SubCarrier Index - QAM, A New Hybrid Modulation Scheme for OFDM

Abstract

In this paper, we present a new hybrid modulation scheme based on quadrature amplitude modulation (QAM) and the idea behind frequency shift keying (FSK) for multicarrier systems. The proposed scheme is a request based modulation scheme where the QAM modulated message signal bits are encoded to different subcarriers based on the message signal bits. This way the subcarrier index also carries some message signal bits without its physical transmission. Perfect utilization of all subcarriers is assumed. The proposed scheme shows considerable improvement in spectral efficiency.