JPH0356020B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is a transmission power control satellite communication system, in particular, a time division multiple access (TDMA) system operated at a frequency such as a sub-millimeter wave band where rain attenuation cannot be ignored. This invention relates to a transmission power control satellite communication system that controls the transmission power of an earth station to keep the effective radiated power (EIRP) approximately constant.

Satellite communications using high frequency bands such as the sub-millimeter wave band are subject to significant attenuation due to rainfall, and countermeasures are required to counter this. For the downlink, a method is generally used in which the earth station receiving device is provided with enough margin to compensate for attenuation, and a site diversity method is adopted if necessary. On the other hand, for the uplink, which generally uses a higher frequency than the downlink and has greater rainfall attenuation, transmitting from the earth station with a constant power with a margin will cause negative effects due to saturation of the satellite repeater on clear days. It happens.
Therefore, apart from the site diversity method, satellite repeaters are capable of controlling the transmitting power of the earth station in response to rainfall attenuation in the uplink and keeping the satellite repeater output, that is, the satellite's EIRP, approximately constant. This method can be said to be desirable from the viewpoint of effective use of output. Even with the high-speed TDMA method, which transmits one carrier with one repeater on a satellite, the effects of saturation are alleviated compared to frequency division multiple access (FDMA) methods, but excessive saturation is undesirable. With the expansion of applications, low- and medium-speed
In the TDMA system, transmission power control is an important technical measure from the standpoint of effective use of satellite repeaters.

As a transmission power control method symmetrical to the FDMA method and FM modulated waves, for example, 1981 Institute of Electronics and Communication Engineers General National Conference Preliminary Paper No. S10-11 "Quasi-millimeter-wave vehicle-mounted station communication method" (pages 8-293, 294) ) and Paper No. 182, ``Compensation method for uplink rain attenuation of BS main station'' (page 182), a preview of the 1973 National Conference of the Optical and Radio Division of the Institute of Electronics and Communication Engineers, was published, but the former was It was devised with a focus on operation between stations and is not suitable for operation with multiple stations, and it also has the disadvantage of using a dedicated channel for control. The first latter method detects the received power on the satellite side and sends it back on a telemeter signal, which requires special equipment in advance on the satellite side and is particularly inappropriate for multi-station operation. The second method is to receive the continuous waves that are transmitted by the own station and reflected back by the satellite, and then calculate the amount of uplink attenuation by using the correlation between the uplink frequency and the downlink frequency's rain attenuation based on the level drop. Although this is an effective method that estimates and controls the transmission power to compensate for this, it is not necessarily the best method for each TDMA earth station to adopt a similar method.

An object of the present invention is to provide a transmission power control satellite communication system that does not require a dedicated frequency or special equipment on the satellite side to control the transmission power of an earth station, and is suitable for the TDMA system operated by multiple stations. It is.

A first aspect of the present invention is a satellite communication system in which a reference station and a plurality of non-reference stations communicate via a satellite in the TDMA method, in which the reference station uses a beacon signal emitted from the satellite and a beacon signal transmitted from the reference station to the satellite. By comparing the reception level or carrier-to-noise power ratio (C/N) with the reference station burst signal returned by the reference station burst signal and controlling the transmission power of the reference station burst signal, fluctuations in the EIRP of the reference station burst signal at the satellite are controlled. Transmission power control means, comprising compensation means for compensating, and controlling the transmission power of the data burst so that the reception level of the burst signal from the non-reference station or the reference station matches the reception level of the data burst transmitted from the local station and reflected by the satellite. It is constructed by having the following.

A second invention of the present invention is based on the above-mentioned first invention, when the reception level of the reference station burst signal transmitted from the reference station itself and returned by the satellite decreases from a predetermined normal value. comprising compensation means for compensating for fluctuations in the EIRP of the reference station burst signal in the satellite by controlling the transmission power of the reference station burst signal to be increased by a predetermined amount in response to the .

