End-to-End Performance Analysis of Underwater Optical Wireless Relaying and Routing Techniques Under Location Uncertainty

TL;DR

The paper addresses the challenge of achieving high-speed, low-latency underwater optical wireless networking in the presence of location uncertainty. It develops an uncertainty-disk model and derives adaptive divergence angles for PAT with perfect, uncertain, and absent location information, enabling robust end-to-end links. Through closed-form analyses of Decode-and-Forward and Amplify-and-Forward relaying, along with centralized and distributed routing schemes (including LiPaR), it demonstrates how range-beamwidth tradeoffs, PAT, and network information availability shape E2E rate, BER, and power. Simulation results across water types and network densities show that PAT-enabled adaptive beamwidth substantially improves performance, DF relaying yields higher E2E rates while AF can be more power-efficient in some cases, and LiPaR provides strong distributed performance where global routing is impractical.

Abstract

On the contrary of low speed and high delay acoustic systems, underwater optical wireless communication (UOWC) can deliver a high speed and low latency service at the expense of short communication ranges. Therefore, multihop communication is of utmost importance to improve degree of connectivity and overall performance of underwater optical wireless networks (UOWNs). In this regard, this paper investigates relaying and routing techniques and provides their end-to-end (E2E) performance analysis under the location uncertainty. To achieve robust and reliable links, we first consider adaptive beamwidths and derive the divergence angles under the absence and presence of a pointing-acquisitioning-and-tracking (PAT) mechanism. Thereafter, important E2E performance metrics (e.g., data rate, bit error rate, transmission power, amplifier gain, etc.) are obtained for two potential relaying techniques; decode & forward (DF) and optical amplify & forward (AF). We develop centralized routing schemes for both relaying techniques to optimize E2E rate, bit error rate, and power consumption. Alternatively, a distributed routing protocol, namely Light Path Routing (LiPaR), is proposed by leveraging the range-beamwidth tradeoff of UOWCs. LiPaR is especially shown to be favorable when there is no PAT mechanism and available network information. In order to show the benefits of multihop communications, extensive simulations are conducted to compare different routing and relaying schemes under different network parameters and underwater environments.

Figures (14)

• Figure 1: Illustration of UOWNs with multiple sinks.
• Figure 2: Demonstration of the system model and range-beamwidth tradeoff.
• Figure 3: Adaptive beamwidths for PAT mechanisms.
• Figure 4: Adaptive half-beamwidths under the receiver location uncertainty.
• Figure 5: Illustration of adaptive beamwidth calculations under the transceiver location uncertainty.