The Wideband Slope of Interference Channels: The Large Bandwidth Case

It is well known that minimum received energy per bit Eb/N₀|_min in the interference channel is -1.59 dB as if there were no interference. Thus, the best way to mitigate interference is to operate the interference channel in the low-signal-to-noise-ratio ( SNR) regime. However, when the SNR is small but nonzero, Eb/N₀|_min alone does not characterize performance. Verdu introduced the wideband slope S₀ to characterize the performance in this regime. We show that a wideband slope of S₀/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 S₀/S_{0, no interference} ≤ 1/2 for large number of users K.