Transcript Presentation

Wireless Networks
Amit Jain and Petter Karal
Media Tech Club
Sloan School of Management
May 2, 2000
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Mobile + Internet =
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The Mobile Internet
mCommerce
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The Mobile Internet
work
anywhere
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The Mobile Internet
play
anywhere
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The Mobile Internet
anytime
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MediaTech Wireless 101
Technical workshop
How wireless works
Today’s different
systems
The future of wireless
technology
Today
Business workshop
Markets and players
Trends
Success factors
May 9
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Technology enables
marketing
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
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Agenda
How does it work?
Today’s systems
Wireless technologies in the near future
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A wireless network
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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
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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
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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
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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
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*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.
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Frequency Division
Multiple Access (FDMA)
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Spectrum
 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
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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
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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
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Agenda
How does it work?
Today’s systems
Wireless technologies in the near future
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End-to-end mobile phone
standards
 Each standard covers air interface, mobility management, 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...)
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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
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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
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Higher capacity (5X over GSM)
CDMA air interface instead of FDMA
Superior voice quality
Digital encoding/decoding
Smooth handoffs
Simpler network design
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GSM is predominant
TDMA
PDC
CDMA
8%
11%
Total worldwide
subscribers:
490 million
13%
67%
GSM
Share of digital mobile subscriber market
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Agenda
How does it work?
Today’s systems
Wireless technologies in the near future
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The Mobile
Internet vision
Any application...
…on any device
…anytime
…anywhere
“The Network is
the Computer”
- Scott McNeally
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The third generation of
wireless (3G) is coming
Value to
user
3G: High-speed
multimedia
internet access
2G: Digital
voice+
1G: Analog
voice
~1980
1990
2002
Introduction
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3G adds functionality
and more connectivity
Multimedia capable
Pictures
Music
Video
Internet connected
Packet-switched
(144 to >2000kps)
Location sensitive
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Access by many different
devices and technologies
Access from different devices (“terminals”)
at different times
Phone device
Car
PDA/palmtop computer
Desktop
Fridge?
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Today’s phones evolve
into funky devices
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3G must overcome
several 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
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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
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Several step-stones for
3G 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 50473kps
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Related technologies
Operating systems (OS) for terminals
Short-distance wireless networking
Applications and services
Security systems
Location specificity
New input/output technologies
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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”35
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
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Many kinds of
applications
“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
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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
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Security systems
enable 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)
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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
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New ways to operate
your wireless device
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
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And the killer app is...
Voice!
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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
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W@P architecture
Phone
WAP
Gateway
MicroBrowser
- WML
- WMLScript
- WTAI
-
Web Server
WML
Decks
Encode Reqs
Decode Reqs
DNS
Proxy Server
Optimization
WAP Protocols
WSP/WTP/WDP
HTTP
Server
Content
CGI
Java/ASP
Standard
HTTP 1.1
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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
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W@P protocols
Micro-browser,
WML, WMLScript,
WTAI
Security
Independent of
wireless standards
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WML: Decks and cards
1> Pizza
2> Chinese
3> Indian
- Web servers always
1> Pepperoni
2> Meat Lovers
3> Veggie
Cost: $11
Buy?
1> Kung Pao
2> Schezuan
3> Fried Rice
Cost: $8
Buy?
1> Tandoori
2> Naan Bread
3> Dosa
Cost $9
Buy?
One
“deck”
send “decks”
- Decks contain “cards”
- Each card is ONE
user interaction
- Decks maintain state
information
One “card”
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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
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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
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CDPD and WAP compared
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
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i-mode
Wireless service launched in spring 1999 in
Japan by NTT DoCoMo
“3G light”
Web content based on subset of HTML
Packet-switched, multimedia enabled
Low bandwidth (9.6kps), but improved by
compression and will move to 14.2kps
Extremely successful:
6 .1M customers; growing at 200,000/week
Thousands of services provided
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Q&A
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Conclusion
The main 2G standards are GSM and CDMA
3G standards are coming that will enable
consumer multimedia internet from any
device
Many new dimensions to internet services
(context-specific, on-the-spot, continuous)
Technological feasibility drives the evolution
of the Mobile Internet (for now)
Be skeptical to hype
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Resources
3G acronym expander: www.nokia.com/3g/acronyms/0,7076,,00.html
Mobile commerce glossary: maffin.net/mobilecommerce/glossary.htm
Great news compilation on wireless: www.mobic.com
Ericsson background papers (pretty technical, but great):
www.ericsson.se/review/issues.taf
 Bluetooth homepage: www.bluetooth.com
 WAP Forum: www.wapforum.org
 Equipment providers’ homepages:
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 www.motorola.com
 www.ericsson.com
 www.nokia.com
 Web site on wireless devices: www.allnetdevices.com
 Consultancy gives “teasers” on its reports: www.ovum.com
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