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Wireless Networks

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  1. Wireless Networks Amit Jain and Petter Karal Media Tech Club Sloan School of Management May 2, 2000

  2. Mobile + Internet =

  3. The Mobile Internet mCommerce

  4. The Mobile Internet work anywhere

  5. The Mobile Internet play anywhere

  6. anytime anytime The Mobile Internet

  7. Technical workshop How wireless works Today’s different systems The future of wireless technology Business workshop Markets and players Trends Success factors Today May 9 MediaTech Wireless 101

  8. Technology enables marketing WARNING • Wireless technologies are very fancy, fun and intellectually exciting • Don’t fall into the tech trap • The business workshop is the “really” important part - this is preparation

  9. Agenda • How does it work? • Today’s systems • Wireless technologies in the near future

  10. A wireless network

  11. Connects a mobile phone... • Mobiles send and receive radio signals to base stations (called BTS) • Each BTS has a service area • Several BTS are connected to a BSC over copper, fiber or microwave links • When a mobile moves from one service area to another, a handoff occurs • BSC directs the handoff, with or without the assistance of the mobile

  12. To the rest of the world! • BSCs are connected to Mobile Switching Center (MSC) • MSC connects mobile to other phones/devices in the world • MSC maintains subscriber database for • Billing • Roaming agreements • Paging mobiles for incoming calls

  13. Talking over the air • Bandwidth is limited (and expensive) • FCC raised over $5 billion in PCS auction • UK licenses recently auctioned for $35 billion • Each operator has 5-10 MHz • Each mobile call needs ~25KHz • Frequency must be re-used • Wireless link unreliable • Severe radio propagation losses • Interference from other networks and users

  14. Air interface standards • Examples: FDMA, TDMA, CDMA • Define how the phone talks to the network • Determine how network solves the frequency reuse, reliability, and voice quality problems • Determine cost of a network and its capacity • Most phones are designed for one air interface and one frequency • Multi-mode phones work over multiple air interfaces but cost substantially more

  15. *DMA compared ! • Consider a room with many people trying to have a conversation. • If they all speak at different frequencies, FDMA • If they take turns to speak, TDMA • If they all speak together but in different language, CDMA.

  16. Spectrum is divided into channels Each call takes one channel for the entire duration of a call Geographical separation allows channels to be reused Still used in US analog systems 2 1 3 7 2 1 4 Spectrum …. 4 6 5 2 7 3 7 1 4 Frequency Division Multiple Access (FDMA)

  17. Time Division Multiple Access (TDMA) • Channels are divided into time slots • Each user gets a channel and a time slot • Uses digital modulation to improve voice quality and capacity • GSM is the leading TDMA based standard

  18. Code Division Multiple Access (CDMA) • All users use the same wide band channel • Users are separated by encryption or codes • Encryption/decryption needs huge computational power • Provides dramatically higher capacity • Well suited for transmitting packets i.e. data • Used by military since 50s, commercialized by Qualcomm in 90s

  19. Agenda • How does it work? • Today’s systems • Wireless technologies in the near future

  20. End-to-end mobile phone standards • Each standard covers air interface, mobility manage-ment, switching, inter-connectivity and other issues • AMPS : Advanced Mobile Phone System • Established 1983 by AT&T • GSM : Global System for Mobile communications • Established 1990, Europe • Ericsson, Nokia, Omnipoint, Pacific Bell, all European carriers • cdmaOne • Established 1995 • Qualcomm, Motorola, Lucent, Sprint PCS • Others (D-AMPS, TDMA, N-TDMA, TACS, DECT...)

  21. AMPS • Still used in AT&T and AirTouch Networks in the cellular band • FDMA based air interface • Poor voice quality • Handoffs are done without the assistance of the mobile, unreliable

  22. Higher capacity (2X over AMPS) • TDMA air interface instead of FDMA • Better voice quality • Digital voice encoding/decoding • Excellent roaming • One phone, many networks • SIM cards • Painless phone upgrades

  23. Higher capacity (5X over GSM) • CDMA air interface instead of FDMA • Superior voice quality • Digital encoding/decoding • Smooth handoffs • Simpler network design

  24. 8% 11% 13% 67% GSM is predominant Total worldwide subscribers: 490 million Share of digital mobile subscriber market

  25. Agenda • How does it work? • Today’s systems • Wireless technologies in the near future

  26. The MobileInternet vision • Any application... • …on any device • …anytime • …anywhere “The Network is the Computer” - Scott McNeally

  27. 3G: High-speed multimedia internet access 2G: Digital voice+ 1G: Analog voice The third generation of wireless (3G) is coming Value to user ~1980 1990 2002 Introduction

  28. 3G adds functionality and more connectivity • Multimedia capable • Pictures • Music • Video • Internet connected • Packet-switched (144 to >2000kps) • Location sensitive

  29. Access by many different devices and technologies Access from different devices (“terminals”) at different times • Phone device • Car • PDA/palmtop computer • Desktop • Fridge?

