Adaptive pilot power allocation for distributed antenna systems with large-scale CSI

Pilot design plays a key role in the channel estimation of pilot-assisted multiple-input multiple-output (MIMO) systems. Power allocation is a momentous issue in the pilot design. In the literature, pilot power allocation among transmit antennas has not been investigated. This paper explores this issue by introducing discriminatory treatment of different channel parameters. Generally, the large-scale channel state information (CSI) is much easier to be obtained than the small-scale CSI because of its slowly-varying characteristics. In particular, under the assumption that the large-scale CSI is available, we propose an optimal adaptive pilot power allocation scheme among transmit antennas for the distributed antenna system (DAS) to maximize the lower bound of the downlink ergodic capacity. Moreover, the proposed scheme provides insight into how to choose from transmit antennas from another perspective. Simulation results demonstrate the validity and superiority of the proposed pilot power allocation scheme.