TDDD66:
Mobile Networks
Linkoping University, Sweden, Fall 2014
Niklas Carlsson
http://www.ida.liu.se/~nikca/
Slides in this course are adapted or based on various on-line resources (including lectures
notes by Juha Takkinen, Anirban Mahanti, Carey Williamson, Jim Kurose, and Keith Ross)
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People
Examiner and lecturer
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Lab assistants
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Niklas Carlsson, Associate Professor
Research area: Design, modeling, and
performance evaluation of distributed systems
and networks
Vengatanathan Krishnamoorthi, PhD student
Director of studies
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Patrick Lambrix
1-2
Course Overview
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Approximately six (6) theory lectures and
three (3) lectures on system analysis
A written exam
Grads: F, 3, 4, 5.
One project with various milestones, a written
report, and a seminar presentation
Four lab times in which to report and discuss
one or two assignments
A selection of scenarios used in the PBL
groups, the projects, and some of the
analysis lectures
See website for more information ...
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1-3
4
My expectations
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Read …
 2.5 textbooks (one main book) and some
research articles
 Lots of content
 Not time to cover everything during lectures
Work hard
 Pay attention during lectures
 Read after class
 Make sure you understand all the material
Follow deadlines and office hours
1-5
What to expect? (What will be covered?)
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Design principles for mobile systems
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Design, resource, and performance tradeoffs in the
mobile systems
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Conceptual view
General working knowledge of protocols/applications
Detailed knowledge of selected protocols/applications
Glimpse into the future
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Emerging trends and technologies
1-6
7
What is Wireless Networking?
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The use of infra-red (IR) or radio frequency (RF)
signals to share information and resources
between devices
Promises anytime, anywhere connectivity
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Laptops, palmtops, PDAs, Internet-enabled phone
promise anytime untethered Internet access
No wires!
8
What is Wireless Networking?


The use of infra-red (IR) or radio frequency (RF)
signals to share information and resources
between devices
Promises anytime, anywhere connectivity


Laptops, palmtops, PDAs, Internet-enabled phone
promise anytime untethered Internet access
No wires!
9
What is Wireless Networking?


The use of infra-red (IR) or radio frequency (RF)
signals to share information and resources
between devices
Promises anytime, anywhere connectivity

Laptops, palmtops, PDAs, Internet-enabled phone
promise anytime untethered Internet access

No wires!
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Lots of media buzzwords!
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Mobile Internet, Pervasive Computing, Nomadic
Computing, M-Commerce, Ubiquitous Computing …
… and acronyms; e.g., CSMA, WiFi, 802.11, …
10
Wireless Networking Technologies
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Operating modes
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Infrastructure mode
Ad-hoc mode
11
Infrastructure Mode
network
infrastructure
Infrastructure mode
 base station connects
mobiles into wired
network
 handoff: mobile
changes base station
providing connection
into wired network
12
Ad hoc Mode
Ad hoc mode
 no base stations
 nodes can only
transmit to other
nodes within link
coverage
 nodes organize
themselves into a
network: route among
themselves
13
Two important
(but different!)
challenges
14
Two important
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(but different!)
challenges
Communication over wireless link
Handling mobile user who changes point of
attachment to network
15
Two important


(but different!)
challenges
Communication over wireless link
Handling mobile user who changes point of
attachment to network
16
Two important


(but different!)
challenges
Communication over wireless link
Handling mobile user who changes point of
attachment to network
17
Two important


(but different!)
challenges
Communication over wireless link
Handling mobile user who changes point of
attachment to network
** In this course we will look at unique
challenges and opportunities in wireless
communication, including the two above.
18
Wireless Link Characteristics
Differences from wired link ….
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Decreasing signal strength: radio signal attenuates as it
propagates through matter (path loss)
Interference from other sources: standardized wireless
network frequencies (e.g., 2.4 GHz) shared by other devices
(e.g., phone); devices (motors) interfere as well
Multi-path propagation: radio signal reflects off objects
ground, arriving at destination at slightly different times
…. make communication across (even a point to point) wireless link
much more “difficult”
 Higher error rates; lower bandwidths; non-uniform
transmission characteristics; increased usage costs; and
increased susceptibility to interference and eavesdropping
19
Wireless Link Characteristics
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SNR: signal-to-noise ratio
 larger SNR – easier to extract
signal from noise (a “good thing”)
10-1
SNR versus BER tradeoffs
 given physical layer: increase
10-3
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power -> increase SNR ->
decrease BER
given SNR: choose physical layer
that meets BER requirement,
giving highest throughput
10-2
BER
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10-4
10-5
10-6
10-7
10
20
30
40
SNR(dB)
QAM256 (8 Mbps)
QAM16 (4 Mbps)
BPSK (1 Mbps)
20
Wireless Network Characteristics
Multiple wireless senders and receivers create additional
problems (beyond multiple access):
C
A
B
A
B
Hidden terminal problem
C
C’s signal
strength
A’s signal
strength
space
 A and B can hear each other
Signal fading:
 B and C can hear each other
 A and B hear each other
 A and C can’t hear each other
 B and C hear each other
 thus A and C are unaware of
 A and C can’t hear each other
their interference at B
interfering at B
21
In this course … the Internet
protocol stack…
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application: supporting network
applications
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transport: host-host data transfer
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IP, routing protocols
link: data transfer between
neighboring network elements
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TCP, UDP
network: routing of datagrams from
source to destination
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FTP, SMTP, HTTP
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet
protocol stack…

application: supporting network
applications


transport: host-host data transfer


IP, routing protocols
link: data transfer between
neighboring network elements


TCP, UDP
network: routing of datagrams from
source to destination


FTP, SMTP, HTTP
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet
protocol stack…

application: supporting network
applications


transport: host-host data transfer


IP, routing protocols
link: data transfer between
neighboring network elements


TCP, UDP
network: routing of datagrams from
source to destination


FTP, SMTP, HTTP
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet
protocol stack…

application: supporting network
applications


transport: host-host data transfer


IP, routing protocols
link: data transfer between
neighboring network elements


TCP, UDP
network: routing of datagrams from
source to destination


FTP, SMTP, HTTP
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet
protocol stack…

application: supporting network
applications


transport: host-host data transfer


IP, routing protocols
link: data transfer between
neighboring network elements


TCP, UDP
network: routing of datagrams from
source to destination


FTP, SMTP, STTP
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet
protocol stack…

application: supporting network
applications


transport: host-host data transfer


IP, routing protocols
link: data transfer between
neighboring network elements


TCP, UDP
network: routing of datagrams from
source to destination


FTP, SMTP, HTTP
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet
protocol stack…

application: supporting network
applications


transport: host-host data transfer


IP, routing protocols
link: data transfer between
neighboring network elements


TCP, UDP
network: routing of datagrams from
source to destination


FTP, SMTP, HTTP
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical