1. Asstt. Professor Adeel Akram
Wireless Networks
Asstt. Professor
Adeel Akram

2. Introduction to Wireless Communication

3. Course Outline: Basic topics
Transmission Fundamentals
Analog and digital transmission
Channel capacity
Antennas, propagation modes, and fading
Signal encoding techniques
Spread spectrum technology
Coding and error control
Cellular networks
Wireless LANs
IEEE
Bluetooth

4. Course Outline: Advanced topics
Mobile IP
Multihop ad hoc networks
MAC and routing protocols
Power control and topology control
Capacity of ad hoc networks
Sensor networks
Infrastructure, MAC, and routing protocols
Synchronization Protocols
Algorithms for query processing

5. Tentative Course Schedule
Topics
Lecture Slide
Administrivia; Transmission Fundamentals: Analog & digital transmission channel capacity
WirelessNetworks1.ppt
Transmission Fundamentals: Antennas and propagation modes, fading
WirelessNetworks2.ppt
Signal encoding techniques
WirelessNetworks3.ppt
Spread spectrum: Frequency hopping, Direct sequence, and CDMA
WirelessNetworks4.ppt
Coding and error control: Error detection, error correction codes, convolution codes, and ARQ
WirelessNetworks5.ppt
Cellular wireless networks
WirelessNetworks6.ppt
Medium access control and Wireless LANs: IEEE protocol
WirelessNetworks7.ppt
Wireless LANs: Bluetooth; Mobile IP
WirelessNetworks8.ppt
Multihop ad hoc networks: Routing protocols
WirelessNetworks9.ppt
Multihop ad hoc networks: Topology and power control
WirelessNetworks10.ppt
Sensor networks: MAC and routing protocols
WirelessNetworks11.ppt
Sensor networks: synchronization protocols; algorithms for query processing Multihop ad hoc networks: Fundamental limits on capacity
WirelessNetworks12.ppt
Student presentations / Project

6. Text Books
Wireless Communications and Networks, by William Stallings, Prentice Hall, 2nd Edition, 2005
This textbook will be followed for most of the course. 
The material on multihop and sensor networks will be taken from research papers,
and other collections. 

7. Wireless Comes of Age
Guglielmo Marconi invented the wireless telegraph in 1896
Communication by encoding alphanumeric characters in analog signal
Sent telegraphic signals across the Atlantic Ocean
Communications satellites launched in 1960s
Advances in wireless technology
Radio, television, mobile telephone, communication satellites
More recently
Satellite communications, wireless networking, cellular technology, adhoc networks, sensor networks

8. Layered Architecture Scope of this course:
Application
Application
Transport
Transport
Network
Network
Network
Network
Data Link
Data Link
Data Link
Data Link
Physical
Physical
Physical
Physical
Medium
Radio
Scope of this course:
Anything above and related protocols

9. Wireless communication systems
Target information systems: “Anytime, Anywhere, Anyform”
Applications: Ubiquitous computing and information access
Market in continuous growth:
35-60% annual growth of PCS (Personal Communications Services)
Number of subscribers:
by 2001: over 700M mobile phones
by 2003: 1 billion wireless subscribers (source Ericsson)
300% growth in wireless data from
Large diversity of standards and products
Confusing terminology

10. Number of Subscribers in Hong Kong
Fixed Telephone
Mobile Phone
Broadband Internet
Will wireless Internet take off?

11. Mobile Subscribers in Pakistan
      
Customers of Mobile Service Providers in Pakistan*
 Year
Mobilink
Ufone
Paktel
Instaphone
Telenor
Warid
Total
Growth Rate
2000
114,272
80,221
112,000
306,493
15.39
2001
309,272
116,711
96,623
220,000
742,606
142.29
2002
800,000
350,000
218,536
330,000
1,698,536
128.73
2003
1,115,000
550,000
319,400
420,000
2,404,400
41.56
2004
3,215,989
801,160
470,021
535,738
5,022,908
108.90
2005
7,469,085
2,579,103
924,486
454,147
835,727
508,655
12,771,203
154.26
Jul-05
Company wise Data is updated on Quarterly Basis
14,119,257
10.56
Aug -05
15,511,045
9.7
More than 15,511,045 subscribers of Cellular Networks
*From Telecom Indicators section of PTA Website

13. Limitations and difficulties
Wireless is convenient and less expensive
Limitations and political and technical difficulties inhibit wireless technologies
Lack of an industry-wide standard
Device limitations
E.g., small LCD on a mobile telephone can only displaying a few lines of text
E.g., browsers of most mobile wireless devices use wireless markup language (WML) instead of HTML

14. Wireless around us… WLAN, DAB, GSM, etc… Personal Travel Assistant,
PDA, Laptop, GSM, cdmaOne,
WLAN, Bluetooth, ...

15. Portable Devices performance PDA simple graphical displays
character recognition
simplified WWW
Laptop
fully functional
standard applications
Mobile phones
voice, data
simple text displays
Palmtop
tiny keyboard
simple versions of standard applications
performance

16. Radio frequency spectrum
Wireless technologies have gradually migrated to higher frequencies

17. Wireless & Mobility Wireless: Mobility: Portability Limited bandwidth
Broadcast medium: requires multiple access schemes
Variable link quality (noise, interference)
High latency, higher jitter
Heterogeneous air interfaces
Security: easier snooping
Mobility:
User location may change with time
Speed of mobile impacts wireless bandwidth
Need mechanism for handoff
Security: easier spoofing
Portability
Limited battery, storage, computing, and UI

18. Challenges in Mobile Computing
Three major challenges:
Wireless Channel
Mobility
Device Limitation

19. Wireless Channel
The 1st challenge

20. Communication Channel
Transmitter
Receiver
Channel
The medium used to transmit the signal from the transmitter to the receiver
Wireline / Wireless channel

21. Wireline Channel Transmitter Wireline Channel, e.g. copper wire
Receiver
Shielded against electromagnetic noise
Too many noises?
Large signal attenuation?
Use repeaters
Upgrade to coaxial cable
Data speed too low?
Data speed still too low?
Upgrade to optical fiber

22. Fading Effect Typical Indoor Wireless Environment
Signal strength fluctuates significantly
Wireless channel cannot be engineered.
You can only improve your transmission and reception techniques.

