14-05-2012, 01:31 PM
An Overview of Mobile Ad Hoc Networks: Applications and Challenges
MANET-Challenges.pdf (Size: 347.93 KB / Downloads: 48)
Introduction
The field of wireless and mobile communications
has experienced an unprecedented
growth during the past decade. Current
second-generation (2G) cellular systems
have reached a high penetration rate,
enabling worldwide mobile connectivity.
Mobile users can use their cellular phone to
check their email and browse the Internet.
Recently, an increasing number of wireless
local area network (LAN) hot spots is
emerging, allowing travellers with portable
computers to surf the Internet from airports,
railways, hotels and other public locations.
Broadband Internet access is driving
wireless LAN solutions in the home for
sharing access between computers. In the
meantime, 2G cellular networks are evolving
to 3G, offering higher data rates,
infotainment and location-based or personalised
services.
Technological Challenges
As already stated, the specific characteristics
of MANETs impose many challenges to
network protocol designs on all layers of the
protocol stack5. The physical layer must deal
with rapid changes in link characteristics.
The media access control (MAC) layer needs
to allow fair channel access, minimise packet
collisions and deal with hidden and exposed
terminals. At the network layer, nodes need
to cooperate to calculate paths. The transport
layer must be capable of handling packet loss
and delay characteristics that are very
different from wired networks.
Addressing and Internet connectivity
In order to enable communication between
nodes within the ad hoc network, each node
needs an address. In stand-alone ad hoc
networks, the use of IP addresses is not per
se obligatory, as unique MAC addresses
could be used to address nodes. However,
all current applications are based on TCP/IP
or UDP/IP.
Security and node cooperation
The wireless mobile ad hoc nature of
MANETs brings new security challenges to
the network design13. As the wireless
medium is vulnerable to eavesdropping and
ad hoc network functionality is established
through node cooperation, mobile ad hoc
networks are intrinsically exposed to
numerous security attacks. During passive
attacks, an attacker just listens to the
channel in order to discover valuable
information. This type of attack is usually
impossible to detect, as it does not produce
any new traffic in the network.