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J. Sens. Actuator Netw. 2013, 2(3), 424-448; doi:10.3390/jsan2030424
Article

Energy-Efficient Packet Relaying in Wireless Image Sensor Networks Exploiting the Sensing Relevancies of Source Nodes and DWT Coding

1,* , 2
, 3
 and 4
1 DTEC-UEFS, State University of Feira de Santana, Feira de Santana, 44036-900, Brazil 2 DCA-CT-UFRN, Federal University of Rio Grande do Norte, Natal, 59072-970, Brazil 3 IDMEC-FEUP-UP, University of Porto, Porto, 4200-465, Portugal 4 INESC TEC-FEUP-UP, University of Porto, Porto, 4200-465, Portugal
* Author to whom correspondence should be addressed.
Received: 24 May 2013 / Revised: 19 June 2013 / Accepted: 26 June 2013 / Published: 10 July 2013
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Abstract

When camera-enabled sensors are deployed for visual monitoring, a new set of innovative applications is allowed, enriching the use of wireless sensor network technologies. In these networks, energy-efficiency is a highly desired optimization issue, mainly because transmission of images and video streams over resource-constrained sensor networks is more stringent than transmission of conventional scalar data. Due to the nature of visual monitoring, that follows a directional sensing model, camera-enabled sensors may have different relevancies for the application, according to the desired monitoring tasks and the current sensors’ poses and fields of view. Exploiting this concept, each data packet may be associated with a priority level related to the packet’s origins, which may be in turn mapped to an energy threshold level. In such way, we propose an energy-efficient relaying mechanism where data packets are only forwarded to the next hop if the associated energy threshold level is below the current energy level of the relaying node. Thus, packets from low-relevant source nodes will be silently dropped when the current energy level of intermediate nodes run below the pre-defined thresholds. Doing so, energy is saved potentially prolonging the network lifetime. Besides the sensing relevancies of source nodes, the relevance of DWT subbands for reconstruction of original images is also considered. This allows the creation of a second level of packet prioritization, assuring a minimal level of image quality even for the least relevant source nodes. We performed simulations for the proposed relaying mechanism, assessing the expected performance over a traditional relaying paradigm.
Keywords: energy-efficient packet relaying; sensing relevance; DWT coding; wireless image sensor networks energy-efficient packet relaying; sensing relevance; DWT coding; wireless image sensor networks
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Costa, D.G.; Guedes, L.A.; Vasques, F.; Portugal, P. Energy-Efficient Packet Relaying in Wireless Image Sensor Networks Exploiting the Sensing Relevancies of Source Nodes and DWT Coding. J. Sens. Actuator Netw. 2013, 2, 424-448.

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