Bisha University
ELECTRICAL ENGINEERING DEPARTMENT
Wireless Communication Systems
Books & References
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Books:
1. “Wireless Communications & Networks”
by William Stallings, PHI, ISBN:0-13-191835-4, 2005
2.“B. A. Forouzan, Data communications and
networking, McGraw Hill, 5th Edition, 978-007337622-6, 2013.
3.Theodore S. Rappaport, Wireless Communications:
Principles and Practice, Practice Hall, 1996. ISBN:
ISBN 0-13-375536-3
Books & References
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References:
1)“Computer Networking” by Kurose &
Ross, Addison-Wesley (6th Edition),
2012, ISBN-10: 0132856204
2) “Course Notes” by Prof. R.K.Rao
Course Plan
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Assignments 10 %
Quizzes 10%
Mid-term 20%
Lab report 10 %
Final Exam 50 %
Leader
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Start a connection channel with
students
Mange Groups and solve problems
Answer Questions
Attend all Classes
Reminder for deadline
Introduction to Wireless LANs
8
Wireless Comes of Age
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Marconi invented the wireless telegraph in 1896
 Communication by encoding alphanumeric characters in
analog signal
 Sent telegraphic signals across the Atlantic Ocean
Advances in wireless technology
 Radio, television, mobile telephone, communication
satellites
More recently, Satellite communications, wireless
networking, cellular technology
Wireless Comes of Age (cont.)
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Communication Satellites were introduced in the 1960s
Wireless Networking is allowing businesses to develop LANs,
WANs and MANs without a cable plant
IEEE has developed 802.11 as a standard for WLAN
Cellular or Mobile telephone is the modern equivalent of
Marconi’s wireless telegraph
Wireless Communications is responsible for “shrinking” the
world
The Cellular Revolution
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The cellular revolution is apparent in the growth of the
mobile phone market alone
Number of users in 1990-11 million
Number of users today exceeds 1billion
The number of wireless phones outnumbered fixed-line
phones in 2002
In 2005 number of wireless Internet devices exceeded the
number of wired Internet devices
All these point to the success of Wireless
Broadband Wireless Technology
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The Internet is increasingly a multimedia experience-graphics, audio, and
video abound on the web pages
Higher data rates obtainable with broadband wireless technology
 Graphics, video, audio
Broadband Wireless service shares same advantages of all wireless
services: convenience and reduced cost
 Service can be deployed faster than fixed service
 No cost of cable plant
 Service is mobile, deployed almost anywhere
Limitations and Difficulties of
Wireless Technologies
Political and technical difficulties inhibit wireless technologies
from reaching their full potential
 Device limitations also restrict free flow of data
 E.g., small LCD on a mobile telephone can only display a
few lines of text
 E.g., browsers of most mobile wireless devices use
wireless markup language (WML) instead of HTML
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Wireless LANs
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A WLAN provides all the features and benefits of traditional
LAN technologies (such as Ethernet and Token Ring),
without the limitations of wires & cables
Areas are measured not in feet or meters but in miles or
kilometres
Infrastructure need not be buried in the ground or hidden
walls
An infrastructure can move and change with the
organization
What is a WLAN?
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WLANs use a transmission medium just like wired LANs
Instead of using Twisted-pair or Fibre-optic cable WLANs
use infrared (IR) or radio frequencies (RFs)
*RF is far more popular because of its
1) Longer range
2) Higher Bandwidth
3) Wider Coverage
Wireless LANs
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Rapidly evolving technology
Connectivity no longer implies attachment
Freedom to roam while still maintaining
connectivity
WLANs use infrared light (IR) or radio
frequency (RF) as transmission media
Wireless LANs
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Use 2.4 and 5 GHz frequency bands
These portions of RF spectrum are reserved
in most of the world for unlicensed devices
The free unlicensed portions of the radio
spectrum enable manufacturers to avoid
billions of dollars in licensing fees
Why Wireless?
