The Wideband Slope of Interference Channels: The Small Bandwidth Case

This paper studies the low-SNR regime performance of a scalar complex K -user interference channel with Gaussian noise. The finite bandwidth case is considered, where the low-SNR regime is approached by letting the input power go to zero while bandwidth is small and fixed. We show that for all \delta>0 there exists a set with non-zero measure (probability) in which the wideband slope per user satisfies Slope<2/K+\delta . This is quite contrary to the large bandwidth case [ShenAHM11IT], where a slope of 1 per user is achievable with probability 1. We also develop an interference alignment scheme for the finite bandwidth case that shows some gain.