Overview:

Wireless sensor networks (WSNs) are typically characterized by a limited energy supply at sensor nodes. Hence, energy efficiency is an important issue in the system design and operation of WSNs. In this project, we propose a novel communication paradigm that enables energy-efficient information delivery in wireless sensor networks. Compared with traditional communication strategies, the proposed scheme explores a new dimension - time, to deliver information efficiently. We refer to the strategy as Communication through Silence (CtS). We identify a key drawback of CtS - energy - throughput trade-off, and explore optimization mechanisms that can alleviate the trade-off. We then investigate several challenges that need to be overcome, primarily at the medium access control layer of the network protocol stack, in order to realize CtS effectively.

Results / Status:

In our Mobicom paper, we have proposed three optimization strategies that significantly improves the throughput and energy performance of basic the CtS scheme. Those strategies are: multiplexing, cascading and fastfowarding. Following are the performance comparison between optimized CtS and conventional energy based transmission (EbT) in a multihop sensor network.

Figure 1

We also identified challenges that need to be addressed in order to realize the CtS strategy. Specific PHY layer solutions are necessary to exploit the potential of CtS. At MAC layer, special considerations for framing, addressing, sequencing, error control and contention resolution are also indispensible for an efficient realization of CtS.

Figure 2

Currently we are working on a MAC layer solution of CtS. We are also planning to implement CtS in our sensor testbed and measure the practical achievable energy savings of CtS strategies through experiments.

Publications & Presentations:

• Y. Zhu and R. Sivakumar,
  "Challenges: Communication through Silence in Wireless Sensor Networks,"
  ACM International Conference on Mobile Computing and Networking (MOBICOM), Cologne, Germany, August 2005.

Software Downloads:

People:

• Yujie Zhu (Student)
• Raghupathy Sivakumar (Professor)

References & Related Work:

• Z. Ghassemlooy E.D Kaluarachi and B. Wilson, "Digital pulse interval modulation for optical free space communication links", in IEE Colloq. On Optical Free Space Communication Links, Feb. 1996.
• R.G. Gallager, "Basic limits on protocol information in data communication networks", in IEEE Transaction on Information Theory, July 1976, pp. 385 398.