State of the cognitive interference channel: a new unified inner bound

The capacity region of the interference channel inwhich one transmitter non-causally knows the message of theother, termed the cognitive interference channel, has remainedopen since its inception in 2005. A number of subtly differingachievable rate regions and outer bounds have been derived,some of which are tight under specific conditions. In thiswork we present a new unified inner bound for the discretememoryless cognitive interference channel. We show explicitlyhow it encompasses all known discrete memoryless achievablerate regions as special cases. The presented achievable regionwas recently used in deriving the capacity region of the linearhigh-SNR deterministic approximation of the Gaussian cognitiveinterference channel. The high-SNR deterministic approximationwas then used to obtain the capacity of the Gaussian cognitiveinterference channel to within 1.87 bits.