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
1,800,000
1,600,000
1,400,000
1,200,000
ROW
Japan
Asia Pacific
Latin America
Western Europe
North America
1,000,000
800,000
600,000
400,000
200,000
0
2000 2001 2002 2003 2004
2005
SOURCE: CTIA, iGillottResearch, 2001
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Electromagnetic Spectrum
SOUND
RADIO
VHF = VERY HIGH FREQUENCY
UHF = ULTRA HIGH FREQUENCY
SHF = SUPER HIGH FREQUENCY
EHF = EXTRA HIGH FREQUENCY
LIGHT
HARMFUL RADIATION
3G CELLULAR
1.5-5.2 GHz
1G, 2G CELLULAR
0.4-1.5GHz
4G CELLULAR
56-100 GHz
UWB
3.1-10.6 GHz
SOURCE: JSC.MIL
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
MARITIME MOBILE
FIXED
BROADCAST
MOBILE
AERO
RADIOLOCATION
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Wireless Telephony
AIR LINK
WIRED
PUBLIC SWITCHED
TELEPHONE NETWORK
SOURCE: IEC.ORG
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Cell Clusters
ACTUAL COVERAGE
AREA OF CELL 3
CELL 1 OVERLAPS 6 OTHERS
DIFFERENT FREQUENCIES
MUST BE USED IN ADJACENT
CELLS
SEVEN DIFFERENT SETS OF
FREQUENCIES REQUIRED
ACTUAL COVERAGE
AREA OF CELL 1
SOURCE: IEC.ORG
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Space Division Multiple Access (SDMA)
MANY CELLS CAN SHARE
SAME FREQUENCIES IF
SEPARATED IN SPACE
PATTERN CAN BE
REPLICATED OVER
THE ENTIRE EARTH
200 FREQUENCIES
IN ONE CELL
TOTAL NUM BER OF
FREQUENCIES = 1400
WORLDWIDE
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Cell Handover
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
performance
contour
A
x
y
B
z
Handover threshold
contour
ANIMATION
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
SOURCE: R. C. LEVINE, SMU
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Cell Sizes
GSM:
100m - 50 km
250 km/hr
MACROCELL: $1M
FAST-MOVING
SUBSCRIBERS
PICOCELLS
MICROCELL: $250K
SLOW-MOVING
SUBSCRIBERS
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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”
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Frequency Division Multiplexing (FDMA)
Each channel gets a band (range) of frequencies
Used in traditional radio, TV, 1G cellular
Advantages:
• No dynamic coordination
Disadvantages:
• Inflexible & inefficient if
channel load is dynamic
and uneven
k1
k2
k3
k4
k5
k6
c
f
EACH CHANNEL
OCCUPIES SAME
FREQUENCY
AT ALL TIMES
t
SOURCE: NORMAN SADEH
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Time Division Multiplexing (TDMA)
Each channel gets entire spectrum for a certain (rotating)
time period
k1
c
k2
k3
k4
k5
k6
FREQUENCY BAND
f
t
Advantage: Can assign more time to senders with heavier loads
3X capacity of FDMA, 1/3 of power consumption
Disadvantage: Requires precise synchronization
SOURCE: NORMAN SADEH
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Combining TDMA and FDMA
Each channel gets a certain frequency band for a certain
amount of time. Example: GSM
Advantages:
• More robust against frequencyselective interference
• Much greater capacity with
time compression
• Inherent tapping protection
Disadvantages
• Frequency
changes must
be coordinated
k1
k2
k3
k4
k5
k6
c
f
t
SOURCE: NORMAN SADEH
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Time-Division Multiple Access
SOURCE: QUALCOMM
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Code Division Multiplexing (CDMA)
• Each channel has unique
k1
k2
“code”
• All channels use same spectrum
at 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
t
• Implemented using spread spectrum
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
k3
k4
k5
k6
c
f
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
CELL TRANSMITTER
& RECEIVER
GSM Architecture
INTERFACE TO LAND
TELEPHONE NETWORKS
HIERARCHY
OF CELLS
DATA RATE: 9.6 Kbps
PHONE
STOLEN, BROKEN
CELLPHONE LIST
ENCRYPTION,
AUTHENTICATION
SIM:
IDENTIFIES A
SUBSCRIBER
LIST OF
ROAMING
VISITORS
LIST OF SUBSCRIBERS
IN THIS AREA
SOURCE: UWC
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
SMS – Short Message Service
• Integral part of GSM standard
– Added to other standards as well
Technology
Message
Length
2
way?
GSM
160 bytes
Yes
TDMA/PDC
160 bytes
No
CDMA
256 bytes
Yes
iDEN
140 bytes
Yes
• 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!
– 3125551234@wireless.att.net
• 1 BILLION SMS/day worldwide
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
SOURCE: GEMBROOK SYSTEMS
COPYRIGHT © 2003 MICHAEL I. SHAMOS
SMS in Banking
Bank Web Site
Customer
Alert me to all credit
card transactions
greater than $100.
Message from YourBank: Credit card
purchase of $1245 at Joe’s HiFi.
