Multiuser MIMO in distributed antenna systems with limited feedback

Augmenting the central antennas of a cellular base station with remote radio units (RRUs) has the potential of providing more uniform coverage of the area served by the base station. In distributed antenna systems (DASs) these RRUs are connected to the base station via high bandwidth and low latency links, enabling coherent transmission from potentially all available antennas at the same time. Prior work has identified multiuser transmission over the entire distributed antenna array as a promising technique. In this work, we demonstrate the viability of zero forcing multiuser MIMO DASs with perfect channel state information (CSI) at the transmitter (CSIT) in an LTE simulation framework. Furthermore, the impact of imperfect CSIT, obtained via limited feedback, on the achievable transmission rates is investigated. Specifically, we modify previously derived feedback algorithms to exploit the large scale fading differences inherently existing in DASs.