Block codes are one of the most widely used codes to improve reliability of data transmissions. They are used both independently as well as with other codes such as convolutional codes and have found many applications in many areas, ranging from space communications to digital versatile discs (DVD). More recently, powerful codes derived from block and iteratively decoded codes have also been adopted in serveral standards (e.g. DVB-S2). The first part of this thesis deals with the design of computationally efficient soft-decision decoding algorithms for block codes. / A bandwidth-efficient modulation technique called orthogonal frequency division multiplexing (OFDM) has been adopted in many international standards to achieve high speed data transmissions over frequency selective fading channels. OFDM signals however, have high amplitude fluctuations. This is known as the peak-to-average power ratio (PAPR) problem. The second part of this thesis focuses on designing a coding scheme to simultaneously correct errors and reduce the PAPR of OFDM signals. / Soft-decision decoding of block codes provide significant performance gains over hard-decision decoding. However, optimal soft-decision decoding is an NP-hard problem, where the decoding complexity grows exponentially with the code length. This thesis develops two computationally efficient sub-optimal soft-decision decoding algorithms by formulating soft-decision decoding as an optimisation problem. The two algorithms are based on a compact genetic algorithm and a k shortest paths algorithm, respectively. The performance and complexity of these algorithms are investigated and compared with various other known decoding schemes. The results obtained show that the proposed decoding algorithm achieves large performance gains over the known decoding schemes. It is also observed that the proposed algorithms achieve near-optimal performance with manageable complexity. / In addition to these soft-decision decoding algorithms, this thesis also proposes a coding technique and an efficient encoding algorithm for joint error-correction and PAPR reduction of OFDM signals. The proposed coding technique is first expressed as an optimisation problem and a computationally efficient sub-optimal algorithm is then proposed to solve this problem. The PAPR reduction and error-correction performance of the proposed algorithm are studied. The results show that the proposed algorithm significantly improves the system performance and also gives PAPR reductions comparable with other known PAPR reduction techniques. / Thesis (PhDTelecommunications)--University of South Australia, 2007.
| Identifer | oai:union.ndltd.org:ADTP/267087 |
| Creators | Shakeel, Ismail. |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | copyright under review |
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