Degrees of Freedom of Time Correlated MISO Interference Broadcast Channels with Delayed CSIT

Abstract

In this work we study the degrees of freedom (DoF) of the two-cell two-user-per-cell multiple-input single-output (MISO) time correlated interference broadcast channel (IBC) with perfect delayed channel state information at the transmitter (CSIT). The time correlation implies that an imperfect estimate of the current CSIT is also available. Within this context we show that the achievable DoF region can be represented as a 4-dimensional polygon and prove how each of the corresponding DoF vertices can be achieved. In particular two new transmission schemes are proposed, a multi-phase one and a single time slot one. Both use zero-forcing (ZF), rate splitting and appropriate power allocation to achieve higher DoF. Additionally, the multi-phase scheme also applies retrospective interference alignment; therefore in order to design it we first propose a new adaptation of the MAT scheme applicable to this type of network.