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

TL;DR

This paper introduces a systematic, structurally designed code for combined channel estimation and error protection that is efficiently decodable using maximum-likelihood priority-first search, improving over previous computer-searched codes.

Contribution

It proposes a new code construction method that achieves performance comparable to computer-searched codes and enables efficient maximum-likelihood decoding with reduced complexity.

Findings

Codes perform as well as computer-searched codes in simulations.

Decoding complexity is significantly reduced with the proposed structure.

Extension codes are robust in fast-fading channels even with short coherent periods.

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.