Performance enhancement in wireless communication systems using mimo techniques

Abstract

MIMO technology offers a variety of accomplishments such as spatial multiplexing gain, diversity gain, array gain, and interference alleviation. Multi-signal transmission through diverse radio propagation environments makes the detection mechanism of primary importance, and a promising spatial multiplexing scheme which can deliver channel capacity without compromising on bandwidth and power is Vertical Bell Laboratories Layered Space-Time (V-BLAST). Nevertheless, V-BLAST is based on successive interference cancellation (SIC) and suffers from multi-stream interference (MSI) and error propagation. Initial research work is related to MIMO detectors for V-BLAST space-time coding architecture. A detailed study was done on performance comparison of different detection methods with V-BLAST to minimize MSI, under distinct radio channel impairments like fading, correlation, and keyhole effect. Error rate comparison indicates ordered-SIC with Maximum Likelihood (ML) detection most efficient for fewer antenna elements, but being an exhaustive search algorithm with exponential complexity, ML is not apt for realistic detection. Minimum Mean Square Error (MMSE) detector with ordered SIC balance the bit error rate (BER) and complexity in combating MSI. But under the right channel conditions, it is suggested to employ Zero-forcing (ZF) precoding as a scalable and low complexity solution. v Fading and keyhole effect has a detrimental impact on channel matrix, reducing the channel capacity, as indicated by the quantitative analysis done with the ZF scheme. Chapter 3 details the study and results thus obtained. As MIMO is progressing towards Massive-MIMO with more than ten times increase in number of transmitting antenna, this low complexity ZF detector is attracting research attention.