20-751 ECOMMERCE TECHNOLOGY FALL 2003 COPYRIGHT © 2003 MICHAEL I. SHAMOS Wireless Technologies
Mar 29, 2015
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Wireless Technologies
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Outline
• Wireless technology overview• Cellular communications• Satellite systems• Wireless LAN
– 802.11, Bluetooth, UWB
• Mobility support– WAP
• Wireless applications
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Why Wireless?
• Human freedom– Portability v. Mobility
• Objective: “anything, anytime, anywhere”• Mobility
– Size, weight, power– Functionality– Content
• Infrastructure required• Cost
– Capital, operational
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Worldwide Mobile Subscribers
0
200,000
400,000
600,000
800,000
1,000,000
1,200,000
1,400,000
1,600,000
1,800,000
2000 2001 2002 2003 2004 2005
ROW
Japan
Asia Pacific
Latin America
Western Europe
North America
SOURCE: CTIA, iGillottResearch, 2001
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COPYRIGHT © 2003 MICHAEL I. SHAMOS
Electromagnetic Spectrum
SOURCE: JSC.MIL
SOUND LIGHTRADIO HARMFUL RADIATION
VHF = VERY HIGH FREQUENCYUHF = ULTRA HIGH FREQUENCYSHF = SUPER HIGH FREQUENCY EHF = EXTRA HIGH FREQUENCY
4G CELLULAR56-100 GHz
3G CELLULAR1.5-5.2 GHz
1G, 2G CELLULAR0.4-1.5GHz
UWB
3.1-10.6 GHz
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MOBILE
FIXED
MARITIME MOBILE
BROADCAST
AERO
RADIOLOCATION
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Wireless Telephony
SOURCE: IEC.ORG
AIR LINK
PUBLIC SWITCHEDTELEPHONE NETWORK
WIRED
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Cell Clusters
SOURCE: IEC.ORG
ACTUAL COVERAGEAREA OF CELL 1
ACTUAL COVERAGEAREA OF CELL 3
CELL 1 OVERLAPS 6 OTHERS
DIFFERENT FREQUENCIESMUST BE USED IN ADJACENTCELLS
SEVEN DIFFERENT SETS OFFREQUENCIES REQUIRED
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Space Division Multiple Access (SDMA)
PATTERN CAN BEREPLICATED OVERTHE ENTIRE EARTH
200 FREQUENCIESIN ONE CELL
TOTAL NUM BER OFFREQUENCIES = 1400
WORLDWIDE
MANY CELLS CAN SHARESAME FREQUENCIES IFSEPARATED IN SPACE
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Cell Handover
SOURCE: R. C. LEVINE, SMU
AS PHONE MOVES FROM CELL “A” TO CELL “B”: • CELL “A” MUST HAND THE CALL OVER TO “B” • PHONE MUST CHANGE FREQUENCIES • CELL “A” MUST STOP TRANSMITTING
Minimum performancecontour
Handover thresholdcontour
A Bx y
z
ANIMATION
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Cell Sizes
MACROCELL: $1M
MICROCELL: $250K
SLOW-MOVINGSUBSCRIBERS
FAST-MOVINGSUBSCRIBERS
PICOCELLS
GSM: 100m - 50 km 250 km/hr
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Multiple Access
• Many users sharing a resource at the “same time”• Needed because user must share cells• FDMA (frequency division)
– Use different frequencies
• TDMA (time division)– Use same frequency, different times
• CDMA (code division)– Use same frequency, same time, different “codes”
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Frequency Division Multiplexing (FDMA)
Advantages:• No dynamic coordination
Disadvantages:• Inflexible & inefficient if
channel load is dynamic and uneven
k2 k3 k4 k5 k6k1
f
t
c
Each channel gets a band (range) of frequenciesUsed in traditional radio, TV, 1G cellular
EACH CHANNELOCCUPIES SAME
FREQUENCYAT ALL TIMES
