Date: December 11, 2012
Speaker: Dr. Marco Moretti, Assistant Professor, University of Pisa
Location: EE Conference Room
We address the problem of margin adaptive scheduling in the downlink of an orthogonal frequency division multiple access (OFDMA) multiple-input multiple-output (MIMO) system. Optimal resource allocation in MIMO systems requires the joint optimization of: a) linear transmit and receive spatial filters, b) channel assignment and c) power allocation. This problem is not convex and its complexity becomes thus intractable already for small sets of users and subcarriers. To reduce the complexity of the problem at hand, we propose a novel heuristic strategy that partitions the users in different groups according to their average channel quality and addresses the original problem by solving a succession of lower-complexity allocation problems. The spatial dimension is employed to prevent multiple access interference from hindering the performance of the sequential allocation. To further reduce the complexity burden we introduce a linear programming formulation in combination with a waterfilling-based strategy to allocate channels and power to the groups of users. Numerical results and evaluation of the computational complexity show that, though suboptimal, in most cases the proposed algorithm manages to exploit in an original way the inherent multi-user diversity of multi-carrier systems to ease the task of resource allocation with a very limited performance loss from the theoretic optimum.
Marco Moretti graduated in electronic engineering at the University of Florence (Italy) in 1995 and received the Ph.D. degree in 2000 from the Delft University of Technology (The Netherlands). From 2000 to 2003 he worked as wireless communications senior researcher at Marconi PLC. He is currently assistant professor at the University of Pisa (Italy). He is author of more than 15 IEEE Transaction papers and several conference papers and is co-author of 3 books and 2 patents. His main research interests include resource allocation for multi-carrier systems, synchronization and channel estimation.