Mung Chiang, Ph.D. - US grants

An exciting paradigm is emerging over the last decade that applies pow-erful control and optimization theories to the design and analysis of communi-cation networks, resulting in intellectual and practical impacts much beyond the established frameworks of the 1980s. This trend has been driven by both new needs from the communications and networking fields and recent advances in control and optimization theories. There is already a substantial body of re-search results and applications that need to be transferred to university cur-riculum and the industry. Moreover, new results are being created at a rapid pace, intensifying the need for students and engineers to understand, and ap-ply, these new insights and techniques. The current project develops a new course on control and optimization of communication systems, and associated courseware, that teach students the mentality of tackling engineering problems as dynamic systems to be controlled and linear/nonlinear objectives to be opti-mized, and equip them with the ability to do so. It covers major communica-tions and networking advances in this area and provide students with hands-on experience on practical problems through numerical and experimental projects. This inter-disciplinary course has a flexible modular structure and the mathe-matical background needed in each module is presented using a 'just-in-time' approach. The project develops instructional materials that can be used in other institutions and the industry. It vigorously pursues various paths of dis-semination. It will transfer recent research advances into the mainstream cur-riculum of CS and EE, and facilitate the spread of knowledge from academia to the industry.

ITR: COLLABORATIVE RESEARCH: (EVS+NHS)-(int+dmc): 'FAST Copper': Dynamic Optimization of Resources in Frequency, Amplitude, Space, and Time for Broadband Access Networks

Mung Chiang, Princeton University
John Cioffi, Stanford University
Alexander Fraser, Fraser Research

Award 0427677

Abstract

Broadband access is the commercial and technical future of telecommunications. Higher data rates on access links enable any or all of video, data, and voice/audio signals. It is widely recognized that the ability to deploy ubiquitous, robust, broadband access services to the majority of U.S. households is vital to economic prosperity, a vibrant civil society, and homeland security. The goal of this 'FAST Copper' project is to help build an engineering foundation to bring broadband information services to everyone with a phone line, including people who live in rural and less-privileged areas. This can be achieved by substantially enhancing the rate and reliability of the existing copper plant access network. Equity of broadband information access in the U.S. will be enhanced as a result. There are two threads of research activities towards this goal: (a) dynamic and joint optimization of resources in Frequency, Amplitude, Space, and Time (FAST) to overcome the attenuation and crosstalk bottlenecks, and (b) integration of communication, networking, computation, modeling, and distributed information management in the multi-user environment of twisted pair networks. Innovations in both physical layer algorithms and network architectures and protocols are pursued. In particular, Dynamic Spectrum Management, a science of multi-user methods for adaptively tuning an access network to specific situations dynamically, is investigated for rate improvements and implementation viability. This proposal has major activities integrating research with education. It also facilitates close collaboration with industry in analyzing highly valuable empirical data and validating research results through extensive lab tests.