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Current Ethernet LANs operate at speeds of
100Mbps (access layer), 1Gbps (distribution
layer), and 10 Gbps (core layer)
WLANs operate at 11 to 54 Mbps at the
access layer
The cost of implementing WLANs is
competitive with implementing wired LANs
Why Wireless?
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So why install a system that is at the lower end of
the current bandwidth capabilities?
Reasons are:
In many small LAN environments, the lower speeds
are enough to support application and user needs
With many offices now connected to the Internet by
broadband services
Why Wireless?
(such as DSL and cable), WLANs can handle
the bandwidth demands
WLANs allow users to roam with freedom
and still remain connected
During office reconfigurations, WLANs do
not require rewiring and its associated costs
Why Wireless?
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Some of the major benefits of WLANs are:
Mobility
Scalability
Flexibility
Short- and long-term cost savings
Installation advantages
Reliability in harsh environments
Reduced installation time
Environments that benefit
from WLANs
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Require standard 10-Mbps Ethernet LAN speeds
Benefit from roaming users
Reconfigure the physical layout of the office often
Expand rapidly
Use a broadband Internet connection
Face significant difficulties installing wired LANs
Need connections between two or more LANs
Require temporary offices and LANs
Value-added features of WLANs
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IT professionals or business executives who want mobility
within the enterprise, in addition to a wired network
Any company site that is not conducive to LAN wiring
because of building or budget limitations, such as older
buildings, leased space or temporary sites
Any company that needs the flexibility and cost savings
offered by a line-of-sight, building-to-building bridge that
avoids expensive trenches, leased lines, and right of way
issues
WLANs
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Even though WLANs are primarily designed
as LAN devices, they can be used to provide
site-to-site connectivity at distances up to 40
Km
Use of WLAN device is much more cost
effective than using WAN bandwidth or either
installing or leasing long fibre runs.
Wireless Devices
Wireless LAN Antennas
Evolution of WLANs
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Very first WLAN technology was very low-speed (1 to 2
Mbps) and was proprietary (Vauled)
As WLAN became more popular, the need for Ethernet-like
standard became important
In 1991 several vendors joined together and formed the
WECA (Wireless Ethernet Compatibility Alliance)
Later WECA changed its name to the Wi-Fi Alliance
In June 1997, the IEEE released the 802.11standard for
wireless LAN
Wireless LAN Standards
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WLANs are regulated by the same types of laws
used to govern such things as AM/FM radios
The Federal Communications Commission (FCC)
regulates the use of WLAN devices
In the US, standards are created and maintained
by IEEE
These standards are created by groups of people
that represent many organizations
Wireless LAN Standards
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IEEE 802.11-original WLAN standard, specifies lowest data
transfer rates for RF and light-based transmission
technologies
IEEE 802.11b-somewhat faster data rates, promoted by WiFi Alliance
IEEE 802.11a-much faster data rates, uses 5GHz UNII
bands, lacks backward compatibility
IEEE 802.11g-data transfer rates equal to IEEE 802.11a,
provides backward compatibility
Evolution of Standards : a, b, g
Speed
Network
Radio
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900 MHz
2.4 GHz
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1990
IEEE 802.11Begins
Drafting
1992
1996 1994
802.11
Ratified
802.11a,b 802.11g
Ratified
Ratified
1998
2000
More later!
Up to 54 Mbps
5 GHz
Not compatible with either 802.11b or 802.11g
802.11b
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1988
Up to 11 Mbps
2.4 GHz
802.11g
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Up to 54 Mbps
2.4 GHz
5 GHz
2.4 GHz
802.11a
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Standards-based
Proprietary
⯆
1986
11 Mbps 54 Mbps
1 and
2 Mbps
1 and
2 Mbps
860 Kbps
802.11g is backwards compatible
with 802.11b, but with a drawback
(later)
2003
Evolution of WLANs
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802.11 WLAN standards allow for data transmission over air
Specified signalling technologies include:
-IR light
-Three types of radio transmission within the unlicensed 2.4GHz
Frequency bands: Spread Spectrum
FHSS (Frequency Hopping Spread Spectrum)
DSSS (Direct Sequence Spread Spectrum)
OFDM (Orthogonal Frequency Division Multiplexing)
-One type of radio transmission within the unlicensed 5-GHz frequency
band
ISM Unlicensed Frequency Bands
ISM: Industrial, Scientific & Medical
Atmosphere: the wireless
medium
Wireless signals are electromagnetic waves
No physical medium is necessary
The ability of radio waves to pass through walls and cover great
distances makes wireless a versatile way to build a network.
