Topology management is essential for prolonging the lifetime of a sensor network. In [1,2], we presented the HEED (Hybrid, Energy-Efficient, Distributed) clustering algorithm for sensor networks. In HEED, a node autonomously and probabilistically elects to become a cluster head based on its residual energy and its communication cost in its neighborhood. HEED clusters the network in a constant number of iterations, elects cluster heads that are well-distributed in the network, and incurs low message and communication overhead.
HEED is implemented in nesC for TinyOS, and evaluated on Mica2 and Mica2Dot sensor motes. Its code extends the Multihop routing module in TinyOS to cluster the network prior to building the routing tree. In addition, the Surge application, which collects sensors readings at the base station, is modified such that data is aggregated along the routing tree as it is forwarded. The energy consumption is computed using a credit-point system in which a node starts with an initial number of points which are reduced as the node transmits packets, receives packets, senses the environment, and processes data. The clustered multi-hop routing and data aggregation application is referred to as iHEED, and its evaluation on Mica2 and Mica2Dot motes is given in .
iHEED code for TinyOS: Click [Here]
 Ossama Younis and Sonia Fahmy, "Distributed Clustering in Ad-hoc Sensor Networks: A Hybrid, Energy-Efficient Approach," In Proceedings of IEEE INFOCOM, volume 1, pp. 629-640, March 2004. [PDF] [Postscript] [Presentation slides in Powerpoint]
 Ossama Younis and Sonia Fahmy, "HEED: A Hybrid, Energy-Efficient, Distributed Clustering Approach for Ad-hoc Sensor Networks," IEEE Transactions on Mobile Computing, volume 3, issue 4, pp. 366-379, Oct-Dec 2004. [PDF] [Postscript]
 Ossama Younis and Sonia Fahmy, "An Experimental Study of Routing and Data Aggregation in Sensor Networks," In Proceedings of the International Workshop on Localized Communication and Topology Protocols for Ad hoc Networks (LOCAN), held in conjunction with The 2nd IEEE International Conference on Mobile Ad Hoc and Sensor Systems (MASS-2005), November 2005. [PDF] [Postscript]
 Ossama Younis, Sonia Fahmy, and Paolo Santi, "Robust Communications for Sensor Networks in Hostile Environments," In Proceedings of the 12th IEEE International Workshop on Quality of Service (IWQoS), pp. 10-19, June 2004. [PDF] [Postscript] [Presentation slides in Powerpoint]
 Ossama Younis and Sonia Fahmy, "A Framework for Distributed Time Synchronization in Multi-hop Sensor Networks," In Proceedings of the Second IEEE International Conference on Sensor and Ad Hoc Communications and Networks (SECON), September 2005. [PDF] [Postscript]
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