JPS61105485A - Transmitting method of reference time signal - Google Patents

Abstract

PURPOSE:To supply an accurate reference time to respectively general stations by measuring the delay time of the transmission line of each general station, and determining the transmission phase of the reference time signal in consideration of the delay quantity. CONSTITUTION:A reference station 11 is connected to the general stations 31-3n through transmission lines 21-2n. The reference time signal is generated by the reference station 11 and received by the general stations 31-3n through the transmission lines 21-2n. Each of the general stations 31-3n knows the reference time from the received reference time signal and the reference time signal is branched and sent from the general stations 31-3n back to the reference station 11 through the same routes with onward paths through the transmission lines 21-2n. The reference station 11 measures the time delay quantity from the transmission to the reception of the reference time signal. Then, the transmission phase of the reference time signal is determined in consideration of the delay; quantity to send out the accurate reference time to the respective general stations 31-3n.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to a reference time signal transmission method for supplying reference time from a reference station to geographically distant locations using a wire or wireless transmission path. .

"Prior Art" Conventionally, time services based on radio signals have been used to obtain reference time. Most services use wireless signals to transmit time information. The factors that determine the accuracy of the obtained time are the propagation path delay and its delay variations.

This method attempts to reproduce accurate time at the receiving station by knowing the average propagation path delay and variation in delay amount from the sending station to the receiving station (up to 8 stations).However, in order to know the average propagation path delay, , it is necessary to accurately know the propagation distance and propagation speed between the transmitting station and the receiving station, and if the receiving station is not in a specific location, it is difficult to estimate the average propagation path delay, and the amount of delay is difficult to estimate. Fluctuations are added during propagation and cannot be corrected at the receiving station.

"Means for Solving Problems" According to the present invention, a reference time signal is transmitted from a reference station to a general station, and when the general station receives the reference time signal,
The reference signal is sent back to the reference station, and the reference station measures the time from transmission of the reference time signal to reception of the returned reference signal, and based on the measured value, the phase of the reference time signal transmitted from the reference station. In other words, the phase is advanced so as to obtain a reference time signal that matches the reference time between the two shells. By appropriately repeating such time measurements, it is possible to correct variations in the amount of transmission delay that exceed the time measurement interval, and it is possible to supply the reference time to general stations with high accuracy.

Embodiment FIG. 1 shows an example of the overall configuration of a system to which the reference time transmission method according to the present invention is applied.

The reference station 11 is connected to the transmission line 2. - General station 3 at 21. ~37 are connected. In FIG. 1, transmission line 21.2 is a wired transmission line, and transmission line 2. is a wireless transmission path, and these transmission paths 21 to 2 are round-trip transmission paths. The reference time signal is generated at the reference station 11 and transmitted through the transmission line 2. ~ 211 via each of the general stations 3. Received at ~3,1. In this invention, each inter-shell 3. ~3. Then, we know the reference time from the received reference time signal and branch the reference time signal.
IC stations 31-3. and transmission line 2, respectively. ~2, the data is returned to the reference station 11 via the same route as the outgoing route.

FIG. 2 shows the temporal change of this reference time signal.

FIG. 2A shows the reference time signal 1 sent from the reference station ll.
2, and the reference time signal 12 is sent out at the instant 1°. Figure 2B shows - intershell 3. ~3. .

One of 3. The reference time signal 13 is received by the reference station 11 at time L2. The reference station 11 measures the amount of time delay T from the transmission of the reference time signal 12 to the reception of the reference time signal 13. Transmission line 2. From the standard station 11 to the general station 3. If it is assumed that the outgoing route and the reverse return route are the same route, the transmission time of these outward route and return route is approximately equal, and the time delay amount T is from the reference station 11 to the general station 3. Transmission delay up to “r+
This corresponds to twice z.

FIG. 2C shows the reference time signal 14 which is periodically generated by the reference station 11 and shows 1! E1 time signal 14 has period T1
It is occurring in The reference station 11 receives this reference time signal 1.
4, the reference time signal 12 to be sent to the transmission path 3m is generated by advancing the snake phase by the transmission time T'+s as shown in the second diagram based on ΔT obtained by measuring the signal in FIGS. 2A and 2H.

