PRAGMATIC PERFORMANCE OF TC8PSK IN RICIAN FADING CHANNELS

This paper analyzes performances of trellis coded(TC) 8PSK modulation in Rician fading channels to optimize parameters of Viterbi decoders. The computer simulation clarifies that when carrier power to multipath power ratio (C/M) equals 10 dB, P(e) performance with reasonable length interleaving depends on free Euclidean distance (d(free)) but not on effective code length (ECL) in a practical range of bit error probability (P(e) = 10(-3)-10(-4)). In the case of C/M = 5 dB, the effect of ECL appears in the range of bit energy to noise power density ratio (E(b)/N(o)) >> C/M (= 5dB). Therefore, for domestic mobile satellite communication systems for non-high latitude countries, only d(free) must be considered for TC8PSK Viterbi decoder design. Moreover, to improve P(e) performance in slow fading environment, pre-Viterbi-decoding maximal ratio combining is proposed. The proposed diversity scheme improves required E(b)/N(o) to achieve P(e) = 10(-4) by more than 6 dB compared with no interleaving and more than 2.5 dB compared with interleaving.