JP2001169372A - Synchronous system between private branch exchanges - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a synchronous system between private branch exchanges, that prevents interference by a radio wave. SOLUTION: A private branch exchange 1 transmits a signal (a) in faster timing than a master frame pulse by a prescribed phase difference to a private branch exchange 2. A synchronization device 27 extracts a 5 ms frame pulse from the received slave frame pulse (a). The synchronization device 27 gives the 5 ms frame pulse to a phase synchronization oscillator 22 as a loopback frame pulse (b). The phase synchronization oscillator 22 generates the 5 ms frame head signal synchronously with the received 5 ms frame pulse and transmits it to PHS base station interfaces 24, 29 via PHS base station interfaces 23, 28. When the phase relation between the slave frame pulse (a) and the loopback frame pulse (b) is symmetrical to the master frame pulse, 5 ms frame synchronization is competed between the phase synchronization oscillators 12, 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a synchronization system between private branch exchanges, and more particularly to a synchronization system between private branch exchanges accommodating PHS terminals. More specifically, the present invention relates to a private branch exchange accommodating a PHS (Personal Handy Phone System) terminal, and particularly to a PHS base station accommodated in a different private branch exchange when accommodating a PHS base station using a plurality of private exchanges. To a frame synchronization system for transmitted radio waves.

[0002]

2. Description of the Related Art Generally, a PHS terminal and a private branch exchange have a P
They are connected by digital communication signals via HS base stations. FIG. 4 is a general block diagram showing a configuration of a private branch exchange accommodating a conventional PHS terminal. Referring to FIG. 4, a system including private branch exchanges 1 and 2 accommodating conventional PHS terminals 10, 15, 20, and 25 establishes connection between private branch exchanges 1 and 2 and PHS base stations 14, 19, 24, and 29. It has time-division switches 11 and 21 for switching. Also, a phase-locked oscillator 12, which generates a 5 ms frame (head) of the PHS digital communication signal (corresponding to the head of the digital signal frame), a clock signal, etc.,
22, PHS base station interfaces 13, 18, 23, 2 for connecting to PHS base stations 14, 19, 24, 29
8

Further, PHS terminals 10, 15, 20, 25
And PHS base stations 14 and 1 connected by radio (radio wave)
9, 24, 29, PHS terminal 10, 1 carried by subscriber
5, 20 and 25, and private branch exchanges 1 and 2 are configured to have trunks 16 and 26 for connection including trunk lines.

In the conventional private branch exchanges 1 and 2 shown in FIG. 4, 5 ms generated by the phase locked oscillators 12 and 22 are used.
The frame (head) signal is transmitted to the time division switches 11 and 21.
Via the PHS base station interface (I / F) 1
3, 18, 23, 28. The PHS base station interfaces 13, 18, 23, and 28 are inserted on a (digital) S (signal) interface frame and transmitted to the PHS base stations 14, 19, 24, and 29. At the PHS base stations 14, 19, 24 and 29,
Radio waves are transmitted in synchronization with the received 5 ms frame head signal.

[0005] Also in the conventional private branch exchanges 1 and 2, the 5 ms frame head signal supplied to a certain private branch exchange, for example, 1 is synchronized. That is, for example, since the 5 ms frame head signals supplied to the PHS base station interfaces 13 and 18 accommodated in the private branch exchange 1 are synchronized, the PHS base station 14 connected to the PHS base station interfaces 13 and 18 is synchronized. , 19 are also synchronized.

Similarly, for example, the PHS in the private branch exchange 2
The radio waves transmitted by the base stations 24 and 29 are also synchronized, and can be placed when the PHS base stations 14 and 19 are installed adjacent to each other or when the PHS base stations 24 and 29 are installed adjacent to each other. No radio interference occurs. That is, when the PHS terminal is accommodated in one private branch exchange as described above, interference of radio waves does not occur even if the PHS base station is installed adjacent to the PHS terminal.

[0007]

However, in such a conventional system, it is assumed that, for example, a plurality of private branch exchanges are installed between adjacent buildings, or a plurality of private branch exchanges are installed in a large site. In such a case, if PHS base stations accommodated in different private branch exchanges are installed adjacent to each other to cover the communication area of the PHS terminal, 5 ms between each private branch exchange accommodating the PHS base station is required. Since the frame head signal is not synchronized, 5 ms (frame) synchronization between adjacent PHS base stations cannot be achieved. Therefore, radio waves are transmitted in an asynchronous state between PHS base stations accommodated in different private branch exchanges located adjacent to each other, and radio wave interference occurs, so that voice signals or data are not transmitted and received normally.

