cs434/534: introduction
TRANSCRIPT
CS434/534: Mobile Computing and Wireless Networks
http://zoo.cs.yale.edu/classes/cs434/
Y. Richard Yang
01/13/2009
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Outline
Introduction to wireless networks and mobile computing
Challenges facing wireless networks and mobile computing
Course information
Introduction to wireless physical layer
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Goal of Wireless Networking and Mobile Computing
“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 – any time, anywhere, in a timely, cost-effective way.”
Dr. G. H. Heilmeier, Oct 1992
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Enabling Technologies
Development and deployment of wireless/mobile technology and infrastructure in-room, in-building, on-campus, in-the-field, MAN,
WAN Miniaturization of computing machinery . . . -> PCs -> laptop -> PDAs/smart phones ->
embedded computers/sensors Improving device capabilities/software
development environments, e.g., andriod: http://code.google.com/android/ iphone: http://developer.apple.com/iphone/ windows mobile
Pervasive Use of Mobile Wireless Devices There are ~4 billion mobile phones
Over 50 countries have mobile phone subscription penetration rates higher than that of the population (Infoma 2007)
http://en.wikipedia.org/wiki/Mobile_phone_penetration_rate
The mobile device will be the primary connection tool to the Internet for most people in the world in 2020. PEW Internet and American Life Project, Dec. 2008
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At Home
WiFi
WiFi
WiFi
cellular
bluetooth
UWB
satellite
WiFi 802.11g/n
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At Home
Source: http://teacher.scholastic.com/activities/science/wireless_interactives.htm
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At Home: Last-Mile
Many users still don’t have broadband reasons: out of service
area; some consider expensive
Broadband speed is still limited DSL: 1-6 Mbps
download, and 100-768Kbps upload
Cable modem: depends on your neighbors
Insufficient for several applications (e.g., high-quality video streaming)
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On the Move
Source: http://www.ece.uah.edu/~jovanov/whrms/
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On the Move: Context-Aware
Source: http://www.cs.cmu.edu/~aura/docdir/sensay_iswc.pdf
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ad ho
cGSM/UMTS, cdmaOne/cdma2000,WLAN, GPSDAB, TETRA, ...
road condition, weather,location-based services,emergency
On the Road
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Example: IntelliDrive (Vehicle Infrastructure Integration)
Traffic crashes resulted in more than 41,000 lives lost in 2007
Establishing vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I) and vehicle-to-hand-held-devices (V2D) communications safety: e.g., intersection collision
avoidance/violation warning/turn conflict warning, curve warning
mobility: e.g., crash data, weather/road surface data, construction zones, emergency vehicle signal pre-emption
More info: http://www.its.dot.gov/intellidrive/index.htm
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Collision Avoidance : V2V Networks
stalled vehicle warning
http://www.gm.com/company/gmability/safety/news_issues/releases/sixthsense_102405.html
bland spots
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Collision Avoidance at Intersections
Two million accidents at intersections per year in US
Source: http://www.fhwa.dot.gov/tfhrc/safety/pubs/its/ruralitsandrd/tb-intercollision.pdf
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UMTS,DECT2 Mbit/s
UMTS Rel. 6400 kbit/s
LAN100 Mbit/s,WLAN54 Mbit/s
UMTS Rel. 5400 kbit/s
GSM 115 kbit/s,WLAN 11 Mbit/s
GSM 53 kbit/sBluetooth 500 kbit/s
GSM/EDGE 135 kbit/s,WLAN 780 kbit/s
LAN, WLAN780 kbit/s
Mobile and Wireless Services – Always Best Connected
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Disaster Recovery/Military
9/11, Tsunami, Hurricane Katrina, South Asian earthquake …
Wireless communication andmobile computing capabilitycan make a difference between life and death ! rapid deployment efficient resource and energy usage flexible: unicast, broadcast, multicast,
anycast resilient: survive in unfavorable and
untrusted environments
http://www.att.com/ndr/
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Habitat Monitoring: Example on Great Duck Island
Patch Network
Transit Network
Basestation
Gateway
A 15-minute human visit leads to 20% offspring mortality
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Wireless and Mobile Computing
Driven by technology and vision wireless communication technology global infrastructure device miniaturization mobile computing platforms
The field is moving fast
Why is the Field Challenging?
