Page 63 - M. Abrahim Thesis

Computer Network 2021

3.4 Wireless Networking

When the computer was first introduced to the world, it was affordable by only large
corporations, governments, and universities. From the first building-sized devices with minimal
computing power to those that fit in the palm of a person’s hand, huge leaps in technology have
occurred. The same is true on the connectivity side of the industry. The advantages are speed,
reliability, and to a certain extent convenience. Physical connectivity allows an increase in
productivity by allowing the sharing of printers, servers, and software. However, networked
systems require that the workstation remain stationary, permitting moves only within the limits
of the media and office area. The introduction of wireless technology removes these restraints
and brings true portability to the computing world. While the current state of wireless
technology does not provide the high-speed transfers of cabled networks nor the security and
uptime reliability, the flexibility justifies the trade-off. When considering the installation of a
network in an existing facility, wireless is at the top of many an administrator’s lists of options.
A simple wireless network can be up and running in just a few minutes after the workstations
are turned on. Connectivity to the Internet is provided through a wired connection, router, cable
modem, or Digital Subscriber Line (DSL) modem, and a wireless access point that acts as a hub
for the wireless nodes. In a residential or small office environment these devices might be
combined into a single unit.

https://www.youtube.com/watch?v=Uz-RTurph3c

3.5 Wireless LAN Organization and Standards

An understanding of the regulations and standards that apply to wireless technology
ensures that deployed networks are interoperable and in compliance. Just as in cabled networks,
IEEE is the prime issuer of standards for wireless networks. The standards have been created
within the framework of the regulations set forth by the FCC. A key technology contained within
the IEEE 802.11 standard is DSSS. DSSS applies to wireless devices operating within a 1 to 2 Mbps
range. A DSSS system can operate at up to 11 Mbps but is not considered compliant above 2
Mbps. The next standard approved was IEEE 802.11b, which increased transmission capabilities
to 11 Mbps. Even though DSSS WLANs are able to interoperate with the FHSS WLANs, problems
developed prompting design changes by the manufacturers. In this case,
IEEE’s task was simply to create a standard that matched the manufacturer’s solution. IEEE
802.11b, called Wi-Fi or high-speed wireless, refers to DSSS systems that operate at 1, 2, 5.5,
and 11 Mbps. All 802.11b systems are backward-compliant in that they also support 802.11 for
1- and 2-Mbps data rates for DSSS only. This backward compatibility is extremely important
because it allows upgrading of the wireless network without replacing the network interface
cards (NICs) or access points. IEEE 802.11b devices achieve the higher data throughput rate by
using a different coding technique from 802.11, allowing for a greater amount of data to be
transferred in the same time frame. The majority of 802.11b devices still fail to match the 10
Mbps throughput of wired Ethernet and generally function in the 2–4 Mbps range. 802.11a
covers WLAN devices operating in the 5-GHz transmission band. Using the 5-GHz range disallows
interoperability of 802.11b devices as they operate within 2.4 GHz. 802.11a is capable of
supplying data throughput of 54 M pbs and with proprietary technology known as rate doubling
has achieved 108 Mbps. In production networks a more standard rating is 20 to 26 Mbps.

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