Nonlinear Predistortion for OFDM SDMA Systems

This paper investigates nonlinear predistortion techniques for the downlink of OFDM systems from a transmitter equipped with multiple antennas to non-cooperative single antenna mobile stations. Although the performance of nonlinear predistortion schemes like Tomlinson Harashima precoding (THP) strongly depends on the ordering of the precoded symbols, current THP approaches apply data independent sorting algorithms. A tree search algorithm is proposed which combines matrix decomposition and the feedback structure of the precoder to compute a data dependent precoding order