Motivation: Wireless local area networks have very promising commercial potential to be widely de-
ployed and used in a variety of application scenarios, but also suffer from a number of significant engineering
difficulties. For example, small cell sizes and unlicensed spectrum lead to sophisticated spatial interaction,
there is a lack of common air-interface to support mobile and time-sensitive applications, and interactions
among competing users, both access points and mobile stations, could form surprising and unpredictable
patterns. In addition, end-to-end transmissions in a wireless LAN often traverse a hybrid network, with
wireless hops as well as wired links in the backbone. This presents unique challenges in cross layer TCP-IP-
MAC-PHY interactions and offers new opportunities to optimize medium access control (MAC) and physical
layer (PHY) algorithms to enhance the end user experience.
There is no shortage of near term ideas from both industry and academia about how to improve the
delivery of wireless Internet services. What is missing is an optimization framework that captures utility at
the level of networked applications, and makes it possible to figure out whether any particular incremental
change at the MAC or PHY layer is positive or negative. The gap is the focus of this SGER proposal.
Kelly and Low have created the counterpart of this utility maximization framework in the wired world,
and it has led to a deeper understanding of TCP congestion control and to the development and field
testing of the new 'FAST TCP' protocol by the high energy physics community. The key insight in this
approach is to start with a given network protocol and ask: 'If this distributed protocol is the solution to an
underlying global optimization problem, what is that optimization problem?' The wireless world presents a
very significant challenge and the new framework needs to capture spatial interaction within a cell, operation
in unlicensed spectrum, a mix of contention and scheduling at the MAC layer, and the flexibility of achieving
different rate-reliability tradeoffs by coding techniques.
For example, we know that TCP throughput can be improved through coordination of spatial resources,
specifically through space-time coding. Embedded diversity transforms spatial diversity into a fine grained
resource that can provide opportunistic communication when the channel is good and reliable communication
with latency guarantees when it is less benign. We expect to see significant benefits in specific cross layer
designs based on a completed framework of wireless utility maximization, but the value of the proposal is a
general proof of principle that can apply to an arbitrary wireless protocol or coding technique.
Project Focus and Intellectual Merit: This SGER project is a proof of concept - the particular
focus is on modelling the medium access mechanisms and leveraging the new coding paradigm of embedded
diversity. The particular objective in the next 12 months of SGER investigation is to identify the global
optimization problem to which coding (with embedded diversity) and scheduling (for medium access) is the
solution.
Preliminary results have recently been obtained by the PIs on tackling interference in utility maximization
problems and on designing new space-time codes with embedded diversity. We believe that by filling in
two remaining holes: modelling medium access and leveraging coding techniques, a complete and widely
applicable framework of wireless network utility maximization will be completed at the conclusion of the
SGER project.
Broader Impacts: The research activities in this SGER proposal will be fully integrated with a variety
of educational activities currently pursued by the PIs. These include curriculum developments of four new,
inter-disciplinary courses at Princeton, two at undergraduate level and two at introductory graduate level,
active supervision of undergraduate research projects on wireless LAN, and student summer internships
being arranged with our industrial partners.
A unique and important aspect of this proposal is a detailed arrangement of close collaboration with
five major telecom and networking companies in the wireless LAN space: AT&T Labs, Cisco, Flarion
Technologies, Intel, and SBC. These interactions with the industry will further strengthen the research and
education components of the project and ensure visible impacts of the intellectual contributions.
A workshop on wireless LAN research, development, and deployment will be hosted at Princeton by the
PIs at the conclusion of this SGER project. We will compile a list of major research issues associated with
wireless LAN and a list of industrial researchers or managers interested in these topics, which may be helpful
to future NSF programs on topics related to mathematical models for wireless networks.

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From the early days of the ARPAnet to today's global Internet, most research on network protocols has focused on traditional performance metrics such as delay, loss, and throughput. However, it is becoming increasingly important that a network not only provides good performance, but also do so in the face of a complex, uncertain, error-prone, and ever-changing environment. In today's networks, operating conditions may change as a result of user behavior (e.g., a shift in traffic to a newly popular Web site) or the underlying infrastructure (e.g., an equipment failure). In all such cases, the network and its operators must respond in a robust fashion, continuing to provide good performance despite changing conditions.

The need for "robust" network operation leads to a set of design considerations that the principal investigators (PIs) refer to as the "X-ities" (since they all end in "ity"): non-fragility, manageability, diagnosability, optimizability, scalability, and evolvability. Intuitively, we know that these X-ities are crucially important if we are to design and analyze robust networks and protocols. Yet, compared with standard performance metrics, these X-ities often lack theoretical foundations, quantitative frameworks, or even well-defined metrics and meaning. The goal of this project is to build a rigorous, quantitative foundation for explicitly considering the X-ities in the design and analysis of network protocols. The PIs consider a number of specific problems, broadly in the area of routing protocols, that concretely address several of the X-ities---with particular emphasis on non-fragility and manageability---and to begin to draw larger lessons from commonalities among the problems studied.