Next, the present invention will be explained in detail with reference to the drawings.
FIG. 1 is a system configuration diagram of an embodiment of the first aspect of the present invention, and FIG. 2 is a frame configuration diagram of a TDMA signal. In the figure, 1 is a satellite, 2 is a reference station, and 3 is a satellite.
~5 is a non-reference station, and reference station 2 has a frame length τ
A reference station burst signal consisting of a reference burst 6 for frame synchronization of the TDMA signal of The received levels of the beacon signal fb, which is transmitted at a constant output from 1 to 1, are compared, and the transmission power is controlled so that the ratio is constant. There is a considerable difference in attenuation due to rain between uplink and downlink frequencies, but beacon signals in the same downlink frequency band and downlink
It shows almost the same attenuation as the TDMA wave. Therefore, if the reception level ratio of the two is kept constant, the ratio of the EIRP of the two on the satellite will also be kept constant, and since the beacon wave EIRP is always constant regardless of rain or shine, the reference station transmitted from the reference station 2 It is clear that the burst signal satellite EIRP is also controlled to be constant by compensating for fluctuations due to uplink rain attenuation. Non-reference stations 3, 4, and 5 send data bursts 8 and 8 to their assigned time slots, respectively.
9 and 10, and the transmission power of each data burst is controlled so that the return reception level matches the reception level of the reference station burst signal transmitted by the reference station 2. With this configuration, the satellite EIRP of the data burst sent by each non-reference station will be the same as the EIRP of the reference station burst signal, and all bursts of TDMA waves will always be at the same level regardless of rain attenuation, making the satellite repeater always optimal. It can be used in the following conditions.

FIG. 3 is a block diagram of an embodiment of the reference station 2 in FIG. 1, in which 20 is a shared transmitting and receiving antenna, 21 is a low noise amplifier, 22 is a down converter that converts the received TDMA wave to an intermediate frequency, and 23 is a beacon signal converter. Convert and amplify to intermediate frequency and receive level output 10
2, a beacon receiver 24 extracts and detects only the reference station burst signal from the TDMA wave output of the down converter, and outputs its reception level 102.
A reference station burst signal detector 25 compares the reception level outputs 101 and 102 of the beacon and the reference station burst signal, and if the ratio of the reference station burst signal to the beacon reception level is larger than a predetermined ratio, the transmission power a comparator that generates a control signal 103 that controls the variable attenuator 26 to decrease the transmission power and increase the transmission power if it is small; 27 is an up converter that converts the intermediate frequency signal to a transmission frequency; 28 is a transmission power amplifier; Reference numeral 29 denotes a TDMA transmitter/receiver, which is configured to open and close the extraction gate of the reference station burst signal detector 24 in response to a gate pulse 104 sent from its synchronization control circuit. Comparator 2 mentioned above
5, if the beacon receiver 23 and the reference station burst signal detector 24 are configured to have a linear output variation with respect to the decibel input within the input signal variation range, the difference between the inputs 101 and 102 is a constant value. The configuration may be such that positive and negative control signals are generated based on the comparison.

FIG. 4 is a block diagram of an embodiment of a non-reference station.
Antenna 30, low noise amplifier 31, down converter 32, own station data burst detector 33 that extracts own station data burst and detects its return reception level, reference station burst signal detector 34, own station data burst detector 33 and reference station. A comparator 35 that compares the output of the burst signal detector 34 and sends out a control signal to control the data burst transmission power so that the outputs of the burst signal detector 34 are equal, a variable attenuator 36, an up converter 37, a transmission power amplifier 38, and TDMA.
The TDMA transmitter/receiver 39 is configured to open and close the extraction gates of the local station data burst detector 33 and the reference station burst signal detector 34, respectively, in response to gate pulses from the synchronization control circuit of the TDMA transmitter/receiver 39.

In the above embodiment, the reference station burst signal to be compared with the beacon signal is composed of the reference burst 6 and the data burst 7 for frame synchronization, but it may be only the reference burst 6 or the data burst 7, and the reference station may be used for frame synchronization. There is no problem even if it is an earth station that does not transmit a reference berth. or,
Although the embodiment is configured to compare the received levels of the beacon signal and the reference station burst signal, C/N may be compared instead of the received levels. C/
Comparing N and controlling the transmission power so that it is a constant value is important because there is no uplink noise contribution to the beacon signal, so the satellite of the reference station burst signal
Although it does not result in a constant control of EIRP, it does significantly compensate for EIRP fluctuations since the uplink noise contribution is generally much smaller than the downlink. In order to further reduce this residual fluctuation due to uplink noise, instead of controlling the C/N ratio to a constant value, it is also possible to perform correction control so that the C/N ratio changes slightly depending on the reception level. can. The use of C/N has the advantage of easing the requirement for gain stability of the receiving device. In the example, we have explained the normal TDMA method in which each earth station transmits data verses in a predetermined time slot, but the same applies to the DAMA method TDMA in which the time slot is not fixed to each station but is assigned according to the request. The following method can be applied. Furthermore, the EIRP fluctuation compensation effect of this method is not only due to rain attenuation, but also applies to EIRP fluctuations caused by other causes, and when multiple carriers share a satellite repeater, the level fluctuations of other carriers are This is also effective when the effective gain of the repeater varies depending on the situation.

