JPS63173426A - Transmission power control equipment - Google Patents

Abstract

PURPOSE:To attain transmission power control with high reliability by measuring a bit error rate of its own station transmission burst so as to estimate the change in the attenuation in the transmission line so as to control the transmission power so that the bit error rate is always at a prescribed level in a time division multiplex multiple access satellite communication system. CONSTITUTION:Since a carrier to noise ratio (C/N) and a bit error rate (BER) on a satellite line correspond to each other, the C/N of its own station loopback is measured by measuring the BER. The measurement of BER is simply realized by applying again error correction coding to an output data of an error correction decoder 11 and comparing the result with an input data of the error correction decoder 11 in a bit error rate measuring device 12. The deterioration of the C/N estimated by the measurement of BER is used and the quantity of rainfall attenuation is shared to the incoming/outgoing links depending on the carrier frequency of the incoming and outgoing links of the satellite line, then the share corresponding to the attenuation of the incoming link is controlled by the variable attenuator 7 to increase the transmission power for the transmission power control.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a time division multiple access (TDMA) satellite communication system in which the attenuation of radio waves due to causes such as rain is compensated for by increasing the transmission power at the transmitting earth station. This invention relates to a transmission power control device that attempts to compensate by

[Conventional technology]

Figure 4 shows, for example, the Radio Research Institute Quarterly Report vol. 1.32 Special 3 (1
This shows the transmission power control method discussed on pages 33 to 35 (January 1986). In the figure, ■ indicates the satellite,
2 is an earth station transmitting/receiving antenna, 3 is a transmitting/receiving branching filter, 4 is a beacon receiver that receives a beacon signal from the satellite 1, 5 is a received power detection circuit, 6 is a transmitting power amplifier, 7 is a variable attenuator, 8 is a This is a transmission signal input to this variable attenuator 7.

Next, the operation will be explained. The satellite 1 normally has a function of generating and transmitting a beacon signal so that the antenna 2 of the earth station can correctly track the direction of the satellite 1. This beacon signal undergoes attenuation corresponding to the attenuation of radio waves due to rain or the like in the propagation path between the satellite 1 and the earth station antenna 2, and is received by the beacon receiver 4 via the transmitter/receiver splitter 3. The amount of attenuation described above is detected by the received power detection circuit 5.

Assuming that the attenuation in the propagation path is only due to rain, it is known that there is a certain relationship between the amount of attenuation and its frequency. Therefore, the frequency of the beacon signal is fb,
Assuming that the frequency of the carrier wave transmitted from the earth station toward the satellite 1 is fu, if the attenuation amount Lb at fb is measured, this can be converted into the attenuation amount Lu at the frequency fU.

Therefore, if the variable attenuator 7 is controlled by the reception power detection circuit 5 and the attenuation amount corresponding to Lu is set to be small, the output of the transmission power amplifier 6 will increase by Lu, and the difference between the satellite 1 and the earth station will be reduced. Attenuation due to rainfall 1. Even if u exists, the power reaching the satellite 1 is the same as when there is no attenuation due to rain, and the operation as a transmission power control loop is completed.

[Problem that the invention seeks to solve]

However, it is generally difficult to control the output power of the beacon oscillator mounted on satellite 1 to a constant level because satellite 1 exists in space, and the problem is that it is difficult to perform highly reliable transmission power control. was there.

The present invention solves the above-mentioned problems, and aims to provide a transmission power control device that can achieve highly reliable transmission power control without using external equipment such as a satellite beacon oscillator. It is said that

[Means for solving problems]

The transmission power control device according to the present invention includes a propagation loss means that measures the bit error rate of a transmission burst of its own station by utilizing a decoding process of an error correction code and estimates a change in attenuation in a propagation path; and power control means for controlling transmission power so that the bit error rate is always at a constant level according to the estimation result.

