  Photon counting detectors such as single-photon avalanche diode (SPAD) arrays
are commonly considered for reliable optical wireless communication at power
limited regimes. However, SPAD-based receivers suffer from significant dead
time induced intersymbol interference (ISI) especially when the incident photon
rate is relatively high and the dead time is comparable or even larger than the
symbol duration, i.e., sub-dead-time regime. In this work, we propose a novel
time-gated SPAD receiver to mitigate such ISI effects and improve the
communication performance. When operated in the gated mode, the SPAD can be
activated and deactivated in well-defined time intervals. We investigate the
statistics of the detected photon count for the proposed time-gated SPAD
receiver. It is demonstrated that the gate-ON time interval can be optimized to
achieve the best bit error rate (BER) performance. Our extensive performance
analysis illustrates the superiority of the time-gated SPAD receiver over the
traditional free-running receiver in terms of the BER performance and the
tolerance to background light.
