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Security in Wireless Ad Hoc Networks 447
nodes forming the ad hoc networks themselves have to act as routers. A MANET may
therefore be defined as an autonomous system of mobile routers (and associated hosts)
connected by wireless links—the union of which forms an arbitrary graph. Given the
central importance of routing in ad hoc networks, it is not surprising that routing forms
a basis for classifying ad hoc networks into two groups: single-hop ad hoc networks
and multihop ad hoc networks. Single-hop ad hoc networks are ad hoc networks where
nodes do not act as routers and therefore communication is possible only between nodes
which are within each other’s radio frequency (RF) range. On the other hand, multihop ad
hoc networks are ad hoc networks where nodes are willing to act as routers and route or
forward the traffic of other nodes.
If you look at the basis for two classifications closely that—is, the geographical
coverage and the routing capability of nodes—the two classifications are not completely
orthogonal. Ad hoc PANs are more likely to be single hop ad hoc networks since nodes
would be close enough to be within each other’s RF range. On the other hand, ad hoc
LANs and ad hoc WANs are more likely to require nodes to have routing capability and
therefore form multihop networks.
Multihop ad hoc networks and their security is an active area of research as of the writing
of this chapter. In the next section we look at some of the emerging security concepts
(and areas of active research) in multihop ad hoc networks. Single-hop ad hoc networks
are now being used commercially and one of the most popular single-hop ad hoc wireless
standard is Bluetooth. We look more closely at Bluetooth and how it implements security
in the next section.
19.2 Bluetooth
One of the most popular ad hoc standards today is Bluetooth. Some of the salient features
of Bluetooth are as follows:
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Wireless ad hoc networking technology.
Operates in the unlicensed 2.4 GHz frequency range.
Geographical coverage limited to personal area networks (PAN).
Point-to-point and point-to-multipoint links.
Supports synchronous and asynchronous traffic.
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