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Stream Processing in Networks of Smart Devices. Holger Ziekow, Lenka Ivantysynova. Institute of Information Systems Humboldt University of Berlin, Germany. Stream Processing on Smart Items (Motivation).
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Stream Processing in Networks of Smart Devices Holger Ziekow, Lenka Ivantysynova Institute of Information Systems Humboldt University of Berlin, Germany
Stream Processing on Smart Items (Motivation) • Business Applications aim to integrate data from smart devices (e.g. sensors and RFID data) • Sensor and RFID data have the properties of data streams (Stream, Aurora) • Processing streams on the device layer can extend device lifetime by reducing communication (Courgar)
Stream Query plan S2 S1 Stream Processing on Smart Items (Motivation) • Smart devices are commonly battery powered and therefore very energy constrained • Communicating is much more energy consuming than calculations (sending 1 bit 1000 CPU instructions) Data processing in the network is favorable How to map?
Querying in the Network Challenges: • Devices vary in • Position in the network. • Free memory. • Operators network position influencesenergy consumption. • Memory influences data accuracy. • Mapping problem is NP hard.(Rectilinear Steiner Tree Problem) • Query plans may have to be modified.
Stream Processing on Smart Items (Optimized Mappings) • Finding an optimal mapping is an NP-hard problem • We define a metric to measure a mappings quality. This metric can be used in optimization algorithms Energy Data quality Parameters to mutate: • Target devices for the query operator (m) for the given query plan (q) • Operators in the query plan (q) which can subsequently be calculated
Stream Processing on Smart Items (Test Results) • We used our metric and a genetic algorithm to find good mappings of query plans • Tests show that good results can be found relatively fast • In manual checks the generated mapping can be proven as reasonable Cost Approximation using a genetic algorithm Optimization steps
Stream Processing on Smart Items (Test Results) Query: AGG(JOIN(Src1,Src2)) Memory Usage: AGG = 50 JOIN = 70 Memory
Stream Processing on Smart Items (Test Results) Query: AGG(Src1,Src2,Src3,Src4) Mapped Query: AGG(AGG(Src1,Src4),AGG(Src2,Src3))
Future Work • Additional optimization parameters • Message delay. • Value based errors. • Node specific energy consumption. • Tuning the optimization algorithm. • Integration of different routing algorithms.