The proposed research focuses on the X-ities in the context of the routing protocols that ensure that each computer has paths through the network to send data to other computers. There are several reasons for this choice. First, routing protocols are a crucial part of the network architecture---they are the very glue that holds the disparate parts of the Internet together. Second, the X-ities of IP routing have not received significant formal attention. Third, routing protocols expose key issues of incomplete information (e.g., across networks run by different institutions) and interacting levels of control (e.g., between applications and the underlying network)---concerns that should arise in any thorough treatment of network X-ities. Finally, routing provides a compelling context in which the X-ities can be quantitatively studied. For example, we can quantify the performance trade-off between a fragile routing solution that has been optimized for narrow, well-defined operating conditions, versus a solution that will perform well of over variety of operating conditions. The contributions of the proposed research are three-fold:

A first quantitative study of X-ities: The intellectual challenges in rigorously understanding the X-ities are many. The PIs define specific metrics and develop mathematical models to quantitatively study each X-ity.

Solutions to specific problems: To make the study of the X-ities concrete, the PIs consider a set of research problems broadly in the area of routing that are of interest in their own right.

The beginnings of a foundation for studying X-ities: The PIs believe that the study of network X-ities is a crucially important area for long-term research in networking.

The X-ity research will lead to a deeper quantitative understanding of how to develop robust network architectures and protocols---technology that is playing an increasingly crucial role in our daily lives. The broader impacts of the research will include enhanced teaching, training, and learning for our students, development and dissemination of new educational materials, and dissemination of X-ity research results throughout the technical community.

The SecureCore project will investigate and design a secure integrated core architecture for trustworthy operation of mobile computing devices consisting of: a security-aware general-purpose processor, a small security kernel and a small set of essential secure communications protocols. The research will use a "clean slate" approach to define a minimal set of fundamental architectural features required for such a secure core, for use in resource-constrained, ubiquitous computing platforms exemplified by secure embedded systems (e.g., computer in a heart monitor), pocket devices (e.g., contact-less smart card), and mobile computing devices (e.g., handheld web-enabled computer). This approach shows what is possible when security is designed in at the beginning rather than added as an after-thought. It also changes the design paradigm from an emphasis on performance to one on trustworthy, dependable operation. The goal is to achieve the desired security levels without compromising performance, size, cost, energy consumption, or usability. Threat models will be re-examined in the new context of continuously networked commodity devices and Internet-scale epidemics such as DDoS, worms and viruses. The broader impact is to provide the scientific basis for trustworthy computing, communications and storage in pervasive computing environments. SecureCore impact will be immense if its architecture influences the design of future trustworthy commodity products, as well as the curriculum for computer hardware and software engineering education.

This research aims at establishing new theoretical foundations for nonlinear optimization of communication systems, developing efficient and distributed solution algorithms, and applying the methodologies to enable next generation broadband access networks. An important goal is to transfer the elegance of mathematical models and analysis to practical communication system design, with significant impacts on economics and ways-of-life in the society through collaboration with several major companies. Furthermore, two new courses are developed on optimization methodologies for communication systems. Using a just-in-time pedagogical approach and a modular structure, these courses traverse the disciplinary boundaries among electrical engineering, computer science, and operations research, and the traditional divide between physical layer and networking layers.

The investigation utilizes the power of recent developments in nonlinear optimization to tackle a much wider scope of problems in the analysis and design of communication systems than what the traditional linear programming methodologies allow, touching every layer of the layered network architecture, making practical impacts to real world deployments, and leading to a new intellectual foundation for communication systems. There are two major thrusts of research on several indispensable and interdependent areas in wireless and wired communications. First is information-theoretic limits characterized and computed using optimization methods. The investigator develops a Lagrange duality approach to prove, bound, and compute channel capacity and rate distortion functions for single and multiple terminal systems. Second is network resource allocation in the utility maximization framework, including analysis of Internet protocol of TCP congestion control and it's interact ional with other protocols as distributed algorithms solving implicit network utility maximization problems. The 'layering as optimization decomposition' approach is developed to provide a unified view on disparate problems in communication networks.

