wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

Ad Hoc Networks 7-3
FIGURE 7.2
Vehicular ad hoc networks.
rapid deployment of these systems at a lower cost, without having to lay cables to each sensor. To sum up,
ad hoc networks and alternative technologies are enabling direct intelligent communication between entities.
This new paradigm is poised to change the way we interact with the world and perform different tasks.
7.1.3 ad Hoc Network Characteristic
One of the key characteristics of ad hoc networks is mobility due to rapid repositioning of nodes. These
nodes can either move independently or are grouped together while their movement can be random
or along preplanned routes. These mobility models can have major impact on selecting an appropriate
routing scheme, which may influence the performance of the network. Another characteristic of ad hoc
networks is multihopping where the path from the source to destination includes several other intermediate
nodes. Wide-area ad hoc networks often exhibit multiple hops for obstacle negotiation, spectrum
reuse, and energy conservation. Besides, an ad hoc network must effectively handle problems pertaining
to addressing, routing, clustering, position identification, and power control, just to name a few.
Another important feature of the ad hoc networks is energy conservation. Designing energy-efficient
protocol is critical for prolonged operation since most ad hoc nodes have limited power. The ad hoc
networks can sometimes grow up to several thousand nodes, all moving in an unpredictable manner.
Although it may be possible to find an ad hoc solution for a few fast nodes or for a very large number
of static nodes, the problem arises when a large number of heterogeneous nodes move in random
direction with different speed over an unpredictable terrain. Thus, multihop, mobility, and large network
size combined with varying device characteristics (heterogeneity, bandwidth, and battery power
constraints) make the design of adequate routing protocol a major challenge. Besides, ad hoc network
should be able to prevent any attempt from intruders to eavesdrop and jam the channel. Due to open
P2P network architecture, the ad hoc networks are more vulnerable against malicious attacks than the
infrastructured counterparts. These attacks can be active or passive; either an attacker actively disrupts
network operations or simply monitors data, controls traffic patterns, and relays this information to
the enemy headquarters. The security for ad hoc networks, therefore, involves key establishment, trust
setup, secure routing, authentication, data aggression, etc., and is therefore a lot more challenging than
in conventional networks.
7.1.4 Enabling Technologies
IEEE 802.11 WLAN [802.11] is the most popular technology for ad hoc networks. There are various
working groups for the standards offering highest data rate up to 54.Mbps and enhancing
© 2011 by Taylor and Francis Group, LLC