Research on Optimal Spectral Efficiency of Orthogonal Frequency Division Multiplexing Visible Light Communication-Radio FrequencyAggregation System Based on Finite Alphabet Inputs

So far, the information theory of Orthogonal Frequency Division Multiplexing (OFDM) Visible Light Communication (VLC) and Radio Frequency (RF) aggregation systems based on finite alphabet inputs is still unknown. Based on this situation, the achievable rate of unclosed expression and the lower bound with closed expression of OFDM VLC-RF aggregation system are derived, and the maximization of Spectral Efficiency (SE) based on achievable rate and its lower bound satisfying the constraints of average optical power and total electric power is studied. In this paper, the relationship between mutual information and Minimum Mean Square Error (MMSE) is used to deal with the rate partial derivative, and the double Water-filling algorithm is proposed to solve the maximization problem of spectral efficiency. Because the non-closed form of spectral efficiency leads to high computational complexity of the double Water-filling algorithm, this paper further studies the problem of spectral efficiency maximization with closed form and uses the interior point method to solve it. The simulation results show that the aggregation system has the advantages in communication performance compared with a single link, and the spectral efficiency based on the lower bound of achievable rate can be used as a good low complexity approximation of the spectral efficiency based on achievable rate.