— High-speed Internet access in subway and railway systems has been receiving more and more attention in recent years. A critical issue for such application is the ground to train communications. One potential solution is to place multiple repeaters along the track and multiple antennas on the roof of the vehicle and then establish multiple point to point links through the use of DS/SSMA. In this paper, we will show that the antenna/repeater assignment can significantly affect system performance when this solution is employed. We will then derive an optimal antenna assignment strategy that maximizes the system throughput. Simulation results will be provided to demonstrate the advantages of the proposed strategy, which can also be applied to the recently proposed information rain system.