Abstract
In optical camera communication (OCC) systems leverage on the use of commercial off-the-shelf image sensors to perceive the spatial and temporal variation of light intensity to enable data transmission. However, the transmission data rate is mainly limited by the exposure time and the frame rate of the camera. In addition, the camera's sampling will introduce intersymbol interference (ISI), which will degrade the system performance. In this paper, an artificial neural network (ANN)-based equaliser with the adaptive algorithm is employed for the first time in the field of OCC to mitigate ISI and therefore increase the data rate. Unlike other communication systems, training of the ANN network in OCC is done only once in a lifetime for a range of different exposure time and the network can be stored with a look-up table. The proposed system is theoretically investigated and experimentally evaluated. The results record the highest bit rate for OCC using a single LED source and the Manchester line code (MLC) non-return to zero (NRZ) encoded signal. It also demonstrates 2 to 9 times improved bandwidth depending on the exposure times where the system's bit error rate is below the forward error correction limit.
Highlights
There are two type of optical receivers commonly used in visible light communication (VLC) systems: (i) photodiodes (PDs); and (ii) image sensors (ISs) [1]–[3]
In this paper, for the first time, we propose and implement an artificial neural network (ANN)-based equaliser to mitigate the intersymbol interference (ISI) induced by high sampling duration within the observed frame in optical camera communications (OCC), and increase the transmission data rate
We have developed an experimental test-bed for the proposed system for evaluating its performance in terms of the data rate, bit error rates (BER) and eye diagrams
Summary
There are two type of optical receivers commonly used in visible light communication (VLC) systems: (i) photodiodes (PDs); and (ii) image sensors (ISs) [1]–[3]. In [26], an ANN-based equaliser was deployed in a fully connected mode to reduce the effect of the inter-symbol interference in a non-LOS (NLOS) or diffuse VLC link in indoor environment It is deployed in OCC systems to compensate for the data loss by reducing the gap-time between observed frames [28]. We have achieved the highest data rate in OCC using a single white LED source, the MLC NRZ encoded signal at the transmitter, an image sensor with Rf of 30 fps and an ANN-based equaliser at the receiver.The achievable bandwidth is increased by approximately 9, 5, and 2 times for Texp of 2, 1 and 0.5 ms, respectively compared with the existing reported systems [6].
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