On the Performance of Downlink Transmission for Distributed Antenna Systems with Multi-Antenna Arrays

In distributed antenna systems (DAS), the scenario that each antenna port is a multi-antenna array with multi-user is far beyond thoroughly studied. In this paper, the performance of four extended methods for DAS downlink transmission are analyzed and compared in such a scenario, two of which are based on the block diagonalization (BD) algorithm, namely joint BD and intra BD method. The other two methods are joint time division multiplexing (TDM) method and central antenna system (CAS) method. Both theoretic analysis and insightful simulations are utilized to evaluate these four methods. Theoretic analysis shows that the intra BD method requires less channel state information at transmitter (CSIT) and has lower computational complexity and process latency. Simulation results show that the intra BD method suffers only a little performance loss compared with the joint BD method. Overall, the intra BD method is proved to be a best tradeoff which achieves high capacity with relatively low complexity when power constraints are considered.