SOURCE: NORMAN SADEH
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k2 k3 k4 k5 k6k1
Time Division Multiplexing (TDMA)
Each channel gets entire spectrum for a certain (rotating) time period
Advantage: Can assign more time to senders with heavier loads 3X capacity of FDMA, 1/3 of power consumptionDisadvantage: Requires precise synchronization
SOURCE: NORMAN SADEH
f
t
c FREQUENCY BAND
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COPYRIGHT © 2003 MICHAEL I. SHAMOS
Combining TDMA and FDMA
f
t
c
k2 k3 k4 k5 k6k1
Each channel gets a certain frequency band for a certain amount of time. Example: GSM
Advantages:• More robust against frequency- selective interference• Much greater capacity with time compression• Inherent tapping protection
Disadvantages• Frequency changes must be coordinated
SOURCE: NORMAN SADEH
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COPYRIGHT © 2003 MICHAEL I. SHAMOS
Time-Division Multiple Access
SOURCE: QUALCOMM
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Code Division Multiplexing (CDMA)
• Each channel has unique“code”
• All channels use same spectrumat same time but orthogonal codes
• Advantages:– bandwidth efficient – code space is huge– no coordination or synchronization
between different channels– resists interference and tapping– 3X capacity of TDMA, 1/25 power consumption
• Disadvantages:– more complex signal regeneration
• Implemented using spread spectrum
k2 k3 k4 k5 k6k1
f
t
c
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Cellular Generations• First
– Analog, circuit-switched (AMPS)
• Second– Digital, circuit-switched (GSM, Palm) 10 Kbps
• Advanced second– Digital, circuit switched, Internet-enabled (WAP)
10 Kbps
• 2.5– Digital, packet-switched, TDMA (GPRS, EDGE)
40-400 Kbps
• Third– Digital, packet-switched, wideband CDMA (UMTS)
0.4 – 2 Mbps
• Fourth– Data rate 100 Mbps; achieves “telepresence”
20-751 ECOMMERCE TECHNOLOGY
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GSM Architecture
SOURCE: UWC
LIST OFROAMINGVISITORS
LIST OF SUBSCRIBERSIN THIS AREA
STOLEN, BROKENCELLPHONE LIST
ENCRYPTION,AUTHENTICATION
INTERFACE TO LANDTELEPHONE NETWORKS
HIERARCHYOF CELLS
CELL TRANSMITTER& RECEIVER
PHONE
SIM:IDENTIFIES ASUBSCRIBER
DATA RATE: 9.6 Kbps
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SMS – Short Message Service
• Integral part of GSM standard
– Added to other standards as well
• Uses control channel of phone
– Send/Receive short text messages
– Sender pays (if from mobile phone)
• Phone has "email" address
– SMTP Interface
• Only in the US, not the rest of the world
• Allows messages to be sent for free!
• 1 BILLION SMS/day worldwide
Technology Message Length
2 way?
GSM 160 bytes Yes
TDMA/PDC 160 bytes No
CDMA 256 bytes Yes
iDEN 140 bytes Yes
SOURCE: GEMBROOK SYSTEMS
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SMS in Banking
Credit card used
Joe’s HiFi$1245
BankBack-endSystems
Internet
Bank Web Site
Message from YourBank: Credit card
purchase of $1245 at Joe’s HiFi.
Message appears within seconds
on the customer’s phone
SMS Monitorin
g Application
Customer
Alert me to all credit
card transactions greater than
$100.
Cell Tower
Air
WirelessCarrier
SMS Carrier
SOURCE: GEMBROOK SYSTEMS
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Satellite Systems
SOURCE: WASHINGTON UNIV.
