Cellular interference alignment (01 January 2014)

Interference alignment (IA) promises that, in Gaussian interference channels, each link can support half of a degree of freedom (DoF) per pair of transmit-receive antennas. However, in general, this result requires to precode the data bearing signals over a signal space of asymptotically large diversity, e.g., over an infinite number of dimensions in time-frequency for time-frequency varying fading channels. 

Here, we propose a communication scenario in wireless cellular systems where the promised optimal DoFs are achieved with linear precoding in one-shot (coding over a single time-frequency slot). We focus on uplink cellular systems, where each cell is split into three sectors and assume that interference is generated locally between transmitters and receivers of neighboring cells. We consider a message-passing network architecture, in which nearby sectors can exchange already decoded messages and propose an alignment solution that can achieve the optimal DoFs. 

To avoid signaling schemes relying on the strength of interference, we further introduce the notion of topologically robust schemes, which are able to guarantee a minimum rate (or degrees of freedom) no matter if the interference link are strong or weak. Towards this end, we design an alignment scheme which is topologically robust and still achieves the same optimum DoFs.