23. Bit Error Rate Optical fiber: 10-11 or 10-12 Mobile channel:
Good quality: 10-6
Actual condition: 10-2 or worse

24. Implication
For wireline systems, it is assumed that the channel is error free
Many protocols are designed with this assumption
These protocols do not work well in a wireless environment
e.g. TCP (why?)

25. What if more than 1 transmitter?
Every user accesses the network by means of a dedicated channel
Switching Center or
Network Access Point
Dedicated Channel
New user is served by a new wire-line circuit
Access capacity is “unlimited”.

26. How about wireless networks?
Wireless users access the network by means of a shared channel
Shared Channel
Access capacity is inherently limited.
Base Station

27. Implication
For wire-line systems, we can simply install new cables to increase capacity.
For wireless systems, the channel can only be shared by the users.
Capacity does not increase.

28. Interference Multiuser Interference Self-Interference
Radio signals of different users interfere with each other
Self-Interference
Multipath effect
Phase-shifted images of the signal at the receiver interact and may cancel the entire signal, (i.e. destructive interference).

29. Interference Management
How to manage multiuser interference?
i.e. how to share the channel?
Multiple Access Problem
FDMA, TDMA, CDMA, etc.
Media Access Control
Aloha, CSMA, etc.
How to manage self-interference?
Physical layer issue
Equalization, coding, diversity, etc.
These issues will NOT be considered in this course

30. Mobility
The 2nd challenge

31. User Mobility Location Management Problem
How does the network know where the intended recipient of a message is currently located?

32. Cellular Scenario Where is 5008011?
Send broadcast messages from every base station?

33. Internet Scenario Forwarding table in router A
Dest. Net router Nhops interface A B E
Suppose A sends a datagram to E
misc
fields
data
The router sends the datagram to via interface
What happens if E moves to elsewhere?

34. Ad hoc Network ScenarioF B C M L J A G H D K I N
How to find a suitable path from source S to destination D?

35. Device Limitation
The 3rd challenge

36. Device Limitation Resource Limitation
Limited memory
Limited computational power
Small display
Limited battery life
This issue will NOT be considered at the moment but may be extended later

37. Classification of Wireless Systems
Personal communication systems
Focus on voice communication
Limited bit-rate data transmission
Large-scale mobility and coverage
Operate over licensed frequency bands
Wireless LANs
Designed for high bit-rate transmission
IP oriented
Low-scale coverage
Use unlicensed ISM frequency bands
Multihop ad hoc networks
Have little or no infrastructure
Need new routing protocols
Emerging applications

38. Transmission fundamentals
Electromagnetic signals
Time domain
Frequency domain
Data rate and bandwidth
Analog and digital data transmission
Channel capacity
Nyquist theorem [Sampling Rate >2fmax ]
Shannon capacity theorem [C≤Wlog2(1+S/N)]
Transmission media

39. Analog signaling

40. Digital signaling

42. Classification of transmission media
Transmission medium
Physical path between transmitter and receiver
Guided media
Waves are guided along a solid medium
E.g., copper twisted pair, copper coaxial cable, optical fiber
Unguided media
Provides means of transmission but does not guide electromagnetic signals
Usually referred to as wireless transmission
E.g., atmosphere, outer space

43. Unguided media
Transmission and reception are achieved by means of an antenna
Configurations for wireless transmission
Directional
Omnidirectional

44. General frequency ranges
Microwave frequency range
1 GHz to 40 GHz
Directional beams possible
Suitable for point-to-point transmission
Used for satellite communications
Radio frequency range
30 MHz to 1 GHz
Suitable for omnidirectional applications
Infrared frequency range
Roughly, 3x1011 to 2x1014 Hz
Useful in local point-to-point multipoint applications within confined areas

45. Terrestrial microwave
Description of common microwave antenna
Parabolic "dish", 3 m in diameter
Fixed rigidly and focuses a narrow beam
Achieves line-of-sight transmission to receiving antenna
Located at substantial heights above ground level
Applications
Long haul telecommunications service
Short point-to-point links between buildings

46. Microwave antenna
Parabolic “Dish”

47. Satellite microwave Description of communication satellite
Microwave relay station
Used to link two or more ground-based microwave transmitter/receivers
Receives transmissions on one frequency band (uplink), amplifies or repeats the signal, and transmits it on another frequency (downlink)
Applications
Television distribution
Long-distance telephone transmission
Private business networks

48. Broadcast radio Description of broadcast radio antennas Applications
Omni directional
Antennas not required to be dish-shaped
Antennas need not be rigidly mounted to a precise alignment
Applications
Broadcast radio
VHF and part of the UHF band; 30 MHZ to 1GHz
Covers FM radio and UHF and VHF television

49. Infrared Beyond the EHF spectrum
1012 to 1014 Hz
Transceivers must be within line of sight or reachable via reflection
Does not penetrate walls

50. Next Lecture
Antennas & Propagation Signal Encoding

51. Questions
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