Degrees of freedom of the MIMO interference channel with parallel multicasting

Abstract : We investigate the degrees of freedom (DoF) for the two-user multiple-input multiple-output interference channel (MIMO IC) with parallel multicasting channels. Specifically, in addition to the MIMO IC, each transmitter is also connected to both receivers via an out-of-band multicast channel. Our main contribution lies in the characterization of the optimal sum DoF when the channel state information (CSI) on the MIMO IC is available to the transmitters with some delay (delayed CSIT). We show that jointly coding over the parallel multicast channels can achieve higher DoF than channel aggregation does. Furthermore, as long as the rate of the multicast channels is above a certain threshold, delayed CSIT is enough to achieve the same DoF performance as with instantaneous CSIT.