The optimal received power distribution for IC-based iterative multiuser joint decoders

Abstract

We use the large-system Density Evolution (DE) analysis of iterative InterferenceCancellation (IC) multiuser detection/decoding as a tool for optimizing the received SNR distribution. We show that the SNR distribution achieving maximum possible spectral eAEciency for a given code and target bit-error rate (BER) can be obtained by linear programming. We show that large spectral eAEciencies and low BER are achievable by very simple standard convolutional codes and QPSK modulation, provided that the SNR distribution is appropriately optimized.