New uplink opportunistic interference alignment: An active alignment approach

In this paper, we propose two new opportunistic interference alignment (IA) schemes to mitigate interference in the K-cell uplink interference channel. Unlike the existing schemes that basically rely on the channel randomness to achieve asymptotical IA for all cells, the proposed schemes employ an active alignment approach to increase the possibility for perfect partial IA for one cell within the network. Specifically, each user adopts the active alignment transmit beamforming such that the user-generated interference is perfectly aligned along the preferred reference interference direction at one of the base-stations (BS) in other cells. With this approach, our schemes increase the chance to obtain degrees-of-freedom gain even with a small number of users. In addition, several new user selection schemes are proposed, and the BS receiver is optimized to enhance performance. Extensive simulations are conducted, and the results show that the proposed schemes outperform the state-of-the-art under the considered scenarios.