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A Sensor Equipped Aquatic (SEA) swarm is a sensor cloud that drifts with water currents and enables 4-D (space and time) monitoring of local underwater events such as contaminants, marine life, and intruders. The swarm is escorted on the surface by drifting sonobuoys that collect data from the underwater sensors via acoustic modems and report it in real time via radio to a monitoring center. The goal of this study is to design an efficient anycast routing algorithm for reliable underwater sensor event reporting to any surface sonobuoy. Major challenges are the ocean current and limited resources (bandwidth and energy). In this paper, these challenges are addressed, and HydroCast, which is a hydraulic-pressure-based anycast routing protocol that exploits the measured pressure levels to route data to the surface sonobuoys, is proposed. This paper makes the following contributions: a novel opportunistic routing mechanism to select the subset of forwarders that maximizes the greedy progress yet limits cochannel interference and an efficient underwater dead end recovery method that outperforms the recently proposed approaches. The proposed routing protocols are validated through extensive simulations. [ABSTRACT FROM PUBLISHER]

In wireless sensor networks (WSNs), hierarchical routing protocol is commonly used for energy efficiency. In particular, the TEEN (Threshold sensitive Energy Efficient sensor Network) protocol is used widely as a basic clustered multihop routing protocol. However, energy efficient routing protocols without proper security suffer from many security vulnerabilities. Hence, in this paper, we propose a hybrid key scheme specially for the TEEN protocol: a symmetric key scheme for the intracluster and a public key scheme for the intercluster. The simulation results show that network lifetime of the proposed hybrid key scheme decreases about 8% than the TEEN protocol and about 4% compared with the TEEN protocol with symmetric key scheme. On the other hand, a hybrid key scheme provides better probability of successful transmission than that of the symmetric key scheme. [ABSTRACT FROM AUTHOR]