LAUSR

In this letter, a novel modulation scheme named orthogonal frequency division multiplexing (OFDM) using dual-mode three-dimensional (3D) constellation is proposed, which is capable of enhancing spectral efficiency (SE) and energy efficiency (EE) compared with the conventional 3D-OFDM. In the proposed scheme, the subcarriers are divided into two groups and modulated by dual-mode 3D constellations. Extra information bits are conveyed by the index pattern without energy consumption. Dual-mode 4- and 8-ary 3D constellations are designed and the signal points are distributed on the surface of Poincare sphere. Two detectors based on the maximum likelihood (ML) and log-likelihood ratio (LLR) are employed at the receiver. The simulation results demonstrate that error performance of the proposed scheme is significantly better than the conventional 3D-OFDM in high signal-to-noise ratio (SNR) region under the Rayleigh and Rician fading channels.