Wideband slope in interference channels with imperfect CSI at transmitters

In this paper we investigate the wideband slope of a K-user interference channel. We show that delay-based inteference alignment can achieve a wideband slope of S₀/S₀ = 1/2, no interference independent of the number of users K, when the delays are known exactly. This result is similar to recent results on degrees of freedom in the high SNR regime. We also show that in many cases the wideband slope is upper bounded by S₀/S₀ ≤ 1/2, no interference for large number of users K. We then consider delay uncertainty at the transmitter side. We present a modified delay-based interference alignment scheme. Its achievable wideband slope can get arbitrarily close S₀/S₀ = 1/2, no interference-the best achievable wideband slope for the channel without delay uncertainty.