The configuration of the earth station is not limited to that shown in Figures 3 and 4; the variable attenuator may be an amplifier with gain control, and even if the variable attenuator is not in the intermediate frequency band but in the high frequency band after the up converter. good. Furthermore, the input/output characteristics of the receiving system and the configuration of the comparator shown in FIG. 3 are not limited to those described above.

A second invention of the present invention is that in the first invention described above, the configuration of the reference station is changed from that shown in FIG. 3 by removing the beacon receiver 23 and replacing the comparator 25 with a control signal generator. It is composed of It is recognized that there is a correlation between uplink and downlink rain attenuation, and when the attenuation is expressed in decibels, there is a nearly linear proportional relationship between the two.
Therefore, if the downlink rain attenuation amount is xdB, it is estimated that the uplink attenuation amount is αxdB. If the transmission power is controlled to increase αxdB when the reference station burst signal output decreases by xdB from the value under clear weather, uplink attenuation can be compensated for and the satellite EIRP can be maintained approximately constant.
This method does not require a beacon receiver for the reference station and is simple, but there is residual variation in EIRP due to variations in individual rainfall phenomena from the average, and although the EIRP variation is larger than in the first invention, the range of variation is significantly reduced. It has the effect of reducing

As explained in detail above, according to the present invention, there is no need for a dedicated frequency or special equipment on the satellite side for controlling the transmission power of the earth station, and the equipment for a large number of non-reference stations is simple and suitable for the TDMA system. It is possible to provide a transmission power control satellite communication system that allows efficient use of satellite repeater power.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the first invention of the present invention, FIG. 2 is a flair configuration diagram of a TDMA signal, FIG. 3 is a block diagram of an embodiment of the reference station of the first invention, and FIG. FIG. 4 is a block diagram of one embodiment of a non-reference station. 1... Satellite, 2... Reference station, 3, 4, 5... Non-reference station, 6... Reference burst, 7, 8, 9, 10
...Data burst, 20,30...Antenna,
21, 31...Low noise amplifier, 22, 32...Down converter, 23...Beacon receiver, 2
4, 34... reference station burst signal detector, 25,
35... Comparator, 26, 36... Variable attenuator, 2
7, 37... Up converter, 28, 38...
Transmission power amplifier, 29, 39...TDMA transmitting/receiving device, 33... Own station data burst detector.

Claims (1)

[Claims] 1. In a satellite communication system in which a reference station and a plurality of non-reference stations communicate via a satellite in a time division multiple access method, the reference station transmits a beacon signal emitted from the satellite and a beacon signal sent from the reference station. Compensating for fluctuations in the effective radiated power of the reference station burst signal at the satellite by comparing the reception level or carrier-to-noise power ratio with the reference station burst signal reflected by the satellite and controlling the transmission power of the reference station burst signal. and a transmission power control means for controlling the transmission power of the data burst so that the non-reference station has a reception level of the reference station burst signal and the data burst transmitted from its own station and reflected by the satellite. A transmission power control satellite communication system characterized by: 2. In a satellite communication system in which a reference station and a plurality of non-reference stations communicate via a satellite in a time division multiple access method, the reception level of the reference station burst signal transmitted from the reference station and returned by the satellite is a predetermined normal level. Compensation for compensating for fluctuations in the effective radiated power of the reference station burst signal in the satellite by controlling the transmission power of the reference station burst signal to be increased by a predetermined amount in response to the amount of decrease when the power decreases below the value. and a transmission power control means for controlling the transmission power of the data burst so that the non-reference station has a reception level of the reference station burst signal and the data burst transmitted from its own station and looped back by the satellite. A transmission power control satellite communication system characterized by: