  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.
