Energy-neutral scheduling and forwarding in environmentally-powered wireless sensor networks

  • Authors:
  • Alvin C. Valera;Wee-Seng Soh;Hwee-Pink Tan

  • Affiliations:
  • Sense and Sense-abilities Programme, Institute for Infocomm Research, Singapore 138632, Singapore and Department of Electrical and Computer Engineering, National University of Singapore, Singapore ...;Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore;Sense and Sense-abilities Programme, Institute for Infocomm Research, Singapore 138632, Singapore

  • Venue:
  • Ad Hoc Networks
  • Year:
  • 2013

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Abstract

In environmentally-powered wireless sensor networks (EPWSNs), low latency wakeup scheduling and packet forwarding is challenging due to dynamic duty cycling, posing time-varying sleep latencies and necessitating the use of dynamic wakeup schedules. We show that the variance of the intervals between receiving wakeup slots affects the expected sleep latency: when the variance of the intervals is low (high), the expected latency is low (high). We therefore propose a novel scheduling scheme that uses the bit-reversal permutation sequence (BRPS) - a finite integer sequence that positions receiving wakeup slots as evenly as possible to reduce the expected sleep latency. At the same time, the sequence serves as a compact representation of wakeup schedules thereby reducing storage and communication overhead. But while low latency wakeup schedule can reduce per-hop delay in ideal conditions, it does not necessarily lead to low latency end-to-end paths because wireless link quality also plays a significant role in the performance of packet forwarding. We therefore formulate expected transmission delay (ETD), a metric that simultaneously considers sleep latency and wireless link quality. We show that the metric is left-monotonic and left-isotonic, proving that its use in distributed algorithms such as the distributed Bellman-Ford yields consistent, loop-free and optimal paths. We perform extensive simulations using real-world energy harvesting traces to evaluate the performance of the scheduling and forwarding scheme.