Finally, the use of alternate routes is inexpensive (for
multipath routing purposes) since it only implies adding another trajectory
[16]. All of these reasons make a very strong argument for the success of
trajectory-centric routing protocols.
Trajectory Based Forwarding [16] was originally proposed as a source routing
scheme. A continuous trajectory is determined by a source node and then
distributed as overhead in the forwarded packets. The continuous path is
parametrically defined, where the parameter corresponds to the sequential
forwarding of a packet. A continuous path described by a parametric equation
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Chapter 15 Information Forwarding and Tra?±c Engineering
is extended to a recursive form to implement multi-cast or multi-path routing.
Sequential hops along the route are determined according to several cost functions.
Every node analyzes the curve in its neighborhood. The neighborhood
of a node is defined by a circle of radius r0. The node will approximate the
curve as discrete points within its neighborhood and calculate the residuals
of the neighboring nodes. The residuals are defined as the parameter value
corresponding to the point which is closest to a node. Using these residuals as
a metric, the algorithm proposes several cost functions. These cost functions
vary and di?®er depending on application. For example, when the trajectory
is designed to avoid insecure transmission zones, a cost function which minimizes
the deviation from the curve would be optimal.
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