Information Theory for Mobile Ad-Hoc Networks (ITMANET):
The FLoWS Project
FLoWS Overview and Update
Andrea Goldsmith
DARPA’s ITMANET Challenge
• Develop and exploit a more powerful information
theory for mobile wireless networks.
• Anticipated byproducts include new separation
theorems to inform wireless network "layering" as
well as new protocol ideas.
Hypothesis: A better understanding of MANET capacity
limits will lead to better network design and deployment.
Limitations in theory of MANETs today
Wireless
Information
Theory
Wireless
Network
Theory
B. Hajek and A. Ephremides, “Information theory and communications
Optimization
networks: An unconsummated union,” IEEE Trans. Inf. Theory, Oct. 1998.
Theory
– Success on narrowly-defined information theory of wireless networks.
– Large body of wireless (and wired) network theory that is ad-hoc, lacks a
basis in fundamentals, and lacks an objective success criteria.
– Little cross-disciplinary work spanning these fields, except applying
optimization techniques to existing wireless network designs.
Our Approach: Consummating Unions
Wireless
Information
Theory
Wireless
Network
Theory
Optimization
Theory
• When capacity is not the only metric, a new theory is needed to deal with
nonasymptopia (i.e. delay, random traffic) and application requirements
– Shannon theory generally breaks down when delay, error, or user/traffic
dynamics must be considered
• Fundamental limits are needed outside asymptotic regimes
• Optimization provides the missing link to address these issues
FLoWS Program Objectives
• Develop tractable and insightful metrics and models
for MANET information theory.
• Define fundamental performance limits for MANETs in
terms of desired objective metrics.
• Obtain upper and lower performance bounds for
these metrics for a given set of MANET models.
• Define the negotiation between the application and
network for resource allocation and performance
optimization of our given metrics
• Bound the cost of using our set of metrics as the
interface between the network and applications.
MANET Metrics
New Paradigms
for Upper
Bounds
Constraints
Capacity and Fundamental Limits
Capacity
Upper
Bound
Layerless
Dynamic
Networks
Delay
Lower
Bound
Degrees of
Freedom
Energy
Application
Metrics and
Network
Performance
Models and
Dynamics
Source Coding and
Network Utility
Capacity
(C*,D*,E*)
Delay
Utility=U(C,D,E)
Energy/SNR
Metrics
Models
Fundamental Limits
of Wireless Systems
New MANET Theory
Application Metrics
Thrust Objectives and Rationale
• Models and Metrics (Leads: Effros and Goldsmith):
– Objective: Develop a set of metrics for dynamic networks that capture
requirements of current and future applications
– Rationale: Models for MANETs are needed that are tractable yet lead
to general design and performance insights
• New Paradigms for Upper Bounds (Leads: Koetter and Medard)
– Objective: Obtain bounds on a diversity of objectively-defined metrics
for complex interconnected systems.
– Rationale: A comprehensive theory for upper bounding the
performance limits of MANETs will help guide design
• Layerless Dynamic Networks (Lead: Zheng)
– Objective: Design of networking strategies as a single dynamic
probabilistic mapping, without pre-assigned layered structure
– Rationale Remove layering and statics from MANET theory.
• End-to-End Metrics and Performance (Leads:Ozdaglar and Shah)
– Objective: Provide an interface between application metrics and
network performance
– Rationale: A theory of generalized rate distortion, separation, and
network optimization will improve application performance
Thrust Synergies and New Intellectual Tools
Thrust 1
New Bounding
Techniques
Combinatorial
Tools
Code Construction
Thrust 2
Optimization
Dynamic
Network IT
Thrust 3
Optimization
Stochastic
Network
Analysis
Game Theory
CSI, Feedback,
and Robustness
Structured
Coding
Progress since December
• New breakthroughs in generalized capacity and separation,
robust source and channel coding, equivalence classes,
scaling laws, wireless NUM, cross-layer optimization, and
distributed resource allocation.
