The cognitive Z channel

Abstract

This paper considers the so-called cognitive Z channel, where two users transmit two independent messages to their respective receivers through a Z interference channel. User 1 (primary user) interferes with receiver 2 while user 2 (secondary user) does not interfere with receiver 1. In addition, user 2 overhears the transmission of user 1 through a noisy channel, hence the term ‘cognitive’. Capacity bounds for such channel in different parameter regimes are obtained and the impact of such causal cognition is carefully studied. In particular, depending on the channel parameters, the cognitive link may not be useful in terms of the capacity region. Numerical examples are also given.