A Spectral and Energy Efficient Transmission Scheme for OFDM-based Communication Systems

This paper introduces a new frequency domain index modulation (FD-IM) technique for a general orthogonal frequency-division multiplexing (OFDM)-based communication system. The proposed technique has been designed to enhance both the spectral and the energy efficiencies of OFDM-based communication systems. In particular, we propose a novel coding scheme for the symbols to be transmitted that leverages the absence of transmission itself to encode a symbol. To the best of our knowledge, this is the first usage of such a coding scheme in the FD-IM OFDM domain. The expected benefits of the proposed solution are as follows: (i) It enhances the spectral efficiency, by increasing the total number of transmit bits for a given set of subcarriers; and, (ii) It improves the energy efficiency. To evaluate and compare the advantages of the proposed FD-IM technique with a baseline subcarrier-index modulated (SIM)-OFDM method, we first have derived the closed-form expressions of the energy gain and the transmit bit gain for both techniques, with respect to the equivalent standard modulation. The theoretical results show a significant enhancement in terms of improving both the spectral and the energy efficiencies of a general OFDM-based communication system. Moreover, we run an extensive experimental campaign to support our findings. Results are striking. For instance, with a binary phase-shift keying (BPSK) modulation, an energy gain of 57% and a transmit bit gain of 58% are experimentally observed. These promising results pave the way to improve the different extension versions of the SIM-OFDM technique that have been presented in the literature. Finally, we also pointed out some further applications of our proposed encoding to the general field of information processing.