人工噪声辅助的物理层安全信号峰均功率比减低算法

人工噪声辅助的物理层安全通信系统采用人工噪声破坏窃听信道的方式提升系统安全信道容量是近年来物理层安全通信领域研究的经典系统模型之一。该文针对这一模型中发射信号存在高峰均功率比问题,利用噪声子空间提供的冗余度提出一种基于噪声子空间功率分配的峰均功率比降低算法。该算法通过分式规划、DC规划以及二次非凸等式约束松弛将非凸的峰均功率比优化问题转化为一系列的凸问题迭代求解。仿真结果表明在系统放大器存在一定线性范围的约束下,该文提出的算法能够有效降低人工噪声辅助的物理层安全通信系统发射信号的峰均功率比问题,达到提高系统中合法用户的通信性能的目的。     

一种基于时空编码的物理层安全算法

针对多天线窃听系统的物理层安全问题,提出一种基于时空编码的预编码算法。首先,合法接收者发送训练序列用于发送者估计主信道状态信息,而窃听信道的状态信息合法用户均未知;其次,发送者利用均匀信道分解的方法提取主信道状态信息的特征参数,生成发射端预编码矩阵和合法接收端均衡矩阵,收发联合加密处理提高物理层安全;最后,利用 Monte Carlo方法进行仿真实验,数值分析表明,该算法在窃听者天线数目增多时能够实现非负的保密容量,即使窃听信道质量较好时,窃听者的接收性能仍维持在很差的水平,误码率高达0.5。     

6G通感融合网络中的物理层安全：机遇与挑战

第六代无线通信（6G）网络对通信速率与感知精度均提出更高要求，通信感知融合技术引起了广泛关注。一方面，感知波形的强指向性使得通信感知融合系统的信息传输面临严峻的安全挑战，另一方面，系统的感知能力也为利用物理层安全技术提升系统安全性提供了新的契机。为了研究面向6G的通感融合网络中的物理层安全问题，首先对通感融合网络中潜在的窃听模型进行总结，随后探索了利用感知能力获取窃听方信道信息的可行性，展示了物理层安全技术在6G通感融合网络中的应用实例，例如感知辅助干扰、协作干扰等，最后讨论了新兴技术在物理层安全辅助的通感融合网络中的潜在应用方向。     

一种加权均方误差最小化的鲁棒性干扰对齐算法

线性干扰对齐的一个常见优化目标是总传输速率最大化,但因为和速率函数的非凸特性而难以直接求解。加权均方误差最小化算法借助均方误差与和速率之间的等价关系解决了这一问题。这一方法需要获得准确的信道状态信息,在实际应用中,通道估计误差的存在会导致算法性能的下降。该文提出一种改进算法,在干扰对齐预编码矩阵与接收矩阵的优化求解过程中将通道估计误差的统计特性考虑在内。仿真结果表明,相比以往的加权均方误差最小化算法,该文算法对信道估计误差具有较高的鲁棒性,可以有效提高总的传输速率。     

不准确CSI下智能反射表面辅助的多用户系统物理层安全方案设计

该文研究智能反射表面(Intelligent Reflecting Surface, IRS)辅助的多用户下行系统中的物理层安全的优化问题。多个用户之间的信息需要相互保密,每个时隙,非信息传输的目标用户视为窃听者,因此这是一个多窃听者的安全传输系统。由于信道的时变性,基站拥有窃听信道的信道状态信息(Channel State Information, CSI)为与真实的CSI间存在误差的过时信息。在此条件下,以系统最坏情况下的保密速率最大化为目标,对基站发射信息信号和人工噪声波束成形矢量,以及IRS的相移矩阵进行联合优化。原始优化问题为非凸半正定规划问题,利用松弛变量、惩罚函数、Charnes-Cooper变换和交替迭代优化等方法将原问题转化为凸问题并求解。仿真结果显示,相较于基准方案,该文所提出的优化算法能有效提高系统的保密速率。     

空天地通信网络中物理层安全技术综述

空天地一体化通信网络是未来无线通信的发展趋势,其固有的广播特性和广阔的覆盖区域,将导致网络通信系统面临严重的安全威胁。如何保证空天地通信网络的安全性是一个亟待解决的问题。物理层安全技术作为一种有效的安全手段,在无线通信领域受到越来越多的关注。介绍了物理层安全的基础以及空天地通信信道模型,并对物理层安全中常见的窃听编码、波束成形、人工噪声、中继协作干扰和物理层密钥加密等技术进行了介绍和总结,最后提出了空天地通信网络中物理层安全面临的挑战和未来的发展趋势。     