In large and complex communication networks, architectural decisions regarding functionality allocation are extremely important. The time is ripe for building a scientific foundation for network architectures, both to capitalize on unique clean-slate design opportunities (such as GENI and MANET) and to guide the evolution from existing network architectures to new ones. Such a foundation can lead to highly efficient, robust, and scalable protocols that could have a significant impact on the communications industry.

The recent successes of understanding protocols as optimizers and layering as mathematical decompositions offer a promising starting point for such an analytic foundation one that is conceptually unifying, mathematically rigorous, and practically relevant. However, there is still much work to be done in developing an analytic foundation for network architectures. This research focuses on three main thrusts:

Alternative architectural choices: Past mathematical results have focused on one architecture derived from a particular decomposition. There is in fact a wide range of alternative decompositions that result in different scalability, convergence, and complexity tradeoffs. This research systematically explores architectural choices using appropriate decompositions.

Stochastic network dynamics: This research develops new architectural designs taking into account stochastic (rather than deterministic) network dynamics, which are critical in modeling real systems and in developing high-performance network architectures.

Non-convexity and robustness: Non-convexity persists in real networks, which could lead to instability, poor performance, and impractical computational complexity. Nonetheless, most past results have been derived only for the convex case. This research explores architectural choices that are robust to non-convexity.

In large and complex communication networks, architectural decisions regarding functionality allocation are often more important than the details of resource allocation algorithms themselves. This NSF-funded project aims to develop a scientific foundation for designing network architectures by building upon recent successes in understanding protocols as optimizers and layering as mathematical decompositions. In particular, the PIs at five institutions collaborate to conduct a wide range of closely-connected research activities that substantially improve upon the state-of-the-art. Starting from a convex optimization formulation of the architecture design problem, the project investigates a wide range of alternative decompositions that provide different scalability, convergence, and complexity tradeoffs. The PIs then determine whether the properties of these alternative architectures continue to hold under stochastic network dynamics and non-convex objectives and constraints, and develop new architectural designs from a careful study of such dynamics. Mathematically, this project leads to a long-overdue union between network optimization and stochastic networks theory, and enables a systematic approach to leverage advances in general non-convex optimization.

Broader Impact: This project has clear synergy with the NSF's GENI initiative. The research provides a strong, analytic foundation for the design of future network architectures, including clean-slate solutions that deviate from todays Internet. The exploration of new ways to decompose functionality, with the influence of network dynamics and non-convexity in mind, will result in new protocols and mechanisms that can be evaluated in the GENI infrastructure.

With this instrumentation grant, the principal investigator will build a realistic access and home networking environment in Princeton's Networked End User Lab (NEULab) including a DSL access system, a cable modem access system, and a home network with triple screens: HDTV with set-top box, computer, and a variety of mobile devices. This testbed will be connected to national backbone testbed VINI via GigE links and a configurable router.

The PI will run a variety of experiments, based on theoretical foundation and in turn shaping the development of theory, on network architectures, protocols, algorithms supporting media-rich triple-play applications over constrained last hop and heterogeneous home networks. Through this proposal, several key parts of NEULab will be established, especially on DSL access network, cable modem access network, and triple-screen home network. The key equipments include DSLAM, CMTS, Spirent channel emulators, copper-farm, home gateways, two stages of switches, and consumer electronics with WLAN capabilities.

Intellectual Merit: Existing mathematical theories and algorithms developed in the following areas will be validated or falsified, and future ones inspired by the proposed testbeds: Broadband access fiber/DSL networks, P2P content distribution, content-aware networking, distributed scheduling algorithms, joint power control and scheduling, stochastic network utility maximization, and green information technology. Open issues involving metrics that are difficult to be analytically characterized, such as delay, jitter, and rate of convergence, will also be addressed. A list of 9 challenging questions that can be answered in the testbed is provided under these 7 research areas.

Broader Impacts: This proposal represents a strategy built on top of the PI?s industry collabora- tions and technology transfers to accelerate the transfer of theory into practice, through a set of experimental platforms under the umbrella of NEULab within Princeton University. The PI will also actively involve undergrad students in the construction and running of the experimental facilities through their independent work and undergrad theses, and hold summer undergraduate program open to 10 undergrads outside Princeton every year.

