The Wideband Slope of Interference Channels: The Small Bandwidth Case

Abstract

This paper studies the low-SNR regime performance of a scalar complex K-user interference channel with the Gaussian noise. The finite bandwidth case is considered, where the low-SNR regime is approached by letting the input power go to zero, while the bandwidth is small and fixed. We show that for all δ > 0, there exists a set of channel coefficients with non-zero measure (probability), in which the wideband slope per user satisfies S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <; 2/K +δ. This is quite contrary to the large bandwidth case, 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 in wideband slope.