A Novel Scheme for Downlink Opportunistic Interference Alignment
  In this paper we propose a downlink codebook-based opportunistic interference alignment (OIA) in a three-cell MIMO system. A codebook composed of multiple transmit vector sets is utilized to improve the multiuser selection diversity. The sum rate increases as the size of the codebook grows. In addition, during the user selection, effective channel gain and alignment metric are combined to generate a novel criterion, which improves the system performance, especially at low SNR. Furthermore, a threshold-based feedback approach is introduced to reduce the feedback load in the proposed scheme. Both the analytical results and simulations show that the proposed scheme provides significant improvement in terms of sum rates with no feedback load growth and slight increase of complexity. 
Haijing Liu, Hui Gao, Wei Long, Tiejun Lv
cs.IT math.IT