Mobile Electronic Commerce

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.