Networks stand at the center of our society, including social networks in virtual online space and technology networks among communication devices. Making socio-technological networks robust is becoming a paramount concern for national security, disaster relief, and economic stability. This project brings together a truly
inter-disciplinary team to develop the fundamental research methodologies and perform large-scale human subject experimentations towards this goal.

Intellectual Merit: (1) Developing Foundational Tools for Robust Networking. We draw from a suite of mathematical and statistical tools on two driving applications: (i) robustness against shocks, from the angles of social structures, policy influence, and communication recovery, and (ii) topology's impact on information value and propagation. (2) Interacting Across Disciplinary Boundaries. This team consists of four faculty members from three departments: Electrical Engineering, Sociology, and Political Science. Collectively the researchers draw upon expertise ranging from large-scale, social-network-based human behavior study to stochastic optimization over heterogeneous communication devices. (3) Bridging Theory-Practice Gap. A major bottleneck to social network study is the lack of an experimental testbed involving both innovative research agenda and human subjects. There are two sets of unique experimental platforms developed by the team: Online Gaming Community and Sharing Mart.

Broader Impacts. In addition to innovations in curriculum development across three departments, this team also actively reaches out to a variety of communities, from Non-Government-Organizations to high school students and online gamers, from major companies in the communication networking sector to undergraduates interested in the intersection between social sciences and engineering.

Current wireless network architectures are based on interference avoidance, which advocates eliminating simultaneous transmissions to avoid collisions at the receivers. However, this design principle is largely an artifact of design simplification. In contrast, if neighboring nodes pool their resources, and cooperate in their signal transmissions, the network could turn interference to its advantage for potentially many-fold increase in network capacity. This cooperative viewpoint necessitates revisiting networking research?s foundations, which are being addressed with a two-part strategy:

1. Network-centric Cooperative Signal Design: Cooperative signaling injects ?network? into signal design, thereby breaking conventional boundaries. Nodes have to understand how their transmissions will be perceived, decoded, suppressed, cancelled, enhanced or forwarded by other nodes. This fundamental shift in signal design (from conventional point-to-point PHYsical layer) is being addressed by developing capacity bounds, distributed codes and messaging protocols for scalable cooperation.

2. Signal-centric Cooperative Network Design: The converse to network-inspired signal design is ?signal-centric? network design. Network resource allocation and control have to be cognizant of signal-level interactions between groups of cooperating nodes,? breaking conventional design boundaries in network protocol design. This foundational change is leading to completely new problem formulations in scheduling, routing and protocol design to harness cooperative signal-scale gains.

The project goals are nothing short of rewriting networking fundamentals. By questioning the basic design paradigms, we expect the project will impact research in multiple communities. Our experiment codes and measurements will be open-sourced as community asset. We will also establish a unique inter-university education program including joint advising and collaborative experiments.

There has been no shortage of headline news on Internet access pricing in 2010 and 2011. From AT&T and Verizon shifting to usage-based pricing for wireless access to FCC's revealing the National Broadband Plan, and from Comcast-Netflix/Level3 battle on two-sided pricing to FCC's 2010 December statement on pricing innovations, the Internet is witnessing the start of a transformative period in the interplay between access pricing and the technology of networking.

The technical core of this project is organized around four fundamental questions: (1) How much to charge? The debate between flat-rate and usage-based pricing renews with fresh perspectives. (2) How to charge? Should the price charged depend on the time of bandwidth consumption or congestion condition of the network? (3) Whom to charge? When will content/application producers find incentives to pay for higher data rate or heavier bandwidth consumption by consumers? (4) What to charge? What kind of new service classes can be invented, especially in heterogeneous wireless networks with multiple platforms co-existing?

The unique features of this project include extensive participation from diverse sectors in the networking industry, implementation of prototypes and trials, and access to and dissemination of data. It combines the collection of fresh, large-volume of empirical data with rigorous design and prototype implementation. The project goes all the way from data analysis through optimization algorithms, to proof-of-concept demos and trials, eventually to practical impact on public policy and ISP business decisions, thus closing the loop in the study of network pricing.

