Design of rate-compatible punctured repeat-accumulate codes

Date

2010-03-18T16:43:28Z

Authors

Planjery, Shiva Kumar

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Abstract

In present day wireless applications, especially for time-varying channels, we require flexible coding schemes that utilize a minimum of bandwidth and can support different code rates. In addition, we require coding schemes that are simple in terms of complexity but give good performance. Recently a special class of turbo-like codes called repeat accumulate (RA) codes were proposed. These codes are extremely simple in terms of complexity compared to turbo or LDPC codes and have been shown to have decoding thresholds close to the capacity of the AWGN channel. In this thesis, we propose rate-compatible punctured systematic RA codes for the additive white Gaussian noise (AWGN) channel. We first pro-pose a three phase puncturing scheme that provides rate compatibility and show that very high rate code rates can be obtained from a single mother code. We then provide a methodology to design rate-compatible RA codes based on our three phase puncturing scheme. The design involves optimizing the punctured profile of the code such that the resulting high rate codes give good performance. The design is done with the help of existrinsic in-formation transfer (EXIT) charts which are plots used to analyze the constituent decoders. Code rates up to 10/11 are obtained from a single rate 1/3 regular RA code. Performance results show that our design methodology combined with our proposed puncturing scheme can provide significant coding gains at high code rates even with practical blocklengths. Hence rate-compatible punctured RA codes are suitable for many wireless applications.

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Keywords

wireless communication systems, random noise theory

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