1. CS434/534: Mobile Computing and Wireless Networks http://zoo. cs. yale
Y. Richard Yang
08/29/2012

2. Outline Introduction to wireless networks and mobile computing
Challenges facing wireless networks and mobile computing
Course information
Introduction to wireless physical layer

4. 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

5. Enabling Technologies
Development and deployment of wireless/mobile technology and infrastructure
in-room, in-building, on-campus, in-the-field, MAN, WAN
Improving device capabilities/mobile applications, e.g.,
andriod:
iphone/ipad:
We are getting closer to the goal because of advances in enabling technologies.

6. Pervasive of Mobile Wireless Devices
Many industrial countries reach at least 90% mobile phone subscription penetration rate
“The mobile device will be the primary connection tool to the Internet for most people in the world in “ PEW Internet and American Life Project
Wireless coverage:

7. Internet Traffic Growth

8. At Home
WiFi
WiFi g/n
UWB
satellite
cellular
bluetooth

9. At Home
Service composition: when playing movie, send sound to stereo
When laptop is active, turn down the volume of the TV
Source:

10. At Home: Last-Mile Many users still don’t have broadband
reasons: out of service area; some consider expensive

11. Source: http://www.ece.uah.edu/~jovanov/whrms/
On the Move
Source:

12. On the Move: Context-Aware
Source:

13. On the Road ad hoc road condition, weather, location-based services,
Vehicles
transmission of news, road condition, weather, music via DAB
personal communication using GSM
position via GPS
local ad-hoc network with vehicles close-by to prevent accidents, guidance system, redundancy
vehicle data (e.g., from busses, high-speed trains) can be transmitted in advance for maintenance
Emergencies
early transmission of patient data to the hospital, current status, first diagnosis
replacement of a fixed infrastructure in case of earthquakes, hurricanes, fire etc.
crisis, war, ...
road condition,
weather,
location-based services,
emergency

14. Mobile and Wireless Services – Always Best Connected
UMTS Rel. 5
400 kbit/s
LAN
100 Mbit/s,
WLAN
54 Mbit/s
GSM 53 kbit/s
Bluetooth 500 kbit/s
LAN, WLAN
780 kbit/s
UMTS,
DECT
2 Mbit/s
GSM/EDGE 135 kbit/s,
WLAN 780 kbit/s
UMTS Rel. 6
400 kbit/s
GSM 115 kbit/s,
WLAN 11 Mbit/s

15. Example: IntelliDrive (Vehicle Infrastructure Integration)
Traffic crashes resulted in more than 41,000 lives lost/year
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:

16. Collision Avoidance : V2V Networks
bland spots
stalled vehicle warning

17. Collision Avoidance at Intersections
Two million accidents at intersections per year in US
Source:

18. Disaster Recovery/Military
9/11, Tsunami, Hurricane Katrina, South Asian earthquake …
Wireless communication and mobile computing capability can 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

19. A 15-minute human visit leads to 20% offspring mortality
Habitat Monitoring: Example on Great Duck Island
Patch
Network
Transit Network
Basestation
Gateway
A 15-minute human visit leads to 20% offspring mortality

20. Wireless and Mobile Computing
Driven by technology and vision
wireless communication technology
global infrastructure
device miniaturization
mobile computing platforms
The field is moving fast

21. Wireless and Mobile Computing
Source: O2

22. Why is the Field Challenging?

23. Challenge 1: Unreliable and Unpredictable Wireless Coverage
Wireless links are not reliable: they may vary over time and space
Reception v. Distance
Reception vs. Power
*Cerpa, Busek et. al
What Robert Poor (Ember) calls “The good, the bad and the ugly”

24. Challenge 2: Open Wireless Medium
Wireless interference S1 R1 S2 R1

25. Challenge 2: Open Wireless Medium
Wireless interference
Hidden terminals S1 R1 S2 R1 S1 R1 S2

26. Challenge 2: Open Wireless Medium
Wireless interference
Hidden terminals
Exposed terminal S1 R1 S2 R1 S1 R1 S2 R1 S1 S2 R2

27. Challenge 2: Open Wireless Medium
Wireless interference
Hidden terminals and
Exposed terminal
Wireless security
eavesdropping, denial of service, … R1 S1 S2 R1 S1 R1 R2 R1 S1 S2 R2

28. 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

29. Challenge 4: Portability
Limited battery power
Limited processing, display and storage
Smart phone
data
smaller graphical displays
802.11/3G
Sensors,
embedded
controllers
Tablet/Laptop
Mobile phones
voice, data
simple graphical displays
GSM/3G
Performance/Weight/Power Consumption

