Subcarrier-Interactive Dual-Mode OFDM

In this letter, a novel dual-mode index modulation aided orthogonal frequency division multiplexing (DM-OFDM) scheme called subcarrier-interactive (SI-) DM-OFDM is proposed. In the SIDM-OFDM, each subcarrier pair conveys the same QAM modulated symbols to achieve a diversity gain. At the receiver, a low complexity (LC) signal detection algorithm is proposed, i.e., SIDM-OFDM-LC, where each subcarrier interacts with other subcarriers in the same subblock as complementary and non-complementary states to improve BER performance. Moreover, Euclidean distance (ED) of the received signal and channel-noise matrix (CNM) based signal detection algorithms are employed for demodulation, namely SIDM-OFDM-ED and SIDM-OFDM-CNM, respectively. Simulation results confirm that the SIDM-OFDM with the proposed three signal detection algorithms achieves a significantly better BER performance than the existing DM-OFDM scheme at the same spectral efficiency. Also, it is revealed that the SIDM-OFDM-LC reduces the signal detection cost compared to the other two proposed detectors.

I. Introduction

Dual-mode index modulation aided orthogonal frequency division multiplexing (DM-OFDM) is proposed in [1], [2] to improve the spectral efficiency of the OFDM with index modulation (OFDM-IM) [3], [4] via activating all subcarriers and mapping subcarriers within each subblock by two distinguishable QPSK/QAM constellation alphabets.