Transcript Trust, Privacy, and Security

CS 6910 – Pervasive Computing
Spring 2007
Section 1 (Ch.1):
Introduction to
Wireless and Mobile Systems
Prof. Leszek Lilien
Department of Computer Science
Western Michigan University
Slides based on publisher’s slides for 1st and 2nd edition of:
Introduction to Wireless and Mobile Systems by Agrawal & Zeng
© 2003, 2006, Dharma P. Agrawal and Qing-An Zeng. All rights reserved.
Some original slides were modified by L. Lilien, who strived to make such modifications
clearly visible. Some slides were added by L. Lilien, and are © 2006-2007 by Leszek T.
Lilien. Requests to use L. Lilien’s slides for non-profit purposes will be gladly granted upon
a written request.
Chapter 1
INTRODUCTION
[Image of 2nd ed. cover added by L. Lilien.]
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
2
Pervasive vs. Wireless & Mobile Systems

Evolution

Distributed Computing (DIST)


Wireless Computing




Really: Wireless & Mobile Computing
Pervasive Computing (PERV)
Note: Textbook uses “wireless” and “mobile” as synonyms


Originally non-mobile wireless only
Mobile Computing (MOBI)


Originally wireline only
Not precise: e.g., can have wireless but not mobile
Q: Why to study Wireless & Mobile Computing?
A: It is foundation for PERV, its critical technology &
building block
Some other technologies for Pervasive Computing:



Embedded computing
Sensornets
Opportunistic networks (oppnets) and systems

See Lecture Section 0.B
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
3
1.1. The History of Mobile Radio Communication (1/3)
Emphasis (underlines) on this and next 2 slides added by LTL

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1880: Hertz – Initial demonstration of practical radio communication
1897: Marconi – Radio transmission to a tugboat over an 18 mi path
1921: Detroit Police Department: -- Police car radio dispatch (2 MHz
frequency band)
1933: FCC (Federal Communications Commission) – Authorized four
channels in the 30 to 40 MHz range
1938: FCC – Ruled for regular service
1946: Bell Telephone Laboratories – 152 MHz (Simplex)
1956: FCC – 450 MHz (Simplex)
1959: Bell Telephone Laboratories – Suggested 32 MHz band for high
capacity mobile radio communication
1964: FCC – 152 MHz (Full Duplex)
1964: Bell Telephone Laboratories – Active research at 800 MHz
1969: FCC – 450 MHz (Full Duplex)
1974: FCC – 40 MHz bandwidth allocation in the 800 to 900 MHz range
1981: FCC – Release of cellular land mobile phone service in the 40 MHz
bandwidth in the 800 to 900 MHz range for commercial operation
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
4
The History of Mobile Radio Communication (2/3)

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


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
1981: AT&T and RCC (Radio Common Carrier) reach an agreement to
split 40 MHz spectrum into two 20 MHz bands. Band A belongs to
nonwireline operators (RCC), and Band B belongs to wireline
operators
(telephone companies). Each market has two operators.
1982: AT&T is divested, and seven RBOCs (Regional Bell Operating
Companies) are formed to manage the cellular operations
1982: MFJ (Modified Final Judgment) is issued by the government DOJ
[LTL: Dept of Justice]. All the operators [LTL: RBOCs] were prohibited to (1)
operate long-distance business, (2) provide information services, and (3) do
manufacturing business
1983: Ameritech system in operation in Chicago
1984: Most RBOC markets in operation
1986: FCC allocates 5 MHz in extended band
1987: FCC makes lottery on the small MSA [LTL: Metropolitan Statistical Area]
and all RSA [LTL: Rural Service Area] licenses
1988: TDMA (Time Division Multiple Access) voted as a digital cellular
standard in North America
1992: GSM (Groupe Speciale Mobile) operable in Germany D2 system
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
5
The History of Mobile Radio Communication (3/3)
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1993: CDMA (Code Division Multiple Access) voted as another digital
cellular standard in North America
1994: American TDMA operable in Seattle, Washington
1994: PDC (Personal Digital Cellular) operable in Tokyo, Japan
1994: Two of six broadband PCS (Personal Communication Service) license
bands in auction
1995: CDMA operable in Hong Kong
1996: US Congress passes Telecommunication Reform Act Bill
1996: The auction money for six broadband PCS licensed bands (120 MHz)
almost reaches 20 billion US dollars
1997: Broadband CDMA considered as one of the third generation mobile
communication technologies for UMTS (Universal Mobile Telecommunication Systems)




