Mutual Information and Bit Error Rate Analysis of MIMO System Under Correlated Fading Channel

Abstract

Multiple Input Multiple Output (MIMO) wireless links has recently emerged as one of the most significant technical breakthrough in modern communication. In this thesis, an overview of MIMO system has been discussed. After presenting brief idea of MIMO transmissions in the introduction, the system Capacity and Bit Error Rate of MIMO designs have been explained. MIMO system with multiple transmitter and receiver antennas have been recognized as the vital breakthrough for wireless system to achieve higher data rates and improved quality of service with limited bandwidth and power resources in influence of multipath fading. On the other hand, traditionally, multiple antennas have been used to increase diversity for combating channel fading. Hence, MIMO system emerges out as the solution for spatial multiplexing, capacity and bit error rate. Wireless relaying networks have recently been given considerable attention due to their various advantages over traditional communication system. The relaying terminals forward the information from the source to the destination mainly using the well-known method Amplify-Forward since MIMO systems can provide better system capacity than SISO, SIMO and MISO systems. MIMO relays aim to provide improved system capacity, increases in range, and better diversity gain. In this thesis the ergodic capacity of an AF MIMO two-hop system under Rayleigh fading channel has been analyzed and compared with earlier techniques of MIMO system. The main contribution of this work is to derive an exact expression for an AF MIMO two-hop system capacity and cumulant function of Mutual Information. The expression derived is unified, and it can be used for arbitrary numbers of antennas at the source, relay and destination. The simulation results have been presented to validate the analysis. Mutual information has shown improvement up to 30% in the capacity as compared to the MIMO system implemented without AF. Further the capacity benefits of MIMO system under Rician fading channel have been presented. Here, in this thesis slow and frequency nonselective Rician fading channel is used for analyzing, the effect of Rician factor (K) and correlation parameter (rr) for the capacity of correlated MIMO channels. From the comparison it has been found that the outage capacity is higher than the ergodic capacity. From the study and simulation result presented in this thesis, it has been observed that by increasing the number of antennas of MIMO system and with increase in signal to noise ratio the capacity of MIMO system degrades; when observed for different Rician factor coefficient. The bit error rate analysis of MIMO system have been analyzed using BPSK modulation scheme over Rayleigh and Rician wireless fading channels. The BER performance characteristics investigation of 2x2 antenna configuration has done by using different type of linear and non-linear equalizer techniques namely ML, ZF and MMSE for MIMO system. The bit error rate characteristics for the two transmitting and two receiving antenna has been simulated. By comparing the Rayleigh and Rician fading simulation result it has been observed that there has been improvement in bit error rate up to 35% for ML detection, up to 24% in ZF detection and up to 18% in MMSE detection technique by keeping BER∿〖10〗^(-4) with respect to SNR under Rician fading channel. Finally, the result achieved in this thesis have been compared with the BER produced on MIMO system by using IEEE802.11n protocol as benchmark, the significant improvement in BER for each technique have been achieved as compared to BER achieved from IEEE802.11n standard and reported in this thesis. The simulation result have shown that ZF equalizer based receiver remove inter symbol interference much better as compared to the receivers implemented using ML and MMSE based equalizer. Whereas MMSE based equalizer found to be robust even in presence of channel nulls and noise because of its property directly minimizing the bit error rate.