Cooperative Caching in Wireless Multimedia Sensor Nets

Cooperative Caching in Wireless Multimedia Sensor Nets Nikos Dimokas1 Dimitrios Katsaros1,2 (presentation) Yannis Manolopoulos1 Informatics Dept., Aristotle University, Thessaloniki, Greece Computer & Communication Engin Dept., University of Thessaly, Volos, Greece 3rd MobiMedia Conference, Nafpaktos, Greece, 27-29/August/20071 Wireless Sensor Networks (WSNs) Wireless Sensor Networks features • Homogeneous devices • Stationary nodes • Dispersed network • Large network size • Self-organized • All nodes acts as routers • No wired infrastructure • Potential multihop routes WSNs - Applications • Applications • Habitat monitoring • Disaster relief • Target tracking • Agriculture Wireless Multimedia Sensor Nets (WMSNs) Cheap CMOS cameras: Cyclops imaging module is a light-weight imaging module which can be adapted to MICA2 or MICAz sensor nodes What’s so special about WMSNs ? • [Ian Akyildiz: Dec’06] We have to rethink the computation-communication paradigm of traditional WSNs • which focused only on reducing energy consumption • WMSNs applications have a second goal, as important as the energy consumption • • delivery of application-level quality of service (QoS) mapping of this requirement to network layer metrics, like latency • This goal has (almost) been ignored in mainstream research efforts on traditional WSNs What’s so special about WMSNs ? • Resource constraints • sensor nodes are battery-, memory- and processing-starving devices • Variable channel capacity • multi-hop nature of WMSNs implies that wireless link capacity depends on the interference level among nodes • Multimedia in-network processing • sensor nodes store rich media (image, video), and must retrieve such media from remote sensor nodes with short latency Our proposal … • Cooperative Caching: NICOCA protocol • multiple sensor nodes share and coordinate cache data to cut communication cost and exploit the aggregate cache space of cooperating sensors • Each sensor node has a moderate local storage capacity associated with it, i.e., a flash memory Relevant work (1/2) • Caching in operating systems, in databases, on the Web • No extreme resource constraints like WMSNs • Caching for wireless broadcast cellular networks • More powerful nodes, and one-hop communication with resource-rich base stations • Most relevant research works: • cooperative caching protocols for MANETs • GroCoca: organize nodes into groups based on their data request pattern and their mobility pattern • ECOR, Zone Co-operative, Cluster Cooperative: form clusters of nodes based either in geographical proximity or utilizing widely known node clustering algorithms for MANETs 10 Relevant work (2/2) Protocols that deviated from such approaches: • CacheData: intermediate nodes cache the data to serve future requests instead of fetching data from their source • CachePath: mobile nodes cache the data path and use it to redirect future requests to the nearby node which has the data instead of the faraway origin node • Amalgamation of them: the champion HybridCache cooperative caching for MANETs • One caching work on WSNs • concerns the placement of caches 11 Our contributions … • Definition of a metric for estimating the importance of a sensor node, which will imply short latency in retrieval • Description of a cooperative caching protocol which takes into account the residual energy • Datum discovery and cache replacement component subprotocols • Performance evaluation of the protocol and comparison with the state-of-the-art cooperative caching for MANETs, with J-Sim 12 Summary • Wireless Multimedia Sensor Networks (WMSNs) • Unique features of WMSNs call for protocol designs that provide application-level QoS • Cooperative caching protocol, NICoCa, suitable for WMSNs • NICOCA evaluation with J-Sim and comparison to the state-of-the-art protocol • NICOCA can: • • reduce the global hits at an average percentage of 50% increase the remote hits (due to the effective sensor cooperation) at an average percentage of 40% 34 Important references I Akyildiz, T Melodia, and K R Chowdhury A survey of wireless multimedia sensor networks Computer Networks, 51:921-960, 2007 Y Diao, D Ganesan, G Mathur, and P Shenoy Rethinking data management for storagecentric sensor networks Proceedings of the Conference on Innovative Data Systems Research (CIDR), pp 22-31, 2007 S Nath and A Kansal FlashDB: Dynamic selftuning database for NAND flash Proceedings of the ACM International Conference on Information Processing in Sensor Networks (IPSN), pp 410-419, 2007 L Yin and G Cao Supporting cooperative caching in ad hoc networks IEEE Transactions on Mobile Computing, 5(1):77-89, 2006 35 Thank you for your attention! Any questions? 36