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Efficient Data Delivery with Packet Cloning for Underwater Sensor Networks

Underwater sensor networks (UWSNs) promises new opportunities for exploration of the oceans which cover more than 70% of the earth's surface. Researchers envision the deployment of dense networks of untethered sensors underwater for data acquisition to better understand the underwater environment, while military and security forces see the great potential of using this technology for mine reconnaissance, intrusion detection and surveillance. However, the underwater environment is extremely harsh and acoustic communications is currently the only physical layer technique considered viable. This presents a wireless channel that is totally different from the radio frequency channel that terrestrial wireless sensor networks technology has been designed for. Key challenges include the long propagation delay of the acoustic signal and the extremely volatile link quality. In this paper, we present a data delivery scheme that exploits nodes' proximity and their ability to overhear one another's transmissions to enhance packet delivery by selectively cloning packets as they are forwarded. Unlike directed or controlled flooding, our scheme is able to control the number of packet clones according to channel conditions and link quality to improve delivery while minimizing contention and energy expenditure.