3.3 Location-Centric: Geographical Routing
A problem with using IP based routing in sensor networks comes from the
fact that the nodes are randomly distributed over a region. The IP address
assigned to a specific node is constant and has no relation to its actual physical
location. When a node moves or dies its IP address loses significance since it
does not o?®er any help in actually finding the node. To address this issue, the
concept of geographical routing, where each node can dynamically determine
its location, was developed. The problem of finding a node??™s position relative to
the other nodes is called localization. Each node can be equipped with a GPS
capable of supplying the node with its longitude and latitude. Transmitting to
the node which is in the same direction as the destination will be a great start
to any routing protocol in which the nodes are aware of their position. The
geographic coordinates of the nodes is not always available or desirable. In the
case where GPS is not available, localization can be very costly in terms of
power, sometimes more than the actual routing. Although it has been shown
in [9] that routing protocols that do not use geographical location information
are not scalable (e.g., traditional ad hoc protocols such as DSR and AODV),
the number of proposed energy-aware location based protocols is still quite
small.
Greedy Perimeter Stateless Routing (GPSR) [8] is a classical geographic
routing protocol.
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