Abstract:Partial projection based interference suppression algorithm is proposed for cognitive Multiple-Input Multiple-Output(MIMO) system to achieve effective spectrum sharing between primary user and cognitive user. In this algorithm, spatial transmission characteristics of the primary user are introduced to the design of secondary user’s transmission. Based on analysis of structural characteristics of the interference, it is proved that the leakage signal from secondary transmitter to the idle dimensions of primary user is not harmful. Then the secondary signals are projected to the null space of low-dimensional subspace of interference channel between primary and secondary user to eliminate interference. Theoretical analysis and simulation results show that the algorithm effectively eliminates interference to the primary user; the secondary user’s transmission rate and the applicability of the algorithm have been significantly improved compared to the traditional method.