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Unformatted text preview: he literature as symbol-by-symbol MAP. It is not the same topic that was considered in Section 2.2 – here we assume symbol memory in our observation. It is not the same topic that was covered in Section 2.3 – here we are interested in symbol (not sequence) estimation. We introduce two basic symbol-by-symbol MAP approaches: forward-only or on-line, which is covered in the Course Text in Subsection 5.1.5; and forward/backward or block, which is just mentioned in Subsection 5.1.5. Compared to MLSE, there is little or no performance advantage with symbol-by-symbol MAP, and symbol-by-symbol MAP is conceptually more challenging and computationally more burdening. However, with the advent over the last decade of cascaded coding and iterative (e.g. turbo) decoding and equalization, both the forward-only and forward/backward approaches have become very popular. This is because symbol-by-symbol MAP algorithms directly provide soft outputs which are central to the performance advantage of turbo methods, as opposed to MLSE which...
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This document was uploaded on 10/12/2009.
- Spring '09