Gugrajah_Yuvaan_ Ramesh_2003.pdf

Routing Protocols for Ad Hoc Networks Chapter 2
connected to one of the nodes in the dominating set. The second phase involves
another flooding process which connects the nodes of the dominating set and this
finally results in a single spine that runs through the network.
Once the spine has been formed, spine nodes gather topology information from
nodes that they dominate and the spine nodes transmit this link information to all
other nodes on the spine. Using this global knowledge of the topology, the spine
nodes determine the shortest paths for all node pairs. When a source node requires a
route to a destination, the source node requests a route from its dominator in the
spine. Route maintenance by the spine nodes are event-driven where the spine nodes
update routes when nodes move and time-driven with topology updates being
periodic.
Core-Extraction Distributed Ad Hoc Routing (CEDAR) algorithm [Siva99] was
introduced in an attempt to provide Quality of Service (QoS) routing in ad hoc
networks. CEI?AR is based on the original spine routing algorithm using MCDS but
bandwidth information is also included in the information stored at each dominator.
When a source seeks a destination with a required bandwidth, a core-path is first
established from the dominator node of the source to the dominator node of the
destination. The core-path is then used to provide the direction in which to iteratively
find a set of partial routes using only local information each of which satisfies the
bandwidth requirement. Together the partial routes are expected to form a single QoS
admissible route.
The main problem with the spine routing is that with node movement the structure of
the spine needs to change often. This means that it will be common for a new node to
be added to the spine or for a spine node to move into a position where it finds a
dominator and no longer needs to be a spine node. Changes in the spine structure
mean that the topological information needs to be updated on all nodes along the
spine. To overcome this problem, Partial Knowledge Spine Routing (PSR) [Siva98]
was introduced, which only allows spine nodes to maintain local information of the
nodes for which they are the dominator. Routing is then achieved by using on­
demand methods. However, the spine routing infrastructure may still be unable to
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