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Challenges in Mobile & Wireless Systems

Challenges in Mobile & Wireless Systems. EE233C (Spring 2000): Lecture #1 April 6, 2000. Welcome to EE233C!. Course logistics Overview of mobile and wireless systems Course plan. Course Logistics: Instructor Info. Email: mbs@ee.ucla.edu Phone: 310-267-2098 Office: 7702-B BH

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Challenges in Mobile & Wireless Systems

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  1. Challenges in Mobile & Wireless Systems EE233C (Spring 2000): Lecture #1April 6, 2000

  2. Welcome to EE233C! • Course logistics • Overview of mobile and wireless systems • Course plan

  3. Course Logistics: Instructor Info • Email: mbs@ee.ucla.edu • Phone: 310-267-2098 • Office: 7702-B BH • Office hours: Fr 10-12 AM, or by appointment • Assistant: Celina Liebmann, 7440D BH celina@ea.ucla.edu

  4. Course Logistics: Prerequisites • No formal prerequisite • Knowledge of computer networking and digital communications at advanced undergraduate level • Part of EE’s Computer Engineering / Embedded Computing Ad Hoc Major Field

  5. Course Logistics: Grading • One examination: 20% • around 7th week • Two home works: 20% • problem solving, analysis, theoretical, simulation • One paper review presentation: 15% • one paper per student from a specified set • 20 minute presentation • Class project: 25% results, 10% report, 5% presentation • up to groups of two students • presentation during last week & final exam slot • like a conference paper and talk • Class participation/attendance: 5% • This is a graduate course – so focus on learning!

  6. Course Logistics: Project • Dig deep into a focus area on your own • lectures would provide a “broad” coverage • Should have some new idea/result, even if minor • one or more of simulation, analysis, implementation • no paper reviews and surveys • Project proposal due by end of week 3 • project web page will have suggested project topics • may relate to your own research or job • but you cannot “reuse” work already done • What should be your goal? • something useful • similar quality as a conference paper and talk • key is to keep the project simple, and focussed

  7. Course Logistics: On the Web • Course web site URL http://www.ee.ucla.edu/~mbs/courses/ee233c/2000s • On-line material • lecture viewgraphs in PDF & PPT • check before class, and print them • copies of handouts, home works, exams etc. • important announcements • on-line reader with pointers to URLs, Melvyl • Important: please fill the on-line questionnaire! • class mailing list

  8. Course Logistics: Reader & Textbooks • No books are required. • A set of papers will be required reading • average of 1-2 paper per lecture • will relate to the core topic of that lecture • you should read them before the lecture • In addition, every student will present one paper • cover alternate ideas or related topics • selected from a set of papers of my choosing

  9. Course Logistics: Reader & Textbooks (contd.) • No paper reader - an “on-line reader” is being maintained at the course web site • bibliographic entries for various papers • links to on-line versions if available • or, indication whether available through Melvyl’s INSPEC database • hardcopies will be handed out for papers not available on-line • Typically access on-line papers from Melvyl (http://www.melvyl.ucop.edu)

  10. Course Logistics: Some Books (for your interest only…) • Wireless Communications : Principles And Practice; Rappaport, Theodore S. Prince Hall Publishing; 09/1995; • Mobile Computing (Kluwer International Series in Engineering and Computer Science, No 353); Imielinski, Tomasz (Edt)/ Korth, Henry F. (Edt) Kluwer Academic Pub; 1/96; • Mobile IP : Design Principles And Practices; Perkins, Charles / Woolf, Bobby Addison Wesley; 11/1997; • Wireless Multimedia Communications : Networking Video, Voice and Data; Wesel, Ellen Kayata Addison Wesley; 12/1997; • Wireless Personal Communications; A Systems Approach; Goodman, David J. Addison Wesley; 09/1997;Principles of Mobile Communication; Stuber, Gordon L. Kluwer Academic Publishing; 6/96; • Second Generation Mobile And Wireless Technologies; Black, Uyless Prentice Hall; 09/1998;

  11. Course Logistics: Conferences and Journals • Conferences & Workshops • Main: MOBICOM • Others: SIGCOM, INFOCOM, MoMuC, ICUPC, PIMRC, WoWMoM, ICC, Globecom, Mobihoc, etc. • Journals & Magazines • Main: ACM/Baltzer WINET, ACM/Baltzer MONET, IEEE Personal Communications • Others: IEEE Trans of N/W, JSAC etc.

