frame timing signal received from the phase delay circuit 244 is detected. The detection result of the phase difference is read from the control unit 243.

The control section 243 controls each section of the TDMA transmission / reception frame timing generation section 24 in order to generate a TDMA transmission / reception timing signal. The details of the synchronization processing operation in the TDMA transmission / reception frame timing generation section 24 controlled by the control section 243 will be described later with reference to the flowchart of FIG.

The base station control unit 21 shown in FIG.
It controls each of the circuits. Base station controller 21
Performs synchronization control for synchronization between base stations shown in FIG. 9 at the time of operation start processing, in addition to control functions such as call control relating to connection control between the wireless terminal and the switching device 1 and wireless / wired protocol conversion. The details of the processing are shown below.

The base station controller 21 internally generates a synchronization processing start signal immediately before the start of operation of the base station 2 (S
T2-1). Then, first, in step ST2-2, a synchronous connection request for making a call by the synchronous connection request is issued to the switching device 1. This is the synchronization signal generator 1
This is done by dialing a pre-assigned telephone number to 5. Next, the base station control unit 21
In step ST2-3, a non-response detection timer is set in order to detect a case where the switching device 1 or the synchronous signal generating device 15 does not respond to the synchronous connection request. Then, in step ST2-4, it waits for a response to the synchronous connection request.

When a response is received or every time a predetermined time elapses, the process proceeds to step ST2-5. Base station controller 2
1 determines whether or not a response signal has been received in step ST2-5, and upon reception, proceeds to step ST2-7.
If not received, the process proceeds to step ST2-6. In step ST2-6, the base station control unit 21 determines whether or not the non-response timer has timed out. If not, the base station control unit 21 continues waiting for a response from ST2-4.
If a timeout has occurred, the process proceeds to ST2-16 to perform an end process.

In step ST2-7, the base station control section 21 controls the communication path switch 23 to control the communication path between the line corresponding to the call of the wired line IF 22 and the TDMA transmission / reception frame timing generation section 24. Connecting. Then, in step ST2-8, the non-response detection timer set in ST2-3 is cleared. Thereafter, the base station control unit 21 issues a synchronization processing start request to the TDMA transmission / reception frame timing generation unit 24 in step ST2-9, and sets a synchronization processing completion monitoring timer in step ST2-10.

In step ST2-11, the base station control section 21 waits for reception of a synchronization processing end signal from the TDMA transmission / reception frame timing generation section 24 or elapse of a predetermined time, and then proceeds to step ST2-12. In step ST2-12, the base station control unit 21 determines whether or not a process end signal has been received. If not, the process proceeds to ST2-13, and if so, the process proceeds to ST2-14. In step ST2-13, the base station control unit 21
It is determined whether or not the monitoring completion timer of the synchronization process has timed out.
If no time-out has occurred in step ST2, step ST2-
Then, the process proceeds to step S11 to continue the synchronization processing completion wait.

In step ST2-14, the base station control section 21 clears the monitoring completion timer of the synchronization processing, controls the communication path switch 23 in step ST2-15, and sets the communication path switch connected in step ST2-7. To release. Next, the base station control unit 21 proceeds to step ST2-1.
In step 6, the call is disconnected by the synchronous connection request.

In step ST2-17, the base station control section 21 determines whether or not to reconnect, based on whether or not the synchronous connection has succeeded. If the communication path of the synchronization signal generation device 15 is busy and cannot be connected, the base station control unit 21 repeats the processing from step ST2-2 to perform reconnection. This connection request for reconnection is repeated a predetermined number of times. If the synchronous connection is successful, the base station control unit 21 proceeds to step ST2-18, where it sends a synchronization processing end signal to the operation start processing, and ends the processing (ST2-19).

As described above, the wireless base station 2 issues a synchronous connection request to the switching device 1 in the operation start processing, and the switching device 1 responds to the synchronous connection request of the base station 2 by using the synchronization signal source of the TDMA frame timing signal. A certain synchronization signal generating device 1
5 and the communication path of the base station 2 are connected, and a synchronization signal is supplied to the wireless base station 2 via the communication path. After responding, the radio base station 2 connects the communication path to the TDMA transmission / reception frame timing generation unit 24 and performs a subordinate synchronization process for synchronizing the TDMA frame timing with the synchronization signal from the synchronization signal generation device 15. After the subordinate synchronization processing ends, the call is disconnected, and the synchronization processing ends. All the radio base stations 2-1 to 2-n accommodated in the switching device 1 perform the synchronization processing as described above, so that the synchronization of the TDMA frame is realized between the base stations.

During operation of the radio base station 2,
In order to prevent synchronization deviation, it is preferable that the above-mentioned synchronous connection request is periodically issued at predetermined intervals, for example, once a day, and the dependent synchronization process is executed.