Japanese Patent Application Laid-Open No. Hei 8-237731 discloses a PHS carrier station exchange and a private branch exchange.
There has been proposed a method of connecting to a base station concentrator and delaying each signal in a buffer unit therein to achieve frame synchronization. However, when a plurality of private branch exchanges are installed, the circuit configurations of the PHS base station concentrator and the base station increase, and the device configuration becomes complicated. In a switching system, it is not practical in terms of cost.

An object of the present invention is to provide a synchronization system between private branch exchanges which prevents interference by radio waves. That is, it is assumed that a plurality of private branch exchanges accommodating PHS terminals are installed, and PHS base stations accommodated in different private branch exchanges are installed adjacently to cover a communication area. In this case, it is an object of the present invention to provide a simple device capable of preventing interference by radio waves from another adjacent base station between a plurality of private branch exchanges accommodating the PHS terminal.

[0010]

SUMMARY OF THE INVENTION A private branch exchange synchronization system according to the present invention is a private branch exchange synchronization system for synchronizing frames between private branch exchanges constituting a master station accommodating a personal handyphone system terminal and a subordinate station. A slave station frame pulse generating means for generating a slave station frame pulse for determining a frame phase of a digital signal of the own station synchronized with a slave frame pulse transmitted from the master station; Loop-back frame pulse transmitting means for sending back the slave frame pulse transmitted from the station as a loop-back frame pulse to the main station, phase advance means for advancing the phase of the slave frame pulse to the main station, and the slave frame pulse. Master station frame pal that determines the frame phase of its own digital signal Phase control means for controlling the phase advance means such that the phase difference between the master station frame pulse and the loop back frame pulse returned from the slave station is equal to the phase difference between the master station frame pulse and the slave station. I do.

The phase difference between the slave frame pulse and the master station frame pulse or the phase difference between the master station frame pulse and the loopback frame pulse returned from the slave station is determined by the master station and the master station. It is characterized by being equal to the signal transmission time with the dependent station.

The operation of the present invention is as follows. A plurality of private branch exchanges accommodating PHS terminals face each other with a 5 ms synchronizer for supplying a 5 ms frame pulse between the private branch exchanges, one private branch exchange as a main station, the other private branch exchange as a subordinate station, And a function for achieving 5 ms synchronization between the slave stations. That is, the private branch exchange that is the main station has a PH
A phase locked oscillator for generating a 5 ms frame head signal to be transmitted to the S base station,
It has a PHS base station interface for transmitting an s frame head signal and a 5 ms synchronizer.

The 5 ms synchronizer includes a slave frame pulse generating section for generating a signal to be transmitted to the dependent station, and a 5 ms frame pulse extracting section for extracting a 5 ms frame pulse from the signal returned from the dependent station. Have. Further, it has a phase comparator for detecting a phase difference between the signal returned from the dependent station and the signal transmitted by itself, and transmitting a signal corrected for the detected phase difference to the slave frame pulse generator.

Further, the private branch exchange, which is a subordinate station,
It has a 5ms synchronizer opposite the 5ms synchronizer. Furthermore, the 5 ms synchronizer includes a 5 ms frame pulse extraction unit that extracts a 5 ms frame pulse from a slave frame pulse received from the main station, and a 5 ms frame pulse transmitting unit that sends out the extracted 5 ms frame pulse to its own phase locked oscillator.
and an s-frame pulse transmitting unit. A loopback control unit for returning the slave frame pulse received from the master station to the master station side, and synchronizing the 5 ms frame pulse received with the 5 ms frame pulse received from the own station's 5 ms synchronizing device. Generate

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of a private branch exchange synchronization system according to the present invention, and the same parts as those in FIG. Referring to FIG. 1, a private branch exchange synchronization system according to the present invention includes a private branch exchanges 1, 2 and 1,
It has time division switches 11 and 21 for switching connections with the base stations 14, 19, 24 and 29. Also, phase-locked oscillators 12 and 2 for generating a 5 ms frame (head) pulse, a clock signal (synchronization) of a PHS digital communication signal, and the like.
2. It has synchronizers 17 and 27 for controlling the synchronization of the 5 ms frame pulse between the phase locked oscillators 12 and 22.

Further, the PHS base stations 14, 19, 24,
PHS base station interface (I
/ F) 13, 18, 23, 28, PHS terminals 10, 1
5, 20, and 25, and PHS base stations 14, 19, 24, and 29 connected by radio (radio waves). Furthermore, the PHS terminals 10, 15, 20, and 25 carried by the subscriber, and trunks 16 and 26 for connecting the private branch exchanges 1 and 2 including trunk lines are configured. Here, a description will be given of a case where the private branch exchange 1 is a main station and the private branch exchange 2 is a subordinate station, and the same operation (result) is obtained when three or more private branch exchanges are connected. Similar operations (results) can be obtained even when the private branch exchange 2 is the master station and the private branch exchange 1 is the slave station.

