Information Theory for Mobile Ad-Hoc Networks (ITMANET): The FLoWS Project FLoWS Progress and Next Steps Andrea Goldsmith Phase 3 Kickoff Sept , 2009

FLoWS Challenge, Progress, and Goals Develop and exploit a more powerful information theory for mobile wireless networks. The development of this theory has progressed along three main thrust areas, with breakthrough progress and new theory in each area. Synergies between thrust areas have emerged, which are blurring the lines between thrusts. In Phases 3-4 our goal is to identify and attack the largest outstanding ITMANET challenges

Capacity Delay Power Upper Bound Lower Bound Capacity and Fundamental Limits Application Metrics Capacity Delay Power Utility=U(C,D,E) Application and Network Optimization (C*,D*,E*) Constraints Degrees of Freedom Models and Dynamics Application Metrics and Network Performance Layerless Dynamic Networks New Paradigms for Upper Bounds Models New MANET Theory MANET Metrics Metrics Fundamental Limits of Wireless Systems

Thrust Objectives and Rationale Models and Metrics (Leads: Effros,Goldsmith,Medard): –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: Effros,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, Coleman) –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,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

Two New PIs Added to FLoWS Cover and El Gamal have been added for the last two phases to complement the existing team Cover’s work will focus on –Coordinated capacity: How much dependence can be set up with a given set of communication constraints –Applications include distributed game theory, task assignment and rate distortion theory. El Gamal’s work will focus on –Network information theory to develop new coding schemes for the canonical channel models with many users –Computing/decision making over a network with distributed sources: lossy distributed averaging

Metrics and Models Lead: Goldsmith and Effros All PIs Contribute Project Thrusts and Organization New Paradigms for Upper Bounds Co-Leads: Effros and Medard — Cover — El Gamal — Koetter — Goldsmith Layerless Dynamic Networks Co-Leads: Zheng and Coleman — Cover — Effros — El Gamal — Goldsmith — Koetter — Medard — Moulin — Shah App. Metrics and Network Performance Co-Leads: Ozdaglar and Shah — Coleman — Effros — Goldsmith — Johari — Medard

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

Open Questions circa 2006 Capacity of large dynamic networks Capacity of basic network building blocks XiXi Y i-1 p(y i,s i |x i,s i-1 ) S i-1 SiSi D YiYi Tx Rx Capacity of time-varying links (with/without feedback)

Progress on these questions XiXi Y i-1 p(y i,z i,s i |x i,s i-1 ) S i-1 SiSi D YiYi Tx Rx Capacity of time-varying links (with/without feedback) Capacity of finite-state Markov channels with feedback Converses under unequal error protection Multiplexing-diversity-delay-distortion tradeoffs in MIMO Generalized capacity and separation Capacity of basic network building blocks Capacity region/bounds for Z channel and interference channels Capacity bounds for cognitive interference/MIMO channels Upper bounds and converses for interference channels with a relay (via interference and message forwarding)

Capacity of dynamic networks Network equivalence Scaling laws for arbitrary node placement and demand Multicast capacity Effect of feedback and side information Dynamic/multiperiod network utility maximization Generalized Max-Weight policies Game-theoretic approaches Mobility for interference mitigation Delay or energy minimization Distributed optimization

New Theory Thrust 1 –Equivalence classes Thrust 2 –Layered and structured codes –Control principles for feedback channels –Generalized capacity and separation Thrust 3 –Stochastic Multi-period Network Utility Maximization –Relaxation and distributed techniques for network optimization –Stochastic games Interthrust –Relaying, cooperation and cognition –Network coding –Capacity regions for more than 3 users –Coordination capacity

Thrust 0 Recent Achievements Metrics Effros, Goldsmith: Expectation and Outage in Capacity and Distortion Models Goldsmith: Diversity/multiplexing/delay tradeoffs Effros: networks with side information Shah: multicast capacity Moulin: Mobility Medard: delay/energy minimization Zheng: UEP Medard, Zheng: Distortion-Outage tradeoff Coleman, Effros, Goldsmith, Medard, Zheng: Channels and Networks with Feedback Goldsmith: Cognitive Nodes Cover: Coordinated Networks Medard: Stability Regions El Gamal: More than 3 users

New bounding techniques Thrust 1 Recent Achievements Code construction Network information theory Networking and optimization Combinatorial Tools Metrics Koetter, Medard: On the stability region of networks with instantaneous decoding Goldsmith: multicasting with a relay Effros: linear code construction Effros: continuity of network coding regions Zheng, Medard : distortion-outage tradeoff Medard: effect of coding versus routing Goldsmith: capacity and interference rates for the interference channel Goldsmith: multi -way relay channel Goldsmith: joint source-channel coding with limited feedback Cover : Capacity of coordinated actions El Gamal: more than 3 users

Dynamic Network Information Theory CSI, feedback, and robustness Structured coding Thrust 2 Recent Achievements Effros: two stage polar codes Coleman: Control principle for feedback channels Zheng: tilted matching for feedback channels Medard, Zheng: Diversity-distortion tradeoff Goldsmith: Joint source channel coding / outage Effros: linear representation of network coding Cover: coordination capacity El Gamal: BC with 3+ receivers Effros: distributed network coding with coded side information Goldsmith: Multicast with relay; BC with cognitive relay Moulin: exploiting mobility of relay networks