智能反射面辅助的抗干扰安全通信系统鲁棒资源分配算法

为了解决恶意干扰攻击、窃听和不完美信道状态信息造成的通信质量降低和安全性差等问题,该文提出一种智能反射面(IRS)辅助的抗干扰安全通信系统鲁棒资源分配算法。首先,基于合法用户的最小安全速率约束、最大发射功率约束和IRS相移约束,在非法节点不完美信道状态信息、干扰器波束成形向量未知的情况下,构建了一个联合优化基站的波束成形向量、人工噪声的协方差矩阵和IRS的相移矩阵的鲁棒资源分配问题。其次,为了求解该非凸问题,利用交替优化、Cauchy-Schwarz不等式、连续凸逼近和泰勒级数展开等方法,将原问题转化为易于求解的凸优化问题。仿真结果表明,与传统算法相比所提算法能有效提高系统安全性、降低功率开销、提高抗干扰裕度,且在一定信道误差范围内能够减低约35%的保密中断概率,具有较强的鲁棒性。     

IRS和人工噪声辅助的MIMO-SWIPT系统安全传输方案设计

针对多天线无线携能通信系统中能量收集节点作为潜在窃听者的信息安全问题，提出了一种智能反射面(Intelligent Reflecting Surface, IRS)和人工噪声辅助的物理层安全传输方案。首先考虑发射功率、能量收集门限以及IRS单位模约束，以最大化系统安全速率为优化目标，在合法用户直射链路不可用的情况下，联合设计发射端波束赋形矩阵、人工噪声协方差矩阵以及IRS相移矩阵，建模一非线性多变量耦合的非凸优化问题；接着利用均方误差准则等价转换非凸目标函数，并利用连续凸逼近方法(Successive Convex Approximation, SCA)处理非凸的能量收集约束；最后基于交替优化框架，分别用拉格朗日对偶方法和基于价格机制的优化最小化(Majorization-Minimization, MM)算法求解发射端变量和IRS端变量。仿真结果表明，与现有方案相比，所提算法能够在保障能量收集需求的同时大幅度提升系统的安全性能。     

认知MIMOME系统安全速率最大化算法研究

文章主要从安全速率（secrecy rate）最大化的角度研究了多输入多输出多天线窃听者（Multiple-Input Multiple-Output Multiple-antenna Eavesdropper,MIMOME）认知无线网络的物理层安全问题。针对在次用户的发送信号中加入人工噪声的安全策略,研究了实现系统安全速率最大化的优化问题。该优化问题属于非凸问题,本文提出了一种双层迭代优化算法,将内层问题通过求解一系列的半正定问题进行有效处理,而将外层问题变换为一个单变量的优化,从而通过一维搜索得到最优解。进一步,将该优化求解算法扩展到非理想信道状态信息情况,采用基于最差情况下的鲁棒人工噪声设计,保证在椭球不确定集内的所有信道实现均能够满足。最后仿真验证了该优化算法在理想和非理想信道状态信息下算法的有效性,与迫零人工噪声预编码优化算法相比,该算法可获得更高的安全速率。      

无人机辅助物理层安全下的保密性能优化

信息安全是影响物联网(IoT)应用的关键因素之一,物理层安全是解决物联网信息通信安全问题的有效技术。该文针对物联网中带有主动攻击的全双工窃听者,利用无人机(UAV)辅助发射人工噪声的方法,提升系统物理层安全性能。为了跟踪窃听者位置移动,首先采用贝叶斯测距和最小二乘法迭代估计窃听者位置,然后提出基于Q-learning的无人机轨迹优化算法,以达到在窃听者移动情况下系统保密性能最优。仿真结果表明,该算法能快速收敛,并且无人机能够跟踪窃听者移动来确定自身最佳位置,对窃听信道实施有效干扰,从而保证系统可达安全速率最大。     

