Adaptive threshold device for detection of reflections based visible light communication

• Published in: Optics communications Vol. 388; pp. 1 - 11
• Main Authors: Amini, Changeez, Taherpour, Abbas
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2017
• Subjects: Bayes risk; Inter symbol interference (ISI); Optical channel model; Receiver design; Spectral efficiency; Visible light communications; Bayes risk; Spectral efficiency; Optical channel model; Visible light communications; Inter symbol interference (ISI); Receiver design
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2016.10.057

One of the major restriction of existing visible light communication (VLC) systems is the limitation of channel transmission bandwidth which can be used in such systems. In this paper, an optimal and a suboptimal receiver are proposed to increase the on-off keying (OOK) transmission rate and hence to increase bandwidth efficiency of VLC system when a multiple reflections channel model is used to characterize the impacts of reflections in VLC signal propagation. Optimal detector consists of a simple receiver with a memory to find the optimal threshold based on the previous detected data. The error probability of the proposed detector is derived in the closed form and compared with the simulation results. It is demonstrated that the proposed detectors can improve the transmitting bandwidth close to the 3-dB bandwidth of the LOS channel model (which is several hundred MHz), whereas bit-error-rate (BER) remains low, in particular where the optimal detection is utilized. •We propose two methods to find the optimal threshold to increase the transmitting bandwidth closer to the 3-dB bandwidths of LOS scheme. Unlike the foregoing works in the field of ISI problem in reflection based VLC, the considered system model is Masao-Nakagawa or even a multiple reflections model.•We determine the optimal threshold for two cases of either the memory is available or not at the receiver resulting to optimal and suboptimal receiver design, respectively.•For optimal receiver according to the number of interfering bits, the corresponding BERs are computed in closed-form and also optimal threshold are derived in order the receiver to acquire the minimum attainable Bayes risks.•For the suboptimal receiver which suffers from N symbols of ISI and does not benefit from memory, we derive the BERs in closed-form and corresponding optimized decision threshold for OOK modulator. Likewise, we derive the upper bound for the general case on condition that ISI to orginate from one bit only.•In order to give the general solution to the hypothesis-testing problem for practical scenarios, the effect of ISI measurement error is investigated.