Intellectual Merits: While we sharpen and apply a variety of tools from optimization theory, microeconomics, game theory, and statistics, the challenges arising out of these social issues also demand the development of new methodologies, such as supply chain contracts for multi-platform, two-sided pricing with conflicting interests of content providers and Internet service providers (ISPs). Furthermore, the interactions between technology evolution and economic policies are mutual: new enabling technologies such as femtocell raises new questions on the interaction between engineering artifacts and pricing structures.

Broader Impacts: The proposal is driven by timely and important questions faced by policy-makers, networking industry, and broadband consumers: (1) Who will pay for the estimated cost of $350B in the next decade to enable universal coverage of broadband services in this country? (2) Can pricing mechanisms be leveraged by the ISP as a practical approach to network management and new service class be created that is net-neutrality compatible? (3) How to regulate the nonstop surge of bandwidth demand to create win-win for both the ISPs and consumers? Furthermore, the project presents unique opportunities for undergraduate curriculum development, extensive industry participation and impact, and unconventional community outreach, both within US and across the world.

This project supports workshop travel and dissemination of workshop results for an upcoming workshop on complex engineered networks. Complex engineered networks are everywhere: power grids, Internet, transportation networks, and others. They are being used more than ever before, and yet our understanding about them remains limited. The Internet, wireless networks, and online social networks have shaped the modern society. Increasingly, critical, engineered, large-scale systems, such as transportation networks, power grids, and oil and gas distribution systems, are being enhanced and optimized by state monitoring and dynamic controls through sensor and cyber mechanisms. These networks have evolved into complex systems with behaviors and characteristics that are beyond the characterizations and predictions possible by the traditional modeling, analysis and design approaches.

The workshop will bring together experts from the academia, national laboratories, government, and industries to assess the recent trends, state-of-the-art, and impending challenges in modeling, predicting and controlling the behaviors of these complex networks to gain better performance, efficiency, and robustness. The objectives of the workshop include:

- Identify transformative research challenges and directions in the field of large-scale, complex engineered networks and interconnected physical systems of sensors and instruments, such as the power grid and communications networks.
- Assess the state-of-the-art, future trends, and important opportunities and challenges in the theory, design, analysis, tools, and applications of complex interconnected systems research in government, industry, and academia.
- Identify strategies for inter-agency collaborations at the federal level to enable different communities to carry out joint efforts, leverage ongoing activities, accelerate new discoveries, and enable technology transfers to societal impact in the research field of complex networks and interconnected systems.

Broader Impact: Complex systems occupy critical roles in our society but their performance across a full set of operating conditions is usually at best poorly understood. Formal mathematical analysis may give insight into the operation of system components or into the operation of simplified system models, but is seldom capable of exactly modeling actual code. Testing of complex systems often misses unexpected and undesirable behaviors resulting from cross-system interactions. Program module (unit) testing is effective in checking for gross programming errors across a specified set of inputs but often fails for inputs generated by these behaviors. Dynamic whole system behaviors such as oscillations, spreading overloads, and cascading security failures are not discoverable via unit testing. Exhaustive testing is often either not possible or prohibitively expensive in terms of time or resources. Better understanding of how to couple mathematical analysis and testing for the purposes of rapid and rigorous characterization of complex systems would have broad societal impact. The workshop is a joint undertaking between NSF, DoE and AFOSR via the Networking and Information Technology Research and Development (NITRD) Program and the Large Scale Networking (LSN) working subcommittee.

