UBC Theses and Dissertations

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UBC Theses and Dissertations

Signal mapping for bit-interleaved coded modulation with iterative decoding Mohammadnavazi, Hassan


Due to its convenience, wireless communication systems have grown tremendously. Data rate requirements of various services/applications that are transmitted over wireless channels are increasing day by day. Bit interleaved coded modulation (BICM), which is a serial concatenation of a channel encoder, an interleaver and a symbol mapper, is a spectral efficient technique that is being used in many wireless systems. The performance of BICM can be significantly improved by using the iterative decoding technique at the receiver. This system is referred as BICM with iterative decoding (BICM-ID), and offers an improved performance over both fading and nonfading channels. It is well-known that BICM-ID performance is strongly dependent on the applied signal mapping. Signal mapping is the assignment of binary bits to complex symbols from a modulation alphabet. It is demanded to use a higher order modulation in BICM-ID to achieve a higher data rate and spectral efficiency. However, finding a mapping for a large modulation that offers an improved performance for BICM-ID is very complicated. This is because of the huge number of possible mappings for higher order modulations. This thesis focuses on the mapping problem for BICM-ID systems. In particular, novel mapping methods are developed for higher order modulations, including two-dimensional and multi-dimensional modulations. The proposed methods in this thesis consist of (i) heuristic methods and (ii) computer search techniques. In comparison with the previously known mappings, the proposed mappings significantly improve the BICM-ID performance over the considered channels. This is confirmed by various analytical and simulation results that are investigated in this thesis.

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