Reliability of MIMO-OFDM Interference Alignment Systems with Antenna Selection under Real-World Environments

Interference alignment (IA) gives a promise to achieve the maximum degrees of freedom of K-user multiple-input-multiple-output (MIMO) interference channels. This theoretical result can be achieved under ideal channels. In practice, the prospective IA sum-rate may not always be achievable, particularly in indoor environments. For this reason, an acceptable sum-rate of IA in MIMO orthogonal frequency-division-multiplexing (MIMO-OFDM) interference channels was obtained in the literature by increasing the separation between antennas to 2 lambda and pre-allocating the user-pairs in specific setups in order to minimize the correlation between channels. In this paper, we propose to apply transmit antenna selection to MIMO-OFDM IA systems either through bulk or per-subcarrier selection, aiming at improving MIMO-OFDM IA systems sum-rate under real-world channel circumstances, while keeping the minimum antenna separation of 0.5 lambda. Furthermore, a simplified antenna selection scheme is proposed for correlated channels, which enhances MIMO-OFDM IA sum-rate with simple selection process and minimal hardware cost. Accordingly, the practical feasibility of MIMO-OFDM IA systems is significantly increased by antenna selection in real-world scenarios. This has been verified using simulation that considers channel realizations that characterize a real-world multi-user indoor environment.