Multilevel concatenated-coded M-DPSK modulation schemes for the shadowed mobile satellite communication channel

This paper presents a bandwidth-efficient multilevel concatenated-coded modulation scheme for reliable data transmission over the shadowed mobile satellite communication (MSAT) channel. In this scheme, bandwidth-efficient block modulation codes are used as the inner codes, and Reed-Solomon codes of various error correcting capabilities are used as the outer codes. The inner and outer codes are concatenated in multiple levels. A general method for constructing multilevel concatenated modulation codes is presented, and a multistage closest coset decoding for these codes is proposed. Specific multilevel concatenated 8-PSK modulation codes have been constructed. These codes are designed to lower the bit error rate (BER) of the error floor caused by the large Doppler frequency shift due to the motion of vehicles. Simulation results show that these codes perform very well and achieve large coding gains over the uncoded reference modulation systems.