GEO
M EO
LEO
GEO (22,300 mi., equatorial) high bandwidth, power, latency
MEO high bandwidth, power, latency
LEO (400 mi.) low power, latency
more satellites
small footprint
V-SAT (Very Small Aperture)
private WAN
SATELLITE MAP
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Geostationary Orbit
SOURCE: BILL LUTHER, FCC
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GPS Satellite Constellation
• Global Positioning System• Operated by USAF• 28 satellites• 6 orbital planes at a height of 20,200 km• Positioned so a minimum of 5 satellites are visible at all times• Receiver measures distance to satellite
SOURCE: NAVSTAR
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GPS Trilateration
DISTANCE MEASUREMENTSMUST BE VERY PRECISE
LIGHT TRAVELS 1018 FEETEACH MICROSECOND
SOURCE: PETER DANA
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Automatic Vehicle Location (AVL)
SOURCE: TRIMBLE NAVIGATION
Benefits of AVL• Fast dispatch• Customer service• Safety, security• Digital messaging• Dynamic route optimization• Driver compliance
Sample AVL Users• Chicago 911• Inkombank, Moscow• Taxi companies
Intelligent Highway demoCA
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Location-Aware Applications
• Vehicle tracking• Firemen in buildings, vital signs, oxygen remaining• Asset tracking• Baggage• Shoppers assistance• Robots• Corporate visitors• Insurance• Barges
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Wireless LAN
• Idea: just a LAN, but without wires
• Not as easy since signals are of limited range– Unlike wired LAN, if A can hear B and B can hear C, not
necessarily true that A can hear C
• Uses unlicensed frequencies, low power• 802.11 from 2 Mb to 54 Mb
• Bluetooth
• UWB
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Wireless LAN Components
SOURCE: LUCENT
WavePOINT IITransmitter
ExtendedRange
Antenna
EthernetConverter
11 Mbps WaveLANPCMCIA Card
WaveLAN ISA(Industry StandardArchitecture) Card
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Wireless LAN Configurations
SOURCE: PROXIM.COM
WIRELESS PEER-TO-PEERCLIENT AND ACCESS POINT
MULTIPLE ACCESS POINTS + ROAMING
BRIDGING WITHDIRECTIONAL ANTENNAS
UP TO 17 KM !
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Bluetooth A standard permitting for wireless connection of:
• Personal computers• Printers• Mobile phones• Handsfree headsets• LCD projectors• Modems• Wireless LAN devices• Notebooks• Desktop PCs• PDAs
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Bluetooth Characteristics• Operates in the 2.4 GHz Industrial-Scientific-Medical (ISM) (unlicensed)! band. Packet switched. 1 milliwatt (as opposed to 500 mW cellphone. Low cost.
• 10m to 100m range • Uses Frequency Hop (FH) spread spectrum, which divides the frequency band into a number of hop channels. During connection, devices hop from one channel to another 1600 times per second
• Bandwidth 1-2 megabits/second• Supports up to 8 devices in a piconet (two or more Bluetooth units sharing a channel).
• Built-in security. • Non line-of-sight transmission through walls and briefcases.
• Easy integration of TCP/IP for networking.
20-751 ECOMMERCE TECHNOLOGY
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Bluetooth Devices
NOKIA 9110 + FUJIDIGITAL CAMERA
ERICSSONCOMMUNICATOR
ERICSSON R520GSM 900/1800/1900
ALCATELOne TouchTM 700
GPRS, WAPERICSSON
BLUETOOTHCELLPHONE
HEADSET
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Bluetooth Piconets
• Piconet = small area network
• “Ad hoc” network: no predefined structure
• Based on available nodes and their locations
• Formed (and changed) in real time
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Bluetooth Scatternets
Master
Slave
Piconet
ScatterNet
Master / Slave
Scatternet Piconets
SOURCE: KRISHNA BHOUTIKA
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Time-Modulated Ultra-Wideband (TM-UWB)
• Not a sinewave, but millions of pulses per second
• Time coded to make noise-likesignal
• Pulse position modulation
500 ps
Time
Randomized Time Coding
Am
plit
ude
ps
“0” “1” Pow
er S
pec
tral
Den
sity
(d
B)
-80
-40
0
Frequency (GHz)1 2 3 4 5
Frequency (GHz)
Random noise signal
SOURCE: TIME DOMAIN
Spread Spectrum
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Ultra Wideband Properties
• VERY low power: 0.01 milliwatt– Bluetooth 1 milliwatt (100 x UWB)– Cellphone 500 milliwatts (50,000 x UWB)
• Range: 30 to 300 feet• Very small • Low cost• 100 Mbits/second• Up to 500 Mbps for short distances
(USB speed)• No interference• Secure
PulsON, A Chip Based Solution
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Wireless Application Support
• WAP (Wireless Application Protocol) and iMode• High-level protocols that use cellular transport• WAP:
– Uses WML (Wireless Markup Language)– Divides content into “cards” equal to one telephone screen– Simplified but incompatible form of HTML– To send to a WAP phone, must broadcast WML content
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WAP Applications
Web ContentServer
MobileTerminal
MobileNetwork
Internet
WAP Gateway
Non Mobile Internet User
DatabaseServer
SOURCE: DANETWAP simulator
iNexware
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iMode• Telephone, pager, email, browser, location tracking,
banking, airline tickets, entertainment tickets, games• NTT DoCoMo ( ドコモ means “anywhere”) • Japan is the wireless Internet leader:
SOURCE: EUROTECHNOLOGY JAPAN K.K.
