JPS583613B2 - Satellite communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a satellite communication system in which spatial propagation loss includes variable factors such as rain attenuation, and transmit waves from one or more pairs of opposing earth stations are amplified by one repeater. In particular, the present invention relates to an earth station transmission power control method that effectively utilizes the transmission power of a satellite repeater by changing the transmission power of each station in accordance with fluctuations in propagation loss.

Conventionally, satellite communications have been carried out in the microwave band, where there is little rainfall attenuation and propagation loss hardly changes, so even when several waves are amplified by one satellite repeater, the transmission output of each earth station is fixed. It was decided that there was no need to change it.

In recent years, frequency bands higher than the microwave band are being used for satellite communications, but propagation loss fluctuates due to rain attenuation in frequency bands higher than the microwave band.

If the transmission power of each earth station is increased to cope with rain attenuation, the level diagram of each wave cannot always be optimized if several waves are commonly amplified by one repeater.

For this reason, in satellite communications that use frequencies higher than microwaves, a method can be considered to optimize the output of the satellite repeater by changing the transmission power of the earth station depending on the propagation state.

One method is to control the transmission power of each earth station so that the received input level from each earth station is constant at the input of the satellite repeater. Only link attenuation compensation, no downlink compensation.

Another method is to collect information on rainfall attenuation at each station at a specific control station, use a computer at the control station to determine the optimal transmission power for each station, and control the transmission power at each station via a control line to each station.

In this case, a specific control station is required, and a line for transmitting the rain attenuation of each station to the control station and a line for controlling the transmission power of each station are also required.

As a way to deal with these problems, one of the inventors of the present invention has already proposed a satellite communication system that controls transmission power using line S/N, which represents the quality of the satellite line.
(Refer to Publication No.-24422).

However, in this method, the transmission power of the main earth station is controlled in communication between the main earth station and the slave earth station, so that the line S/N from the master earth station to the slave earth station and from the slave earth station to the master earth station is equal. However, control of the transmitting power of the slave earth station was not taken into account.

This is because a small earth station was assumed to be the main earth station and a large earth station as the slave earth station, and application to communication between small earth stations was not considered.

In the case of communication between small earth stations, it is necessary to control the transmission power of both earth stations, but it is simply necessary to control the line quality in both directions (
If the transmission power of each earth station is controlled so as to equalize the signal-to-noise ratio (S/N), there is a risk that the control will not converge.

The present invention provides a method for transmitting signals from each station so that the line quality between each station always matches a certain reference value when a single satellite repeater commonly amplifies communication signals between one or more pairs of earth stations facing each other. By controlling power, we have developed a satellite communication system that can easily optimize the line settings of the entire satellite communication system, where there are fluctuation factors in propagation loss, and significantly reduce the line unavailability of each communication line. This is what we provide.

The present invention will be explained in detail below using the drawings.

FIG. 1 shows an example of the configuration of a satellite communication line to which the present invention is applied, in which 1 represents one satellite repeater, and 2 represents each earth station that accesses it.

The figure shows a case where three sets of communications, AB, CD, and EF, are amplified by one repeater 1.

Among these, communication between station A and station B will be explained as an example.

It is assumed that the output of the satellite repeater 1 increases monotonically with respect to the input.

It is also assumed that each group of communication is assigned its own dedicated frequency.

At this time, if the transmission power of station A is increased, the line quality from A to B will improve, and the commonly amplified B→A and C D
, the line quality of E■F deteriorates slightly.

Conversely, if the transmission power of station B is increased, the line quality from B to A will improve, but the line quality from A to B, C and D, and E4+F will slightly deteriorate.

Each communication line is a bidirectional line, and considering the above-mentioned line properties, it can be seen that the optimum line setting is when the line quality from A to B and from B to A is equal.

This kind of line setting is possible by changing the transmission power of stations A and B, but if a reference value for line quality to be made equal is given, it is possible to set the line quality based on the bidirectional line quality measured at station A or B. It is possible to control the transmission power of its own station and make the bidirectional line quality match the standard value.

The procedure for transmitting power control in each station will be described below, taking station A as an example.

First, all stations, including station A, can always know the line quality from their own station to their own station and from their partner station to their own station by a method described later.

Line quality is represented by S/N, and the line quality of A → B and B → A is S/NA → B, S/NB → A, and the standard line quality is S/N0. /NA
→B, S/NB→A is (i) S/NA→B>S/NB→A, then S/NB
→ If A>S/N0, reduce the transmit power of station A, and increase the transmit power of station B if S/NB→A<S/N0.

(ii) If S/NA→B<S/NB→A, S/N
If A→B<S/N0, the transmit power of station B is reduced, and if S/NA→B<S/N0, the transmit power of station A is increased.

