25 Gbps mobile visible light communication system employing fast adaptation techniques

Abstract

Visible light communication (VLC) systems have typically operated at data rates below 20 Gbps and operation at this data rate was shown to be feasible by using laser diodes (LDs), beam steering, imaging receivers and delay adaptation techniques. However, an increase in the computational cost is incurred. In this paper, we introduce fast computer generated holograms (FCGHs) to speed up the adaptation process. The new, fast and efficient fully adaptive VLC system can improve the receiver signal to noise ratio (SNR) and reduce the required time to estimate the position of the VLC receiver. In addition, an imaging receiver and a delay adaptation technique are used to reduce the effect of inter symbol interference (ISI) and multipath dispersion. Significant enhancements in the SNR, with VLC channel bandwidths of more than 36 GHz are obtained resulting in a compact impulse response and a VLC system that is able to achieve higher data rates (25 Gbps) with full mobility in the considered indoor environment. Keywords:Beam steering, imaging receiver, fast computer generated hologram, delay adaptation technique, SNR. INTRODUCTIONTraditional radio and microwave communication systems suffer from limited channel capacity due to the limited radio spectrum available, while the data rates requested by the users continue to increase exponentially. Achieving very high data rates (multi gigabits per second) using the relatively narrow bandwidth of microwave and millimetre wave systems is challenging [1]. According to a GreenTouch research study, mobile Internet traffic over this decade (2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020)) is expected to increase by 150 times [2]. Given this expectation of dramatically growing demand for data rates, the quest is already underway for alternative spectrum bands beyond microwaves and millimetre waves. Different technology candidates have entered the race to provide ultra-fast wireless communication systems for users. Visible light communication (VLC) systems are among the promising solutions to the bandwidth limitation problem faced by microwave systems [1]. They are also considered among the potential candidates for 5G indoor systems [3]. Previous work has shown that significant enhancements in the VLC system data rates can be achieved by replacing LEDs with LDs coupled with the use of an imaging receiver instead of the conventional wide field of view (FOV) receiver [4], [5], [6]. A data rate of 10 Gbps in a realistic environment has been shown to be possible with a VLC system when a delay adaptation technique in conjunction with laser diodes and imaging receiver were used with a simple modulation format (on-off keying, OOK) and without the use of relatively complex wavelength division multiplexing approaches [4]. Significant improvements were shown to be possible when a VLC relay assisted system is combined with an imaging receiver and a delay adaptation technique [7]. However, given typical parameters, the latter system cannot provide a throughput beyond 10 Gbp...

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