Generalized Selecting Sub-carrier Modulation Scheme in OFDM System

Selecting Sub-carrier Modulation (SScM) scheme, in which the information bits are used for both modulation and active-sub-carrier selection, can be used to improve Energy Efficiency (EE) without deteriorating spectrum efficiency (SE) in Orthogonal Frequency Division Multiplexing (OFDM) system. In this paper, SScM is extended to Generalized Selecting Subcarrier Modulation (GSScM) to further improve EE and SE simultaneously. In the new scheme, more than one sub-carrier are active and an appropriate number achieving the optimal SE ratio is deduced. Further, the closed-forms and the asymptotic values of the optimal SE ratio, as well as the corresponding EE ratio are derived. Besides, a detection method is proposed to enhance the performance of Energy Detection (ED) and Log-likelihood Ratio (LLR) detection. Simulation results reveal that the enhanced detection method is better than the conventional detection methods by 1.5 dB to 3 dB at the cost of endurable complexity rise.