Asynchronous interference alignment

A constant three-user interference channel wherein users are not symbol synchronous is considered. A novel practical interference alignment scheme for this channel is proposed wherein aligning interfering signals at each receiver is performed with the help of asynchronous delays which inherently exist among the received signals at each receiver node. Due to the existence of asynchronism among the users, the underlying quasi-static flat fading links are converted into frequency selective and accordingly into time varying channels with correlated coefficients across the time. This solves the lack of channel variation required for interference alignment in quasi-static scenarios. It is proved that the proposed scheme achieves the total degrees of freedom equal to 3/2 of this channel almost surely in the limit of codeword´s length. Application of the proposed scheme is not limited to high signal to noise ratio (SNR) regime and it can be used in any range of SNR.