JPH0369218A - Tdma communication system - Google Patents

Abstract

PURPOSE:To normally maintain a communication system by transmitting the respective reference burst signals of two reference stations by carriers each different in a system to control the transmission timing of each communication terminal station according to the reference burst signals to be transmitted by the two reference stations. CONSTITUTION:Out of many communication terminal stations 2A-2N, the stations 2B and 2M are selected as the reference stations, for example. The two reference stations 2B and 2M transmit the respective reference burst signals by respective different carriers 11 and 12. Carrier signals to transmit the two reference burst signals are converted to an IF level and supplied to demodulators 101 and 102 as IF signals 11 and 12. In a synchronizing holding circuit 105, out of unique word signals 15 and 16 of the two reference burst signals, reception synchronization is held with one signal as a reference according to logic determined in advance. Accordingly, even in a TDMA satellite communication network for which an interference wave is existent, the reception synchronization can be held.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is applied to satellite communications. The present invention is suitable for use in communication systems such as intercontinental communication where the mutual distance between communication terminal stations is extremely large.

〔overview〕

The present invention provides a system in which two of a large number of communication terminal stations using one satellite communication system are used as reference stations, and the transmission timing of each communication terminal station is controlled according to a reference burst signal transmitted by the reference station. By transmitting each reference burst signal from one reference station using a different carrier wave, it is possible to avoid a situation where neither of the two reference carrier waves can be received even if interference or other propagation problems occur.

[Conventional technology]

A conventional TDMA satellite communication network using multiple carriers is described. In this TDMA satellite communication network, the amount of traffic that can be transmitted is limited by the band of the satellite relay device (transponder) used. In a TDM satellite communication network including a large number of general communication terminal stations, the amount of traffic to be transmitted cannot be covered by the band of one satellite relay device. For this purpose, multiple satellite relay devices with different carrier frequencies are used simultaneously.
Configure the network. The reference station transmits a reference burst on the carrier frequency of each satellite repeater to define the time reference for the TDMA frame. In a typical TDMA satellite communication network, two reference stations are used, one for each carrier, in order to improve network reliability, that is, one reference burst signal can be used as the time reference for reception synchronization. Sending a reference burst. Therefore, there are two reference burst signals on one received carrier. A general communication terminal station uses one of a plurality of reception carrier waves as a reception synchronization carrier wave, and establishes and maintains reception TDMA frame synchronization using either of the two reference burst signals above this carrier wave as a reference.

For traffic bursts exchanged between communication terminal stations, by switching the carrier manually input to the demodulator within a TDMA frame in synchronization with the position within that frame, the traffic burst transmitted to any carrier can be As long as it does not overlap, reception is possible and communication can be performed.

However, in the process of establishing reception synchronization for reference burst signals, it is not possible to control the switching of the reception carrier wave, so as mentioned above, it is difficult to receive two reference burst signals on one reception carrier wave whose frequency is determined in advance. It is used to maintain synchronization. The method for establishing and maintaining reception synchronization at the reference station is the same as that for other communication terminal stations.

Next, an example of the synchronization holding function according to the conventional method will be explained with reference to the drawings.

In FIG. 2, the carrier signal transmitted from the first satellite relay device and received by the device at the earth terminal station is converted to an IF level, and is sent to the hopping switch 200 as an IF signal 21a.
is input. Similarly, the carrier wave signal transmitted from the n-th satellite relay device and received by the communication terminal equipment on earth is 1
The signal is converted to F level and input to the hopping switch 201 as an IF signal 2In. Therefore, n IF signals are input to the hopping switch 201. A hopping switch control signal 22 is supplied to the hopping switch 201 from a hopping switch control signal generation circuit 202 to control on/off of the hopping switch. In the normal synchronized state, the hopping switch control signal generation circuit 202 operates as shown in the timing chart 311 of FIG.
A hopping switch control signal as shown in is generated according to the burst time plan information 23 stored in the storage circuit 203 in advance. That is, the timing 303 when the first reference burst signal 301 of the TDMA frame indicated by reference numeral 310 in FIG. 3 can be received.
The hopping switch control signal 22 is generated so that either of the timing 304 and the timing 304 at which the second reference burst signal 302 can be received is received from the same carrier wave that is predetermined in the burst time plan. In FIG. 3, the first reference burst signal 3
01 and the timing 304 when the second reference burst signal 302 can be received are shown consecutively, but they may exist independently. IF selected by hopping switch 201
Signal 24 is provided to demodulator 204. The signal 25 demodulated by the demodulator 204 is sent to the unique word detection circuit 205.
A unique word of either the predetermined first or second reference burst is detected and supplied as a detection signal 26 or 27 to the synchronization holding circuit 206 .

