Gugrajah_Yuvaan_ Ramesh_2003.pdf

Routing Protocolsfor Ad Hoc Networks Chapter 2
Modifications have been made to the originally proposed routing protocols for ad
hoc networks to incorporate various enhancements such as using signal and location
stability of nodes as metrics for routing. Other enhancements include incorporation
of the Global Positioning System (GPS) to allow nodes to determine the location of
the other nodes in the network using both reactive and proactive mechanisms. The
use of virtual backbones has also been attempted to mimic the fixed infrastructure of
cellular networks. Hybrid protocols that use proactive routing locally and reactive
routing globally as well as clustering and zone-based protocols were also discussed.
Figure 2-12 depicts some of the unicast routing protocols proposed in the literature
for ad hoc networks. The concept of multicast routing is also briefly described.
Each routing protocol has its advantages and disadvantages. The implementation of
the enhancements to the basic routing protocols depends on a trade-off of cost vs.
performance. For example, the inclusion of a GPS unit would need to be justified,
depending on whether or not the GPS-based routing protocol would significantly
improve performance in the application under consideration. The zone-based,
hierarchical and clustering protocols have their'disadvantages in that while reducing
overhead for a majority of the nodes, certain nodes are overburdened and consume
more resources than other nodes in order to maintain and organize the network. It
therefore becomes difficult to justify the hierarchical and clustering structures when
different users are using devices all of the same type, especially where service costs
are involved, unless some type ofbilling system is implemented.
Most of the routing protocols proposed for ad hoc networks use the shortest path as
the main routing criterion. In Chapter 3 load balancing is discussed and extensions to
the reactive routing protocols are proposed for a routing protocol that uses routing
metrics which incorporate both signal quality determination and load balancing.
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