M. Faloutsos UC Riverside 1

Open Problems: What should you work on for

the next 4 years?

Fred Baker, Fellow CISCO

Bob Briscoe, British Telecom

George Varghese, UCSD/entrepreneurJohn Wroclawski, ISI Networking Director

Facilitator: Michalis Faloutsos, UCRFacilitator: Michalis Faloutsos, UCR

ICNP 2006 - Panel

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We wish a quick recovery… to Darleen Fischer (NSF) who would have been here but cannot due to non-threatening health reasons

M. Faloutsos UC Riverside

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The Goal is to Provoke Provoking is an essential human function

I provoke, therefore I think, therefore I exist A good panel should result in a fist-fight Conclusion: We need controversy

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My First Choices for the Panel

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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Final Panel Fred Baker, Fellow CISCO Bob Briscoe, British Telecom George Varghese, UCSD/entrepreneur John Wroclawski, ISI Networking Director

Alphabetical Order

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The Focus of the Panel The most exciting idea you have read recently The right area for a new researcher to tackle A problem the community should solve

You would give money for the research You would invest in the start up You would give $20 out of your pocket

A technology or user trend that will make a splash in 2-5 years

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Playing the Devil’s Advocate

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My Challenge to the Panel: Everything important has already been

discovered We are not reinventing, just renaming Let the industry do the research it needs Academia is consumed by paper-o-lagnia

Greek: Lagnia = desire, lust for We should all change professions

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Something New and Cool I ‘d give $20 to see it fully implemented

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Cooperative Diversity in ad hoc networks

“United we transmit”

A

B

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Synchronous Tx = Contention

So far, overlapping transmissions = BAD Hidden and exposed terminals Self-contention: packets of the same flow

Current Focus: reduce contention

A B

CD

BAD

C

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Cooperative Diversity: A Paradigm Shift

Cooperation instead of Contention

A phy breakthrough Multiple transmissions

can be combined at the receiver

Not only they don’t cancel out

They improve the success of transmission!

A

B

Node A cooperates with neighbors to send the same packet to B

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Cooperative Diversity: Essentials

Solicit/select the cooperation of neighbors

Provide the cooperating neighbors with a copy of the data packet.

Ensure that the receiver has CSI for the links to every cooperating node.

A

B

Node A cooperates with neighbors to send the same packet to B

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Cooperative Diversity is Counter Intuitive

Transmission range is longer than interference range! The transmissions range is

increased by a factor of 5.4 The interference range by a

factor of 1.7 For diversity gain 15 dB,

path loss 3, BER 10^-3A

B

C

Coop Interference

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1.What Cooperation Buys Us1. We can “shorten” our paths

S D

S I D

2. Path using cooperative diversity

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2. What Cooperation Buys Us Can bridge gaps in sparse networks

Connect disconnected networks Enable weak-device networks

The sensor network reach-back problem Many sensors cooperate to reach the sink!

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Can this translate to network performance?

Phy layer has been well studied Recently efforts show big gains in higher

layer performance Implementation is pending…

CooperativePerformance is red

Thruput Delay

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If you want to see more: J.N.Laneman, “Cooperative diversity in wireless networks:

Algorithms and architectures”, Ph.D. Thesis, Massachusetts Institute of Technology, August 2002.

G. Jakllari et al. "A Cross-Layer Framework for Exploiting Virtual MISO Links in Mobile Ad hoc Networks" IEEE Transactions on Mobile Computing to appear.

G. Jakllari et al. "On Broadcasting with Cooperative Diversity in Multi-hop Wireless Networks ” IEEE JSAC to appear.

A. Khandani, et al. “Cooperative routing in wireless networks.”, Allerton Conference on Communications, Control and Computing, October 2003.

X, Li, Space-Time Coded Multi-Transmission Among Distributed Transmitters without Perfect Synchronization, IEEE Signal Processing Letters, 11(12), December 2004.

A. Sendonaris et al. “User Cooperation Diversity--Part II: Implementation Aspects and Performance Analysis”, IEEE Transactions on Communications, 51(11), November 2003.

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Thank You!