Maximum-Likelihood Priority-First Search Decodable Codes for Combined Channel Estimation and Error Protection

Abstract: The code that combines channel estimation and error protection has received general attention recently, and has been considered a promising methodology to compensate multi-path fading effect. It has been shown by simulations that such code design can considerably improve the system performance over the conventional design with separate channel estimation and error protection modules under the same code rate. Nevertheless, the major obstacle that prevents from the practice of the codes is that the existing codes are mostly searched by computers, and hence exhibit no good structure for efficient decoding. Hence, the time-consuming exhaustive search becomes the only decoding choice, and the decoding complexity increases dramatically with the codeword length. In this paper, by optimizing the signal-tonoise ratio, we found a systematic construction for the codes for combined channel estimation and error protection, and confirmed its equivalence in performance to the computer-searched codes by simulations. Moreover, the structural codes that we construct by rules can now be maximum-likelihoodly decodable in terms of a newly derived recursive metric for use of the priority-first search decoding algorithm. Thus,the decoding complexity reduces significantly when compared with that of the exhaustive decoder. The extension code design for fast-fading channels is also presented. Simulations conclude that our constructed extension code is robust in performance even if the coherent period is shorter than the codeword length.