Ergodic Secrecy Rate Analysis of Ultra-Dense Networks with Multiple Antennas

Ultra-Dense Networks (UDNs), where Small Cells (SCs) will be deployed in very high densities, are considered as a leading promising technology in 5G and beyond. Such SCs being equipped with multiple antennas can further enhance the achievable performance. In particular, significant gains can be obtained in securing the wireless data transfer through Physical Layer Security (PLS) protocols. In this paper, we study the combined effects and trade-offs between densifying the SCs and increasing the number of antennas per SC on the achievable downlink secrecy rate per user. Using tools from stochastic geometry, we derive an analytical expression for the achievable average secrecy rate. The obtained results show that both approaches of densifying the SCs and/or increasing the number of antennas per cell enhance the secrecy level of communication. Interestingly, we show that reducing the density of SCs can be compensated by increasing the number of antennas per cell in terms of the achievable secrecy rate.