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WLAN Growth & Applications
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Speed: IEEE 802.11b 11Mbps data rate meets
enterprise standards for performance. 802.11a
offers 54 Mpbs, 802.11n offers 450 Mbps but
802.11ac offers a 1300 Mbps data rate
Positioning: Positioning WLANs as a way to
complete the LAN/WAN networking solution
simplifies technology adoption decisions
Also, it encourages customers to include wireless
technology in their strategic networking plans
WLAN Growth & Applications
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Value: Lower costs with acceptable performance
make wireless an attractive alternative to wired
solutions
Ease of implementation: Instant solutions and
easily implemented alternatives accelerate market
adoption
Security: With increased instances of attacks and
security breaches, consumers and businesses are
concerned about network protection
Wireless LAN growth
Key Market Drivers
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Increased Performance
Lower Costs
Ease of implementation
Applications Areas:
Retail; Warehouses; Healthcare; Insurance; Real
Estate; Transportation; Hospitality and
Conventions; Energy and Utilities; Vending;
Education; Travel and recreation; Military ...
Momentum is Building in Wireless
LANs
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Wireless LANs are an “addictive” technology
Strong commitment to Wireless LANs by technology heavyweights
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Cisco, IBM, Intel, Microsoft, Apple
Embedded market is growing
Laptop PC’s and Tablets with “wireless inside”
 Smart Phones are next
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The WLAN market is expanding from Industry-Specific
Applications, to Universities, Homes, & Offices
Professionals and Experts in Wireless LANs & MANs will be in
great demand in the future
Wireless LANs Are Taking Off
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 Standards
 High Bandwidth Needs
 Low Cost
 Embedded in Laptops
 Variety of Devices
 Voice + Data
 Multiple Applications
 Security Issues Solved
 Ease of Deployment
 Network Mgmt. Tools
 Enterprise Adoption
Wireless LANs & WANs
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It is not wise to assume that wireless is just
like any other form of networking
Wireless LANs & WANs are fields of study all
their own
If you are new to Networking, be sure to
have a basic understanding of networking
concepts
WLAN Challenges & Issues
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Radio Signal Interference & Degradation
Power Management
Interoperability
Network Security
Reliability & Connectivity
Installation & Site Design Issues
Health Issues
Radio Signal Interference
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In metropolitan area building-to-building designs, it is
possible to have third party interference from other
companies using wireless bridging or wireless devices
operating in the same frequency band
In such a situation network managers must ensure that
different channels are used
Interference cannot be always detected until the link is
implemented
Because 802.11 standards use unlicensed spectrum,
changing channels is the best way to avoid interference
Radio Signal Interference
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Many other devices, such as portable phones,
microwaves, wireless speakers, and security
devices, also use these frequencies
Operation in unlicensed bands carries higher risk of
interference
Two warnings to be aware of are:
Interference from other wireless installations in
licensed and unlicensed bands
EMI
Power Management
Power consumption is always an issue with laptops and
PDAs, because the power and battery have limited lives
 Constant Awake Mode (CAM): Best for devices when power
is not an issue. Provides the best connectivity option
 Power Save Mode: Selected when power conservation is of
utmost importance. Wireless NIC goes to sleep after a
period of inactivity and periodically wakes to retrieve
buffered data from Access Point (AP)
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Power Management
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Fast Power Save Mode: A combination
of the above two. It is good for clients
who switch between AC and DC power.
Most wireless clients use Fast Power
Save Mode.
