A simple transmit diversity system for fading channels using shaped sinusoidal functions

This paper proposes a transmit-diversity system using a pair of orthogonal pulses. The system uses a set of orthonormal-basic functions, which contains four shaped-sinusoidal pulses with the same frequency. The first two elements in the set are shaped sine and cosine pulses. The second two elements are the same sine and cosine pulses but they are shaped with the Hilbert transform of the shaping pulse of the first two elements. The modulator in the proposed system produces two modulated symbols for each data symbol. It uses the first two elements in the proposed set in modulating the first modulated symbol and the second two elements in modulating the second modulated symbol. The modulated symbols are transmitted though two antennas. The diversity order of the proposed system is twice the number of antennas in the receiver. In the proposed system, no space-time coding is used and the channel gains change every symbol period. This is different from the Multiple-Input-Multiple-Output (MIMO) system. The receiver of the proposed system consists of two matched filters for each receiving antenna. No special detectors or interference cancelation techniques are used because there is no interference between the outputs of the matched filters.     

A downlink beamforming assisted by locally positioned communication devices

Recently, multiple cell types with overlapping coverage have been deployed simultaneously to increase cellular network capacity. Cross‐tier interference is one of the key technical challenges in the use of this method. A simple and practical beamforming scheme assisted by locally positioned communication devices for the downlink of a multi‐cell wireless hierarchical cell structure system is proposed in this paper to maximize the capacity of the embedded small cell and simultaneously ensure minimal impact on the performance of existing macrocells. The locally positioned communication devices can be implemented with low complexity and at low cost and can continuously provide helpful and accurate information to base stations for the proper configuration of geographical cell coverage, allowing neighboring cells to cooperate effectively with each other. Simulation results verify that the proposed scheme can provide a significant gain over conventional systems not using the proposed algorithm. Copyright © 2013 John Wiley & Sons, Ltd.     

A robust adaptive weighted constant modulus algorithm for blind equalization of wireless communications systems under impulsive noise environment

A robust adaptive weighted constant modulus algorithm is proposed for blind equalization of wireless communication systems under impulsive noise environment. The influence of the impulsive noise is analyzed based on numerical analysis method. Then an adaptive weighted constant modulus algorithm is constructed to adaptively suppress impulsive noise. Theoretical analysis is provided to illustrate that the proposed algorithm has a robust equalization performance since the impulsive noise is adaptively suppressed. Moreover, the proposed algorithm has stable and quick convergence due to avoidance of large misadjuntment and adoption of large step size. Simulation results are presented to show the robust equalization performance and the fast convergence speed of the proposed algorithm under both impulsive noise and Gaussian noise environments.     

基于SystemView的奈奎斯特第一准则的验证与分析

本文阐述了奈奎斯特第一准则的基本原理,并使用SystemView软件对数字基带系统进行仿真设计。我们修改信道噪声和基带信号的码元传播速率,并观察比较接收波形和发送波形,直观看到噪声和码间干扰对数字基带系统的影响,同时验证了奈奎斯特第一准则。     

假目标散射特性对激光有源诱偏效果的影响

针对假目标散射特性对激光有源诱偏干扰效果的影响,提出了假目标激光散射特性的测量方法,实际测量了常见典型假目标的激光散射特性,得到了不同类型假目标对激光的散射规律。结果表明,利用假目标对激光制导武器进行有源诱偏干扰时,首先应选择散射系数较高的假目标,同时要依据假目标的散射特性确定干扰激光的照射部位,确保尽可能强的干扰激光信号进入导引头系统,形成有效诱偏干扰。     

邻频干扰对跳频系统中断概率的影响

在已知台站布置的跳频系统中,针对邻频干扰对系统中断概率的影响,分析了接收端信干噪比（SINR）的分布函数,得到了以信道参数、干扰台站数和可用频点数为变量的中断概率公式。理论计算和仿真结果表明,信道参数、干扰台站数是影响中断概率的主要因素,可用频点数与中断概率有类反比的关系。该结果为跳频系统的性能分析和台站布置提供了指导。     

联合多分组接收和模糊逻辑控制功率策略

针对无线网络节约能耗的要求,提出了一种联合多分组接收和模糊逻辑控制功率策略,采用串行干扰消除法,根据无线节点的传输功率等级,将功率等级划分为多分组接收能够正常解码的功率等级,并以任一无线节点到邻接节点的距离、邻接节点的个数和无线节点的剩余能耗为模糊逻辑控制的输入参数来控制各无线节点的功率选择。仿真结果表明,与现有的几种经典的基于功率控制的串行干扰消除算法方案相比,联合多分组接收和模糊逻辑控制功率策略的无线网络具有更大的有效吞吐量及更长的生存时间。     

基于MIMO的可见光通信中的信道均衡

针对基于多输入多输出(MIMO)的室内可见光通信(Visible-Light Communication,VLC)系统中存在的码间串扰(ISI)问题进行了分析,并提出了适用于MIMO可见光通信系统的信道均衡方案及实现方法.仿真实验结果表明,该方法可以有效降低MIMO可见光通信系统中的码间串扰的影响.     

参考信号耦合有用信号对干扰对消系统的影响及其抑制

分析了参考信号耦合有用信号时,实际自适应干扰对消系统的时域特性。分析表明,参考信号含有用信号导致系统时变,改变系统的最佳权值,使系统的干扰对消效果下降,并对有用信号的接收产生影响。根据实际共平台通信系统的收发耦合特性,从时域角度分析得到系统干扰对消比和有用对消比的计算表达式,并得到干扰对消比和有用对消比随相对时延相位变化的规律。提出一种时延匹配方法,通过匹配参考信号提取点至正交功分器输出与接收天线至合成信号注入点间的时延,可以有效抑制参考信号耦合有用信号导致干扰对消效果下降的问题。仿真结果表明,所提出的时延匹配方法能消除有用信号对干扰对消比的影响,还能提高干扰对消效果。