Further, the trunks 16 and 26 and the 5 ms synchronizers 17 and 27 face each other between the private branch exchanges 1 and 2. Further, the 5 ms (frame) synchronizer 27 accommodated in the private branch exchange 2 serving as a subordinate station supplies the 5 ms frame pulse received from the private branch exchange 1 serving as the main station to the phase locked oscillator 22 of the own station. I have.

FIG. 2 is a block diagram showing the internal configuration of the 5 ms synchronizers 17 and 27. In FIG. 2, the 5 ms synchronizer 17 accommodated in the private branch exchange 1 as a master station has a slave frame pulse generator 31 for generating a slave frame pulse a to be transmitted to the private branch exchange 2 as a subordinate station. Further, it has a 5 ms frame pulse extraction unit 33 that extracts a 5 ms frame pulse from the loopback frame pulse b returned from the private branch exchange 2. Further, a master frame pulse d supplied from the phase locked oscillator 12 of the own station 1 and a loop back frame pulse b
And a phase comparison unit 32 that detects a phase difference from the phase comparison and performs phase correction.

5 accommodated in private branch exchange 2 which is a subordinate station
The ms synchronizer 27 has a 5 ms frame pulse extraction unit 35 that extracts a 5 ms frame (head) pulse (signal) (for a dependent station) from the slave frame pulse a sent from the master station 1. Also, a loopback control unit 34 that returns the received slave frame pulse a in a loop-back manner,
It has a 5 ms frame pulse sending unit 36 for sending the extracted 5 ms frame pulse to the phase locked oscillator 22 in the own station 2.

FIG. 3 is a timing chart in the embodiment of the present invention shown in FIGS. In FIG. 3, the master frame pulse d is the PH accommodated in the private branch exchange 1, which is the main station.
5 ms to send to S base stations 14 and 19 (for main station)
This is a frame head (pulse) signal. The slave frame pulse a is a signal sent from the 5 ms synchronizer 17 to the private branch exchange 2 as a slave station, and the loopback frame pulse b is a signal returned from the private branch exchange 2 as a slave station.

In the pattern shown in FIG. 3A, the phase relationship between the interval A between the slave frame pulse a and the master frame pulse d and the interval B between the master frame pulse d and the loop back frame pulse b are as follows. This is the case where A <B, and the pattern shown in FIG.
> B.

The operation of the embodiment of the present invention will be described with reference to FIGS. First, in FIG. 1, in the private branch exchange 1 of the main station, a master frame pulse d to be transmitted to the PHS base stations 14 and 19 of the own station is generated by the phase-locked oscillator 12, and is transmitted through the time division switch 11. It supplies to the PHS base station interfaces 13, 18 and the 5ms synchronizer 17. Here, the master frame pulse d supplied to the PHS base station interfaces 13 and 18 and the 5 ms synchronizer 17 accommodated in the private branch exchange 1 are naturally synchronized with each other.
Therefore, since the PHS base stations 14 and 19 connected to the PHS base station interfaces 13 and 18, respectively, are synchronized with the PHS base station 1,
Even if 4 and 19 are installed adjacent to each other, radio wave interference does not occur.

In FIG. 2, the 5 ms synchronizer 17 receiving the master frame pulse d considers the transmission delay to the 5 ms synchronizer 27 of the private branch exchange 2 of the subordinate station. As a result, the slave frame pulse generation unit 31 generates a signal (see FIG. 3) at a timing earlier than the master frame pulse d set by the phase comparison unit 32 by a certain phase difference A. As a, it is sent to the private branch exchange 2 which is a dependent station.

Next, in the private branch exchange 2 of the subordinate station, 5 ms
The synchronizer 27 extracts a 5 ms frame pulse from the slave frame pulse a received from the private branch exchange 1 with a 5 ms frame pulse extraction unit 35. Also, the extracted 5 ms frame pulse is sent to the 5 ms frame pulse sending unit 3.
6 to the phase-locked oscillator 22 in the own station 2 and sends the received slave frame pulse a back to the private branch exchange 1 as a loopback frame pulse b from the loopback control unit 34. In the private branch exchange 1, the phase difference (A-B, see FIG. 3) between the loop back frame pulse b received from the private branch exchange 2 and the slave frame pulse a sent by the own station 1 is calculated by the phase comparison unit 32. To detect.

