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。     

全双工MIMO中继系统高性能的波束成型算法

为了更好地抑制全双工多入多出技术(MIMO)中继系统的自干扰,提高信息传输速率,提出了一种新型的波束成型组合算法。该组合在源节点和目的节点采用奇异值分解的波束成型向量,而在中继站采用基于最大化信干噪比接收波束成型来抑制中继端的自干扰,以及最大化信泄噪比发射波束成型矩阵来减少中继发送端泄漏到中继接收机的信号组合波束成型算法。为了降低复杂度,随后引入了交替迭代结构来进一步优化中继接收和发送波束成型矩阵,并比较了不同组合波束成型方案的和速率性能。仿真结果表明,与现存的波束成型组合相比,当干噪比较低时,提出的组合算法能够提供更优的和速率性能。     

基于主被动波束成形联合优化的双RIS辅助抗干扰通信方法

针对双可重构智能表面（RIS）辅助的无线通信系统,提出了基于主被动波束成形联合优化的抗干扰通信方法。以接收信干噪比最大化为目标,构建主被动波束成形的联合优化问题。基于交替优化算法,将联合优化问题分解为3个子问题来迭代求解。通过半定松弛算法求解各RIS的近似最优被动反射向量;基于广义瑞利商求解基站的最优主动波束成形向量。仿真结果表明,所提方法优于传统的单RIS辅助抗干扰通信方法。     

多小区大规模协同功率分配及波束成形算法

针对大规模多输入单输出的多点协作下行系统,本文主要研究协同波束成形和功率控制,以达到最大化最差用户信干噪比的目的。为了求解原始下行的非凸优化问题,首先将原始优化问题转化成等价的上行优化问题进行求解。尽管在有限系统里可通过迭代算法获得波束矢量和发射功率,但是该算法依赖于瞬时信道信息,功率也需要瞬时更新。为了减少功率更新计算复杂度,本文进一步利用随机矩阵理论,提出了只需要依赖统计信道信息的算法来获得发射功率。数值仿真验证了单基站功率约束下所提算法的有效性以及相对于最大比发送算法的优越性。      

毫米波MIMO通信感知一体化联合波束成形设计北大核心CSCD

考虑一个毫米波多输入多输出（Multiple-InputMultiple-Output,MIMO）通信感知一体化系统,同时进行多目标感知与多用户通信。首先,基于毫米波MIMO几何信道模型,在满足总功率和多用户信干噪比的约束下,最小化MIMO感知发射波束图匹配误差和互相关图。然后,针对建立的联合波束成形设计问题,采用半正定松弛算法进行求解,得到通信感知一体化波束成形矩阵。最后,仿真结果验证了联合波束成形设计的有效性。     

基于对偶理论的多点协同联合发送波束成形算法

该文针对单基站功率约束的多点协同联合发送多输入单输出干扰下行链路系统,利用拉格朗日对偶理论研究了下行链路最大化最小信干噪优化问题与虚拟上行链路最小化最大信干噪比优化问题间的对偶关系。基于对偶关系和次梯度理论,提出了一种求解虚拟上行链路最小化最大信干噪比优化问题的内外层交替迭代优化波束成形算法;同时,给出了所提算法的收敛性证明;利用实数浮点运算理论分析了所提算法的复杂度;数值仿真验证了所提算法的有效性。     

毫米波MIMO系统中迭代最小均方误差混合波束成形算法

混合波束成形结构能有效解决毫米波MIMO系统中射频链路受限的问题,但要设计性能较优的混合波束成形算法仍然存在困难.为了实现更高的频谱利用率,提出了一种性能较优的迭代最小均方误差(Alt-MMSE)混合波束成形算法.该算法利用数字矩阵的正交特性,首先进行初始数字矩阵设计,然后通过最小化发送信号与接收信号的均方误差不断迭代更新数字矩阵,在每一次迭代过程中,通过更新后的数字矩阵得到模拟矩阵的相位信息.仿真结果表明,与OMP混合波束成形算法和基于矩阵分解的混合处理方案相比,该算法具有更优的性能且更接近于纯数字波束成形.     

