面向6G的超奈奎斯特波形及其检测技术

6G系统峰值数据传输速率需求为1Tbps,对通信系统的容量和频谱效率提出了巨大挑战。由此,超奈奎斯特传输作为一种高效的传输方式备受瞩目,其独特之处在于能够在不增加带宽和天线的情况下提升系统容量和频谱效率。从单载波传输到多载波传输,对超奈奎斯特传输的机理与波形、现有模型的干扰及相应的信号检测技术进行重点论述。对超奈奎斯特传输在载波恢复、同步、正交频分复用和多输入多输出方面的发展进行综述。最后,探讨超奈奎斯特传输在未来移动通信系统的发展发向和潜在的研究思路。     

基于对称逐步超松弛的低复杂度信道估计算法

随着大规模多输入多输出系统基站端天线数量的增大,系统的信道容量和频谱效率随之增加.传统的信道估计算法,如最小均方误差涉及到高维矩阵的求逆运算,特别在大规模多输入多输出系统中,导致系统复杂度过高.为降低大规模多输入多输出系统的计算复杂度,本文提出了一种基于对称逐步超松弛的低复杂度信道估计算法,该方法以迭代的形式有效避免高...     

高阶调制的多天线系统中的半定松弛检测算法

提出了一种半定松弛检测算法，分别从秩松弛和Lagrange双对偶规划两种途径，给出了这一检测算法的推导过程。复杂度分析和仿真结果表明，该算法能够在计算复杂度与误码性能之间取得很好的折衷。     

基于失配误差正交分解的稳健自适应波束形成

针对自适应波束形成中期望信号导向矢量的失配问题,该文提出了一种利用失配误差的正交分量来逐步修正期望信号导向矢量的自适应波束形成方法。该方法首先构造两个正交子空间,正交分解失配误差以后,通过引入松弛变量,把修正过程转化为解决迭代的二次凸优化问题。提出的方法没有假定失配误差模约束或概率约束,从而避免了上限估计和概率分布建模。仿真结果验证了方法的有效性。     

基于±1二次规划的低复杂度球形解码算法

从MIMO检测的±1二次规划模型出发,推导了最大似然MIMO检测最优解的必要条件。在此基础上提出了一种基于必要条件的球形解码改进算法,该算法在球形解码剪枝策略的基础上利用必要条件对树型搜索的节点进行进一步剪枝,从而明显降低了运算复杂度,而不降低球形解码检测算法的误比特率性能。     

基于成本约束的虚拟网映射策略及竞争分析

为实现物理网提供商长期收益的最大化,单个虚拟网的映射成本和接入控制策略最为关键,但在之前的研究中,资源价格定义不能反映资源供求关系,不利于物理网资源的有效利用,且接入控制策略没有综合考虑成本和收益的关系.为此,首先基于凸二次规划松弛方法,设计以映射成本最小化为目标的单虚拟网映射方案求解的近似算法;然后,针对动态到达的单虚拟网构建请求,基于影子价格的物理网资源定价策略,用上述近似算法求出映射方案,并基于映射成本约束的虚拟网接入控制策略,完成竞争算法设计,并给出算法的竞争比分析.实验表明,所提方法能使物理网资源得到有效利用,进而提高虚拟网构建请求的接受率和物理网提供商的长期收益.     

基于最小L1范数的方法估计码片内延时

所要传输的已知单周期PN码信号是通过多条带有加性噪声的路径到达接收端,因此问题就在于估计路径的数目以及与每一条路径相对应的小于单个码片间距的时延和衰落幅度.文中在基于最小L1范数的加性调整条件下,提出了一种新的去卷积方法.由此衍生出的最优化问题则通过转化为二次规划,利用其标准程序进行简便快捷的求解未知量.在复杂的条件下这种方法比其他方法更加的适用.     

基于连续干扰消除的超奈奎斯特信号迭代接收技术

为了消除超奈奎斯特(FTN)调制技术引入的干扰,设计了基于连续干扰消除(SIC)的Tur-bo迭代均衡接收机.对于单载波FTN系统,首先建立了FTN信号等效模型,然后接收机根据等效模型和译码器输出的软信息重建干扰,并通过多次连续干扰消除和译码逐步消除,具有较低的复杂度.同样地,在多载波FTN系统中,根据译码器输出的软信息和成型脉冲的时频特性重建引入的干扰并通过多次迭代给予消除.仿真表明,在加速因子不是太小时,基于SIC-Turbo均衡的接收机能够有效消除干扰,可获得近似正交传输时的误码性能.     

