Design of multiuser Visible Light Communication for localization applications

Visible light communication (VLC) system has received significant attention and it has been penetrating numerous zones of daily life on account of its promising feature of data transmissions, in parallel to illumination. VLC is also a potential candidate for green data communication as its transmission is free from all hazards present in other wireless technologies such as Wi-Fi etc. This technology carries number of unique features such as license free spectrum (384 THz-789 THz), high transmission speed, dual use (illumination and data communication), ubiquitousness, low cost components, stable channel conditions. However, there are certain challenges in the design of this novel technology such as efficient channel access scheme, its use for accurate localization, duplex transmission system, dimming control and suitable form of modulated signal that could drive the optical transmitter (LEDs) circuit. In this proposal, two of above mentioned challenges are investigated, i.e., suitable channel access scheme to boost system capacity and its use for localization application. Both orthogonal and non-orthogonal multiple access schemes are investigated based on selected performance metrics. Non-Orthogonal Multiple Access (NOMA) permits simultaneous data transmission with each user operating in the same band and at the same time where they are distinguished by their power levels or specific codes. Thus, infusion of NOMA to VLC system effectively enhances the spectral efficiency (SE) which is the key to its use for localization accuracy. It is worth-noting that in the conventional NOMA scheme, the possible pair of users is limited and this limitation restricts the capacity improvement. Therefore, in order to improve the total capacity for the downlink NOMA, a joint detection (JD) with phase pre distortion (PPD) decoding scheme needs to be investigated which can decode multiple signals jointly and it achieves superior Bit Error Rate (BER) performance, compared to popular decode scheme used in NOMA, i.e., Successive Interference Cancellation (SIC). The proposed VLC-NOMA will be investigated for localization application based on novel Time Difference of Arrival (TDoA) algorithm.