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 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: ssengupta@jjay.cuny.edu 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: 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 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 Project & Presentation 40% Homework assignments 30% Midterm exam 30% No final exam Extra-credit assignments as decided by Instructor Late policy approx % 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…?? Lecture 1 Wireless 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 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] 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 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 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 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 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 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 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 Image courtesy: Google 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 WiFi WiFi WiFi Urban DSL/T1 Replacement WiFi WiFi WiFi WiFi Rural Rural Rural Broadband Rural Image courtesy: Google 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 Image courtesy: Google 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 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 • • • • 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 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 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 – – – – 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