JPS61184012A - Transmission power control system - Google Patents

Abstract

PURPOSE:To attain proper control of transmission power by estimating directly the attenuation from a ground transmitter to a satellite. CONSTITUTION:A transmission system device 1 inputs a signal whose amplitude changes stepwise to an amplitude modulator AM and a carrier is subject to amplitude modulation and sent from a transmission system antenna A to an antenna B on a satellite. The signal received by the antenna B is irradiated from an antenna C via a repeater 3 and received by an antenna D of the ground reception system. The output of the antenna D is detected and demodulated by the detector DET of the reception system device 2. The detection output of the detector DET is fed to a controller system device 4. The control system device 4 counts number of stages of change in the amplitude of the detected output, estimates the attenuation from the transmission system device 1 to the repeater 3 depending on the step number and the transmission power of the transmission system device 1 is controlled depending on the attenuator. Thus, the transmission power is controlled properly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a transmission power control method for controlling transmission power in accordance with changes in attenuation of a propagation path in a wireless communication system.

SUMMARY OF THE INVENTION The present invention applies stepwise or temporally varying amplitude modulation to a transmitted signal, transmits the signal, receives the amplitude-limited signal via a repeater, and adjusts the amplitude change of the received signal. This is a transmission power control method that estimates the amount of attenuation from the transmitter to the repeater based on the number of steps or time, and controls the transmission power according to the estimated amount of attenuation. Appropriate transmission power control can be performed by directly understanding the amount of attenuation between the transmitting device and the repeater without being affected by the amount of attenuation from the repeater to the receiving device.

Prior Art For example, in satellite communications, etc., in order to reduce the deviation of the received electric field of each radio channel received by the satellite, the transmission power from the ground is controlled according to the amount of attenuation in the uplink from the transmitter to the satellite. There is a need to. Since it is not possible to directly measure the attenuation from the ground transmitter to the satellite, conventional methods have been to estimate the attenuation of the uplink from the attenuation of the downlink from the satellite to the ground, or to estimate the attenuation of the uplink from the attenuation of the downlink from the satellite to the ground. The amount of attenuation is estimated.

In the former, a signal of a certain level is sent from the satellite to a transmitting station, and the signal is received at the transmitting station to measure the attenuation of the downlink, but generally the frequencies used for the upstream and downlink are different. Therefore, there is a drawback that the amount of attenuation in the uplink cannot be accurately estimated from the amount of attenuation in the downlink.

The latter estimates the attenuation of the uplink by comparing the C/N of the satellite return C18, and the C/N of the beacon wave etc. from the satellite, but the measurement signal such as the beacon wave is different from the actual control signal. It is difficult to estimate accurate attenuation because it differs from the frequency.
Another disadvantage is that the measurement system becomes complicated. Furthermore, T
When a large number of earth stations are accessing using the DMA method, etc., it is necessary to transmit beacon waves of a certain level to each earth station, which deteriorates the efficiency of frequency use and reduces the frequency on the satellite. The disadvantage is that the device is also complicated.

There is also a method that sends the satellite's reception input level to the earth station as a telemetry signal, but the equipment on the satellite is complicated and the TD
In the MA method and the like, the frequency usage efficiency deteriorates.

Problems to be Solved by the Invention The present invention does not require any complicated equipment on the satellite, and can directly calculate the amount of attenuation from the ground transmitting device to the satellite without being affected by the amount of attenuation from the satellite to the ground receiving device. By easily and accurately estimating the transmission power, it is possible to accurately control the transmission power.

Structure of the Invention The transmission power control method of the present invention is a wireless communication system in which a transmission signal from a transmitter is transmitted to a receiver via a repeater having an amplitude limiting characteristic. The receiver includes an amplitude modulator that performs amplitude modulation, and the receiving device includes a detector that detects changes in the amplitude of the received signal whose amplitude has been limited by the repeater. It is characterized by controlling transmission power accordingly.

Embodiments of the Invention Next, the present invention will be described in detail with reference to one drawing.

FIG. 1 is a block diagram showing one embodiment of the present invention.

