Independent Signaling Achieves the Capacity Region of the Gaussian Interference Channel With Common Information to Within One Bit

摘要

The interference channel with common information (IC-CI) consists of twotransmit-receive pairs that communicate over a common noisy medium. Eachtransmitter has an individual message for its paired receiver, andadditionally, both transmitters have a common message to deliver to bothreceivers. In this paper, through explicit inner and outer bounds on thecapacity region, we establish the capacity region of the Gaussian IC-CI towithin a bounded gap of one bit, independently of the values of all channelparameters. Using this constant-gap characterization, the generalized degreesof freedom (GDoF) region is determined. It is shown that the introduction ofthe common message leads to an increase in the GDoF over that achievable overthe Gaussian interference channel without a common message, and hence to anunbounded improvement in the achievable rate. A surprising feature of thecapacity-within-one-bit result is that most of the available benefit (i.e., towithin one bit of capacity) due to the common message is achieved through asimple and explicit coding scheme that involves independent signaling at thetwo transmitters so that, in effect, this scheme forgoes the opportunity fortransmitter cooperation that is inherently available due to shared knowledge ofthe common message at both transmitters.