A new external limit to the capacity of interference channels

An interference channel is a communication network where two senders communicate with two receivers through a shared medium, in such a way that the flow of information over the first link (from the first sender to the first receiver) can impair the flow over the second link, and vice versa. If R1 and R2 are the rates of information transmission over the first and second link, respectively, the channel's capacity region is the set of pairs (R1,R2) which are jointly achievable in reliable communications. The problem of determining the capacity region has been solved only in some special cases, in particular in strong interference cases. A new outer bound on the capacity region of the Gaussian interference channel is demonstrated by means of the technique involving degradation of a modified channel by added noise. In those cases where the interference is of medium intensity, which in practice, are more common than strong interference cases, the new bound is significantly, tighter than previously known outer bounds.