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Challenge 1: Unreliable and Unpredictable Wireless Coverage
Asymmetry vs. PowerReception v. Distance
*Cerpa, Busek et. al
What Robert Poor (Ember) calls “The good, the bad and the ugly”
Wireless links are not reliable: they may vary over time and space
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Challenge 2: Open Wireless Medium
Wireless interferenceS1
S2
R1
R1
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Challenge 2: Open Wireless Medium
Wireless interference
Hidden terminals
S1
S2
R1
R1
S1 R1 S2
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Challenge 2: Open Wireless Medium
Wireless interference
Hidden terminals
Exposed terminal
S1
S2
R1
R1
S1 R1 S2
R1 S1 S2 R2
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Challenge 2: Open Wireless Medium
Wireless interference
Hidden terminals and
Exposed terminal
Wireless security eavesdropping, denial of service, …
S1
S2
R1
R1
S1 R1 R2
R1 S1 S2 R2
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Challenge 3: Mobility
Mobility causes poor-quality wireless links
Mobility causes intermittent connection under intermittent connected networks,
traditional routing, TCP, applications all break
Mobility changes context, e.g., location
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Challenge 4: Portability
Limited battery power Limited processing, display and storage
Sensors,embeddedcontrollers
Mobile phones• voice, data• simple graphical displays• GSM/3G
PDA phone• data• simpler graphical displays• 802.11/3G
Laptop• fully functional• standard applications• battery; 802.11
PPerformanceerformance/Weight/Power Consumption/Weight/Power Consumption
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Challenge 5: Changing Regulation and Multiple Communication Standards
cellular phones satellites wireless LAN
cordlessphones
1992:GSM
1994:DCS 1800
2001:IMT-2000
1987:
CT1+
1982:Inmarsat-
A
1992:Inmarsat-BInmarsat-M
1998:Iridium
1989:CT 21991:DECT 199x:
proprietary
1997:IEEE 802.11
1999:802.11b, Bluetooth
1988:Inmarsat-
C
analogue
digital
1991:D-AMPS
1991:CDMA
1981:NMT 450
1986:NMT 900
1980:
CT01984
:CT1
1983:AMPS
1993:PDC
2000:GPRS
2000:IEEE 802.11a
Fourth Generation
(Internet based)
Evolution of Mobile Systems to 3G
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3G Networks
http://en.wikipedia.org/wiki/List_of_mobile_network_operators_of_the_Americas#United_States
What Will We Cover?
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Instructor• Y. Richard Yang, [email protected], AKW 308A• office hours: to be posted
Teaching fellow• Richard Alimi, [email protected], AKW 303• office hours: to be posted on class page
Course home pagehttp://zoo.cs.yale.edu/classes/cs434/
Class Info: Personnel
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Class Goals
Learn both fundamentals and applications of wireless networking and mobile computing
Obtain hands-on experience on developing on mobile, wireless devices
Discuss challenges and opportunities in wireless networking and mobile computing
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Application
Transport
Network
Data Link
Physical
Medium
Data Link
Physical
Application
Transport
Network
Data Link
Physical
Data Link
Physical
Network Network
Radio
Often we need to implement a function across multiple layers.
The Layered Reference Model
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Course Topics
Communications: physical layer: channel and diversity link layer: MAC (sharing and power
management), reliability network layer: routing, mobility management transport over wireless
Mobile foundational services localization, security
Application developments app. adaptation to handle mobility, portability develop for heterogeneous devices
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Course Topics
Transport
Network
Data Link
Physical
Communications Locations
LocationManagement
Localization
Security
Application Development
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Class Materials
Chapters of reference books
Selected conference and journal papers
Other resources MOBICOM, SIGCOMM, INFOCOM Proceedings IEEE Network, Communications, Pervasive
magazines
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Suggested Reference Books
"Mobile Communications, Second Edition," by Jochen Schiller, Addison Wesley. 2nd Ed. August 2003.
“802.11 Wireless Networks: the Definitive Guide” by Matthew Gast, O’Reilly, 2005 (available online)
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Suggested Reference Books (2) “Fundamentals of
Wireless Communication”, by David Tse and Pramod Viswanath, Cambridge University Press, 2005. (available online)
"Mobile Computing Handbook," by Mohammad Ilyas and Imad Mahgoub, CRC Press, 2005.
