共查询到19条相似文献,搜索用时 62 毫秒
1.
讨论了跳频码的构造与性能,着重介绍了Costas序列的结构,用Costas序列设计跳频码能获得理想的自模糊和较好的互模糊性能.建立了跳频扩频信号的数学模型,给出了子脉冲正交的条件.论述了Costas序列的自(互)相关特性,给出了置换序列互相关函数的实用性质及模糊函数的求取算法,并进行了性能仿真,研究了Costas序列互模糊函数的特性,阐述了多用户系统中减小用户间相互干扰的方法. 相似文献
2.
部分传输序列(PTS)方法需遍历所有的可选相位因子,这样的计算量随分割子序列数按指数增长。本文在对循环移位PTS方法 (PTS/CSS) 和次优PTS方法 (sub-OPTS) 进行研究的基础上,提出了一种减少计算复杂度的次优化时域循环移位序列方法(sub-OPTS/CSS)。该方法用快速傅立叶变换(FFT)的时域循环移位特性增加更多备选信号;且仅对变换后的部分备选信号进行相位优化。同时,将其与已有的一些方法的备选信号、冗余比特数、运算量进行了分析和比较。理论分析和仿真结果表明,当使用相同的分割子序列数和相位旋转因子时,sub-OPTS/CSS方法降低PAPR的性能稍次于PTS/CSS方法,但搜索最佳相位时的计算量减少了一半;sub-OPTS/CSS方法降低PAPR的性能要优于sub-OPTS方法。 相似文献
3.
基于正交多相序列的OFDM信道估计算法 总被引:1,自引:0,他引:1
提出了一种基于正交多相序列的OFDM信道估计算法。该算法采用相关性能良好的正交多相序列作为发送信号的循环前缀,在接收端,提取循环前缀,进行相关计算,最终得到系统频域响应的估计值。通过仿真,验证了在多径衰落信道中,提出的算法比频域梳状导频插入的时域滤波算法及采用小m序列作为循环前缀的信道估计算法具有更高的信道估计精度。 相似文献
4.
针对突发分组模式的OFDM传输系统,提出了一种基于加权CAZAC序列的OFDM系统同步方案,在时域实现了符号定时和频偏估计。仿真结果显示定时精确稳定,频偏估计范围大、均方差小,在低信噪比和量化后表现优异,减小了硬件设计的复杂性。 相似文献
5.
6.
7.
给出了OFDM在无线个人域网、局域网、城域网和广域网中的典型应用,并对其系统参数的取值方法进行了比较。 相似文献
8.
9.
阐述了Costas序列的代数结构及其特点,分析了常用雷达信号,如线性调频脉冲信号、非线性调频脉冲信号等的模糊函数,文中指出当雷达信号使用Costas序列的构成方法形成跳频扩频的信号时,将获得理想的模糊函数性能,即同时获得极好的距离分辨率和速度分辨率。文中建立了多目标散射、多径衰落和加性高斯白噪声信道的数学模型,并介绍了多目标散射、多径衰落和加性高斯白噪声信道的雷达信号设计方法,最后给出了计算机仿真结果。 相似文献
10.
在采用部分功率训练序列同步的OFDM系统中[1],训练序列会对OFDM承载用户数据的检测造成严重干扰.本文针对每个无线分组包中只有一个OFDM符号,即训练序列和用户数据同时在一个OFDM符号时间内发射,提出一种抑制训练序列干扰的方法,在接收机中分离训练序列、OFDM承载的用户数据.在室内多径衰落信道的条件下,本文分析和仿真了训练序列和OFDM承载用户数据的分离性能,结果表明,分析与仿真结果相近,分离效果明显. 相似文献
11.
