  A new achievable rate region is given for the Gaussian cognitive many-to-one
interference channel. The proposed novel coding scheme is based on the
compute-and-forward approach with lattice codes. Using the idea of decoding
sums of codewords, our scheme improves considerably upon the conventional
coding schemes which treat interference as noise or decode messages
simultaneously. Our strategy also extends directly to the usual many-to-one
interference channels without cognitive messages. Comparing to the usual
compute-and-forward scheme where a fixed lattice is used for the code
construction, the novel scheme employs scaled lattices and also encompasses key
ingredients of the existing schemes for the cognitive interference channel.
With this new component, our scheme achieves a larger rate region in general.
For some symmetric channel settings, new constant gap or capacity results are
established, which are independent of the number of users in the system.
