Zero-Forcing for the Symmetric Interference Channel with Conferencing Encoders

A two-user Gaussian Interference Channel (GIC) is considered in which encoders are connected through noiseless links with finite capacities. New genie-aided upper bounds on the sum-capacity are developed which incorporate the capacities of the cooperative links. When the GIC is symmetric, with possibly different cooperation link capacities, the sum-capacity is characterized within 2.13 bits gap for all values of the channel parameters. In the achievable scheme, each transmitter sends a private and a common message, and zero-forces the part of the other transmitter's private message, communicated over the conference between the encoders.