A novel relay-based interference alignment strategy for multi-user networks

Interference alignment (IA) is a transmission strategy that use channel state information (CSI) to improve the capacity of multiuser communication systems. However, the performance of IA is always limited by the accuracy of the CSI. In particular, this is a problem in time-varying channels, as the CSI at transmitter (CSIT) may become outdated when the channel is changing quickly. In this study, we propose a novel cooperative relay-based interference alignment (RIA) scheme, which aims to increase the number of Degrees of Freedom (DoF) for the multiuser networks, even when the required source-to-destination CSIT is completely outdated. With the RIA scheme, the DoF region is firstly derived under an ideal CSIT case. Then, the RIA scheme is respectively presented in non-ideal CSIT cases. Furthermore, the achievable DoF regions by RIA in these non-ideal cases are derived. In addition, the trade-off between relay-based and non-relay based IA schemes are analysed.