基于MSMSE的MIMO放大转发双向中继信道中波束成形设计

本文主要研究了基于最小化均方误差和准则的MIMO放大转发双向中继信道中的波束成形向量(矩阵)的设计.我们分别在集中式与分布式两种应用环境中提出了一套解决方案.在集中式方案中,多个中继之间完全协作,因此将多个单天线中继等效成一个多天线的中继节点,设计了基于所有中继天线的总功率控制的波束成形向量(矩阵).在分布式方案中,中继节点之间无协作,分别设计了基于所有中继总功率控制波束成形向量(矩阵)和基于单个中继功率控制的波束成形向量(矩阵).仿真表明,通过波束成形设计,可以显著提高通信节点平均误码率.由于中继节点之间的完全协作,集中式方案要优于分布式方案.但是,由于中继结构简单,分布式方案更易于在实践中应用.     

考虑收发机损耗的多小区多用户下行链路波束成形算法

在现有收发机损耗模型基础上以最小化最差用户均方误差或者最小化用户均方误差之和为优化目标,设计一种考虑收发机残留损耗的多小区多用户下行链路波束成形算法。通过将优化问题转化成二阶锥规划的标准形式,并设计分层优化迭代算法来求解原始问题。数值仿真表明,相对于传统收发机的波束成形算法而言,所提算法将极大地减小收发机损耗对系统性能的影响,进而显著提高系统性能。     

基于功率的双向AF MIMO中继系统收发器设计

针对多用户对双向放大转发多输入多输出中继系统中用户和中继的收发器联合设计问题,基于节省功率的目的,提出了在满足每个用户均方误差约束的条件下最小化用户和中继总功率的优化问题。由于所形成的优化问题是非凸的,难以求得全局最优解,因此将原问题分解为3个便于处理的子问题,对这3个子问题分别进行求解,在此基础上提出了一种基于交替优化的迭代算法去求解原问题。仿真结果表明,所提算法相较于其他算法可以有效地节省用户和中继的总功率。     

Beamforming design for energy-constrained full-duplex two-way relaying system

A beamforming design was proposed under simultaneous wireless information and power transfer (SWIPT) protocol.A utility optimization problem was considered aiming to maximize the harvested energy by jointly optimizing the beamforming matrix,the power splitting ratio at the relay and the transmit powers at the sources.Since the formulated joint optimization problem was nonconvex,it was difficult or even intractable to obtain the global optimal solution.To overcome this issue,the objective problem into three subproblems was decoupled which could be solved by the proposed semidefinite relaxation technique and the derived constraints activation solution,respectively.The solution was finally obtained with the proposed convergent iterative algorithm.Simulation results show that the proposed joint optimization scheme achieves the optimal performance.Compared with the traditional half-duplex (HD) algorithm,the proposed algorithm can obtain 2~3 times energy harvesting (EH) efficiency improvement,while the computational complexity increases slightly.     

Distributed Beamforming for Relay Networks Based on Second-Order Statistics of the Channel State Information

In this paper, the problem of distributed beamforming is considered for a wireless network which consists of a transmitter, a receiver, and $r$ relay nodes. For such a network, assuming that the second-order statistics of the channel coefficients are available, we study two different beamforming design approaches. As the first approach, we design the beamformer through minimization of the total transmit power subject to the receiver quality of service constraint. We show that this approach yields a closed-form solution. In the second approach, the beamforming weights are obtained through maximizing the receiver signal-to-noise ratio (SNR) subject to two different types of power constraints, namely the total transmit power constraint and individual relay power constraints. We show that the total power constraint leads to a closed-form solution while the individual relay power constraints result in a quadratic programming optimization problem. The later optimization problem does not have a closed-form solution. However, it is shown that using semidefinite relaxation, this problem can be turned into a convex feasibility semidefinite programming (SDP), and therefore, can be efficiently solved using interior point methods. Furthermore, we develop a simplified, thus suboptimal, technique which is computationally more efficient than the SDP approach. In fact, the simplified algorithm provides the beamforming weight vector in a closed form. Our numerical examples show that as the uncertainty in the channel state information is increased, satisfying the quality of service constraint becomes harder, i.e., it takes more power to satisfy these constraints. Also our simulation results show that when compared to the SDP-based method, our simplified technique suffers a 2-dB loss in SNR for low to moderate values of transmit power.      