During the UMTS workshop conference held in Korea
1999: ITU (International Telecommunication Union) decides the next
generation mobile communication systems (e.g., W-CDMA, cdma2000, etc.)
2001: W-CDMA commercial service beginning from October in Japan
2002: FCC approves additional frequency band for Ultra-Wideband (UWB)
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
6
[LTL:]
RF = radio
frequency
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
7
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
8
Applications
[LTL:]
Wireless Telephone
Washington, DC
Cincinnati, OH
[LTL:]
User moves but phone # unchanged
Maintaining the telephone number across geographical areas in a
wireless and mobile system
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
9
Generations of Wireless Systems & Services

1G - First Generation
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2G - Second Generation

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Primarily for voice communication
Using FDM (frequency division multiplexing)
Emphasis still on voice communication but allows for…
… Data communication
Using TDM (time division multiplexing)
Indoor/outdoor and vehicular environment
3G - Third Generation


Integrated voice, data, and multimedia communication
Need for:
 High volume of traffic / Real time data communication
 Flexibility, incl.


Frequent Internet access
Multimedia data transfer
Compatibility with 2G
Using compression
 Without compromising quality


Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
10
First Generation Wireless Systems and Services
Emphasis (underlines) and text in square brackets on this and next slide added by LTL
Note: “Cellular systems” called “mobile systems” outside North America.
1970s
Developments of radio and computer technologies for 800/900
MHz mobile communications [1st mobile band]
1976
WARC (World Administrative Radio Conference) allocates
spectrum for cellular radio
1979
NTT (Nippon Telephone & Telegraph) introduces the first
cellular system in Japan
1981
NMT (Nordic Mobile Telephone) 900 system introduced by
Ericsson Radio System AB and deployed in Scandinavia
1984
AMPS (Advanced Mobile Phone Service) [cellular] introduced by
AT&T in North America
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
11
Second Generation Wireless Systems and Services
1982 CEPT (Conference Europeenne des Post et Telecommunications)
established GSM [global special mobile] to define future Pan-European
Cellular Radio Standards
1990 Interim Standard IS-54 (USDC [US digital cellular]) adopted by TIA
(Telecommunications Industry Association)
1990 Interim Std IS-19B (NAMPS [narrowband AMPS]) adopted by TIA
1991 Japanese PDC (Personal Digital Cellular) system standardized by the
MPT (Ministry of Posts and Telecommunications)
1992 Phase I GSM system is operational
1993 Interim Standard IS-95 (CDMA) adopted by TIA
1994 Interim Standard IS-136 adopted by TIA
1995 PCS Licenses [added 2nd band (1900 MHz)] issued in North America
1996 Phase II GSM operational
1997 North American PCS deploys GSM, IS-54, IS-95
1999 IS-54: in North America
IS-95: in North America, Hong Kong, Israel, Japan, China, etc
GSM: in 110 countries
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
12
Two Basic Technology Choices for 3G



Basic technology in the U.S.
 cdma2000
Basic technology in Europe & Japan
 W-CDMA
Similar but design & implementation differences
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
13
Third Generation Wireless Systems and Services (1/2)

IMT-2000 (International Mobile Telecommunications-2000):
- Fulfill one's dream of anywhere, anytime communications a
reality.

Key Features of IMT-2000 include:
- High degree of commonality of design worldwide;
- Compatibility of services within IMT-2000 and with the fixed
networks;
- High quality;
- Small terminal for worldwide use;
- Worldwide roaming capability;
- Capability for multimedia applications, and a wide range of
services and terminals.
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
14
Third Generation Wireless Systems and Services (2/2)

Important Component of IMT-2000 is ability to provide high
bearer rate capabilities:
- 2 Mbps for fixed environment;
- 384 Kbps for indoor/outdoor and pedestrian environments;
- 144 Kbps for vehicular environment.

