On the benefits of pilot-aided MAP receivers over differential PSK

This paper considers new maximum a posteriori (MAP) receivers for phase-shift keyed (PSK) digital mobile communication systems. The focus is on the benefits of pilot-aided PSK over differential PSK (DPSK) when using these receivers in fast fading channel conditions. For fading channels, DPSK is typically employed in preference to PSK because it avoids the need for accurate channel tracking. However, for both the PSK and DPSK MAP receivers considered here, non-coherent quadrature analog front-ends are used, with channel estimation being performed digitally in conjunction with data estimation. Channel estimates are formed along each branch of an expanded MAP trellis. In the case of absolutely encoded PSK, phase ambiguity is resolved using pilot symbols. For the new MAP receivers, the choice between PSK and DPSK is no longer clear. This paper shows that pilot-aided PSK outperforms DPSK for these new receivers, despite the SNR penalty associated with pilot symbols. From a computational point of view however, the new MAP DPSK receiver developed in this paper is more efficient.