  We consider interference alignment (IA) over K-user Gaussian MIMO
interference channel (MIMO-IC) when the SNR is not asymptotically high. We
introduce a generalization of IA which enables receive diversity inside the
interference-free subspace. We generalize the existence criterion of an IA
solution proposed by Yetis et al. to this case, thereby establishing a
multi-user diversity-multiplexing trade-off (DMT) for the interference channel.
Furthermore, we derive a closed-form tight lower-bound for the ergodic mutual
information achievable using IA over a Gaussian MIMO-IC with Gaussian i.i.d.
channel coefficients at arbitrary SNR, when the transmitted signals are white
inside the subspace defined by IA. Finally, as an application of the previous
results, we compare the performance achievable by IA at various operating
points allowed by the DMT, to a recently introduced distributed method based on
game theory.
