Layering As Optimization Decomposition: Questions and Answers
Chiang,Mung
Princeton University
Low,Steven
California Institute of Technology
Doyle,John
California Institute of Technology
Calderbank,A. Robert
Princeton University
Network protocols in layered architectures have historically been obtained on an ad-hoc basis, and much of the recent cross-layer designs are conducted through piecemeal approaches. Network protocols may instead be holistically analyzed and systematically designed as distributed solutions to some global optimization problems in the form of generalized Network Utility Maximization (NUM), providing insight on what they optimize and structures of the network protocol stack.
In the form of 10 Questions and Answers, this paper presents a short survey of the recent efforts towards a systematic understanding of &096;&096;layering'' as &096;&096;optimization decomposition''. The overall communication network is modeled by a generalized NUM problem, each layer corresponds to a decomposed subproblem, and the interfaces among layers are quantified as functions of the optimization variables coordinating the subproblems. Furthermore, there are many alternative decompositions, each leading to a different layering architecture. Industry adoption of this unifying framework has also started. Here we summarize the current status of horizontal decomposition into distributed computation
and vertical decomposition into functional modules such as congestion control, routing, scheduling, random access, power control, and coding. We also discuss under-explored future research directions in this area. More important than any particular cross-layer design, this framework is working towards a
mathematical foundation of network architectures and the design process of modularization.
Mung Chiang is an Assistant Professor of Electrical Engineering, and an affiliated faculty of Applied and Computational Mathematics at Princeton University. He received the B.S. (Hon.) degree in electrical engineering and in mathematics, and the M.S. and Ph.D. degrees in electrical engineering from Stanford University, Stanford, CA, in 1999, 2000, and 2003, respectively. He conducts research in the areas of optimization of communication systems, theoretical foundations of network architectures, algorithms in broadband access networks, and information theory.
Professor Chiang has been awarded a Hertz Foundation Fellowship and received the Stanford University School of Engineering Terman Award for Academic Excellence, the SBC Communications New Technology Introduction contribution award, the National Science Foundation CAREER Award, and the Princeton University Howard B. Wentz Junior Faculty Award. He is the Lead Guest Editor of the IEEE Journal of Selected Areas in Communications special issue on Nonlinear Optimization of Communication Systems, a Guest Editor of the IEEE Transactions on Information Theory and IEEE/ACM Transactions on Networking joint special issue on Networking and Information Theory, and the Program Co-Chair of the 38th Conference on Information Sciences and Systems.