tddd66: mobile networks
TRANSCRIPT
TDDD66: Mobile Networks
Linkoping, Sweden, fall 2013
Niklas Carlsson Email: [email protected]
Office: 2B:476
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
Niklas Carlsson, Associate Professor
Research area: Design, modeling, and performance evaluation of distributed systems and networks
Lab assistants
Vengatanathan Krishnamoorthi, PhD student
Director of studies
Patrick Lambrix
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Course Overview
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
Three 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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My expectations
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
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What to expect? (What will be covered?) Design principles for mobile systems
Conceptual view
Design, resource, and performance tradeoffs in the mobile systems
General working knowledge of protocols/applications
Detailed knowledge of selected protocols/applications
Glimpse into the future
Emerging trends and technologies
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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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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!
Lots of media buzzwords! Mobile Internet, Pervasive Computing, Nomadic
Computing, M-Commerce, Ubiquitous Computing …
… and acronyms; e.g., CSMA, WiFi, 802.11, …
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Wireless Networking Technologies
Operating modes Infrastructure mode
Ad-hoc mode
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Infrastructure Mode
network infrastructure
Infrastructure mode
base station connects mobiles into wired network
handoff: mobile changes base station providing connection into wired network
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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
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Two important (but different!) challenges
Communication over wireless link
Handling mobile user who changes point of attachment to network
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Two important (but different!) challenges
Communication over wireless link
Handling mobile user who changes point of attachment to network
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Two important (but different!) challenges
Communication over wireless link
Handling mobile user who changes point of attachment to network
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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.
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Wireless Link Characteristics Differences from wired link ….
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
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Wireless Link Characteristics
SNR: signal-to-noise ratio
larger SNR – easier to extract signal from noise (a “good thing”)
SNR versus BER tradeoffs
given physical layer: increase power -> increase SNR -> decrease BER
given SNR: choose physical layer that meets BER requirement, giving highest throughput 10 20 30 40
QAM256 (8 Mbps)
QAM16 (4 Mbps)
BPSK (1 Mbps)
SNR(dB) B
ER
10-1
10-2
10-3
10-5
10-6
10-7
10-4
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Wireless Network Characteristics Multiple wireless senders and receivers create additional
problems (beyond multiple access):
A B
C
Hidden terminal problem A and B can hear each other
B and C can hear each other
A and C can’t hear each other
thus A and C are unaware of their interference at B
A B C
A’s signal strength
space
C’s signal strength
Signal fading: A and B hear each other
B and C hear each other
A and C can’t hear each other interfering at B
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In this course … the Internet protocol stack…
application: supporting network applications
FTP, SMTP, HTTP
transport: host-host data transfer
TCP, UDP
network: routing of datagrams from source to destination
IP, routing protocols
link: data transfer between neighboring network elements
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet protocol stack…
application: supporting network applications
FTP, SMTP, HTTP
transport: host-host data transfer
TCP, UDP
network: routing of datagrams from source to destination
IP, routing protocols
link: data transfer between neighboring network elements
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet protocol stack…
application: supporting network applications
FTP, SMTP, HTTP
transport: host-host data transfer
TCP, UDP
network: routing of datagrams from source to destination
IP, routing protocols
link: data transfer between neighboring network elements
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet protocol stack…
application: supporting network applications
FTP, SMTP, HTTP
transport: host-host data transfer
TCP, UDP
network: routing of datagrams from source to destination
IP, routing protocols
link: data transfer between neighboring network elements
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet protocol stack…
application: supporting network applications
FTP, SMTP, STTP
transport: host-host data transfer
TCP, UDP
network: routing of datagrams from source to destination
IP, routing protocols
link: data transfer between neighboring network elements
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet protocol stack…
application: supporting network applications
FTP, SMTP, HTTP
transport: host-host data transfer
TCP, UDP
network: routing of datagrams from source to destination
IP, routing protocols
link: data transfer between neighboring network elements
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
In this course … the Internet protocol stack…
application: supporting network applications
FTP, SMTP, HTTP
transport: host-host data transfer
TCP, UDP
network: routing of datagrams from source to destination
IP, routing protocols
link: data transfer between neighboring network elements
PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical