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.