共查询到18条相似文献,搜索用时 93 毫秒
1.
2.
3.
串行级联Turbo码在Ka频段静止卫星通信系统中的应用仿真研究 总被引:1,自引:0,他引:1
文章在分析Ka频段静止卫星信道特点的基础上,建立了信道仿真模型并进行了基带仿真;研究了不同天气条件下静止卫星通信系统的误比特率性能;基于这一模型,通过仿真研究了串行级联Turbo码在静止卫星信道条件下的性能。仿真结果表明,除了中雨、雷雨等恶劣天气状况之外,在通常的天气条件下,串行级联Turbo码可以提供约10dB左右的编码增益,可有效改善系统性能。 相似文献
4.
5.
6.
7.
Turbo码的出现揭开了编码领域的新篇章。Turbo码中使用的交织器对码的性能有很大的影响。使用 Mat-lab工具 ,通过仿真比较了 Turbo码的几种交织器在不同交织深度时对 Turbo码性能的影响 ,说明 Turbo码交织器设计中的两个准则 ,并验证了这些准则的有效性。分析比较 SP交织器的性能 ,提出在交织器的设计中应将目标放在获得最好的性能上 相似文献
8.
9.
Turbo码是一种性能优异的纠错编码方式 ,已引起广大学者的高度重视。文中介绍了 Turbo码的编码方式和迭代译码原理 ,详细推导了 MAP算法。给出了目前用于 CCSDS标准中的 Turbo码结构。对 Turbo码和卷积码的异同点做了比较。最后给出了一些目前关于 Turbo码研究的热点问题。 相似文献
10.
在短波多径衰落信道的条件下,码间干扰、信道的严重衰落和快速变化是制约传输可靠性的重要因素。接收机的性能在很大程度上取决于信道估值与信道均衡的性能。但是在训练序列太短或者选用的均衡算法收敛速度太慢时,当训练过程结束,均衡器的权值无法收敛到最佳值。因此先用训练序列进行信道参数的辨识,通过解Wiener-Hopf方程直接将信道参数映射为均衡器的系数,然后复用训练序列用平方根卡尔曼算法对估计的抽头系数进行调整,并在跟踪过程中跟踪信道的变化。仿真结果表明,此算法比传统的自适应均衡算法,特别是在训练序列较短时,性能有明显提高。 相似文献
11.
针对机载情报侦察链中空地通信链路的特点,建立了统一的信道模型。模型包括大尺度衰落模型和基于三径信道模型的小尺度衰落模型。在给出了信道衰落模型的具体仿真方法后,分析了飞机飞行距离、工作频率及径向飞行速度等参数对信道特性产生的影响,为进行链路预算和解决多径干扰提供理论上的依据和参考。结果表明:不管信息传输速率多大,由于多径的影响在飞机飞行过程中频率选择性衰落都是不可避免的,但信息传输速率越高,衰落越严重;多普勒频移并不直接影响信道特性,但多径信道下的多普勒频移通过引起多普勒扩展而使信道具有了时变性。 相似文献
12.
13.
由于运算量大,以及对快衰落信道的无能为力,自适应均衡器的使用受到了很大的限制。将高斯-塞得尔迭代用于信道均衡,提出了一种基于信道估值的信道均衡算法,主要分析了小数抽头决策反馈均衡器的性能,并与整数抽头均衡器作了比较。 相似文献
14.
多径信道下OFDM信号和单载波信号的盲识别 总被引:1,自引:0,他引:1
针对非协作通信条件下OFDM(正交频分复用)信号和单载波调制信号的类间识别问题,提出一种在多径信道下基于信号循环自相关的调制识别算法。该算法不需要信号和噪声的先验知识,可以直接对中频信号进行处理,具有较强的实用性。通过对信号循环自相关函数进行分析,仅需进行时域的延时自相关运算和特定延时下的循环自相关运算,就可以从频域提取特征值来实现OFDM信号和单载波信号的盲识别。在估计OFDM信号周期时,提出一种基于极大值抽取的延时估计算法,能在多径衰落信道中不需要先验信息的情况下完成估计。仿真表明,本文提出算法的识别性能优于传统的四阶累积量算法。 相似文献
15.
16.
17.
在卫星多径衰落信道环境中传输正交频分复用信号时,工程上可以考虑采用以插值运算为核心的信道估计方法对接收信号进行信道估计。文章首先给出并研究了线性插值、三次样条插值和拉格朗日函数插值这三种插值估计算法的基本原理,然后对各种算法的计算复杂度、插值估计的均方误差以及系统的误比特率这三项性能指标进行了对比分析,最后通过综合评估总结出了"在慢多径衰落信道环境下宜采用线性插值估计算法"和"在快多径衰落信道环境下宜采用三次样条插值估计算法或拉格朗日函数插值估计算法"的结论。 相似文献
18.
Multipath fading analysis of telemetry signals power fluctuations from Universitetsky microsatellite
The article deals with the results of the fading fluctuations analysis for telemetry signals in the 2 m and 70 cm bands from the first Moscow State University microsatellite better known as “Universitetsky”. Radio telemetry signals were received from the microsatellite for around 2 years, collecting and recording the power signal data of almost 7500 satellite overpasses. The received signals from about 2300 satellite overpasses had a very low signal to noise ratio (SNR) that caused high transmission losses. The rest of the signals had a SNR high enough to complete the transmission without losses. The main objective of this paper was to find the fading fluctuations caused both by diffusion and by the presence of Gaussian and non Gaussian noise in telemetry signal power data. The purpose was both to characterize the communication channel as well as to elaborate solutions both to improve the communication quality as well as to identify no homogeneous zones in the ionosphere environment. The signal power analysis was based in the observation of statistical characteristics from different power signal components, in particular the components influenced by diffusion and non Gaussian noise. The employed methodology follows the next steps: removing the power signal envelope; taking away the Gaussian noise; obtaining the statistical characteristics from non Gaussian noise, Gaussian noise and envelope; finally identifying the LOS and NLOS signal fading components. For this purpose, the wavelet technique was used to perform the signal decomposition. In particular, the discrete wavelet transform DWT was utilized to carry out the signal de-noising. Then, the results were statistically treated in order to obtain a diffusion index for Rician fading, which are associated with fading in atmosphere and ionosphere layers. In this way the communications channel among satellite and ground station was characterized and a BER parameter was obtained for every satellite overpass, which means an outstanding result when considering that just few papers describe such results for satellite systems. The obtained results are valid not only for satellite communications systems but also for wireless communications systems. These results are the basis for future communications system design, which in our case pursues to reduce the BER parameter in the satellite link. The referred system will employ adaptive error coding schemes as well as channel analyzer algorithms based in the theory exposed in this paper. 相似文献