Information Theory for Mobile Ad-Hoc Networks (ITMANET): The FLoWS Project

1. Information Theory for Mobile Ad-Hoc Networks (ITMANET): The FLoWS Project FLoWS Overview and Update Andrea Goldsmith

2. DARPA’s ITMANET Challenge Hypothesis: A better understanding of MANET capacity limits will lead to better network design and deployment. 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.

3. Limitations in theory of MANETs today • 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. Wireless Information Theory Wireless Network Theory B. Hajek and A. Ephremides, “Information theory and communications networks: An unconsummated union,” IEEE Trans. Inf. Theory, Oct. 1998. Optimization Theory

4. Our Approach: Consummating Unions • 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 Wireless Information Theory Wireless Network Theory Optimization Theory

5. FLoWSProgram 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.

6. MANET Metrics Constraints Capacity and Fundamental Limits Capacity Layerless Dynamic Networks Delay Models and Dynamics Upper Bound New Paradigms for Upper Bounds Lower Bound Degrees of Freedom Energy Source Coding and Network Utility Capacity Delay (C*,D*,E*) Utility=U(C,D,E) FLoWS Energy/SNR Fundamental Limits of Wireless Systems Models New MANET Theory Application Metrics Metrics Application Metrics and Network Performance

7. 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 • RationaleRemove 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

8. Thrust Synergies and New Intellectual Tools Thrust 1 New Bounding Techniques Code Construction Combinatorial Tools Thrust 2 Dynamic Network IT Optimization Structured Coding Thrust 3 CSI, Feedback, and Robustness Stochastic Network Analysis Optimization Game Theory

9. 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.

10. 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

11. Thrust 1 Achievements Zheng: error exponents unequal error protection, embedded control messages to reduce overhead. New bounding techniques Effros, Koetter: A characterization of the source coding region of networks for “line networks” Koetter: likelihood forwarding Zheng, Medard: New techniques to unify multiple description and multi-resolution, distortion-diversity Code construction Network information theory Moulin: covert channel by timing information Goldsmith: Interference channel with cognitive user, “asymmetric” cooperation Koetter, Effros, Medard: Equivalence classes of networks based on emulation of a channel or a building block by arbitrary channels, including multipoint channels 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 Networking and optimization Combinatorial Tools

12. 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 Medard, Zheng: Diversity-distortion tradeoff Moulin: Error/erasure tradeoff for compound channel Coleman: Joint Source/Channel Coding in Networks Moulin: Universal Decoding in MANETs Effros, Goldsmith: Generalized capacity, distortion, and joint source/channel coding. Zheng: Message embedding in feedback channels Zheng: Embedded Coding and UEP Goldsmith: Broadcasting with layered codes CSI, feedback, and robustness Structured coding

13. Thrust 3 Achievements Optimization Theory Distributed efficient algorithms for resource allocation Boyd: Efficient methods for large scale network utility maximization Goldsmith: Layered broadcast source-channel coding Medard, Ozdaglar: Cross-Layer optimization for different application delay metrics and block-by-block coding schemes Medard, Shah: Distributed functional compression Boyd, Goldsmith: Wireless network utility maximization (dynamic user metrics, random environments and adaptive modulation ) Medard, Ozdaglar: Efficient resource allocation in non-fading and fading MAC channels using optimization methods and rate-splitting Ozdaglar: Distributed optimization algorithms for general metrics and with quantized information Goldsmith, Johari: Game-theoretic model for cognitive radio design with incomplete channel information Shah: Capacity region characterization through scaling for arbitrary node placement and arbitrary demand Johari: Local dynamics for topology formation Shah: Low complexity throughput and delay efficient scheduling Ozdaglar: Competitive scheduling in collision channels with correlated channel states Meyn: Generalized Max-Weight policies with performance optim- distributed implementations Game Theory New resource allocation paradigm that focuses on hetereogeneity and competition Stochastic Network Analysis Flow-based models and queuing dynamics

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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 information-theoretic approach”, IEEE Proc’09 (w/ Jafar, Maric, and Srinivasa)

21. 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

22. 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)