JPS6216640A - Synchronization switching system - Google Patents

Abstract

PURPOSE:To minimize the generation of a phase discontinuity in case of switching by monitoring a phase difference of two signals by a phase comparing circuit, and switching a line of a sending end side of a stand-by radio line at the time point when its phase difference becomes some value or below. CONSTITUTION:By a control signal 101, a selecting circuit 13 selects a clock signal in a signal 104b (or 104c,...) of existing radio lines (b), (c),... to be switched, and applies it to a phase comparing circuit 14. The phase comparing circuit 14 compares the phases of a clock signal CLK in a signal 103 of a stand-by radio line (a) with a clock signal CLK of the existing radio line, and at the time point when its phase difference enters into some range determined in advance, a controlling circuit 15 is opened and the controlling signal 101 is applied to a switching circuit 16. As a result, the selected existing radio lines (b) (c,...) are switched to the stand-by radio line (a). Accordingly, the large phase discontinuity is not generated in the signal component of the stand-by radio line, the step-out of a clock and the carrier of a receiving side demodulating circuit can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to a digital wireless communication system using a synchronous switching method, particularly a multiphase multi-level modulation method consisting of a backup radio line and a plurality of working radio lines. -Relates to a synchronous switching method that performs backup line switching without momentary interruptions and without code errors.

[Conventional technology]

Digital wireless lines are used in addition to information such as telephone voice.

In recent years, digital information such as data has been increasingly transmitted. Conventionally, in the working/backup switching method using mechanical relays used in analog wireless communication systems, the transition time of the relay cannot be ignored.

In the case of data transmission, there is a problem in that code errors occur due to instantaneous interruptions and loss of synchronization associated with line switching.

Line switching in wireless communication systems occurs when (a) an actual failure occurs in the current line due to a failure, propagation path abnormality, etc.

←) Performed when maintaining the current line as part of preventive maintenance work. In recent wireless communication systems, emphasis has been placed on synchronous switching methods that can switch lines without generating code errors even in the latter case, and one method has already been proposed in Japanese Patent Application Laid-Open No. 55-143850. It is proposed in the Publication No.

This method uses 0 as a switching device on the receiving side.
A synchronous switching circuit consisting of an electronic circuit with a buffer memory described in Publication No. 4709 is used to absorb the propagation time difference (phase difference) caused by the difference in the length of the transmission path between the working and backup channels and the fading of the wireless section, and to eliminate the need for coding. It has a function to switch errors.

On the other hand, as digital modulation methods that can effectively utilize one frequency band, multi-phase multi-value modulation methods such as 8-phase PSK and 16-value QAM are attracting attention and being developed.

These multi-phase multi-level modulation systems are susceptible to fading in the radio section, particularly selective fading.

It would be effective as a countermeasure against fading if a fading working radio line could be switched to a backup radio line without code error.

[Problem that the invention seeks to solve]

When using the above-mentioned conventional synchronous switching method as a countermeasure against such fading, except for the case of a completely synchronous method in which all the digital inputs of each radio line are synchronized, the modulation input of the backup radio line must be changed on the transmitting side. When switching to parallel transmission, a phase discontinuity occurs in the signal component of the backup wireless line.And.

If this discontinuity is large, not only the timing synchronization on the receiving side of the backup radio line but also the carrier synchronization of the demodulation circuit will be significantly lost, and it will take time for synchronization to be re-established and switching to occur, resulting in rapid aging. has the disadvantage of not being compatible with

The present invention improves this and eliminates the above-mentioned drawback by minimizing the discontinuity in the phase of the signal component of the backup radio channel when switching transmission, and when the switching time is short and each working radio channel is asynchronous. The purpose is to provide a synchronous switching method that can be used as a countermeasure against fading.

[Failure to solve the problem]

The synchronous switching method according to the present invention enables multiple working radios 1
a line, at least one backup radio line, and a nucleon□
Transmission switching means provided at the transmitting side modulation input of the backup radio line to switch data and clock input; and synchronization means provided at the receiving side demodulation output of each of the working radio lines to synchronously switch the demodulation outputs of the working and backup radio lines. a switching means;
distribution means provided at the demodulation output of the receiving side of the backup radio line and branching the demodulated data and timing signals to each of the synchronization switching means, and switching between working and backup without momentary interruption.
In a synchronous switching system for a digital wireless communication system that uses no coded errors, the transmission switching means includes a control circuit that controls a switching circuit, a selection circuit that selects a signal on a working line, and a signal on a selected working line and a backup circuit. Equipped with a phase comparison circuit that compares the phase difference of line signals.

The phase comparison circuit detects the optimum point at the time of transmission switching and controls the switching circuit.

[Effect]

In a general line switching configuration, the frequencies of the signal □ of the working radio line and the backup radio line are not the same, but there is a slight difference in frequency. Comparing the phases of two signals with a frequency difference over time, the phase difference gradually increases from a certain value, reaches a maximum, and then decreases.

In the end, the phases match. And after matching.

The phase difference increases again, reaches a maximum, and then decreases again, and the process repeats. Based on this phenomenon, the present invention uses a phase comparator circuit.

The phase difference between these two signals is monitored, and when the phase difference becomes less than a certain value, the transmission end side of the backup wireless line is switched, thereby changing the phase of the signal component of the backup wireless line. If a discontinuity occurs, it can be minimized.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

゛Figure 2 is a block diagram of the synchronous switching method for digital wireless lines described in Japanese Patent Application Laid-Open No. 55-14850.''
It is structured as follows. Working wireless line b # e l sent from a multiplexer (not shown) on the transmitting side
The input signal of ... is the switching device 1b, lc using a relay.
, and then to the transmission code processing circuit 2b.