Standardization Work:
- Release 1999 specifications
- In processing

Scheduled Service:
- Started in October 2001 in Japan (W-CDMA)
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
15
Future: 4G

4G



Expected to implement all standards from 2G & 3G
Infrastructure only packet-based, all-IP
Some of the standards paving the way for 4G:
 WiMax
 WiBro (Korean)
 3GPP Long Term Evolution


To improves the UMTS mobile phone standard
Work-in-progress technologies

E.g., HSOPA, a part of 3GPP Long Term Evolutionon
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
16
Subscriber Growth for Wireless Phones
Subscribers
3G Subscribers
2G Digital-only
Subscribers
1G Analog-only
Subscribers
Year
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
17
China Leads World in Mobile Phone Users


Total [World] Mobile Users
Total [World] Analogue Users
> 800 million
> 70 million
[2003]
[2003]

ZDNet UK reports that the number of mobile phone users in
China reached 167 million in April, 2002, a rise of 6 million
subscribers on March, 2002.

The US, which is the second biggest market, has 136 million
subscribers.

Mobile phones are the preferred mode of communication in
Japan, with 56.8 million subscribers as of the end of March,
2003.
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
18
Flexibility & Versatility of 3G

Many diverse subsystems

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
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Different requirements for different needs
Different characteristics
 Corresponding to the requirements
Different coverage areas
Cell = area that can be covered by a single transmitting
station (usually called base station)

Picocells, microcells, macrocells & global “cell”


Figure – next slide
Why different cell sizes?
 Limited nr of channels per cell
 Smaller cells can serve more users

E.g. 2x smaller => can serve 2x more users on the same band
(with smaller range)
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
19
Coverage Aspect of Next Generation Mobile
Communication Systems
Satellite
In-Building
Urban
Suburban
Global
Picocell
Microcell
Macrocell Global
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
20
Transmission Capacity
Global System for Mobile Communications
as a Function of Mobility
Mobility
Vehicular
Pedestrian
Universal Mobile
Telecommunications System
Broadband radio
Mobile Broadband System
Local Multipoint Distribution System
Satellite Universal Mobile Telecommunications System
Broadband Satellite Multimedia
Stationary
0.01
0.1
1
10
100
Data Rate (Mb/s)
Transmission capacity as a function of mobility in some radio access systems
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
21
1.2. Characteristics of Cellular Systems
Wireless Technology & Associated Characteristics
[From 1st ed. slides – Slightly modified by LTL]


Wireless Technologies
 Cellular
 WLAN (Wireless LAN)
 GPS
 Satellite Based PCS
 Campus network (e.g., Ricochet, Carnegie Mellon U.)
 Home Networking
 Ad Hoc Networks
 WPAN (Wireless PAN = [personal area network])
 Incl. Bluetooth
 Sensor Networks
Different technologies needed for different applications
-- Details on the next slide –
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
22
[LTL: Yellow and
red highlights
added]
(phone calls)
(CMU campus)
(also oppnets, IANs)
(WPAN = wireless
personal area network)
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
23
Wireless Technologies for Application Classes
[LTL: Yellow and red highlights added]

Notice the following:
 Infrastructure-based networks vs. ad hoc networks (p.
11/2)

Terms & acronyms:
 Access point – AP (p. 8/-1, 10/2)
 Mobile station – MS (p. 11/2)
 Handoff and switching radio resources (p. 11/3)
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
24
Application Example: Medical Application
ATM backbone
network
In hospital
physician
Remote
databases
ATM switch
ATM switch
Wireless remote
consultation
Ambulance
Possibility for remote consulting
(including audio visual communication)
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
25
Wireless Features & Their Potential Apps
[LTL:]

Notice the following (p. 11/-1):
 “Anytime anywhere” not always required
 Often “many time” or “many where” is adeqate


Permanent connectivity not necessary
MS can:


Start transaction at AP1, then move away (loosing connection to it)
Get close to AP99 & complete transaction at AP99
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
26
1.3. Fundamentals of Cellular Systems
Ideal cell area
(2-10 km radius)
(circle)
Cell
Alterative
shape of a cell
(square)
BS
MS
MS
Hexagonal cell area
used in most models
Illustration of a cell with a mobile station (MS) and a base station (BS)
[LTL:]



Cell shapes (above)
Actually, cell may have a zigzag shape
Hexagon is a good approximation in practice

