JPS6033325B2 - Unified timing method in communication systems - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a timing unification scheme in a telecommunications system including a time division multiplexed modem.

FIG. 1 is a diagram showing a normal communication system including a time division multiplexing modem, and FIG. 2 is a diagram showing the relationship between modulation rate and multiplexing in the time division multiplexing modem.

In Figure 1, M and m are time division multiplex modems (hereinafter referred to as
It is called a modem with TOM).

This modem with TDM is a CCITT recommendation V2 modem for needlemen. To explain the operation of this type of modem with TDM,
2400 bps channel (low speed line) #1, #2, #
A bit of 1/960 Msec is assigned to each of #3 and #4, and four consecutive bits of 1/960 Msec are transmitted to a high-speed line subjected to quadrature amplitude modulation. in this case,
The communication speed of the multiplexed channel must be synchronized with the modulation speed of the modem. That is, the relationship 2400×4=9600 must be accurately established for one channel.

Therefore, in a communication system as shown in Fig. 1, a 2400Hz clock is created by frequency-dividing the clock generator in the TDM modem, and this is distributed to terminals and communication control units. The timing is unified throughout the communication system. Another method is to receive a 2400Hz clock from channel #1, create a 2400Hz signal synchronized with this from the clock generator in the TDM modem, and send this to other channels #2, #3, #4. It is also known that it distributes to FIG. 3 shows a communication system to which the present invention is applied.
, to M3 and M', to M'3 indicate modems with TDM. The TDM-equipped modems M, , M2 and M3 constitute a first modem group, and the TDM-equipped modems m, , M2 and M3 constitute a first modem group.
m2 and m3 constitute a second modem group. Second
Each modem with TDM belonging to the modem group m,, m2, m3
The low-speed line side of the TDM modems M, , M2, and M3 belonging to the first modem group are interconnected by a low-speed line. Such a connection is adopted in order to enable communication even if a failure occurs in one part of the TDM-equipped modem or line. However, the third
In the communication system shown in the figure, for example, a modem M.
If the timing between modem M2 and modem M2 is different, modem m
, it is not possible to adopt the timing unification method as described above. The present invention is based on the above consideration, and includes a first modem group having a plurality of time division multiplexing modems, a second modem group having a plurality of time division multiplexing modems, and a second modem group having a plurality of time division multiplexing modems. In a communication system in which the low-speed line side of each time-division multiplexing modem belonging to a modem group is connected to the low-speed line side of a plurality of time-division multiplexing modems belonging to a second modem group by a low-speed line, the timing of the entire communication system is The purpose of this invention is to provide a timing unification method for communication systems that ensures unification.

Therefore, the timing unification method in the communication system of the present invention sets a modem group in which a plurality of time-division multiplexing modems are arranged in parallel with each other, and uses the pattern of the modem group set above to modem group, and the low-speed line side of each time-division multiplexing modem belonging to the first modem group and the low-speed line side of each time-division multiplexing modem belonging to the second modem group are interconnected via a low-speed line. A timing unification method in a communication system connected to the time division multiplexing modem, the time division multiplexing modem comprising: a phase synchronization circuit; means for performing a time division multiplexing operation in synchronization with a clock output from the phase synchronization circuit; A clock input terminal for inputting an external clock to the synchronous circuit, and a clock for transmitting the clock output from the phase synchronous circuit to the outside. one time-division multiplexing modem among the plurality of time-division multiplexing modems belonging to the first modem group or the second modem group is selected as the main modem, and the remaining A division multiplexing modem is used as a slave modem, and the phase synchronization circuit of the master modem outputs a clock synchronized with the clock that inputs the clock from the source to the clock in the master modem. The phase synchronized circuit is supplied with the clock output from the phase synchronized circuit of the main modem through the clock output terminal of the main modem, the clock signal line, and the clock input terminal of the slave modem, and the clock in the slave modem. By inputting the clock from the generation source and outputting a clock synchronized with the clock output from the phase synchronization circuit of the main modem from the phase synchronization circuit of the slave modem, This is a timing unification method in a communication system characterized by synchronizing the clocks of time division multiplexed modems. Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 3 is a diagram showing an outline of one embodiment of the present invention, and FIG. 4 is a block diagram of one example of the main part thereof. In FIGS. 3 and 4, 1 to 13 are clock signal lines, and 1 is a PLL.
(phase locked loop), 2 is a driver, 3 is a receiver, 4 is a clock output terminal, 5 is a clock input terminal, 6 is a channel connected to a low-speed line or terminal device, etc., 7 is a A time-division multiplexing device that time-division multiplexes a low-speed line and converts it to a high-speed line;
Reference numeral 8 denotes a line modem which modulates the multiplexed signals of each channel or demodulates the received signal received from the high-speed line and delivers it to the time division multiplexer.