Next, referring to the flowchart of FIG. 10, the synchronization processing operation in TDMA transmission / reception frame timing generation section 24 executed in response to the synchronization processing start request issued in step ST2-9 will be specifically described. explain.

When the control unit 243 of the TDMA transmission / reception frame timing generation unit 24 shown in FIG. 7 receives the synchronization processing start request from the base station control unit 21 (ST1-1), the communication channel signal reception unit 241 sends a synchronization signal reception request signal. And waits for a synchronization signal reception confirmation signal from the communication path signal receiving section 241 (ST1-2). Then, the control unit 243 determines in step S
At T1-3, it is determined whether or not the synchronization signal has been received, and if the reception of the synchronization signal is confirmed, the processing from step ST1-4 is performed. If the reception of the synchronization signal is not confirmed, the processing from step ST1-10 is performed. .

When a synchronization signal is received, the control unit 243
First, a value preset as a delay amount is set in the phase delay circuit 244 (ST1-4). Next, a phase comparison start instruction is transmitted to the phase comparator 245 in step ST1-5. Thereafter, in step ST1-6, the control unit 24
3 reads the phase difference of the phase comparator 245 and determines whether or not the phase difference is 0 in step ST1-7.
If the phase difference is not 0, the control unit 243 proceeds to step S
At T1-8, a phase control signal is transmitted to the frame timing signal generator 242 so as to reduce the phase difference, and the phase control is repeated from step ST1-6. Step ST1-
If it is determined in step 7 that the phase difference is 0, the control unit 243 transmits a phase comparison end instruction signal to the phase comparator 245 in step ST1-9. Thereafter, the control unit 243
Transmits a synchronization signal reception end instruction to the communication path signal receiving section 241 (ST1-10), transmits a synchronization processing end signal to the base station control section 21 (ST1-11), and ends the processing (ST1). -12).

As described above, according to the first embodiment,
A single synchronization signal generator 15 and a plurality of radio base stations 2-1
To 2-n are connected by a communication path, and a synchronization signal is distributed to each of the wireless base stations 2-1 to 2-n via the communication path. By distributing the synchronization signal using the communication path in this way, it is not necessary to provide a dedicated circuit such as a multiplexing circuit or a demultiplexing circuit, and the synchronization signal is transmitted to each wireless communication by a standard communication IF for communication. It can be transmitted to a base station. Therefore, it is possible to perform low-cost and highly stable inter-base-station synchronization.

Next, a second embodiment of the present invention will be described. FIG. 2 shows a configuration example of a mobile communication system according to a second embodiment of the present invention. In the following, the description will focus on the differences from the first embodiment.

In FIG. 2, reference numeral 90 denotes an exchange, which includes a plurality of radio base stations 2- distributed in a service area.
1 to 2-n are accommodated via base station connection lines 4-1 to 4-n, respectively. These radio base stations 2-1 to 2-n
Are connected via a wireless channel to a plurality of wireless terminals 3-1 to 3-i composed of cordless telephones such as PHS terminals, for example, in wireless zones formed by them. This radio channel access method includes a four-channel multiplex multi-carrier TDMA (Time Division Multiple Multiple Access).
Access)-A TDD (Time Division Duplex) method or the like is used. The switching device 90 accommodates the synchronization signal generating device 6 via the ISDN extension connection 7.

The switching device 90 is connected to the wireless terminals 3-1 to 3-i
In accordance with the outgoing and incoming calls to and from the wireless base stations 2-1 to 2-n to which these wireless terminals 3-1 to 3-i are connected, and the office lines 5-1 to 5-m of the public telephone network, Between the connected stations 8 and between the radio base stations 2-1 to 2-n, and between the radio base stations 2-1 to 2-n and the synchronization signal generator 6 accommodated in the switching device 90 Is connected alternatively.

The switching device 90 includes a central control unit 91 and base station accommodation interfaces (base station accommodation IFs) 12-1 to 12-1.
2-1, office line accommodating IFs 13-1 to 13-j, a communication path switch 14, and an ISDN terminal accommodating IF 92. A communication path between these devices is connected by a communication path connection 17, and a control signal from the central control unit 91 is connected by a control bus 18.

The ISDN terminal accommodating IF 92 performs an interface operation such as a terminal having an ISDN interface, in this embodiment, detection of transmission of the synchronization signal generator 6 and transmission of an incoming signal.

