Degrees-of-freedom of the K-user MISO interference channel with delayed local CSIT

This paper considers a K-user Multiple-Input-Single-Output (MISO) Interference Channel (IC), where the channel state information obtained by the transmitters (CSIT) is perfect, but completely outdated. A Retrospective Interference Alignment (RIA) using such delayed CSIT was proposed by Maddah-Ali et. al for the MISO Broadcast Channel (BC), but the extension to the MISO IC is a non-trivial step as each transmitter only has the message intended for the corresponding user. Recently, Abdoli et.al focused on a Single-Input-Single-Output (SISO) IC and solved such bottleneck by inventing a distributed higher order symbol generation. Our main work is to extend Abdoli´s work to the MISO case by integrating some features of Maddah-Ali´s scheme. The achieved sum Degrees-of-Freedom (DoF) performance is asymptotically given by 64/15 when K→∞, outperforming all the previously known results.