When this reference time signal 12 reaches the general station 3, it is delayed by Tlt due to the transmission path delay, so that the reference time signal 15 is obtained at the same time as the reference time signal 14 of the reference station 11, as shown in FIG. The sending reference time signal 12 shown in the second diagram is created by advancing the phase of the reference time signal 14 by the Tth time, but in reality it is T m (-T c-T +x
) is more advantageous in terms of circuit configuration. The reference time signal 16 is, for example, 0 seconds of every hour, 0 seconds of every minute,
or a reference time (point in time) such as 0.01 seconds per minute and n;1
These are pulses with coincident edges. Further, the transmission path has sufficient transmission capacity compared to the transmission capacity normally required to transmit the reference time signal 12.

By configuring a frame with a set of a certain number of pulses, the transmission capacity of the transmission path can be used effectively. For example, as shown in FIG. 3, one frame is composed of a frame synchronization signal F, a reference time signal ST, and other information bits D, and if the frame synchronization bit F is detected between the two frames 33, the reference time signal ST While receiving the signal ST, other information and node D can be used. It is also possible to put time information C1 on other information bits D, and the reference time signal ST and time information nC! You can also deal with this. In other words, for example, the reference time indicating 0 seconds of every hour is general station 3. When a reference time signal ST is received at a station, it is possible to know what time it is 0 seconds from the clock of the general station 31, but if the reference time signal is generated relatively frequently or there is no clock between shells. In this case, it can be seen that the reference time signal corresponds to the time information CI.

Next, a configuration example of the reference station 11 will be explained with reference to FIG. 4. First, the reference time signal 14 is generated by the pulse signal generator 19 based on the output of the main oscillator 18 which serves as a reference such as the period Tt of the reference time signal. The reference time signal 14 is
The time All adjustment unit 21 takes correspondence with the time,
This becomes a reference time signal 22 with time information, and a frame synchronization signal F is added by a frame synchronization signal generator 23 to become a transmission reference time signal 24. Reference time signal 24
After passing through delay circuits 41-47, the signals are supplied to general stations 31-37 via outgoing paths 2a of transmission lines 21-2, respectively.

General station 3. ~37 to transmission line 2I~2. One of the reference time signals 51 to 5 returned via each return path 2b is selected by the changeover switch 25, and the selected reference time signal 5 is the 0 time input to the time interval measuring section 26. The interval measurement section 26 uses the reference time signal 22 and 5. The phase difference (time difference) is measured and the measured value 27 is sent to the control unit 28.

The control unit 2B creates delay amount control data 6+ (i=1.2. . . . n) according to the measured value 27 at the cycle of the control cycle signal 29 from the pulse signal generator 19, and selects the changeover switch 25. General station 3゜(i -1, 2,
..., n) to the delay circuit 4N for phase adjustment. Change the changeover switch 25 to sequentially - between ships 3
．． Delay circuit 4 corresponding to ~37. ~4. By adjusting these operations and repeating these operations using the control periodic signal 29, all inter-ship 3. -37, the reference time signal 22 can be reproduced at the reference time. Delay circuit 4. .about.41 may be of a digital type, such as a shift register, or of other analog type.

An example of the configuration of three general station reefs is shown in Figure 5. The reference time signal 24 from the reference station 11 is branched into two by the signal distributor 31, one of which is sent to the general station 3. one for reference station 1, and the other for reference station 1.
The reference time signal 24 returned to the reference station 11 is 5 degrees, that is, in the -ship 3I, a circuit for simply branching and returning the reference time signal 24 received from the reference station 11 to the general station used in the conventional system. It only requires This returned reference time signal 5. Therefore, as mentioned earlier, the reference station 11 sends out the reference time signal 24 whose phase has been adjusted for each ship interval 11. Therefore, by reproducing the reference time signal 24, accurate reference time can be obtained.

- between ships 3. The reference time signal 24 taken into the decoder 32
The frame synchronization signal F is used to separate the reference time signal 22 with time information and other information data.

