Capacity of FH wireless multi-hop networks

In this article, the capacity of wireless multi-hop networks with the frequency hopping (FH) technique is derived. Different from the previous work based on non- spread spectrum (SS) system, this study is based on frequency hopping spread spectrum (FHSS) and the retransmission mechanism. The analysis results show that the normalized transport capacity decreases as 1/(Mλ) , when the total available frequency band is divided into M sub-bands for frequency hopping and the nodes are randomly distributed in space according to a Poisson point process with intensity λ . In this work, the best transmission range per hop to get the maximum capacity is also derived. Besides, the results summarize how the capacity of FH wireless multihop networks is affected by the outage probability, target signal to interference plus noise ratio (SINR) and other system parameters.     

强方向性干扰下跳波束通信方式的性能分析

通信波束的方向上出现的强方向性干扰将严重地影响无线通信的质量,本文针对这一问题,提出了一种新的跳波束的通信方式。对其平均信干噪声比性能的分析结果表明,这种新的跳波束通信方式能够有效地对抗方向性干扰。     

Coherent interference suppression with complementally transformedadaptive beamformer

This paper proposes a beamforming scheme for suppressing coherent interference with an array of arbitrary geometry. The scheme first uses estimates of the source directions to construct a transformation, which removes the desired signal while retaining the coherent interference. Optimum beamforming is then performed on the transformed data containing only interference and noise to produce the maximum output signal-to-interference-plus-noise ratio (SINR). Analysis and numerical results demonstrate that the proposed complementally transformed beamformer significantly outperforms the conventional multiply constrained minimum variance (MCMV) beamformers     

时分双工蜂窝系统的智能天线研究和性能评估

智能天线是移动多媒体通信亟待解决的关键技术,本文研究了一种适用于时分双工蜂窝系统,基于非线性判决反馈空间均衡器和递归最小平方算法的智能天线。提出了双向链路信号对干扰加噪声功率比的算法以及阵列波束方向增益和信干比累积分布函数两种性能评估方法。仿真结果表明：该智能可以抵消同波道干扰,改善信干比,减小频率复用系数。     

A two-sensor array blind beamformer for direct sequence spreadspectrum communications

We present an efficient blind beamformer dedicated to the problem of interference mitigation in direct sequence spread spectrum (DSSS) communication systems using a two-sensor array. A closed-form solution for the blind identification of the communication channel is derived by exploiting the temporal properties of the desired signal and the interference. The optimal beamformer is derived from the maximization of the signal-to-interference and noise ratio (SINR) at the output of the receiver in terms of the blindly estimated channel coefficients. Three structures of the DSSS receiver are presented. One structure consists of the blind beamformer followed by the spread spectrum demodulator. The other two structures consist of the spread spectrum demodulator followed by the blind beamformer. The performance of these structures is discussed in terms of the achieved SINR and the computational cost. Simulation results are provided to illustrate the effectiveness of the proposed blind beamformers in interference excision     

基于稀疏约束和SRV约束的宽带自适应波束形成

针对传统的宽带MVDR自适应波束形成中,抑制干扰的同时会抬高旁瓣电平,且过多的线性约束会导致波束输出的SINR性能下降的问题,提出了一种基于SRV约束和稀疏约束的低旁瓣、高增益宽带自适应波束形成方法.该方法在窄带MVDR自适应波束形成基础上,通过增加波束图稀疏约束来降低波束的旁瓣电平,同时利用空间响应偏差(SRV)约束将窄带算法推广到宽带MVDR 自适应波束形成中,极大地降低了算法的复杂度,改善了波束输出的SINR 性能.与传统方法相比,该方法在降低宽带波束的旁瓣电平的同时,还具有良好的干扰抑制效果.数值仿真实验验证了该方法的有效性.     

Joint beamforming and power control in downlink multiuser multiple‐input multiple‐output systems

In this paper, we study joint beamforming and power control for downlink multiple‐input multiple‐output systems with multiple users and target values for signal‐to‐interference plus noise ratios (SINRs). We formulate this as a constrained optimization problem of minimizing total interference subject to constraints on the beamforming vector norms, target SINRs, and total transmit power. Necessary and sufficient conditions satisfied by the optimal beamformer and power allocation are presented, and a new algorithm for joint beamforming and power control is proposed. This adapts the beamforming vectors and transmit powers incrementally, and it stops when the specified SINR targets are achieved with minimum powers. The proposed algorithm is illustrated with numerical results obtained from simulations, which study its convergence and compare it with other similar algorithms. Copyright © 2013 John Wiley & Sons, Ltd.     

