Multi-user Information Theory
Multiple input multiple output (MIMO) communication has been the focus of a lot of research which basically demonstrated that the capacity of a point to point MIMO link increases linearly with the number of transmit and receive antennas. Research focus has shifted recently to the role of multiple antennas in multiuser systems, especially broadcast scenarios (i.e., one to many communication) as downlink scheduling is the major bottleneck for future broadband wireless networks.
Scaling laws of broadcast channels
I am interested in the scaling laws of various multiuser broadcast techniques in the large number of users regime. I have recently considered the effect of spatial correlation among the transmit antennas on various broadcast techniques including dirty paper coding and various forms of random beamforming. It was shown that transmit correlation results in an SNR hit that depends on the broadcast technique used and the eigenvalues of the transmit correlation matrix.
Scaling laws of group broadcast channels
In a group broadcast setting, the users’ pool is divided into groups, each of which is interested in common information. Such a situation occurs for example in digital audio and video broadcast where the users are divided into various groups according to the shows they are interested in. I have recently considered the scaling laws of group broadcast in the large number of users and large number of transmit antennas regimes. As expected, group decrease with the number of users. Moreover, to achieve a constant rate per user, the number of transmit antennas should scale at least logarithmically in the number of users.