PAPR of QPSK OFDM Modulation Schemes: A Comparative Study

Abstract

With the rapid growth in the field of telecommunication, there is a huge demand for increase in the bandwidth. Orthogonal Frequency Division Multiplexing (OFDM) is an advanced modulation technique suitable for the fourth-generation wireless communication due to the improved spectral efficiency and bandwidth. Besides these benefits of the OFDM, there are some major concerns which need to be taken care. Inter-symbol interference and the Peak to Average Power Ratio (PAPR) are the major drawbacks affecting the performance of the OFDM symbols. In this paper, a comparative study of PAPR of Quadrature Phase Shift Keying (QPSK) OFDM and the Offset QPSK OFDM has been done. Initially, OFDM symbols are generated with QPSK as the modulation techniques for the different symbol lengths ranging from 8 to 12 and the PAPR has been calculated for all combinations. The number of combinations resulting in a high value of PAPR was 16 for all the symbol lengths. The experiment was repeated with the offset QPSK for the same symbol lengths and the number of combinations resulting in a high value of PAPR was reduced to 8 for all symbol lengths. The mean of the QPSK and the Offset QPSK was computed. There was a reduction in the mean with the offset QPSK compared with the QPSK. The simulation results and the mean of the same have been discussed.

Keywords: Orthogonal Frequency Division Multiplexing (OFDM), Peak to Average Power Ratio (PAPR), Quadrature Phase Shift Keying (QPSK), Offset QPSK, Symbol length