A High Spectral Efficiency System Enabled by Free Window with Full Duplex

This paper studies the capacity issues of a wireless communication system that implements single channel full duplex（SCFD） communication at the base station（BS）, thereby the mobile stations share the channel via time division duplex（TDD）. The system makes use of the same setup as has been used in previous studies of SCFD, but unlike these previous systems, the new system uses water-filling to maximize the spectral efficiency of the uplink channel. The concept of a free window is introduced to the duplex model for measuring, intuitively, the effective bandwidth of the bi-directional communication. The capacity gain is calculated and numerical results show the advantage of the proposed system over that of conventional TDD.