Most communication and localization algorithms in underwater environments have been constrained by dependencies on the Line Of Sight (LOS), which is hard to guarantee due to the inherent node mobility. This constraint hinders node discovery and ad hoc formation in underwater networks and limits the performance of routing protocols. This article introduces a novel Surface-Based Reflection (SBR) model that uses a homomorphic deconvolution technique to establish water-surface-reflected communication links. We then propose a Surface-Based Reflection Anchor-free Localization (SBR-AL) algorithm that can be employed by the individual nodes to establish a relative coordinate system. Our approach also employs a switch-beamed directional antenna model that allows each node to use the LOS estimated from SBR-AL to enable directional communication which is beneficial for higher Signal-to-Noise Ratios (SNR). The relative locations can facilitate the various network operation functions such as geo-routing and collision-free medium access. The simulation results confirm the effectiveness of the proposed approach.

The 3-D nature of the underwater environment has made geographical-routing a popular choice in underwater acoustic sensor networks (UW-ASNs). A geographical (geo) routing protocol works by using the position information to find the best route from a source to a destination. These algorithms, often try to minimize the line-of-sight (LOS) Euclidean distance between hops, which is not always possible due to blocked LOS paths resulting in voids (or local minimum). Thus, traditional geo-routing algorithms typically employ a face routing recovery scheme that allows for back-tracking when blocked LOS links are encountered, which adds delay to the data delivery time. To overcome this, we propose a geo-routing scheme that does not depend on the LOS and utilize directional antennas to incorporate surface-reflected non-line-of-sight (NLOS) links in the routing process. Furthermore, the proposed algorithm is configured to optimize the route selection to achieve maximum network throughput. Simulation results are provided to validate the performance of the proposed algorithm.

Underwater communication relies on acoustic links due to its long propagation and low attenuation properties. Despite the advantages of using acoustic links over radio frequency (RF), the major drawback is the limited bandwidth of the acoustic spectrum. To circumvent this, we advocate the use of directional antennas rather than the traditional omni-directional antennas to boost the network throughput by taking advantage of the spatial spectrum. In this paper, we analyze the network throughput for shallow water communication with directional antennas. Unlike traditional line-of-sight (LOS) directional communication, our analysis will aim to factor in non-line-of-sight (NLOS) links in the throughput analysis. We will be focusing on two NLOS links; namely refracted-surface-reflected (RSR) and refracted-bottom-reflected (RBR) to study the multipath effects on the network throughput. Simulation experiments are also provided to validate the analytical results.

Localization in underwater environments has been constrained by the dependencies on the line of sight (LOS) due to the challenging variability's of the environment. This dependency hinders node discovery and ad-hoc formation in underwater networks and limits the performance of routing protocols. Most proposed algorithms in the literature rely on anchor nodes that are at fixed positions to serve as reference points, which is not practical in many applications. This paper introduces a novel approach to the localization problem that allows for node discovery without depending on the LOS and any fixed reference nodes. In the proposed surface-based reflection anchor-free localization (SBRAL) algorithm all nodes will apply homomorphic deconvolution to establish a water-surface-reflected communication link. SBRAL then creates a relative coordinate system where every node in the network identifies others nodes by increasing the SBRAL transmit angle and using the reflection points on the water surface as temporary reference points. The simulation results confirm the effectiveness of the proposed SBRAL algorithm.

In an underwater environment signal propagation for the acoustic channel is subject to major multipath effect. Therefore, most underwater communication schemes require that the position of the transmitter or receiver is fixed while using directional antennas in order to ensure high signal-to-noise ratio. However, such a requirement hinders node discovery and ad-hoc formation of underwater networks and restraints communication between autonomous underwater vehicles (AUVs) where node locations change over time. This paper proposes a novel approach to underwater communications by relying on the water surface to establish communication links. The proposed surface-based reflection (SBR) model works by requiring the transmitting node to direct its energy towards the water surface. The receiver then applies homomorphic deconvolution techniques to determine the channels impulse response used in obtaining the reflected signal. The receiver is then able to determine the location of the transmitter by triangulating the transmitted and reflected signals with respect to the water surface. Simulation experiments are provided to validate the SBR approach.