携能网络中保障能效的缓存队列中继选择与能量分配方案

在无线携能（SWIPT）网络中,带有缓存队列的一对半双工SWIPT中继可以在一个时隙内完成信息同时收发,实现虚拟全双工通信。针对SWIPT虚拟全双工网络的资源分配问题,该文研究了缓存队列机制的最佳SWIPT中继选择与子载波能量分配方案。首先建立数学模型,参考注水因子辅助搜索算法,以最大化能效为目标,在满足能量、信息传输速率、最佳接收中继干扰等多个约束条件下,通过求解优化问题选择SWIPT最佳转发中继,同时得到最佳转发中继的子载波能量分配最优解。仿真结果表明,与最大化端到端可达速率为目标的联合资源分配算法相比,所提方案考虑了SWIPT网络中继间干扰。且当源端发送功率较大时,所提方案可以获得较高的能效。      

Dynamic Resource Allocation in OFDMA-Based DF Cooperative Relay Networks

This paper investigates the Resource allocation problem in OFDMA-based decode-and-forward cooperative communication systems. The objective is to maximize the sum throughput under the constraints of joint total transmission power and subchannels occupation, while maintaining the maximum fairness among multiple relay nodes. Since the optimal solution to this combinatorial problem is extremely computationally complex to obtain, we propose a low-complexity suboptimal algorithm that allocates subchannel and power separately. In the proposed algorithm, subchannel allocation over the relay nodes is first performed under the assumption of equal power distribution. Then, an optimal power allocation algorithm named multi-level water-filling is used to maximize the sum rate. The simulation results show that the performance of the proposed algorithm can approach asymptotically to that of the optimal algorithm while enhancing the fairness among all relay nodes and reducing computational complexity from exponential to linear with the number of subchannels. It is also shown that the proposed equal power distribution algorithm with subchannel permutation (SP) outperforms the one without SP.     

无人机交替中继通信及其轨迹优化和功率分配研究

为了提高无人机中继通信系统的频谱利用率,该文提出一种交替中继方法,通过两个无人机中继交替工作,轮流将信息从源端转发到目的端。研究联合优化无人机中继的飞行轨迹和各发射端的发射功率,协调两条中继链路的相互干扰,实现端到端的吞吐量最大化。涉及的优化问题受限于无人机的高度约束、机动约束、防碰撞约束以及各发射端的平均与峰值发射功率约束,是难以求得最优解的非凸优化问题。该文提出一种基于交替最大化和连续凸优化技术的高效迭代算法求解次优解,并用计算机仿真验证了所提算法的有效性。     

Resource Allocation for Decode-and-Forward Relaying Assisted Multi-cell Orthogonal Frequency Division Multiplexing Systems with Frequency Planning

In this paper we apply frequency planning to the resource allocation of multi-cell and multi-user relay enhanced orthogonal frequency division multiplexing systems and propose a low-complexity algorithm taking into account of interference coordination, subcarrier and power allocation. We divide each cell into three sectors and allow different subcarrier set that can be used by the users of one sector. Such a method can help to increase the distance among users that use the same subcarriers of adjacent cells, which can reduce the impact of co-channel interference to a certain extent. Therefore, the original problem can be decoupled into three independent sub-problems by means of frequency dividing and adaptive power allocation at base station nodes which can reduce the computing complexity greatly. In the process of resource allocation for single sector, the relationship of transmission power between base station and relay node is used to transform the max-min problem into standard closed expression. With the help of dual decomposition approach, water-filling theorem and iterative power allocation algorithm, the suboptimal solution of the primal problem can be achieved finally. Simulation results illustrate that our proposed algorithm achieves almost the same performance as the optimal resource allocation and reduce the computing complexity greatly. In addition, the proposed algorithm can ensure the users fairness of different sectors.     

Optimal designs of collaborative relay‐assisted multiuser beamforming for cellular systems

With careful calculation of signal forwarding weights, relay nodes can be used to work collaboratively to enhance downlink transmission performance by forming a virtual multiple‐input multiple‐output beamforming system. Although collaborative relay beamforming schemes for single user have been widely investigated for cellular systems in previous literatures, there are few studies on the relay beamforming for multiusers. In this paper, we study the collaborative downlink signal transmission with multiple amplify‐and‐forward relay nodes for multiusers in cellular systems. We propose two new algorithms to determine the beamforming weights with the same objective of minimizing power consumption of the relay nodes. In the first algorithm, we aim to guarantee the received signal‐to‐noise ratio at multiusers for the relay beamforming with orthogonal channels. We prove that the solution obtained by a semidefinite relaxation technology is optimal. In the second algorithm, we propose an iterative algorithm that jointly selects the base station antennas and optimizes the relay beamforming weights to reach the target signal‐to‐interference‐and‐noise ratio at multiusers with nonorthogonal channels. Numerical results validate our theoretical analysis and demonstrate that the proposed optimal schemes can effectively reduce the relay power consumption compared with several other beamforming approaches. Copyright © 2012 John Wiley & Sons, Ltd.     

