Ultra-low duty cycle MAC with scheduled channel polling
Proceedings of the 4th international conference on Embedded networked sensor systems
SIGMETRICS '08 Proceedings of the 2008 ACM SIGMETRICS international conference on Measurement and modeling of computer systems
A tale of two synchronizing clocks
Proceedings of the 7th ACM Conference on Embedded Networked Sensor Systems
SewerSnort: a drifting sensor for in-situ sewer gas monitoring
SECON'09 Proceedings of the 6th Annual IEEE communications society conference on Sensor, Mesh and Ad Hoc Communications and Networks
The true cost of accurate time
HotPower'08 Proceedings of the 2008 conference on Power aware computing and systems
Angle-of-arrival-assisted relative interferometric localization using software defined radios
MILCOM'09 Proceedings of the 28th IEEE conference on Military communications
Putting the software radio on a low-calorie diet
Hotnets-IX Proceedings of the 9th ACM SIGCOMM Workshop on Hot Topics in Networks
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Time keeping and synchronization are important services for networked and embedded systems. High quality timing information allows embedded network nodes to provide accurate time-stamping, fast localization, efficient duty cycling schedules, and other basic but essential functions - all of which are required for low power operation. In this paper we present a new type of local clock source called Crystal Compensated Crystal based Timer (XCXT) and a number of novel algorithms that effectively utilize it to achieve low power consumption in wireless sensor networks. The XCXT has timing accuracies similar to timers based on temperature compensated crystal oscillators (TCXO) but has a lower implementation cost and requires less power. Our initial 8MHz prototype unit, using the simplest algorithm, achieves an effective frequency stability of ±1.2ppm and consumes only 1.27mW. On the other hand, commercially available TCXOs with similar stability can cost over 10 times as much and consume over 20mW. In addition to the prototype, we will present algorithms that will improve the XCXT's power consumption by at least 48%, depending on application and environmental conditions. We will also show how XCXT's power efficiency can be improved even further by employing clocks at different frequency when different time granularities are required by an application.