OpticsRadio Hybrid Single Frequency Network for Digital Television Terrestrial Broadcasting The visible light communication (VLC) system works well for indoor scenarios if the indoor coverage performance of the existing digital television terrestrial broadcasting (DTTB) system is not satisfactory. In this paper, we propose a hybrid system called the opticsradio hybrid single frequency network (SFN) with wide and deep coverage for DTTB, realizing seamless connection between outdoor and indoor. The hybrid system maintains the consistency of the baseband signal as well as the existing SFN structure of DTTB, and the hybrid receiver with antenna and photodiode can receive radio or optical signal individually or simultaneously. Furthermore, other functions of DTTB like positioning can also be improved.

Performance Analysis on Hybrid OOKandOFDM Modulation in VLC System Since visible light communication (VLC) could support highspeed broadband transmission and be combined with existing illumination system, it is an optional technology for multimedia broadcasting, especially for indoor scenario. Furthermore, hybrid modulation could be applied in VLC system to assist data transmission or expand new functions. Researches and experiments show that conventional onoff key (OOK) and orthogonal frequency division multiplexing (OFDM) could be implemented successfully in VLC system respectively, thus it seems that a direct adding of OOK and OFDM signal is a feasible method for hybrid modulation. However, nonlinearity of electrooptical converting in VLC transmitter makes the relationship between transmission performance and amplitude of OOK or OFDM signal different from that in radio frequency (RF) system. In this paper, a mathematical model is built to analyze its performance and predict the bit error rate (BER) using OOK and OFDM signal amplitude in a given VLC system in order to find proper parameters for higher transmission quality. Simulation is also implemented to prove the validity and accuracy of the model.