Outdated interference alignment based transmit precoding for MU-MIMO

We present a simple transmit precoding scheme which exploits the delayed interference state information (INTSI) and the concept of interference alignment (IA). We design the precoding such that the inter-cell interference subspace from the previous transmission is aligned at the desired receiver with the intra-cell interference subspace of current transmission. Due to this fact, the alignment is not perfect for current transmission and causes leakage interference in the desired signal space. However, we show that with the help of proper receiver design, we can minimize this leakage interference and get substantial gains. We also consider the practical limitations of the current receivers and provide a modified solution to overcome these limits. With the help of extensive system level simulations we compare our scheme with other baseline MU-MIMO transmit precoding schemes in terms of mean user rates. The simulation results show that our proposed scheme provides considerable gains over the baseline transmission schemes.