Performance Evaluation and Comparison of Protocols for Topology Control over IEEE 802.15.4 - 10/14/2005

Huseyin Mutlu

Recent developments in microelectronics and wireless communication technology opened a new era for wireless sensor networks (WSNs). Reasonable computing power, data storage and radio transceivers can coexist today in a small volume and at low cost. However, similar reduction in size and improvements in capacity did not occur for the batteries that power these devices. Power consumption remains the biggest problem for WSNs. Researchers addressed this issue by developing low power communication devices, standards and topology control algorithms that use available energy as efficiently as possible. This thesis concerns topology control in WSNs. In particularly, we implement and compare the performances of two topology control protocols over an emerging standard for WSNs: IEEE 802.15.4 (also known as "ZigBee"). The feature of this technology that enables power conservation concerns the possibility to send the nodes "to sleep," i.e., to turn off their radio interface. By defining suitable "awake/asleep" schedules, nodes are able to save energy while still providing enough connectivity to allow efficient network operations. The topology control protocols we consider are GAF and S-DMAC, two recently proposed scheduling algorithms. This work investigates the feasibility of implementing GAF and S-DMAC over the different modes of IEEE 802.15.4. Both solutions are implemented in the network simulator ns-2 for which we have provided necessary extensions that implements the IEEE 802.15.4 protocol stack and the GAF and S-DMAC procedures. Our results show that in general, a density independent solution like S-DMAC outperforms GAF in essentially all the metrics we considered.