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This paper presents a self-organizing MAC protocol framework for distributed sensor networks with arbitrary meshtopologies. The novelty of the proposed ISOMAC (In-band Self-Organized MAC) protocol lies in its in-band control mechanismfor exchanging TDMA slot information while distributed MAC scheduling. A fixed length bitmap vector is used in each packetheader for exchanging relative slot timing information across immediate and up to 2-hop neighbors. It is shown that by avoidingexplicit timing information exchange, ISOMAC can work without network-wide time synchronization which can be prohibitivefor severely cost-constrained sensor nodes in very large networks. A slot-clustering effect, caused by in-band bitmap constraints,enables ISOMAC to offer better spatial channel reuse compared to traditional distributed TDMA protocols. ISOMAC employs apartial node wake-up and header-only transmission strategy to adjust energy expenditure based on the instantaneous nodal datarate. Both analytical and simulation models have been developed for characterizing the proposed protocol. Results demonstratethat with in-band bitmap vectors of moderate length, ISOMAC converges reasonably quickly - approximately within 4 to 8TDMA frame duration. Also, if the bitmap header duration is restricted within 10% of packet duration, the energy penalty of thein-band information is quite negligible. It is also shown that ISOMAC can be implemented in the presence of network timesynchronization, although its performance without synchronization is just marginally worse than that with synchronization.
Wireless Sensor Network; Medium Access Control, MAC, Distributed TDMA, In-band Protocols, Sensor Energy Efficiency, Network Self-Organization

F. Yu, S. Biswas and T. Wu, "Toward In-Band Self-Organization in Energy-Efficient MAC Protocols for Sensor Networks," in IEEE Transactions on Mobile Computing, vol. 7, no. , pp. 156-170, 2007.
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