Secure Hybrid Digital and Analog Precoder for mmWave Systems With Low-Resolution DACs and Finite-Quantized Phase Shifters

Abstract

Millimeter wave (mmWave) communication has been regarded as one of the most promising technologies for the future generation wireless networks because of its advantages of providing a ultra-wide new spectrum and ultra-high data transmission rate. To reduce the power consumption and circuit cost for mmWave systems, hybrid digital and analog (HDA) architecture is preferred in such a scenario. In this paper, an artificial-noise (AN) aided secure HDA beamforming scheme is proposed for mmWave MISO system with low resolution digitalto-analog converters (DACs) and finite-quantized phase shifters on RF. The additive quantization noise model for AN aided HDA system is established to make an analysis of the secrecy performance of such systems. With the partial channel knowledge of eavesdropper available, an approximate expression of secrecy rate (SR) is derived. Then using this approximation formula, we propose a two-layer alternately iterative structure (TLAIS) for optimizing digital precoder (DP) of confidential message (CM), digital AN projection matrix (DANPM) and analog precoder (AP). The inner-layer iteration loop is to design the DP of CMs and DANPM alternatively given a fixed matrix of AP. The outerlayer iteration loop is in between digital baseband part and analog part, where the former refers to DP and DANPM, and the latter is AP. Then for a given digital part, we propose a gradient ascent algorithm to find the vector of AP vector. Given a matrix of AP, we make use of general power iteration (GPI) method to compute DP and DANPM. This process is repeated until the terminal condition is reached. Simulation results show that the proposed TLAIS can achieve a better SR performance compared to existing methods, especially in the high signal-to-noise ratio region.Index Terms-Hybrid digital and analog, mmWave, security, artificial Noise, low-resolution digital-to-analog converter(DAC)

Hybrid Analog-Digital Precoder Design for Securing Cognitive Millimeter Wave Networks

“…As a further development, Ramadan and Minn [25] have imposed the artificial noise on the eavesdropper for enhancing the PLS of mmWave communications. By considering a mmWave MISO network and assuming low-resolution digital-to-analog converters as well as quantized phase shifters, Xu et al [26] have designed a hybrid secure precoder for maximizing the achievable secrecy rate. Zi et al [27] have studied the hybrid precoder design for improving the secure energy efficiency of IoT networks.…”

“…The authors of [24], [25], [27] proposed several heuristic algorithms, which resort to separate design approaches for independently optimizing the analog precoder and digital precoder or adopt an approximate secrecy performance metric instead of the secrecy rate as the objective function. Xu et al [26] proposed a gradient ascent algorithm to alternatively design the analog and digital precoder. However, none of the contributions mentioned above address the secrecy rate maximization problem from a mathematical optimization perspective.…”

“…We adopt the widely used stochastic approach [26], [46]- [48] for handling Eves' CSI uncertainty. In particular, we adopt the average secrecy rate as the objective function, which averages the achievable secrecy rate over Eves' uncertainty and converts the impact of Eves' CSI uncertainty into a more amenable formulation.…”

“…As commented by Zhang et al [45], such an approximation becomes accurate upon increasing the number of antennas, hence it is quite accurate in the massive MIMO setting. Furthermore, this approximation has been widely adopted by authoritative contributions on PLS [26], [46]- [48]. Therefore, employing the lower bound technique, problem (52) can be approximated as follows:…”

“…As IoT is pervading both industry and our daily life, more and more confidential information will be transmitted over wireless channels, hence communication security is vitally important [4], [5]. Physical layer security (PLS) exploits the randomness of the wireless media in an innovative way for securing the confidential information transmission [4], [26]. The study of cognitive radio networks relying on PLS is a particularly active research field [15]- [20].…”