In this paper, we propose an efficient and robust interference mitigation technique based on a nullsteering multiuser multiple-input multiple-output (MU-MIMO) spatial division multiple access (SDMA) scheme for frequency sharing between IMT-Advanced and Fixed Satellite Service (FSS). In the proposed technique, the conventional precoding matrix for SDMA unitary precoded (UPC) MIMO proposed by the authors is modified to construct nulls in the spatial spectrum corresponding to the direction angles of the victim FSS earth station (ES). The frequency sharing results are given in terms of interference power and minimum separation distance in the co-channel. Simulation results shows that our mitigation technique reduces interfering power by about 60dB and can meet the maximum permissible interference power condition in almost separation distances. Therefore it can be concluded that the proposed mitigation technique in this paper is highly efficient in terms of reducing the separation distance as well as robust against DOE estimation errors.