The central control section 91 controls each device in the switching device 90. This central control unit 91
Is a function for connecting a communication path between the wireless base station that transmitted the request and the synchronization signal generator 6 in response to a synchronous connection request from each wireless base station, in addition to various control functions related to the switching connection control. have. Further, when the synchronous connection request is received and all the communication paths of the synchronization signal generation device 6 are busy, the transmission signal of the synchronization signal generation device 6 is connected to the plurality of wireless base stations 2 as shown in FIG. Have a connection function.

FIG. 5 shows the details of the synchronizing signal generator 6. The synchronization signal generator 6 is realized as an ISDN terminal, and has a line interface (line IF) 61.
, A reference clock generator 152 and a synchronization signal generator 15
3 and a control unit 62 similar to that of the first embodiment. Clock signal between each device is clock connection 1
At 55, the control signal from the control unit 62 is
6 are connected. The line IF 61 is connected to an ISDN terminal accommodating interface (IS
DN terminal accommodating IF) 92.

The line IF 61 extracts the above-described clock for network synchronization from the signal waveform received via the ISDN extension connection 7, and transmits the same to the reference clock generator 152 via the clock connection 155. The line IF 61
The TDMA frame timing reference signal received from the synchronization signal generator 153 via the clock connection 155 is
The transmission is made to the ISND terminal accommodation IF 92 via the N extension connection 7. The line IF 61 has a plurality of lines, and all TDMA frame timing reference signals transmitted to each line are transmitted in the same phase.

The configurations and operations of the reference clock generator 152 and the synchronization signal generator 153 are the same as those of the first embodiment described with reference to FIG. The control unit 62 monitors the activation and operation of each device in the synchronization signal generation device 6. Also I
It performs connection control as an SDN terminal and control to send a synchronization signal to a line in response to an incoming call.

The configuration and operation of the radio base station 2 will be described first.
The description is omitted because it is the same as that of the first embodiment. In the second embodiment, the switching device 90 responds to a synchronous connection request from each base station by a call between the synchronization signal generator 6 which is a synchronization signal source of the TDMA frame timing signal and the requesting base station. And a synchronization signal is supplied to the wireless base station via the communication path. Each radio base station issues a synchronous connection request to the switching device 90 in the operation start processing, and after responding, connects the communication path to the TDMA transmission / reception frame timing generation unit 24 and performs the subordinate synchronization processing. After the dependent synchronization process ends,
Disconnect the call and end the synchronization process. All the radio base stations 2-1 to 2-n accommodated in the switching device 90 perform the synchronization processing as described above, thereby realizing the synchronization of the TDMA frame between the base stations.

FIG. 3 shows an example in which a plurality of switching units 90-1 to 90-2 are interconnected as a modification of the second embodiment. In this example, the switching device 90-1
And the switching device 90-2 are provided with respective ISDN line accommodating IFs.
The synchronization signal generating device 6 is interconnected via 92-1 and 92-2, and is accommodated in the ISDN terminal accommodating IF 92-k of the switching device 90-2. In this configuration, the plurality of wireless base stations 2-1 to 2-n accommodated in the switching devices 90-1 to 90-2 each issue the above-described synchronous connection request, and are transmitted from the synchronous signal generating device 6 via the communication path. The synchronization processing is performed using the synchronization signal transmitted by the mobile station, so that the TD is established between all the base stations accommodated in the switching devices 90-1 to 90-2.
Synchronization of the MA frame is realized.

[0061]

As described above, according to the present invention, a multiplexing circuit and a demultiplexing circuit can be provided by distributing a synchronization signal from the same signal source to each radio base station in a system via a communication path. Without providing a dedicated circuit such as
The synchronization signal can be transmitted to each wireless base station via a standard communication IF for communication, and it is possible to perform low-cost and stable inter-base-station synchronization.

[Brief description of the drawings]

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

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

FIG. 3 is a block diagram showing an example of another configuration of the mobile communication system of FIG. 2;

FIG. 4 is a diagram showing an example of a specific configuration of a synchronization signal generation device used in the mobile communication system of FIG. 1;

FIG. 5 is a diagram showing an example of a specific configuration of a synchronization signal generator used in the mobile communication system of FIG. 2;

FIG. 6 is a diagram showing an example of a specific configuration of a wireless base station used in each embodiment.

FIG. 7 is a diagram showing an example of a specific configuration of a TDMA transmission / reception frame timing generation unit provided in the wireless base station of FIG. 6;

FIG. 8 is a diagram showing a state of connection between a synchronization signal generation device and a radio base station in each embodiment.

FIG. 9 is a flowchart showing a processing procedure of a control unit of the wireless base station in each embodiment.

