1. Energy Aware Self Organized Communication in Complex Networks Jakob Salzmann, Dirk Timmermann SPP 1183 Third Colloquium Organic Computing, 14.-15.09.2006, Stuttgart Institute of Applied Microelectronics and Computer Engineering University of Rostock

2. DFG 1183 Organic Computing2 Outline Project introduction OC principles in research Current work Future work Conclusion

3. DFG 1183 Organic Computing3 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 Project introduction (1)

4. DFG 1183 Organic Computing4 Active node Sink Properties of a sensor network: –High node count –Random node distribution –Wireless communication Project introduction (2) Properties of a node: Typical problems: – Energy limits lifetime – Node failure rate high – Centralized control infeasible – Limited energy per node – Transmission range – Sensing range Transmission range ? Sensing range !

5. DFG 1183 Organic Computing5 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 Project introduction (3)

6. DFG 1183 Organic Computing6 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 Computing7 Role assignment Clusterhead: –Distributes necessary data to his cluster (i.e. sensoring cycle) –Collects and aggregates data –Communicates outside cluster Sensor nodes (Active nodes): –Measure data –Communicate with their clusterhead only Active node Sink Clusterhead In Nature: –Concentration on specialized work –Data aggregation –Improvement by learning Introducing two roles

8. DFG 1183 Organic Computing8 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 Inside a cell, only one node is necessary for coverage High effort for redundancy detection Our approach: define a grid Active node Sensing range Redundant node Max. Cellsize Active node Sink

9. DFG 1183 Organic Computing9 Controlled shutdown Nodes inside a cell establish a cluster Graceful degradation / Controlled shutdown (2) Clusterhead can shutdown all nodes in its cell until specified time Active node Sink Clusterhead Switched off node

10. DFG 1183 Organic Computing10 Scale free network (1) Network results from preferred connection US airline system Scale free network Most nodes have alike number of connections US highway system Random network

11. DFG 1183 Organic Computing11 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 Computing12 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 Clusterhead Switched off node

13. DFG 1183 Organic Computing13 Switched off node Clusterhead Switched off node Sink 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 g Sink Clusterhead (Sparsely populated Cluster) Clusterhead (Highly populated Cluster) Switched off node

14. DFG 1183 Organic Computing14 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 Computing15 Current work (2) Simulation of selected network strategies to analyze –Energy behaviour of nodes –Network lifetime –Balancing factors NS2  Energy model available  Realistic simulation Extracting Energy

16. DFG 1183 Organic Computing16 Current work (3) Lifetime extension via energy aware role changing –Simulation of one routing path –Assignment of roles: Clusterhead, Gateway, Aggregator, Sensor Lifetime extension by 40%

17. DFG 1183 Organic Computing17 Current work (4) Analysis of different cell shapes –Hexagonal, triangular Enlargement of cells to include more nodes

18. DFG 1183 Organic Computing18 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 Computing19 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 Conclusion 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 Publications