| Summary: | 碩士 === 雲林科技大學 === 電機工程系碩士班 === 98 === Wireless sensor network applications such as environmental monitoring and data
gathering are meant to operate as long as possible. Since each wireless node has
limited communication range, packets are generally delivered hop by hop, at the
expense of power consumption, towards the intended destinations. However, when any
intermediate node on a path has depleted its power, i.e., a hole emerges, packet
delivery fails and subsequently another new route must be resolved, so as to restore
packet transfer. Therefore, a well-planned routing strategy that avoids ineffective
transmissions on account of holes is essential to overall network performance.
This thesis presents a load-aware geographic routing scheme that allows for three
determinants for each of qualified neighbor nodes on demand: residual energy, the
amount of dissipated power for current transmission, and its distance away from the
destination. Each neighbor node is thus associated with a score per packet; the node
which scores highest becomes the next hop to forward the packet. Such a selection is
done hop by hop until the packet reaches its destination. Our strategy is to prevent
packets from traversing a certain set of nodes repeatedly, causing severe power drain
on these nodes. Accordingly, workload is better distributed in our architecture so that
holes are less likely to shape. In addition, we propose an algorithm, namely the
Available Relay Block algorithm, that is performed a priori to identify which areas
towards the given destination contain dead-end nodes. These identified areas are ruled
out of consideration by our load-aware strategy. By doing so, our routing strategy is
kept operable, despite the presence of holes, such that network lifetime can be
maximized. Performance evaluation is conducted via QualNet. Simulation results
indicate the effectiveness of our design and outlines several directions to work toward
in the future.
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