Soft-quantized demodulation for BPSK over discrete-time memoryless fading channel

Abstract

The demapping method that simply multiplies the received symbols with channel state information (CSI) coefficients is proved optimal in this paper for any BPSK modulated discrete-time memoryless fading channel (DMFC) from the viewpoint of channel capacity, when CSI is available at the receiver. A generic method to calculate the channel capacity of BPSK modulated DMFC subjected to uniform soft quantization is proposed, which offers a powerful criterion for optimal quantizer design. Numeric results of the Rayleigh fading case are presented, showing that 6-bit uniform quantization offers effective demodulation compared with unquantized demodulation, losing less than 0.1 dB for both with and without CSI cases.