A comparative analysis of the potential of robust coding schemes in emerging wireless technologies
Kaluuba, Livingstone Listone
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This study investigates the critical design parameters for robust codes used for data transmission systems in a wireless environment. Robustness refers to the ability of a given code to withstand transmission channel impairments, and thus deliver a useable signal despite the unavoidable signal corruption of the channel. One of the major obstacles to the accurate delivery of information from the source to some destination is the unpredictable and random behaviour of the wireless communication channel. There are several factors/processes which influence the performance of the communication channel, namely: noise, distortion, shadowing, multipath fading, and many others. Most of these are stochastic in nature and we have often to deal with probabilistic variables. The main culprit of the channel impairments in a mobile environment, however, is multipath fading. Several methods exist for combating the multipath problem, such as space diversity, frequency diversity, polarization diversity, and adaptive modulation, but we believe that forward error coding is the most versatile method for mobile communications. This thesis deals with the fundamental issues related to the recovery of a useful signal from the corrupted signal using the forward error correction coding technique in a wireless environment. This is only possible through the use of robust codes whose mathematical origin is rather interesting, extending from the binary number system, to information theory and finally coding theory. The thesis discusses the background to the wireless transmission problem, how it manifests itself in terms of path loss, shadowing, multipath attenuation, wave absorption, etc., mathematical modeling of these processes, multipath fading mitigation methods, and finally gives a comparative presentation of the critical design parameters of turbo codes as a representative example of robust codes. From the error performance analysis and results, it is evident that turbo codes are quite suitable for the emerging wireless communications technologies and applications. However, low density parity check codes are preferred to turbo codes in some applications because of their more efficient implementation as well as better performance.