Space-time polarization diversity in multiple input multiple output communication systems

Abstract

In wireless communications systems, diversity techniques are widely used to combat the e ects of wireless fading channels. Multiple-input multiple-output (MIMO) systems have better performance under fading channels than single-input single-output (SISO) systems. In most scattering environments, antenna diversity is a practical, e ective and a widely used technique for reducing the e ect of multipath fading. Previous analyses of MIMO systems concentrate on uncorrelated antennas. However, antenna spacing and properties of scattering environment can create correlation between channel coe cients that a ects the system performance remarkably. The use of dual-polarized antennas (polarization diversity) is a cost and space e ective alternative where two spatially separated uni-polarized antennas are replaced by a single antenna structure employing orthogonal polarizations. This work presents a comprehensive analysis of MIMO systems under polarization diversity. Pairwise error probability (PEP) expressions for quasi-static fading under Rayleigh channel conditions are calculated. Then these PEP expressions are used to calculate union bounds on the performance of orthogonal space-time block code for 4Tx-2Rx MIMO system. Using polarization diversity leads to performance loss, but 2Tx-1Rx (dual polarized) MIMO system reduces to 4Tx-1Rx MIMO system which gives us advantage of having one receive uni-polarized antenna at the receiver instead of having one dual polarized antenna. Iterative detection and decoding technique for MIMO systems are focused and it is applied to 2Tx-1Rx (dual polarized) MIMO system.