Selection diversity for interference alignment systems

This paper explores the use of selection diversity for interference alignment systems. Multiple distinct alignment modes exist for certain types of interference network. By selecting the best alignment mode to support the signal-to-noise rate (SNR) of the worst user, a diversity gain improvement can be observed. This paper shows that in a 3-user double-antenna interference channel, a system switching between two alignment modes achieves a diversity gain of 2 in the fixed-rate regime and the maximum degree-of-freedom (DoF) gain of 3 in the variable-rate regime. Consequently, we disprove a previous feasibility condition for diversity in alignment systems, which requires a trade-off between the DoF gain and the diversity gain.