Capacity Enhancement Using Cooperative Distributed Antenna System in Downlink High-Speed Train Environments

In order to improve the system capacity of distributed antenna system (DAS) in downlink high-speed train (HST) environments, this paper presents a power allocation scheme for remote antenna units (RAUs) based on the cooperative distributed antenna system (CDAS). The investigated power allocation scheme exploits the channel state information (CSI) between RAUs and vehicle-mounted relay (VMR). Based on the CDAS-CSI power allocation, a corresponding RAU selection algorithm is introduced to quickly find the suboptimal solution that maximizes the channel capacity and to optimize the number of RAUs in CDAS. Simulation results show that the CDAS-CSI power allocation greatly improves the downlink system capacity compared to the cases of non-cooperation among RAUs and equal power allocation among RAUs.