CSc 82020 Wireless Networking and Mobile Computing

CSc 82020 CSc 82020 Wireless Networking and Mobile ComputingWireless Networking and Mobile Computing

Prof. Shamik Sengupta

Office 4210 N

[email protected]

http://jjcweb.jjay.cuny.edu/ssengupta/

Fall 2010

What is the course about?

Wireless networking and mobile computing

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: Learning applications, concepts, practice… Enjoy…

Timing and Contact Information

Class meeting time: Tuesday (6:30pm – 8:30pm)

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

Email: [email protected] Office Phone: 212-237-8826 Class WWW site: http://jjcweb.jjay.cuny.edu/ssengupta/ Blackboard online

Course Material Information

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: 978-0470845295.

2. Wireless Communications: Principles and Practice by Theodore S. Rappaport. Publisher: Prentice Hall; 2nd edition. ISBN-10: 0130422320. ISBN-13: 978-0130422323.

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. ISBN-10: 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

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 approx %

Project & Presentation 40%

Homework assignments 30%

Midterm exam 30%

No final exam Extra-credit assignments as decided by Instructor Late policy

Submission will not be accepted after due date Permission needed for exceptional circumstances

Attendance needed

Project & Presentation

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.)

Decide your topic as soon as possible and discuss with me. Start as early as possible.

Questions…??Questions…??

Lecture 1Lecture 1Wireless IntroductionWireless Introduction

Why Wireless?

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

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 visionWireless technologiesDevice miniaturizationMobile computing platforms

Need for ubiquitous connectivityThe 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

1023

2200

250

0

500

1000

1500

2000

2500

Internet Cell Phones Broadband

[su

bs

x000

,000

]

WLAN Market: WiFi

0

1

2

3

4

5

$-b

il

2001 2002 2003 2004 2005

Forecast Sales of Wi-Fi Equipment(Source: InfoTech Trends)

Source: Pyramid Research

Worldwide WLAN Infrastructure Shipments (Source: Gartner)

0

1

2

3

4

5

6

7

Mil

lio

ns o

f U

nit

s

Source: AirTight Networks

WLAN growing exponentiallyToday, NY city is totally covered by Wi-Fi hotspots

Today, Variety of Wireless-Capable Devices

But how did it all get started?


An overview of Wireless NetworksAn 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


Early Cellular Systems

1940s-50s: cellular concept discovered

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

1960: Improved MTS (IMTS) Automatic call switching and full duplex Supported 23 channels MTS & IMTS used high power BS and used the spectrum inefficiently


Early Cellular Systems (contd.)

Post-1960: High power BS replaced by low-power low coverage stations

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

2nd generation (2G): Digital Systems: early 90s– Represent voice signal digitally– Higher capacity– Higher speed– Reduced cost and power efficiency of digital hardware– Encryption

Early Cellular Systems (contd.)

A number of 2G systems became very popular…

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…

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

A

B

C

1.5 Mb/s

D E

queue of packetswaiting for output

link

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

Wireless Data Systems

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

ALOHANET developed at University of Hawaii, first wireless data systems, 1971

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

A wide variety of wireless data systems now exist – can be categorized based on coverage area

IEEE Wireless Standards

IEEE 802.15 Bluetooth

WAN

MAN

LAN

PAN

IEEE 802.11

Wi-Fi

IEEE 802.16d WiMAX

IEEE 802.20

IEEE 802.16e

RANIEEE 802.22


Wireless LANs: WiFi/802.11

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.

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)

Cable replacement RF technology (low cost)

Short range {10m (1mW), 100m (100 mW)}

– 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


WPAN (Wireless Personal Area Network)

IEEE 802.15.1– WPAN/Bluetooth standard: includes MAC and PHY spec.

IEEE 802.15.2– Addresses the issue of coexistence of WPAN with other wireless devices such as

WLAN IEEE 802.15.3

– MAC and PHY standard for high rate WPANs IEEE 802.15.4

– MAC and PHY standard for low rate but high endurance (power-aware) IEEE 802.15.5

– Mesh networking standards for WPAN devices IEEE 802.15.6

– Body area network standard (low power, low frequency), can be helpful in health monitoring

IEEE 802.15.7– Very recently started..still working– PHY and MAC standard for visible light communications

WiMAX: worldwide interoperability of microwave access

802.16-2004

802.16-2004

Rural

Rural

Rural

Urban

DSL/T1 Replacemen

t802.16-2004802.16-2004

WiFiWiFi

WiFiWiFi

Rural

Broadband

802.16-2004802.16-2004

WiFiWiFi

WiFiWiFi

WiFiWiFi

WiFiWiFi

WiFiWiFi

802.16e

802.16e


WiMAX Fixed and Mobile

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


Wide Area: Satellite Systems

Cover very large areas

Different orbit heights– Low Earth Orbit (LEO): ~1000 miles– Mid Earth Orbit (MEO): ~6000 miles– Geosynchronous Orbit (GEO): ~22,300 miles

Optimized for one-way transmission

location positioning, GPS systems, Satellite Radio

Most two-way systems struggling or bankrupt

Ad hoc Networks

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

Infrastructure networks are not appropriate in– emergency situations like natural disasters or

– military conflicts or

– in areas where access is difficult

Ad hoc networks are particularly suitable in such scenarios– Decentralized

– Peer-to-peer

– Does not depend on a central entity

– Minimal configuration and quick deployment

Ad-Hoc/Mesh Networks

Wireless Ad hoc networks1. Mobile ad hoc networks

2. Wireless mesh networks

3. Wireless sensor networks


Mobile ad hoc network

Wireless mesh network

Wireless Sensor Networks

• Particularly useful for sensing and Event detection• Battlefield surveillance• Security surveillance

• Sensor Nodes• Low power, Small size


Wireless Sensor Network Classification

Infrastructure-less•No human intervention• Not replaceable• One time deployment• Finite energy available with sensor nodes

Infrastructured•In buildings• Secured places


Wireless Technical Challenges & Basic Concepts

Challenge 1: Unreliable and Unpredictable Wireless Coverage

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

Results: – Capacity is shared with others– Variable capacity– Unreliable channel: errors, outages– Variable delays

Challenge 2: “Open” Wireless Medium

Wireless interference

S1

S2

R1

R1


Hidden terminals


S1

S2

R1

R1

S1 R1 S2



Hidden terminals

Exposed terminal

S1

S2

R1

R1

S1 R1 S2

R1 S1 S2 R2

Challenge 2: Open Wireless Medium

Wireless security– 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

Documents

CSc 82020 Wireless Networking and Mobile Computing