TH预编码的超奈奎斯特系统残余干扰消除算法

超奈奎斯特(Faster-Than-Nyquist, FTN)技术能够有效提高传输系统的频谱效率,然而代价是引入了严重的码间串扰(Inter-Symbol Interference, ISI)。在基于Ungerboeck模型的FTN系统中的发送端使用TH预编码(Tomlinson-Harashima Precoding, THP)并不能完全有效消除FTN系统所引入的ISI,会存在残余ISI。对此,针对FTN系统中的残余干扰提出了两种接收端检测算法,分别是基于后向串行干扰消除(Backward Serial Interference Cancellation, BSIC)的无迭代检测算法和基于连续干扰消除(Successive Interference Cancellation, SIC)的Turbo迭代均衡改进算法,并通过蒙特卡洛方法寻找最优的扩展取模间隔。计算机数值仿真结果表明,在选定的扩展取模间隔下,两种接收端检测算法在FTN系统的加速因子为0.8和0.9时均能有效消除FTN技术所引入的ISI,其误码率趋近于奈奎斯特正交传输性能。     

无源时差定位方程的半定松弛解法

针对基于到达时差量测的多站无源定位系统,提出了一种基于半定松弛的时差定位方程求解方法.该方法首先将关于目标位置估计的非凸二次优化问题转换成等价的非凸半定规划问题,然后通过秩1松弛得到一个凸优化问题,最后对松弛半定规划问题的最优解进行秩1近似,从而提取出最终的目标位置估计.计算机仿真结果表明这种松弛解法可以有效求解目标位置.     

Low-complexity FTN receivers based on frequency domain iterative decision feedback equalization

Faster-than-Nyquist (FTN) signaling can improve the system effectiveness without reducing the system reliability,but the fierce inter-symbol interference (ISI) introduced by it may cause that the complexity of the optimal receiver is intolerable.An effective low-complexity FTN receiver is iterative block decision feedback equalizer (IBDFE),which can achieve performance close to the optimal receiver with much lower complexity,but its complexity can be further reduced.Therefore,a reduced-complexity IBDFE (RC-IBDFE) was proposed for FTN communication systems,which was based on IBDFE,but introduced a simplified method to design the feedforward and feedback filters.When packing factor is τ={0.8,0.7},numerical results and analysis indicate that,compared with IBDFE,RC-IBDFE has stronger robustness,its complexity is reduced by {45.7%,25%},and its performance gain is {0.605 4,0.193 6} dB when the bit error rate (BER) is 10^-5.Compared with the existing low-complexity IBDFE (LC-IBDFE),RC-IBDFE has stronger robustness,its complexity is reduced by {13.6%,-25.8%},and its performance gain is {0.289 7,0.531 2} dB when the BER is 10^-5.     

Characterization and modeling of static and cyclic relaxation in nonconductive adhesives

Adhesive interconnections are considered to be attractive alternatives to lead or lead-free solder interconnects because of their lower processing temperatures and extendability to fine pitch applications. However, reliability issues, such as moisture-induced delamination and viscoelastic relaxation of the adhesive in both steady-state and cyclic loading, continue to pose a challenge to widespread implementation. To date, the static and cyclic relaxation characteristics of nonconductive adhesives (NCAs) are yet to be understood. This paper attempts to provide insights into this static and cyclic relaxation behavior through experimental characterization and modeling. The viscoelastic property of a typical NCA material was characterized, and a simulation program with integrated circuit emphasis (SPICE) modeling program was used to model the cyclic relaxation behavior. The modeling results were successfully validated with a series of experiments. This showed that cyclic relaxation of the adhesive can be successfully modeled using linear-viscoelastic property. The phenomenon of slower relaxation of the adhesive under cyclic loading than that in static loading suggests that accelerated reliability testing used in solder-joint fatigue durability investigations may not be directly applicable to the adhesive interconnections. A rework methodology applicable to adhesive interconnects using cyclic loading has also been proposed.     

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.     

密码理论算法综述

概要介绍了密码理论算法的发展现状,重点讨论了密码算法中的布尔函数,最后总结了各种密码体制的应用。     

BER Performance of Finite in Time Optimal FTN Signals for the Viterbi Algorithm

In this article, we consider the faster than Nyquist (FTN) technology in aspects of the application of the Viterbi algorithm (VA). Finite in time optimal FTN signals are used to provide a symbol rate higher than the “Nyquist barrier” without any encoding. These signals are obtained as the solutions of the corresponding optimization problem. Optimal signals are characterized by intersymbol interference (ISI). This fact leads to significant bit error rate (BER) performance degradation for “classical” forms of signals. However, ISI can be controlled by the restriction of the optimization problem. So we can use optimal signals in conditions of increased duration and an increased symbol rate without significant energy losses. The additional symbol rate increase leads to the increase of the reception algorithm complexity. We consider the application of VA for optimal FTN signals reception. The application of VA for receiving optimal FTN signals with increased duration provides close to the potential performance of BER, while the symbol rate is twice above the Nyquist limit.     

PSI/SI中描述符的用法浅析

介绍PSI／SI信息的概念、组成及各张表的作用，从语法角度简单说明SI表的层次结构，并列举出有线数字电视系统中常用的描述符及其表示的信息，最后举例说明描述符在实际网络运营中的灵活运用。