In the synchronization holding circuit 206, reception synchronization is maintained using the unique word detection signal 26 or 27 of the first or second reference burst as a reference according to a predetermined logic.

[Problem that the invention seeks to solve]

However, in the conventional method, one of the two reference burst signals on one received carrier wave is used as the time reference signal of the TDMA reception frame to maintain reception synchronization, so the transmission carrier corresponding to this reception carrier wave If interference waves such as continuous waves are added to the network, it becomes impossible to receive both of the two reference burst signals at the same time, making it impossible to maintain reception synchronization at all stations participating in the network. Put it away. In particular, in a TDMA satellite communication system that performs communication across regional beams, such as intercontinental communication, it becomes impossible to maintain reception synchronization even at the reference station, and the synchronization of the entire network collapses. In this case, in order to restart, it is necessary to start up all stations from the initial stage, which has the disadvantage that the communication network is interrupted for a long time which cannot be ignored. - In an international satellite communication network in which many countries participate, there is a non-negligible probability that one of the stations will erroneously transmit an interference wave on a single carrier wave.

Since TDMA satellite communication is a communication method that transmits one wave to one satellite relay device, the influence of these interference waves on communication is fateful and fatal.

The present invention solves these shortcomings and provides a TDM system that enables smooth network operation without causing the entire network to become out of synchronization even if there is interference.
The purpose is to provide a communication method for satellite communication terminals.

[Means for solving problems]

The present invention includes one satellite relay device and a large number of communication terminal stations, two of the communication terminal stations are selected as reference stations, and each of these two reference stations transmits a reference burst during a TDMA frame. The two reference stations include means for controlling the timing of mutually transmitting reference burst signals, and the communication terminal station transmits the reference burst signals of the two reference stations that are relayed and received by the satellite relay device. In TDMA communication, the two reference stations are configured to transmit their respective reference burst signals using different carrier waves, respectively, in TDMA communication equipped with a means for controlling the transmission timing of the own station based on one receivable one of the reference burst signals. The communication terminal is
The present invention is characterized in that it includes means for extracting each reference burst signal transmitted from two reference stations from different carrier waves.

[Effect]

Two reference burst signals are provided, and under normal conditions, these two reference burst signals are synchronized with each other, and one of these two reference burst signals is used to control the transmission timing of the own station. The two reference burst signals are transmitted using carrier waves of different frequencies. Therefore, even if interference waves or the like occur in one carrier wave, the possibility that both of the two reference burst signals become unreceivable is reduced, and the communication system can be maintained normally.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. 1st
The figure is a block diagram of an embodiment of the present invention.

In FIG. 1, the present embodiment is composed of a satellite relay device 1 and a large number of communication terminal stations 2A to 2N. Among these communication terminal stations, those with reference symbols 2B and 2M are selected as reference stations, and these reference stations 2B and 2M are each equipped with a means for transmitting a reference burst signal during a TDMA frame, and also transmit reference burst signals to each other via line 3. It controls the timing. Other communication terminal stations 2A, 2C to 2L, and 2N are two reference stations 2B that are relayed and received by the satellite relay device 1.
, 2M is equipped with means for controlling the transmission timing of its own station based on a receivable reference burst signal among the reference burst signals transmitted by 2M.