Achievable rate region with secrecy constraints for secure communication in two‐way relay networks

In this paper, we consider a two‐way relay network consisted of two sources and multiple relays in the presence of an eavesdropper, where the cooperative beamforming strategy is applied to exploit the cooperative diversity to support the secure communication as illustrated in Figure 1. Naturally, we are interested in the beamforming strategy and power allocation to maximize the achievable sum secrecy rate. However, the corresponding problem is equivalent to solve a product of three correlated generalized Rayleigh quotients problem and difficult to solve in general. Because of the openness of wireless medium, the information rate leakage to the eavesdropper cannot be canceled perfectly. To some extent, ‘almost perfect secrecy’, where the rate leakage to the eavesdropper is limited, is more interesting from the practical point of view. In this case, we concern ourself mainly the achievable rate region for general case where the rate at the eavesdropper is regarded as the measurement of secrecy level. Two beamforming approaches, optimal beamforming and null space beamforming, are applied to investigate the achievable rate region with total power constraint and the rate constraint at the eavesdropper, which can be obtained by solving a sequence of the weighted sum inverse‐signal‐to‐noise‐ratio minimization (WSISM) problem. Because of the non‐convexity of WSISM problem, an alternating iteration algorithm is proposed to optimize the relay beamforming vector and two sources' transmit power, where two subproblems need to be solved in each iteration. Meanwhile, we provide the convergence analysis of proposed algorithm. Through the numerical simulations, we verify the effectiveness of proposed algorithm. Copyright © 2013 John Wiley & Sons, Ltd.     

多跳多中继无线网络中的协作波束形成技术

针对多跳多中继无线网络中的协作波束形成技术进行研究.在基于放大转发机制的三跳协作通信系统中,对2个中继节点簇的协作波束形成矢量进行联合设计,以求在目标节点获得最大的接收信噪比.该方法首先将原始优化问题加以推导简化,然后应用半定规划方法求解获得协作波束形成矢量的次优解,并结合对分搜索算法加以改进.仿真结果表明,提出的协作波束形成方法可取得明显优于固定放大增益中继策略的接收信噪比.     

Secure resource allocation in hybrid energy-harvesting relay and full-duplex receiver

Taking into account the wireless physical layer security in energy-constrained relaying systems,a secure resource allocation scheme was proposed under simultaneous wireless information and power transfer (SWIPT) protocol.The utility optimization problem was considered aiming to maximize the secrecy rate by jointly optimizing the power splitting (PS) ratio and the transmit powers under the constraint of the transmit powers of the nodes and the harvested energy of the relay.The objective problem,which is non-convex,was decoupled into two subproblems.One was to optimize the PS ratio,another was to optimize the transmit powers.The optimal solution of the subproblems can be obtained in the closed-form.Then,the suboptimal solution is obtained with the proposed convergent iterative algorithm.Simulation results show the effects of artificial noise signal,residual self-interference signal,transmit power of nodes,amplification factor of relay and other factors on the security performance.Compared with the traditional gradient descent algorithm,the proposed algorithm can reduce more than 80% of the computational load,while the algorithm has the slightly better performance.     

基于硬件损伤的MIMO异构网络波束成形算法

由于多输入多输出(MIMO)异构网络能够提高系统容量和实现更多的用户接入,因此受到了学术界和工业界的广泛关注,从而成为下一代通信系统的关键技术之一。然而,由于放大器非线性、相位噪声和I/Q不均衡等因素的影响,这类硬件损伤成为制约当前MIMO异构网络波束成形性能进一步提升的瓶颈。为了解决该问题,该文提前将硬件损伤考虑到MIMO异构网络波束成形算法设计当中。首先,考虑了每个基站的最大发射功率约束和每个用户的最小信干噪比约束,建立了一个含硬件损伤参数的系统总能耗最小的资源优化问题。其次,利用等价变换和半正定松弛方法,将原非凸问题转化为凸优化问题进行求解。仿真结果表明,与完美硬件条件下的波束成形算法对比,所提算法具有较好的抗硬件损伤能力和较低的中断概率。     

