UBC Theses and Dissertations
Binary-coded modulation and applications in free-space optics Nguyen, Trung Thanh
Binary-coded modulation techniques such as bit-interleaved coded modulation (BICM) and multilevel coding (MLC) are pragmatic methods to achieve both high power and bandwidth efficiencies in digital communications. These techniques enable the combination of powerful and popular off-the-shelf binary codes with bandwidth-efficient multilevel signaling without considerable performance loss compared to joint coding and modulation designs. Today, binary-coded modulation has become almost universal in digital communication systems. This thesis concerns several aspects of binary-coded modulation and its applications. For BICM, we study the use of approximate decoding metrics to reduce detection complexity. Specifically, we propose metric correction functions which can improve achievable rates. We further propose a metric scaling which can improve throughput performance of symbol-by-symbol (SBS) decoding, which is the basis of state-of-the-art error-control coding systems. To this end, we also discover an intriguing relationship between the generalized Gallager function and the performance of sum-product SBS decoding. For MLC, we develop the concept of reduced-layer coding that facilitates a trade-off between performance and structural complexity. We then propose a novel rateless MLC scheme which can seamlessly adapt to the instantaneous channel quality and achieve throughput gains compared to BICM in a number of transmission scenarios. Finally, we apply binary-coded modulation techniques to free-space optics (FSO). FSO is an interesting transmission technology which has recently emerged as a low-cost solution to a range of communication challenges. We consider advanced signaling schemes such as channel coding diversity with mismatched decoding metrics and multipulse pulse-position modulation (MPPM). Combined with binary codes, these schemes are practical means to improve rate and reliability in FSO systems.
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