Channel Estimation Considerations for Iterative Decoding in Wireless Communications

The time-varying nature of wireless channels poses a challenge for using soft-decision iterative decoders on such channels. Even if the channel gain is perfectly known to the receiver, inaccurate estimation of the additive noise power, results in incorrect log-likelihood computation at the receiver and hence significant performance degradation in the decoder. Through a detailed study of the effects of channel estimation errors on the performance of soft-decision iterative decoders in uncorrelated block-fading channels, we propose a solution which does not need a knowledge of the power of the additive noise. We show that this solution performs almost identical to the case for which a perfect knowledge of the power of the additive noise exists at the receiver. The choice of the block-fading channel reflects a situation where the equivalent variance of the additive Gaussian noise can change in a wide range and thus the decoder performance seriously relies on the knowledge of the noise power at the receiver.