Mitigation of inter-symbol interference in non-line-of-sight ultraviolet communication using a photon counting image sensor

Scattering-based ultraviolet (UV) transmission is a crucial method for realizing non-line-of-sight (NLOS) optical communications. However, the inherent multipath characteristics of scattering channels can induce inter-symbol interference (ISI), significantly limiting signal transmission efficiency. To mitigate the effects of ISI on UV NLOS transmission, we propose a photon counting image sensor (PCIS) based receiver and the corresponding multiple scattering channel model. A photon counting reception mode for the PCIS has also been developed, incorporating two combining methods along with three types of counting-start instants that influence photon counting sampling. Simulation results reveal that the photon counting channels that account for ISI can be more accurately described as multipath channel models where the path with the maximum signal strength is not necessarily the shortest. Furthermore, the time-aligned equal gain selective combining method, when employed with a counting-start instant that maximizes photon counts in a single window, can concentrate a greater number of photons within one counting window, thereby substantially reducing the bit-error rate.