Efficient resource allocation for MIMO-OFDMA based cognitive radio networks

In the opportunistic Cognitive Radio (CR) networks, the secondary users´ (SU) capacity is limited due to the need to avoid the primary users´ (PUs) bands. The combination of the Multiple-input multiple-output (MIMO) structure with the orthogonal frequency division multiplexing (OFDM) structure is a very promising candidate which can compensate for such a shortage of capacity through increasing the spectral efficiency. In this paper, a MIMO-OFDMA structure is proposed for the multiple access in multi-user CR networks. Furthermore, in order to achieve the maximum capacity in this structure, the resource allocation problem including proper allocation of sub-carriers to users and proper power allocation for each branch is investigated. To this aim, an efficient algorithm for the resource allocation is introduced. The performance of this algorithm is investigated and its superior efficiency is verified for CR networks via simulation.