JP2937783B2 - Staff synchronization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stuff synchronous multiplexer and, more particularly, to a digital multiplex radio apparatus.

[0002]

2. Description of the Related Art In a digital multiplex radio apparatus, a synchronization system based on pulse stuffing is generally used.

That is, the output transmission speed of a multiplexing device is made higher than the sum of the maximum transmission speeds of input signals, and extra transmission capacity is generated in the device by inserting a stuff pulse into each input signal. Used to increase the input signal speed up to the clock signal speed.

In such a conventional multiplexer using the stuff synchronization method, a frame designation pulse is inserted once per frame only when a stuff pulse is performed.

[0005] In this case, if a burst error having a length of one frame or more occurs, the receiving side cannot accurately detect the stuff designation pulse.

Therefore, the PCM devices in the low-order group a plurality of times lose synchronization, and the influence on the lower-order group becomes very large.

As described above, since the receiving side constantly monitors the presence of the stuff pulse, if a burst error that continues for one frame or more occurs, the presence or absence of the stuff designated pulse is erroneously determined.

Therefore, for example, Japanese Patent Application Laid-Open No. 61-98034
In the “stuff-designated pulse detection method” described in Japanese Patent Application Laid-Open Publication No. H11-27139, the detection of the stuff-designated pulse is performed for the frame determined by the stuff rate and the frames before and after the frame, and the detection is not performed for other frames. Also, there is disclosed a technique for reducing erroneous detection of stuff information due to a burst error.

[0009]

In this prior art, only a frame having a period determined by the stuff ratio and frames before and after the frame are stuff information detectable frames. However, when a burst error occurs in the stuff information detectable frame, there has been a problem that the receiving side where the stuff information is correctly detected malfunctions.

[0010]

According to the stuff synchronization system of the present invention, when a burst error occurs due to switching of a transmission line and a separation operation malfunction (hereinafter, a destuff error) occurs due to a stuff information detection error, a multiplexing unit is used. The switching advance information is multiplexed and transmitted, and the stuff operation is fixed for a certain period of time. On the other hand, when the switching unit receives the prior information of the switching, detection of the stuff information is prohibited for a certain period of time as in the transmitting side, and the destuff operation is fixed to prevent the destuff error.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention.

In FIG. 1, data and a clock signal are input to a multiplexing unit 50, and a multiplexed data signal is transmitted to a demultiplexing unit 70 through a radio transmission line 60. The wireless transmission path 60 is provided with a playing switching circuit in which a transmitter is duplexed and one of them is used for switching.

The multiplexed data demodulated by the receiver 28 in the transmission line 60 is separated by a separating unit 70 into data and a clock.

The details of this configuration will be described below. In this figure, data is input to an elastic memory 1. The clock is input to an N frequency divider 3 that divides the clock frequency by N (a positive integer of 2 or more), and the output is input to a phase comparator 5. On the other hand, the clock pulse of the frequency of the multiplexing speed from the oscillator 9 passes through the inhibition circuit 10 comprising an AND gate and an inverter to change the frequency of the oscillator 9 to (N
+1) The input is input to the (N + 1) frequency divider 4 for frequency division, and the output thereof is input to the phase comparator 5. In the phase comparator 5, the N frequency divider 4
And outputs a match / mismatch of the phase to the stuff information transmitting unit 6. The stuff information transmitting section 6 outputs a stuff request signal when the output of the phase comparator 5 is determined to be out of phase. The staff request signal is A
The signal is input to a fixed circuit 1 including an ND gate and an inverter. The advance information transmitting unit 7 outputs the stuff control signal to the fixed circuit 11 so as to prohibit the stuff control signal for a certain period of time when external information of the transmission path quality deterioration at the time of switching or the like is input from outside. Fixed circuit 1
After the output of 1 is input to the stuff information multiplexing unit 2 composed of an OR gater, the output of the stuff information multiplexing unit 2 is input to the multiplexing unit 13. Therefore, after performing the multiplexing process, the multiplexing unit 13 outputs a multiplexed signal. The signal is input to each of the transmitter 26 and the transmitter 27 and output as a modulated wave suitable for radio. The transmission path is switched by selecting one of the outputs of the transmitter 26 and the transmitter 27 for switching.

On the other hand, the signal received by the receiver 28 is demodulated and becomes a digital multiplexed signal, which is input to the demultiplexer 14 and subjected to demultiplexing processing. Prior information obtained by the separation process is subjected to bit error protection processing by the prior information detection unit 21 and output to the fixed circuit 22, so that the destuff operation is prohibited for a certain period of time as in the stuff operation. Even if a burst error occurs due to switching during the fixed period and stuff information is erroneously detected, erroneous destuffing control is prevented.

The operation described above will be described with reference to a time chart shown in FIG.

FIG. 3A shows a switching control signal, and the switching operation is performed at a certain time t ₀ (s).

FIG. 3B shows an output waveform of the advance information transmitting unit 7, which changes its state at the rise of the switching control signal.
A pulse is transmitted for a fixed time (T _I ). This time is the staff ban period. In this embodiment, the above-mentioned T _I for simplicity, have been selected the same as the frame period of the multiplexed signal (T _F), not limited to this value, T _F
Any value larger than this may be used. It is possible to ban the stuff pulse in the always T _I by choosing the T _I above this T _F. Of course, the same operation is performed even when the switching control signal falls.

FIG. 3C shows multiplexed data in the multiplexing circuit 13. The portion indicated by hatching portion of the figure, a pulse indicating prior information, rising staff inhibit period T _I obtained in advance information sending unit 7 described above in synchronization with the time slots of the multiplexed signal, falling In, is inserted.

As a result, it is possible to insert two prior information pulses indicating the stuff inhibition period into the multiplexed signal.

