Improving Opportunistic Data Dissemination via Selective Forwarding

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Support for Mobility and Fault Tolerance in Mykil

Abstract — This paper describes the support provided for mobility and fault tolerance in Mykil, which a key distribution protocol for large, secure group multicast. Mykil is based on a combination of group-based hierarchy and key-based hierarchy systems for group key management. Important advantages of Mykil include a fast and efficient rekeying operation for large group sizes, continuous availability of the key management service in a disconnected network environment, an ability to map group structure to the underlying network infrastructure, fault tolerance, and support for member mobility and smaller hand-held devices. Mobility support in Mykil allows mobile group members to access a multicast service without any need for going through an extensive registration process. Fault tolerance support allows group members to access a multicast service despite communication failures, network partitions, and node failures in the network. A prototype of Mykil has been implemented. The paper describes this implementation and reports on the performance measured from this implementation. I

A sensor based tracking system using witnesses

Abstract — Search and rescue of people in emergency situations, e.g. lost hikers, stranded climbers, or injured skiers has been difficult due to lack of information about their location at various times. Current location and tracking systems require a connected network via satellites, GSM base stations, or mobile devices. This requirement severely limits their applicability, particularly in remote wilderness areas where maintaining a connected network is very difficult. This paper proposes a new tracking system called Cenwits that is based on sensors that use RF for communication and emit beacons from time to time. When two sensors are in the range of one another, they record the presence of each other and exchange the information they recorded earlier. A sensor dumps all its information to an access point, whenever it is in the range of one. Important advantages of Cenwits include a looselycoupled system that does not require network connectivity, power efficiency, and low cost. A preliminary prototype of Cenwits is being built using Berkley Mica2 Motes. The paper reports results from this preliminary prototype. I

Cenwits: A sensor-based loosely coupled search and rescue system using witnesses

Abstract — This paper describes the design, implementation and evaluation of a search and rescue system called CenWits. CenWits uses several small, commonly-available RF-based sensors, and a small number of storage and processing devices. It is designed for search and rescue of people in emergency situations in wilderness areas. A key feature of CenWits is that it does not require a continuously connected sensor network for its operation. It is designed for an intermittently connected network that provides only occasional connectivity. It makes a judicious use of the combined storage capability of sensors to filter, organize and store important information, combined battery power of sensors to ensure that the system remains operational for longer time periods, and intermittent network connectivity to propagate information to a processing center. A prototype of CenWits has been implemented using Berkeley Mica2 motes. The paper describes this implementation and reports on the performance measured from it. I