On the Diversity and Multiplexing Tradeoff for MIMO Links with Imperfect CSIT

Multiple antennas can be used for increasing the packet reliability (spatial diversity) or the spectral efficiency (spatial multiplexing) in wireless communication systems with slow fading. Zheng and Tse showed that both types of gains can be simultaneously obtained for a given multiple antenna channel, but there is a fundamental tradeoff between spatial diversity and spatial multiplexing. They considered the case of no CSIT but perfect CSIR. In this paper, we focus on the role of channel state information at the transmitter (CSIT) on the diversity multiplexing tradeoff. When there is perfect CSIT, there will be no packet outage in slow fading channels through proper rate adaptation and hence, the diversity order can be regarded as infinity. However, perfect CSIT is not realistic. Thus, we consider the diversity and multiplexing tradeoff with imperfect CSIT for slow fading MIMO channels. The imperfect CSIT is parameterized by the CSIT estimation error sigma(2)(Delta H). Hence, the results obtained are the generalizations of the Zheng-Tse results. We show that when SN R sigma(2)(Delta H) -> infinity as SNR -> infinity, availability of the imperfect CSIT does not improve the diversity multiplexing tradeoff.