Wideband slope of interference channel: Finite bandwidth case

This paper studies the low-SNR regime performance of a scalar complex K-user interference channel with Gaussian noises under the assumption that the low-SNR regime is approached by letting input power P → 0 while bandwidth is fixed. First, a generalized Z-channel type of upper bound is derived. Using this bound, we show that for any δ >; 0, there exists a set of channels Us with non-zero probability whose sum slope S is bounded by S_TDMA + δ, which means that TDMA is nearly optimal. On the other hand, we develop an interference alignment scheme utilizing the differences between the phases of channel coefficients and show that for channels in a subset of U_δ^C with non-zero probability, this achievable scheme performs noticeably better than TDMA. And for both the upper bound and the lower bound, we allow circularly asymmetric inputs.This paper studies the low-SNR regime performance of a scalar complex K-user interference channel with Gaussian noises under the assumption that the low-SNR regime is approached by letting input power P → 0 while bandwidth is fixed. First, a generalized Z-channel type of upper bound is derived. Using this bound, we show that for any δ >; 0, there exists a set of channels U_δ with non-zero probability whose sum slope S is bounded by S_TDMA + δ, which means that TDMA is nearly optimal. On the other hand, we develop an interference alignment scheme utilizing the differences between the phases of channel coefficients and show that for channels in a subset of U_δ^C with non-zero probability, this achievable scheme performs noticeably better than TDMA. And for both the upper bound and the lower bound, we allow circularly asymmetric inputs.