A Three-Cell Coordinated Network MIMO with Fractional Frequency Reuse and Directional Antennas

In this paper, we propose three-cell network multiple-input multiple-output (MIMO) schemes to mitigate the inter-cell interference in a multi-cell system with each cell using the same spectrum. One fundamental question to apply the network MIMO technique in such a high interference environment is: how many cell should coordinate together to provide sufficient signal-to-interference plus noise ratio (SINR)? Consider interferences from the other coordinated groups, we find that on top of the tri-sector directional antenna and fractional frequency reuse (FFR), the network MIMO based on the proposed three-cell coordination strategy can outperform seven-cell based network MIMO with omni-directional antenna. We also consider the effect of different cell sectorings by using 120° and 60° beamwidths directional antennas.