Two-Layer Beamforming for Virtual Cell in Ultra Dense Network

Virtual cell can be viewed as an effective way to solve the challenges in the ultra-dense network (UDN), however it suffers from severe and complex interference with the increase of cell density. In this paper, we exploit the similarity of interference channel among users, and assume a two-layer beamforming scheme to eliminate both intra-cell and inter-cell interference. To ensure the feasibility of the two-layer beamforming in UDN, we adopt a strategy to jointly optimize the virtual cell selection and user scheduling based on the interference channel similarity. Different from the user group schemes exploiting the channel similarity of users, we extend this similarity concept to the case of user grouping by interference channel. Analysis and simulation results conducted in virtual cell scenario confirm the improvements of the proposed scheme in complexity and performance aspects.