CSc 82020
Wireless Networking and Mobile Computing
Prof. Shamik Sengupta
Office 4210 N
ssengupta@jjay.cuny.edu
http://jjcweb.jjay.cuny.edu/ssengupta/
Fall 2010
What is the course about?
Wireless networking and mobile computing
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In-depth coverage of the wireless technologies
Understanding the tradeoffs and limitations of different wireless
networking architectures and protocols
Improving your skills of analyzing/solving wireless network design
problems
Theoretical knowledge development as well as hands on experience
and prototype development
Goals:
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Learning applications, concepts, practice…
Enjoy…
Timing and Contact Information
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Class meeting time: Tuesday (6:30pm – 8:30pm)
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Office hours and location:
– John Jay College Campus (Columbus Circle), North Hall Building, 4210N
– Tuesday, 4pm – 5 pm
– To be decided @ GC
– Tuesday, 5pm – 6 pm
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Email: ssengupta@jjay.cuny.edu
Office Phone: 212-237-8826
Class WWW site: http://jjcweb.jjay.cuny.edu/ssengupta/
Blackboard online
Course Material Information
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No single textbook
Class notes and slides
References to current materials from journals, magazines and other
websites
Few Reference Texts:
1. Wireless Networks by P. Nicopolitidis, M. S. Obaidat, G. I. Papadimitriou, A. S.
Pomportsis. Publisher: Wiley. ISBN-10: 0470845295. ISBN-13: 9780470845295.
2. Wireless Communications: Principles and Practice by Theodore S. Rappaport.
Publisher: Prentice Hall; 2nd edition. ISBN-10: 0130422320. ISBN-13: 9780130422323.
3. Wireless Communications & Networking by Vijay Garg. Publisher: Morgan
Kaufmann; 1st edition. ISBN-10: 0123735807. ISBN-13: 978-0123735805.
4. Wireless Communications & Networks, 2nd edition by William Stallings. ISBN10: 0131918354. ISBN-13: 9780131918351.
Course Material Information (contd.)
 Other References:
– ACM digital library - http://portal.acm.org/dl.cfm
– IEEE Xplore - http://ieeexplore.ieee.org/
 Reading list in the class website
– Will be updated continuously
Course Syllabus Overview
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Wireless Introduction
Wireless Communication
The Cellular concept
Wi-Fi (IEEE 802.11)
Wimax (IEEE 802.16)
Wireless personal area network (WPAN)
Ad hoc, sensor, mesh networking
Single channel and multi-channel networks
Dynamic Spectrum Access (DSA) and Cognitive Radio (CR)
Economics of wireless spectrum
Mobile IP, Mobility management
Wireless security and vulnerabilities
Grading Information
 Workload and grading:
Course work
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Project & Presentation
40%
Homework assignments
30%
Midterm exam
30%
No final exam
Extra-credit assignments as decided by Instructor
Late policy
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approx %
Submission will not be accepted after due date
Permission needed for exceptional circumstances
Attendance needed
Project & Presentation
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Project: (Approx. 15 weeks time)
– The term project is a original research project related to any topic
in wireless
– A 1-page initial proposal is due by 9/21/2010
– Individual Project or 2-person team project
– Collaborated project is expected to show synergy
– The project paper is due at the end of the semester
– Presentation (approx. 20 min.)
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Decide your topic as soon as possible and discuss with me. Start as
early as possible.
Questions…??
Lecture 1
Wireless Introduction
Why Wireless?
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Advantages
– Mobility (on the go)
– Flexibility (any place, any time, temporary, permanent)
– No problems with wiring (e.g. historical buildings, fire protection,
esthetics), also cost reducing
– Robust against disasters like earthquake, fire; in emergency situations
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It has really been a wireless revolution decade…with more to come
Wireless is no longer a luxury but a necessity
Wireless Technology is everywhere
Driven by technology and vision
Wireless technologies
Device miniaturization
Mobile computing platforms
Need for ubiquitous connectivity
The field is moving fast
Image courtesy: Google
The Wireless Revolution
Cellular is the fastest growing sector of communication industry
(exponential growth since 1982, with over 2.5 billion users
worldwide today)
– Wireless mobile services grew from 11 million subscribers worldwide in
1990 to over 2 billion in 2005
– In the same period, the Internet grew from being a curious academic tool to
about 1 billion users
Estimated Global Subscribers mid 2006
2500
2200
2000
[subs x000,000]
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1500
1023
1000
500
250
0
Internet
Cell Phones Broadband
WLAN Market: WiFi
Worldwide WLAN Infrastructure
Shipments (Source: Gartner)
Forecast Sales of Wi-Fi Equipment
(Source: InfoTech Trends)
5
7
4
Millions of Units
6
$-bil
3
2
5
4
3
2
1
1
2001
2002
2003
2004
2005
20
01
20
02
20
03
20
04
20
05
20
06
20
07
0
0
WLAN growing exponentially
Today, NY city is totally
covered by Wi-Fi hotspots
Source: Pyramid Research
Source: AirTight Networks
Today, Variety of Wireless-Capable Devices
But how did it all get started?
