Achievable Rate Regions for Cognitive Radio Gaussian Fading Channels with Partial CSIT

We study the simplest version of Gaussian fading Cognitive Radio (CR) interference channel which comprises of two transmitter-receiver pairs. The primary transmitter (PTx) and primary receiver (PRx) are equipped with single antenna each whereas the cognitive transmitter (CTx) and the cognitive receiver (CRx) may be equipped with multiple antennas in our setting although this pair is also restricted to single stream transmission. The channel state information is partial such that each transmitter knows its channel to the PRx but has no information about its channel to the CRx. This contribution proposes two simple transmission strategies focusing the CR channels in the so-called "overlay paradigm" where the CTx not only transmits its own message but helps as well transmitting the primary message. In the first strategy, the primary message is independently encoded at the two transmitters whereas the same primary message encoding is used in the second strategy which not only allows the coherent signal combining at the PRx but also the possibility of complete interference cancellation at the CRx even in the limiting case when the CRx is equipped only with two antennas. The simulation results demonstrate that the proposed strategy with same primary message encoding shows considerable performance benefit over the strategy where the primary message is independently encoded at the two transmitters.