System-level performance evaluation of MMSE MIMO turbo equalization techniques using measurement data

In this paper, system-level performance of three different MMSE turbo MIMO equalization techniques is evaluated in realistic scenarios. Soft cancellation and minimum mean squared error filtering (SC/MMSE) turbo equalization and its complexity reduced version, turbo equalized diversity, is considered. Furthermore, another version of equalized diversity, turbo equalized diversity with common SC/MMSE, which exploits the transmit diversity and coding gain through the cross-wise iterations over the decoding branches, is evaluated. The multi-dimensional channel sounding measurement data used for the simulations consists of snapshots measured in different channel conditions in terms of spatial and temporal properties. The system-level assessment is in terms of outage probabilities of the performance figures such as bit and frame error rates obtained by evaluating their cumulative probability densities as well as throughput efficiencies using the field measurement data. It is found that the receivers considered in this paper can all provide reasonable system-level performance. However, turbo equalized diversity receiver is more sensitive to the channel conditions than the original SC/MMSE equalizer. It is also found that the performance gain, obtained from the cross-wise iteration over the decoding branches in the turbo equalized diversity with common SC/MMSE technique, is significant.