Abstract
In this paper, we propose two digital signal processing (DSP) techniques, the orthogonal circulant matrix transform (OCT) technique and the singular value decomposition (SVD)-based adaptive loading, to reduce the bit error rate (BER) of multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM)-based visible light communication (VLC) systems, without and with using the channel state information (CSI), respectively. A gigabit/s 2 × 2 MIMO-OFDM VLC system under ~100-MHz system bandwidth, with both symmetrical and asymmetrical MIMO setups, is demonstrated. It is shown that both techniques can attain outstanding BER reduction regardless of the transceivers' geometrical distributions. The SVD-based adaptive loading exhibits the best performance but requires the CSI. The OCT technique can achieve suboptimal performance without the needs of CSI. In both the 1.6-Gbit/s symmetrical MIMO setup and the 1.2-Gbit/s asymmetrical setup, we achieved more than one and two orders of magnitude reductions in the BER by using the OCT technique and the SVD-based adaptive loading, respectively.
Highlights
With the substantial increase in the number of multimedia-capable and Internet-connected mobile devices, e.g., smartphones and tablets, the explosion of wireless data traffic has been witnessed in recent years [1]
Different from the single-input and single-output (SISO) case, in this work we propose the orthogonal circulant matrix transform (OCT) technique for Multiple-input multiple-output (MIMO) visible light communication (VLC) to address the performance disparity between different subcarriers within each transceiver and different transceivers, wherein the latter depends on the geometrical distributions of transceivers
The SNR profiles of the two Rxs are nearly identical by using the joint OCT technique
Summary
With the substantial increase in the number of multimedia-capable and Internet-connected mobile devices, e.g., smartphones and tablets, the explosion of wireless data traffic has been witnessed in recent years [1]. Visible light communication (VLC) is rapidly emerging as an attractive solution for future high-speed wireless access. The dual functionality offered by VLC, i.e., the primary illumination function and the high-rate communication function, has enabled a wide range of applications for both indoor and outdoor scenarios [2]. 10-Gbit/s data rates were demonstrated in VLC, expensive and/or specially designed devices, e.g. injection-locked and impedance-matched lasers were required to enhance the system bandwidth beyond 1 GHz [3–5]. The main challenge for VLC, using the off-the-shelf components, to provide high-speed data communication is the severe frequency roll-off, induced by the limited system bandwidth [6]. Prior works including digital signal processing (DSP) [6–9] and analog circuit based equalization [10] have been reported, most of which lay emphasis on single-input and single-output (SISO) VLC systems
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