  30. Today’s phones evolveinto funky devices

  31. 3G must overcomeseveral challenges • Standardization • Tug-of-War over technical aspects of global standards waged in many forums • Migration • Old customers, networks and frequencies can’t simply be discarded • Technology • High-speed data devours batteries, heats handsets and uses a lot of spectrum

  32. Standardization for 3G • Three coinciding technologies • DS-CDMA (UTRA FDD) • MC-CDMA • UTRA TDD • “Harmonization” - maximizing compatibility • Doesn’t matter all that much • Most consumers aren’t global • Multi-band/multi-mode phones can roam the world anyway

  33. Several step-stones for3G migration • Circuit-switched internet access • WAP (discussed later) • Upgrades to 2G (“2.5G”) • GPRS: Upgrades GSM to PS at 50-115kps • cdma2000: High-speed data over cdmaONE • Upgrades to 3G of current networks • EDGE: Upgrades GSM/GPRS and TDMA/AMPS to 3G, with data rates of 50-473kps

  34. Related technologies • Operating systems (OS) for terminals • Short-distance wireless networking • Applications and services • Security systems • Location specificity • New input/output technologies

  35. Operating systems • Battle to become the “Windows of Wireless” • Players come in at different angles • EPOC (Symbian) - the OS for the PSION PDA • Palm OS • Pocket CE - was: Windows CE, Microsoft’s “all gadgets” OS • Phone.com - WAP browser “all you need”? • Mobile Linux - no position now, but potential • Java - might make underlying OS “irrelevant”

  36. Short-distance wireless networking: • Widely adopted standard • Cheap chip that communicates via microwave radio • Enables devices within 30’ to network spontaneously (forming “Piconets”) • Speed: 1mps, allegedly bound for 10mps

  37. Many kinds ofapplications • “Hardcoded” functionality • Installed software (possible today on PDAs, Palmtops; not on cell phones) • Wireless-enabled web sites • Network applications - run them on distant servers using browser

  38. Example applications • E-mail = instant messaging • Arrival services • Device knows you and your position - offers relevant booking services for transportation, as well as for dining and entertainment • Web-based enterprise systems • Store and retrieve files, look up information and perform transactions from anywhere, anytime

  39. Security systemsenable transactions • Main focus: To enable secure transactions • Key technology: Public Key Encryption (PKI) • Many players race to define industry standard • Strong contender: Hardware-based systems (smart-cards; chips)

  40. Your service will be tailored by your location • Location tracking required by US law for 9-1-1 purposes (“e911”) • Several technologies • Analysis of signals and handoffs • GPS (not used in mobile devices yet) • Bluetooth (not sufficient for e911, though) • Current systems are not very precise; will improve

  41. New ways to operate your wireless device HYPE? • New input technologies • Palm Grafitti (has been around for a while) • Keyboard variants • Integrated camera • Speech recognition • New output technologies • New screens • Screen specs - glasses with display • Crazy stuff coming: Direct retinal projection, implants, AI, neural interfaces

  42. And the killer app is... Voice!

  43. Wireless Application Protocol, W@P • Emerging standard for presentation and delivery of data on wireless phones • Designed to work within the constraints of existing wireless and phone technology • Standard initiated by Unwired Planet, now Phone.com, with the support of Nokia, Ericsson and Motorola. • Today WAP Forum has 100+ members

  44. W@P architecture Phone MicroBrowser - WML - WMLScript - WTAI WAP Gateway - Encode Reqs - Decode Reqs - DNS - Proxy Server - Optimization Web Server WML Decks HTTP Server Content CGI Java/ASP WAP Protocols WSP/WTP/WDP Standard HTTP 1.1

  45. Why do we need W@P ? • Wireless devices are not PCs • Devices are small • Limited CPU, RAM • Support Voice, Telephony • Wireless channel is not copper or fiber • Unreliable • Low Bandwidth • High Latency • Standardization is essential for developing applications

  46. W@P protocols Micro-browser, WML, WMLScript, WTAI Security Independent of wireless standards

  47. WML: Decks and cards 1> Pizza 2> Chinese 3> Indian 1> Pepperoni 2> Meat Lovers 3> Veggie Cost: $11 Buy? 1> Kung Pao 2> Schezuan 3> Fried Rice Cost: $8 Buy? One “deck” - Web servers always send “decks” - Decks contain “cards” - Each card is ONE user interaction - Decks maintain state information Cost $9 Buy? 1> Tandoori 2> Naan Bread 3> Dosa One “card”

  48. WAP Gateway • Translates WAP requests to HTTP and TCP/IP • Encodes and decodes content to reduce size and number of over-the-air packets • Off-loads phone from computation intensive tasks • Maintains cookies / user information • Caches commonly accessed information

  49. Cellular Digital Packet Data (CDPD) • Technology currently used by Palm, RIMM • Palm.net, GoAmerica (NASDAQ:GOAM) resells service from ATT, Bell Atlantic, Ameritech • Uses a digital overlay of existing network • Data sent using TCP/IP • Maximum data rate = 19.2 kbps • Billed by the byte

  50. CDPD Network Overlay Required Uses TCP/IP Dedicated devices like Palm, wireless modem Packed-switched Charge by the byte W@P Works on existing network Own network protocol Software upgrade of phone Circuit and Packet Charge by the minute CDPD and WAP compared