  This paper focuses on two-cell multiple-input multiple-output (MIMO) Gaussian
interfering broadcast channels (MIMO-IFBC) with $K$ cooperating users on the
cell-boundary of each BS. It corresponds to a downlink scenario for cellular
networks with two base stations (BSs), and $K$ users equipped with Wi-Fi
interfaces enabling to cooperate among users on a peer-to-peer basis. In this
scenario, we propose a novel interference alignment (IA) technique exploiting
user cooperation. Our proposed algorithm obtains the achievable degrees of
freedom (DoF) of 2K when each BS and user have $M=K+1$ transmit antennas and
$N=K$ receive antennas, respectively. Furthermore, the algorithm requires only
a small amount of channel feedback information with the aid of the user
cooperation channels. The simulations demonstrate that not only are the
analytical results valid, but the achievable DoF of our proposed algorithm also
outperforms those of conventional techniques.