Here, the feature of the present invention is that two reference stations 2B
and 2M are configured to transmit the respective reference burst signals using different carrier waves 11 and 12, respectively, and the communication terminal stations 2A, 2C to 2L, and 2N transmit the first IF signals 11 and 2M using different carrier waves, respectively. The present invention includes means for extracting each reference burst signal from the second IF signal 12.

As a means for extracting this reference burst signal, as shown in the receiving circuit of the communication terminal station 2N in FIG.
a detection circuit 103 that detects the first unique word; and a second demodulator 1 that similarly demodulates the second IF signal 12.
02 and a detection circuit 105 that detects the second unique word from this output, and these two detection circuits 105.1.
A synchronization holding circuit 105 is provided which maintains reception synchronization using either of the outputs 15 and 16 of 06.

That is, one of the two reference burst signals for reception synchronization is transmitted from the transmitting satellite relay device l, and the receiving terminal station 2N
The carrier wave signal received is converted to an IF level and is supplied to the demodulator 101 as an IF signal 11. Further, the carrier wave signal through which the other reference burst signal is transmitted is converted to an IF level and is supplied to the demodulator 102 as an IF signal 12. Two demodulators 101 and 102 are provided so that they can be demodulated even if the reference burst signals for reception synchronization are arranged to overlap in time. The first and second demodulated signals 13.14 demodulated by the demodulators 101.102 are sent to independent unique word detection circuits 103.104.
is input. Unique word detection circuit 103.104
A predetermined unique word in each reference burst signal is detected in the detection signal 15.
16 and is supplied to the synchronization holding circuit 105. In the synchronization holding circuit 105, reception synchronization is maintained using one of the unique word detection signals 15 and 16 of the first and second reference burst signals as a reference according to a predetermined logic.

〔Effect of the invention〕

As described above, according to the present invention, reception synchronization can be maintained even in a TDMA satellite communication network where interference waves exist. In particular, when there is an interference wave in one of the multiple carrier waves, the entire network becomes out of synchronization, and there is no need to start up the entire network from the process of establishing reception synchronization of all stations, making it possible to operate a TDMA satellite communication network. It becomes possible to carry out the process smoothly and to minimize the influence of interference waves.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a block diagram of a conventional example. FIG. 3 is a timing diagram of the arrangement of reference burst signals and control signals in a conventional example. 11...First IF multiplied signal 12...Second IF multiplied signal 13.14.25...Demodulated signal, 15...
First unique word detection signal, 16... Second unique word detection signal, 101.102.204... Demodulator, 103.104.205... Unique word detection circuit, 105.206... Synchronization holding circuit, 21a~
2In... IF double signal 22... Hopping switch control signal, 23... Burst time plan information, 24
...Selected IF multiplied signal 2G, 27...Detection signal, 201...Hopping switch, 202...Hopping switch control signal generation circuit, 203...Storage circuit, 301...First Reference burst signal, 302...
- Second reference burst signal, 303... Timing at which the first reference burst signal 301 can be received, 304...
- Timing at which the second reference burst signal 302 can be received, 310... Reference burst arrangement of TDMA frame, 311... Hopping switch control signal timing chart.

Claims (1)

[Claims] 1. It is equipped with one satellite relay device and a large number of communication terminal stations, and two of the communication terminal stations are selected as reference stations, and these two reference stations each transmit a TDMA frame. The communication terminal station includes a means for transmitting a reference burst signal within the terminal, and the two reference stations include means for controlling the timing of mutually transmitting the reference burst signal, and the communication terminal station transmits the reference burst signal which is relayed and received by the satellite relay device. In a TDMA communication system that is equipped with means for controlling the transmission timing of its own station using one of the receivable reference burst signals of two reference stations as a reference, the two reference stations transmit their respective reference burst signals using different carrier waves. A TDMA communication system, characterized in that the communication terminal station is configured to transmit, and the communication terminal station includes means for respectively extracting each reference burst signal transmitted from the two reference stations from the different carrier waves.