On feasibility of linear interference alignment for single-input-single-output multi-frequency interference channel

This study explores the feasibility of linear interference alignment (IA) for a (M × M, 1)^K system with multi-frequency independent channels. The authors prove that number of users K ≤ 2M - 2 is a necessary condition for (M × M, 1)^K multi-frequency IA system, which is less than that of (M × M, 1)^K multiple-input-multiple-output system (i.e. K ≤ 2M - 1). The conclusion can be extended to all cases with the diagonal channel matrix. They also reveal that the traditional frequency division multiplexing method is inefficient in spectrum utilisation. They apply max-SINR (signal to interference plus noise ratio) and iterative IA algorithms and the author´s simulation results verify that IA algorithms work well in (M × M, 1)^2M-2 IA system.