Performance analysis of Adaptive Switching Between Space-Time and Space-Frequency Block Coded OFDM Systems using ZF and MMSE techniques

This paper focuses on the implementation and performance analysis of adaptive switching between STBC and SFBC OFDM systems [1].Here in this paper we proposed an adaptive transmission technique for MIMO OFDM systems using adaptive equalization algorithms (ZF,MMSE) where the channel response are unknown a priori and time variant. In this paper two selection criteria, correlation of the channel and magnitude of the interference, are proposed for transmission mode selection . In criterion I, correlation between successive OFDM symbols for STBCOFDM and correlation between neighboring subcarriers for SFBC-OFDM are compared and the mode which has higher correlation value is selected to maximize the SNR. Next, in criterion II, we choose the mode which has smaller Inter symbol Interference to reduce the performance degradation. Simulation results show that the proposed adaptive switching system shows better performance with ZF and MMSE equalizers[8]. keywords – space-time code (STC), MIMOOFDM systems, adaptive switching, Zero forcing, Minimum mean square error. .