| 摘要 |
PROBLEM TO BE SOLVED: To easily and correctly supervise transmission quality at a receiving station in a satellite communication system which digitizes a video signal and transmits and receives it. SOLUTION: In a transmitting station 1, a code generator 107 sends a test signal, together with a main signal and a synthesizer 105 synthesizes them and transmits them. A receiver 112 receives the test signal that returns from a satellite station 3, and a demodulator 111 demodulates it and calculates its BER(bit error rate). A transmitting power variable device 109 controls transmitting power of the test signal, so that a calculated value may be a fixed value that has been preliminarily defined. At the same time, the fixed value is added to the test signal and sent. In a receiving station 2, a separator 202 separates the test signal from the fixed value information, a bit error rate calculator 207 calculates the BER of the test signal, the calculated value is compared with the fixed value and an alarm is generated based on the compared result. In this case, as for a fixed value, even if the state of a transmission path is satisfactory, the value is preliminarily selected so that a BER can easily be calculated. |
