Cellular Mobile Communication
Systems
Lecture 1
Engr. Shahryar Saleem
Assistant Professor
TA: Engr. M. Fahad Khan
Department of Telecom Engineering
University of Engineering and Technology
Taxila
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Course Outline
• Introduction
– Mobile communication systems issues, system
structure, safety
• Wireless communication fundamentals
– Propagation, Modulation and Coding, Frequency
reuse. Traffic eng.
• Intersystem Operation + Mobility Management
– Location tracking and Paging, Handoff
• Second Generation Cellular (2G) :
– GSM,
– IS-95
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Course Outline
• 2.5G Cellular: Wireless Data Services
– GPRS (General Packet Radio Service)
– EDGE (Enhanced Data GSM Evolution)
• 3G Cellular:
– Structure, protocols and advance services
– UMTS (Universal Mobile Telecom. Services)
– Cdma 2000 1x EV-DO (Evolved Data Optimized)
• Location Based Systems/Services
• Wireless Local Area Networks
– 802.11, infrastructure and ad-hoc
• Hybrid WLAN and 3G
• Wireless MANs
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Course Structure
Assignments
Quizzes
Midterm
Final Exam
10%
10%
30%
50%
Text: Principles of Wireless Networks: A Unified Approach, by, Kaveh Pahlavan
and Prashant Krishnamurthy, Prentice Hall 2002.
Online Course Management System:
URL:
http://web.uettaxila.edu.pk/CMS/coeCMCSms/index.asp
Note:
• Assignments after the due date will not be accepted.
• Plagiarism will not be accepted
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Mobile vs. Wireless
• Wireless Communication System:
– Any electrical communication system that uses a
naturally occurring communication channel, such as air,
water, earth.
• Mobile wireless communication systems focus
– Communicate over the air via radio-waves
– Support some form of user mobility
• Examine how they are different from wired networks
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Wireless Issues
• Wireless link implications
– communications channel is the air
• poor quality: fading, shadowing, weather, etc.
• data rate and coverage vary
– regulated by governments
• frequency allocated, licensing, etc.
– limited bandwidth
• low bit rate, frequency planning and reuse, interference
– power issues
• Power levels regulated (safety issue), conserve mobile
terminal battery life
– security issues
• wireless channel is a broadcast medium!
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Mobility Issues
• Mobility Types
– User mobility : user can access network while mobile
• must handoff calls/connections in progress as user moves
• track users as they move so they can receive info/calls
– Service mobility: user’s services follow them
• Need to have authentication and services follow user
• Degree of Mobility
– Geographic range
• ranges from a house/apartment to worldwide
– Speed
• ranges from stationary to bullet train
• cordless phone vs. cell phone
• Mobility portable device
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Device Issues
• Mobile Device Issues
– Portability
• Device and accessories size and weight
– Usability
• User characteristics (size, dexterity, knowledge, etc.)
• Environment characteristics (Temperature, degree of mobility,
etc)
• Device Characteristics
– startup time
– data integrity and security
– cpu speed and memory size
– power supply
– user interface (keypad, stylus, voice, etc.)
– Functionality (standalone, network dependent)
– Connectability (always, partial, never)
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Mobile devices
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Wireless Networks
– Wireless Wide Area Networks (WWANs)
• Cellular Networks :
– GSM, cdmaone (IS-95), UMTS, cdma2000 EVDO
• Satellite Networks:
– Iridium, Globalstar, GPS, etc.
– Wireless Metro Area Networks (WMANs)
• IEEE 802.16 WiMAX
– Wireless Local Area Networks (WLANs)
• IEEE 802.11, a, b, g, etc. (infrastructure, ad hoc, sensor)
– Wireless Personal Area Networks (WPANs)
• IEEE 802.15 (Bluetooth), IrDa, Zigbee, etc.
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Wireless Networks
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Licensed vs. Unlicensed
• Licensed Spectrum
– need to buy right to use spectrum allocation in a
specific geographic location from the government
(e.g., AM/FM radio)
– Prevents interference – licensee can control signal
quality
• Unlicensed spectrum
– Anyone can operate in the spectrum (e.g. ISM
band for WLANs) but must maintain proper behavior
in spectrum (max power level and frequency
leakage, etc.)
– Can have interference problems
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Frequency Allocations
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Mobile Phone Systems
• Mobile phone systems
– Support communication to mobile users via wireless
radio channel
– Variety of systems and standards:
• Analog 1G : NMT, AMPS, TACS
• Digital 2G: GSM, IS-95b (cdmaone),
• 3G: UMTS, cdma 2000
– Scope of services and coverage areas growing
• SMS, MMS, laptop data, etc.
• Focus now on wireless data and location aware
services
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Cellular Network Architecture
• Cell : Area covered by 1 radio tower unit (base station)
• Cellular Systems: provide wireless coverage to a geographic
area with a set of slightly overlapping cells. Use a set of low power
radio stations to provide coverage, each cell has different set of
frequencies or codes, support handoff of mobile from one cell to
another, track mobile for incoming call
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Cellular Network Architecture
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2.5/3G/WLAN Mobile Devices
•
More Internet-friendly interface
– Wide, color screens
• More flexible to support new applications
– Voice
– Video telephony capabilities
– Web browsing
– Web Games
– Location-based services
– Streaming applications
• Various I/O modes/interfaces
– Keypad,
– voice recognition,
– character recognition,
– pen based, etc.
