The Wideband Slope of Interference Channels: The Large Bandwidth Case

TL;DR

This paper investigates the wideband slope of interference channels in the low-SNR regime, demonstrating achievable bounds using interference alignment techniques and establishing upper bounds for multiple users.

Contribution

It introduces the concept of wideband slope in interference channels and shows how interference alignment can achieve a specific slope, extending understanding of low-SNR performance.

Findings

Achievable wideband slope of 1/2 with interference alignment.

Upper bound of 1/2 for large number of users.

Performance characterization beyond minimum energy per bit.

Abstract

It is well known that minimum received energy per bit in the interference channel is -1.59dB as if there were no interference. Thus, the best way to mitigate interference is to operate the interference channel in the low-SNR regime. However, when the SNR is small but non-zero, minimum energy per bit alone does not characterize performance. Verdu introduced the wideband slope S_0 to characterize the performance in this regime. We show that a wideband slope of S_0/S_{0,no interference}=1/2 is achievable. This result is similar to recent results on degrees of freedom in the high SNR regime, and we use a type of interference alignment using delays to obtain the result. We also show that in many cases the wideband slope is upper bounded by S_0/S_{0,no interference}<=1/2 for large number of users K .