Soft-output sphere decoding: Algorithms and VLSI implementation


Christoph Studer, Andreas Burg, and Helmut Bölcskei


IEEE Journal on Selected Areas in Communications, Vol. 26, No. 2, pp. 290-300, Feb. 2008.

DOI: 10.1109/JSAC.2008.080206

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Multiple-input multiple-output (MIMO) detection algorithms providing soft information for a subsequent channel decoder pose significant implementation challenges due to their high computational complexity. In this paper, we show how sphere decoding can be used as an efficient tool to implement soft-output MIMO detection with flexible trade-offs between computational complexity and (error rate) performance. In particular, we provide VLSI implementation results which demonstrate that single tree-search, sorted QR-decomposition, channel matrix regularization, log-likelihood ratio clipping, and imposing run-time constraints are the key ingredients for realizing soft-output MIMO detectors with near max-log performance at a chip area that is only 50 percent higher than that of the best-known hard-output sphere decoder VLSI implementation.


MIMO, VLSI, soft-output sphere decoding, single tree search, LLR clipping, run-time constraints, sorted QR-decomposition

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