基于谱分析的稳健自适应波束形成算法

针对在导向矢量存在误差情况下,自适应波束形成算法性能下降问题,提出一种基于谱分析的稳健自适应波束形成(SA-RAB)算法。算法利用空域与频域的对称性,根据真实导向矢量与理想导向矢量之间的误差,运用谱分析(SA)技术确定波束主瓣宽度,最后利用二阶锥规划(SOCP)技术在主瓣宽度内形成平顶响应,并在副瓣区域内进行干扰抑制。仿真结果表明:该算法可有效地抑制干扰,并输出理想的信号干扰噪声比(SINR),且提高了波束形成针对导向矢量误差的稳健性,验证了算法的有效性和优越性。     

Minimum-noise-variance beamformer with an electromagnetic vectorsensor

We study the performance of the minimum-noise-variance beamformer employing a single electromagnetic (EM) vector sensor that is capable of measuring the complete electric and magnetic fields induced by EM signals at one point. Two types of signals are considered: one carries a single message, and the other carries two independent messages simultaneously. The state of polarization of the interference under consideration ranges from completely polarized to unpolarized. We first obtain explicit expressions for the signal to interference-plus-noise ratio (SINR) in terms of the parameters of the signal, interference, and noise. Then, we discuss some physical implications associated with the SINR expressions. These expressions provide a basis for effective interference suppression as well as generation of dual-message signals of which the two message signals have minimum interference effect on one another. We also analyze the characteristics of the main-lobe and side-lobe of the beampattern of an EM vector sensor and compare them with other types of sensor arrays     

Beamforming for inter‐relay interference reduction in MIMO‐aided two‐path successive relaying

To effectively reduce the inter‐relay interference (IRI) in two‐path successive relaying, two beamforming schemes are proposed in this paper, utilizing multiple‐antenna relay nodes. Specifically, the two cooperation nodes perform receive combining of the source signal and transmit beamforming of the relayed signal alternately in the successive relaying process. As a result, the IRI between them can be effectively suppressed, thanks to the additional degree of freedom provided by the multiple‐input multiple‐output inter‐relay channel. In the first beamforming scheme, the source‐to‐destination signal‐to‐interference‐plus‐noise ratios (SINR) of separate paths are maximized with approximation, leading to a minimum variance distortionless response beamformer under the high SINR condition. To further improve the system performance, noting that the received SINRs of the two paths have impact on each other due to the mutual coupling of the beamformers, the sum of mean squared errors from these two transmission paths is minimized in the second scheme. Based on this performance criterion, a suboptimal beamformer design is developed numerically through cyclic minimization of the sum of mean squared error cost function. Simulation results demonstrate the superiority of both proposed beamforming schemes in terms of symbol error rate and the achievable system rate, in particular, at high IRI levels. Copyright © 2016 John Wiley & Sons, Ltd.     

跳频信号盲检测的时频语义对消方法

复杂电磁环境下精准检测跳频信号是实施跳频信号侦查的先决条件。针对复杂干扰下跳频信号难以检测的问题,本文提出一种名为时频语义对消的方法。该方法设计了一种具有自注意力和图注意力机制的暹罗嵌套UNet,并根据该网络提取包含跳频信号、干扰信号和噪声的时频图语义信息。将得到的结果与不包含跳频信号时频图的语义信息相消就可以得到仅包含跳频信号的时频图,实现对跳频信号的检测。仿真结果表明所提方法可以在复杂干扰下实现对跳频信号的参数估计与盲检测,在信噪比高于-5 dB和信干比高于0 dB时,虚警概率与漏警概率低于1‰。在信号时频范围检测中,对比实验表明语义对消检测方法比语义分割检测方法交并比分数提升0.31,消融实验表明注意力模块对交并比分数提升为0.022。同时分析了所提网络的复杂度,结果表明该方案具有较小的参数量以及较快的处理速度,可以运用于跳频信号的实际检测当中。      

基于累积量的盲自适应波束形成技术

本文研究了在阵列信号处理中使用累积量的问题,以及在相干多径环境中基于累积量的盲自适应波束形成技术。该技术能在阵列几何结构和阵列流形未知的条件下,自适应调整权系数使阵列输出的信号干扰加噪声比最大。     

Analysis of the error performance of adaptive array antennas for CDMA with noncoherent M-ary orthogonal modulation in Nakagami fading

This letter presents an analytical model for evaluating the bit error rate (BER) of a direct sequence code division multiple access (DS-CDMA) system, with M-ary orthogonal modulation and noncoherent detection, employing an array antenna operating in a Nakagami fading environment. An expression of the signal to interference plus noise ratio (SINR) at the output of the receiver is derived, which allows the BER to be evaluated using a closed form expression. The analytical model is validated by comparing the obtained results with simulation results.     

