The impact of a priori information on the map equalizer performance with M-PSK modulation

In this paper, we consider a transmission of M-Phase Shift Keying (M-PSK) symbols with Gray mapping over a frequency selective channel. We propose to study analytically the impact of a priori information (provided for instance by a decoder in a turbo equalizer) on the maximum a posteriori (MAP) equalizer performance. We derive analytical expressions of the bit error probability at the output of the equalizer. Simulations show that the analytical expressions approximate well the bit error rate (BER) at the output of the MAP equalizer at high signal to noise ratio (SNR).