Uplink/downlink achievable rate analysis of heterogeneous networks with massive MIMO full-duplex backhaul link

Heterogeneous networks (HetNets) which involves densifying a high powered macro cell (MC) with a number of low powered small cells (SCs), has been identified as key technology for 5G communication. This technology requires that MC is connected to SCs with high speed fiber optic cable for control and coordination. However connecting fiber links to all cells is expensive, labor intensive and less flexible. This paper proposes HetNet topology where massive MIMO with full-duplex (FD) provides wireless backhaul link for SCs. Communication is achieved in two phases. In the first phase, we assume cells in the HetNet are equipped with massive receive antennas and single transmit antennas whereas in the second phase a circulator switches massive antenna receivers into transmitters and single antenna transmitters into receivers. We derive accurate approximations for uplink/downlink (UL/DL) rate under the assumption of imperfect channel state information. Our results indicate that the strength of loop interference (LI) and SC-to-SC interference which occur due to FD operation depends largely on the number of SCs. By increasing the number of SCs, achievable rates also increase but requires more antennas to overcome the deleterious effects of LI and SC-to-SC interference.