Frequency-Space Interference Alignment in Multi-Cell MIMO OFDM Downlink Systems

We consider two approaches to frequency-space Interference Alignment (IA) in multi-cell systems that use Orthogonal Frequency Division Multiplexing (OFDM) and Multiple Input Multiple Output (MIMO). In the first approach, which we call frequency-space IA, we align and remove the interference from the signals radiated from the base stations intended for the users from the other cells (inter-cell interference) using transmit precoders and receive decoders, and we remove the interference from the users within the cell (intra-cell interference) by using additional Zero-Forcing (ZF) precoding that precedes the IA precoding at the transmiter (base station). In the second approach, we assume that Orthogonal Frequency Division Multiple Access (OFDMA) downlink is used for transmission to the users within the cell, which avoids the intra-cell interference, and we apply frequency-space IA to the inter-cell interference only. Simulation results show that the first approach outperforms the second in a broad SNR region.