CAREER: Design and Analysis of Iteratively Decodable Codes for Wireless Communications and Digital Magnetic Recording

Texas A&M Engineering Experiment Station, College Station TX

Investigators

Abstract

Future generation wireless systems and data storage systems will certainly take advantage of the recent developments in coding theory and signal processing. In the last decade, concatenated coding and iterative processing have emerged as powerful paradigms in coding theory and signal processing. Both wireless communications and magnetic recording systems place particular constraints and limitations. In wireless communications, maintaining high power and spectral efficiency is key. In addition, in some systems, it may be necessary to maintain a constant envelope for the transmitted signals. Digital magnetic recording systems can tolerate very little redundancy and require very low end to end bit error rates. It is crucial to develop an understanding of the potential and limitations of concatenated coding and iterative processing for use in these systems. While exact analysis of concatenated codes with iterative decoding is difficult, a recently proposed technique called density evolution is a powerful tool that permits analysis of iterative decoding and offers considerable insight. Using this technique or, a variation thereof, this research aims at furthering the design and analysis of iteratively decodable codes with applications to wireless communications systems and digital magnetic recording systems. This research emphasizes two main ideas - irregular codes and the design of codes matched to iterative decoding. Based on these ideas, three specific areas are addressed. They are 1) Design and analysis of irregular parallel and serial concatenated codes including non-binary codes and irregular turbo trellis coded modulation, 2) A comprehensive study of concatenated coding and decoding strategies for modulators with memory (such as CPM), their performance analysis for AWGN, flat Rayleigh fading and inter-symbol interference channels, 3) Design and analysis of codes for digital magnetic recording - particular emphasis is given to the design of concatenated codes in the presence of an outer Reed-Solomon code, evaluating novel high rate codes and on low complexity receiver structures when the overall desired bit error rates are of the order of 10^{-15}.