Interference alignment, carrier pairing, and lattice decoding

We discuss how to take advantage of the discreteness of signal constellations at the detector side, in various interference alignment schemes for which linear zero-forcing of the interference has been traditionally considered. We show that lattice decoding, with possible “generalized decision feedback equalization” preprocessing can achieve significant gains in symbol error rate at the detector output, at finite SNR. Furthermore, we discuss the effect of channel coefficient dynamics on the Cadambe and Jafar interference alignment precoding scheme, and point out the need of careful carrier pairing in order to limit these dynamics.