Multiple Input Multiple Output System with Space Time Block Coding and Orthogonal Frequency Division Multiplexing

Problem statement: A large amount of research has been performed to achieve very high data rate networks to support reliable transmission of video, data and speech at high rates to many users. One way to increase the data rate in a wireless system is to use multiple transmit and/or receive antennas (MIMO structure). Indeed, it has been shown that the Shannon capacity of MIMO channel is (if the channel is known to the receiver) grows linearly with the number of transmit antennas and the number of receive antennas. MIMO systems can be implemented using various types of pre coding and modulation technique. All leads to get better signal at the receiver. Approach: Large scale fading due to multipath propagation of wireless signals can be mitigated by deploying multiple antennas both at the transmitter and the receiver. MIMO systems can be implemented using many techniques. Here at the transmitter the signals are coded using space time block codes and then they are modulated using Orthogonal Frequency Division Multiplexing (OFDM). Due to this the received signal can have an improved SNR. Results: The results are obtained for simple STBC-MIMO system, when it implemented for various number pf transmit and receive antennas. The resultant SNR and BER were obtained through simulation. Then the same system was deployed using OFDM technique. The results were compared for simple MIMO-OFDM and coded MIMO-OFDM. Conclusion/Recommendations: The complexity increases for higher data rate because of using both coding and modulation technique. By using proper mapping technique before deployment on the transmit antennas the complexity may be reduced. The OFDM technique can be improved to give high SNR by properly coding it like a CDMA process.