In order to solve the resource allocation problem for the interference channel in a cognitive context, we evaluate the application of the superposition coding strategy at the secondary system for underlay multi-carrier cooperative cognitive radio. The objective is to maximize the sum rate of both primary and secondary systems, considering the interference threshold constraint and that the primary receiver always treats interfer- ence as noise. The decoding method at the secondary receiver is either Successive Interference Cancellation, treating interference as noise or Superposition Coding strategy, depending on the channel gains. The proposed algorithm achieves high data rate improvement for the secondary system, and a small improvement for the sum rate of the entire system while causing a very low degradation on the primary system?s rate.