iMode FAQ
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iMode
• Sits on top of packet voice/data transport• As of July 31, 2003, > 39 million subscribers
– 28,000 new ones per day
• 26% of Japan• >3000 “official” sites• >1000 application partners• >40,000 unofficial sites• Fee based on amount
of data transmitted
SOURCES: XML.COM, EUROTECHNOLOGY.COM
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iMode
• Phonetic text input (better for Japanese)• SLOW: 9.6 Kbps, but 3G will raise to 384 K• Uses cHTML (compact HTML)
– same rendering model as HTML (whole page at a time)– low memory footprint (no tables or frames)
• Standby time: 400 min., device weight 2.4 oz. (74g)
SOURCES: XML.COM, NTT
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iMode Operation
IP
DoCoMoDoCoMoPacketPacket
Network Network (PDC-P)(PDC-P)IP
INFOPROVIDER
INTERNET
iMode Servers
BILLINGDB
USERDB
PACKET DATAHTTP
SOURCE: SAITO & SHIN
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Wireless Standards
• 802.11b (2.4 GHz 300’ radius 11 Mbps)
• 802.11a (5 GHz 54 Mbps incompatible with b)
• 802.11g (2.4 GHz 54 Mbps backward compatible with b)
• 802.20 (<3.5 GHz >1 Mbps @250 kph)
• BlueTooth (2.4 Ghz 30’ radius)
• GSM (9.6 Kbps) GPRS (28.8 Kbps up to 60 Kbps )
• 3G (UMTS 1.1 Mbit/s shared typically giving 80 Kbit/s )
• 4G 2010? (10 Mbs? )
• UWB potential to deliver 500 Mbps over short distances
SOURCE: JOHN DOWNARD
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Key Takeaways
• Mobile growing very rapidly• Cell systems need large infrastructure• Wireless LAN does not• Content preparation is a problem• Wireless business models largely unexplored• Bandwidth, bandwidth, bandwidth
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QA&
20-751 ECOMMERCE TECHNOLOGY
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Code Division
SOURCE: JOCHEN SCHILLER
1 10DATA
1 1 1 1 1 1 1 10 0 0 0 0 00000“CODE”
0 0 0 0 0 0 0 0 0 011 1 1 1111DATA CODE
+1
-1
ACTUALSIGNAL
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Code Division
SOURCE: JOCHEN SCHILLER
1 00DATA B
0 1 1 0 0 1 1 10 1 0 0 0 10100“CODE” B
1 0 0 1 0 0 0 1 1 111 0 0 1011DATA CODE
+1
-1
ACTUALSIGNAL
B
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Two CDMA Signals
SOURCE: JOCHEN SCHILLER
+1
-1
ACTUALSIGNAL
A
+1
-1
ACTUALSIGNAL
B
ACTUALSIGNAL
A+B
+2
-2
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Recovering Data A From A+B
SOURCE: JOCHEN SCHILLER
+2
-2
ACTUALSIGNAL
A+B
1 1 1 1 1 1 1 10 0 0 0 0 00000“CODE” A
+2
-2
-(A+B) *CODE A
+1
-1
INTEGRAL1
0
1