Underwater sensor networks (UWSNs) can be applied in sea resource reconnaissance, pollution monitoring and assistant navigation, etc., and have become a hot research field in wireless sensor networks. In open and complicated underwater environments, targets (events) tend to be highly dynamic and uncertain. It is important to deploy sensors to cover potential events in an optimal manner. In this paper, the underwater sensor deployment problem and its performance evaluation metrics are introduced. Furthermore, a particle swarm inspired sensor self-deployment algorithm is presented. By simulating the flying behavior of particles and introducing crowd control, the proposed algorithm can drive sensors to cover almost all the events, and make the distribution of sensors match that of events. Through extensive simulations, we demonstrate that it can solve the underwater sensor deployment problem effectively, with fast convergence rate, and amiable to distributed implementation.

https://www.mdpi.com/1424-8220/14/8/15262/pdf

Particle Swarm Inspired Underwater Sensor Self-Deployment

Constrained-energy underwater acoustic nodes are typically connected via a multi-hop underwater acoustic network (MHUAN) to cover a broad marine region. Recently, protocols for efficiently connecting such nodes have received considerable attention. In this paper, we show that the time reversal (TR) process plays an important role in the medium access control (MAC) because of its physical capability to exploit the multi-path energy from the richly scattering underwater environment, as well as to focus the signal energy in both spatial and temporal domains. In MHUANs, with severe multi-path propagation at the physical layer, the active TR process spatially focuses the signals to the location of the intended receiver; this significantly diminishes the interference among parallel links. We propose an active TR-based MAC (TRMAC) protocol for MHUANs, with the aim of minimizing collision and maximizing channel utilization simultaneously. Furthermore, by considering the impact of the cross correlation between different links on the TR-based medium access, we derive the threshold of the link cross correlation to resolve collision caused by the high cross correlation between realistic links. We perform simulations using the OPNET and BELLHOP environments, and show that the proposed TRMAC results in significantly improved throughput, decreased delay, and reduced data drop ratio in MHUANs.

Time Reversal Based MAC for Multi-Hop Underwater Acoustic Networks

An efficient spread spectrum pulse position modulation scheme for point-to-point underwater acoustic communication

Underwater acoustic sensor networks (UASNs) have played a vital role in many security-sensitive applications like offshore oil exploration, tsunami forecast, and tactical surveillance. Due to the complex marine environment and harsh acoustic channel, UASNs face severe security challenges and attacks. Exploiting the multi-path energy from the richly scattering underwater environment, the time-reversal (TR) process can form the resonating strength based on the channel impulse response (CIR). Inspired by the natural link signature resulting from the spatial dependency of acoustic links, an authentication scheme using the maximum TR resonating strength is proposed, with the aim of effectively detecting the spoofing attacks in UASNs. To accommodate the time-varying nature of the underwater acoustic link, a database correlation method is exploited to capture the link CIR pattern over time for each link, which efficiently improves the accuracy of the authentication scheme using the TR process. Hence, the proposed algorithm enables each node to make the authentication decision based on maximum time-reversal resonating strength (MTRRS) locally with little overhead. It was evaluated by the probabilities of authentication, attack detection, and false alarm through extensive simulations. Finally, this MTRRS-based authentication was verified using the sea trial CIR data.

Physical Layer Node Authentication in Underwater Acoustic Sensor Networks Using Time-Reversal

Underwater acoustic sensor networks (UASNs) have played a vital role in many security-sensitive applications like offshore oil exploration, tsunami forecast, and tactical surveillance. Due to the complex marine environment and harsh acoustic channel, UASNs face severe security challenges and attacks. Exploiting the multi-path energy from the richly scattering underwater environment, the time-reversal (TR) process can form the resonating strength based on the channel impulse response (CIR). Inspired by the natural link signature resulting from the spatial dependency of acoustic links, an authentication scheme using the maximum TR resonating strength is proposed, with the aim of effectively detecting the spoofing attacks in UASNs. To accommodate the time-varying nature of the underwater acoustic link, a database correlation method is exploited to capture the link CIR pattern over time for each link, which efficiently improves the accuracy of the authentication scheme using the TR process. Hence, the proposed algorithm enables each node to make the authentication decision based on maximum time-reversal resonating strength (MTRRS) locally with little overhead. It was evaluated by the probabilities of authentication, attack detection, and false alarm through extensive simulations. Finally, this MTRRS-based authentication was verified using the sea trial CIR data. 

Underwater acoustic sensor networks (UASNs) consist of sensors that are deployed to perform collaborative monitoring of tasks over a given volume of water. The quality of the underwater acoustic link is highly unpredictable, since it mainly depends on fading and multipath, which are not easily modeled phenomena. This is return severely degrades the performance at higher layers such as extremely long and variable propagation delays. In addition, this variation is generally larger in horizontal links than in vertical ones. In this paper, we analyze a modulation scheme and associated receiver algorithms. This receiver design take advantage of the time reversal (phase conjugation) and properties of spread spectrum sequences known as Gold sequences. This technique improves the signal-to-noise ratio (SNR) at the receiver and reduces the bit error rate (BER). We then applied the phase conjugation to the case of network communication. We show that this approach can give almost zero BER for a 2-hop communication compared to single hop. This link layer information can be used at the network layer to formalize routing decisions. We show these improvements by means of analytical analysis and simulations.

F. Filali

Papers

Underwater Acoustic Sensor Networking Using Passive Phase Conjugation