Cascaded tomlinson harashima precoding and block diagonalization for multi-user MIMO

We propose and evaluate the performance of a cascaded THP and BD system (THP-BD) for a MIMO downlink in which BD is used to mitigate multi-user interference and THP is used to mitigate spatial interference. We show that at moderate to high SNR, the cascaded THP-BD system achieves the same error performance as the system employing THP on a multi-user MIMO (MU-MIMO) downlink. Also, symbol error rate (SER) of the THP-BD precoding technique is at least 3 dB better than a linear precoding scheme when perfect CSIT is available. We also evaluate the performance of this scheme for channels with noisy feedback and with temporal correlation. Significantly, we find that while THP is sensitive to temporal correlation of the channel, THP-BD is more resilient.