  12. Growth in Wireless Services • Rapid growth in cellular/PCS services over the last decade • by 2000, one in three phoned will be mobile (42% in US) • Nordic countries: 10 new mobile phones for every wired phone • 35-60% annual growth in PCS users • 600M mobile users by 2001 • $17B in PCS license auctions • Wireless data services still a small market • albeit a fast growing one • WLAN to 2.2B in 2004 • rapid growth of PDAs, laptops

  13. Wireless Data Applications: Small Market • Lack of killer application • Unsuitable terminal devices • Lack of standard air interfaces and services • Poor performance of wireless WANs • due to low bit rates, high latencies, and high error rates of existing wide-area wireless air interfaces • Business factors • high pricing and cost, lack of universal coverage • But, technology trends augur well...

  14. Favorable Technology Trends • Innovative Internet-based applications and services particularly useful to mobile users • personalized information retrieval, access to airline reservations systems, online trading • Novel handheld terminal devices e.g. PalmPilot • compact size, low power, ease of use • next generation will have built-in wireless interfaces • Emerging wide-area wireless packet data services • aggregate data rates of several 100 kbps • TCP/IP-friendly link layer protocols

  15. Evolution in Information Systems • Wired  wireless, e.g. wired phones  cellular • more freedom of location and time • Voice telephony, data  multimedia • Intelligent telecom n/w  networked computing • intelligence at the edges of the network • programmable servers intermixed with switching infrastructure for rapid service deployment • Networked computing is becoming pervasive • personal  networked  mobile  pervasive • more flexible resource usage, more freedom of location and time, more efficient flow of information • Moving beyond phones and PCs • embedded devices & sensor-based smart spaces

  16. Core Network becoming IP-based • The dramatic rise of Internet/WWW means majority of traffic is IP packet data • Data traffic exceeding voice • Pervasive IP access • IP dial-tone • single core network for wireless access, internet access, and voice access • e.g. Sprint’s ION, MCI/Worldcom’s On-net, Qwest

  17. WWW + Mobile Telephony = Mobile Access to Information Mobile Telephone Users Internet Users

  18. PDA PCS Qualcomm PDQ Phone Novel Wireless Terminals

  19. Novel Wireless Terminals

  20. Network Infrastructure • Dynamic, programmatic creation/composition of scalable, highly available & customizable services • automatic adaptation to end device characteristics and network connectivity • dynamic composition of component services • Diverse appliances beyond the phone and the PC • devices plus servers in the infrastructure • Arbitrarily powerful services on arbitrarily small clients using an adaptive infrastructure • computing resources mixed with switching fabric • WAP: wireless application protocol

  21. Proxy-based Services

  22. Your PDA connects to the local infrastructure and asks it to build a custom GUI • Next, your PDA asks the infrastructure for a path out to your personal information space, where agents are processing your e-mail, v-mail, faxes, and pages You have complete, secure, optimized access to local devices and your private resources Project @ Berkeley: Imagine… • You walk into a room

  23. Universal In-box Transparent Information Access: a Killer Application? Speech-to-Text Speech-to-Voice Attached-Email Call-to-Pager/Email Notification Email-to-Speech All compositions of the above! Policy-based Location-based Activity-based

  24. What is this course about? • Mobile and wireless networked computing and communication systems • Emphasis on emerging systems • beyond traditional cellular telephone systems • wireless packet-switched data and multimedia • beyond network of phones and PCs • networks of large # of wireless embedded systems • Emphasis on higher layers of the system • not about radio design or communication theory • link/network/transport, application, OS/middleware • optimizations across layers

