Abstract
In this paper, we consider secure transmission in the downlink of a multicell multiple-input multiple-output (MIMO) system with M cells; each cell consists of an N-antenna base station (BS) and K single-antenna users. Coordinated beamforming (CBf) is employed for secrecy enhancement. For CBf, the BSs can jointly design their respective beamformers to control intercell interference and information leakage. Based on regularized channel inversion (RCI) precoding structures, we derive the concise formulas for the signal-to-interference-plus-noise ratio (SINR) for the legitimate users and the colluding malicious users and the achievable secrecy sum rate for the CBf. Furthermore, we obtain a novel closed-form expression of the secrecy sum in the large-system regime where N and K tend to infinity with a fixed ratio β=K/N. Based on the large-system regime result, the regularization parameter is optimized to maximize the secrecy sum rate. It shows that the optimal regularization parameter decreases with the signal-to-noise ratio (SNR) and stays constant at high SNR if β>1/M. Compared with single-cell processing (SCP) without BS cooperation, simulation results show that the secrecy performance can be significantly enhanced by exploiting CBf. The analytical results are validated with the finite-size system by simulation.
Highlights
Multicell multiuser multiple-input and multiple-output (MIMO) has been considered a classical scenario for 5G networks
In addition to the widely used cryptographic approach, information-theoretic security by exploiting the physical layer to achieve perfect secrecy, known as physical layer security, has attracted attention widely [1,2,3]. e pioneering work made by Wyner introduced the wiretap channel in [4], and secrecy capacity was defined to measure the performance of physical layer security. en, it was extended to the broadcast channel with a confidential message [5] and the Gaussian wiretap channel [6]
We focus on the Coordinated beamforming (CBf) scheme, and the base station (BS) partially cooperate based on the channel state information (CSI) of all users
Summary
Multicell multiuser multiple-input and multiple-output (MIMO) has been considered a classical scenario for 5G networks. Physical layer security for single-cell multiuser MIMO communications was first studied in the broadcast channel, where a multiantenna BS transmitted confidential messages to multiple users at the same time. In the CBf, the BSs only share the CSI, but they do not share the messages to transmit Many studies, such as [19,20,21,22], employed the MCP to improve the secrecy rate in multicell MIMO systems. We extend to study the achievable ergodic secrecy sum rate in the downlink multicell MIMO system with M cells, where there are one N-antenna BS and K single-antenna users in each cell. E{·} denotes the expectation operation. e trace of a matrix is denoted by Tr(·), (·)− 1 denotes the inversion operator, and ⟶ a.s. denotes almost sure convergence
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
