  The cognitive interference channel models cognitive overlay radio systems,
where cognitive radios overhear the transmission of neighboring nodes. Capacity
for this channel is not known in general. For the Gaussian case capacity is
known in three regimes, usually denoted as the "weak interference", "very
strong interference" and "primary decodes cognitive". This paper provides a new
capacity result, based on rate-splitting of the primary user's message into a
public and private part and that generalizes the capacity results in the "very
strong interference" and "primary decodes cognitive" regimes. This result
indicates that capacity of the cognitive interference channel not only depends
on channel conditions but also the level of cooperation with the primary user.
