A single user MIMO system using Tomlinson-Harashima precoding with adaptive bit allocation

To develop reliable communication systems, we propose a single user multiple-input multiple-output communication system using zero-forcing (ZF) Tomlinson-Harashima precoding (THP) with adaptive bit allocation. Eigenbeam space division multiplexing (E-SDM), which utilizes a singular-value decomposition (SVD) and a water filling technique, is known to be an optimal linear precoding MIMO scheme. However, the SVD of a MIMO channel matrix requires a heavy computational cost. On the other hand, the ZF-THP is a non-linear precoding scheme which is computationally efficient while showing allowable bit error rate (BER) performance. In order to improve further in terms of the BER, we propose to allocate bits adaptively to minimize the upper-bound of the theoretical BER for every transmission in a fading environment. Numerical examples provide a comparison with the E-SDM method.