Also, gives non-overlapping cells

(used by clever bees for beehives)
E.g., circles would either overlap, or would have gaps in between
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
27
Cell Bandwidth Limitations & Multiplexing



Single BS per cell =>
limited bandwidth per cell
Increase bandwidth use
efficiency by multiplexing
MS
MS
B
S
Service
area
(Zone)
4 +1 basic multiplexing techniques





FDMA – frequency division multiple access
TDMA – time division multiple access
CDMA – code division multiple access
OFDM – orthogonal frequency division multiplexing
New: SDMA – space division multiple access

Specialized for microwave antennas
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
28
FDMA (Frequency Division Multiple Access)
[LTL:]


Used in all 1G cellular systems
BS allocates to each of n users a channel (a frequency
subband) for time the user needs it
Frequency
User n
…
User 2
User 1
Time
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
29
FDMA Bandwidth Structure
1
2
3
4
…
n
Frequency
Total bandwidth
[LTL:] Divided into n channels
(frequency subbands)
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
30
FDMA Channel Allocation
Channel 1
User 1
Channel 2
User 2
…
User n
…
Channel n
Mobile Stations
Base Station
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
31
TDMA (Time Division Multiple Access)
[LTL:]
time slot
…
User n
Frequency
User 2

Used in most 2G cellular systems
BS allocates to each user full bandwidth for duration of a
User 1

Time
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
32
TDMA Frame Structure
1
2
3
4
…
n
Time
Frame
Divided into n time slots
(by a round-robin method)
[LTL:]
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
33
TDMA Frame Illustration for Multiple Users
[LTL:]
Note: Non-overlapping time slices
“Time 2” slot starts after “Time 1” slot is over, etc.
User 1
Time 1
User 2
User n
n Mobile Stations
Time 2
…

…

…
Time n
Base Station
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
34
CDMA (Code Division Multiple Access)

CDMA a.k.a. spread spectrum technique

Used in some 2G and most 3G cellular systems

Simultaneous transmission of data from multiple users on
full frequency band
 Figure shows all users using:
Same range of frequencies
 Same time range
But
 Different codes


CDMA is enabled by orthogonal
codes (= keys)
 One distinct code assigned
by BS to each user
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
35
CDMA (Code Division Multiple Access) – cont.

CDMA transmission
 Transmitter:


Codes (using the key) each user’s data “stream”
Puts all coded individual data “streams” on data link


Receiver:




Creates a common “mixed” data stream
Gets common “mixed” data stream from data link
Uses keys to decode (“unmix”) individual data stream from the
“mixed” data stream
# of simultaneous users limited by # of possible
orthogonal codes
Complex but robust technique
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
36
[SKIP:] Transmitted & Received Signals
in a CDMA System
[LTL:] 10-bit codewords
Information bits
Code at
transmitting end
Transmitted signal
Received signal
Code at
receiving end
Decoded signal
at the receiver
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
37
Frequency Ranges used for
FDMA, TDMA & CDMA
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
38
OFDM (Orthogonal Frequency Division
Multiplexing)


OFDM idea – to reduce interference
 Convert single high-speed data stream to multiple lowspeed data streams
 Low-speed data streams sent in parallel using
(sub)channels working on multiple-frequencies
Frequencies of subchannels in FDMA vs. OFDM
 FDMA – non-overlapping frequencies of subchannels


Figure:
Copyright © 2003, Dharma P.
Agrawal and Qing-An Zeng.
All rights reserved
Even with gaps between subchannel
bands to reduce interference
OFDM - overlapping frequencies
of subchannels
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
39
39
Variants & Combinations of
FDMA, TDMA & CDMA


Many variants & combinations of FDMA, TDMA & CDMA beyond the scope of this discussion
Frequency hopping – combines FDMA & TDMA


Idea: One user uses one channel for a time slot, then
changes to another channel for another time slot
 See the next slide
 Receiver needs to know frequency hopping sequence
Main advantage (e.g., in defense applications):
Message gets through even if one frequency band
jammed
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
40
Frequency Hopping
Each user gets one time slot per frame, on a different frequency (round-robin
used for frequency selection)
[LTL:]
Frequency
Frame
Slot
f1
f2
f3
f4
f5
Time
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
41
1.4. Cellular System Infrastructure
BS
Service area
(Zone)
Early wireless system: Large zone
[LTL:]