Performance analysis of the minimum variance beamformer

We present an analysis of the signal-to-interference-plus-noise ratio (SINR) at the output of the minimum variance beamformer. The analysis is based on the assumption that the signals and noise are Gaussian and that the number of samples is large compared to the array size, and it yields an explicit expression for the SINR in terms of the different parameters affecting the performance, including signal-to-noise ratio (SNR), interference-to-noise ratio (INR), signal-to-interference ratio (SIR), angular separation between the desired signal and the interference, array size and shape, correlation between the desired signal and the interference, and finite sample size     

Performance of power control in inter-cell interference coordination for frequency reuse

To mitigate inter-cell interference in 3G evolution systems,a novel inter-cell interference coordination scheme called soft fractional frequency reuse is proposed in this article,which enables to improve the data rate in cell-edge.On this basis,an inter-cell power control is presented for the inter-cell interference coordination,and the inter-cell balanced signal to interference plus noise ratio(SINR) among users is established for power allocation,which enables mitigation of inter-cell interference.Especia...     

Performance evaluation of Wi‐Fi and WiMAX over OFDM physical layer

Orthogonal frequency division multiplexing (OFDM) is an alternative technology that is constrained to keep up with the increasingly high data transmission rate due to its robustness against selective frequency fading and its resistance to intersymbol interference (ISI). This paper aims to study and optimize its performance, namely, its probability of communication failure and signal‐to‐interference‐plus‐noise ratio (SINR) metrics. The mathematical tool used to perform OFDM evaluation and analysis is the Fourier transform and its properties. The obtained results of those equations led to the demonstration of the probability of communication outage and to notice that the cutoff time occurs after the 10th iteration for values of λ less than or equal to 1. It could also be checked that this period is small if λ exceeds 1 by considering the sensitivity factor. Moreover, for the obtained results, in terms of bit error rate (BER) and SINR, the influence of the modulation on the error vector magnitude (EVM) shows the sensitivity factor Ω presents a key role in the transmission chain.     

Performance improvement of fixed wireless access networks by conjunction of dual polarization and time domain radio resource allocation technique

This paper considers the impact of dual polarization adoption on the performance for a fixed wireless access (FWA) network. The major limiting factor of the performance in these systems is co‐channel interference (CCI) originating from intracell and intercell concurrent transmissions. The proposed framework combines an appropriate time domain radio resource allocation technique with a dual polarization pattern to mitigate CCI and enhance the obtained signal to interference plus noise ratio (SINR). Simulation results present the performance of the proposed framework against various terrain categories and sector antenna characteristics. Copyright © 2010 John Wiley & Sons, Ltd.     

基于嵌套阵列的稀疏表示稳健波束形成方法

针对波束形成中目标方位失配以及噪声加干扰的协方差矩阵非精确重构造成的波束形成方法性能下降的问题,提出一种基于嵌套阵列的稀疏表示稳健波束形成方法。在该方法中,计算嵌套阵的采样协方差矩阵,通过差合作阵处理得到一孔径扩展的虚拟均匀线列阵;基于稀疏表示的方法来估计目标以及干扰的准确方位信息;进一步利用得到的方位信息构造导向矢量,通过最小二乘方法计算干扰信号的精确功率值;最后重构干扰加噪声协方差矩阵,通过波束形成实现干扰抑制。数值仿真表明,所提方法有效提升了干扰加噪声协方差矩阵重构精确度,在不同信噪比和快拍数条件下,输出信噪比都能逼近最优信干噪比,验证了该算法的有效性。     

射频干扰环境下OFDM系统的盲信号干扰噪声比估计

基于OFDM信号的循环平稳特性,提出一种在射频干扰环境下OFDM系统的盲信号干扰噪声比估计方法。通过分析发送信号,射频干扰信号以及高斯白噪声的周期自相关函数能量分布规律,选取合适的延时变量和循环频率在功率谱域能有效分离信号功率和干扰加噪声功率分量,从而估计出信号干扰噪声比值。计算机仿真结果表明,和经典的二阶四阶矩(M2M4, second-order and fourth-order moments)盲信号干扰噪声比估计方法相比,新方法不仅能够有效估计射频干扰环境下OFDM系统的信号干扰噪声比值,而且无论是估计性能还是复杂度都优于M2M4方法;同时在快衰落Rayleigh信道下,新方法也能有效的估计出信号干扰噪声比值。进一步,所提方法具有对射频干扰信号密度不敏感的优点。     

Design and analysis of synchronous dynamic frequency hopping code division multiple access communication system

An optical dynamic frequency hopping code division multiple access communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. Two-dimensional code, named functional code, is also proposed based of shifted sine function. The function defines the dynamic coding pattern of the central wavelength of the transmitted narrowband optical signal. Thus, the system will allow for an easy reconfiguration of the transmitter without the need for sophisticated encoder. At the receiver, a synchronized TOF with the same function is used as a decoder. The system is modeled and analyzed taking into account the multiple access interference, phase induced intensity noise, and thermal noise. The performance of this system is shown to be better compared with a fast frequency hopping system and a spectral amplitude coding system that uses either a Hadamard code, a modified quadratic congruence code (MQC), or a modified frequency hopping code (MFH).