Yesilkaya, A.Basar, E.Miramirkhani, FarshadPanayirci, E.Uysal, Murat2017-10-052017-10-052017-080090-6778http://hdl.handle.net/10679/5638https://doi.org/10.1109/TCOMM.2017.2699964Due to copyright restrictions, the access to the full text of this article is only available via subscription.Visible light communications (VLC) is a promising and uncharted new technology for the next generation of wireless communication systems. This paper proposes a novel generalized light emitting diode (LED) index modulation method for multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM)-based VLC systems. The proposed scheme avoids the typical spectrum efficiency losses incurred by time- and frequency-domain shaping in OFDM signals. This is achieved by exploiting spatial multiplexing along with LED index modulation. Accordingly, real and imaginary components of the complex time-domain OFDM signals are separated first, then resulting bipolar signals are transmitted over a VLC channel by encoding sign information in LED indexes. As a benchmark, we demonstrate the performance analysis of our proposed system for both analytical and physical channel models. Furthermore, two novel receiver designs are proposed. Each one is suitable for frequency-flat or selective channel scenarios. It has been shown via extensive computer simulations that the proposed scheme achieves considerably better bit error ratio versus signal-to-noise-ratio performance than the existing VLC-MIMO-OFDM systems that use the same number of transmit and receive units [LEDs and photo diodes (PDs)]. Compared with the single-input single-output (SISO) DC biased optical (DCO)-OFDM system, both spectral efficiency and DC bias can be doubled and removed respectively simply by exploiting a MIMO configuration.enginfo:eu-repo/semantics/restrictedAccessArticle6583429344100041100610001810.1109/TCOMM.2017.2699964Visible light communications (VLC)Multiple-input-multiple-output (MIMO) systemsOrthogonal frequency division multiplexing (OFDM)Optical-spatial modulation (OSM)LED index modulationMaximum-a-posteriori probability (MAP) estimator2-s2.0-85029509430