On the Improvement of the Soft-Output Sphere

• Main Authors: Feng, Shih-Lun, 馮世綸
• Other Authors: 陳伯寧
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/62743936338931022057

碩士 === 國立交通大學 === 電信工程研究所 === 99 === Many solutions for detecting signals transmitted over flat-faded multiple input multiple output (MIMO) channels have been proposed, e.g., the zero-forcing (ZF) detector, minimum mean squared error (MMSE) detector, brutal-force maximum likelihood (ML) detector, sphere decoding (SD) algorithm, to name a few. These approaches however either do not provide soft-output or suffer from high complexity when being modified to a soft-output counterpart. In this thesis, we focus on the soft-output SD algorithm and the methods of its computational complexity reduction. We will first illustrate that the single tree search (STS), ordered QR decomposition, channel matrix regularization, and log-likelihood ratio clipping can reduce the decoding complexity but at a price of the performance degradation. We then present a new algorithm for soft detection in an MIMO system. Simulations show that our new method can achieve simultaneously less performance degradation and less decoding complexity than the existing methods.