Channel precoding using phase distortion for slowly fading channels

The bit error rate (BER) of a mobile or personal digital communications system at a high bit rate can be significantly increased by intersymbol interference (ISI) due to multipath propagation. Using traditional precoding techniques, the amplitude of transmitted signals cannot be kept constant due to amplitude predistortion. To improve the frequency spectrum efficiency, a new precoding method is investigated. Only the phase of the signal carrier is predistorted at the transmitter of the base station, and the signal received at the portable unit is ISI free. The information of the received signal amplitude is used for detection. Computer simulation results demonstrate that, over a two-path Rician fading channel, differential QPSK with precoding has significantly lower BER values than those with a conventional decision feedback equalizer (DFE) since the precoder is not subject to error propagation