The Wideband Slope of Interference Channels: The Large Bandwidth Case

It is well known that minimum received energy per bit
Eb
/
N
₀
|
_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
/
N
₀
|
_min
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
.