When the phase difference is A <B, FIG.
As shown in (a), the phase is shifted forward by the phase of the phase difference (A−B) ÷ 2, and is accommodated again in the dependent station 2 side.
The slave frame pulse a 'is sent to the ms synchronizer 27. In this case, the loop back frame pulse b 'returns, and A = B. Further, when the phase difference is A> B, as shown in FIG. 3B, the phase difference (AB) Ｂ
The slave frame pulse a "is transmitted to the 5 ms synchronizer 27 accommodated in the subordinate station 2 again. In this case, the loop back frame pulse b" returns and A = B. Become.

The phase-locked oscillator 22 of the private branch exchange 2, which is a subordinate station, generates a 5 ms frame head signal synchronized with the received 5 ms frame pulse c from the 5 ms frame pulse sending section 36 in the 5 ms synchronizer 27. . Further, the generated 5 ms frame head signal is transmitted to the PHS base stations 24 and 29 via the PHS base station interfaces 23 and 28 in the own station 2.

The phase-locked oscillator 22 accommodated in the private branch exchange 2 always synchronizes with the slave frame pulses a, a ', a "received from the private branch exchange 1. The slave frame pulse a and the loop back frame pulse b When the phase relationship of A becomes B = 5 ms between the phase locked oscillator 12 of the master station 1 and the phase locked oscillator 22 of the slave station 2
(Frame) synchronization is completed (as illustrated). as a result,
PHS base station 1 accommodated in each of private branch exchanges 1 and 2
The (frame) synchronization of the radio waves transmitted from 4, 19, 24 and 29 is established.

The case where two stations, a master station and a slave station, are described above, but the same operation (effect) can be obtained even if one master station has a plurality of slave stations. It is also possible that one private branch exchange, which is a subordinate station, becomes a master station with respect to another private branch exchange, and a plurality of subordinate stations are connected under the private branch exchange. As a result, by connecting the subordinate stations to a certain master station in multiple stages, even if the private branch exchanges accommodating the PHS terminals are installed in a distributed manner, 5 private exchanges between the exchanges can be obtained.
ms (frame) synchronization may be established.

[0029]

As described above, the present invention has an effect of preventing radio wave interference between PHS base stations installed adjacently in a private branch exchange accommodating a plurality of installed PHS terminals. That is, by making the 5 ms synchronizer face each other between the private branch exchanges, the 5 ms
This is because (frame) synchronization can be achieved. In addition, the use of the 5 ms synchronization device has the effect of simplifying the circuit / device configuration. Therefore, it is possible to provide a simple radio wave interference prevention device to be used between a plurality of private branch exchanges.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a detailed block diagram of a synchronization device according to the embodiment of the present invention.

FIG. 3 is a timing chart of the embodiment of the present invention.

FIG. 4 is a system block diagram of a private branch exchange accommodating a conventional PHS terminal.

[Explanation of symbols]

 1, 2 Private branch exchange 11, 21 Time division switch 12, 22, Phase locked oscillator 10, 15, 20, 25 PHS terminal 13, 18, 23, 28 PHS base station interface 14, 19, 24, 29 PHS base station 16, 26 Trunk 17,27 Synchronizer

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04Q 3/58 101 H04L 11/00 331 F term (reference) 5K028 AA04 AA07 AA15 BB04 DD02 DD03 MM05 MM12 NN01 NN12 NN22 NN23 NN51 RR01 5K031 AA07 DA07 DB01 DB04 EA02 5K049 AA07 BB04 BB16 BB23 5K067 AA03 BB04 BB08 BB44 DD25 DD57 EE02 EE10 EE16 EE59 5K069 AA02 AA05 CB02 GA02 GA13

Claims (3)

[Claims] 1. A private branch exchange synchronization system for synchronizing private branch exchanges constituting a master station and a subordinate station accommodating a personal handyphone system terminal, wherein a frame synchronization between the master station and the subordinate station is provided. A private branch exchange synchronization system characterized in that: 2. A slave station frame pulse generating means for generating a slave station frame pulse for determining a frame phase of a digital signal of the own station synchronized with a slave frame pulse transmitted from the master station, to the slave station. Loop-back frame pulse transmitting means for returning the slave frame pulse transmitted from the master station to the master station as a loop-back frame pulse is provided, wherein the master station advances the phase of the slave frame pulse to the master station; The phase difference between the slave frame pulse and the master station frame pulse that determines the frame phase of the digital signal of the own station becomes equal to the phase difference between the master station frame pulse and the loopback frame pulse sent back from the slave station. Phase control means for controlling the phase advance means as described above. Private branch exchange between synchronization system of claim 1, wherein. 3. The phase difference between the slave frame pulse and the master station frame pulse or the phase difference between the master station frame pulse and the loopback frame pulse sent back from the slave station, the phase difference between the master station and the master station. 3. The synchronization system between private branch exchanges according to claim 2, wherein the signal transmission time is equal to a signal transmission time with a dependent station.