| 摘要 |
PROBLEM TO BE SOLVED: To provide a time delay diversity/site diversity method capable of increasing a line availability ratio, and drastically decreasing an entrance line cost.SOLUTION: A method uses a configuration in which two earth stations 46 and 47 are located not at the same location but with a distance of 3 to 5 km apart each other. The method includes: if rain attenuation 45 above an earth station becomes large and exceeds a threshold value of C/N required in the system, changing an operation mode thereof to an SD method mode to enhance a line availability ratio; if the rain attenuation increases further and the SD method cannot secure communications, activating a TDD method, causing two repeaters on a satellite 41 to transmit a real time signal and delayed signals 61, 62, 63, and 64, which are delayed from the real time signal by (t1-t2); operating a delay circuit in the earth station for delaying the real time signal by (t1-t2) to align the timing to the delayed signals; and causing a level determination circuit to control so as to receive a signal with the maximum signal strength among the four signals to secure communications under larger rain attenuation. |
