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Self‐Organising Sensors for Wide Area Surveillance using the Max‐Sum Algorithm. Alex Rogers and Nick Jennings School of Electronics and Computer Science University of Southampton acr@ecs.soton.ac.uk Alessandro Farinelli Department of Computer Science University of Verona Verona, Italy
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Self‐Organising Sensors for Wide Area Surveillance using the Max‐Sum Algorithm Alex Rogers and Nick Jennings School of Electronics and Computer Science University of Southampton acr@ecs.soton.ac.uk Alessandro Farinelli Department of Computer Science University of Verona Verona, Italy alessandro.farinelli@univr.it
Overview • Self-Organisation • Landscape of Decentralised Coordination Algorithms • Local Message Passing Algorithms • Max-sum algorithm • Graph Colouring • Wide Area Surveillance Scenario • Future Work
Self-Organisation Sensors
Self-Organisation • Multiple conflicting goals and objectives • Discrete set of possible actions Agents
Self-Organisation • Multiple conflicting goals and objectives • Discrete set of possible actions • Some locality of interaction Agents
Self-Organisation • Multiple conflicting goals and objectives • Discrete set of possible actions • Some locality of interaction Maximise Social Welfare: Agents
Self-Organisation No direct communication Solution scales poorly Central point of failure Who is the centre? Decentralised self-organisation through local computation and message passing. • Speed of convergence, guarantees of optimality, communication overhead, computability Central point of control Agents
Landscape of Algorithms Optimality Complete Algorithms DPOP OptAPO ADOPT Message Passing Algorithms Sum-Product Algorithm Iterative Algorithms Best Response (BR) Distributed Stochastic Algorithm (DSA) Fictitious Play (FP) Communication Cost
Max-Sum Algorithm Find approximate solutions to global optimisation through local computation and message passing: A simple transformation: allows us to use the same algorithms to maximise social welfare: Factor Graph Variable nodes Function nodes
Graph Colouring Graph Colouring Problem Equivalent Factor Graph Agent function / utility variable / state
Graph Colouring Utility Function Equivalent Factor Graph
Wide Area SurveillanceScenario Dense deployment of sensors to detect pedestrian and vehicle activity within an urban environment. Unattended Ground Sensor
Energy Constrained Sensors Maximise event detection whilst using energy constrained sensors: • Use sense/sleep duty cycles to maximise network lifetime of maintain energy neutral operation. • Coordinate sensors with overlapping sensing fields. duty cycle time duty cycle time
Future Work • Continuous action spaces • Max-sum calculations are not limited to discrete action space • Can we perform the standard max-sum operators on continuous functions in a computationally efficient manner? • Bounded Solutions • Max-sum is optimal on tree and limited proofs of convergence exist for cyclic graphs • Can we construct a tree from the original cyclic graph and calculate an lower bound on the solution quality?