Capacity results for a class of deterministic Z-interference channels with unidirectional receiver conferencing

We study the Z-interference channel in which there is an additional orthogonal link from the interference-free receiver to the interfered receiver. We call this channel model the Z-interference channel with unidirectional receiver conferencing. We find the capacity region when the Z-interference channel belongs to the class of deterministic Z-interference channels studied by El Gamal & Costa in 1982. Our results show that in the presence of unidirectional receiver conferencing, it is still optimal for the interfering transmitter to use superposition encoding to control the amount of interference it causes. For the interference-free receiver, it is optimal to forward part of the decoded message over the orthogonal cooperation link. We further note that the same scheme is also optimal for another class of Z-interference channels studied by Liu & Goldsmith in 2009.