If the transmission power control of such a procedure is performed at the A station and the B station, the bidirectional line quality can be made to match the reference value S/N0.

FIG. 2 shows an example in which the line S/N measurement channel (pilot) is placed on the baseband, and FIG. 3 shows the configuration of each station at that time.

In this embodiment, on the transmitting side, a transmitting baseband unit 11 combines the multiplex telephone signal input and pilots 1 and 2 and applies it to a modulator 10 whose output is an upconverter 9.
The signal is frequency-converted and sent to the antenna 18 via the transmitter 8.

On the receiving side, the output of the antenna 18 is received by the receiver 12, frequency-converted by the down converter 13, demodulated by the demodulator 14, and converted into multiplex telephone output and pilot 1 and pilot 2 by the receiving baseband unit 15. To separate.

16 is a pilot detection filter that operates as a line quality detection circuit, and 17 is a control logic circuit for S/N detection and transmission power control.

In FIG. 2, 3 is a multiplex telephone signal to be transmitted, 4 and 5 are pilots 1 to be sent out, and pilots 2, 6, and 7 are pilots 1 and 2 to be received.

Among the pilots to be sent out, pilot 1 is a pilot sent out from the own station, and pilot 2 is a pilot sent out from the other station and received by the own station, and is returned to the other station as shown in FIG.

Among the received pilots, pilot 1 is a pilot sent from the own station and returned by the partner station, and pilot 2 is a pilot sent out from the partner station.

Among the received pilots, from pilot 1 to own station →
Since the line quality from the other station to the own station is known, and the line quality from the other station to the own station can be determined from the pilot 2, the control logic circuit 17
Now, you can use these to measure the line quality in both directions from the other station to your own station, and based on this, follow the steps above to make sure that the line quality in both directions reaches the reference value S/NO. Controls the transmission power of the transmitter 8.

In this way, the quality of the communication line between each station is matched to a certain standard value, but if this standard value is always selected so that the total output of the satellite repeater is at the maximum allowable level,
It becomes possible to constantly optimize the line settings of the entire communication system, and the downtime rate of each station can be significantly improved.

As explained above, according to the present invention, when a single satellite repeater commonly amplifies communication signals between one or more pairs of opposing earth stations, the line quality between each earth station can be made equal. If the transmission power of each earth station is controlled, the satellite repeater will have enough margin for normal communication, so the margin should be allocated for rain attenuation at any one station. This has the effect of significantly reducing the downtime rate of communication between each station as a whole.

In addition, according to the method of the present invention, if an appropriate value is given as the standard value of line quality in accordance with the propagation state at that time, 1
By controlling the transmission power of each station accessing the same repeater while checking the line quality with the other station, it is possible to set the optimum line level diagram as a whole.

Furthermore, the present invention controls the line quality (S/N) in both directions so that it converges to a certain reference value, and there is no risk of divergence even if the transmission power of each communicating earth station is controlled. do not have.

Therefore, it is also applicable to communication between small earth stations.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing the configuration of a satellite communication system to which the present invention is applied, Fig. 2 is a diagram showing a signal arrangement used in the present invention, and Fig. 3 is an example of the configuration of an earth station when implementing the present invention. FIG. 1...Satellite repeater, 2...Earth station, 3
...Multiple telephone signal, 4...Transmission pilot 1, 5...Transmission pilot 2, 6...
...Receive pilot 1, 7...゜Receive pilot 2, 8...Transmitter, 9...Up converter, 10...Modulator, 11... ...Transmission baseband unit, 12 ...Receiver, 1
3... Down converter, 14... Demodulator, 15... Receiving paceband unit, 1
6...Pilot detection filter, 17...
...Control logic circuit for S/N detection and transmission power control.

Claims (1)

[Claims] 1. When a single repeater of a communication satellite commonly amplifies communication signals between one or more pairs of opposing earth stations, the transmission power of each earth station is adjusted between the opposing earth stations. A satellite communication system characterized by controlling all the lines so that the line quality matches a predetermined reference value. 2 Two channels for line quality measurement are provided in the communication line between each pair of earth stations among the pair or pairs of earth stations facing each other, and one channel is used for measuring the line quality from the other station to the local station. In addition, the other channel is used to measure the line quality of the return line from the local station to the local station via the other station, and the two-way communication from the local station to the other station and from the other station to the local station obtained by this measurement. 2. The satellite communication system according to claim 1, wherein transmission power is controlled at the local station and the other station so that the line quality always matches the predetermined reference value. 3. The satellite according to claim 1 or 2, wherein the reference value is selected so that the total output of the repeater is always constant, so that the entire communication between each station is always optimized. Communication method.