Full-space spectrum-sharing strategy for TDD/FDD massive MIMO cognitive radio systems

This paper presents a new spatial spectrum-sharing strategy for massive multiple-input multiple-output (MIMO) cognitive radio (CR) systems, where two CR base stations (CBS) are employed at the adjacent sides of each cell to provide a full-space coverage for the whole cell. Thanks to the high spatial resolution of massive antennas, CRs are distinguished by their angular information and their uplink/downlink channels are also represented with reduced parameter dimensions by the proposed two-dimensional spatial basis expansion model (2D-SBEM). To improve the spectral efficiency and the scheduling probability of CRs, a greedy CR scheduling algorithm is designed for the dual CBS system. As the proposed strategy is mainly based on angular information and since the angle reciprocity holds for two frequency carriers with moderate distance, it can be applied for both TDD and FDD systems.