Surface Based Anchor-Free Localization Algorithm for Underwater Sensor Networks

Abstract

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-surfacereflected 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.

Signal reflection-enabled geographical routing for underwater sensor networks

“…We refer to the inclusion of reflection points in the localized Delaunay triangulation as the LDel ୖ (V) planar graph. Recall from Figure 1 the LOS links may be blocked due to an obstacle or an unknown node, to account for this the node ܵ building the LDel ୖ (V) graph will determine which LOS links are blocked from the information obtained from network-discovery (stage 1) and calculate reflection points to the water surface and bottom to be used as temporary reference vertices in the LDel ୖ (V) graph by applying the SBR-AL technique [8]. After creating the planar graph, each routing node ܴ will apply (15) to select the next-hop that maximizes the network throughput.…”

“…In stage 1, the source node performs a k-hop node discovery to obtain the positions and movement information of all k-hops neighbors. This is done by incorporating a surface based reflected anchor-free localization (SBR-AL) scheme [8]. After obtaining the position information, the node will then determine the geocast region R (cubic boundary) centered on the destination node D j , based on the node degree and movement information (speed and direction) of the destination.…”

“…In this section we highlight the potential of multi-hop routing with directional antennas when utilizing NLOS links. Given the lack of GPS and anchor information in the networking scenario in Figure 1, we have adopted an anchor-free relative localization scheme [8], which we employ to support geographical routing and directional communication.…”

Surface-Reflection-Based Communication and Localization in Underwater Sensor Networks

“…To overcome the limitations of present systems, this article presents a surface-based reflection (SBR) scheme [Emokpae and Younis 2011] that uses a switch-beamed acoustic directional antenna for communication. SBR is designed to operate in shallow water regions (with depths down to 200m) and uses the reflections from the water surface (or bottom) to enable non-line-of-sight (NLOS) communication links.…”

“…The second scheme does not require an exchange of SBR range measurements between neighbors and opts to only consider one neighbor at a time, which we refer to as surface-based reflected directed anchor-free localization (SBR-DAL). A preliminary version of the SBR-DAL algorithm can be found in Emokpae and Younis [2011]. The third variant, which we call surface-based reflected enhanced anchor-free localization (SBR-EAL), aims at enhancing the directed localization scheme.…”