Proceedings of the 5 th ICEENG Conference, 16-18 May, 2006 CO - 10 - ١ Military Technical College Kobry El-kobbah, Cairo, Egypt 5 th International Conference on Electrical Engineering ICEENG 2006 PERFORMANCE ANALYSIS OF TRELLIS CODED MODULATION SCHEMES WITH ASYMMETRIC QPSK IN LAND MOBILE SATELLITE FADING CHANNELS Salah EL-Agooz * , Gamal Mabrouk Abdel-Hamid * , and Amru Hassan Hafez * ABSTRACT This paper is concerned with evaluating the performance of trellis coded modulation schemes with asymmetric QPSK when transmitted through a land mobile satellite channel. The channel exhibits fading and shadowing as well as additive white Gaussian noise. Fading and shadowing cause both envelope and phase variations of the received signal. However, it is assumed that the effect of the fading on the phase of received signal is fully compensated using a pilot tone calibration technique. The paper provides an upper bound of pairwise error probability of TCM schemes with both asymmetric and symmetric QPSK modulations. Numerical results show that TCM with asymmetric QPSK provides better performance in terms of bit error probability over TCM with symmetric constellations in Nakagami-m distribution fading channel. KEY WORDS Trellis coded modulation, Land mobile satellite fading channel, Asymmetric QPSK constellation. І. INTRODUCTION Trellis coded modulation (TCM) scheme achieves good power and bandwidth efficiencies for additive white Gaussian noise (AWGN) channel. In the recent years, TCM has increasingly been used in mobile radio and indoor wireless channels, which are often modeled as fading channels. In a bandwidth limited environments, increasing efficiency in frequency utilization can be obtained by choosing higher order modulation schemes however, larger signal power would be needed. Therefore, if a well chosen code can be combined with bandwidth efficient scheme, e.g. Mary PSK, the bandwidth expansion results from coding can be compensated by bandwidth reduction results from the Mary PSK modulation. Furthermore, the coded system allows a reduction in the required signal power by an amount equal to the coding gain, which allows overcoming the increased power required by using the Mary PSK modulation scheme. Performance analysis for trellis-coded M-any phase shift keying (MPSK) and M-any continuous phase frequency shift keying (CPFSK) operating on fading land mobile satellite channel have been presented in [2]and[3]. A complete analysis of TCM for the ideally interleaved Rician fading channel with coherent or differentially coherent detection