1. A method of relaying data among a plurality of node pairs using a plurality of relay nodes, the method comprising: obtaining a first channel matrix between antennas included in a plurality of source nodes and antennas included in the plurality of relay nodes; obtaining a second channel matrix between the antennas included in the plurality of relay nodes and antennas included in a plurality of destination nodes; generating an effective interference channel matrix based on the first channel matrix to and the second channel matrix; and calculating at least one null space vector included in a null space of the effective interference channel matrix where the null space vector is not a zero vector.