Wireless sensor nets demand trade-off

Wireless sensor nets demand trade-off -...

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http://www.wirelessnetdesignline.com/showArticle.jhtml;jsessionid=MLCYHQDGBQF Wireless sensor nets demand trade-offs By Sokwoo Rhee and Sheng Liu Courtesy of EE Times (10/31/2003 11:21 AM EST) Wireless sensor networks represent an emerging technology that has great potential for widespread applications. These networks consist of a large number of simple nodes with limited power sources and functionality, but they offer far greater utility than the sum of those individual nodes. To maintain highly dynamic, ad-hoc networks with resource- constrained nodes, however, trade-offs among power consumption, robustness and responsiveness must be made. The most common way to reduce the power consumption of sensor network nodes is to minimize the time spent in transmitting, listening and processing. But low-duty-cycle operation inevitably leads to slow network response, and eventually may result in network congestion or even instability. This article will analyze the design trade-offs between node duty cycle and system-level performance, pinpointing opportunities to improve power efficiency while maintaining network robustness and responsiveness. Many factors influence the power consumption of wireless communication devices. In a sensor network node, the radio consumes more power than other components in the node. A narrowband radio with 0-dBm output typically draws about 15 milliamps in transmit (TX) mode at 3 volts dc and 5 to 15 mA in receive (RX) mode. Spread-spectrum radios tend to draw more current in RX than in TX. Such current consumption is excessive to a sensor node supported only by a coin cell battery with no more than 220 mA-hr of capacity. To save battery power, the radio must be turned off as much as possible. But in an ad-hoc, multihop wireless sensor network, sensor nodes cooperate to maintain connectivity and forward traffic on behalf of one another, so turning off the radio for an extended period would certainly increase the likelihood of a node's missing and dropping packets, resulting in numerous
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This note was uploaded on 05/06/2008 for the course CMPE 206 taught by Professor Rfatoohi during the Summer '07 term at San Jose State University .

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Wireless sensor nets demand trade-off -...

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