The Wideband Slope of Interference Channels: The Infinite Bandwidth Case

It is well known that minimum received energy per bit Eb N0 ̨̨̨ min 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 power regime, that is in the limit of infinite bandwidth. However, when the bandwidth is large, but finite, 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. Index Terms Interference channels, wideband slope, interference alignment.