The efficient denoising artificial light interference using discrete wavelet transform with application to indoor optical wireless system

—Reducing the effect of the artificial light interference (ALI) in indoor optical wireless (OW) communication is a challenging prospect because of the spectral overlaps between the interference and the baseband modulating signal. High pass filtering is used for mitigating the effect of ALI; however it introduces another form of interference known as baseline wander (BLW). In this paper, an alternative approach is investigation to minimize the performance degradation due to ALI using the discrete wavelet transform (DWT). Performances of different digital baseband modulation techniques are examined under the influence of the ALI in line-of-sight (LOS) links and we show that the DWT is very effective in reducing the effect of the ALI. 1. Introduction We have seen an exponential growth in bandwidth requirement per end-user due to profuse growth in the internet user and the file sharing, and video broadcasting. Though RF technologies already available can provide the required bandwidth up to a certain point beyond which bandwidth congestion becomes a bottleneck. One of the proposed solutions is to move to a higher frequency band of 10 GHZ and 60 GHz, which is still in research and development stages. However, there is a solution to the last-mile problem that is based on the optical communication systems. Though the fibre-to-the-home is already a proven concept, the cost and environmental effect may count against it for new installations. The alternative solutions would be to use OW links, which is more suitable for indoor as well as outdoor applications. Outdoor OW link is more mature than the indoor offering data rates of 10 Gbps per wavelength over a range of up to 6 km [1, 2]. The LOS indoor OW systems can provide data rates in access of the 1 Gbps without any multiple access [3], but high blocking probability and lack of mobility make them suitable for limited applications. The diffuse links on the other hand provide mobility to certain extent at the cost of a high path loss and reduce data rates. However, the key challenge to the reliability of the link for both LOS and non-LOS links arises from the ambient light radiations from natural and artificial sources. The background radiation can be received as an average power much larger than the desired signal, even when optical filtering is employed. The background radiation can be model as the signal independent additive white Gaussian noise (AWGN). However, ALIs are periodic and …