Signal sending and receiving method for low-orbit constellation communication

The invention discloses a signal sending and receiving method for low-orbit constellation communication; the method comprises the steps: carrying out the OFDM conversion of different symbols needing to be sent based on a transmitting end, and obtaining corresponding OFDM symbols, wherein each antenna circularly samples the same OFDM symbol according to a preset rule to obtain a cyclic displacement form; adding the cyclic shift form into a cyclic prefix to obtain an MMDM space-time coding matrix, wherein the MMDM space-time coding matrix is combined with a low-orbit satellite multi-antenna system to send the same satellite signals with different delays; receiving the signals and separating the same satellite signals with different delays to obtain signals of each path; carrying out doppler frequency shift and time delay estimation and compensation are on signals of all paths, and acquiring all satellite signals through demodulation. According to the method, the problem that the channel capacity of an MIMO syst