Large zone requires a high-power BS
Better: replace large zone with smaller hexagonal zones
(next slide)
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
42
Cellular System: Small Zone
BS
BS
BS
BS
Service area
BS
BS
BS
[LTL:]

BS covers much smaller area now
 Requires much less power (for a given area)
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
43
Cellular System Infrastructure

Various kinds of Mobile Stations (MSs) a.k.a. wireless devices


Cellphone, PDA, PalmPilot, laptop with WiFi card, …
MSs need connectivity on the move
 E.g., connectivity from BSs in the cells they visit


BS is a gateway to wired infrastructure
Typical support for MSs: Cellular infrastructure

See next slide
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
44
MS, BS, BSC, MSC, and PSTN
wired link
PSTN
Home phone
…
MSC
BSC
…
…
BS MS
BS MS
MSC
BSC
BSC
…
…
BS MS
BS MS
BS MS
…
BSC
…
BS MS
BS MS
BS MS
[LTL:]



Several BSs connected via wireline links to one BSC (BS controller)
Several BSCs connected via wireline links to one MSC (Mobile Switching
Center)
Several MSCs interconnected via wireline links to PSTN (Public
Switched Telephone Network) and the ATM backbone
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
45
BS Structure

BS consists of
 Base Tranceiver System (BTS)
 Includes tower & antenna
 BSC
 Contains all associated electronics
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
46
MSC Database Supporting MS Mobility
& Incoming Call Scenario

MSC database for supporting MS mobility
1) Home location register (HLR) for MS


Located at the “home MSC” for MS
 Where MS is registered, billed, etc.
Indicates current location of MS
 Could be within home MSC’s area
OR
 Could be in the area of any MSC in the world
2) Visitor location register (VLR) on each MSC


Contains info on all MSs visiting area of this MSC
Incoming call scenario
 Based on the called #, incoming call for an MS is directed
to the HLR of the “home MSC” for this MS
 HLR redirects the call to MSC/BSC/BS where the MS is now
 VLR of the “current MSC” has info on MS (one of visiting MSs)
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
47
Control and Traffic Channels
Note: Forward/reverse in the U.S.,
downlink/uplink elsewhere
Mobile Station
Base Station
[LTL:]

4 simplex channels needed for control & traffic
 2 control channels



Exchange control msgs
Forward channel & reverse channel
2 traffic channels


For data
Forward channel & reverse channel
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
48
More on Control and Traffic Channels
[LTL:]



Traffic channels used for call duration => Large # of traffic
channels on each BS
Handshake steps for call setup use control channels
Control channels used for short duration => Small # of
control channels on each BS
 MSs compete for these few control channels

For call setup, etc.
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
49
Steps for a Call Setup from MS to BS
[LTL:]
Steps for a call setup from MS to BS  When MS initiates a call
BS
MS
1. Need to establish path
2. Frequency/time slot/code assigned
(FDMA/TDMA/CDMA)
Time

3. Control information acknowledgement
4. Start communic. on assigned traffic channel
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
50
Steps for a Call Setup from BS to MS
[LTL:]
Steps for a call setup from BS to MS:
 When MS responds to a call (somebody calls MS)
BS
MS
1. Call for MS # pending
2. Ready to establish a path
3. Use frequency / time slot / code
(FDMA/TDMA/CDMA)
Time

4. Ready for communication
5. Start communic on assigned traffic channel
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
51
A Simplified Wireless Communication System
Representation
[LTL:]



The figure shows major steps in wireless communications
Signal processing operations – beyond the lecture scope
Lecture will concentrate on system aspects of wireless data
communication
Antenna
Information to
be transmitted
(Voice/Data)
Coding
Modulator
Transmitter
Carrier
Antenna
Information
received
(Voice/Data)
Decoding
Demodulator
Receiver
Carrier
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52
1.5. Satellite Systems

Application areas of satellite systems
 Traditional Applications
 Weather satellite
 Radio and TV broadcasting
 Military satellites
 Navigation and localization (e.g., GPS)

Telecommunication Applications
 Global telephone connections
 Backbone for global network
 Connections for communication in remote places or
underdeveloped areas
 Global mobile communications
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53
Basic Concepts & Terminology

