Wireless sensor nodes spend most of the time waiting either for sensed data or for packets to be routed to the sink. While on board, sensors can raise hardware interrupts to trigger the wake-up of the processor, incoming packets require the radio module to be turned on in order to be properly received and processed; thus, reducing the effectiveness of dynamic power management and exposing the node to unintended packets cause energy waste. The capability of triggering the wake-up of a node over the air would makes it possible to keep the entire network asleep and to wake up the nodes along a path to the sink whenever there is a packet to transmit. This paper presents an ultrasonic wake-up trigger for ultra-low-power wireless sensor nodes developed as a plug-in module for VirtualSense motes. The module supports a simple out-of-band addressing scheme to enable the selective wake-up of a target node. In addition, it makes it possible to exploit the propagation speed of ultrasonic signals to perform distance measurements. The paper outlines the design choices, reports the results of extensive measurements, and discusses the additional degrees of freedom introduced by ultrasonic triggering in the power-state diagram of VirtualSense. 1. Introduction The reduction of power consumption through the adoption of low-power design solutions and dynamic power management policies is mandatory in order to meet the needs of wireless sensor networks (WSNs). The average power consumption of on-board transceivers, at the time of writing, can be estimated to be around 20？mA (either in receiver or transmitter mode), which is commonly recognized as the main contribution to the energy drain of sensor nodes [1]. Since the radio module has to be powered on to enable the reception of incoming packets, strategies and techniques have been developed with the aim of limiting the impact of idle listening on power consumption. Current state-of-the-art solutions make use of pseudoasynchronous rendez-vous schemes or purely asynchronous methods that exploit ad hoc hardware. The former, in all their variants, are protocols developed in order to allow efficient communication between duty-cycle-based receivers, which typically trade off latency for power consumption. The latter are techniques that exploit separate low-power wake-up receivers that are devoted to continuous monitoring of the communication channel in order to enable the main radio module to be switched off while idle to avoid energy waste. A further possible approach to the problem entails the adoption of global clock
References
[1]
V. Jelicic, M. Magno, D. Brunelli, V. Bilas, and L. Benini, “Analytic comparison of wake-up receivers for WSNs and benefits over the wake-on radio scheme,” in Proceedings of the 7th ACM Workshop on Performance Monitoring and Measurement of Heterogeneous Wireless and Wired Networks (PM2HW2N '12), pp. 99–106, ACM, New York, NY, USA, 2012.
[2]
E. Y. A. Lin, J. M. Rabaey, and A. Wolisz, “Power-efficient Rendez-vous schemes for dense wireless sensor networks,” in Proceedings of IEEE International Conference on Communications, pp. 3769–3776, June 2004.
[3]
J. Gao and L. Guibas, “Geometric algorithms for sensor networks,” Philosophical Transactions of the Royal Society A, vol. 370, no. 1958, pp. 27–51, 2012.
[4]
G. Lu, D. De, M. Xu, et al., “TelosW: enabling ultra-low power wake-on sensor network,” in Proceedings of the 7th International Conference on Networked Sensing Systems (INSS '10), pp. 211–218, June 2010.
[5]
V. Jeli？i？, M. Magno, D. Brunelli, V. Bilas, and L. Benini, “An energy efficient multimodal wireless video sensor network with eZ430-RF2500 modules,” in Proceedings of the 5th International Conference on Pervasive Computing and Applications (ICPCA '10), pp. 161–166, December 2010.
[6]
P. Le-Huy and S. Roy, “Low-power 2.4？GHz wake-up radio for wireless sensor networks,” in Proceedings of the 4th IEEE International Conference on Wireless and Mobile Computing, Networking and Communication ( WIMOB '08), pp. 13–18, IEEE Computer Society, Washington, DC, USA, October 2008.
[7]
R. van Langevelde, M. van Elzakker, D. van Goor, H. A. H. Termeer, J. Moss, and A. J. Davie, “An ultra-low-power 868/915？MHz RF transceiver for wireless sensor network applications,” in Proceedings of IEEE Radio Frequency Integrated Circuits Symposium (RFIC '09), pp. 113–116, June 2009.
