基于帕累托最优的雷达-通信共享孔径研究

针对雷达-通信综合射频系统,该文提出一种基于环境信息的共享孔径动态分配方法。首先基于帕累托最优理论将共享孔径分配建模为一个多目标优化问题,并建立了雷达阵列方向图的峰值旁瓣电平和多输入多输出(MIMO)通信系统的信道容量两个优化目标函数。然后提出一种基于整数编码的改进粒子群算法,通过迭代求解以帕累托前沿的形式给出一组最优解,供决策者根据任务需求从中选出一个最满意的解。最后,仿真结果验证了该方法的有效性。     

协作式中继增强MIMO通信系统的联合波束成形

本文对协作式中继辅助的多输入多输出(Multiple-input Muhiple-output,MIMO)通信中的联合波束成形问题进行了研究.首先推导了接收信噪比的下界,并基于该下界建立了联合波束成形的数学模型;然后推导了分布式波束成形的最优方案;最后设计了联合优化信源的多天线波束成形和协作式中继的分布式波束成形的算法,从而获得联合波束成形方案.计算机实验仿真表明所提联合波束成形方案获得明显的性能增益.     

多用户中继系统中联合收发机的设计方案

在多用户中继系统中,根据最小均方误差(MMSE)准则,提出了一种考虑直接路径的联合收发机设计方案.给出了迭代算法,对中继发射机和用户接收机进行了联合优化,其中用户接收机是用来接收合并源端发送信号和中继发送信号.数据仿真结果表明,提出的方案与不考虑直接路径的收发机方案以及其他已知的LMMSE方案相比,在均方误差(MSE)和误码率(BER)性能方面,有较大的提高.     

一种基于嵌套晶格码的MIMO中继多用户矢量预编码设计

针对多输入多输出(MIMO)中继多用户系统的多址传输问题,为了提高系统可达速率和误码率性能,该文利用嵌套晶格码具有可达加性高斯白噪声信道容量的特性,设计一种基站和中继联合预编码的方法。基站端的嵌套晶格码结合矢量扰动(VP)预编码,以控制发送信号的功率。由于矢量扰动预编码和嵌套晶格码都存在相同的模运算步骤,因此在中继端的模运算抑制噪声功率的同时消除了冗余矢量。接着实现中继联合迫整数预编码方法,这种基站/中继混合预编码技术能够控制等效噪声功率,实现对蜂窝用户的有效信号传输。更进一步地,在给出整系数矩阵和扰动矢量矩阵的计算方法后,以最大化系统可达速率为目标对基站和中继的功率实现最优分配。实验结果表明,该方案在可达速率和误码性能方面优于现有方案。     

中继辅助的MIMO系统联合最优的 功率分配研究

本文对中继辅助的多输入多输出(MIMO)系统中信源与中继的联合最优功率分配问题进行了研究.首先,基于系统容量最大化准则提出相应代价函数,并证明了该代价函数仅仅对于部分参数是凸的,而对于全局参数是非凸的.然后,通过推导系统容量的下界,给出了一个新的代价函数,从而将非凸问题转化为一个联合凸优化问题.最后,利用凸优化方法获得了联合功率分配问题的全局最优解.计算机仿真表明,与现有方案相比,所提方案获得了更好的吞吐量性能.     

认知无线电网络中基于均方误差的预编码设计

基于认知无线电的概念,研究了一个多中继的认知无线电场景,设计了基站与中继的预编码矩阵,来最小化具有最大均方误差(MSE)的次用户的MSE值,同时保证主用户的MSE小于一定的阈值且中继的功率满足约束条件,将此优化问题转化为一个凸优化问题,并通过凸优化软件包来获得基站和中继预编码矩阵的最优数值解。最后,仿真结果验证了所提方案的有效性。     

单中继多用户MIMO系统中继预编码新方案

针对单中继多用户多输入多输出(MIMO)通信系统中用户间干扰问题,提出了一种可以有效抑制用户间干扰的中继接收和预编码方案。该方案在中继端对信号进行迫零(ZF)接收,利用最大化信漏噪比(SLNR)准则设计中继端预编码向量,并针对难以获得最优解的情况,利用迭代解出次优解。仿真结果表明,与中继端ZF预编码相比,SLNR预编码更好地抑制了用户间干扰,相同和速率性能下,基站发送端功率比ZF预编码减少4 dB,具有实用价值。     

基于上行多用户大规模MIMO系统能效优化算法

针对上行多用户大规模多输入多输出（MIMO）系统,提出了基于能效优化的资源分配方法。所提方法采用迫零(ZF)接收,以最大化系统能效下界为准则,系统功率消耗考虑电路功率消耗和发射功率消耗2部分,通过联合调整基站端的发射天线数和用户的数据速率来优化能效函数。首先,根据目标函数的性质,证明全局最优速率分配和天线数的存在性和唯一性,然后,根据分数规划的性质,把原始的分数最优化问题转换成减式形式,进而提出一种新的迭代算法。仿真结果表明,所提算法以较少迭代次数取得了接近最优算法的性能。     

基于两阶段帕累托优化的卫星下行链路功率分配方法

多波束卫星下行链路在实现高传输速率和低功耗之间相互制约,是影响多波束卫星系统通信性能的重要因素之一.本文提出两阶段多波束卫星下行链路多目标功率分配方法,建立多波束卫星下行链路功率分配模型,第一阶段采用凸优化算法实现下行链路传输速率的优化匹配,将传输速率匹配的解作为第二阶段启发式算法的初始解,得出的帕累托解可表示优化后的性能,为链路传输速率和功耗提供了平衡点.研究结果表明,在相同传输速率条件下,两阶段优化方法将链路功耗降低了17.6％,且收敛速度较快.     