Image courtesy: Google
An overview of Wireless Networks
Wireless History
•1895: Marconi demonstrated the first radio based wireless transmission
•1901: First radio reception across the Atlantic Ocean
•1924: First Mobile Radio Telephone
Image courtesy: Google
Early Cellular Systems
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1940s-50s: cellular concept discovered
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1946: First Mobile Telephone System (MTS) introduced in 25 cities in
USA
Half-duplex
Everything was “manual” in MTS
Maximum 3 calls supported!!!
Huge Mobile transceivers
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1960: Improved MTS (IMTS)
Automatic call switching and full duplex
Supported 23 channels
MTS & IMTS used high power BS and used the spectrum inefficiently
Image courtesy: Google
Early Cellular Systems (contd.)
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Post-1960: High power BS replaced by low-power low
coverage stations
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1st Generation (1G): Analog Systems
– Designed in late 1960s but due to regulatory delays deployed in
early 1980s
– 1983: The first analog cellular system deployed in Chicago:
Advanced Mobile Phone System (AMPS), saturated by 1984
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2nd generation (2G): Digital Systems: early 90s
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Represent voice signal digitally
Higher capacity
Higher speed
Reduced cost and power efficiency of digital hardware
Encryption
Early Cellular Systems (contd.)
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A number of 2G systems became very popular…
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Global System for Mobile Communications (GSM) became famous
in Europe and partly in USA
– Operating around 900 MHz and also in 1800 MHz
– Primarily for voice
– GSM defines number of frequency channels, divided into uplink and downlink, in
turn divided into timeslots
– We will study GSM in detail later in this class…
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High Speed Circuit Switched Data (HSCSD) and General Packet
Radio Service (GPRS)
– Extension of GSM: Primarily for data applications
– GPRS is packet switched while GSM and HSCSD are circuit switched network
– *** What is circuit switching and packet switching? ***
Circuit Switching
 End-end resources
reserved for “call”
– dedicated bandwidth
resources: no sharing
– circuit-like (guaranteed)
performance
– call setup required
Packet Switching
C
A
B
1.5 Mb/s
queue of packets
waiting for output
link
D
each end-end data stream divided into packets
 user A, B packets share network resources
 each packet uses full link bandwidth
 resources used as needed
E
Wireless Data Systems
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Characteristics of data systems are different from voice systems
– Data systems are characterized by bursty transmissions
– Unless there is a packet to transmit, terminals remain idle
– Appropriate for packet switching and sharing the resources among multiple users
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ALOHANET developed at University of Hawaii, first wireless data systems, 1971
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Wireless data systems revolutionized by Wireless LAN
– Commenced in the late 1980s
– Driven by FCC’s decision to authorize license-free bands
– Provide high speed data within a relatively small region
– IEEE standard 802.11
– Will study IEEE 802.11 system in detail
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A wide variety of wireless data systems now exist – can be categorized based on
coverage area
IEEE Wireless Standards
RAN
IEEE 802.22
WAN
IEEE 802.20
IEEE 802.16e
MAN
IEEE 802.16d
WiMAX
IEEE 802.11
Wi-Fi
IEEE 802.15
Bluetooth
LAN
PAN
Image courtesy: Google
Wireless LANs: WiFi/802.11
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Based on the IEEE 802.11a/b/g/n family of standards
Designed to provide in-building or campus broadband coverage.
– IEEE 802.11b peak physical layer data rate of 11 Mbps
– IEEE 802.11a/g peak physical layer data rate of 54 Mbps and
indoor coverage over a distance of 100 feet.
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Much higher peak data rates than 3G systems, primarily since it
operates over a larger bandwidth (20 MHz).
– Its MAC scheme CSMA (Carrier Sense Multiple Access) is
inefficient for large numbers of users
– The interference constraints of operating in the license-exempt
band is likely to significantly reduce the actual capacity of
outdoor Wi-Fi systems.
– Wi-Fi systems are not designed to support high-speed mobility
WPAN (Wireless Personal Area Network)
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Cable replacement RF technology (low cost)
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Short range {10m (1mW), 100m (100 mW)}
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– Lower power than WiFi
Widely supported by telecommunications, PC,
and consumer electronics companies.
– Hands free phone (ear set) for cars, internet
chat/VoIP
– Intra-car networking announced by some car
manufacturers in Europe
IEEE 802.15 includes seven task groups…
– Numbered from 1 – 7 with each of them having own
responsibility
Image courtesy: Google
WPAN (Wireless Personal Area Network)
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IEEE 802.15.1
– WPAN/Bluetooth standard: includes MAC and PHY spec.
