Shiqi Gong

Millimeter-Wave Secrecy Beamforming Designs for Two-Way Amplify-and-Forward MIMO Relaying Networks

The gigahertz unlicensed bandwidth spectrum endows millimeter-wave (mmWave) communications with the great potential of realizing high data transmission rates. Similar to all wireless transmission technologies, mmWave communications are also susceptible to security threats. This problem becomes more serious for cooperative networks that need more information exchanges. In this paper, we investigate the secrecy beamforming designs for mmWave two-way amplify-and-forward (AF) multiple-input–multiple-output (MIMO) relaying networks. To control hardware size and cost, an additional rank constraint is posed on the forwarding matrix at the relay to control the number of analog-to-digital converters (ADCs). In general, the considered optimization problem is nonconvex and very challenging. Based on iterative optimization algorithms, the secrecy beamforming designs are successfully decoupled into a series of convex subproblems that can be solved efficiently. Finally, numerical experiments are conducted to demonstrate the performance advantages of the proposed secrecy beamforming designs.

Cooperative beamforming design for physical-layer security of multi-hop MIMO communications

The security issue is critically important for wireless communications, especially for multi-hop communications. In this paper, we propose a cooperative secrecy beamforming scheme for a multi-hop MIMO communication network, in which there is a single-antenna source, multiple multi-antenna relays and a singleantenna destination. Moreover, two types of eavesdroppers exist in the network, one of which has known channel state information (CSI), while the other not. To achieve security communications, in our work null-space beamforming and artificial noise beamforming are jointly optimized to improve the secrecy rate of the multi-hop network. In nature, the joint optimization is nonconvex and challenging. Exploiting its structure, the considered optimization problem is decoupled into a series of subproblems that can be efficiently solved based on convex optimization theory. Finally, some numerical experiment results are provided to assess the performance of the proposed secrecy beamforming design.创新点物理层安全在无线网络通信中占据重要地位,尤其是针对窃听可能性较大的多跳网络。基于此我们提议了一个协作的多跳MIMO通信网络下的安全波束赋性方案。假定网络中存在一个单天线的发射端,多个多天线的中继以及一个单天线的接收端, 同时还有两个不同类型的窃听者, 其中一类窃听者的信道信息已知, 而另一类窃听者信道信息未知。为了实现多跳 MIMO 网络的安全通信,我们采用迫零波束赋性算法和人工噪声发送方案来分别尽可能的降低被这两类窃听者窃听的信息量,从而达到提升多跳网络的安全容量的目标。通常来说,对多个基站进行联合波束赋形设计有一定的困难和挑战,因为优化问题常常是非凸的NP-hard 问题。 因此, 我们提议了一个基于凸优化理论的迭代波束赋形优化算法,通过将原始的非凸优化问题分解为一系列具有凸性质的子问题来迭代的设计每个基站的最优波束矩阵。仿真结果表明我们所提议的算法可以有效的提升系统的安全容量。

Energy-efficient transceiver design for multi-pair two-way relay systems

In this paper, we focus on energy-efficient transceiver and relay beamforming design for multi-pair two-way relay system. The multi-antenna users and the multi-antenna relay are considered in this work. Different from the existing works, the proposed algorithm is energy-efficient which is more applicable to the future green network. It considers both the sum-MSE problem and the power consumption problem for the users under the relay power constraint. Based on the optimal condition decomposition (OCD) method, the energy-efficient precoders at the users can be designed separately with limited information exchanged. The proposed relay beamforming algorithm is based on the alternative direction method of multipliers (ADMM) which has simpler iterative solution and enjoys good convergence. Simulation results demonstrate the performance of the proposed algorithms in terms of power consumption and MSE performance.

Energy Efficient Transmission in Multi-User MIMO Relay Channels With Perfect and Imperfect Channel State Information

We design novel transmission strategies to maximize the energy efficiency (EE) of the uplink multi-user multiple-input and multiple-output relay channel. In this channel,

