Performance enhancement of OFDM-SQ²AM in distorted channel environments

Abstract

In this letter, a new pulse shaped OFDM-Superposed Quadrature Quadrature Amplitude Modulation (OFDM-SQ²AM) system is proposed to reduce the inter-channel interference (ICI) as well as to maintain the orthogonalities between the OFDM subcarriers in the presence of the subcarrier frequency offset. Time and frequency dispersion properties of the proposed SQ²AM pulse shape are analyzed using the Heisenberg parameter and in-band energy function. Such properties of the proposed pulse are compared with those of a rectangular pulse and IOTA pulse. The BER performance of the pulse shaped OFDM-SQ²AM is compared with those of conventional OFDM-QAM and IOTA/OFDM-OQAM in the 3GPP ITU-R environment. Our simulation results indicate that the proposed OFDM-SQ²AM achieves higher spectral efficiency and power efficiency as compared to the other schemes and gives better robustness of the frequency dispersion.