1. A method of relaying data among node pairs using relay nodes, the method comprising: obtaining a first channel matrix between antennas related to source nodes and antennas related to the relay nodes; obtaining a second channel matrix between the antennas related to the relay nodes and antennas related to destination nodes; generating an effective interference channel matrix based on the first channel matrix and the second channel matrix; wherein the generating comprises: obtaining an interference pair comprising a source node and a destination node that are excluded from the node pairs; transposing a channel matrix between antennas of the source node related to the interference pair and antennas of one of the relay nodes; and calculating a Kronecker product of the transposed channel matrix and a channel matrix between the antennas of one of the relay nodes and antennas of the destination node related to the interference pair; 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.