Lower bounds on the performance of the map equalizer with a priori over mimo systems

In this paper, we consider a transmission of quadrature phase shift keying (QPSK) symbols over a frequency selective multiple input multiple output (MIMO) 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 tight lower bounds on 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.