An adaptive modulation precoding scheme for mean BER minimisation of ISI MIMO channels

This paper considers a non-linear precoding scheme with adaptive bit loading in order to minimise the average BER for a given target data rate when transmitting over a frequency-selective (FS) multiple-input multiple output (MIMO) channel. The proposed design utilises a recently developed polynomial singular value decomposition (PSVD) to decouple the FS MIMO channel into a number of independent FS single input single output (SISO) subchannels, whereby spectral majorisation inherent on the PSVD leads to a natural ordering of channel gains. The latter is exploited to adaptively allocated the transmission bits to the resulting FS SISO subchannels according to their SNRs. Simulation results show that BER performance can be enhanced for different data rate targets compared to a previously proposed heuristic method as well as to uniform bit loading.