[8]
M. S. Durante and S. Mahlknecht, “An ultra low power wakeup receiver for wireless sensor nodes,” in Proceedings of the 3rd International Conference on Sensor Technologies and Applications (SENSORCOMM '09), pp. 167–170, IEEE Computer Society, Washington, DC, USA, June 2009.
[9]
N. M. Pletcher, J. Rabaey, and S. Gambini, “A 52 μW wake-up receiver with ？72 dBm sensitivity using an uncertain-IF architecture,” IEEE Journal of Solid-State Circuits, vol. 44, no. 1, pp. 269–280, 2009.
[10]
S. Drago, D. M. W. Leenaerts, F. Sebastiano, L. J. Breems, K. A. A. Makinwa, and B. Nauta, “A 2.4？GHz 830pJ/bit duty-cycled wake-up receiver with -82dBm sensitivity for crystal-less wireless sensor nodes,” in Proceedings of IEEE International Solid-State Circuits Conference (ISSCC '10), pp. 224–225, February 2010.
[11]
G. U. Gamm, M. Sippel, M. Kostic, and L. M. Reindl, “Low power wake-up receiver for wireless sensor nodes,” in Proceedings of the 6th International Conference on Intelligent Sensors, Sensor Networks and Information Processing (ISSNIP '10), pp. 121–126, December 2010.
[12]
X. Huang, S. Rampu, X. Wang, G. Dolmans, and H. de Groot, “A 2.4GHz/915MHz 51μW wake-up receiver with offset and noise suppression,” in Proceedings of IEEE International Solid-State Circuits Conference (ISSCC '10), pp. 222–223, 2010.
[13]
X. Huang, P. Harpe, G. Dolmans, et al., “A 915？MHz ultra-low power wake-up receiver with scalable performance and power consumption,” in Proceedings of the 37th European Solid-State Circuits Conference (ESSCIRC '11), pp. 543–546, September 2011.
[14]
W. C. Shih, R. Jurdak, B. H. Lee, and D. Abbott, “High sensitivity wake-up radio using spreading codes: design, evaluation, and applications,” EURASIP Journal on Wireless Communications and Networking, vol. 2011, article 26, 2011.
[15]
S. J. Marinkovic and E. M. Popovici, “Nano-power wireless wake-up receiver with serial peripheral interface,” IEEE Journal on Selected Areas in Communications, vol. 29, no. 8, pp. 1641–1647, 2011.
[16]
C. Hambeck, S. Mahlknecht, and T. Herndl, “A 2.4μW wake-up receiver for wireless sensor nodes with 71dBm sensitivity,” in Proceedings of IEEE International Symposium of Circuits and Systems (ISCAS '11), pp. 534–537, May 2011.
[17]
N. B. Priyantha, A. Chakraborty, and H. Balakrishnan, “The cricket location-support system,” in Proceedings of the 6th Annual International Conference on Mobile Computing and Networking (MobiCom '00), pp. 32–43, August 2000.
[18]
G. Oberholzer, P. Sommer, and R. Wattenhofer, “SpiderBat: augmenting wireless sensor networks with distance and angle information,” in Proceedings of the 10th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN '11), pp. 211–222, April 2011.
[19]
K. Yadav, I. Kymissis, and P. Kinget, “A 4.4-μW wake-up receiver using ultrasound data,” IEEE Journal of Solid-State Circuits, vol. 48, no. 3, pp. 649–660, 2013.
E. Lattanzi and A. Bogliolo, “Virtual sense: a java-based open platform for ultra-low-power wireless sensor nodes,” International Journal of Distributed Sensor Networks, vol. 2012, Article ID 154737, 11 pages, 2012.
A. Dunkels, B. Gr？nvall, and T. Voigt, “Contiki—a lightweight and flexible operating system for tiny networked sensors,” in Proceedings of the 29th Annual IEEE International Conference on Local Computer Networks (LCN '04), pp. 455–462, IEEE Computer Society, Washington, DC, USA, November 2004.
