Visible light communications (VLC) is a new emerging technology, which provides both data transmission and illumination by utilizing the visible range (370-780 nm) of the electromagnetic spectrum. In order to maximize the available data rate and enhance the users mobility within an indoor environment, it is essential to characterize the communication channel. In this paper, we present both analytical and experimental results for a VLC system affected by movement of people for different indoor conditions (i.e., furnished office room, empty hall, and corridor). VLC systems utilize multiple light-emitting diodes mounted in the ceiling and the configuration is based on the nondirected line of sight. We consider random movement of people within the room, focusing on the impacts of shadowing and blocking on mobility and link system performance by investigating changes in the channel characteristics using the cumulative distribution function of the received power distribution and the delay profile. We demonstrate the behaviour of communication channels for different scenarios from corridor, the most robust against people movement induced fading, to the office rooms and halls, the most vulnerable to the received power fluctuation.

In this paper, we experimentally demonstrate a multiband carrierless amplitude and phase modulation format for the first time in VLC. We split a conventional carrierless amplitude and phase modulated signal into m subcarriers in order to protect from the attenuation experienced at high frequencies in low-pass VLC systems. We investigate the relationship between throughput/spectral efficiency and m, where m = {10, 8, 6, 4, 2, 1} subcarriers over a fixed total signal bandwidth of 6.5 MHz. We show that transmission speeds (spectral efficiencies) of 31.53 (4.85), 30.88 (4.75), 25.40 (3.90), 23.65 (3.60), 15.78 (2.40), and 9.04 (1.40) Mb/s (b/s/Hz) can be achieved for the listed values of m, respectively.

Visible light communications is a technology with enormous potential for a wide range of applications within next generation transmission and broadcasting technologies. VLC offers simultaneous illumination and data communications by intensity modulating the optical power emitted by LEDs operating in the visible range of the electromagnetic spectrum (~370-780 nm). The major challenge in VLC systems to date has been in improving transmission speeds, considering the low bandwidths available with commercial LED devices. Thus, to improve the spectral usage, the research community has increasingly turned to advanced modulation formats such as orthogonal frequency-division multiplexing. In this article we introduce a new modulation scheme into the VLC domain; multiband carrier-less amplitude and phase modulation (m-CAP) and describe in detail its performance within the context of bandlimited systems.

In general, visible light communication (VLC) systems, which utilise white light-emitting diodes (LEDs), only offer a bandwidth limited to the low MHz region. Therefore, providing VLC-based high data rate communications systems becomes a challenging task. To address this challenge, we propose a solution based on multiplexing in both the frequency and space domains. We experimentally demonstrate a 4 $\times$ 4 imaging multiple-input multiple-output (MIMO) VLC system (i.e., space multiplexing) utilising multi-band carrier-less amplitude and phase (m-CAP) modulation (i.e., frequency multiplexing). Independently, both MIMO and m-CAP have shown the remarkable ability to improve transmission speeds in VLC systems, and hence, here we combine them to further improve the net data rate. We investigate link performance by varying the number of subcarriers m, link distance L, and signal bandwidth B$_{sig}$. From all the values tested, we show a data rate of ~249 Mb/s can be maximally achieved for m = 20, B$_{sig}$ = 20 MHz, and L = 1 m, at a bit error rate of 3.2$\times$10$_{-3}$ using LEDs with ~4 MHz bandwidth.