Intelligent Index Recognition for OFDM With Index Modulation in Underwater OWC Systems

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) is a promising scheme for underwater optical wireless communication (UOWC) due to its high power efficiency and flexibility. In this letter, we propose and experimentally demonstrate an intelligent index recognition scheme for OFDM-IM in UOWC systems. Considering the unique activation patterns of OFDM-IM with different numbers of activated subcarriers within each subblock, the signal histograms in the frequency domain are adopted as the features for recognition. Moreover, various machine learning or deep learning algorithms are further utilized as the tools to perform intelligent index recognition based on the distinctive frequency-domain histograms. Experimental results demonstrate the feasibility of the proposed intelligent index recognition scheme for OFDM-IM in UOWC systems. In addition, the impact of the number of bins and the number of symbols on the performance of index recognition is also studied.