Institute of Applied Microelectronics and Computer Engineering

1. Institute of Applied Microelectronics and Computer Engineering Energy Aware Self Organized Communication in Complex NetworksJakob Salzmann, Dirk TimmermannSPP 1183 Third ColloquiumOrganic Computing,14.-15.09.2006, Stuttgart University of Rostock

2. DFG 1183 Organic Computing Outline • Project introduction • OC principles in research • Current work • Future work • Conclusion

3. DFG 1183 Organic Computing Project introduction (1) Sensor network = paradigm of a complex network Task: • Collection of sensor data at many locations • Transmit collected data to sink Applications: • Forest fire surveillance • Movement of cars • Detection of volcanic activity • Intelligent house

4. DFG 1183 Organic Computing ? ! Active node Sink Transmission range Sensing range Project introduction (2) Properties of a sensor network: • High node count • Random node distribution • Wireless communication Properties of a node: • Transmission range • Sensing range • Limited energy per node • Typical problems: • Energy limits lifetime • Node failure rate high • Centralized control infeasible

5. DFG 1183 Organic Computing Project introduction (3) Our goal: Increase lifetime and robustness of sensor networks using self-organized communication and organic principles Lifetime and robustness of a sensor network A network „lives“ completely: • iff phenomens still can be detected in each observed location • iff messages from acquiring nodes can reach the sink A structure of a sensor network is robust: • iff deliberate and random node failures up to a given extent do not impact lifetime

6. DFG 1183 Organic Computing OC principles in research • Role assignment • Less communication • Graceful degradation / Controlled shutdown • Less communication • Less computation • Scale free network • More robustness • Stigmergy • Energy balancing

7. DFG 1183 Organic Computing Active node Sink Clusterhead Role assignment • In Nature: • Concentration on specialized work • Data aggregation • Improvement by learning • Introducing two roles • Sensor nodes (Active nodes): • Measure data • Communicate with their clusterhead only • Clusterhead: • Distributes necessary data to his cluster (i.e. sensoring cycle) • Collects and aggregates data • Communicates outside cluster

8. DFG 1183 Organic Computing Max. Cellsize Active node Active node Sink Sensing range Redundant node Graceful degradation / Controlled shutdown (1) • In nature: Hibernation of animals • In sensor networks: Detection and temporary shutdown of redundant nodes • Detection: • Redundant, if transmitting and sensing function can be adopted by adjacent nodes • High effort for redundancy detection • Our approach: define a grid • Inside a cell, only one node is necessary for coverage

9. DFG 1183 Organic Computing Active node Sink Clusterhead Switched off node Graceful degradation / Controlled shutdown (2) Controlled shutdown • Nodes inside a cell establish a cluster • Clusterhead can shutdown all nodes in its cell until specified time

10. DFG 1183 Organic Computing Scale free network Random network • Network results from preferred connection • US airline system • Most nodes have alike number of connections • US highway system Scale free network (1)

11. DFG 1183 Organic Computing Scale free network (2) • Random network break down at random faults • Scale free network very robust against random faults • But prone to attack on main nodes

12. DFG 1183 Organic Computing Clusterhead Switched off node Active node Sink Scale free network (3) • Our approach: • starting with sink…. • after attending the network, node connects with all unconnected nodes in transmission range • Combination with graceful degradation

13. DFG 1183 Organic Computing g Sink Switched off node Clusterhead Sink Switched off node Switched off node Clusterhead (Sparsely populated Cluster) Clusterhead (Highly populated Cluster) Stigmergy • Behavior of nodes adapts to different environments • Clusterheads in highly populated clusters can be exchanged easily • Permitted to spend more energy • Permitted to connect with more adjacent nodes • New energy balanced scale free structure

14. DFG 1183 Organic Computing Current work (1) • Simulation of scale free routing strategies to analyze • Guaranteed connectivity • Behaviour of network with failed nodes • Balanced hop number • Matlab • Less programming effort • Advantageous visualization Changing connection rules Higher transmission range for densely populated cells

15. DFG 1183 Organic Computing Extracting Energy Current work (2) • Simulation of selected network strategies to analyze • Energy behaviour of nodes • Network lifetime • Balancing factors • NS2 • Energy model available • Realistic simulation

16. DFG 1183 Organic Computing Current work (3) • Lifetime extensionvia energy aware role changing • Assignment of roles: Clusterhead, Gateway, Aggregator, Sensor • Simulation of one routing path • Lifetime extension by 40%

17. DFG 1183 Organic Computing Current work (4) • Analysis of different cell shapes • Hexagonal, triangular • Enlargement of cells to include more nodes

18. DFG 1183 Organic Computing Future work • Robustness by altruism? • Adaption of changing environment parameters through learning at runtime? • Improved network behavior by more specialized roles?

19. DFG 1183 Organic Computing Conclusion • Generic OC principles adopted and optimized for sensor networks • New energy balanced and coverage aware OC routing strategy developed • Successfully implemented in Matlab simulation environment • Strategies should be compared in NS2 regarding network‘s robustness and lifetime • Publications Salzmann, J.; Kubisch, S.; Reichenbach, F.; Timmermann, D., Energy and Coverage Aware Routing Algorithm in Self Organized Sensor Networks, Fifth Annual IEEE International Conference on Pervasive Computing and Communications, New York, March 2007, (submitted) Kubisch, S.; Hecht, R.; Salomon, R.; Timmermann, D., Intrinsic Flexibility and Robustness in Adaptive Systems: A Conceptual Framework, 2006 IEEE Mountain Workshop on Adaptive and Learning Systems (SMCals/06), Logan, Utah, U.S.A., July 2006 Reichenbach, F.; Bobek, A.; Hagen, P.; Timmermann, D.; Increasing Lifetime of Wireless Sensor Networks with Energy-Aware Role-Changing, Proceedings of the 2nd IEEE International Workshop on Self-Managed Networks, Systems & Services (Self Man 2006), Dublin, Ireland, June 2006