Space-Time Interference Alignment: DoF of Two-User MIMO X Channel With Alternating CSIT

摘要

In this letter, we consider the sum degrees of freedom (sum-DoFs) of the two-user multiple-input multiple-output (MIMO) X channel with alternating channel state information (CSI) at the transmitters (CSIT), which implies that the CSI available to the transmitters is distributed. Two space-time interference alignment schemes are proposed for the same channel, which possess novel ingredients, namely, interference regeneration and symbolic elimination. The new sum-DoFs achieved by these two schemes are mutually complementary over different antenna configurations. Moreover, the achieved sum-DoFs for certain antenna configurations are greater than the best known sum-DoFs in the literature with delayed CSIT.