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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. CSc 82020 Wireless Networking and Mobile Computing. What is the course about?. Wireless networking and mobile computing In-depth coverage of the wireless technologies

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CSc 82020 Wireless Networking and Mobile Computing

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  1. Prof. Shamik Sengupta Office 4210 N ssengupta@jjay.cuny.edu http://jjcweb.jjay.cuny.edu/ssengupta/ Fall 2010 CSc 82020 Wireless Networking and Mobile Computing

  2. 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…

  3. 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: ssengupta@jjay.cuny.edu • Office Phone: 212-237-8826 • Class WWW site: http://jjcweb.jjay.cuny.edu/ssengupta/ • Blackboard online

  4. Course Material Information • No single textbook • Class notes and slides • References to current materials from journals, magazines and other websites • Few Reference Texts: • Wireless Networks by P. Nicopolitidis, M. S. Obaidat, G. I. Papadimitriou, A. S. Pomportsis. Publisher: Wiley. ISBN-10: 0470845295. ISBN-13: 978-0470845295. • Wireless Communications: Principles and Practice by Theodore S. Rappaport. Publisher: Prentice Hall; 2nd edition. ISBN-10: 0130422320. ISBN-13: 978-0130422323. • Wireless Communications & Networking by Vijay Garg. Publisher: Morgan Kaufmann; 1st edition. ISBN-10: 0123735807. ISBN-13: 978-0123735805. • Wireless Communications & Networks, 2nd edition by William Stallings. ISBN-10: 0131918354. ISBN-13: 9780131918351.

  5. 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

  6. 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

  7. Grading Information • Workload and grading: • 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

  8. 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.

  9. Questions…??

  10. Lecture 1Wireless Introduction

  11. 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

  12. 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

  13. 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

  14. Source: Pyramid Research WLAN Market: WiFi • WLAN growing exponentially • Today, NY city is totally covered by Wi-Fi hotspots Source: AirTight Networks

  15. Today, Variety of Wireless-Capable Devices But how did it all get started? Image courtesy: Google

  16. An overview of Wireless Networks

  17. 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

  18. 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 Image courtesy: Google

  19. 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

  20. 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? ***

  21. End-end resources reserved for “call” dedicated bandwidth resources: no sharing circuit-like (guaranteed) performance call setup required Circuit Switching

  22. D E Packet Switching C A 1.5 Mb/s B queue of packets waiting 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

  23. 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

  24. IEEE Wireless Standards RAN IEEE 802.22 WAN IEEE 802.20 IEEE 802.16e MAN IEEE 802.16d WiMAX LAN IEEE 802.11 Wi-Fi PAN IEEE 802.15 Bluetooth Image courtesy: Google

  25. Wireless LANs: WiFi/802.11 • Based on the IEEE 802.11a/b/g/n family of standards • Designed to provide in-building or campusbroadband 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

  26. 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 Image courtesy: Google

  27. 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

  28. 802.16e 802.16e WiMAX: worldwide interoperability of microwave access 802.16-2004 WiFi WiFi WiFi Urban DSL/T1 Replacement WiFi WiFi 802.16-2004 WiFi 802.16-2004 WiFi Rural Rural Rural Broadband Rural Image courtesy: Google

  29. 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 WiMAX Fixed and Mobile Image courtesy: Google

  30. 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

  31. 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

  32. Ad-Hoc/Mesh Networks • Wireless Ad hoc networks • Mobile ad hoc networks • Wireless mesh networks • Wireless sensor networks Wireless mesh network Mobile ad hoc network Image courtesy: Google

  33. Wireless Sensor Networks • Particularly useful for sensing and Event detection • Battlefield surveillance • Security surveillance • Sensor Nodes • Low power, Small size Image courtesy: Google

  34. 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

  35. Wireless Technical Challenges & Basic Concepts

  36. 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

  37. Challenge 2: “Open” Wireless Medium • Wireless interference S1 R1 S2 R1

  38. Challenge 2: “Open” Wireless Medium • Wireless interference • Hidden terminals S1 R1 S2 R1 S1 R1 S2

  39. Challenge 2: “Open” Wireless Medium • Wireless interference • Hidden terminals • Exposed terminal S1 R1 S2 R1 S1 R1 S2 R1 S1 S2 R2

  40. Challenge 2: Open Wireless Medium • Wireless security • eavesdropping • jamming • denial of service • and many more…

  41. 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

  42. 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.

  43. Challenge 5: Crowded Spectrum: FCC Chart http://www.ntia.doc.gov/osmhome/allochrt.pdf

  44. 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

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