Multiple Peer-to-Peer Communications Using a Network of Relays

We consider an ad hoc wireless network consisting of d source-destination pairs communicating, in a pairwise manner, via R relaying nodes. The relay nodes wish to cooperate, through a decentralized beamforming algorithm, in order to establish all the communication links from each source to its respective destination. Our communication strategy consists of two steps. In the first step, all sources transmit their signals simultaneously. As a result, each relay receives a noisy faded mixture of all source signals. In the second step, each relay transmits an amplitude- and phase-adjusted version of its received signal. That is each relay multiply its received signal by a complex coefficient and retransmits the so-obtained signal. Our goal is to obtain these complex coefficients (beamforming weights) through minimization of the total relay transmit power while the signal-to-interference-plus-noise ratio (SINR) at the destinations are guaranteed to be above certain predefined thresholds. Although such a power minimization problem is not convex, we use semidefinite relaxation to turn this problem into a semidefinite programming (SDP) problem. Therefore, we can efficiently solve the SDP problem using interior point methods. Our numerical examples reveal that for high network data rates, our space division multiplexing scheme requires significantly less total relay transmit power compared to other orthogonal multiplexing schemes, such as time-division multiple access schemes.     

Robust Joint Design of Transmit Beamforming and Receive Filter for TB-MIMO STAP Radar

In this paper, we consider the joint design of transmit beamforming and receive filter for transmit beamspace (TB) multiple-input multiple-output (MIMO) radar red space-time adaptive processing (STAP) under the target information uncertainty. The associated robust joint design problem is formulated by maximizing the signal-to-interference-plus-noise ratio (SINR) to guarantee the target detection performance. An iterative optimization procedure is developed to resolve the NP-hard joint design problem. The optimized transmit beamforming weight vector and receive filter exhibit superior performance in terms of output SINR. Several simulation examples are presented to demonstrate the effectiveness of the proposed algorithm.

     

基于IRS辅助的SWIPT物联网系统安全波束成形设计

为满足绿色万物互联的智能信号处理部署和物理层安全的新要求,针对基于智能反射面辅助的无线携能通信物联网系统中可持续能量供应紧缺问题,提出了一种安全波束成形设计方法。考虑保密速率、发射功率和IRS反射相移约束,以最大化能量采集器采集功率为目标,联合优化基站发射波束成形矩阵和干扰机协方差矩阵以及IRS相移,将优化问题建模为具有二次型约束的非凸二次型规划问题。利用松弛变量、半定松弛法、辅助变量和序列参数凸逼近法将非凸的二次型问题转化为等价的凸问题,并提出一种交替迭代优化算法获取原问题的可行解。仿真结果表明,所提算法能够快速收敛,且与基准方案相比能有效地提升性能。     

User-centric harvested energy-efficiency maximisation for secure SWIPT transmissions

ABSTRACT

In this paper, simultaneous wireless information and power transfer (SWIPT) transmissions with multiple-input single-output transceiver pairs are considered. In each pair, a multi-antenna transmitter sends data and energy to a single-antenna receiver with a signal-splitting structure and a non-linear energy harvesting model. Each transceiver pair tries to achieve high individual harvested energy efficiency, and uses artificial noise (AN) to protect the information from being overheard by other users that cooperate like a virtual eavesdropper. The weighted sum user-centric harvested energy-efficiency maximisation problem is formulated under constraints on the required signal-to-interference-plus-noise ratio (SINR) at each receiver, plus a limited SINR for virtual eavesdroppers and limited transmit power at each transmitter. The optimal precoding beamforming, AN, and signal-splitting factors are obtained by two proposed algorithms. The first solution exploits semidefinite relaxation and sequential parametric convex approximation techniques to convert the non-convex problem to a series of convex subproblems with matrix variables. We obtain optimal beamforming vectors along with an optimal covariance matrix for AN. The second solution directly utilizes beamforming approximation and obtains a low complexity solution for the convex subproblem. Moreover, we need to apply the feasible point pursuit method. Finally, numerical evaluations are provided in comparison with some benchmark schemes.