30. Challenge 5: Changing Regulation and Multiple Communication Standards

31. Challenge 5: Changing Regulation and Multiple Communication Standards
cordless phones
wireless LAN
cellular phones
satellites
1980: CT0
1981:
NMT 450
1982:
Inmarsat-A
1983:
AMPS
1984: CT1
1986:
NMT 900
1987: CT1+
1988:
Inmarsat-C
1989:
CT 2
1991:
CDMA
1991:
D-AMPS
1991:
DECT
1992:
GSM
1992:
Inmarsat-B
Inmarsat-M
199x:
proprietary
1993:
PDC
1997:
IEEE
1994: DCS 1800
1998:
Iridium
1999:
802.11b, Bluetooth
2000: GPRS
2000:
IEEE a
analogue
2001:
IMT-2000
digital
Fourth Generation
(Internet based)

32. Wireless Communication Standards

33. IMT Advanced Requirements
All-IP communications.
Peak data rates
100 Mbit/s for high mobility
1 Gbit/s for low mobility
Scalable channel bandwidth, between 5 and 20 MHz, optionally up to 40 MHz
Peak link spectral efficiency
15 bit/s/Hz (downlink); 6.75 bit/s/Hz (uplink)
System spectral efficiency
3 bit/s/Hz/cell (downlink)
2.25 bit/s/Hz/cell (indoor)

34. Wireless Bit Rates 1.2 kbps 9.6 kbps 384 kbps 2 Mbps 100 Mbps 1 Gbps
NMT 1981
GSM 1992
IMT (WCDMA; CDMA)
IMT-Advanced ~2012

35. What Will We Cover?

36. Class Info: Personnel Instructor Teaching fellow Course home page
Y. Richard Yang, AKW 308A
office hours: to be posted
Teaching fellow
Jiewen Huang, AKW
office hours: to be posted on class page
Course home page

37. Class Goals
Learn both fundamentals and applications of wireless networking and mobile computing
Obtain hands-on experience on developing on wireless, mobile devices
wireless: GNU radio
mobile computing: Android
Discuss challenges and opportunities in wireless networking and mobile computing

38. The Layered Reference Model
Application
Application
Transport
Transport
Network
Network
Network
Network
Data Link
Data Link
Data Link
Data Link
Physical
Physical
Physical
Physical
Medium
Radio
Often we need to implement a function across multiple layers.

39. Course Topic: Communications
Three topics, with ~ 4 classes each
Physical layer: channel and diversity
Link layer: channel sharing
Network and transport: routing, reliability

40. Course Topic: Basic Services
Two topics with ~2 classes each
Localization
Service and naming

41. Course Topic: Mobile App and OS
Mobile OS/application framework [2-3 classes]
TinyOS/Android
Storage/file system for mobile devices
Resource-driven dynamic adaptation
Diverse mobile hardware platforms
Mobile app design methodology and case studies

42. OS/Application Platform
Course Topics
OS/Application Platform
Communications
Locations
Security
Transport
Location
Management
Network
Localization
Data Link
Physical

43. Class Materials Chapters of reference books
Selected conference and journal papers
Other resources
MOBICOM, SIGCOMM, INFOCOM Proceedings
IEEE Network, Communications, Pervasive magazines

44. Suggested Reference Books
"Mobile Communications, Second Edition," by Jochen Schiller, Addison Wesley. 2nd Ed. August 2003.
“ Wireless Networks: the Definitive Guide” by Matthew Gast, O’Reilly, 2005 (available online)

45. Suggested Reference Books (2)
“Fundamentals of Wireless Communication”, by David Tse and Pramod Viswanath, Cambridge University Press, (available online)
"Mobile Computing Handbook," by Mohammad Ilyas and Imad Mahgoub, CRC Press, 2005.

46. What You Need to Do Your prerequisite Your workload
motivated, critical
basic programming skill
Your workload
class participation
actively participate in class discussions
one presentation at Mobile app [4-5 such classes]
3-4 assignments
One project
One midterm

47. 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 provide Android Phone/iPod touch

48. Grading More important is what you realize/learn than the grades
Project
35%
Assignments
Exam
20%
Class Participation
10%
More important is what you realize/learn than the grades

49. Class Survey Please take the class survey
help me to determine your background
help me to determine the depth and topics
suggest topics that you want to be covered

50. Questions?

51. Overview of Wireless Transmissions
source coding
bit
stream
channel coding
analog
signal
sender
modulation
receiver
bit
stream
source decoding
channel decoding
demodulation

52. Signal Signal are generated as physical representations of data
A signal is a function of time and location 1
ideal digital signal t 1 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 

53. Fundamental Question: Why Not Send Digital Signal in Wireless Communications?1
ideal digital signal t
$22 billion: Amount operators paid the U.S. government over the past ten years for spectrum. Source Burton Group.

54. ideal periodical digital signal
Fourier Transform: Every Signal Can be Decomposed as a Collection of Harmonics 1 1 t t
ideal periodical digital signal
decomposition
The more harmonics used, the smaller the approximation error.

55. Example Two representations: time domain; frequency domain
Knowing one can recover the other

57. Basic Question: Why Not Send Digital Signal in Wireless Communications?
$22 billion: Amount operators paid the U.S. government over the past ten years for spectrum. Source Burton Group. 1
digital signal t

58. Backup

59. Evolution of Mobile Systems to 3G

60. 3G Networks