Replication-Based Outer Bounds: On the Optimality of "Half the Cake" for Rank-Deficient MIMO Interference Networks
The degrees of freedom (DoF) of the 3-user multiple-input multiple-output (MIMO) interference channel (IC) with full channel state information (CSI) and constant channel coefficients are characterized when linear filters are employed and (p, p+1) antennas are deployed at the transmitters and receivers, respectively. The point of departure of this paper is the work of Wang et al. , which conjectured but not proved the DoF for the configuration tackled in this work. In this work we prove the optimal DoF by means of a transmission scheme based on asymmetric complex signaling (ACS) together with symbol extensions in time and interference alignment (IA) concepts. The paper deals with the p = 2, 3 cases, providing the transmit and receive filters and the tools needed for proving the achievability of the DoF for other values of p.