The K -user two-hop interference channel. The transmitters (TXs) and the half-duplex DF relays are equipped with multiple antennas while the receivers (RXs) have a single antenna. Each relay aids the signal forwarding of only one TX–RX pair. The transmission procedure requires two stages. In the first stage, the TXs send data to the relays. In the second stage, each relay decodes its received signal, re-encodes and retransmits to its associated RX.