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

Abstract

We consider transmitter-receiver (Tx-Rx) parameter optimization for a vertical underwater wireless optical communication link under misalignment conditions. The Tx is assumed to use a light-emitting diode while 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 the 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 FoV in the presence of pointing errors.

Bit-Error-Rate Performance of an Underwater Wireless Optical Link Under Misalignment and Turbulence Effects

“…where γ th denotes the optimal demodulation threshold (see [6] for details) and erfc(•) is the complementary error function. Given the very large SiPM gain, we reasonably assume that the Rx noise is dominated by shot noise [6]. Hence, assuming a relatively large OOK extinction ratio ξ, we have Ȋ0 ≈ ξ Ȋ1 and σ 2 n0 ≈ ξ σ 2 n1 .…”

“…A geometric loss model was proposed in [5] to investigate the impact of angular PEs on the link bit-error-rate (BER) performance. Also, the impact of Tx-Rx parameter optimization on minimizing the effect of PEs was studied in [6]. An experimentally verified statistical model for turbulence induced by air bubbles and temperature gradient was proposed in [7].…”

Outage probability analysis of a vertical underwater wireless optical link subject to oceanic turbulence and pointing errors

“…For relatively short link ranges, the use of angular multiple-input multipleoutput (MIMO) technique was proposed in [12,25], allowing increased robustness against PEs. In a recent work [26], we studied the effect of Tx-Rx parameter optimization on the performance of a vertical UWOC link subject to PEs.…”

“…In contrast to our previous work in [26], here we take into account the effects of turbulence and solar background noise, as well as using a laser diode (LD) at the Tx (instead of an LED source, as considered in [26]). Using a laser source results in a higher modulation bandwidth and a higher beam directivity.…”

Ergodic Capacity of a Vertical Underwater Wireless Optical Communication Link Subject to Misalignment

“…links. Considering the impact of random sea surfaces, [3] studied for both upload and download cases the interest of system parameter optimization. Also, [4] and [5] investigated a buoy-based UWOC downlink scenario, of which the latter extended in [6] to the case of employing multiple Txs and Rxs to improve channel capacity.…”