Hidden Markov Model Based Signal Characterization for Weak Light Communication

Weak illumination by light emitting diode (LED) can be realized by either peak-power transmission at a low duty cycle or low-power transmission at a regular duty cycle. In this paper, we address the signal characterization and transmission rate of visible light communication for the latter case. We first characterize the LED nonlinear effect via a state transition model based on the experimental measurements. Then, we adopt hidden Markov model (HMM) to characterize the LED transmission under weak illumination. Based on the HMM, we propose a Monte Carlo method to compute the achievable transmission rate and apply Viterbi algorithm to detect the signals. The achievable transmission rates and detection performance of the HMM-based model are evaluated by simulation results. Moreover, both numerical and experimental results show lower bit error rate of the Viterbi algorithm compared with the per symbol detection.