SUSHMITA DAS et.al. : PERFORMANCE IMPROVEMENT OF OFDM SYSTEM BY PEAK TO AVERAGE POWER REDUCTION THROUGH PULSE SHAPING TECHNIQUE

OFDM is a form of multicarrier modulation technique with high spectral efficiency, robustness to channel fading, immunity to impulse interference, uniform average spectral density capacity of handling very strong echoes and non-linear distortion. Despite of its many advantages, one major disadvantage of OFDM is that the time domain OFDM signal which is a sum of several sinusoids leads to high peak to average power ratio (PAPR). The peak to average power ratio of the time domain envelope is an important parameter at the physical layer of the communication system using OFDM signaling. The signals must maintain a specified average energy level in the channel to obtain the desired Bit-error-rate. Pulse shaping techniques are very effective and mitigate problems associated with PAPR. In this paper conventional pulse shapes like Raised Cosine (RC), and sinc Power (SP) pulses are modified as Modified Raised Cosine Pulse (MRC) and Improved sinc Power pulse (ISP) introducing design parameter ‘d’ and amplitude parameter ‘a’ etc . The proposed method has fast decaying rate by decreasing the lobes of sinc function and its implementation complexity is also less. In this paper OFDM system performance measures like Complementary Cumulative Distribution Function (CCDF) of PAPR and bit error rate (BER) are analyzed through MATLAB simulation which proves the efficacy of the proposed pulse shaping scheme. It was observed from the performance curves using ISP pulse shaping filter at the OFDM transmitter’s end outperforms others.