PHASE PRECEDING FOR FREQUENCY-SELECTIVE RAYLEIGH AND RICIAN SLOWLY FADING CHANNELS

This paper presents a novel phase preceding (pre-equalization) techniq ue to equalize frequency-selective Rayleigh and Rician slowly fading c hannels for personal communication systems using phase modulation, In order to achieve intersymbol interference (ISI)-free transmission, the preceding technique pre-distorts the signal transmitted from a base s tation to a portable unit, The novelty of the technique lies in using a spiral curve design: 1) to ensure the stability of the precoder even in equalizing a non minimum-phase channel; 2) to obtain an ISI-free r eceived signal; and 3) to keep a constant transmitted signal amplitude , Using the precoder can improve the bit-error-rate (BER) transmission performance without increasing the complexity of the portable unit re ceiver, The BER performance of coherent quadrature phase-shift-keying (QPSK) with the channel pre-equalization is analyzed theoretically for both Rayleigh and Rician fading channels, Analytical and simulation r esults demonstrate that coherent QPSK using the proposed channel preco der has a significantly lower BER than that using a conventional decis ion-feedback equalizer (DFE) because the precoder does not suffer from error propagation.