Opportunistic interference alignment in heterogeneous two-cell uplink network

Degrees of freedom (DoF) of heterogeneous two-cell interfering uplink network is investigated in this paper. In each cell, there is one base station (BS) equipped with M antennas and arbitrary number of users equipped with different number of antennas (smaller than M). Suppose k and l active users are selected to communicate with the two BSs, respectively, it is shown that the DoF of k + l is achievable. A distributed opportunistic interference alignment scheme is then proposed which can obtain the optimal achievable DoF of the network. Numerical result shows that the scheme outperforms other existing schemes in terms of achievable sum rate.