Stable Transmission in the Frequency-Selective MIMO Broadcast Channel

Traditional non-linear (dirty paper coding) and linear (beamforming) preceding techniques that maximize the sum rate in the multi-antenna broadcast channel often suffer severe performance degradation when the channel state information (CSI) at the transmitter is erroneous or outdated. This has motivated the recent development of a linear preceding algorithm that uses the channel distribution information (CDI) rather than channel state to provide more stable performance in time-varying environments. This paper extends the prior analysis by using simulations with measured multi-user multi-antenna broadband channel responses to examine the effect of frequency selective channel characteristics on the behavior of the traditional CSI- based strategies as well as the more recent CDI-based approach. The results show that the CDI-based beamformer can offer superior performance with reduced feedback communication requirements.