Secrecy beamforming design for large millimeter-wave two-way relaying networks

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Secure communications for SWIPT over MIMO interference channel

multi-antenna users communicate with a multi-antenna base station (BS) through a multi-antenna relay. To achieve the goal of EE maximization, we propose new iterative algorithms to jointly optimize the multi-user precoder and the relay precoder under transmit power constraints for two cases. In the first case, the perfect global channel state information (CSI) is available, while in the second case, the CSI between the relay and the BS is imperfect. To surmount the non-convexity of our formulated EE optimization problems in both cases, we introduce the parameter subtractive function into the proposed algorithms. Then, the EE parameter in the parameter subtractive function is updated by Dinkelbach’s algorithm in the perfect CSI case, and by the bisection method in the imperfect CSI case. Moreover, in the perfect CSI case, the relay precoder is optimized by the diagonalization operation and the multi-user precoder is optimized based on the weighted minimum mean square error method. Differently, in the imperfect CSI case, we apply the sign-definiteness lemma to promote the semidefinite programming formulation of the EE optimization problem. Furthermore, we present the numerical results to demonstrate that our proposed iterative algorithms have a good convergence rate in both cases. In addition, we show that our proposed iterative algorithms achieve a higher EE performance than the existing algorithms in both CSI cases.

A novel transceiver architecture in the two-way relay channel with analog and digital beamforming

Thanks to gigahertz unlicensed spectrum, the millimeter wave (mmWave) communication becomes an important enabling technology to meet the increasing data rate demands of future communication systems. It is also well-known that wireless communications are susceptible to security threatening, especially for wireless two-way relaying networks. Hence, in this work, we propose two secrecy beamforming schemes for large mmWave two-way relaying networks. Firstly, the secrecy rate maximization problem is considered with the constraint of relay power. Then the relay transmit power is optimized to satisfy the secrecy rate requirement of network. Owing to the nonconvexity of original optimization problem, the null-space beamforming is utilized to transform both problems into the standard SOCP problem, which can be solved effectively with the convex optimization technique. Finally, numerical experiments are conducted to show the superior security performance and high energy efficiency of the two proposed secrecy beamforming schemes, respectively.

Polarization Sensitive Array Based Physical-Layer Security

Owing to the wireless signal power received by the energy harvesting (EH) node is generally higher than that of the information decoding (ID) node in simultaneous wireless information and power transfer (SWIPT) system, the confidential information becomes vulnerable to be wiretapped. Motivated, in this paper, we aim at realizing secure communications for two-user MIMO interference channel with SWIPT. Unfortunately, the formulated secrecy rate maximization problem is non-convex with respect to the covariance matrices of two transmitters, thus an alternative algorithm is proposed to solve the nonconvex optimization problem. Firstly, the orthogonal-projection-based optimization algorithm is performed to completely suppress the interference to ID receiver, then by applying the Taylor series expansion, the covariance matrix of information transmitter is optimized based on the dual optimization. Finally, numerical experiments are conducted to validate the security performance of the proposed algorithm.

Multi-Objective Optimization for Distributed MIMO Networks

In this paper, we propose a novel transceiver architecture at relay for multiple input, multiple output two-way relay channel (TWRC). This transceiver architecture consists of the analog beamforming in RF domain and the MMSE based digital processing at baseband, which is simplified as RF-MDP-MIMO architecture. Under the RF-MDP-MIMO architecture, the objective of this paper is to find the optimal relay transmit and receive beamformings that can achieve the boundary of the optimal capacity region with limited relay power. Specifically, by formulating the original optimization problem into two semidefinite programing (SDP) problems with rank-one constraints which can be effectively solved by the penalty function method, we can optimize relay transmit and receive beamformings alternatively. Then, the maximum achievable sum rate of TWRC can be obtained with the bisection method. Further, the achievable capacity region is realized. Numerical experiments are conducted to show that our proposed RF-MDP-MIMO architecture outperforms the RF-MIMO architecture in terms of the optimal achievable capacity region.

A QoE-based jointly subcarrier and power allocation for multiuser multiservice networks

We propose a framework exploiting the polarization sensitive array (PSA) to improve the physical layer security of wireless communications. Specifically, the polarization difference among signals is utilized to improve the secrecy rate of wireless communications, especially when these signals are spatially indistinguishable. We firstly investigate the PSA based secure communications for point-to-point wireless systems from the perspectives of both total power minimization and secrecy rate maximization. We then apply the PSA based secure beamforming designs to relaying networks. The secrecy rate maximization for relaying networks is discussed in detail under both the perfect channel state information and the polarization sensitive array pointing error. In the later case, a robust scheme to achieve secure communications for relaying networks is proposed. Simulation results show that the proposed PSA based algorithms achieve lower total power consumption and better security performance compared to the conventional scalar array designs, especially under challenging environments where all received signals at destination are difficult to distinguish in the spatial domain.