FIG. 10 is a flowchart showing the procedure of TDMA transmission / reception frame timing generation processing in each embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Switching apparatus 11 ... Central control part 12-1 to 12-1 ... Base station accommodation interface (base station accommodation IF) 13-1 to 13-j ... Office line accommodation interface (station line accommodation IF) 14 ... Call path switch DESCRIPTION OF SYMBOLS 15 ... Synchronization signal generation apparatus 151 ... Communication path interface (communication path IF) 152 ... Reference clock generator 153 ... Synchronization signal generator 154 ... Control part 155 ... Clock connection 156 ... Internal control bus 17 ... Communication path connection 18 ... Control bus 2, 2-1 to 2-n wireless base station 21 base station control unit 22 wired line interface (wired line IF) 23 communication path switch 24 TDMA transmission / reception frame timing generation unit 241 communication path signal receiving unit 242 ... frame timing signal generator 243 ... control unit 244 ... phase delay circuit 245 ... phase comparator 246 ... timing No. connection 247 ... Internal control bus 25 ... Wireless unit 26 ... Call path connection 27 ... Control bus 28 ... Timing signal connection 9 ... Antenna 3-1-3-i ... Wireless terminal 4-1-4-n ... Base station connection line 5-1 to 5-m office line 6 synchronization signal generation device 61 line interface (line IF) 62 control unit 7 ISDN extension connection 8 office 90, 90-1, 90-2 switching device 91 Central control unit 92, 92-1 to 92-k ... ISDN terminal accommodation interface

Claims (10)

[Claims] 1. A plurality of radio base stations which are distributed and arranged in a specific area, each of which forms a radio zone in the area, and accommodates the plurality of radio base stations via a wired line, and A mobile communication system including a switching device connected to an external communication network via a line, wherein the switching device generates a synchronization signal and transmits the synchronization signal to a communication path; Connection control means for connecting and disconnecting a communication path with each of the radio base stations, wherein each of the radio base stations requests communication with the synchronization signal generation means; and the communication path And a synchronization control means for synchronizing a TDMA frame timing for transmitting / receiving a radio signal with a synchronization signal received from the synchronization signal generation means via the communication communication system. Beam. 2. A plurality of radio base stations which are distributed and arranged in a specific area, each of which forms a radio zone in the area, a synchronizing signal generating means for generating a synchronizing signal and transmitting the synchronizing signal to a communication path; A mobile communication system including a station and the synchronization signal generation unit via a wired line, and a switching device connected to an external communication network via a station line or a dedicated line; A connection control unit that connects and releases a communication path between the signal generation unit and each of the radio base stations, wherein each of the radio base stations requests a connection to the synchronization signal generation unit; A synchronization control unit for synchronizing a TDMA frame timing for transmitting and receiving a radio signal with a synchronization signal received from the synchronization signal generation unit via the communication path. Mobile communication system that. 3. The mobile station according to claim 1, wherein the synchronization signal generation unit generates a reference signal serving as a reference for generating a TDMA frame timing in the radio base station as the synchronization signal. Communications system. 4. The mobile communication system according to claim 1, wherein said synchronization signal is transmitted as unrestricted digital information from said synchronization signal generation means to said radio base station. 5. The mobile station according to claim 1, wherein said call control means of said radio base station requests connection to said synchronization signal generation means immediately before said radio base station starts operation. Communications system. 6. The mobile communication system according to claim 1, wherein said call control means of said radio base station requests connection to said synchronization signal generation means at predetermined time intervals. 7. The communication control means of the radio base station, wherein the connection request is repeated a predetermined number of times when a communication path of the synchronization signal generating means is busy. Mobile communication system. 8. The connection control means, when the synchronization signal generation means is in a call, additionally connects a requesting radio base station to the connection during the call and transmits the synchronization signal to a plurality of radio base stations. 3. The mobile communication system according to claim 1, wherein the mobile communication system distributes the data to a station. 9. An exchange device accommodating a plurality of wireless base stations via a wired line and being connected to an external communication network via an office line or a dedicated line, wherein a predetermined connection request from each of said wireless base stations is provided. In response to the request, comprising means for connecting a communication path between the requesting wireless base station and a synchronization signal generating means for generating a synchronization signal, wherein each of the wireless base stations is connected via the communication path A switching device for synchronizing a TDMA frame timing with a synchronization signal received from the synchronization signal generation means. 10. A plurality of radio base stations distributed in a specific area and each forming a radio zone in the area,
A method for controlling synchronization between base stations used in a mobile communication system including a plurality of wireless base stations accommodated via a wired line and a switching device connected to an external communication network via a central line or a dedicated line. In response to a predetermined connection request from each of the radio base stations, a call path between the requesting radio base station and a synchronization signal generating means for generating a synchronization signal is connected, Transmitting a synchronizing signal from the synchronizing signal generating means to the radio base station via a channel, and synchronizing TDMA frame timings of the plurality of radio base stations using the synchronizing signal. Control method.