Lower Bounds on the Capacity of Discrete-Time Poisson Channels with Dark Current

Currently, no closed form for the capacity of discrete-time Poisson channels is known. In this paper, improved lower bounds on the capacity of discrete-time Poisson channels with dark current and average power constraint are obtained by using the family of gamma input distributions. The intuition of the method used in this work comes from Martinez and the new bounds are tighter than the previous lower bounds, especially at low transmit power levels.