协作通信中突发短帧信号的直接盲恢复

为解决中继协作通信系统中突发短帧(SBD)信号的检测问题,该文提出一种基于半正定松驰(SDR)的信号直接盲恢复方法。该方法可在信道状态信息和信号统计量信息缺失情况下直接盲恢复突发短帧数据序列。首先给出了单中继协作通信系统中SBD信号盲检测的数学模型;然后推导了高阶正交幅度调制(QAM)信号的最小二乘估计目标函数,并应用SDR法求解该优化问题,SDR法所得低秩解可有效逼近最优解。最后,仿真结果表明该方法效果良好并具有快速收敛性,所提出的方法为突发短帧信号盲检测提供了一种借鉴思路。     

Joint design of precoder and receiver in cognitive radio networks using an MSE criterion

We consider a single-user multiple-input multiple output (MIMO) transmission from secondary base station (SBS) in cognitive radio network where there is one primary user to which spectrum is licensed. It is assumed that coexistence of secondary network is allowed if interference power from the secondary network measured at primary user (PU) can be kept below a given threshold. In this paper, joint design problem of precoder and receiver is treated using mean-squared error (MSE) criterion between transmitted signal and its estimate at the receiver. Due to constraint on interference power measured at the PU, it is not possible to find an optimal solution in closed form. Therefore, a suboptimal solution with low complexity is proposed in closed form. Simulation results show that the MSE and bit error rate (BER) performances of the proposed scheme are 1.5-4.0 dB better than those of a conventional capacity-maximization scheme when the received signal-to-noise ratio (SNR) is high, and they converge to their lower bounds, i.e., those of an MSE-based scheme without considering the PU interference constraint, as the received SNR increases.     

MIMO中继系统中基于失真信道的联合收发机设计

在MIMO中继系统中,基于完全信道状态信息的基站、中继节点和终端联合收发机设计方案能够改善系统的误比特率性能,在放大转发(AF)中继的基础上提出了一种基于不完全信道状态信息的联合收发机设计方案.新方案在基站和中继节点的功率都受限条件下,将信道估计误差建模为高斯随机变量,以最小均方误差(MMSE)为准则,采用迭代算法,得到了基站预编码矩阵、中继转发矩阵和终端解码矩阵.该方案与不考虑信道估计误差的方案相比,能够有效地改善系统的均方误差和误比特率性能.     

接收端配备滤波器的分布式波束形成技术

基于频率选择性信道中由一个发射节点、一个目标节点和多个中继节点构成的中继网络,该文提出一种新型的分布式波束形成技术。该技术除了在中继节点上采用滤波而后转发的中继数据中转策略之外,在接收节点也配备一个有限长响应(Finite Impulse Response, FIR)滤波器,共同均衡发射节点与中继节点以及中继节点与接收节点之间的频率选择性信道。该文中,此两种滤波器将得到联合优化以提高接收节点的服务质量,并同时满足中继节点的发射功率限制。仿真结果表明,相较于放大而后转发以及滤波而后转发但无接收滤波器的波束形成器而言,所提波束形成技术极大地提高了频率选择性信道中中继网络的性能。     

VLSI implementation of a new LMS-based algorithm for noise removal in ECG signal

Least mean square (LMS)-based adaptive filters are widely deployed for removing artefacts in electrocardiogram (ECG) due to less number of computations. But they posses high mean square error (MSE) under noisy environment. The transform domain variable step-size LMS algorithm reduces the MSE at the cost of computational complexity. In this paper, a variable step-size delayed LMS adaptive filter is used to remove the artefacts from the ECG signal for improved feature extraction. The dedicated digital Signal processors provide fast processing, but they are not flexible. By using field programmable gate arrays, the pipelined architectures can be used to enhance the system performance. The pipelined architecture can enhance the operation efficiency of the adaptive filter and save the power consumption. This technique provides high signal-to-noise ratio and low MSE with reduced computational complexity; hence, it is a useful method for monitoring patients with heart-related problem.     

