A novel signaling scheme is proposed for iterative channel estimation and data decoding in fast fading channels. The basic idea is to bias the occurrence probability of transmitted symbols. A priori information about the bias is utilized for channel estimation. The bias-based scheme is constructed as a serially concatenated code, in which a convolutional code and a biased nonlinear block code are used as the outer and inner codes, respectively. This construction allows the receiver to estimate channel state information (CSI) efficiently. The proposed scheme is numerically shown to outperform conventional pilot-based schemes in terms of spectral efficiency for moderately fast fading channels.

This letter proposes a robust detection scheme of orthogonal space-time block codes that face very fast fading channels. The proposed detection scheme employs a QR decomposition on the channel matrix and minimizes noise enhancement and impact of channel estimation errors which occur in a conventional detection scheme. It is shown by simulations that the proposed detection scheme outperforms the conventional detection scheme when the channel fading is very fast.

The design criteria for space-time trellis codes (STTC's) in fast fading channels have been proposed: the Distance Criterion and the Product Criterion. The design criteria in [1] are based on optimizing the pairwise error probability (PWEP). However, the frame error rate (FER) of STTC's depends on the distance spectrum. In this paper, we propose a new design criterion for STTC's based on the distance spectrum in fast fading channels. The proposed design criterion is based on the product distance distribution for the large signal-to-noise ratio (SNR) and the trace distribution for the small SNR, respectively. Moreover, we propose new STTC's by the computer search based on the proposed design criterion in fast fading channels. By computer simulation, we show that the proposed design criterion is more useful than the Product Criterion in [1] in fast fading channels. We also show that the proposed STTC's achieve better FER than the conventional STTC's in fast fading channels.