New transmission scheme to enhance throughput of DF relay network using rate and power adaptation

This paper presents a new transmission scheme for a decode and forward (DF) relay network using continuous power adaptation while independent average power constraints are provisioned for each node. To have analytical insight, the achievable throughputs are analysed using continuous adaptation of the rates and the powers. As shown by numerical evaluations, a considerable outperformance is seen by continuous power adaptation compared to the case where constant powers are utilised. Also for practical systems, a new throughput maximised transmission scheme is developed using discrete rate adaptation (adaptive modulation and coding) and continuous transmission power adaptation. First a 2-hop relay network is considered and then the scheme is extended for an N-hop network. Numerical evaluations show the efficiency of the designed schemes.     

无线电测向设备测向误差与数据处理方法研究

通过对某型测向设备的测向精度试验获取的试验数据的分析处理发现，现行的标准和规范中采用的测向误差计算方法没有能够正确区分出设备的能力和试验环境的影响。不能完全客观公正地评价测向设备的真实性能。为了获得合理的测向结果，建议严格按照ITU的有关标准选择测向场地。并选择合适的误差计算方法。     

中远红外双波段激光器增益介质匹配

对中远红外双波段激光器中DF和CO2两种增益介质的匹配进行了研究。根据对DF和CO2两种增益介质分布的理论分析,发现DF相比于CO2介质增益峰值位置更靠前,激活区长度更短,据此设计加工了一台双波段激光器,使CO2气体注入孔位置可调,通过D2和CO2注入孔位置的差别来实现两种介质增益峰值位置的匹配。实验证明了这种设计是有效的,并确定了激光器共同光轴的最佳位置位于D2气注入孔下游3 mm,CO2注入孔下游33 mm处,此处双波段激光的输出功率均接近最大值。     

HF／DF化学激光器的研究进展

HF／DF激光器作为光电对抗设备的中波红外备选光源受到研究者的普遍关注。本文对HF／DF激光器几十年的发展进行了回顾和分析,并在此基础上对其未来的发展方向进行了预测和探讨。     

Dense subspaces of quasinormable spaces

Dense linear subspaces of quasinormable Fréchet spaces need not be quasinormable, as an example due to J. Bonet and S. Dierolf proved. A characterization of the quasinormability of dense linear subspaces of quasinormable locally convex spaces and several consequences are given. Moreover, an example of a dense linear subspace of a countable direct sum of Banach spaces, which is not quasinormable, is provided. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

单通道接收机实施空间谱估计测向

本文是应用空间谱估计技术测向的一种新方法。基于用权微扰算法得到的协方差矩阵，提出了用单通道接收机实施空间谱估计测向。从原理上讲，任何特征结构算法都适用。针对空间骨算法进行了计算机模拟，结果证明方法是有效的。并且这一方法有着重要的现实意义。     

小型电激励连续波HF/DF化学激光器研究进展

小型电激励连续波HF/DF化学激光器具有广泛的用途和重要基础研究价值,本文介绍了四种放电类型的小型电激励连续波HF/DF化学激光器的研究工作,并对各类型激光器的优缺点进行了讨论。     

三维告警测角系统的天线布局研究

相对于常规的告警比幅测向系统,三维告警不仅要测量目标的方位角,还需要测量目标的俯仰角,其比幅天线布局不同。通过对比计算三维告警和常规两维告警覆盖的立体角,从理论上分析了两种条件下比幅测向天线数量的区别。并在此基础上,提出了一种三维告警测角系统天线的布局方式,并说明了这种布局方式的优点。     

基于机载平台的干涉仪测向技术研究

围绕工程实际中干涉仪测向技术面临着布阵平台空间有限、不能同时对多个信号分辨的问题进行研究,提出相应的解决办法.首先根据机载平台特点,给出了5元均匀椭圆阵列模型,分析了椭圆阵列孔径与波长之比对入射角度的估计性能影响,得出了在一定孔径范围内增大阵列孔径能提高测向精度的结论;接着采用四阶累积量MUSIC算法引入虚拟阵元来解决受限平台上增大孔径的问题,仿真验证了此算法在干涉仪椭圆阵列模型中的有效性.     

More tractable average error rate expression for the Nth best relay selection scheme of DF relaying over Rayleigh fading channels

In this paper, we derive another exact average error rate expression for the Nth best decode‐and‐forward relay systems over Rayleigh fading channels. On the basis of error‐events at relay nodes, the Nth best relay's selection probability is expressed as a more tractable form in which the number of summations and the length of each summation are specified. Then, exact average error performance metrics are obtained as two well‐known forms. The first is expressed with a moment generating function, and the other is presented as a closed form. Simulation results are finally presented to validate that the derived analytical expression can be a general frame work covering all Rayleigh fading channel conditions. Copyright © 2012 John Wiley & Sons, Ltd.