上行链路功率控制算法在Ka波段卫星通信系统中的研究

为了减少降雨对Ka波段（30/20GHz）卫星通信系统信号传输质量造成的影响,本文提出了一种改进的上行链路功率控制的方法,即对某个控制周期选取修正参数来提高上行链路降雨衰减的预测精度。仿真结果表明：该方法具有较好的补偿效果和精度。     

Ka波段雨衰减时间序列的合成及性能仿真

在Ka波段(30/20GHz)卫星通信系统传输中,降雨衰减是导致信号衰落的重要原因之一.为了通过功率控制算法来补偿动态雨衰减,用ITU-R降雨衰减预测模式,通过最小二乘曲线拟合方法详细推导我国北京地区雨衰减统计分布的参数,获得北京地区的动态雨衰减时间序列;用下行链路雨衰减预测上行链路雨衰减的方法,为上行链路功率控制算法奠定了基础;采用QPSK调制,分别考虑AWGN信道和莱斯多径衰落信道,将有小雨、中雨、大雨这三种降雨与没有降雨情况进行性能对比,仿真结果表明雨量越大对系统的影响越严重.     

Ka频段卫星通信地空链路的云雾衰减

在卫星通信系统的设计中,设计人员往往更关心的是降雨对电波传播造成的降雨衰减而忽略了在一般情况下云雾对卫星通信地空链路微波传播的影响。但是当系统的链路余度较小、天线仰角较低的情况下,应考虑云雾造成的衰减。本文论述了Ka频段卫星通信链路云雾衰减的计算方法,给出了计算结果,可供从事类似工作的相关人员参考。     

认知星地混合网络中基于干扰约束的最优功率控制方法

在认知星地混合网络中,当卫星用户作为次级用户时,为了不影响地面主用户系统的正常工作,在上行链路中要对卫星用户进行必要的功率控制。针对衰落信道场景,选择最大化卫星用户的遍历容量（EC）作为优化的目标函数,分别提出了基于峰值干扰功率约束（PIC）和平均干扰功率约束（AIC）的功率控制方法,并给出了最优发射功率的闭合表达式。仿真结果表明,卫星信道条件越好、地面干扰链路衰减越大,卫星用户的性能越好;除此之外,基于AIC的功率控制方法要优于基于PIC的功率控制方法。     

Ka波段卫星通信系统降雨衰减的计算

研究基于ITU-R的降雨衰减预测方法,并根据此算法以62°E,Ka波段30GHz的卫星通信系统为例,对我国65个典型站点的降雨衰减值进行了计算,为降雨衰减的进一步研究提供了数据支持。     

APPLEⅡ在实时处理微波辐射降雨衰减数据中的应用

用来研究大气、天文、电波传播和地貌特性的25毫米波段的微波辐射信号,降雨时受到衰减。为了改变手工处理微波辐射降雨衰减数据以及相应的降雨率数据费时、费事和查阅历史资料极为不便的落后状况,并提高处理精度,我们利用APPLE Ⅱ微机实现了对12GHz微波辐射降雨衰减数据以及相应的降雨率数据的自动采集、处理、存储和打印的实时控制。     

基于数字线性化技术的高性能光载无线链路

针对光载无线(Radio over fiber, ROF)链路中的固有非线性,研究了多种数字线性化技术,来提高链路性能。下行链路针对多频段多制式场景,提出采用多维数字预失真技术,最大输入射频功率增加了3 dB,进而提高了下行链路的射频功率传送效率。同时,提出了多维预失真在2倍过采样率,考虑5阶非线性,无记忆时有最佳的链路性能改善。上行链路采用基于输出截断点获取的数字后补偿技术,仅需确定系统三阶截断点(Output third-order intercept point,OIP3)即可完成非线性补偿函数的确定与失真的补偿,无杂散动态范围(Spurious free dynamic range,SFDR)可提高到128.3 dB·Hz2/3;上行链路针对多频段多 制式架构采用盲估计数字后补偿技术,动态范围提高了3 dB。     

