Multiple Input Multiple Output (MIMO) systems have beenemerged as a new paradigm in wireless communications due to theirenormous capacity gains predicted by recent theoretical researchers.However, the majority work of the MIMO channel capacity assumes that the MIMO fading channels are frequency flat and time quasi-static, that means the fading channels have neither intersymbol interference (ISI) nor Doppler spread, which is not the case in many practical wireless systems with high data rate and user mobility.

In this talk, we will consider realistic MIMO channels undergoing triply

selective fading, that is, space-selective, time-selective and frequency-selective fading. We demonstrate that, besides spatial and temporal correlations, there exists ISI inter-tap correlations due to

irregular delay spreads in frequency-selective fading. This ISI inter-tap correlation has been largely overlooked but it has significant impact on channel capacity and transceiver design. We will present both theoretical and simulation results for the ergodic capacity and outagecapacity of MIMO triply selective fading channels. Our results show that (1) the frequency-selective channel usually have smaller ergodic capacity than frequency flat channel, which is different from the established results in the literature; (2) although time variation has no influence on ergodic capacity, it has significant impact on the outage capacity; (3) MIMO channels have four-dimensional diversities which consist of transmit, receive, Doppler and multipath diversities.

Chengshan Xiao received the B.S. degree from the University of Electronic Science and Technology of China (UESTC), Chengdu, China, in 1987, the M.S. degree from Tsinghua University, Beijing, China, in 1989,and Ph.D. degree from the University of Sydney, Australia, in 1997, all in electronic engineering.

Dr. Xiao was a lecturer at Tsinghua University, a Senior Member ofScientific Staff at Nortel Networks at Ottawa, Canada, and an Assistant

Professor at the University of Alberta, Canada. He is currently a faculty member at the University of Missouri-Columbia, Missouri, USA.

Dr. Xiao's research interests include wireless communications, signal

processing, multidimensional and multirate systems, and nonlinearcontrol. He has published more than 80 papers in international journals and conferences. He holds 3 US patents in wireless communications area.Two of his algorithms have been implemented into Nortel's base station radios with successful technical field trials and network integration.

Dr. Xiao is an Associate Editor for the IEEE TRANSACTIONS ON WIRELESS

COMMUNICATIONS, and the IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY. Previously, he was an Associate Editor for the IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS-I, and the International Journal of MULTIDIMENSIONAL SYSTEMS AND SIGNAL PROCESSING. He is currently the Vice Chair of Technical Committee on Personal Communications (TCPC) of IEEE Communications Society.