Page 133 - DCAP311_DCAP607_WIRELESS_NETWORKS

Unit 8: Wireless MAN

z z Security Risk: This has been another major issue with a data transfer over a wireless Notes
network. Basic network security mechanisms like the service set identifier (SSID) and
Wireless Equivalency Privacy (WEP). These measures may be adequate for residences and
small businesses but they are inadequate for entities that require stronger security.
z z Reachable Range: Normally wireless network offers a range of about 100 meters or less.
Range is a function of antenna design and power. Now a days the range of wireless is
extended to tens of miles so this should not be an issue any more.
WMAN (Wireless Metropolitan Area Networking) allows communication between two or more
terminals (nodes) using just one access point, within a radius up to 40 km. The most well-known
wireless networking technology is WiMAX (World Wide Interoperability for Microwave Access)`
created by WiMAX Forum which was founded by Esemble, Nokia, Harri and Cross Span in
2001. This wireless network is also known as IEEE 802.16 (Institute of Electrical and Electronics
Engineers), standard which defines the technology.
WiMAX works with radio wave for transmission and microwaves for reception in frequencies
between 2,3 and 3,5 GHz. This allows reaching speeds of 70 Mbps within distances up to 50 km
from the access point. Thus, a radial area of 100 Km could be cover with only one access point.
Thus, a radial area of 100 Km could be cover with only one access point.
The technology is commonly used to provide internet to rural areas in which installing other
types of technology becomes too expensive. Installed in the cities, WiMAX will allow people to
connect to the internet whenever they want without looking for ‘hotspots’. This will transform
the user internet mobile lifestyle.

The first WiMAX standard IEEE 802.16 , was created to administrate the interoperability of
all devices working between 10 and 66 GHz. It will allow, as WiFI does, receive and transmit
encrypted information among devices that have the technology. Within this standard, we should
make some remarks to the IEEE 802.16a, IEEE 802.16e-2005 and IEEE802.16m which will allow to
work with frequencies from 2 to 11 GHz, mobility and speed up to 1GB, respectively.

8.2 Components

The various components are as follows:

8.2.1 Bridges

A wireless bridge is a hardware component used to connect two or more network segments
(LANs or parts of a LAN) which are physically and logically (by protocol) separated. It does not
necessarily always need to be a hardware device, as some operating systems (such as Windows,
GNU/Linux, Mac OS X and FreeBSD) provide software to bridge different protocols. This is seen
commonly in protocols over wireless to cable. So in a sense the computer acts as a bridge by using
bridging OS software.
Many wireless routers and wireless access points offer either a “bridge” mode or a “repeater”
mode, both of which perform a similar common function, the difference being the bridge mode
connects two different protocol types and the repeater mode relays the same protocol type.
Wireless routers, access points, and bridges are available that are compliant with the IEEE802.11a,
b, g and n standards. The frequency bands for these wireless standards can be used license-free
in most countries.
Wireless bridge devices work in pairs (point-to-point), one on each side of the “bridge”. However,
there can be many simultaneous “bridges” using one central device (point to multipoint).
Bridging can be via WDS (Wireless Distribution System) which creates a transparent Level 2
wireless bridge between two or more points. Alternately the bridge can be set up as an access

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