An adaptive modulation scheme for low Earth orbit satellites

LEO satellites present widely varying signal conditions. Fixed modulation schemes are designed for the worst operating conditions and cannot take advantage of the better signal to noise conditions present at high elevations. An adaptive modulation scheme, which uses different constellation patterns with trellis coded modulation and a Reed Solomon outer code is proposed in this paper. The system is tested under AWGN noise and Rician/Rayleigh fading conditions. The system is found to provide good performance in AWGN and moderate fading conditions.