• New synergies within and between our thrust areas
• New and ongoing collaborations among PIs
• Overview paper for Scientific American
– Co-authors: Effros, Goldsmith, Medard
– Paper near completion, will be submitted next month
• JSAC Tutorial on MANET Capacity with Cognitive Radios
– Co-authors: Goldsmith, Jafar, Maric, and Srinivasa
– Paper accepted for publication, to appear in 2009.
• Website updated with Dec. PI meeting slides, recent
publications, and recent results.
Thrust 0 Achievements
Models
Boyd, Effros, Goldsmith, Zheng: Fading with/without CSI
Goldsmith:Finite State Markov Dynamics
Boyd, Goldsmith, Ozdaglar, Johari: General Network State Distributions
Shah: Arbitrary node placement and traffic
Boyd, Effros, Goldsmith, Koetter,
Ozdaglar, Shah: General traffic
models, including multicast traffic
Effros, Goldsmith: Expectation and
Outage in Capacity and Distortion
Goldsmith: Diversity/multiplexing/delay tradeoffs
Coleman, Medard, Koetter, Effros, Goldsmith : Capacity Regions
Boyd, Ozdaglar, Medard, Goldsmith: End-to-end optimization
metrics subject to specific constraints (e.g. delay)
Ozdaglar, Medard: Downloading delay
Moulin: Error-erasure tradeoffs
Zheng: Error exponents
Zheng, Medard: Distortion-diversity tradeoffs
Metrics
Thrust 1 Achievements
Zheng: error exponents unequal
Effros, Koetter: A characterization of the source
error protection, embedded control
messages to reduce overhead.
coding region of networks for “line networks”
Zheng, Medard: New techniques to unify multiple
description and multi-resolution, distortion-diversity
New bounding techniques
Koetter: likelihood forwarding
Code construction
Network information theory
Goldsmith: Interference channel with
Koetter, Effros, Medard: Equivalence
classes of networks based on emulation of
a channel or a building block by arbitrary
channels, including multipoint channels
cognitive user, “asymmetric” cooperation
Moulin: covert channel
by timing information
Goldsmith, Effros: generalized capacity and source-channel coding
Goldsmith, Medard, Katabi: analog network coding
Ozdaglar, Medard: Cross-layer optimization under different metrics and constraints
Ozdaglar, Medard: Network coding for downloading delay
Ozdaglar, Medard: Rate allocation in multiple access networks
Medard, Koetter: network coding capacity via conflict graphs
Combinatorial Tools
Networking and optimization
Thrust 2 Achievements
Dynamic Network Information Theory
Goldsmith: general relaying, soft combining
Goldsmith: Interference forwarding
Goldsmith: Degraded FS Broadcast Channels
Coleman: Rate Distortion of Poisson Processes
Goldsmith: DMT for multi-hop networks
Zheng: Euclidean Information Theory
Moulin: Information flow via timing
Coleman: “E-type” broadcasting channels
Goldsmith: Feedback
and Directed Information
Goldsmith: Cognitive users and interference
Moulin: Error/erasure tradeoff
for compound channel
Medard, Zheng: Diversity-distortion tradeoff
Coleman: Joint Source/Channel Coding in Networks
Moulin: Universal Decoding in MANETs
Zheng: Message embedding in feedback channels
Zheng: Embedded Coding and UEP
CSI, feedback, and robustness
Effros, Goldsmith: Generalized capacity,
distortion, and joint source/channel coding.