That is, the transmission system device 1 inputs a signal whose amplitude changes stepwise to the amplitude modulator AM, and the amplitude modulator AM modulates the amplitude of the carrier wave using the signal to transmit the signal from the transmission system antenna A to the antenna B on the satellite. Send. The signal received by antenna B is limited to a certain level by repeater 3, and then emitted from antenna C and sent to antenna D of the terrestrial reception system.
received at The output of the antenna D is detected and demodulated by the detector DET of the receiving system device 2. The detection output of the detector DET is input to the control system device 4. The control system device 4 is
The number of steps in which the amplitude of the detection output changes is counted, the amount of attenuation from the transmission system device 1 to the repeater 3 is estimated based on the number of steps, and the transmission power of the transmission system device 1 is controlled according to the amount of attenuation.

FIG. 2(A) shows the carrier wave level transmitted from antenna A, increasing in stages. Figure CB) shows the input signal to the repeater 3 when the amount of attenuation between the transmitting system antenna A and the satellite antenna 3 is small. When the amplitude is limited by the device 3, the signal becomes a signal limited to a constant level as shown in FIG. 2(C). In this case, the signal is limited to an intermediate level between the fourth step and the fifth step, and steps beyond that are eliminated, resulting in a five-step signal.

On the other hand, when the attenuation between antenna A and antenna B is large, the received signal of antenna B is as shown in (D) of the same figure.
The signal becomes a low-level signal, and the output of the repeater 3 becomes as shown in FIG. 3(E) without being amplitude limited by the repeater 3.

The number of steps in this case is six.

The output of the repeater 3 is radiated into space through the antenna C and received by the antenna D of the terrestrial reception system. The amount of attenuation in the downlink between the satellite and the receiving system antenna 0 changes due to rain, etc., but since it is a linear space, the amplitude modulation waveform of the signal does not change. Therefore, if the received signal is AM detected by the detector DET, The waveforms shown in FIG. 2(C) or (E) can be extracted.

Therefore, the control system device 4 controls the repeater 3 by counting the number of steps of the signal input from the detector DET.
Since it is possible to estimate the input level of , the transmission power of the transmission system device l is controlled accordingly.

In addition to the methods described above, various methods of applying amplitude modulation can be considered. For example, as shown in FIG. 4(A), an amplitude-modulated pulse signal may be used to count the number of pulses until an amplitude change occurs;
As shown in B), a signal whose amplitude is increased at a constant slope is sent immediately after the reference pulse, and the input level of repeater 3 is estimated by measuring the time T from the reference point to the saturation point of the received signal. You may also do so.

In this embodiment, by installing the transmitting/receiving system devices 1 and 2 and the control system device 4 at the same ground station, the transmission level can be controlled by easily estimating the amount of attenuation of each uplink at each scattered ground station. By doing so, it is possible to keep the satellite input level constant. Therefore, inter-channel interference can be reduced, channel frequencies can be arranged densely, and frequencies can be used effectively.

Effects of the Invention As described above, in the present invention, a carrier wave that changes stepwise or temporally is transmitted, and the receiving device side detects the amplitude-limited received signal via a repeater to determine the amplitude of the received signal. Since the input level of the repeater is estimated based on the number of change steps, etc., the transmission power can be accurately controlled without being affected by changes in attenuation between the repeater and the receiving device. be.

When applied to satellite communications, it is possible to control the transmission power of the uplink from the earth station to the satellite, reduce interference between adjacent channels due to deviations in the satellite input level, and make the frequency allocation between channels denser. Therefore, there are effects such as being able to use frequencies effectively.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing an example of each part signal of the above embodiment, FIG. 3 is a diagram showing input/output characteristics of the repeater of the above embodiment, and FIG. 4 is a diagram showing various examples of amplitude modulation. In the figure, 1: transmission system device, 2: reception system device, 3: repeater, 4: control system device, A: transmission system antenna, B, C: satellite antenna, D = reception system antenna, AM: amplitude modulation. Detector, DET: Detector.

Claims (1)

[Claims] In a wireless communication system in which a transmission signal from a transmitter is transmitted to a receiver via a repeater having amplitude limiting characteristics, the transmitter has amplitude modulation that changes stepwise or temporally on a carrier wave. The receiver is equipped with a detector for detecting changes in the amplitude of the received signal whose amplitude has been limited by the repeater, and the receiver is equipped with a detector for detecting changes in the amplitude of the received signal whose amplitude has been limited by the repeater. A transmission power control method characterized by controlling transmission power.