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Unformatted text preview: Radio-Triggered Wake-Up for Wireless Sensor Networks Lin Gu and John A. Stankovic Department of Computer Science, University of Virginia lingu, stankovic @cs.virginia.edu Abstract Power management is an important technique to prolong the lifespan of sensor networks. Many power management protocols employ wake-up/sleep schedules, which are often complicated and inefficient. We present power management schemes that eliminate such wake-up periods unless the node indeed needs to wake up. This type of wake-up capability is enabled by a new radio-triggered hardware component inspired by the observation that the wake-up radio signal contains enough energy to trigger a wake-up process. We evaluate the potential power saving in terms of the lifes- pan of a sensor network application, using experiment data and SPICE circuit simulations. Comparing the result with always-on and rotation-based power management schemes, we find the radio-triggered scheme saves 98% of the energy used in the always-on scheme, and saves over 70% of the en- ergy used in the rotation-based scheme. Consequently, the lifespan increases from 3.3 days (always-on) or 49.5 days (rotation-based) to 178 days (radio-triggered). Furthermore, a store-energy technique can extend operating distance from 10 feet to 22 feet, or even longer if longer latency is accept- able. Wake-up efficiency is evaluated in NS-2 simulations, which show that radio-triggered wake-up has fewer failures, shorter latency, and consistently larger sensing laxity than rotation based wake-up. We also present amplification and radio-triggered IDs which can further enhance performance. 1. Introduction A sensor network is comprised of a number of low-power devices with sensing and computing capability. In many sen- sor network systems, the power supply for the network nodes is usually a depletable power source, such as batteries. To in- crease the lifespan of sensor networks, researchers have de- signed a number of power management schemes. Many power management schemes take advantage of the energy saving features of sensor network hardware. For ex- ample, the ATmega128 processor, which is designed for em- bedded systems and is used in the Berkeley Mica2 mote, has six working modes with different energy saving features  . In one of the working modes, the processor shuts down all the hardware components except for the memory, a timer, and the interrupt handler, hence energy consumption reduces to less than of the active working mode. Power management schemes need to control when a net- work node should enter a high-power running mode and when to enter a low-power sleep mode. The high-power to low-power transition can usually be done with a set of in- structions that shuts down hardware components, and the power management scheme may perform this action when certain conditions hold, e.g., there are no events in the sys- tem for a long time. The low-power to high-power transi- tion is, however, a tricky problem because the network node...
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This note was uploaded on 01/27/2010 for the course EE 600 taught by Professor Aodafkdlja during the Spring '10 term at Aarhus Universitet.
- Spring '10