A Study On Demodulation Based On Iterative Processing

This dissertation is devoted to a study on demodulation technologies based on iterative processing in Software Radio. The work finished in this paper is a part of the overall task targeting at the projects undertaken by our scientific discipline.In recent years, Iterative Processing, due to its huge latency in performance improvements, is attracting more and more attentions and has become a hot topic of research in many fields of communication signal processing such as detection and equalization etc..First, based on the analysis of encoding and decoding theory in Turbo codes, the decoding algorithms of sub-decoders in iterative process are investigated while laying emphasis on Soft-Out Viterbi Algorithm (SOVA). Based on which, targeting at breaking through the limitation of the algorithm, computational complexity is simplified, and an improved algorithm is proposed which can be used in iterative demodulation of signals encoded with non-systematic codes.And then, carrier synchronization technology is discussed in detail. The central problem in this section is about how to utilize soft-out likelihood for non-data-aided carrier synchronization. Various frequency offset estimation algorithms are discussed, and an estimation algorithm based on iterative processing is emphasized on condition that frequency offset is small with regard to symbol rate. After common methods of phase estimation are introduced, an algorithm named as Li algorithm is analysed. Anew phase estimation algorithm based on joint iterative processing of carrier phase estimation, demapping and decoding is proposed for routine communication signals.Finally simulation results are provided which have proved the feasibility and effectiveness of the algorithms proposed in this paper. The algorithms proposed in this paper could be used for practical implementation of signal demodulation and provided a necessary basis of design and experiments on software-radio-based comprehensive platform.