A Water-Filling Algorithm for Distributed MIMO Systems in Underground Tunnels

Previous work has revealed that nonuniform power allocation schemes can significantly improve the performance of multiple-input-multiple-output (MIMO) systems in conventional environments. Here, we propose a water-filling scheme based on the multimode-waveguide model and customized for underground mines and tunnels that is suitable for use in conjunction with 4 ×4 distributed-MIMO systems. We show that employing this method significantly improves downlink capacity for different mobile locations in a typical underground environment. We have also studied the manner in which performance is affected as the separation between access-point antennas increases. These results provide useful guidance to deploy distributed and antenna-selection-based MIMO systems in underground environments.