Fragiacomo, Simon; (1997) Developments in channel coding for error and spectral control. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

This thesis is concerned with channel coding. Channel coding consists of error control coding and line coding (LC). The basic definitions and concepts of both error correcting codes (ECCs) and LC are initially examined, followed by the presentation of a number of existing coding algorithms. Where appropriate, computer simulation is used to establish their limitations. Certain new codes are then devised which offer improved performance. Finally, following on what is now an established trend, error correcting and line codes are combined to form error correcting line codes (ECLCs), which may offer superior performance compared to the use of a cascaded scheme. Specifically, the first chapter contains some basic definitions, the thesis outline and a summary of the contributions. Chapter 2 introduces the basic concepts behind error correcting codes and soft decision decoding (SDD) together with a brief description of the well-established Chase algorithms. Their advantages and limitations will be examined and used to generate novel SDD algorithms in chapter 5. The basic concepts of line coding are introduced in chapter 3. In addition, a new family of single added bit line codes is also presented. This offers reasonably good line characteristics with very small compromise to rate. Chapter 4 is concerned with simulation as a means of evaluating the performance of coded systems. A conventional simulation technique is initially presented and used for assessing the performance of BCH codes. This proves inadequate for simulating the very low error rates of modern communication systems, especially when SDD is used. Two novel simulation acceleration algorithms are therefore introduced to alleviate this problem. These will only simulate code words that affect the residual bit error rate (RBER) and simply calculate the effects of the code words which are correctly decoded. The novel simulator algorithms are used in subsequent chapters to determine the performance of the proposed new codes. Chapter 5 introduces the new generalised Chase (GC) algorithms, followed by the adaptive immediate decision (AID) and test pattern elimination (TPE) algorithms. These can be used to offer near maximum likelihood (ML) performance with minimum increase in complexity. Chapter 6 is concerned with combined EC and line codes to form ECLCs. These can offer both tight line coding characteristics and good decoding performance. Some emphasis is placed on implementation appropriate to very high bit rate systems. Finally chapter 7 brings the thesis to a conclusion and provides recommendations for future work.

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