Recent years have seen the advent of sophisticated multiple-input, multiple-output (MIMO) technology for communication networks. Achieving the substantial performance gains promised by such technology requires not only the development of suitable network protocols, but also rethinking aspects of the associated network architecture based on careful consideration of issues that transcend individual layers in the hierarchy. To date, most effort has focused on the physical and medium-access layers, emphasizing coding and multiplexing issues. However, there is an emerging appreciation that the issues at the higher networking layers are at least as important and equally rich, and that the associated broader view of MIMO network design challenge is critical to realizing the performance potential of this technology. The proposed research is aimed at precisely these challenges, and will start from fundamental principles to the develop key insights from which efficient and robust networking protocols and resource management algorithms will follow. With the strong interest in the development of standards such as 802.16 and 802.11n, among many others, such research is especially timely and the potential for practical impact is particularly high.
This broader research theme will be approached by investigating several specific questions and issues. Of central importance is the scheduling problem: given a MIMO link for delivering data to a collection of endusers, what are the fundamental tradeoffs between throughput, delay, reliability, fairness, and complexity achievable in such systems? In our preliminary research, we have established that fundamentally new spatiotemporal scheduling protocols can and must be developed, and that the structure of such protocols is strikingly different from those in their non-MIMO counterparts. In the proposed research, we will investigate issues ranging from how users should be selected in any given transmission interval, to how feedback should be exploited, to how training should be accomplished.
The research will further pursue the still richer problems when multiple MIMO links of this type are used in conjunction with one another, as is the case in any practical network. In such settings, cooperation and relaying become integral aspects of efficient scheduling and resource management, and the research will pursue the development of such algorithms in detail. Throughout our investigation, we will take into account the strong network dynamics, including multipath fading and shadowing, rapid fluctuations in user connectivity and populations, and the bursty nature of traffic in such networks.
Distinguishing features of our research include its emphasis on 1) stronger notions of optimality than have been considered to date; 2) its finer grain analysis beyond simple asymptotics; and 3) its tight integration of traditional information-theoretic and communication-theoretic treatments with queuing-theoretic, scheduling-theoretic and algorithm-theoretic treatments in the protocol design and analysis. Indeed, more generally the spectrum of issues to be investigated will require the coordinated application of a wide range of design and analysis tools, making the research highly interdisciplinary in nature. Indeed, these tools will be drawn from information theory, queuing theory, communication theory, graph theory, coding theory, algorithms and complexity theory, and estimation theory and machine learning.
Intellectual Merit: The proposed research will significantly advance the fundamental theory and practice of networking in systems exploiting MIMO technology, and to provide a solid foundation for the development of the higher performance networking infrastructure needed to enable a new generation of applications.
Broader Impacts: The proposed research is a highly education-centered activity with a focus around the professional and intellectual development of students. Through outreach efforts, the PI's will continue their strong commitment to involving in their research programs students from groups traditionally underrepresented in engineering. The PI's are also strongly committed to the integration of the results of this research into the curriculum, and in particular to new networking subjects under development at their respective institutions that specifically integrate network- and physical-layer design and analysis. Finally, the research program will help foster important new interlaboratory research collaboration between two academic institutions for which there is the potential for strong partnership, as well as with additional key industrial partners. In particular, the proposed effort will foster closer research and educational ties between OSU and MIT in the communication and networking area, and rapid transition of the resulting research results to practice through close interaction with the networking laboratories of Hewlett-Packard, Nokia, and General Electric, each of whom has a strong commitment to and track record of effective academic-industrial research collaboration. The PI's will strongly leverage these relationships, as well as earlier infrastructure investments, such as the interdisciplinary Center for Wireless Networking established by HP at MIT over the last several years to foster such collaboration both within and beyond MIT.