FIG. 3D shows the output waveform of the delay circuit 8. That is, the output of the prior information transmission circuit shown in (b) is input and delayed by the prior information detection time on the separation unit side. In this embodiment, for the sake of simplicity, the delay is delayed by the time T _D1 equal to the above-described staff inhibition period T _I.

FIG. 5E shows an output waveform of the delay circuit 25 which receives the switching control signal and delays the signal by a predetermined time. In this case, it is provided for switching the switch 24 during the staff prohibition period. In the present embodiment, the delay time is delayed by a time T _D2 longer than the staff inhibition period T _I.

(F) is the transmitter 26, (g) is the transmitter 2
7 shows multiplexed data input. In this figure, (f) and (g) are the same data, and each of them is input to the transmitter 26 and the transmitter 27 to switch between them to form a duplex configuration.

To explain (f), the prior information pulse by the output signal of the prior information transmission circuit 7 shown in (c) and the delayed prior information pulse by the output signal of the delay circuit 8 shown in (d) will be described. It is a multiplexed signal.

Next, (h) shows the multiplexed data at the time of output from the switch 24.

In this figure, within the staff ban period,
The delay time T _D2 is longer than the rise time (t ₀ ) of the switching control signal.
The actual switching operation is performed from the time t ₁ delayed by only this time, and the switch 24 operates.

The switch 24 switches the transmitter in a short time, but an instantaneous interruption of about several 100 μs occurs.

Assuming that this time is T _B , this time is a period during which a burst error occurs.

Next, the operation of the separation unit will be described.

(I) shows the multiplexed data demodulated by the receiver 28, and the same waveform as the multiplexed data shown in (h) is obtained.

In (j), the first prior information pulse is separated from the multiplexed signal shown in (i) by the separation unit 14, and
3 shows a waveform input to the advance information detection circuit 21.

(K) shows the output waveform of the prior information detection circuit 21.

In the figure, the following two information pulses are detected based on the first prior information pulse shown by (j).
It has been shown to output the staff prohibition period T _I.

This output signal is input to the gate circuit 24, and by inhibiting the output signal of the stuff information detecting section 20, the destuff operation is inhibited.

As a result, even if a burst error occurs during the switching operation, malfunction of the stuff is prevented.

Here, 10 Mb is actually used by using this embodiment.
when applied to data multiplexing ps as 500μs staff prohibition period T _I, the burst error occurrence time T _B by the switch 24 becomes 200 [mu] s.

In the embodiment described above, the occurrence of a burst error due to an instantaneous interruption of the switch 24 has been shown as advance information.
The present invention is not limited to this. For example, by inputting a variation outside the allowable range of the frequency variation of the local oscillator of the high-frequency circuit to the advance information transmitting circuit 7 and appropriately selecting the delay circuits 8 and 25. Needless to say, the same effect as that of the present embodiment is obtained.

[0038]

As described above, according to the present invention, prior information on the occurrence of a burst error is multiplexed and transmitted, and the stuffing and destuffing operations are fixed in the same manner in accordance with the prior information. Even if a burst error occurs in a stuff frame enabling frame, a destuff error does not occur.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a time chart of each unit in FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 elastic memory 2 stuff information multiplexing unit 3 N frequency divider 4 N + 1 frequency divider 5 phase comparator 6 stuff information transmitting unit 7 advance information transmitting unit 8 delay circuit 9 oscillator 10 inhibit circuit 11 fixed circuit 12 fixed circuit 13 multiplex Conversion unit 14 separation unit 15 elastic memory 16 N + 1 frequency divider 17 N frequency divider 18 phase comparator 19 voltage controlled oscillator 20 stuff information detection unit 21 prior information detection unit 22 fixed circuit 23 prohibition circuit 24 switch 25 delay circuit 26 Transmitter 27 Transmitter 28 Receiver 50 Multiplexer 60 Transmission path 70 Demultiplexer

Claims (5)

(57) [Claims] 1. A stuff synchronization method for a digital multiplex radio apparatus which multiplexes a stuff signal with data, transmits the multiplexed signal, separates the received multiplexed signal, and performs a destuff operation. A stuff operation prohibition unit for prohibiting the stuff operation for a predetermined stuff operation prohibition time based on the prior information to be notified, and a data for prohibiting the destuff operation by detecting the prohibition time of the stuff operation prohibition unit in response to the multiplexed signal. A staff synchronization method comprising a staff inhibiting means. 2. The stuff synchronization system according to claim 1, wherein said advance information is based on a switching control signal of a switch for switching between a working transmitter and a backup transmitter of said digital multiplex radio apparatus. 3. The prior information transmission circuit for receiving the advance information and transmitting a stuff inhibition signal for inhibiting a stuff operation for the stuff operation inhibition time longer than the data frame time, First and second prior information pulses are inserted into the data at the time of the rising (falling) and the falling (rising) of the stuff operation prohibition signal, respectively, and the stuff operation prohibition signal is prohibited for the predetermined period. And a multiplexing circuit for inserting third and fourth advance information pulses delayed at the time of rising (falling) and falling (rising) through said delay circuit into said data. 1. The staff synchronization method described in 1. 4. The switcher stores the advance information in the first information.
3. The stuff synchronization system according to claim 2, wherein the switching unit is switched via a second delay circuit that delays by a longer time than the delay circuit. 5. The destuffing inhibiting means, comprising: a separating circuit that receives the data and the multiplexed signal to detect the first prior information pulse; and a third circuit that detects the third prior information pulse based on the first prior information pulse. And a pre-information detecting circuit for transmitting a destuffing prohibition signal for prohibiting a destuffing operation during the fourth pre-information pulse, and a prohibiting circuit for prohibiting the destuffing operation based on the destuffing prohibition signal. The destuffing synchronization method according to claim 3.