Mobility

EM-Based Maximum-Likelihood Sequence Detection for MIMO Optical Wireless Systems

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Executive Summary

A major performance-limiting factor in terrestrial Optical Wireless (OW) systems is turbulence-induced fading. Exploiting the additional degrees of freedom in the spatial dimension, multiple laser transmitters combined with multiple receiver apertures provide an effective solution for fading mitigation. Although MIMO (Multiple-Input Multiple-Output) OW systems have been extensively studied in recent years, most of these works are mainly limited to symbol-by-symbol decoding. Maximum Likelihood Sequence Detection (MLSD) exploits the temporal correlation of turbulence-induced fading and promises further performance gains. In this paper, the authors investigate MLSD for IM/DD (Intensity-Modulation/Direct-Detection) MIMO OW systems over log-normal atmospheric turbulence channels. Even with a low-order modulation scheme such as On-Off keying which is typically used in OW systems, the complexity of MLSD might be prohibitive.

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