Impact of spatial correlation towards the performance of MIMO downlink transmissions

There are two known MIMO transmission scheme in the wireless link-level research: Space-Time Coding (STC) and Spatial Multiplexing (SM). STC aims to achieve maximum antenna diversity and improve wireless link reliability, while SM, on the other hand provides a capability for increasing the data rate by higher spectral efficiencies, i.e. more bits/s/Hz of bandwidth. Most MIMO simulations consider ideal transmission spatial subchannels condition, whereby the fading correlation between each spatial subchannel is uncorrected with uniform Rayleigh´s distribution. However, in a more realistic propagation environment, spatial correlation does exist between antenna pairs and affects the MIMO transmission link, resulting in reduced capacity and loss of Bits Error Rate (BER). The main aim of this paper is to investigate the effect of spatial interference due to spatially correlated MIMO subchannels by employing a dynamic subcarrier allocation, based on the Orthogonal Frequency Division Multiple Access (OFDMA) transmission scheme. Focus is given in the downlink path, since the Mobile Station (MS) is expected to benefit from the rich multiuser diversity gain given from the dynamic subcarrier allocation. From the simulation results, the BER performance between both the STC and SM scheme will be analyzed to further understand the limitation in transmission under different spatial correlation.