Linear MIMO Techniques in Multiuser Wireless Communications

• Applicant: Professor Dr.-Ing. Wolfgang K. Utschick
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2008 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 97748472

The recent research on MIMO systems in wireless communication systems has been concentrating on Costa’s Dirty Paper Coding, which is an elegant approach for – at least principally – achieving the theoretically bounds of two important performance measures for the vector BC and MIMO BC channel, namely the sum capacity and the weighted sum rate. Although theoretically very appealing, the DPC technique suffers from a couple of drawbacks; that are the very complex implementation, the performance loss if considering the suboptimal THP solution, and, which in many relevent scenarios might even be prohibitive for practical implementation, the requirement of very precise channel state information at the transmitter side of the respective communication links. Especially, the latter turns out to be a severe drawback in alternative communication scenarios, e.g. as in networks with high mobility applications, or alternatively for the interference channel scenario, where multiple spatially distributed MIMO systems interfere with each other during a network session or at the border of a cellular network. To this end, linear MIMO techniques which do not resort to DPC are very attractive candidates for the exploitation of the potential performance enhancements by spatial signal processing in wireless communication networks without the challenging requirements related with DPC and THP. However, interestingly enough, although linear MIMO techniques appear to be the natural extension of the fundamental beamforming techniques, which the successful evolution of space time processing even started with, the underlying optimizations generally turn out to be rather complicated, even more complicated than for the theoretically more demanding DPC, and a couple of problems with linear MIMO have remained unsolved until now. Taking into account the intrinsical challenges of linear MIMO signal processing the existing previous work mainly concentrates on suboptimal schemes based on the (block) diagonalization of the underlying multiuser MIMO channels or by imposing the constraint of separately decoded data streams without exploiting the potential of multiple cooperating receivers at the respective data sinks. In this proposed project, such restrictions will not be imposed, since the goal is rather to exploit the recently discovered duality results between the MIMO BC with Linear Precoding and the MIMO MAC with linear user separation. This new duality results will serve as the fundamental framework for a methodical treatment of linear MIMO systems in multiuser communication scenario and the design of respective algorithms.

• DFG Programme: Research Grants
• Participating Person: Dr.-Ing. Michael Joham