Applying the FRFT to an OFDM System for Li-Fi : A Design Experiment for Peace Engineering Education

Abstract

Peace engineering is a new window in science, technology, math and engineering (STEM) programs that educates STEM students and engineers to consider how their engineering products, solutions and designs impacts the society and economy. This paper presents a design experiment that can be used for both peace education and engineering. Visible Light Communication (VLC) and Li-Fi can provide cheaper access to Internet and communications. On the other hand, it is environment friendly and is considered as green communications.This paper presents a novel multi-carrier communication (MCM) system based on orthogonal frequency division multiplex (OFDM) called fractional OFDM (FR-OFDM). The designed system introduces the angular parameter ,α, which is the paramter that relates Fourier transform (FT) and fractional Fourier transform (FRFT) together. Introduced in the Fourier Transform (FT), parameter α, allows to map the input signal onto a time-frequency domain. This mapping is achieved by applying a rotation directly to the kernel of Fourier transform.For the first time we have studied the impact of FR-OFDM on LI-Fi and VLC. What makes our work unique is that we carried out experiments with NI-USRP and LEDs and LED drivers. The experimental results approves the impact of FR-OFDM on the bit error rate (BER) for VLC systems. We ran experiements for different rotation angles of FRFT (α = 0.3π, 0.75π, 0.5π, 0.9π). We observed that the BER changes when the data is pre-modulated with FR-OFDM. For this experiment the two LEDS experienced a linear channel model with additive white Gaussian noise (AWGN). The measurement results shows that the best BER is acheived for rotation angle α = 0.5π.