Nearly optimal linear transceiver design for amplify‐and‐forward MIMO multiple‐relay systems under MMSE criterion

In this paper, we consider amplify‐and‐forward multiple‐input multiple‐output multiple‐relay systems, where all the nodes have multiple antennas. For enhancing link reliability, we address the problem of designing optimal linear transceiver to minimize the mean squared error (MSE) of symbol estimations subject to the total relay transmit power constraint. This problem is highly complex and has not been solved in the literature. We first simplify this optimization problem to one that takes a singular value vector and a unitary matrix as optimization variables. Then based on the analyses for the simplified problem, we develop an iterative algorithm consisting of one boundary optimization and one unitary matrix constrained optimization. We show analytically that the proposed iterative algorithm always converges, and the MSE is monotonically decreasing from one iteration to the next. Finally, numerical results demonstrate the nearly optimal performance of the proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

采用最优放大因子的全双工中继选择方案

在多中继协作通信系统中,提出一种基于放大转发协议的全双工中继选择算法并进行了相应的理论分析。由于全双工中继中自干扰的存在,为保证通信的质量,首先利用传统的最大化边界信干噪比算法选择一个中继,然后利用中继的最优功率放大因子来减小自干扰对系统的不利影响。基于最优放大因子的全双工中继选择方案在系统中断概率、中继节点功率消耗、目的节点接收信干噪比方面都优于采用最大化边界信干噪比的系统。最后,我们利用蒙特卡洛仿真结果证明了该选择算法的优势。      

Network planning for mobile multi‐hop relay networks

In this paper, the coverage problem of network planning in mobile multi‐hop relay networks is defined on the basis of integer linear programming. In order to provide desired utilities and also meet deployment limitations for network planning, we propose a supergraph tree algorithm to place base stations and relay stations at the lowest cost position. Furthermore, another algorithm for avoiding the interference between base stations, which is called interference aware tree algorithm is also proposed. Both the proposed algorithms are formulated on the basis of a graph theoretic technique and analyzed in the simulation results. The results show that the supergraph tree algorithm provides the lowest construction cost with different network scenarios, and the interference aware tree algorithm provides the highest communication quality for mobile multi‐hop relay infrastructure‐based communication network planning. Copyright © 2013 John Wiley & Sons, Ltd.     

多天线中继系统中人工噪声辅助的安全波束成形

针对放大转发中继系统中转发信息易被窃听者截获的问题,提出了在中继节点处采用人工噪声辅助的安全波束成形方法。该方法以系统的安全速率最大化（SRM, secrecy rate maximization)为目标,在中继节点的总功率和单个天线功率受限情况下,联合设计最优的中继波束成形矩阵和人工噪声协方差矩阵。由于该SRM问题非凸,设计了双层优化算法,其中采用一维搜索解决外层优化问题,采用半定松弛及内点法解决内层优化问题。理论推导证明,内层优化问题总存在秩为1的最优解,即所采用的松弛技术是紧的。仿真结果表明所提的方法可以显著提高系统的安全性能。     

基于资源分配和功率控制的D2D中继选择

为优化蜂窝用户通信与设备直传(D2D)中继通信共存下的同频干扰问题,满足蜂窝用户容量要求,提出了一种基于能效的联合资源分配和功率控制的D2 D中继选择算法.该算法首先对等效D2 D中继链路进行资源分配,减小算法复杂度的同时使得D2 D链路对蜂窝链路产生的干扰最小;然后以资源分配结果和功率控制算法为依据进行中继选择.该方案不仅考虑了D2 D中继链路的能效问题,而且还同时考虑到了对蜂窝链路的干扰问题.通过仿真验证,所提算法不仅能有效提升D2 D中继链路的能效值,同时降低了对蜂窝用户的干扰.