Throughput analysis of OFDM based wireless system with FrFT

Abstract

Fourier Transform (FT) is a well defined transform which has seen wide publicity and advantageous applications in the field of signal processing, optics and image processing. However, the real revolution in signal processing is given by its generalized form Fractional Fourier transform (FrFT) and has been utilized in this research work for wireless systems. The fractional variable given the freedom to transform the signal into time-frequency plane and hence FrFT is able to analyze the signal performance more precisely in fast time varying frequency selective channel. The main problem in the existing Orthogonal frequency division multiplexing (OFDM) systems is its inability to detect the change in frequency of signal with time under wireless channel. This non-detection of exact frequency of the signal at any instance of time in a wireless channel increases the bit error rate (BER) of the system. The aim of this research work is to use the FrFT in OFDM wireless system which is based on IEEE 802.11g protocol and capable of delivering 54 Mbps of bandwidth. Here, the throughput analysis of FrFT based OFDM system has been carried out in terms of BER, Signal to Noise Ratio (SNR), Inter Carrier Interference (ICI), Carrier Frequency Offset (CFO) and Peak-to-Average Power Ratio (PAPR) as the performance metrics. Hence, the contribution of this research work is develop an FrFT based OFDM system by using various modulation techniques for better performance and security of said system using the benefits of FrFT. The security of the signal transmitted on the wireless channel is not taken care in case of conventional OFDM system. Security of OFDM modulated signal in wireless domain has been enhanced as compared to existing OFDM system. In this proposed technique the FrFT is appended with the traditional OFDM system for encrypting the signal before transmitting. Now, instead of transmitting the plain OFDM signal in wireless domain; the OFDM modulated signal is encrypted with fractional variable using FrFT before transmission.