JPH0612885B2 - TDMA transmission synchronization control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a transmission synchronization control method in a slave station of a time division multiple access (hereinafter referred to as TDMA) satellite communication system, and particularly, to a slave station transmission burst timing in steady synchronization control. Control method for determining.

[Conventional technology]

The TDMA satellite communication system is a communication system in which a plurality of satellite communication earth stations share one satellite repeater in a time division manner to communicate with each other. In this communication system, even if the satellite used is a geostationary satellite, the influence of slight relative position fluctuations with each earth station cannot be avoided.

FIG. 2 is a conceptual diagram of a frame format of TDMA satellite communication, and shows a temporal arrangement when a signal transmitted from each station takes time on the horizontal axis and passes through a satellite repeater.

This arrangement is repeated with the TDMA frame as one cycle.
The signals transmitted from each station are transmitted in the form of intermittent signals called bursts, and at the input of the satellite repeater, burst-like signals arriving from each earth station must be controlled so that they do not overlap each other. In FIG. 2, A is called a reference burst and contains a synchronization signal which is a reference of a TDMA frame. This reference burst is transmitted from a reference station selected from a large number of stations participating in the communication system.
B, B ′, B ″ ... Denote burst signals transmitted from each station, and C is a time slot assigned to another station which is not currently transmitting.

The relative position variation between the satellite and each earth station appears as a variation in the radio wave propagation time between each station and the satellite. Therefore, in order to correct this fluctuation, once synchronization is established, each earth station needs the following frame synchronization and burst synchronization. That is, by comparing the local synchronization signal received through the satellite repeater with the allocated time position for the local synchronization signal in the received frame, and correcting the transmission timing momentarily to eliminate the error, the correct timing is always obtained. Control is required to reach the satellite repeater input.

Regarding transmission burst synchronization, it is currently roughly classified,
It is roughly divided into an open loop method and a closed loop method, but in order to maintain burst synchronization accurately,
The Claude loop method is often used. There are two methods in the closed loop method. The first method is a loopback control method using a satellite return signal of a burst signal transmitted by the own station, and the concept is shown in FIG. The second method is a reference station feedback control method. As shown in FIG. 4, this feedback control method measures the synchronization error of the local station transmission burst signal by the reference station or the monitoring station via the satellite, and the error The information is transmitted again to the slave station via the satellite, and the slave station controls the transmission timing according to the reference station measurement synchronization error information. Currently, these two methods are used properly according to each system.

[Problems to be solved by the invention]

In the loopback control method, all processing relating to transmission timing control can be performed by the slave station, so the control function of the reference station can be simplified. However, since the own station transmit signal is re-received by satellite loopback, when operating in the Ku or Ka band frequency band, signal degradation due to rainfall attenuation is affected simultaneously from the uplink and downlink, and the transmission synchronization control retention characteristics deteriorate. There is a drawback that

On the other hand, in the feedback control method by the reference station, it is necessary to measure the synchronization error for all slave stations and transmit the error information to all slave stations. Therefore, the control function of the reference station becomes complicated, and the transmission channel capacity for transmitting the synchronization error information to all slave stations must be secured. Therefore, a considerably complicated control function is required for the reference station, and the circuit is required. It has the drawback of being complicated.

The present invention is intended to eliminate the above drawbacks.

[Means for solving problems]

The present invention relates to a transmission timing control method in a time division multiple access (TDMA) communication method for satellite communication, in which a reference station measures burst position error of a slave station and outputs reference station measurement burst position error information and an error of the slave station. When the error rate reaches a predetermined value, the reference station measuring burst position error information is transmitted to the corresponding slave station, and the slave station measures the burst position error of its own station and the own station. Error rate measuring means and means for selecting and outputting either the reference station measured burst position error information from the reference station or the burst position error information of the own station according to the error rate and the output of the selecting means. And means for controlling the transmission timing of its own station.

[Work]

The transmission synchronization control method according to the present invention controls the transmission timing by the self-station measured burst position error information when the self-station reception synchronization signal by the satellite loopback is normally received in the slave station, while the satellite loopback When the local station reception synchronization signal is no longer received normally, the transmission timing control is performed by switching and selecting to the reference station measurement burst position error information measured by the reference station. At this time,
To measure the burst position error of the corresponding slave station at the reference station, the bit error rates of the received reference station signal and the slave station signal are measured, and the error rate of the received slave station signal falls below a certain reference level compared to the error rate of the reference station signal. When there is a deterioration, the burst error information of the reference station measurement burst is transmitted to the corresponding slave station via satellite. That is, since the reference station measurement burst position error information transmitted from the reference station is only for the specified slave station among all the slave stations, the reference station function and the transmission channel capacity required for the control are the same as those of the conventional reference station feedback control method. Compared to this, the number can be greatly reduced, and the entire system can be simplified.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.

In the slave station ES ₁ , the own station burst position error measuring circuit 11 detects the own station measured burst position error information using the received frame synchronization signal and the own station reception synchronization signal. The selection circuit 12 selects one of the self-station measured burst position error information and the reference-station measured burst position error information transmitted from the reference station ES ₂ , and the transmission timing control circuit 13 determines the slave station transmission burst timing. Selection circuit 1
The determination criterion of No. 2 is based on the determination result of the determination circuit 15 based on the error rates of the reception reference station signal and the reception own station signal measured by the error rate measurement circuit 14.

On the other hand, the reference station ES ₂ also includes a slave station burst position error measuring circuit 21, a transmission control circuit 22, an error rate measuring circuit 23, and a judging circuit 24, as in the slave station ES ₁ . When the error rate of the received slave station signal falls below a certain standard, the transmission control circuit 22 transmits burst position error information to the slave station based on the output of the determination circuit 24.

〔The invention's effect〕

As described above, according to the present invention, the slave station performs transmission timing control of its own station while selecting both the loopback control method of the own station and the feedback control method of the reference station, thereby reducing the reception level due to rainfall. The transmission timing control can be stably maintained, and the circuit scale and the transmission channel capacity for controlling the slave station transmission timing of the reference station can be greatly reduced compared to the conventional method.

[Brief description of drawings]

FIG. 1 is a second embodiment of the TDMA transmission synchronization control system of the present invention.
FIG. 4 shows an example of a TDMA frame burst structure, FIG. 3 shows an example of a conventional loopback control method, and FIG. 4 shows an example of a conventional reference station feedback control method. In the figure, ES ₁ is a slave station, ES ₂ is a reference station, and SS is a satellite.

Claims (1)

[Claims] 1. In a transmission timing control system in a time division multiple access (TDMA) communication system for satellite communication, a reference station measures a burst position error of a slave station and outputs reference station measured burst position error information. When the error rate reaches a predetermined value, the reference station measurement burst position error information is transmitted to the corresponding slave station, and the slave station measures the burst position error of its own station. Based on the error rate measuring means of the station, the means for selecting and outputting either the reference station measured burst position error information from the reference station or the burst position error information of the own station according to the error rate, and the output of the selecting means. And a means for controlling the transmission timing of its own station.