[Effect]

In this invention, the bit error rate of the transmission burst of the own station is measured in order to estimate the propagation loss, and it is assumed that the change (deterioration) in the bit error rate is due to the change (deterioration) in the amount of attenuation in the propagation path. The bit error rate is estimated and the transmission power is controlled so that the bit error rate is always at a constant level.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 2, 3, 6, and 7 are equivalent to the corresponding parts in FIG. 9 is a receiver that receives the reception burst from the satellite including its own transmission carrier; 10 is a demodulator that demodulates the reception burst and converts the digital data into '1fitM; 11 is the error correction coded fj[digital data]; A decoder performs decoding, 12 is a device for measuring the bit error rate occurring in the satellite line, and 13 is a synchronization control section of the TDMA terminal station. Further, 14 is an error correction encoder, 15 is a modulator that modulates a carrier wave according to digital data to be transmitted, and 16 is digital data 1 to be transferred to and from the ground side.
This is a demultiplexing section that performs multiplexing and demultiplexing of 7 and 1 demultiplexing.

Next, the operation will be explained. Here, the arrangement of bursts at the input section of the receiving device 90 is illustrated in FIG. Same figure (
In al, 18.20 shows a burst transmitted from another earth station, and 19 shows a state in which a transmitted burst from the own station is received. When there is rain near one's own earth station and the carrier wave burst is attenuated, as shown in FIG. The signal will be received at a lower level corresponding to the amount of attenuation in the uplink from the station to the satellite.

Next, considering the carrier noise ratio (C/N ratio) for the local burst 19 or 19a, 19a has a lower C/N ratio than 19. The C/N ratio and the bit error rate (BER) on the fr star line are correlated as shown in Figure 3, so by measuring the BER, it is possible to measure the ClN ratio of the local return loop. . Here B
In the measurement of ER, it can be assumed that the output data of the error correction decoder 11 is correct data after error correction. This can be easily realized by comparing with the input data of the correction decoder 11.

BER using real traffic data like this
For example, the time required to measure a BER of 10-4, which is normally set as the threshold BER, at a data rate of IMbit/sec is less than 1 second.

In this way, it is possible to divide the amount of rain attenuation into the uplink and downlink according to the carrier frequency of the uplink and downlink of the satellite link using the deterioration amount of the C/N ratio estimated by the ER measurement. Therefore, by controlling the variable attenuator 7 by an amount corresponding to the uplink attenuation amount, it becomes possible to control the transmission power to increase the transmission power.

〔Effect of the invention〕

As described above, according to the present invention, the C/N ratio is determined by measuring the BER using actual traffic data, and the transmission power is controlled accordingly. This has the advantage that it is possible to perform more reliable control, and also to perform transmission power control using an inexpensive device even for small earth stations that do not require a beacon receiver.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a transmission power control device according to an embodiment of the present invention, FIG. 2 (ia) (b) is a diagram showing the power level of a received burst, and FIG. FIG. 4 is a diagram showing the configuration of a conventional transmission power control device using beacon waves. 2...Earth station transmitting/receiving antenna, 6...Transmission power amplifier, 7...Variable attenuator, 9...Receiver, 11...
Decoder, 12...Bit error rate measuring device, 14...
Error correction encoder. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (3)

[Claims] (1) In a time division multiplex multiple access satellite communication system in which an error correction code is applied to traffic data, a bit error rate measuring device is provided to measure the bit error rate of a received burst from data before and after error correction decoding processing; a propagation loss estimating means for estimating a change in the amount of loss in a propagation path between a satellite and an earth station due to rain etc. by receiving a burst transmitted by itself and measuring the bit error rate of the received burst; 1. A transmission power control device comprising: power control means for controlling burst transmission power of an earth station so that the power reaching a satellite is constant according to the transmission power. (2) The bit error rate measurement device measures the bit error rate of the received burst by comparing the data obtained by re-encoding the output data of the error correction decoder with the input data of the error correction decoder. The transmission power control device according to claim 1, characterized in that: (3) The transmission power control device according to claim 1 or 2, wherein the power control means is a variable attenuator.