ISSN : 1796-2056
Volume : 3    Issue : 1    Date : January 2008

ROAL: A Randomly Ordered Activation and Layering Protocol for Ensuring K-Coverage in
Wireless Sensor Networks
Hogil Kim, Eun Jung Kim, and Ki Hwan Yum
Page(s): 43-52
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In this paper, we propose a Randomly Ordered Activation and Layering (ROAL) protocol. Each node
under the ROAL protocol can decide its eligibility regarding a given coverage degree K at randomly
generated activation time using only the coverage status informed from its neighbor nodes located
within its sensing region. A new concept of layer coverage also provides a simple and effective
reconfiguration method for energy balancing. Using the layer concept, we also propose a circulation
scheme to reconfigure the set of working nodes in an autonomous way, where the reconfiguration
can be performed with a small and almost constant energy consumption. We also provide the
model of the expected coverage and connectivity for the layer coverage and show a proper range in
which only one node can be activated with regard to a node density and the sensing radius of a
The simulation results show that the ROAL protocol can guarantee K-coverage with more than 95%
coverage ratio, which almost closes to the coverage ratio that is achieved using the geographic
coordinate. A significantly extended network lifetime is also observed against the original topology of
a given network. Meanwhile, the experimental results on the circulation scheme show that the
fraction of total reconfiguration energy becomes less than 1% of the energy consumed for the
reconfiguration. Also, we obtain a greatly reduced packet latency, which corresponds to only 5% of
the delay that occurred in the ROAL protocol.

Index Terms
wireless sensor networks, K-coverage, layer coverage, circulation scheme