The FCC seeks to connect 19 million unserved Americans to broadband by 2020. These rural areas have yet to be fully connected to the Internet due to wireline infrastructure costs which exceed potential revenue opportunities. Even in heavily-populated environments with sufficient wireline infrastructure, capacity issues remain in congested stadiums, disaster recovery zones, and public transportation. Each aforementioned access challenge seemingly is well-suited for wireless mesh networks, but have yet to be fully solved. However, recently, there has been a sizable growth in radios operating in diverse frequency bands (e.g., TV white spaces) with emerging multi-antenna schemes. In this project, multi-user beamforming and diverse frequency bands are leveraged to significantly build upon the flexibility originally sought by mesh networks. In doing so, frequency-agile beamforming mesh (FabMesh) networks seek to truly scale in complexity and cost according to the user population and traffic demand. The work includes three key innovations: (i) client-side, beamforming-aware, and frequency-agile protocols to improve performance and reliability of clients, using contextual information and advanced physical layer techniques, (ii) analysis of spatial reuse and capacity for media access control in mesh networks which leverage multi-user beamforming, and (iii) scalable network deployments which leverage multi-user beamforming along the backhaul and adaptation across multiple frequency bands according to network demand. The project includes a number of hands-on courses for university students at all levels, "just in time" pedagogical approaches to thousands of online students, outreach to under-represented students and communities, and key industrial collaborations to accelerate the commercial adoption of FabMesh networks.

The National Science Foundation (NSF) is pleased to announce the selection of Mung Chiang , the Arthur LeGrand Doty Professor of Electrical Engineering at Princeton University, to receive its 2013 Alan T. Waterman Award. Dr. Chiang is also an associated faculty of Computer Science and an affiliated faculty of the Department of Applied and Computational Mathematics at Princeton.

The Waterman Award is the National Science Foundation's (NSF) highest honor. The annual award recognizes outstanding researchers under the age of 35 in any field of science or engineering that NSF supports. In addition to a medal, this year's awardee will receive a $1 million grant over a five-year period for further advanced study in his field.

Professor Chiang, is the founder of the Princeton EDGE Lab, which bridges over the theory-practice divide in networking through collaboration across many disciplinary boundaries as well as the academia-industry boundary. His team constantly re-examines the mathematical crystallization of engineering artifacts in networking. His research investigates an evolving set of projects spanning the modeling, analysis, and design of networks, both technological and human ones. Prof. Chiang also received the 2012 IEEE Kiyo Tomiyasu Award -for demonstrating the practicality of a new theoretical foundation for the analysis and design of communication networks', a U.S. Presidential Early Career Award for Scientists and Engineers in 2008, an Office of Naval Research Young Investigator Award in 2007, and a National Science Foundation CAREER Award in 2005. He was named as an MIT Technology Review TR35 Young Innovator in 2007, and was elected an IEEE Fellow in 2012.

Mobile phones and tablets are the most widely-used wireless communication devices nowadays. Video already represents the majority of mobile traffic and is expected to grow significantly in the coming years. Network operators are already facing shortage of bandwidth to support such a huge amount of traffic, despite the availability of newer cellular communication technologies. A solution to increase the availability and the efficiency of wireless communication technologies is given by cognitive radio networks (CRNs). Enabled by adaptive communication protocols, CRNs have the capability to sense a wide range of the spectrum and the agility to make use of the available resources dynamically. Accordingly, they can reclaim unused spectrum (i.e., whitespace) for wireless communications while avoiding interferences with between licensed and unlicensed users. However, video delivery over CRNs presents several challenges related to the highly-varying nature of the channel, the presence of misbehaving users, and the dynamic availability of heterogeneous resources.

This project addresses such challenges and makes CRNs suitable as a platform to provide ubiquitous wireless video. The research takes a flexible approach that is applicable to diverse regulations across national boundaries and specifically targets mobile devices. It helps create a cognitive phone, i.e., a smartphone with cognitive radio capabilities, to bridge the gap between the technologies behind CRNs and real applications. The project builds on two major research thrusts. First, it adopts spectrum crowd-sensing as a means to model the availability of whitespace at multiple scales and support long-lived communications. Such an approach enables novel solutions to accurately characterize the channel and enforce the policies established by the communication authorities. Second, it leverages adaptive mechanisms as foundations to efficiently deliver video streams to end users. These mechanisms are implemented through streaming protocols and components in the network infrastructure that provide video content with a target quality of experience. The project also integrates synergistic activities between the United States and Finland in education, industry collaboration, and entrepreneurship.