This reference time signal 22 is supplied to a synchronization circuit 33. Even during the period when the base time signal 24 is interrupted, the base time signal 22 is transmitted between -3 and 3. For example, the output of the oscillator 34 is sent to the basic clock 3 by the pulse generator 35 so that it can be supplied to the basic clock 3.
6 and is supplied to the synchronization circuit 33 via the delay circuit 37. The frequency of the basic clock 36 of the pulse generator 35 is almost the same as that of the reference time signal 22, but the phase is not necessarily the same, and the reference time signal 22 is interrupted due to measurement of the amount of delay time, etc. During this time, a phase difference occurs between the basic clock 36 and the reference time signal 22. The phase difference between the basic tarokk 36 and the reference time signal 24 is detected by the synchronization circuit 33, and its output is used as the delay circuit 37.
is adjusted. By providing this synchronization circuit 33, each ship-to-ship 3. Reference time signal 2 for
The phase adjustment period of 4 can be lengthened, the number of 3 shifts of general stations that can be accommodated in the reference station 11 can be increased, and furthermore, it is possible to cope with transmission path failures.

Furthermore, although the oscillator 34 is a fixed oscillator in FIG.
As shown in FIG.
It may also be supplied to −°general 1 as shown in Figure 6B.
The basic clock 3'8 may be branched from an inter-network M device 39 incorporated in a frequency synchronization network that is separately configured as an lnla network and supplied to the pulse generator 35.

As for the transmission line 2I, even if the outgoing path 2a and the incoming path 2b are not the same, the amount of transmission delay changes in the same 7111 case,
In addition, it is only necessary that the transmission delay ratio between the outbound route and the return route is known in advance. Depending on how 1A quasi-time is used, synchronous circuit 3
3 can be omitted.

"Effects of the Invention" As described above, according to the present invention, the delay amount of the transmission path is measured for each shell, and the sending phase of the reference time signal is determined by anticipating the delay amount in advance. Therefore, an accurate reference time can be given between each ship.

Since the general station only needs to send the received reference time signal from the standard station back to the standard station, the circuitry required for adjustment installed at the general station can be extremely simplified and has the advantage of being economical.

Furthermore, if the reference station sequentially selects the reference time signals returned from multiple general stations using one circuit and measures the delay between each general station and the reference station, the measurement circuit installed at the reference station can be effectively used.

Furthermore, the accurate reference time obtained in this way can be effectively used in the following fields. First, in the field of communications, it can be used as a reference time to realize simultaneous switching control among multiple stations in repairing faults in transmission paths or switching without momentary interruptions.

Furthermore, in the field of information processing, it can also be used as a reference time to ensure concurrency in simultaneous data updates in distributed database management systems that will continue to develop.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the overall configuration of a system using the method of the present invention, Fig. 2 is a time chart showing temporal changes in a reference time signal, and Fig. 3 is a diagram of an l frame for transmitting the reference time signal. Figure 4 is a block diagram showing an example of the configuration of a reference station, Figure 5 is a block diagram showing an example of the configuration of a general station, and Figure 6 is a block diagram showing another example of the basic clock generation method. It is. 11... Reference station, 2I~2,... Propagation path, 31~3
a゛... General station, 14... Reference time signal generated at reference station 11, 41-4... Delay circuit, 5. ~
5o... Return reference time signal, 25... Changeover switch, 26... Time interval measurement section, 27... Time difference measurement value, 28... Control section, 6. ~6. 1...Delay 1 control data, 31...Signal distribution unit. Patent Applicant: Nippon Telegraph and Telephone Public Corporation Representative Patent Attorney Takugyu Kusano 2 Figure FST Day O

Claims (1)

[Claims] (1) A reference time signal is transmitted from the reference station that generates the reference time to a general station that requires the reference time, and the general station returns the received reference time signal to the reference station, and the reference station generates the reference time. The time from the transmission of the signal to the reception of the returned reference signal is measured, and based on the measured value, the phase of the reference time signal transmitted from the reference station is adjusted, and the reference time signal that matches the reference time at the general station is generated. A reference time signal transmission method that obtains the following.