Goldsmith: Broadcasting with layered codes
Structured coding
Thrust 3 Achievements
Boyd: Efficient methods for large scale
network utility maximization
Optimization Theory
Distributed efficient algorithms
for resource allocation
Goldsmith: Layered broadcast source-channel coding
Medard, Shah: Distributed functional compression
Boyd, Goldsmith: Wireless network utility
maximization (dynamic user metrics, random
environments and adaptive modulation )
Ozdaglar: Distributed optimization algorithms for
general metrics and with quantized information
Shah: Capacity region characterization
through scaling for arbitrary node
placement and arbitrary demand
Medard, Ozdaglar: Cross-Layer optimization for
different application delay metrics and blockby-block coding schemes
Medard, Ozdaglar: Efficient resource allocation in
non-fading and fading MAC channels using
optimization methods and rate-splitting
Goldsmith, Johari: Game-theoretic model for
cognitive radio design with incomplete channel
information
Johari: Local dynamics for topology formation
Shah: Low complexity throughput and
delay efficient scheduling
Meyn: Generalized Max-Weight policies with
performance optim- distributed implementations
Stochastic Network Analysis
Flow-based models and
queuing dynamics
Ozdaglar: Competitive scheduling in collision
channels with correlated channel states
Game Theory
New resource allocation
paradigm that focuses on
hetereogeneity and competition
Focus Talks and Posters
• Thrust 1:
– Koetter: A tool oriented approach to network capacity
(joint with Effros and Medard)
• Thrust 2:
– Goldsmith: Interference in MANETs: Friend or Foe?
• Thrust 3:
– Shah: Capacity region of large wireless networks
(joint with Neisen and Gupta)
• Posters on all new (green) results
Progress Criteria: Phase 1 (completed)
• Upper and lower bounds characterization of n(n-1) capacity region for
small networks with simple assumptions
– Koetter, Effros, Medard: Equivalence classes of networks based on ability of a channel or a
building block to emulate arbitrary channels
– Goldsmith, Medard, Katabi: Joint relaying, combine symbols in PHY, bits, or network layer
• Scaling and achievability results for large networks with fixed traffic
– Shah: Optimal capacity scaling for arbitrary node placement and arbitrary multi-commodity
flows
– Shah: multiple access decomposition for constructive scaling laws
• Analysis of tractability vs. practicality of channel models and
robustness to modeling assumptions and system uncertainty
– Meyn, Zheng, Medard: mismatched receiver, online robust algorithm to combat imperfect
channel info.
– Goldsmith: Broadcasting with layered source code, graceful degradation for weaker users
• Joint characterization of trade-offs among delay, energy and capacity
– Medard, Zheng: diversity-distortion tradeoff
– Shah: Low complexity throughput and delay efficient scheduling
– Goldsmith, Boyd: Capacity and delay under Wireless NUM
Progress Criteria: Phase 1 (completed)
• Study of optimized node cooperation incorporating not only virtual
MIMO, cooperation diversity, conferencing, and relaying but also
network coding for networks of 5-10 nodes. Includes impact of
generalized decode-forward and amplify-forward (list decoding,
partial decoding). Includes impact of delay, energy, and outage
probability.
– Goldsmith: MANET capacity w/ node cooperation and cognition
– Koetter: Likelihood forwarding
• Study dynamic allocation of rate, power, and the spatial degrees of
freedom associated with multiple antennas, as well as dynamic
spectrum allocation
– Goldsmith, Johari: Game-theoretic model for cognitive radio design with incomplete
channel information
– Medard, Ozdaglar: Efficient resource allocation in non-fading and fading MAC channels
using optimization methods and rate-splitting
•
Study strengths and vulnerabilities posed by addressing jamming with
cooperating and non-cooperating nodes
– Moulin, Medard: On Manet jamming
Progress Criteria: Phase 1 (completed)
• Study fundamental limits of the ability of inside attackers to observe and
contaminate degrees of freedom in a MANET
– Medard, Effros: Byzantine’s attacks
• Study systematic techniques for bounding the achievable rate region for
distributed source coding in complex networks, considering issues of
robustness to unknown/imperfect source and network statistics and
application of universal coding and decoding techniques to such systems.
– Coleman: Joint Source/Channel Coding in Networks
– Effros/Koetter: A characterization of the source coding region of networks for “line networks”
• Study network-aware design; stability of network operation with respect to
application-aware optimization will be studied.