The past 15 years have seen the rise of the cloud, along with a rapid increase in Internet backbone traffic and more sophisticated cellular core networks. Some of the responsibilities of these: (1) data centers, (2) backbone IP networks, and (3) cellular core networks, are now descending to be among, or near, the end users, i.e., to the edge of networks. Fog networking is an architecture that uses one or a collaborative multitude of end-user clients or near-user edge devices to carry out a substantial amount of storage, communication and management. Engineering artifacts and applications that reflect such an architecture include 5G, home/personal networking, and the Internet of Things (IoT). It has thus become both feasible and interesting to ask the question: "What can be done on the network edge?" Can it carry out a substantial amount of storage (rather than storing data primarily in large-scale data centers), communication (rather than routing traffic always through the backbone network), and network measurement and control (rather than controlling primarily at gateways like those in the LTE Core)? Potential benefits of fog networking include real-time processing, client-centric objectives, pooling of local resources, rapid innovation with affordable scaling, and feasibility to operate on encrypted and multipath traffic.

There is no shortage of challenges in fog networking, including the following to be tackled in this project: traversing the boundary between centralized and distributed system architectures, steering the global behavior caused by collective client actions, incentivizing client participation, and using redundancy to achieve resilience on the network edge. Among a large and diverse set of topics in fog networking, this project focuses on two themes: (1) Client-driven measurement and inference, including real-time inference of network congestion conditions. Clients can combine local measurements from multiple sources to infer congestion in real time and use these insights to, for instance, optimally preload content at uncongested times. Implementation is achieved by turning client-side SDKs from an app development tool to a network control element. (2) Client-based control and configuration, including control of network connectivity and secure storage. On a fast timescale, client/edge devices can actively optimize their network connectivity by switching between heterogeneous networks, while on a longer timescale, they can relieve network congestion by selectively throttling their data rates. Beyond network connectivity, client-based software can also enhance storage security and reliability by scrambling, shredding and spreading data to different storage spaces.

Broader Impacts: Among this project's industry collaboration, curriculum development, mentoring and outreach are the following highlights. (1) Fog Consortium. Fog networking has the potential to tip the balance of power in the overall IT ecosystem. The PIs help create a Fog Industry-Academia Consortium, which will promote the ideas of fog networking and host outreach events and internship matching open to academia and industry. (2) MOOC. The PIs will offer a new course on "Fog Networking and the Internet of Things," both online and in in-person classes. (3) Community outreach. The PIs will maintain a research website, including a database of papers on fog networking, that is currently hosted at fogresearch.org.

Internet censorship consists of restrictions on what information can be publicized or viewed on the Internet. According to Freedom House's annual Freedom on the Net report, more than half the world's Internet users now live in a place where the Internet is censored or restricted. However, members of the Internet Freedom community lack comprehensive real-time awareness of where and how censorship is being imposed. The challenges to achieving such a solution include but are not limited to coverage, scalability, adoption, and safety. The project explores a linguistically-informed approach for measuring and circumventing Internet censorship.

The research takes a new perspective on the problem by investigating a hybrid method for censorship detection and evasion from the lens of linguistic analysis. The team develops new models to measure Internet censorship, investigates mechanisms to circumvent censorship using linguistic techniques, conducts communication and social network measurements of censored content. Active Sensing and natural language processing techniques, in conjunction with machine learning and optimization, invigorates new research directions in Internet Freedom and produces new high quality data and tools available for public use. This new allogamy between computer science, information security, network analysis and linguistics provides the foundation for evolution of anti-censorship technologies. The research contributes to a number of fields including Internet censorship, privacy and online information retrieval, as well as computational social science by modeling and analyzing the phenomenon of censorship using the signal available in language. The broader contribution includes wide dissemination of the research results via peer-reviewed publications, special topic courses and workshops. Additional benefits include providing graduate and undergraduate researchers with significant experience of highly practical work on a difficult interdisciplinary problem. Significant gains are obtained in recruitment of minority students through research training in computer science and linguistics.