26GHz LMDS在雨区中传输的分析

分析了降雨对26GHzLMDS产生的降雨衰耗和去极化,并给出了有关的公式.介绍了一个26GHzLMDS在新加坡降雨时进行测量的方法和结果.研究指出,降雨对26 GHz LMDS的信号传输有很大的影响,随着降雨率的增加,降雨衰耗的增加接近线性,差分衰减和差分相移的增加变得更加显著.当降雨率接近90mm/h时,会出现3dB的差分衰减和45°的差分相移.     

卫星通信系统的降雨衰方法研究

研究降雨天保证卫星通信高质量问题。卫星通信极易受云、雪、雾、雨等天气的影响,尤其是在下雨天气中卫星通信信号的衰落程度最大。传统的分集接收技术不能有效去除雨衰对通信信号的影响,造成卫星通信质量不高的问题。为了克服上述难题,提出了根据上行功率降雨衰的方法。通过检测卫星信号的强度,计算卫星通信链路上的雨衰大小,并根据雨衰值动态调整地面通信站中功率放大器的发射功率,达到对雨衰进行最大补偿,有效减小了雨衰对通信质量的影响。实验表明,改进方法能够有效避免降雨对通信信号的影响,最大限度地对雨衰进行了补偿,提高了卫星通信的质量,取得了满意的结果。     

基于非合作博弈的变电站无线网络资源研究

无线资源管理对实现资源的有效利用起着至关重要的作用.针对变电站中无线网络资源分配问题,提出了基于非合作博弈的变电站无线网络资源的优化管理算法,解决了全双工系统的无线电资源分配问题.将下行链路与上行链路的联合速率最大化问题建模成为上下行链路信道之间的非合作博弈,提出了基于非合作博弈的迭代算法.该算法有效的实现最佳上行链路与下行链路的资源分配,直到达到纳什均衡.仿真结果表明,该算法实现了快速收敛,与同等资源分配方法相比,可以显著提高全双工的性能.     

Technical note The effect of rate of decay of rain path profile on microwave communication

The attenuation of radio waves due to rain can be predicted with a good degree of accuracy, provided the rain rate characteristics over the entire path of propagation are known. The attenuation due to rain is usually deduced on the basis of point rain rate, which can lead to inaccuracy in the estimation of attenuation. We use the concept of rate of decay of rain path profile to estimate the attenuation due to rain. The attenuation has been deduced at 11GHz and 13.4 GHz for 56 elevation angle by using the theory of decay rate of rain path profile, its controlling factor, gamma, and rain rate distribution over Delhi, a tropical station in India. The theoretically-estimated attenuation is compared with observed values, as well as with values obtained using the International Radio Consultative Committee (CCIR) method. The CCIR model is found to overestimate the attenuation.     

Ka频段维纳雨衰预测模型与补偿系统

为了降低Ka频段雨衰的影响,基于维纳预测思想建立了一种维纳雨衰预测模型,该模型通过预测某一频率点的雨衰值来控制多进制正交幅度调制（MQAM）的阶数M和发射功率,从而降低雨衰的影响。通过和DAH雨衰预测模型的仿真比较,结果表明,当频率大于[21 GHz]时,维纳雨衰控制模型能比较精确地预测各个频率点的雨衰值,其最大误差小于0.2 dB。相比于DAH预测模型,维纳雨衰控制模型大大简化了计算量,提高了计算效率。     

Ka频段抗雨衰自适应功率控制算法

为了降低雨衰对Ka频段卫星通信的影响,提出了一种简单的自适应功率控制算法.该算法可根据低频段或低降雨率的雨衰数据预测高频段或高降雨率的雨衰,并且可通过算法的不同参数的选取,提高预测精度.仿真结果表明,该算法具有较好的精度和补偿效果.     