Only LOS communication is possible





LOS = line of sight
Satellites further away from earth cover a wider area
Satelites can emit one or more satellite beams
Satellites w.r.t. position over earth
 Geostationary
 Rotating around the earth
ES – earth station
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
54
History of Satellite Systems
50th anniversary of the space age on October 4, 2007
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55
1.6. Network Architectures and Protocols


[LTL:] Protocol = basic set of rules followed to provide
systematic signaling steps for information exchange
 Other protocols:
Diplomatic protocols, protocol to login, …
[LTL:] We will cover later following protocol reference
models and protocols:
 Open Systems Interconnections (OSI) reference model
 Transmission Control Protocol (TCP) (on top of IP)
 Internet Protocol (IP)
 Internet Protocol Version 4 (IPv4)
 Internet Protocol Version 6 (IPv6) – work in progress
 Mobile IP (MIP)
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56
1.7. Ad Hoc Network




[LTL:] Ad hoc network (AHN)
Def 1: AHN is a local network with wireless connections or
temporary plug-in connections, in which mobile or portable
device are a part of the network only while they are in close
proximity
Def 2: AHN is a collection of wireless MHs forming a
temporary network without the aid of any centralized
administration or standard support services regularly
available on the wide area network (WAN) to which the hosts
may normally be connected
Examples:


AHN 1: Instructor’s and students’ computers can create an AHN
during lectures
AHN 2: Oppnet used after an earthquake
Copyright
© Leszek
2003, Dharma
P. Agrawal and Qing-An Zeng. All rights reserved
© 2007 by
T. Lilien
57
1.7. MANET


[LTL:] MANET = mobile ad hoc network - an autonomous
system of mobile nodes, mobile hosts (MHs), or mobile
stations (MSs) connected by wireless links
MSs of a MANET also serve as routers
 These routers are mobile
 Route messages from SRC to DEST - see Figure
 Multihop routing
 Store-and-forward passing of info in P2P (peer-to-peer)
way
Source
Destination
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58
MANETs – cont.1


MANETs are highly dynamic
 All nodes, incl. routers, are mobile
=> topology highly dynamic, unpredictable
 Topology change due to MSs mobility made known to
(some) other nodes
Types w.r.t. infrastructure support
 Stand alone - no infrastructure support
 Limited infrastructure support
 Some routers have access to a fixed infrastructure


E.g., access to Internet – like in oppnets
E.g., stub network (SN) –

Stub network = a single LAN which never carries packets
between two remote hosts; all traffic is to and/or from local
hosts
 Multiple routers on SN don't route to one another, they
will only route a packet into SN (if it's destined for SN), and
out from SN (if it originated on SN) [cf. “stub network“ in Wikipedia]
Copyright © 2003, Dharma P. Agrawal and Qing-An Zeng. All rights reserved
59
MANETs – cont.2


Location of MSs in a MANET:
within buildings, highways, vehicles, on and within human
bodies
MANET nodes equipped with a “radio”
“Radio” = wireless transmitter & receiver (or: wireless transceiver)
 With antenna
 Types of antennas:





Omnidirectional
Directional
Steerable
Any combination of these
Xmit/rcv parameters affect MANET topology at any given
moment
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60
Wireless Sensor Networks

(Ad Hoc) Wireless Sensor Networks (WSNs) – a specialized subclass of AHNs
 Sensor(s) in each node in addition to processor and radio
 Sensors sense/measure some physical characteristcs
[LTL:]


Can be planted at random


Base Station
Even thrown out of a speeding
vehicle, even from a plane


Temperature, humidity, acceleration, pressure, toxicity, …
Note: The plane in the Figure
is BS & collects data. Another
one could have dropped
sensor nodes earlier
BS collects &
aggregates
sensed info
Example 1 (Fig):
Sensing enemy’s
moves
Antenna
Target
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Sensor
61
Example 2: Sensing a Cloud of Smoke
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62
1.8. Wireless LAN and PAN



IEEE 802.11 = Wireless Local Area Network (WLAN) using the
IEEE 802.11
HiperLAN is a European Standard
Bluetooth nets are examples of Wireless Personal Area Networks
(WPAN)
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63
End of Section 1 (Ch.1)