Introduction
UMM ALQURA UNIVERSITY
ELECTRICAL ENGINEERING DEPARTMENT
EE 802460 Modern Wireless Communication Systems Second Semester 1439
Books & References
Books:
“Wireless Communications & Networks”
by William Stallings, PHI, ISBN:0-13- 191835-4, 2005
“B. A. Forouzan, Data communications and networking, McGraw Hill, 5th
Edition, 978-0-07337622-6, 2013.
Books & References
References:
1) “Computer Networking” by Kurose &
Ross, Addison-Wesley (6
thEdition), 2012, ISBN-10: 0132856204
2) “Course Notes” by R.K.Rao
Mid-term and Final Exams
In both Mid term and Final Examination are Limited Open Book exams, no text books, notes, crib sheets etc. are
allowed
Only a calculator is permitted (for
example, HP-48g+, TI-84)
Topics
Wireless Radio Technology Fundamentals
Cellular Radio Architectures
Satellite Networks
Cellular Wireless Networks
Wireless LAN & WAN Technologies
IEEE 802.11 Standards
Introduction to Wireless LANs
Wireless Comes of Age
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.)
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
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
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
Wireless LANs
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
What is a WLAN?
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
Wireless LANs
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
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?
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?
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 adequate 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?
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
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
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
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
Very first WLAN technology was very low-speed (1 to 2 Mbps) and was proprietary
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
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
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 Wi- Fi 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
802.11a
Up to 54 Mbps
5 GHz
Not compatible with either 802.11b or 802.11g
802.11b
Up to 11 Mbps
2.4 GHz
802.11g
Up to 54 Mbps
860 Kbps
900 MHz
1 and 2 Mbps
2.4 GHz Proprietary
802.11 Ratified
802.11a,b Ratified
1986 1988 1990 1992 1994 1996 1998 2000 2003
1 and 2 Mbps
2.4 GHz
11 Mbps 54 Mbps Standards-based
5 GHz Radio
Network Speed
IEEE 802.11Begins Drafting
802.11g is backwards compatible with 802.11b, but with a drawback
802.11g Ratified
More later!
Evolution of WLANs
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:
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
WLAN Growth & Applications
Speed: IEEE 802.11b 11Mbps data rate meets enterprise standards for performance. 802.11a offers a 54Mbps 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
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
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
Wireless LANs are an “addictive” technology
Strong commitment to Wireless LANs by technology heavy- weights
Cisco, IBM, Intel, Microsoft
Embedded market is growing
Laptop PC’s and Tablets with “wireless inside”
Smart Phones are next
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
$1.7
$2.6 $3.3
$6.0
$9.0
$10.3
$0.0
$1.0
$2.0
$3.0
$4.0
$5.0
$6.0
$7.0
$8.0
$9.0
$10.0
$11.0
2001 2002 2003 2004 2005 2006
Future Growth Due To:
✓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
Wireless LANs & WANs
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
Radio Signal Interference & Degradation
Power Management
Interoperability
Network Security
Reliability & Connectivity
Installation & Site Design Issues
Health Issues
Radio Signal Interference
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
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)
Power Management
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
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
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
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 systems-
FHSS, DSSS, OFDM
Wireless network designers must also be aware of
Installation & Site Design Issues
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
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
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:
Applications of Wireless LAN
(Building-to-Building Connectivity)
Applications of Wireless LAN (Bldg-to-Bldg Connectivity)
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)
‘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)
For example, a parcel delivery company uses wireless technology to update parcel-
tracking 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)
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
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
