Abstract:

 Cognitive users can opportunistically utilize the unused spectrum resources without causing interference to primary user or affecting primary users communication. How to apply transmit beamforming to eliminate the primary user interference from cognitive user is the key. Firstly, the system model that the cognitive user network coexists with primary user network was developed. Then, an optimal beamforming algorithm that can completely eliminate the primary user interference from cognitive user was proposed. Compared with calssical zeroforcing beamforming algorithm, the proposed algorithm not only can eliminate the the primary user interference from cognitive user, but can improve the performance of itself. Finally, a performance simulation of the optimal beamforming algorithm was present. The result shows that the proposed algorithm has a better performance than zeroforcing beamforming.

Key words: cognitive user, primary user;interference, beamforming