Antenna selection and RF preprocessing for MIMO systems

Speaker: Dr. Andreas Molisch, Mitsubishi Electric Research LabsAbstract: Multiple Input Multiple Output (MIMO) systems can significantly increase the capacity of a wireless link and improve the robustness of the link. However, an important factor limiting the adoption of MIMO is the increased system- and hardware complexity. The signal received (transmitted) at each antenna element requires a separate Radio Frequency (RF) demodulator (demod) chain, which is expensive. A way to mitigate this problem is antenna selection, where either one, or both, link ends choose the "best" out of available antennas, so that only L (instead of N) RF chains are required. This talk will give an overview of the performance of antenna selection schemes when used in conjunction with diversity or with spatial multiplexing. In ideal channels, full diversity order can be achieved, and also the number of independent data streams for spatial multiplexing can be maintained if certain conditions on are fulfilled. However, there is a reduction of beamforming gain, which can lead to a significant performance loss especially in correlated channels. We will then demonstrate that a preprocessing of the signals in the RF domain by an array of phase shifters can recover most of this beamforming gain. A discussion of the hardware nonidealities in the preprocessing scheme and their impact on the performance wraps up the talk.Bio: Andreas F. Molisch (Fellow, IEEE) is a senior researcher with Mitsubishi Electric Research Labs (Cambridge, MA), and professor for radio systems at Lund University, Sweden. Previously, he had worked at AT&T Bell Labs (NJ) and the Technical University of Vienna, Austria. His current research interests are wireless propagation channels, MIMO systems, and ultrawideband (UWB) systems. He has authored, co-authored, or edited four books, 11 book chapters, some 85 journal papers, and numerous conference contributions. He is inventor of more than 40 patents, has been chairman of various standardization and industrial groups in the area of MIMO and UWB, and received several awards.Host: Keith Chugg, chugg@usc.edu, x.07294

Location: Hughes Aircraft Electrical Engineering Center (EEB) - -248

Audiences: Everyone Is Invited

Contact: Mayumi Thrasher