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Wireless Sensor Network Control: Drawing Inspiration from Complex Systems LOGO LOGO Pavlos Antoniou and Andreas Pitsillides Networks Research Laboratory, Computer Science Department, University of Cyprus E-mail: [email protected], [email protected] INTRODUCTION NATURE & BIOLOGICALLY-INSPIRED SYSTEMS • Wireless Sensor Networks (WSNs) consist of tiny low-cost, lowpower unsophisticated sensor nodes. • Complex systems can draw inspiration from natural and biological processes to develop techniques and tools for building robust, selfadaptable and self-organizing network information systems. • Fundamental aim: Produce globally meaningful information from raw local data obtained by individual sensor nodes based on 2 goals: • Study of Nature/Biologically-Inspired Systems relies on: - Swarm Intelligence (ants, bees, birds, etc.) save energy, maximize network lifetime, Collective ant foraging for routing [4] (Ant Colony Algorithms in Swarm Intelligence) maintain connectivity. • Constraints: Computation capability, memory space, communication bandwidth and energy supply. • Congestion in WSNs: aggregated incoming traffic flow > outgoing channel capacity, channel contention and interference in shared communication medium. • Consequences of congestion in WSNs: energy waste, throughput reduction, information loss lower QoS / network lifetime. Congestion Control mechanisms goals: prolong network lifetime + provide adequate QoS levels RELATED WORK • Protocols and implementation in WSNs infer congestion based on methodologies known from the Internet: Fusion [1]: queue length, channel contention. CODA [2]: present/past channel conditions, buffer occupancy. SenTCP [3]: local inter-arrival packet time, service time, buffer occupancy. COMPLEX SYSTEMS IN GENERAL • Modern information systems are complex: sheer size, large number of nodes/users, heterogeneous devices, complex interactions among components difficult to deploy, manage, keep functioning correctly through traditional techniques. • Need for: robust, self-organized, self-adaptable, self-repairing, decentralized networked systems Complex Systems Science • Complex Systems Science studies how elements of a system give rise to collective behaviors of the system, and how the system interacts with environment. • Focus on: - elements (nodes), - wholes (networks), and - relationships (links, information dissemination). - Artificial Immune system - Evolutionary (genetic) algorithms - Cell and Molecular Biology Blood pressure regulation for the control of information flow [5] (Cell Biology) • Global properties (self-organization, robustness, etc.) are achieved without explicitly programming them into individual nodes. These properties are obtained through emergent behavior even under unforeseen scenarios, environmental variations or deviant nodes. OUR DIRECTION • Natural and Biological Systems can provide strong research framework beyond classic mathematical (analytical) models. • Network control models and techniques intended for WSNs need to possess the properties arisen from the aforementioned systems: - Self-* properties: self-organization, self-adaptation, selfoptimization, self-healing, etc. - Robustness and Resilience (tolerance against failures or attacks) - Decentralized operation. • Develop techniques that extract hypotheses about interaction networks apply them for the control of stressful congestion conditions in challenging sensor environment. CONCLUSIONS AND FUTURE WORK • Complex System Science represents a radical shift from traditional algorithmic techniques. • Complex Natural and Biological Systems can provide efficient solutions to a wide variety of problems in a sensor environment Promise for the Future. • Nature-inspired and bio-inspired techniques such as ant colony algorithms [4] and cell biology-based approaches [5] respectively have achieved remarkable success in computer science problems of search and optimization. • Our Aim: Capture successful natural/biological mechanisms and exploit their properties to control the complexity of stressful congestion conditions in Wireless Sensor Networks. REFERENCES [1] B. Hull, K. Jamieson and H. Balakrishnan, “Mitigating Congestion in Wireless Sensor Networks,” Proceedings of the 2nd International Conference on Embedded Networked Sensor Systems, ACM SenSys 2004, November 2004, pp. 134-147. [2] C.-Y. Wan, S. B. Eisenman and A. T. Campbell, “CODA: Congestion Detection and Avoidance in Sensor Networks,” Proceedings of the 1st International Conference on Embedded Networked Sensor Systems, ACM SenSys 2003, November 2003, pp. 266-279. [3] C. Wang, K. Sohraby, and B. Li., “SenTCP: A hop-by-hop congestion control protocol for wireless sensor networks,” IEEE INFOCOM 2005, March 2005. [4] M. Bundgaard, T. C. Damgaard, F. Dacara, J. W. Winther and K. J. Christoffersen, “Ant Routing System – A routing algorithm based on ant algorithms applied to a simulated network”, Report, University of Copenhagen, 2002. [5] F. Dressler, B. Kruger, G. Fuchs and R. German, “Self-organisation in Sensor Networks using Bio-Inspired Mechanisms,” Proceedings of 18th ACM/GI/ITG International Conference on Architecture of Computing Systems, March 2005, pp. 139-144.