Turbo decoders which adapt to noise distribution mismatch

This article investigates the sensitivity of turbo decoder performance to mismatch of the noise distribution, and proposes a simple on-line procedure for estimating the unknown noise distribution from each block of received signal. This procedure consists of: (1) quantization of the received signal and (2) estimation of the noise distribution from the histogram of the quantized received signal. For Gaussian and Laplacian noise, the proposed procedure leads to decoder performances which are comparable (within 0.1 dB at bit-error rate of 10/sup -4/) to the case where the noise distribution is known exactly.