The authors address various important issues related to punctured turbo codes. A modified technique for finding the transfer function of punctured turbo codes is developed. This modified technique provides a means of deterministic evaluation of the weight distribution of the code, as well as a possibility of studying vanous puncturing patterns. These advantages are shown with some illustrative examples. Moreover, the paper explains some characteristics of the puncturing pattern, and arrives at useful guidelines for the design of a good puncturing matrix.
The severity of fading on mobile communication channels calls for the combining of multiple diversity sources to achieve acceptable error rate performance. Traditional approaches perform the combining of the different diversity sources using either: the Conventional Selective diversity combining (CSC), Equal-Gain combining (EGC),
Powerful rate-compatible codes are essential for achieving high throughput in hybrid automatic repeat request (ARQ) systems for networks utilising packet data transmission. The paper focuses on the construction of efficient rate-compatible low-density parity-check (RC-LDPC) codes over a wide range of rates. Two LDPC code families are considered; namely, regular LDPC codes which are known for good performance and low error floor, and semi-random LDPC codes which offer performance similar to regular LDPC codes with the additional property of linear-time encoding. An algorithm for the design of punctured regular RC-LDPC codes that have low error floor is presented. Furthermore, systematic algorithms for the construction of semi-random RC-LDPC codes are proposed based on puncturing and extending. The performance of a type-II hybrid ARQ system employing the proposed RC-LDPC codes is investigated. Compared with existing hybrid ARQ systems based on regular LDPC codes, the proposed ARQ system based on semi-random LDPC codes offers the advantages of linear-time encoding and higher throughput. Recently, in [8], a systematic method was proposed for finding good puncturing distributions for finite-length LDPC codes, in which the codeword length is small, which
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