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IEEE 802.15.2
– Addresses the issue of coexistence of WPAN with other wireless devices such as
WLAN
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IEEE 802.15.3
– MAC and PHY standard for high rate WPANs
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IEEE 802.15.4
– MAC and PHY standard for low rate but high endurance (power-aware)
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IEEE 802.15.5
– Mesh networking standards for WPAN devices
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IEEE 802.15.6
– Body area network standard (low power, low frequency), can be helpful in health
monitoring
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IEEE 802.15.7
– Very recently started..still working
– PHY and MAC standard for visible light communications
WiMAX: worldwide interoperability of microwave access
WiFi
WiFi
WiFi
Urban
DSL/T1
Replacement
WiFi
WiFi
WiFi
WiFi
Rural
Rural
Rural
Broadband
Rural
Image courtesy: Google
WiMAX Fixed and Mobile
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WiMAX Fixed / Nomadic
– 802.16d or 802.16-2004
– Usage: Backhaul, Wireless DSL
– Devices: outdoor and indoor
installed CPE
– Frequencies: 2.5GHz, 3.5GHz
and 5.8GHz (Licensed and LE)
– Description: wireless connections
to homes, businesses, and other
WiMAX or cellular network towers
WiMAX Mobile
– 802.16e
– Usage: Long-distance mobile
wireless broadband
– Devices: PC Cards, Notebooks
and future handsets
– Frequencies: 2.5GHz
– Description: Wireless connections
to laptops, PDAs and handsets
when outside of Wi-Fi hotspot
coverage
Image courtesy: Google
Wide Area: Satellite Systems
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Cover very large areas
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Different orbit heights
– Low Earth Orbit (LEO): ~1000 miles
– Mid Earth Orbit (MEO): ~6000 miles
– Geosynchronous Orbit (GEO): ~22,300 miles
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Optimized for one-way transmission
location positioning, GPS systems, Satellite Radio
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Most two-way systems struggling or bankrupt
Ad hoc Networks
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All the wireless networks mentioned so far are known as
infrastructure network
– Require initial setup
– Radios mostly follow master/slave concept
– Base stations act as master while user devices are controlled by BS
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Infrastructure networks are not appropriate in
– emergency situations like natural disasters or
– military conflicts or
– in areas where access is difficult
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Ad hoc networks are particularly suitable in such scenarios
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Decentralized
Peer-to-peer
Does not depend on a central entity
Minimal configuration and quick deployment
Ad-Hoc/Mesh Networks
Wireless Ad hoc networks
1. Mobile ad hoc networks
2. Wireless mesh networks
3. Wireless sensor networks
Wireless mesh network
Mobile ad hoc network
Image courtesy: Google
Wireless Sensor Networks
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Particularly useful for sensing and Event detection
Battlefield surveillance
Security surveillance
Sensor Nodes
• Low power, Small size
Image courtesy: Google
Wireless Sensor Network Classification
Infrastructured
•In buildings
• Secured places
Infrastructure-less
•No human intervention
• Not replaceable
• One time deployment
• Finite energy available with sensor nodes
Image courtesy: Google
Wireless
Technical Challenges & Basic Concepts
Challenge 1: Unreliable and Unpredictable Wireless Coverage
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Wireless channel “feels” very different from a wired channel.
– Wireless links are not reliable: they may vary over time and space
– Noise adds on to the signal
– Signal strength falls off rapidly with distance
– Signal strength may weaken due to obstacles
– Medium “air” shared among many users
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Results:
– Capacity is shared with others
– Variable capacity
– Unreliable channel: errors, outages
– Variable delays
Challenge 2: “Open” Wireless Medium
 Wireless interference
S1
R1
S2
R1
Challenge 2: “Open” Wireless Medium
 Wireless interference
S1
R1
S2
R1
 Hidden terminals
S1
R1
S2
Challenge 2: “Open” Wireless Medium
 Wireless interference
S1
R1
S2
R1
 Hidden terminals
S1
R1
S2
 Exposed terminal
R1
S1
S2
R2
Challenge 2: Open Wireless Medium
 Wireless security
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eavesdropping
jamming
denial of service
and many more…
Challenge 3: Mobility
 Mobility causes poor-quality wireless links
 Mobility causes intermittent connection
– under intermittent connected networks, traditional routing,
TCP, applications all break
 Mobility changes context, e.g., location
Challenge 4: Portability: Energy-Constrained Nodes
 Limited battery power
 Limited processing, display and storage
 Each node can only send a finite number of bits.
– Transmit energy minimized by maximizing bit time
– Introduces a delay versus energy tradeoff for each bit
 Short-range networks must consider transmit and
processing energy
– Sophisticated techniques not necessarily energy-efficient
– Sleep modes save energy but complicate networking
 Changes everything about the network design:
– Delay vs. throughput vs. node/network lifetime tradeoffs.
– Optimization of node cooperation.
Challenge 5: Crowded Spectrum: FCC Chart
http://www.ntia.doc.gov/osmhome/allochrt.pdf
 The field is challenging
 With new wireless technologies and with more
sophistication, there are additional challenges…
– Operational
– Security
– Efficiency and more
 This course is all about
– learning current and new wireless technologies
– Understanding the challenges
– Design + Implement new mechanisms to counteract
against the challenges and make wireless networking
more efficient