Interoperability
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Most vendors want their customers to use
their APs and NICs exclusively
Often they offer some degree of reduced
capability if there is a need to mix and match
different brands of APs and NICs
When designing WLANs this aspect must be
considered carefully
Network Security
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Researchers have exposed several vulnerabilities to the
authentication, data privacy, message integrity mechanisms
defined in IEEE 802.11 (a, b, and g) specifications
As wireless networks grow, the threat of intruders from the
inside and outside is great
IEEE’s WEP (Wired Equivalent Privacy) provides robust
authentication options
IEEE is also looking into Advanced Encryption Standard
(AES) in 802.11i
Reliability and Connectivity
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WLANs include mechanisms to improve the reliability of the
packet transmissions to be at least the same level as wired
Ethernet
Using TCP/IP protocols helps protect the network against
any loss or corruption of data over the air
Most WLANs use spread-spectrum technology, which is a
broadband RF technique developed by the military for use in
reliable, secure, mission critical communication systemsFHSS, DSSS, OFDM
Wireless network designers must also be aware of
connection issues due to changing environments
Installation & Site Design
Issues
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Not all sites are created equal
Even similar sites can be very different, even if they appear
to be uniform
Because of differences in component configurations,
placement, and physical environment, every infrastructure
application is unique
In a point-to-point bridging scenario, the following
obstructions might obscure a visual link: topographical
features, curvature of earth, buildings and other man-made
objects, and trees
Health Issues
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There are many unknowns concerning the safe limits of
human exposure to RF radiation
The general rule is to not subject living beings to radiated
RF energy unnecessarily
You should not stand in front of, or in close proximity to,
any antenna that is radiating a transmitted signal
Directional antennas pose potentially hazardous emission
levels only at the front of the antenna
Guidelines for emissions are set by FAA, FCC etc.
Applications of Wireless LAN
(Access Role)
Access Role
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WLANs are mostly deployed in an access role-entry
point into wired network
In the past, access has been defined as dial-up,
ADSL, Cable, cellular etc.
Wireless is simply another method for users to
access the network
Not typically implemented at Distribution and Core
layers
WLANs offer specific solution to difficult problem:
mobility
Applications of Wireless LAN
(Building-to-Building Connectivity)
Applications of Wireless LAN
(Bldg-to-Bldg Connectivity)
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Using WLAN technology, equipment can be installed
easily and quickly to allow two or more buildings to
be part of the same network
This avoids the use of expensive leased lines or the
need to dig up the ground between buildings
With proper antennas, any number of buildings can
be linked together on the same network
Applications of Wireless LAN
(Last Mile Service)
WISP: Wireless Internet Service Provider
Applications of Wireless LAN
(Last Mile Service)
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‘Last Mile’ refers to the communication
infrastructure that exists between the Central Office
of Telco or cable company and the end-user
If one lives in a rural area, chances are that one
does not have access to a broadband connection
(cable or ADSL)
It is cost effective for WISP to offer wireless access
to these remote locations
Applications of Wireless LAN
(Mobility)
Applications of Wireless LAN
(Mobility)
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For example, a parcel delivery company uses
wireless technology to update parceltracking data immediately upon the arrival of
the delivery vehicle
As the driver parks at the dock, the drivers
computer has already logged onto the
network and transferred the day’s delivery
data to the central network
Applications of Wireless LAN
(SOHO)
Applications of Wireless LAN
(SOHO)
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As a professional, you may have more than one
computing device at your home
Then you most likely want these devices to be
networked together so that you can share files,
a printer, or a broadband connection
For small office home office (SOHO) a WLAN is
a very simple and effective solution
Applications of Wireless LAN
(School with Mobile Classrooms)
School with Mobile Classrooms
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Due to overcrowded classrooms, many schools use
mobile classrooms.
These classrooms usually consist of large, moveable
trailers that are used while more permanent
structures are built
Wireless LAN connections from the main building to
the mobile classrooms allow flexible configurations
at a fraction of the cost of alternate cabling
Assignment 1:
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1.5
1.8
1.9
1.10
1.11
Theodore S. Rappaport, Wireless Communications:
Principles and Practice, Practice Hall, 1996. ISBN:
ISBN 0-13-375536-3