Comparison of distributed space and frequency interference alignment

This paper addresses multiple access in MIMOwireless networks. It compares two distributed interferencealignment techniques, in space and in frequency, that bothaim at removing interferences through orthogonalization. Thetheoretical advantages and drawbacks of each technique arehighlighted. Then, the multiplexing gain and the computationalcomplexity are analytically evaluated. It is shown that frequencyinterference alignment achieves a higher multiplexing gain thanspace interference alignment in realistic network conditions,and always requires a lower computational complexity. Finally,the performances of both algorithms with varying number ofinterfering links are assessed via numerical simulations. Spaceinterference alignment fulfills complete interference suppression,and consequently provides the same spectral efficiency to alllinks, regardless of the number of interfering links. Frequencyinterference alignment is less efficient in terms of INR, and thespectral efficiency per link thus decreases when the number oflinks increases. Nevertheless, the spectral efficiency is alwayshigher with frequency interference alignment than with spaceinterference alignment