Performance Analysis And Key Technology Research Of MBM Systems

Media-based modulation(MBM)is a novel modulation scheme,which embeds information in different channel fading realizations created by changing the status of radio frequency mirrors placed near the transmit antenna.Compared with traditional multi-antenna technology,it has at-tractive potential advantages in terms of spectral efficiency,energy efficiency and hardware cost.Recently,there has been increasing research interest in its applications in massive MIMO systems and in physical layer security enhancement.This thesis is concerned with some key technology in MBM systems,and is composed of the following contents.Firstly,the basic model of the MBM system is studied.Detailed explanations on how infor-mation is conveyed by the channel is given.The optimal signal detection method is introduced.Employing different types of the channel model(Rayleigh fading and Rice fading in uncorrelated and correlated channel conditions),a tight upper bound of average bit error rate is derived.Besides,we analyze the average mutual information of the system and derive a closed-form approximation.Monte Carlo simulations are then performed to study the system performance with different system settings.Secondly,the problem of multi-user MBM signal detection in a large-scale MIMO system is investigated,where the base station is equipped with a large number of antennas and several users use MBM for uplink transmission.Interference cancellation-based iterative search algorithms and sparse recovery-based compressive sensing algorithms are proposed.The basic idea of the former is to treat the multi-user interference as noise and cancel it iteratively while that of the latter is to exploit the sparsity of MBM signals and formulate the signal detection problem as a sparse recovery problem.Computer simulation results show that the proposed algorithms have good performance with low complexity.Finally,we focus on physical layer security of MBM systems.It is assumed that the channel state information of both the legal user and the eavesdropper is known to the MBM transmitter.A probabilistic shaping-based scheme and a precoding-based scheme are investigated.The se-crecy rate is maximized by optimizing the probability mass function of the input MBM symbols and the precoding coefficients,respectively.We formulate the constrained non-linear non-convex optimization problems and convert those to unconstrained ones by changing the variables.An it-erative algorithm utilizing the gradient method with backtracking line search is proposed to find optimal solutions.Simulation results are provided to demonstrate the effectiveness of the proposed schemes.Besides,a close-form approximation of the mutual information is introduced to reduce the complexity,which is verified to be a good alternative formula by simulations.