Cover The identification of small patterns on the surface of the sea

The rainrate distributions obtained from rapid response rain gauge measurements over five different locations in India are presented. On the basis of simultaneous observations of rainrate measured by rain gauges having integration times of 10 seconds and 15 minutes, a power law has been established. Rain attenuation characteristics at 11GHz were analysed and some interesting results are presented, which are also compared with International Radio Consultative Committee and other models. Attenuations due to water vapour are deduced for a frequency range of 1-350GHz at elevation angles 3 and 10 . The attenuation due to water vapour at a lower elevation angle is found to increase as the tropospheric effects become dominant. It can also be seen that the antenna temperature attains a peak value of about 160K in the monsoon months and a minimum of about 80 K during the winter. The monthly variation of antenna temperature reveals a similar variation for the attenuation and water vapour content.     

星地测控链路中的功率控制策略研究

对于卫星来说,能源是极其重要的资源,为有效节约星上能源、延长卫星寿命,研究了星地测控链路的功率控制策略;首先,分析了造成星地测控链路信号衰减的因素,在此基础上,建立了卫星下行链路信噪比计算模型,然后,在保证地面设备能够正确解调星上遥测数据的前提下,在星地测控链路中,提出了基于信噪比平衡准则的闭环功率控制策略,最后,利用构建的计算模型,仿真分析了所提功率控制策略对卫星功耗的影响和对雨衰的抑制作用;研究结果表明,所提的功率控制策略能大幅降低卫星功耗,且复杂度低,具有工程实践性,同时,对雨衰有较强的抑制作用,能有效提高设备跟踪时长,保证卫星下行信号接收。     

基于循环神经网络的宽带CDMA系统的功率控制

在CDMA系统中,远近效应是一个重要的技术难题,克服该难题的有效措施是系统进行功率控制.该文根据Hopfield循环神经网络的思想,把功控问题转化为离散的Hopfield神经网络,由此给出了一种新的功率控制算法,它能控制移动用户发射功率的平衡,且有较强的Robustness性质,易于工程实现.     

Estimating tropical rain attenuation on the Earth-satellite path using radar data

Radar-return echoes, known as ‘reflectivity’, are exploited in the course of estimating rain attenuation along a slant path. Relevant radar gates or ‘range bins’ are identified to correlate a specific satellite path. The reflectivity value of each range bin is converted to rainfall rate using established radar reflectivity values – rainfall rates, (Z–R relation). Specific attenuation is then derived for all associated range bins. The attenuation for each bin is the product of specific attenuation and its effective path length. The summation of attenuation endured by all range bins is inferred as the attenuation along the slant path. In this study, an X-band slant path rain attenuation was estimated using 2.85 GHz (S-band) Terminal Doppler Weather Radar (TDWR) data. A technique to estimate rain attenuation by exploitation of radar information is elaborated in this article. Comparisons between the radar-derived attenuation estimations and actual satellite signal measurements are also presented. The findings were verified by comparing the generated values to the directly measured rain attenuation from the Razak satellite (RazakSAT). Radar reflectivity data were obtained from Kuala Lumpur International Airport (KLIA) radar station operated by the Malaysian Meteorology Department (MMD). Preliminary findings using the most recent Z–R relation (i.e. the generated radar-derived rain attenuation estimations) appear to show lower values than the actual measurements.     

Rain generated ring-waves: Measurements and modelling for remote sensing

We present an analysis of ring-wave and scatterometer data from a water surface that was agitated by simulated rain. Water droplets of 2.8mm diameter impacted the water surface at almost terminal velocity, and the rain rates cover a wide range of conditions (5 to 200mm hr^?1). Both the ring-wave energy and backscattered power from the GHz scatterometer increase as R increases, but the growth rates slacken at higher rain intensities. Ring-wave frequency spectra and wavenumber spectra are well represented by log-Gaussian spectral models. The results can be used to guide development of microwave scattering models.