This paper presents a way to maximize transmission efficiency and reception ability through transmission diversity technology, which can be adapted to wireless multimedia OFDM system. The presented method is a comparative analysis between a case where parameter ${alpha}$ for time average is 0.3, 1 with consideration of channel presumption with two types of rms delayed spread, which is 50nsec, 150nsec, for the performance analysis of STTC(Space-Time Trellis Code) using time-space ciphering method appropriate for MIMO channel, and performance in the case where presumed channel value from long training column section is applied to according frame in a single frame. The result showed that BER brought SNR improvement of 1.0 dB in $10^{-3}$ when ${alpha}$ was 0.3 than using only the long training column, and showed increase of general performance improvement for the sake of time average rather than the case without.