Secure massive MIMO‐enabled full‐duplex 2‐tier heterogeneous networks by exploiting in‐band wireless backhauls

Abstract

AbstractTo enhance the spectrum efficiency and secrecy performance, by using in‐band full‐duplex (FD) wireless backhaul technique, a secure massive multiple input multiple output (MIMO)–enabled heterogeneous cellular network (HCN) model is presented, where the macro base stations (MBSs) are equipped with massive MIMO antenna array, whereas the small cell base stations (SBSs) and user equipment have the single antenna. The ultradense small cells underlay the macro cells and offload traffic from macro cells. With FD mode, the massive MIMO MBSs and single‐antenna SBSs are responsible, respectively, for the access traffic of macro and small cells as well as the backhaul transmission between MBSs and SBSs over the same time‐frequency resource. The transmissions of macro and small cells are exposed to non‐colluding and passive eavesdroppers that attempt to decode the signals of legitimate users. For such HCN with in‐band wireless backhaul, by modeling the network elements as the independent Possion point processes and using the stochastic geometry, we first investigate the secrecy probabilities of the macro cell downlink and small cell uplink transmissions. At the same time, to achieve a comprehensive view, we also investigate the corresponding signal‐interference‐noise ratio (SINR) coverage performance. The presented numerical results show that when the intensity of user equipment is small relatively, exploiting the in‐band backhaul interference as jamming signals can enhance the secrecy probabilities of both the macro and small cell transmissions so that the in‐band FD backhaul mode outperforms the out‐band FD one. However, for the SINR coverage, the opposite results are achieved. That is to say, the in‐band backhaul transmission degrades the SINR coverage probabilities because of the existence of wireless backhaul interference. Besides of these, in numerical analysis, we also investigate the effect of the network parameters on the secrecy and coverage performance of both the macro and small cells. The derived results can be used for guiding the design of HCNs.