无线携能网络中一种非线性能量收集与信息传输均衡策略

在无线携能(SWIPT)网络中,节点通常采用非线性能量收集。论文首先建立了非线性能量收集模型,提出了时隙切换与静态功率分割相结合的智能协同SWIPT传输方案(CoTP),推导了该传输方案的速率-能量(R-E)域,研究了接收端存在电路功耗情况下CoTP方案的速率-能量(R-E)均衡策略。同时,论文将所提的CoTP策略与动态功率分割(DPS)、开-关功率分割(OPS)、静态功率分割(SPS)与时隙切换策略(TS)的R-E域性能进行了比较,仿真分析了噪声以及接收端电路功耗对R-E域性能的影响。数值结果表明,与其他方案相比,若不考虑电路功耗情况,所提CoTP策略在每比特收集能量为0.6 mJ~2。4 mJ时具有较高的可达速率。若考虑电路功耗情况,所提CoTP策略在每比特收集能量为0 mJ~15 mJ时具有较高的可达速率,可以实现能量收集与信息传输的均衡。      

同信道干扰条件下的多天线放大转发中继中断概率分析

该文研究了基于波束形成技术的双跳多输入多输出(MIMO)放大转发(AF)中继系统的中断概率,该系统在发射端、中继端和接收端都配置了多根天线。假设每条链路的发射端采用最大比传输(MRT)技术,接收端采用最大合并比(MRC)技术,该文得出了中继端受到同信道干扰时的信干噪比(SINR),推导了基于固定增益中继方案的中断概率(OP)闭合表达式。计算机仿真结果不仅验证了性能分析的有效性,而且还分析了关键参数对系统性能的影响以及配置多天线带来的好处。     

Cooperative Impulse Radio Ultra-Wideband Communication Using Coherent and Non-Coherent Detectors: A Review

Ultra-wideband (UWB) is a booming technology in the field of wireless communication. This paper presents a brief idea related to the various coherent and non-coherent IR-UWB detectors. Due to the limitation in transmit power spectral density of UWB system, the major challenges faced by UWB system includes, achieving Quality of Service, system performance and coverage area. So, the combination of UWB system with cooperative communication will not only improve the system performance, but also help in expanding coverage area of signals. A brief review of the work done by various researchers in the field of cooperative impulse radio (IR) UWB communication is also presented in this paper. The working principle and performance analysis of the various coherent and non-coherent IR-UWB detectors using cooperative relay strategies are also discussed at large in this paper. The various fixed cooperative relay strategies used for cooperative UWB communication is Amplify and Forward, Decode and Forward and Detect and Forward. From the simulation results it can be inferred that, even though IR-UWB DTR receiver gives a much better BER performance than IR-UWB ED receiver using both cooperative and non-cooperative strategies, yet ED receiver is preferred because of its less complexity and low power consumption. Future prospects in the field of cooperative IR-UWB communication have also been discussed in this paper.     

Secrecy outage analysis in a hybrid cognitive relay network with energy harvesting

In this paper, we investigate the physical layer security of a hybrid cognitive relay network using an energy harvesting relay in presence of an eavesdropper. In the hybrid scheme, a secondary user (SU) as well as a cognitive relay works either in underlay or in overlay mode. In underlay, the transmit power of the SU as well as the relay is limited by the maximum acceptable interference at primary user (PU) receiver as required by an outage constraint of PU, a quality of service for PU. The secondary network consists of a decode and forward relay that harvests energy from radio frequency signal of secondary transmitter as well as PU transmitter to assist the SU in forwarding the information signal to the destination. A time switching relaying protocol is used at the relay. We evaluate the secrecy outage probability of secondary relay network assuming that channel state information of the interfering links from both the SU and relay transmitter to PU receiver is imperfect. Our results reveal the impact of imperfect channel state information, energy harvesting time, tolerable interference threshold, and PU outage constraint on the secrecy outage probability of SU.     

中继镜系统上行传输的数值模拟

利用激光大气传输四维程序,在H-V5/7湍流模型下建立了双望远镜中继镜系统上行传输模型。数值研究了地面发射功率对中继平台接收望远镜与地面发射望远镜之间的耦合效率以及中继平台接收功率和接收光场远场峰值功率密度的影响。结果表明:在文中的条件下,中继平台接收功率随着地面发射功率的增大而增大,同时,中继接收望远镜与地面发射望远镜之间的耦合效率和中继平台接收光场的光束质量随着地面发射功率的增大而下降;存在一临界热畸变参数NDc,当上行传输的热畸变参数超过这一值时,中继平台接收光场的远场峰值功率密度不再增加反而下降。对不同湍流效应下的中继镜系统上行传输的临界热畸变参数作了进一步研究,得到了临界热畸变参数随D/r0值变化的拟合关系式NDc=22.36e-0.26（D/r0）+36.87。     

多天线双向中继系统中的中继处理与资源分配策略

该文在多天线放大转发双向中继系统中,根据最小和均方误差(MSMSE)准则,以较小的复杂度得到了MSE最优的中继处理矩阵的闭合表达式。为综合利用空域和频域分集,探讨了OFDM双向中继系统的资源分配策略,提出了实现复杂度低的分层子载波配对策略和功率优化分配策略。仿真结果显示,所设计的中继处理策略在系统和速率和误码率性能上均明显优于其他双向中继策略,且性能随着中继天线数的增加而提升;结合功率分配的分层子载波配对策略能明显提升系统和速率,性能接近最优策略。