– Boyd: Dynamic and stochastic network utility maximization with delivery constraints
– Ozdaglar: Distributed optimization algorithms for general metrics and with quantized
information
Progress Criteria: Phase 2 (next 12 months)
– Evolve results in all thrust areas to examine more complex models,
robustness/security, more challenging dynamics, and larger networks.
•
•
•
•
•
•
•
•
Koetter, Effros, Medard: Network equivalence
Ozdaglar, Medard: Rate allocation in multiple access networks
Goldsmith: Multihop networks: Cooperation, Cognition, and Robustness Tradeoffs
Moulin: Error/erasure tradeoff for compound channel
Zheng: Message embedding in feedback channels
Coleman: “E-type” broadcasting channels
Johari: Local dynamics for topology formation
Meyn: Generalized Max-Weight policies with performance-optimal distributed
implementations
• Shah: Capacity scaling laws for arbitrary node placement and arbitrary demand
– Demonstrate synergies between thrust areas: compare and tighten upper
bounds and achievability results for specific models and metrics; apply
generalized theory of distortion and utility based on performance regions
developed in Thrusts 1-2.
•
•
•
•
Ozdaglar, Medard: Cross-layer optimization under different metrics
Zheng, Medard: Unifying multiple description and multi-resolution, distortion-diversity
Boyd, Goldsmith: Wireless NUM with cooperative PHY
Medard, Ozdaglar: Cross-Layer optimization for different application delay metrics and
block-by-block coding schemes
• Ozdaglar: Competitive scheduling in collision channels with correlated channel states
Progress Criteria: Phase 2 (next 12 months)
– Demonstrate that key synergies between information theory,
network theory, and optimization/control lead to at least an order of
magnitude performance gain for key metrics.
• Ozdaglar, Medard: Network coding for downloading delay
• Goldsmith: Generalized capacity, distortion, and separation
• Boyd, Goldsmith: Wireless network utility maximization
– Pose clearly defined community challenges related to evolving our
theory that inspires other researchers to collectively make
breakthrough progress.
• Community challenges posed in plenary talks and tutorials, as well as invited
papers and vision papers
– Publish 2 vision papers, one for the community (e.g. in the IEEE
Wireless Communications Magazine) and one for the broader
technical community (e.g. in Nature or Science) illuminating our
ideas, results, and their potential impact
• Draft paper for Scientific American near completion. To be submitted in Oct.
• Outline of community paper will be discussed in Friday team meeting
Project Impact To Date
• Plenary Talks and Panels
–
–
–
–
–
–
Boyd: Dysco’07, S. Stevun Lecture’08, CNLS’08, ETH’08
Effros: ISIT’07
Goldsmith: ACC’07, Gomachtech’08, ISWPC’08, Infocom’08, LTE Wshp’09
Medard: Gretsi’07, CISS’07, NRC’07, IT Winter School’08
Koetter: ITW’07, WiOPT’08
Meyn: Erlang Centennial’09
• Recent Tutorials
– Boyd: MOCCS’08, WOSP’08
– Ozdaglar: Networks' challenge: Where game theory meets network
optimization (ISIT’08)
– Medard/Koetter: Intro. to Network Coding (PIMRC’08)
– Maric/Dabora: Cooperation in Wireless Networks (PIMRC’08)
• Conference Session/Program Chair
– ISIT’07 Technical Program (Chairs: Medard and Goldsmith)
– CTW’08 session (Chairs: Andrews and Goldsmith)
• Invited journal papers
– “Breaking spectrum gridlock through cognitive radios: an informationtheoretic approach”, IEEE Proc’09 (w/ Jafar, Maric, and Srinivasa)
Publications to date
• 10 accepted journal papers, 10 more submitted
• 80 conference papers (published or to appear)
• Publications website:
– http://www.stanford.edu/~adlakha/ITMANET/flows_publications.htm
Summary
• Significant progress on all thrust areas
• Significant progress on synergies between thrust areas
• Ongoing and fruitful collaborations between PIs
• Roadmap towards meeting Phase 2 goals underway
• Significant impact of FLoWS research on the broader
research community (IT, communications, networking,
and control/optimization)