2. Supplied to c+... Transmission code processing circuit 2b.

2 c+... converts the bipolar signal used on the multiplexing device side into a unipolar signal used for code processing on the wireless device side, performs speed conversion of the code, and converts it into bits for monitoring the wireless line and bits for frame synchronization. Insert and perform scramble processing.

These code-processed digital signals are sent to the transmitters 3b, 3
It is modulated by c, . . . and sent as a radio wave to the other party's station. A transmission switching circuit 4 composed of an electronic circuit is provided between the transmission code processing circuit 2a and the transmitter 3a on the backup radio line a, and normally transmits the signal from the test signal generation circuit 5. The control signal 101 causes the working wireless line blcl...
・It is configured to be able to switch and transmit signals from.

On the receiving side, the receiver 6a16b16el...
demodulated data and clock synchronization signals.

Frame synchronization circuit 7 a l 7 b + 7 C+・
The frame synchronization signals detected in the two-way distribution circuit 8 or the synchronization switching circuits 9b, 9c, . . . are applied to the received code processing circuits 10a, 10b, 10c, . Following the descrambling process, the reception code processing circuit performs transmission rate conversion to remove the inserted pinots for wireless line monitoring and frame synchronization, and converts the signal into a bipolar signal again.

The bipolar signals of the working wireless lines S, C, . The demodulated data and timing signals of the backup radio line a are as follows.

The distribution circuit 8 branches the received code processing circuit 10a on the backup side and the synchronization switching circuits 9b, 9c, .
In addition to 2, 1 is normally used to monitor the status of the backup wireless line. Each working wireless line.

The signal branched to C1... is the synchronous switching circuit 9b.

9c, . . . are configured to switch between the demodulated output of the working radio channel and an uncoded error.

FIG. 1 is a block diagram of an embodiment of a transmission switching circuit according to the present invention, which is applied to the transmission switching circuit 4 in FIG.

The transmission switching circuit 4 is an electronic circuit that instantaneously switches between the signal 103 of the backup wireless line a and the signals 104b, 104c, . . . from the working wireless line blc1, . Phase comparison circuit 14. Control circuit 1
5. It consists of a switching circuit 16.

The operation of this circuit is as follows. In response to the control signal 101, the selection circuit 13 selects the working wireless line blc to be switched.
The clock signal in the signal 104b (or 104C1...) of l... is selected and applied to the 1 phase comparator circuit 14. The phase comparison circuit 14 compares the phases of the clock signal CLK in the signal 103 of the backup radio line a and the clock signal CLK of the selected working radio line, and determines that the phase difference falls within a certain predetermined range. At this point, the control circuit 15 is opened.

By applying the control signal 101 to the switching circuit 16, the selected working radio line is switched to the backup radio line.

With such a switching method, large phase discontinuity does not occur in the signal component of the backup radio channel, and it is possible to prevent clock and carrier synchronization of the receiving demodulation circuit from occurring.

Although the embodiment shown in FIG. 1 shows the case of a four-phase phase modulation system, it goes without saying that the present invention can also be applied to other multi-phase multi-level modulation systems such as an eight-phase phase modulation system. Also,
It is also clear that even when there are two or more backup wireless lines, the same connection configuration as in the embodiment can be used.

〔Effect of the invention〕

As explained above, according to the synchronous switching method of the present invention,
It is possible to shorten the synchronization switching time of working and standby wireless lines that are operated asynchronously, and it can also be used as a countermeasure against fading, making it more economical to implement countermeasures against fading than synchronizing all wireless lines. There are advantages.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a transmission switching circuit which is a main part of the present invention, and FIG. 2 is a block diagram of a synchronous switching system to which the present invention is applied. 1 b, 1 c, 1 l b, 11 c-
...Switcher, 2a. 2 b, 2 c-transmission code processing circuit + 38 +
3b +3c...transmitter, 4...transmission switching circuit,
5...Test signal generation circuit, 6a, 6b, 6cm receiver, 7a. 7b, 7c...frame synchronization circuit, 8...distribution circuit. 9b, 9c=-synchronous switching circuit, 10a, 10
b. 10c... Reception code processing circuit, 12... Test signal detection circuit, 13... Selection circuit, 14... Phase comparison circuit. 15... Control circuit, 16... Switching circuit.

Claims (1)

[Claims] 1. A plurality of working radio lines, at least one backup radio line, a transmission switching means provided at the transmission side modulation input of the protection radio line for switching data and clock input, and a receiving side demodulation output of each of the working radio lines. synchronous switching means provided at the receiving side demodulation output of the protection radio line for synchronously switching the demodulation outputs of the working and backup radio lines; and a synchronous switching means provided at the receiving side demodulation output of the protection radio line for branching the demodulated data and timing signals to each of the synchronous switching means. In a synchronous switching system for a digital wireless communication system, the transmitting switching means has a control circuit that controls the switching circuit and a signal of the working line, in which switching between working and standby is performed without momentary interruption and without code errors. and a phase comparison circuit that compares the phase difference between the signal of the selected working line and the signal of the protection line, and the output of the phase comparison circuit is used for controlling the switching circuit. Switching method.