Gaussian Interference Channel Capacity to Within One Bit

Abstract

The capacity of the two-user Gaussian interference channel has been open for thirty years. The understanding on this problem has been limited. The best known achievable region is due to Han-Kobayashi but its characterization is very complicated. It is also not known how tight the existing outer bounds are. In this work, we show that the existing outer bounds can in fact be arbitrarily loose in some parameter ranges, and by deriving new outer bounds, we show that a simplified Han-Kobayashi type scheme can achieve to within a single bit the capacity for all values of the channel parameters. We also show that the scheme is asymptotically optimal at certain high SNR regimes. Using our results, we provide a natural generalization of the point-to-point classical notion of degrees of freedom to interference-limited scenarios.

Cognitive Interference Alignment for Spectral Coexistence

“…This metric has been successfully used in [4,18] to approximate the capacity of two user interference channel and in [46] for multiple antenna scenarios considering two user MIMO interference channel.…”

Ergodic Interference Alignment With Delayed Feedback

“…Thus, they just send independent messages at t 1 and t 2 . After the channel changes, the transmitters can figure out that the channel condition in (3) and (4) is satisfied at the previous time t 2 due to delayed CSI feedback. Then, transmission phase 6 Transmission phase 2: If the previous time was t 2 , the transmitters send the following signals at time…”

“…After the output feedback signals are received, the transmitters realize that the previous time instant was t 2 at which the channel condition in (3) and (4) is satisfied and enters into transmission phase 2. In transmission phase 2, transmitter k sends the signal…”

Harnessing Interference with an Out-of-Band Relay: An Approximate Capacity Result

“…When interference is weak or very weak, using HK scheme for the IC limits the achievable rates for the common messages, since all common messages need to be decoded at interference link. We show that instead of decoding all common messages from the IC as in [9], with the OBR, part of the common messages from the interference link can be decoded from the OBRC to improve the rates and further mitigate interference. By deriving new outerbounds, we show that our scheme achieves rates that are within 1.14625 bits of the symmetric capacity.…”