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Easing Spectrum Congestion and Efficient Wireless Access: Policy, Sharing, and Protocol Approaches

Event Date: April 24, 2014
Speaker: Dr. Vijay Subramanian
Speaker Affiliation: Northwestern University
Sponsor: Possible ECE faculty candidate
Time: 2:00pm
Location: EE 317
Contact Name: Dr. David Love
Contact Phone: 765-496-6797
Contact Email:

Large systems with strategic agents are typical for many problems facing the modern world such as designing efficient transportation systems, efficient and effective cyber physical systems, etc. The engineering problems to solve are challenging and require a multiple disciplinary approach. One such problem is enabling efficient usage of the country’s wireless resources in order to provide increased access of connectivity and services to the public.

In this talk we describe our research on three approaches at different time-scales to enable increased wireless access and yield efficient spectrum usage: impact of adding new spectrum, contract design for sharing of spectrum between incumbents and fast time-scale use of commons to enhance quality of service.

Allocation of spectrum is an important policy issue and decisions taken have ramifications for future growth of wireless communications. In this part of the talk we compare the social welfare obtained from the allocation of new spectrum under different alternatives: to licensed providers in monopolistic, oligopolistic and perfectly competitive settings, and for unlicensed access. For this purpose we use mathematical models of competition in congestible resources. Initially we assume that any new bandwidth is available for free, but we also generalize our results to include investment decisions when prices are charged for bandwidth acquisition.

In a limited form cellular providers have long shared spectrum in the form of roaming agreements. The primary motivation for this has been to extend the coverage of a wireless carrier’s network into regions with no infrastructure. As devices and infrastructure become more agile, such sharing could be done on a much faster time-scale and have advantages even when two providers both have coverage in a given area, e.g., by enabling one provider to acquire ``overflow" capacity from another provider during periods of high demand. This may provide carriers with an attractive means to better meet their rapidly increasing bandwidth demands. On the other hand, the presence of such a sharing agreement could encourage providers to under-invest in their networks, resulting in poorer performance. In the first part of the talk, we adapt the newsvendor model from the operations management literature to model such a situation and to gain insight into these tradeoffs. In particular, we analyze the structure of revenue-sharing contracts that incentivize both capacity sharing and increased access for end-users.

In the last part, we consider the problem of streaming live content to a cluster of co-located wireless devices that have both an expensive unicast base-station-to-device (B2D) interface, as well as an inexpensive broadcast device-to-device (D2D) interface, which can be used simultaneously. It is easily argued that cooperative device-to-device transmissions will enhance the streaming quality of all users while simultaneously reducing their base-station-to-device transmissions. Our goal is to incentivize such cooperation. Based on ideas drawn from truth-telling auctions, we describe a mechanism that achieves this goal via appropriate transfers (monetary or rebates) in a setting with a small number of devices. As the number of devices becomes large, and there is significant peer churn, we show that a mean-field game can be used to accurately approximate our system. Furthermore, the complexity of calculating the best responses under this regime is low. Time permitting, we will also discuss the implementation of the proposed system on an Android testbed, and illustrate its good performance using real world experiments.

The first part is joint work with Randy Berry, Mike Honig at Northwestern University. The second is joint work with Randy Berry, Mike Honig at Northwestern University, Thanh Nguyen at Purdue University, Rakesh Vohra at University of Pennsylvania, and Hong Zhao at Intel Corporation. The last part is joint work with Jian Li, Rajarshi Bhattacharya, Suman Paul, and Srinivas Shakkottai at Texas A&M University.

Vijay Subramanian received the B.Tech. Degree in Electronics Engineering from IIT Madras in 1993. Subsequently, he obtained M.Sc. (Engg.) degree in Electrical Communication Engineering from IISc Bangalore in 1995 and Ph.D. in Electrical Engineering from University of Illinois at Urbana-Champaign. He worked in the research arm of the Networks Business Sector of Motorola in Arlington Heights, Illinois, USA until May 2006. In May 2006, he moved to the Hamilton Institute of the National University of Ireland, Maynooth as a Research Fellow. During Summer 2010, he was a visiting researcher at LIDS MIT. From Nov 2010 to Oct 2011, he was a Senior Research Associate in the EECS Department at Northwestern University. Currently, he is a Research Assistant Faculty in the EECS Department at Northwestern University. His interests are in social networks, network economics, random graphs, communication networks, information theory and applied probability.