A Multigigabit per Second Integrated Multiple-Input Multiple-Output VLC Demonstrator

Abstract

In this paper, we report the performance of an imaging multiple input multiple output (MIMO) visible light communication (VLC) system. The VLC transmitter consists of a two-dimensional, individually addressable Gallium Nitride micro light emitting diode (µLED) array. The receiver uses a two-dimensional avalanche photodiode (APD) array fabricated using complementary metal oxide semiconductor (CMOS). Using integrated CMOS-based LED drivers, a data rate greater than 1 Gbps was obtained at a link distance of 1 m with the system field of view (FOV) of 3.45 degree using four channels. At a reduced link distance of 0.5 m, a data rate of 7.48 Gbps was obtained using a nine channel MIMO system. This demonstrates the feasibility of compact MIMO systems which offer substantial data rates. Index Terms-Visible light communications, multiple input multiple output, VLC demonstrator, integrated VLC I. INTRODUCTION Visible light communications (VLC) systems, realized using solid-state lighting (SSL) devices, can offer high-speed data communication in addition to their primary purpose of illumination. With the white light emitting diodes (LEDs) expected to be the dominant illumination device in the home and office environment in the near future, the use of VLC systems will grow exponentially over the coming decades [1]. As a result, there has been significant research and commercial interest in VLC systems over the last ten years (see [2] for the detailed review). This is largely due to several key advantages that VLC offers in comparison to the existing radio frequency (RF) technology, including license-free operation, high available bandwidth, high spatial diversity, innate security, and controlled beam shaping. Phosphor based white LEDs have a low communication bandwidth (a few MHz) due to the long photoluminescence lifetimes of the phosphor [3]. The bandwidth of the blue LED itself is limited to 20-30 MHz. Using pre and post-equalisation for on-off keying (OOK) modulation, a data rate of 550 Mbps M anuscript

Transmitter and receiver technologies for optical wireless

“…Examples of array receivers can be found in [18,99]. For both the transmitter and the receiver, the challenge is the implementation complexity, as individual drive circuitry is required for each source, and receiver circuitry for each detector in the respective arrays.…”

“…The path loss for each of the potential transmitter/receiver pairs can either be estimated or calculated, leading to an equation relating the transmitted signal vector T to the received signal vector R. If the channel matrix H is known, either by calculation or measurement, multiplying the received signal vector R by its inverse yields an estimate of the data sent T. Figure 9 shows an integrated MIMO demonstrator, fabricated as part of a UK EPSRC funded project including the Universities of Oxford, Cambridge, Strathclyde, Edinburgh and St Andrews. This has nine transmission channels and operates at approximately 7 Gb s −1 [18].…”

Reproducing Single-Carrier Digital Modulation Schemes for VLC by Controlling the First Switching Harmonic of the DC–DC Power Converter Output Voltage Ripple

“…However, since all the communication channels are using the same frequency band, the difficulty is differentiating the data streams of each channel at the receiver. The MIMO technique exploits this idea considering n transmitters and n receivers [32]- [35]. The key point is that each transmitter has a different orientation, thus transmitting most of the optical power to only one of the receivers.…”

Spatial and wavelength division multiplexing for high-speed VLC systems: An overview

“…The transmitter and receiver optics were designed in such a way that there was a minimum cross-talk in the perfectly aligned condition. By using joint spatial and temporal equalization for the 4-PAM scheme, a minimum data rate of 1.3 Gb/s was achieved using four channels within the FOV of 3.5 degrees [40]. Further improvement up to 7 Gb/s was achieved using nine channels at the reduced FOV.…”