Internet
SMS
Monitoring
Application
Bank
Back-end
Systems
Air
Message appears within seconds
on the customer’s phone
Wireless
Carrier
SMS
Carrier
Credit card used
Joe’s HiFi
$1245
Cell Tower
SOURCE: GEMBROOK SYSTEMS
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Satellite Systems
GEO
GEO (22,300 mi., equatorial)
high bandwidth, power, latency
M EO
MEO
high bandwidth, power, latency
LEO
LEO (400 mi.)
low power, latency
more satellites
small footprint
V-SAT (Very Small Aperture)
private WAN
SATELLITE MAP
SOURCE: WASHINGTON UNIV.
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Geostationary Orbit
SOURCE: BILL LUTHER, FCC
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
GPS Trilateration
DISTANCE MEASUREMENTS
MUST BE VERY PRECISE
LIGHT TRAVELS 1018 FEET
EACH MICROSECOND
SOURCE: PETER DANA
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Automatic Vehicle Location (AVL)
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 demo
CA
SOURCE: TRIMBLE NAVIGATION
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Location-Aware Applications
•
•
•
•
•
•
•
•
•
Vehicle tracking
Firemen in buildings, vital signs, oxygen remaining
Asset tracking
Baggage
Shoppers assistance
Robots
Corporate visitors
Insurance
Barges
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Wireless LAN Components
WaveLAN ISA
(Industry Standard
Architecture) Card
Extended
Range
Antenna
WavePOINT II
Transmitter
Ethernet
Converter
11 Mbps WaveLAN
PCMCIA Card
SOURCE: LUCENT
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Wireless LAN Configurations
CLIENT AND ACCESS POINT
WIRELESS PEER-TO-PEER
BRIDGING WITH
DIRECTIONAL ANTENNAS
MULTIPLE ACCESS POINTS + ROAMING
UP TO 17 KM !
SOURCE: PROXIM.COM
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Bluetooth Devices
ALCATEL
One TouchTM 700
GPRS, WAP
ERICSSON R520
GSM 900/1800/1900
NOKIA 9110 + FUJI
DIGITAL CAMERA
20-751 ECOMMERCE TECHNOLOGY
ERICSSON
BLUETOOTH
CELLPHONE
HEADSET
ERICSSON
COMMUNICATOR
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Bluetooth Scatternets
Scatternet
Piconets
Master
Master / Slave
Slave
Piconet
ScatterNet
SOURCE: KRISHNA BHOUTIKA
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Time-Modulated Ultra-Wideband (TM-UWB)
• Not a sinewave,
but millions of
pulses per second
500 ps
Spread Spectrum
20-751 ECOMMERCE TECHNOLOGY
0
-40
Time
“0” “1”
• Pulse position
modulation
Frequency (GHz)
Power Spectral Density (dB)
• Time coded to
make noise-like
signal
Amplitude
Randomized Time Coding
-80
Random noise signal
1
2
3
4
5
Frequency (GHz)
d d
d = 125 ps
FALL 2003
SOURCE: TIME DOMAIN
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
PulsON,
A Chip Based Solution
• Secure
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
WAP Applications
Internet
Web Content
Server
Non Mobile
Internet User
WAP Gateway
Mobile
Terminal
iNexware
Mobile
Network
WAP simulator
20-751 ECOMMERCE TECHNOLOGY
Database
Server
SOURCE: DANET
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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:
iMode FAQ
SOURCE: EUROTECHNOLOGY JAPAN K.K.
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
iMode Operation
INFO
PROVIDER
HTTP
INTERNET
IP
iMode
Servers
BILLING
DB
USER
DB
DoCoMo
Packet
Network
PACKET DATA
(PDC-P)
IP
SOURCE: SAITO & SHIN
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
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
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Q&A
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Code Division
DATA
1
0
“CODE”
0
1
0
1
0
0
1
0
DATA
 CODE
1
0
1
0
1
1
1
0
0
1
0
1
0
1
1
0
0
1
1
0 0
1
0
0
0
1
1
0
0
+1
ACTUAL
SIGNAL
-1
SOURCE: JOCHEN SCHILLER
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Code Division
DATA B
1
0
“CODE” B
0
0
0
1
1
0
1
0
DATA
 CODE
1
1
1
0
0
1
1
0
ACTUAL
SIGNAL
B
1
0
0
0
0
0
1
0
1
1
1
1 0
0
0
0
1
0
1
1
1
+1
-1
SOURCE: JOCHEN SCHILLER
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Two CDMA Signals
ACTUAL
SIGNAL
A
ACTUAL
SIGNAL
B
+1
-1
+1
-1
+2
ACTUAL
SIGNAL
A+B
-2
SOURCE: JOCHEN SCHILLER
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS
Recovering Data A From A+B
ACTUAL
SIGNAL
A+B
“CODE” A
+2
-2
+1
0
1
0
1
0
0
1
0
0
0
1
0
1
1
0
0
1
1
-1
+2
-(A+B) *
CODE A
-2
0
INTEGRAL
1
1
SOURCE: JOCHEN SCHILLER
20-751 ECOMMERCE TECHNOLOGY
FALL 2003
COPYRIGHT © 2003 MICHAEL I. SHAMOS