Downlink MIMO performance evaluation for LTE/LTE-A indoor distributed antenna systems

Distributed antenna systems (DAS) are used to improve indoor coverage in cellular systems, which has been widely deployed in the current 2G and 3G mobile networks. In this paper, an indoor DAS solution will be provided, which can easily upgrade from the existing DAS to support multiple-input multiple-output (MIMO). In addition, the performance of different MIMO transmission modes will be discussed, including closed-loop spatial multiplexing and multiuser MIMO (MU-MIMO). Simulation results show that the imbalance effects in indoor scenario have significant impact on downlink MIMO performance. The antenna configurations should be carefully considered before they are deployed. For the scenarios when distributed antennas can not be co-located, attention should be given to MIMO modes and precoding codebook selection to optimize the performance.