Multi-Input UV Communication With Adaptive Gain Adjustment

In this paper, an on-off keying based multi-input superimposed transmission for ultraviolet communication is investigated by characterizing the multi-input transmission as a hidden Markov model. A Gaussian approximation for the summation of sampled signal is characterized and the corresponding log-likelihood ratio computation method is proposed for the subsequent message-passing decoder. The profile of the PMT output amplitude under different supply voltage levels is experimentally measured and fitted. Based on the fitted results, we predict the optimal PMT gain and its corresponding supply voltage that minimizes the bit error rate (BER) for the signal detection. In the experiments, the derived supply voltage by the proposed approach is close to the optimal value via exhaustive searching method, and the BER of the proposed approach is close to that of exhaustive search.