Interference Neutralization With Partial CSIT for Full-Duplex Cellular Networks

Abstract

Compared to half-duplex (HD) communications, full-duplex (FD) communications have the potential to double the throughput of the cellular networks. However, the inter-user interference (IUI) from the uplink (UL) users to the downlink (DL) users severely hinders the improvement of the throughput. In this paper, we propose an interference neutralization (IN) scheme to eliminate the IUI with the help of partial channel state information at the transmitter (CSIT). Before the UL signals are transmitted, we rotate their phases through a set of scalars known by the base station (BS), which endows the conventional receive antennas of the BS with the reconfigurability. The BS assists the IUI management by precoding and forwarding the UL signals to the DL users. Consequently, the UL signals forwarded by the BS locate in the opposite direction of the IUI so as to neutralize it. After the IUI is neutralized, all the symbols of the last time slots can be recovered. The DoF region and the corresponding feasible conditions are analyzed. The analysis and numerical results demonstrate that 1.5-fold DoF over that of the HD systems can be achieved via the proposed IN scheme with only partial CSIT and 2 symbol extensions. It shows that the proposed scheme is a low complexity interference management scheme for the FD cellular networks.INDEX TERMS Full-duplex, inter-user interference (IUI), CSIT, Degrees of Freedom (DoF).