  25. Evolution of Mobile and RF Wireless Systems • 1st generation: analog - voice • AMPS with manual roaming • cordless phones • packet radio • 2nd generation: digital - voice, data • cellular & PCS with seamless roaming and integrated paging (IS-95, IS-136, GSM) • multizone digital cordless • wireless LANs (802.11), MANs (Metricom), and WANs (CDPD, Ardis, RAM, Mobitext)

  26. Beyond the 2nd Generation • Wide-area mobile voice/data • 2.5G: GPRS • 3G standards: UMTS,/IMT2000, wideband CDMA, CDMA2000, EDGE • Fixed Point-to-multipoint broadband wireless access 802.16 • LMDS (local multipoint distribution) 24-28GHz • MMDS below 5 GHz • Free space optics (Terabeam) • Higher-speed WLAN • 802.11b (2.4GHz, 11 Mbps), 802.11a (5GHz, 54 Mbps) • HomeRF • Personal area Networks • Bluetooth, 802.15 • Wireless device networks • Sensor networks, wirelessly networked robots

  27. Example: Sensor-Enhanced Gadgets • ADXL202 • Dual Axis, ±2g • 2.7V-5.25V Single Supply • 1000g Shock Survival • $40 • SmartQuill (by British Telecom) • http://www.innovate.bt.com/showcase/smartquill/index.htm • ADXL 202 monitors movement using ‘spatial sensing’ • Password by signature recognition

  28. Example: MIT’s “Expressive Footwear” • Dance shoes with wireless link & a suite of sensors • measure dynamic parameters at a dancer's foot • differential pressure at 3 points and bend in the sole, 2-axis tilt, 3-axis shock, height off the stage, orientation, angular rate and translational position) • example use: generate accompanying music

  29. Telecom View of theFuture Information Systems People and their machines should be able to access information and communicate with each other easily and securely, in any medium or combination of media - voice, data, image, video, or multimedia - anytime, anywhere, in a timely, cost-effective way. George Heilmeier (CEO of Bellcore)IEEE Communication Magazine, 1992

  30. Computing View of theFuture Information Systems The most profound technologies are those that disappear. They weave themselves into the fabric of everyday life until they are indistinguishable from it... the idea of a “personal computer” itself is misplaced... the vision of laptop machines, dynabooks and “knowledge navigators” is only a transitional step... a new way of thinking about computers, one that takes into account the human world and allows the computers themselves to vanish into the background. Mark Weiser (Chief Technologist, Xerox PARC)Scientific American, September1991

  31. Alternate Models of Mobile Computing Systems • Ubiquitous Information Access • information distributed everywhere by the “net” • terminal centric • users carry wireless terminals • terminal is the universal service access device • terminal adapts to location and services • Ubiquitous Computing • cheap computers of different scales and types embedded everywhere • 100s of computer in every room in the form of common, day-to-day objects • user centric • computers swapped among users • computers dedicated to service • computers adapt to location and users

  32. Novel Attributes of Mobile and Wireless Systems • Wireless • limited bandwidth • high latency • < 3 ms indoor • > 100 ms outdoor (cellular, satellite) • variable link quality • noise, disconnections, interference • link asymmetry • heterogeneous air interfaces • easier snooping • Mobility • Portability More Signal Processing

  33. Novel Attributes of Mobile and Wireless Systems • Wireless • Mobility • user and terminal location • are system variables of interest • change dynamically • speed of terminal mobility impactswireless bandwidth • constants become variable • location, environment, connectivity, b/w,I/O devices, security domain • easier spoofing • Portability More Protocol Processing

  34. Novel Attributes of Mobile and Wireless Systems • Wireless • Mobility • Portability • limited battery capacity • limited computing • limited storage • small dimensions • risk to data (easily lost) More Energy Efficiency

  35. Disconnections • Planned vs. unplanned • Choices? • engineer to prevent disconnections • gracefully cope (adapt) to disconnections • Mask disconnections and round-trip latencies • decouple communication from data production/consumption • asynchronous operation (multiple REQs before ACKs), prefetching, delayed write-back etc. • Tolerate by autonomous operation, caching/hoarding, local applications etc. • disconnected filesystems, e.g. CMU’s CODA • Good user interfaces to give feedback about disconnection

