TDDD66: Mobile Networks

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

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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No wires!

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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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** 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

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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



FTP, SMTP, STTP


TCP, UDP




PPP, Ethernet


application

transport

network

link

physical



FTP, SMTP, HTTP


TCP, UDP




PPP, Ethernet


application

transport

network

link

physical

TDDD66: Mobile Networks

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Transcript of TDDD66: Mobile Networks