Wireless Technologies
LAN’s & WAN’s
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Contents
1 Introduction to WiFi & WiMAX
2 Deploying Wireless LAN’s
3 LAN Summary
4 Deploying Wireless WAN’s
5 LAN Summary
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Evolution of Wireless Standards
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802.11b
802.11a
802.11g
802.16a
The Wi-Fi Alliance is a nonprofit international association
formed in 1999 to certify interoperability of wireless Local
Area Network products based on IEEE 802.11 specification.
http://www.wi-fi.org
The WiMAX Forum is a non-profit corporation with a goal of
promoting deployment of broadband wireless access
networks. Our member companies support the industry-wide
acceptance of the IEEE 802.16 standard.
http://www.wimaxforum.org
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What is 802.11b
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•
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802.11b, or IEEE 802.11b, is a standard that has been developed by
the IEEE (Institute of Electrical and Electronic Engineers),
http://standards.ieee.org. The IEEE is an international organization
that develops standards for hundreds of electronic and electrical
technologies. The organization uses a series of numbers, like the
Dewey Decimal system in libraries, to differentiate between the
various technology families.
The 802 committee develops standards for local and wide area
networks (LANs and WANs). For example, the 802.3 committee
develops standards for Ethernet-based wired networks, the 802.16
committee develops standards for wireless wide area networks
(WAN), and the 802.11 committee develops standards for wireless
local area networks (LAN).
802.11 is then further divided: 802.11b, or Wi-Fi, is a standard for
wireless LANs operating in the 2.4 GHz spectrum with a bandwidth of
11 Mbps. 802.11a is a different standard for wireless LANs operating
in the 5 GHz frequency range with a maximum data rate of 54 Mbps.
Another draft standard, 802.11g, is for WLANs operating in the 2.4
GHz frequency but with a maximum data rate of 54 Mbps.
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Standards – Frequencies - Throughputs
2Part Concept
Standards &
Throughputs
•802.11b 11Mbps
•802.11a 54Mbps
•802.11g 54Mbps
Frequencies
•2.4GHz
•5.8GHz
•2.4GHz
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RF Modulation
DSSS
OFDM
FHSS
802.11b/g
3 Non-overlapping
Channels
802.11a
4-8 Non-overlapping
Channels
Hops
Across
allocated
spectrum
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Example Non-Overlapping Channels
• N o m in a l 2 0 M H z C h a n n e l B a n d w id th
• T o ta l o f 9 C h a n n e ls a va ila b le (4 n o n -o ve rla p p in g )
Channel
F re q u e n c y
1
5735 M Hz
1A
5745 M Hz
2
5755 M Hz
2A
5765 M Hz
3
5775 M Hz
3A
5785 M Hz
4
5795 M Hz
4A
5805 M Hz
5
5815 M Hz
5.8GHz OFDM
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AP Placement
1
6
11
Channel
Planning
6
11
11
6
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Deploying Wireless LAN’s
1. How many wireless networked computers can use a single access point?
This depends upon the manufacturer. Some hardware access points have a
recommended limit of 10, with other more expensive access points supporting up
to 100 wireless connections.
2. Can I have more than one access point?
Yes, multiple access points can be connected to a wired LAN, or sometimes even
to a second wireless LAN if the access point supports this.
In most cases, separate access points are interconnected via a wired LAN,
providing wireless connectivity in specific areas such as offices or classrooms, but
connected to a main wired LAN for access to network resources,
such as file servers or the Internet.
3. What is the range of a wireless network?
Typical indoor ranges are 150-300 feet,
but can be shorter if the building construction
interferes with radio transmissions. Outdoor
are quoted up to 1000 feet, but again
depends upon the environment.
this
ranges
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Deploying Wireless LAN’s
4. Can I use a wireless network to interconnect two LANs?
Yes. Wireless networking offers a cost-effective solution to users with difficult
physical installations such as campuses, hospitals or businesses with more than
one location in immediate proximity but separated by public thoroughfare. This
type of installation requires two or more access points. Each access point acts as
a bridge or router connecting its own LAN to the wireless connection. The wireless
connection allows the two access points to communicate with each other, and
therefore interconnect the two LAN's.
5. Can networking software identify a wireless
computer in the same way it can identify an
Ethernet computer on the network?
Wireless cards look just like Ethernet cards
to your network drivers. In fact, wireless
networking cards have unique MAC hardware
addresses that are formatted like Ethernet
hardware addresses allocated from the same
standards organization.
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Wireless LAN Site Surveys
The traditional method for performing an RF site survey includes a laptop equipped
with an 802.11 PC Card and site survey software supplied at no additional cost
from the radio card vendor. The software features vary greatly by vendor, but a
common function among them all displays the strength and quality of the signal
emanating from the access point. This helps determine effective operating range
(i.e., coverage area) between end users and access points.
For example, after "best guessing" the potential position of access points for adequate
coverage and overlap, you verify your thoughts by placing an access point at each
location, and then walk around with the laptop while monitoring and noting signal
levels. The goal is to verify the maximum distances that will maintain adequate
signal levels, generally the value that continues to enable operation at the
planned data rate (e.g., 11 Mbps). If the predetermined location of an access
point doesn't provide the coverage you had in mind, then reposition or include
additional access points and repeat the testing.
Advanced tools let you "see" wireless LANs
Advanced 802.11 site survey tools include spectrum analyzers, like the Air
Magnet, providing the "eyes" and "ears" that let you understand the affects of the
environment on the transmission of 802.11 signals. For example, an 802.11b
spectrum analyzer graphically illustrates the amplitude of all signals falling within
a chosen 22 MHz channel. This enables you to distinguish 802.11 signals from
other RF sources that may cause interference, making it possible to locate and
eliminate the source of interference or use additional access points to resolve the
problem.
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Wireless LAN Security
1. What about security?
Wireless communications obviously provide potential security issues, as an
intruder does not need physical access to the traditional wired network in order to
gain access to data communications. To protect against any potential security
issues, 802.11 wireless communications have a function called WEP (Wired
Equivalent Privacy), a form of encryption which provides privacy comparable to
that of a traditional wired network. If the wireless network has information that
should be secure then WEP should be used, ensuring the data is protected at
traditional wired network levels.
2. Aren’t there Problems with WEP
On 802.11 networks, you can enable WEP, which encrypts the body of each frame. This
is supposed to keep hackers from viewing sensitive e-mails, user names and passwords,
proprietary documents, etc. Hackers can fairly easily decode WEP-encrypted information
after monitoring an active network for less than one day.
Consequently, don't depend on WEP for protecting sensitive information. The use of
WEP in most cases, nevertheless, is better than no encryption at all, especially if you
deploy a mechanism to change the WEP key often. Recent improvements from
manufacturers have begun to include AES and 3DES encryption within the radios.
Also it should be noted that traditional Virtual Private Networking (VPN)
techniques will work over wireless networks in the same way as traditional
wired networks.
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Wireless LAN Summary
Wireless LAN installation is tricky. Unlike wired networks, you can't visualize
the wireless medium. The construction of a facility and silent sources of RF
interference impact the propagation of radio waves, often in odd ways. This
hinders your ability to plan the location of access points.
How do you avoid these drawbacks? Perform an RF site survey using
appropriate site survey tools that help you plan access point locations for
adequate coverage and resiliency to potential RF interference.
There are many wireless LAN security issues that require attention. If and how
you handle these problems depends greatly on your security requirements. In
some cases, you might want to keep the network as open as possible and only
protect files on user PCs. Most other scenarios, however, will likely need much
more. It's possible to make wireless LANs very secure with the proper planning
and management.
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Deploying Wireless WAN’s
Revolutionary Technology:
Technological improvements in the broadband wireless
arena have been rapid and significant in recent years,
offering greater performance and flexibility in
deployments while reducing investment risks and
ongoing operating expenses.
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Line-of-Sight
The Line of Sight Concept
An optical line of sight exists if an imaginary straight line can be drawn connecting the antennas on either
side of the link.
Clear Line of Sight
A clear line of sight exists when no physical objects obstruct viewing one antenna from the location of
the other antenna.
A radio wave clear line of sight exists if a defined area around the optical line of sight (Fresnel Zone) is
clear of obstacles.
Fresnel Zone
The Fresnel zone is the area of a circle around
the line of sight.
The Fresnel Zone is defined as follows:
When at least 80% of the first Fresnel Zone is
clear of obstacles, propagation loss is equivalent
to that of free space.
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Studies & Design
Topology Studies
Topo Studies are a requirement for any outdoor
deployment to ensure a proper design for LOS (Line
of Sight) or NLOS (Near Line of Sight) Connections.
Link Budget Calculations
Once you determine the distance and topology of
your link you must run Link Budgets for each link to
ensure proper connection, throughput, and link
reliability.
Spectrum Analysis
Prior to deployment a site survey including a
complete spectrum analysis will help to identify any
potential interfering systems and channel space that
is best suited for the individual sites.
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What is WiMAX or 802.16a?
The 802.16/HiperMAN for 2-11 GHz is a wireless metropolitan area network (MAN) technology that provides
broadband wireless connectivity to Fixed, Portable and Nomadic users. This powerful OFDM and NLOS
technology can be used to backhaul LANs to the Internet, provide inter-campus connectivity, and enable a
wireless alternative to cable, DSL, T1’s or even fiber or DS3’s.
It provides up to 50-kilometers of service area range, allows users to get broadband connectivity without
needing direct line of sight with the base station, and provides total data rates of hundreds of Mbps per base
station - a sufficient amount of bandwidth to simultaneously support hundreds of businesses with T1/E1-type
connectivity and thousands of homes with DSL-type connectivity with a single base station.
802.16/HiperMAN Technology Specs

Based on IEEE 802.16 and ETSI HiperMAN - WiMAX selected the common mode of operation of
these two standards - 256FFT OFDM.

Concentrated in 2-11GHz Wireless MAN (Metropolitan Access Networks), with the following set of
features:
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Service area range 50km

Non Line of Sight
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QoS designed in for voice/video, differentiated services

Very high spectrum utilization: 3.8 bit/Hz

Up to 280Mbps per base station
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True broadband for portable users - based on IEEE 802.16e enables the creation of a ‘CPE-less’
broadband market, providing broadband connectivity for laptops and PDAs with integrated WiMAX
technology
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Sectorial Cell Architecture
The Line of Sight Concept
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Micro-Cell Architecture
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Wireless Broadband
Summary
The growing demand for broadband services on a global scale is clear and uncontestable
Businesses, public institutions and private users regard it as an enabling technology and it has
become a given requirement for delivering communications services in the Information Age. In
last mile markets where traditional cable or copper infrastructures are either saturated, outdated
or simply out of reach, Broadband Wireless Access (BWA) technology fills the void admirably,
providing highly efficient and cost effective access services for millions
of subscribers who would otherwise be left out of the loop.
The introduction of the Wireless MAN
standards (802.16 and HiperMAN) and the
guidelines set forth by the WiMAX Forum
to ensure its success, will do much to
encourage the growth of broadband
wireless markets everywhere,
benefiting everyone…