In the TDM modems M2 and M3 shown in FIG. 4, the channel 6, time division multiplexer 7, and line modem 8 are omitted. Further, the PLL constitutes a phase locked circuit. In FIG. 3, modem M with TDM is the main modem, and a clock is sent from modem M with TDM to modem M3 with TDM via clock signal lines 1, 12.
The TDM-equipped modems M2 and M3 synchronize their own clocks with the sent clock. The TDM-equipped modem M'i can synchronize its own clock with the clock of the corresponding TDM-equipped modem Mi, and the TDM-equipped modem mi can synchronize its own clock with the clock of the corresponding TDM-equipped modem Mi, Since the TDM modem m'i can synchronize its own clock with the clock of the corresponding TDM modem ml, the timing of the entire communication system is unified. It goes without saying that the subscript i is 1, 2, and 3. FIG. 4 is a block diagram of an example of the main part of the present invention.

As mentioned above, the TDM-equipped modem M is selected as the main modem, and the TDM-equipped modems M2 and M3 are selected as the slave modems. Modem M with TDM is INTERNAL
mode is set. In INTERNAL mode, clock output terminal 4 is closed and clock input terminal 5 is turned off. In the INTERNAL mode, a clock from a clock generation source (not shown) within the own modem is supplied to the PLLI, and the PLLI outputs a clock synchronized with the clock of the clock generation source within the second modem. TDM modems M2 and M3 are set to EXTERNAL mode. In EXTERNAL mode, clock output terminal 4 is open and clock input terminal 5 is closed. Modem M with TDM is in INTERNAL mode, T
Since the modems M2 and M3 with DM are set to the EXTERNAL mode, the clock output from PLL1 of the modem M with TDM is supplied to channel 6, time division multiplexer 7, and line modem 8 within the own device. At the same time, it is applied to the PLLI of the modem with TDM M2 via the driver 2, the clock signal line 1, the clock input terminal 5 of the modem with TDM M2, and the receiver 3, and as a result, the clock generation source in the modem with TDM M2 (Fig. The clock output from the TDM modem (not shown) is a clock synchronized with the clock of the TDM-equipped modem M. Further, the clock output from the modem M with TDM is applied to the modem M3 with TDM via clock signal lines 1 and 12, and the clock output from the clock generation source (not shown) in the modem M3 with TDM is applied to the modem M3 with TDM. is a clock synchronized with the clock of modem M with TDM. In addition,
Instead of configuring the first modem group M, , M2, M3 as shown in FIG.
It may be configured as shown in the figure. As is clear from the above description, according to the present invention, even in a communication system having a configuration in which a low-speed line of a TDM-equipped modem is connected to a plurality of TDM-equipped modems, the timing of the entire communication system can be accurately unified. I can do it.

Brief Description of the Drawings Figure 1 is a diagram showing a normal communication system including a time division multiplexing modem, Figure 2 is a diagram showing the relationship between modulation rate and multiplexing in a time division multiplexing modem, and Figure 3 is a diagram showing the relationship between the modulation rate and multiplexing in a time division multiplexing modem. A diagram showing an outline of one embodiment of the invention, FIG. 4 is the main part 1
FIG. 2 is an example block diagram.

m', to m'3, m, to m3, M, to M3
and M, to M'3...modem with TDM,
1, to 13... Clock signal line, 1...
- PLL (Fes-locked loop), 2... Driver, 3... Receiver, 4... Clock output terminal, 5... Clock input terminal.

O 1 80 2nd figure talent figure Sai 4 figure

Claims (1)

[Claims] 1 Set up a modem group in which a plurality of time division multiplexed modems are arranged in parallel with each other, configure a first modem group and a second modem group using the pattern of the modem group set above, and A timing unification method in a communication system in which the low-speed line side of each time-division multiplexing modem belonging to a group and the low-speed line side of each time-division multiplexing modem belonging to the second modem group are interconnected by a low-speed line. , the time-division multiplexing modem includes a phase-locked circuit, a means for performing a time-division multiplexing operation in synchronization with a clock output from the phase-locked circuit, and a means for inputting an external clock to the phase-locked circuit. A clock input terminal and a clock output terminal for externally transmitting the clock output from the phase synchronized circuit are provided, and one of the plurality of time division multiplexing modems belonging to the first modem group or the second modem group is provided. One time-division multiplexing modem is selected as the main modem, and the remaining time-division multiplexing modems are selected as slave modems, and the phase synchronization circuit of the main modem is connected to the clock generation source in the main modem. A clock is input, a clock synchronized with the clock is output, and the clock output terminal of the main modem is connected to the phase synchronization circuit of the slave modem through the clock output terminal of the master modem, the clock signal line, and the clock input terminal of the slave modem. Inputs the clock output from the phase-locked circuit, and also inputs the clock from the clock generation source in the slave modem, and outputs a clock synchronized with the clock output from the phase-locked circuit of the main modem from the phase-locked circuit of the slave modem. 1. A timing unification method in a communication system, characterized in that the clocks of time division multiplexed modems in the first modem group or the second modem group are synchronized by synchronizing the clocks thereof.