  36. Limited Bandwidth • Difference between indoor (1-10Mbps) and outdoor (10s of Kbps) • mobility, multipath • Right metric? • bps vs. bps per user vs. bps per unit volume • Cope by improving bandwidth usage • compression, buffering • techniques for disconnection (caching, delayed write-back) help • Schedule link bandwidth to improve user satisfaction • differentiate data according to quality of service • fair allocation of bandwidth

  37. Bandwidth Variability • Variations due to change of network • ethernet vs. wavelan vs. CDPD • Variations due to changing wireless link condition • fading • How can applications cope? • operate only when all bandwidth available • design for worst case minimum bandwidth • adapt to available bandwidth • appropriate scheduling of packets on the link

  38. Time Varying Wireless Environment • Wired networks • problem is congestion… need to share resources • resource reservation + scheduling can provide QoS • Wireless networks • sharing is only part of the problem • available wireless link resource undergoes dramatic and rapid changes • multipath reflection, doppler fading, frequency collisions • rapid signal fades and distortions as a receiver moves • necessitates aggressive signal processing and adaptive protocols

  39. Satellite Regional Area Low-tier High-tier Local Area Wide Area Low Mobility High Mobility Heterogeneous Networks • Seamless mobility across diverse overlay networks • “vertical” hand-offs • software “agents” for heterogeneity management • IP as the common denominator?

  40. Address Migration due to Mobility • Dynamically changing network access point • In current internet (and PSTN) address corresponds to the point of attachment to n/w • applications/calls connect to a fixed address • active connections cannot be moved to new address • How to support changing network access point? • How to find the current address? • How to do rerouting? • How to do route optimization? • How to do multicast?

  41. Location-dependent Information • Location affects configuration parameters • DNS, timezone, printer etc. • Location affects answer to user queries • e.g. where is the nearest printer • More complex location-dependent queries • e.g. where is the nearest taxi • Privacy concerns due to location tracking • Changing context • small movements may cause large changes • caching may become ineffective • dynamic transfer to nearest server for a service

  42. Portability • Power is key • long mean-time-to-recharge, small weight, volume • Risk to data due to easier privacy breach • network integrated terminals with no local storage • Small user interfaces • small displays, analog inputs (speech, handwriting) instead of buttons and keyboards • Small storage capacity • data compression, network storage, compressed virtual memory, compact scripts vs. compiled code

  43. Low Power • Battery technology is a hurdle… no Moore’s Law to help out • Typical laptop: 30% display, 30% CPU, 30% rest • wireless communication and multimedia processing incur significant power overhead • Low power techniques • circuits, power management, architectures, protocols • Battery model

  44. Battery Technology • Battery technology has historically improved at a very slow pace • NiCd improved by x2 over 30 years! • require breakthroughs in chemistry

  45. Summary: Challenges in Mobile and Wireless Computing • Portable, energy-efficient devices • End-to-end quality of service • Seamless operation under context changes • Context-aware operation • Secure operation • Sophisticated services for simple clients

  46. Application & Services OS & Middleware Network Data Link Radio, IR Generic Mobile and Wireless System Architecture Partitioning Source coding, DSP Context adaptation Disconnection managementPower managementQoS management This Course ReroutingImpact on TCPLocation tracking Multiple accessLink error controlChannel allocation Wireless channel models Channel coding RF circuits, Radio modems Antennas

  47. Goal for This Course Explain the impact of Mobility, Wireless, and Energy Efficiency on Link, Network, OS, and Application Layers in End-point, Network Infrastructure, and Services for Multimedia-oriented Mobile Information Systems and Emerging Networked Wireless Embedded Systems.

  48. Course Plan: Topics • Quick overview of physical layer concepts (radio propagation, wireless channel, antennas) • Software radios • Link layer protocols, medium access, adaptivity, packet scheduling • Cellular system concepts (frequency reuse, channel allocation, handoff), 3G • Mobile-IP, wireless TCP, QoS in mobile networks

  49. Course Plan: Topics (contd.) • Sensor network protocols and algorithms • Low-power portable nodes, power management, battery models • OS & middleware: database, file systems, application structure • Other emerging topics as time permits

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