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In this paper we propose a hybrid visible light communications (VLC) and radio frequency (RF) femtocell system and investigate user association issues to achieve effective load balancing. We propose a scheme for cell association based on the minimum distance to the closest access point (AP) which involves a simple and fully uncoordinated decision. The performance of the three tier (macro-, femto-...
In this paper the average area spectral efficiency (ASE) of indoor visible light communication (VLC) wireless network is investigated for various room geometries (2.5m×5m×3m, 5m×5m×3m and 10m×10m×3m). A comparison is made against state-of-the-art radio frequency (RF) systems employing femtocells indoors. A modified version of the wireless world initiative new radio (WINNER) indoor deployment scenario...
In this paper the optimum placement of light emitting diode (LED) arrays is investigated for indoor visible light communication (VLC) subject to maximization of average area spectral efficiency (ASE). Design parameters of LED array such as the distance between two neighboring LEDs and the precise location on the ceiling of the LED arrays can be obtained by solving an optimization problem. The formulated...
In this paper, the performance of an asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) indoor wireless system is investigated. In particular, the illuminance distribution inside a room (5m×5 m×3m) under different brightness conditions, i.e. dimming levels, and the electrical signal-to-noise ratio (SNR) at the receiver are considered. The system performance is also...
This paper analyses the impact of imperfect synchronisation in optical orthogonal frequency division multiplexing (OFDM) systems utilising intensity modulation (IM) / direct detection (DD). The use of IM/DD technique inherently eliminates the problem of carrier frequency offset. Therefore, time-frequency synchronisation in optical OFDM system reduces to frame synchronisation and sampling clock synchronisation...
Nonlinearities can drastically degrade the performance of OFDM (orthogonal frequency division multiplexing) based optical wireless (OW) communication systems using intensity modulation (IM) of the optical carrier. The light emitting diode (LED) transfer function distorts the signal amplitude and forces the lower signal peaks to be clipped at the LED turn-on voltage (TOV). Additionally, the upper signal...
Optical spatial modulation (OSM) is a pulsed modulation technique for indoor optical wireless (OW) communication systems, proposed recently in [1]. In this paper, the performance of OSM is significantly enhanced by proper geometrical alignment of transmit and receive units. In OSM, multiple transmit units are considered where only a single transmit unit is activated at a particular time instance and...
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