Thrust 3 Recent Achievements Shah: Distributed MAC using queue based feedback Johari: Large network games Meyn: Q-learning for network optimization Boyd, Goldsmith: Wireless network utility maximization as a stochastic optimal control problem Optimization Distributed and dynamic algorithms for resource allocation Stochastic Network Analysis Flow-based models and queuing dynamics Game Theory New resource allocation paradigm that focuses on hetereogeneity and competition Ozdaglar: Distributed second order methods for network optimization Ozdaglar: Noncooperative power control using potential games Effros: Noncooperative network coding Medard: Decoding and network scheduling for increased capacity Ozdaglar: Near potential games for network analysis Johari: Supermodular games El Gamal: Overhead in distributed algorithms

FLoWS progress since March New breakthroughs in upper bounds, feedback and CSI, cognitive techniques, interference forwarding, multicast traffic, and dynamic/distributed network optimization, New synergies within and between our thrust areas New/ongoing collaborations among PIs within FLoWS and with Nequit PIs; integration of new PIs Cover and El Gamal Overview paper for Scientific American to appear –Co-authors: Effros, Goldsmith, Medard Comm. Magazine paper with overview of FLoWS –Submitted and reviewed; likely to be accepted after revision Discussion of Phase 3 and 4 progress criteria –Identification of main challenges Website updated with March PI meeting slides, recent publications, and recent results.

Focus Talks and Posters Thrusts 1 and 2: –El-Gamal: More than Three Users –Cover: Coordination Capacity Thrust 2: –Zheng: Tilted Matching for Feedback Channels Thrust 3: –Ozdaglar: Near-Optimal Power Control in Wireless Networks: A Potential Game Approach Posters on all recent achievements

Progress Criteria: Phase 3 1.Revolutionize upper bounding techniques through new and different approaches that go beyond the classical MIN-CUT bounds and Fano's inequality that have dominated capacity bounds for the last several decades. 2.Determine the optimal channel/network “coding” that achieves these capacity upper bounds when possible, and characterize for which classes of networks gaps still exist between achievability & upper bounds, & why. 3.Develop a generalized theory of rate distortion and network utilization as an optimal and adaptive interface between networks and applications that results in maximum performance regions 4.Demonstrate the consummated union between information theory, networks, and control; and why all three are necessary ingredients in this union Progress towards meeting each criteria (more details in Thrust talks) Identifying “grand challenges” remaining to develop an IT for MANETS First pass will be presented in the thrust talks Will focus on these challenges during Phases 3 and 4 Team meeting Tuesday dedicated to this topic

Project Impact To Date Recent Plenary Talks –Boyd: Stevun Lec.’08, CNLS’08, ETH’08, ISACCP’09, ISMP’09, ICOCA’09, CCCSP’09 –Goldsmith: Gomachtech’08, ISWPC’08, Infocom’08, RAWC’09, WCNC’09, ICCCN’09 –Medard: IT Winter School’08, UIUC Student Conference’08, Wireless Network Coding’08, ITC.09, ITW’09 –Meyn: Erlang Centennial’09, Yale Workshop’09, Diaconis Symp.’09 –Ozdaglar: ACC 2009, NecSys'09, ASMD’08 –Johari: World Congress of the Game Theory Society’08 –El-Gamal: Allerton’09, Padovani Lecture’09, Brice Lecture’09 –Shah: Net Coop’09, Winedale’09 Conference Session/Program Chairs/Panels –CTW’09, ITW’09, ISMP’09, INFORMS’09, ITW’10, CTW’10 Recent Tutorials –Meyn: Mathematics of OR’09, –Shah: CDC’09, Invited/award winning journal papers –“Breaking spectrum gridlock through cognitive radios: an information-theoretic approach”, Goldsmith, Jafar, Maric, Srinivasa, IEEE Proc’09. –“A Random Linear Network Coding Approach to Multicast”, Ho, Medard, Koetter, Karger, Effros, Shi, and Leong, Joint IT/Comsoc Paper Award –"XORs in the Air: Practical Wireless Network Coding“, Katti, Rahul, Hu, Katabi, Medard, and Crowcroft. Bennett Prize in Communications Networking 2009.

Publications to date 22 accepted journal papers, 16 more submitted 127 conference papers (published or to appear) SciAM paper to appear Comm. Magazine paper submitted and reviewed Book on FLoWS vision and results under development –Alternative to NoW Foundations and Trends article Publications website: –

Summary Significant progress in and across all thrust areas Ongoing and fruitful collaborations between PIs Powerful new theory has been developed that goes beyond traditional Information Theory and Networking Addition of El Gamal and Cover adds new perspective and experience to our team Significant impact of FLoWS research on the broader research community (IT, communications, networking, and control/optimization) Want to maximize research impact in the final two phases of the project by identifying key challenges within and beyond the progress criteria