Design of Space Time Trellis Coded OFDM


Space Time Trellis Code (STTC) is a technique that can be used to improve the performance of the Orthogonal Frequency Division Multiplexing (OFDM) system over wireless channels by providing both coding gain and diversity gain. STTC is combined from two codes, Trellis Code Modulation (TCM) as an inner code and Space Time Block Code (STBC) as an outer code. TCM which combines the choice of a modulation scheme with that of a convolutional code provides the coding gain, and the other code provides the diversity gain. Simulation is done over flat fading and frequency selective Rayleigh fading channel for Eight Phase Shift Keying (8-PSK) TCM. It found that the best results are obtained for the case of two transmitters and three receivers which have a gain of about 18dB over that without STBC.