Relay-aided interference alignment and neutralization for 3-cellular interference channels

As everyone knows, the energy of signals diminishes with increasing distance, so users at the edge of hexagon cells have lower signal-to-noise ratio (SNR) than users at the center, which means they are more easily interfered by signals from other base stations. So we consider the application of relay to the cellular case to help users at the edge to eliminate interferences and obtain higher sum-rate. In this paper we don't only use relay to neutralize interferences but also use interference alignment to reduce the number of antennas needed in destinations. To this end, we propose a relay-aided interference alignment and neutralization scheme. The relay knows all channel state information(CSI) and can solve out all signals transmitted by sources. To align and neutralize interferences, the relay needs to retransmit the signals solved out by using proper transmitting vectors. The transmitting vectors in sources and relay are carefully designed to achieve higher sum-rate and simulation results will prove it.