Writing on Rayleigh faded dirt: a computable upper bound to the outage capacity

A transmitter may have non-causal knowledge of the interference signal being transmitted by another user. Recently, Tarokh and others have raised the possibility of exploiting this knowledge to increase the data rates of a cognitive radio. However, there is a difference between knowing the signal transmitted by the primary and the actual interference at our receiver since there is a wireless channel between these two points. This raises the interesting problem of finding the achievable rates for a compound Gel´fand-Pinsker channel. The problem was addressed recently in the work by Mitran et al, where the authors gave some upper and lower bounds to the achievable rates, with an emphasis on fading channels. But the upper bounds in that work are sometimes non-computable. In this work, we derive computable upper bounds on the outage capacity for a channel where the primary signal can be Rayleigh faded at our receiver.