OFDM Demodulation Using Receive Signal Combining for Massive GW Satellite MIMO With Small Antennas

The LEO satellite constellation is one of the most promising non-terrestrial network (NTN) systems for super coverage extension. Since future LEO systems will be required to provide terrestrial mobile services with higher than the current data rates, they need to accommodate significantly more terminals than conventional satellite-dedicated communication systems. Moreover, to establish robust backhauls for satellite mobile services, they must be able to achieve a large capacity feeder link. We previously investigated a Massive GW satellite MIMO system comprising many GW antennas distributed over a wide area that cooperate to achieve high capacity. In the current work, we propose an OFDM demodulation scheme to reduce the computational complexity for downlink transmission in this system. Our demodulation scheme combines the received OFDM signals before synchronization and demodulates them as a pseudo-multipath channel received signal. Simulation results show that the proposed scheme can reduce the computational complexity of MIMO demodulation to about 20% while keeping the required SNR degradation at about 1–2 dB. We also evaluated the relationship between the signal combining method and CP length and found that using group combining (which combines nearby receiving antennas) improves the frame utilization efficiency by about 1.12 times and increases the channel capacity compared to using scattered combining (which combines distributed receiving antennas).