Multihop Medium Access Control for WSNs: An Energy Analysis Model
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Multihop Medium Access Control for WSNs: An Energy Analysis Model Jussi Haapola Centre for Wireless Communications (CWC), University of Oulu, P.O. Box 4500, 90014 Oulu, Finland Email: [email protected]
Zach Shelby Centre for Wireless Communications (CWC), University of Oulu, P.O. Box 4500, 90014 Oulu, Finland Email: [email protected]
´ Carlos Pomalaza-Raez Centre for Wireless Communications (CWC), University of Oulu, P.O. Box 4500, 90014 Oulu, Finland Email: [email protected]
¨ onen ¨ Petri Mah Institute of Wireless Networks, RWTH Aachen University, Kackertstraße 9, 52072 Aachen, Germany Email: [email protected] Received 30 November 2004; Revised 30 March 2005 We present an energy analysis technique applicable to medium access control (MAC) and multihop communications. Furthermore, the technique’s application gives insight on using multihop forwarding instead of single-hop communications. Using the technique, we perform an energy analysis of carrier-sense-multiple-access (CSMA-) based MAC protocols with sleeping schemes. Power constraints set by battery operation raise energy efficiency as the prime factor for wireless sensor networks. A detailed energy expenditure analysis of the physical, the link, and the network layers together can provide a basis for developing new energy-efficient wireless sensor networks. The presented technique provides a set of analytical tools for accomplishing this. With those tools, the energy impact of radio, MAC, and topology parameters on the network can be investigated. From the analysis, we extract key parameters of selected MAC protocols and show that some traditional mechanisms, such as binary exponential backoff, have inherent problems. Keywords and phrases: energy efficiency, wireless sensor networks, medium access control, multihop communications.
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INTRODUCTION
Sensor network applications have recently become of significant interest due to cheap single-chip transceivers and microcontrollers. Sensor nodes are usually battery operated and their operational lifetime should be maximized, hence energy consumption is a crucial issue. Many wireless sensors and therefore sensor networks are expected to operate using single-chip transceivers like the RFM TR1000 [1] or its European versions, all of which work in ISM bands. The radio parameters of the RFM TR1000 represent a typical transceiver operating in the lower-frequency ISM bands. Therefore, the This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
RFM TR1000 is used in this paper as a representative example. Regulations in many countries impose a duty cycle [2, 3], which is normally 10% in the 434 MHz band and 1% in the 868 MHz band. The duty cycle is defined as the ratio, expressed as a percentage, of the maximum transmitter on-time, relative to a one-hour period. When a sensor network is expected to work continuously, this duty cycle has to be taken into acc
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