INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & MANAGEMENT NEW PHASE SEQUENCE PTS AND COMPANDING USED TO REDUCE PAPR IN OFDM SYSTEM

Orthogonal Frequency-division multiplexing or multicarrier transmission scheme is an attractive technique for high-bit-rate communication systems. It has been widely used in modern wireless communication because of its high data rate, immunity to delay spread and frequency spectral efficiency and other advantages. Besides these advantages, one of the major drawbacks of OFDM is the high Peak-to- average-power ratio (PAPR) of the Transmitter's output signal, as it restricts the system performance. One of the effective methods used for reducing peak to average power ratio (PAPR) in OFDM systems is partial transmit sequence (PTS). In the conventional PTS (CPTS) several inverse fast Fourier transform (IFFT) operations and complicated calculation to obtain optimum phase sequence, increase the computational complexity of C-PTS. In this paper, we propose new a technique i.e., new phase sequence PTS and companding in cascaded form. First new phase sequence is used to reduce the number of IFFT operations to half at the expense of a slight PAPR degradation. Simulations are performed with QPSK modulation with OFDM signal and Saleh model power amplifier. The effects of digital pre-distortion (DPD) to increase the linearity and efficiency of the Saleh model power amplifier (PA) are also examined and then next we will add companding techniques which will again used to reduce PAPR in OFDM.