Parameter Optimization for an Underwater Optical Wireless Vertical Link Subject to Link Misalignments

We consider transmitterreceiver (TxRx) parameter optimization for a vertical underwater wireless optical communication link under misalignment conditions. The Tx is assumed to use a light-emitting diode, whereas the Rx uses a silicon photomultiplier that allows a high Rx sensitivity. We consider two typical application scenarios and investigate optimization of the Tx and Rx parameters to optimize the link performance in terms of outage probability. We derive accurate analytical expressions for the distribution of the channel attenuation accounting for link misalignments, which allows for the evaluation of the link performance in terms of bit-error-rate and outage probability without resorting to costly Monte Carlo simulations. Through numerical results, we show and discuss the impact of parameter optimization on the link performance in different link configurations and for various misalignment conditions. In particular, the presented results show the significant performance improvement resulting from optimizing the Tx beam divergence and the Rx field-of-view in the presence of pointing errors.