Trellis Frequency and Phase Modulation in Fading Mobile Satellite Channels

Abstract

Most satellite communication systems are power and bandwidth-limited. In band limited nonlinear satellite applications, various researchers have shown that respectable coding gains can be achieved by Ungerboeck TCM ( trellis coded modulation ) codes [1], which improve error performance without reducing data rates or requiring more bandwidth than conventional uncoded schemes. This is achieved by channel coding with expanded sets of multilevel phase signals, such that the free Euclidean distance is maximized. A coded modulation format is defined over an expanded set of signals varying both in frequency and phase modulation ( FPM ). This special technique combines Frequency Shift Keying ( FSK ) and Phase Shift Keying ( PSK ) modulations. The FPM signal has been transmitted through nonlinear satellite transponder which exhibits amplitude and phase distortion ( AM/AM and AM/PM ), respectively, [2]. The TCM / FPM schemes demonstrate improved performance over TCM / MPSK systems on AWGN and the fading channels.