MIMO interference alignment for cognitive radio network

Though various cognitive radio schemes have been developed, they have not considered the problem of co-channel interference for cognitive users (CU) and primary user (PU)to share a OFDM channel, also well as MIMO-OFDM channel. This paper proposes a scheme that allows PU and CU share a same frequency band, while there are two problems to be solved: the interference of CU to PU, and interference of PU to CU. To solve the first problem, this paper proposes an ICA preceding scheme to cancel the interference of CU to PU, the preceding scheme involves the design of cognitive transmitters. To solve the second problem, this paper proposes CU receiver algorithm, we use inverse matrix to cancel the PU signal interference. The proposed scheme is not limited in the case that a MIMO-OFDM system of cognitive users in a wide spectrum range, and the primary user operates at a narrower channel bandwidth in overlap with the channel of the cognitive user. We designed an ICA CU system as a 2 × 2 MIMO OFDM system, while we need not change the PU systems´ design. The simulation of the bit error rate of proposed ICA CU system verifies the proposed scheme.