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Functional Units of A Cellular
Mobile Network
• Base Station (BS)
Provides radio channels between mobile units and network
Pico-cells : (indoor – 0-.5 Km) support 8-20 channels
micro-cells: (outdoor – 0-1 Km), macro-cells: (1-30 Km)
• Base Transceiver Station (BTS) - houses radio units
• Base Station Controller (BSC)
Manages a cluster of BS, channel assignment, handoff, power
control, some switching, etc
• Mobile Switching Center (MSC)
Provides switching functions , coordinates location tracking, call
delivery, handoff, interfaces to HLR,VLR, AUC, etc..
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Functional Units of A Cellular
Mobile Network
• Home Location Register (HLR)
Specialized database server contains subscriber information for
billing etc, and part of mobile information to allow incoming calls to
be routed to the MSC for a particular MS.
• Visitor Location Register (VLR)
Similar to HLR which dynamically stores subscriber information
when the subscriber is located in the area covered by the VLR.
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Wireless MANs
• Wireless Metropolitan Area Network (WMAN)
– Wireless alternative to DSL/cable modem
services for last mile broadband access.
– Point to Multipoint (PMP) protocol
– Scope expanded to include mobility and higher
data rates
– IEEE 802.16 standard
– Worldwide Interoperability for Wireless Microwave
Access (WiMAX)
• Focus on both licensed and unlicensed spectrum
deployment
• Advantages: cost, flexibility, mobility
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WiMAX Architecture
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WiMAX service Architecture
•NLOS has lower data rate up
to 32 Mbps
•LOS, where a fixed antenna
points straight at the WiMax
tower from a rooftop or pole.
can provide higher data rates
~ 75Mbps
• Point to Point Focused LOS
antennas – high data rates
with longer distances 30-40
miles suitable for wireless
backhaul ~100 Mbps
•MAC layer protocol has QoS
service specifications built in
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WiMAX service Architecture
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WiMAX Applications
• According to WiMax Forum it supports 5 classes
of applications:
• 1. Multi-player Interactive Gaming.
• 2. VOIP and Video Conference
• 3. Streaming Media
• 4. Web Browsing and Instant Messaging
• 5. Media Content Downloads
• Basically Triple Play
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Wireless LANs
• Wireless Local Area Networks
– Support communication to mobile data users via wireless channel
– Types of WLAN
1. Infrastructure based (most popular) Connect users to a wired
infrastructure network
Wireless access network like cellular phone system
IEEE 802.11, a, b, g , etc.
2. Ad-Hoc based networks
– Provide peer to peer communication – mobiles
communicate between each other directly
– Rapid Deployment (conference room)
– Bluetooth, IEEE 802.11, a, b, g Proprietary
3. Point – to – Point (cable replacement!)
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Wireless LAN Components
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IEEE 802.11Terminology
• Access Point (AP)
– Provides access to distribution services via the wireless
medium
• Basic Service Area (BSA)
– The coverage area of one access point
• Basic Service Set (BSS)
– A set of mobile stations controlled by one access point
• Distribution system
– The fixed (wired) infrastructure used to connect a set of BSS
to create an extended service set (ESS)
• Portal(s)
– The logical point(s) at which non-802.11 packets enter an
ESS
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WLAN Topologies
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Major Players
• Wireless LAN market
– Lucent (Orinoco)
– Alcatel
– Cisco
– 3Com
– Alvarion
• Indoor and Outdoor systems
– Outdoor range - up to 25 Km claimed
– Wireless ISPs in many cities
• Expand market and scope of services
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Ad-hoc Networks
• In Latin, ad hoc literally means "for this purpose only.”
• Ad-hoc network:
– A LAN or other small network, especially one with
wireless connections, in which some of the network
devices are part of the network only for the duration
of a communication session or, in the case of
mobile or portable devices, while in some close
proximity to the rest of the network.
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Ad-hoc Networks
Lap-tops in a conference room
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Why Ad-hoc Networking
• Useful when infrastructure not available, impractical, or expensive
• Technically:
– Mobile devices internetworking;
– Wireless hardware becomes a commodity ----- increasing
performance and inexpensive
– Market demand:
– Mobile conferencing, etc
– Home networking
– Emergency services
– Military applications
– Taxi-cab network
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Sensor Networks
• Specialized wireless networks to gather data from a specific system,
usually no mobility of sensor nodes
– APPLICATIONS:
Military, Environmental, Health, Home, Space Exploration,
Chemical Processing
– SENSOR TYPES:
Seismic, Low Sampling Rate Magnetic, Thermal, Visual,
Infrared, Acoustic, Radar…
– SENSOR TASKS:
Temperature, Humidity, Vehicular Movement, Lightning
Condition, Pressure, Soil Makeup, Noise Levels, Presence or
Absence of Certain Types of Objects, Mechanical Stress
Levels on Attached Objects, Current Characteristics (Speed,
Direction, Size) of an Object ….
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Example Sensor Network
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Wireless Personal Area Networks
• Origins in the BodyLAN project initiated by BBN in the
early 1990s
• Networking “personal” devices – sensors, cameras,
handheld computers, audio devices, etc. with a range of
around 5 feet around a soldier
• Today: Networking digital cameras to cell phones to
PDAs to laptops to printers to etc..,
• Most popular application – handsfree headset to
cellphone
• IEEE 802.15 standard (Bluetooth)
– Use band available globally for unlicensed users
– Low powered – medium data rate ~100s kbps
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Applications of WPAN
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QUESTIONS ?
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