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What You Need to Do
Your prerequisite motivated, critical basic programming skill
Your workload class participation
• actively participate in class discussions assignments class project exam
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Class Project
Goal: obtain hands-on experience I’ll suggest potential topics You may also choose your own topic Initial proposal + midterm progress
report + final report + [presentation] We can provide Window Mobile/Google
Andriod Dev Phone devices
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Grading
More important is what you realize/learn than the grades
Project 35%
Assignments 35%
Exam 20%
ClassParticipation
10%
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Class Survey
Please take the class surveyhelp me to determine your
background
help me to determine the depth and topics
suggest topics that you want to be covered
Questions?
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Overview of Wireless Transmissions
source decoding
bitstream
channel decoding
receiver
demodulation
source coding
bitstream
channel coding
analogsignal
sender
modulation
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Signal
Signal are generated as physical representations of data
A signal is a function of time and location
t
1
0
t
a special type of signal, sine waves, also called harmonics: s(t) = At sin(2 ft t + t)
with frequency f, period T=1/f, amplitude A, phase shift
1
0
ideal digital signal
t
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Fundamental Question: Why Not Send Digital Signal in Wireless Communications?
1
0
ideal digital signal
t
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)2cos()2sin(2
1)(
11
nftbnftactgn
nn
n
1
0
1
0
t t
ideal periodical digital signal
decomposition
Fourier Transform: Every Signal Can be Decomposed as a Collection of Harmonics
The more harmonics used, the smaller the approximation error.
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Fundamental Question: Why Not Send Digital Signal in Wireless Communications?
May cause interference suppose digital frame length T, then signal
decomposes into frequencies at 1/T, 2/T, 3/T, …
let T = 1 ms, generates radio waves at frequencies of 1 KHz, 2 KHz, 3 KHz, …
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Frequencies for Communications
VLF = Very Low Frequency UHF = Ultra High FrequencyLF = Low Frequency SHF = Super High FrequencyMF = Medium Frequency EHF = Extra High Frequency
HF = High Frequency UV = Ultraviolet LightVHF = Very High Frequency
Frequency and wave length:
= c/f
wave length , speed of light c 3x108m/s, frequency f
1 Mm300 Hz
10 km30 kHz
100 m3 MHz
1 m300 MHz
10 mm30 GHz
100 m3 THz
1 m300 THz
visible lightVLF LF MF HF VHF UHF SHF EHF infrared UV
optical transmissioncoax cabletwisted pair
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ITU-R holds auctions for new frequencies, manages frequency bands worldwide (WRC, World Radio Conferences)
Frequencies and Regulations
Europe USA Japan
Cellular Phones
GSM 450 - 457, 479 -486/460 - 467,489 -496, 890 - 915/935 -960, 1710 - 1785/1805 -1880 UMTS (FDD) 1920 -1980, 2110 - 2190 UMTS (TDD) 1900 -1920, 2020 - 2025
AMPS , TDMA , CDMA 824- 849, 869-894 TDMA , CDMA , GSM 1850 - 1910, 1930 - 1990
PDC 810- 826, 940-956, 1429 - 1465, 1477 - 1513
Cordless Phones
CT1+ 885 - 887, 930 -932 CT2 864-868 DECT 1880 - 1900
PACS 1850 - 1910, 1930 -1990 PACS -UB 1910 - 1930
PHS 1895 - 1918 JCT 254-380
Wireless LANs
IEEE 802.11 2400 - 2483 HIPERLAN 2 5150 - 5350, 5470 -5725
902-928 I EEE 802.11 2400 - 2483 5150 - 5350, 5725 - 5825
IEEE 802.11 2471 - 2497 5150 - 5250
Others RF- Control 27, 128, 418, 433,
868
RF- Control 315, 915
RF- Control 426, 868
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Spectrum and Bandwidth: Shannon Channel Capacity The maximum number of bits that can be
transmitted per second by a physical channel is:
where W is the frequency range of the channel, and S/N is the signal noise ratio, assuming Gaussian noise
)1(log2 NSW
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Objective encode digital data into analog signals at the
right frequency range with limited usage of spectrum
Modulation
Basic schemes Amplitude Modulation (AM) Frequency Modulation (FM) Phase Modulation (PM)
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Modulation of digital signals known as Shift Keying Amplitude Shift Keying (ASK):
Frequency Shift Keying (FSK):
Phase Shift Keying (PSK):
1 0 1
t
1 0 1
t
1 0 1
t
Modulation
ATT and Verizon 3G Coverage
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http://mobileroar.com/wp-content/uploads/2008/07/3g-verizon.gif