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Mobile Electronic Commerce by June Wei

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78 Mobile Electronic Commerce
4.1.3 Types of network
4.1.3.1 Wired network
Wired network is simply a collection of two or more computers, printers,
and other devices linked by Ethernet cables. Wired networks can also be
used as part of other wired and wireless networks. Ethernet is the fast-
est wired network protocol, with connection speeds from 10 megabits per
second (Mbps) to 100Mbps or higher. Typically, the range of a wired net-
work is within a radius of 2000 ft.
4.1.3.2 Wireless network
Wireless network, which uses high-frequency radio waves rather than
wires to communicate between nodes, is another option for home or
business networking. Individuals and organizations can use this option
to expand their existing wired network or to go completely wireless.
Wireless allows for devices to be shared without networking cable, which
increases mobility but decreases range. There are two main types of wire-
less networking: peer to peer or ad hoc and infrastructure.
4.1.3.3 Ad hoc wireless network
Ad hoc or peer-to-peer wireless network consists of a number of computers
each equipped with a wireless networking interface card. Each computer
can communicate directly with all the other wireless-enabled computers.
They can share les and printers this way but may not be able to access
wired LAN resources unless one of the computers acts as a bridge to
thewired LAN using special software. Mobile ad hoc networks (MANETs)
are a kind of ad hoc wireless network that usually has a routable network-
ing environment on top of a Link Layer ad hoc network (Hu et al., 2003).
Node 1
Node 2
Node 3
Node 4
Figure 4.8 Mesh topology.
79Chapter four: Security of wireless ad hoc network
4.1.4 Comparing wireless network and wired network
The key advantage of wireless networks over wired network emerges
from the major difference between the two; that is, one uses network
cables and the other uses radio frequencies (see Figure 4.9).
Though wireless networking is a lot more mobile than wired net-
working, the range of the network is usually 150–300 indoors and up
to 1000 ft outdoors depending on the terrain, but wired network is
much more secure than wireless network, and transmission speeds
can suffer from outside interference.
Wired networks are inexpensive compared with wireless network
installation, for wireless adapters and access points may cost three
or four times as much as Ethernet cable adapters and hubs/switches.
Broadband routers cost more, but these are optional components of a
wired network, and their higher cost is offset by the benet of easier
installation and built-in security features.
Wired LANs offer superior performance compared with wire-
less networks as it degrades because of distance sensitivity; that is,
maximum performance will degrade on computers farther away from
the access point or other. A traditional wired Ethernet connection
offers only 10Mbps bandwidth, but 100Mbps Fast Ethernet technol-
ogy costs a little more and is readily available. Fast Ethernet should
be sufcient for le sharing, gaming, and high-speed Internet access.
But greater mobility of wireless LANs helps offset the performance
disadvantage.
Wireless LANs are less secure than wired LANs because wireless
communication signals travel through the air and can easily be
intercepted. But wireless networks can be made as secure as wired
networks are for the ease of mobility; that is, wireless networks
protect their data through the wired equivalent privacy (WEP)
encryption.
Radio wave and microwave
30
04
00 900
GHzKHz
3
THz THz
Infrared
Light wave
Figure 4.9 Radio frequency distribution.

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