Space-frequency-mode multi-dimensional hybrid modulation in OAM based MIMO-OFDM systems

A new modulation scheme, referred to as space-frequency-mode multi-dimensional hybrid modulation (SFMHM), is proposed to be integrated with multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system in this paper. The key idea of SFMHM is to map a block of information bits to two information carrying units: 1)symbols chosen from a constellation diagram and 2)a subset chosen from all possible combinations of antennas, orbital angular momentum (OAM) modes and subcarriers, which means that only a part of antennas, OAM modes and subcarriers will be activated at any given time. Specifically, the use of the second part will add three additional dimensions to conventional two-dimensional (2-D) amplitude/phase modulation techniques, which will improve the achievable rate significantly. For SFMHM scheme, we propose a computationally efficient mapping method by taking advantage of combinadic representation in combinatorial system, and we further study the achievable rate. Finally, simulation results show that, for the same configuration at the transmitter, SFMHM can achieve higher rate compared with conventional MIMO-OFDM.