MIMO OFDM Space Time Coding - Spatial Multiplexing Increasing Performance and Spectral Efficiency in Wireless Systems

OFDM is a multicarrier modulation technique in which a high rate bit stream is split into N parallel bit-streams of lower rate and each of these are modulated using one of N orthogonal sub-carriers. OFDM is robust to multi-paths fading and delay because it has high data transmission capability with high bandwidth efficiency that's why it has recently been applied in wireless communication systems. It is highly sensitive to frequency offset introduced by the wireless channels and causes loss of orthogonality and amplitude reduction of OFDM signal and lead to Inter Carrier Interference (ICI). There are two deleterious effects caused by frequency offset one is the reduction of signal amplitude in the output of the filters matched to each of the carriers and the second is introduction of ICI from the other carriers a main problem in OFDM is its vulnerability to frequency offset errors due to which the orthogonality is destroyed that result in Inter carrier Interference (ICI). ICI causes power leakage among subcarriers thus degrading the system performance. This paper studies ICI cancellation scheme in MIMO-Ofdm which performs better than standard OFDM system. Later we proposed Self cancellation method in MIMO OFDM to enhance the performance of the system by reducing the BER for different values of signal to noise ratio (SNR).