Mu Shanxiang Kong Dechun Li Xingguo He Guodong 《电子科学学刊(英文版)》2000,17(2):153-160
A new radar waveform utilizing Costas sequences and interpulse Frequency Hopping (FH) technique is developed, which is a good high range resolution radar signal. The interpulse Costas FH coherent pulse train is introduced and the system block diagram using the interpulse Costas FH waveform is given. In the paper, ambiguity function is employed to study interpulse Costas FH radar. The mathematical expression of the ambiguity function for this waveform is derived. The advantages of the waveform are interpreted by computer simulation. 相似文献
12.
13.
通过建立连续时间模型和离散时间模型,对OFDM的原理进行了详细推导与分析,并得出结论:当循环前缀的长度大于信道频率响应的时间宽度,以及在OFDM符号持续时间内信道衰落近似为常数时,OFDM系统可以看作是一组并行高斯信道。这样就大大简化了接收机均衡器的设计。文章还从时间-频率的角度对OFDM做出了解释,并对OFDM信号的产生方法进行了归纳总结。 相似文献
14.
从正交频分复用(orthogonal frequency division multiplexing,OFDM)技术的角度出发,提出了一种基于循环前缀(cyclic prefix,CP)的OFDM同步位置估计方法[1],旨在接收到CP后能启动同步估计,然后将循环前缀等分为两段信号,比较分段信号的信噪比(signal-noise ratio,SNR),并采用递归二等分的方法得出OFDM有效数据符号的同步起始位置,计算简单,同步速度快。通过仿真论证发现,本文提出的方案较常规方案精确度更高。 相似文献
15.
研究了移动信道中的最大多普勒频移估计技术。分析了一种基于循环前缀的多普勒频移估计算法,该算法通过计算正交频分复用(OFDM)符号已有的循环前缀的相关函数来获得最大多普勒频移。采用广义平稳非相关散射下的多径时变瑞利信道模型,对各个算法进行了仿真试验,比较了各个算法的性能。仿真结果表明,利用多普勒分集技术,可以显著降低误码率,提高系统在移动环境下的性能。 相似文献
16.
与传统的正交频分复用(OFDM)频域信道估计方法不同,提出了一种循环前缀为PN序列的OFDM信道估计方法:在时域OFDM符号中不插入传统意义上的循环前缀,而是插入PN序列作为训练序列,将PN序列与对应的接收序列作圆周相关处理获得信道频率响应估计;而由于PN序列周期性出现,它也起到了循环前缀的作用。仿真结果表明:在多径瑞利衰落信道中,在相同信噪比和相同信道利用率的条件下,提出的算法比频域梳状导频插入的时域滤波算法具有更高的信道估计精度。 相似文献
17.
18.
基于循环前缀的OFDM系统频偏自适应跟踪算法 总被引:1,自引:0,他引:1
为了减小正交频分复用系统受频率偏差的影响,本文提出了基于循环前缀的频偏自适应跟踪算法,该算法利用循环前缀,对载波频偏进行跟踪.文中用最陡下降法和变步长自适应算法进行了计算机仿真,给出了频偏跟踪曲线和BPSK的星座图.理论分析和仿真结果表明,本文提出的方法运算复杂度低,并具有较好的收敛性,能够改善解调性能. 相似文献
19.
OFDM is recognized to be one of the best transmission techniques for wideband wireless communication systems. However, it
exhibits two main drawbacks: its large amplitude fluctuation and its sensitivity to phase noise. Here we consider the phase
noise impairments, taking care of the phase noise spectrum, which diverges form the classical Wiener model as the carrier
frequency increases. Moreover, we show that the phase noise distortion can be decomposed in two terms, one dependent on the
symbol under detection and the other dependent on the symbols of adjacent subcarriers, so that the performance degradation
depends on both the constellation used in each subcarrier and the phase noise spectrum. As a consequence of this new results,
the penalty due to phase noise expressed in terms of the average signal/noise plus interference ratio is not applicable in
the case of modulations with non-constant amplitude constellations, such as 16- or 64-QAM. The method proposed here achieves
a good accuracy, while keeping a low computational complexity, and it is confirmed by simulations.
Roberto Corvaja was born in Padova (Italy) in 1967. He graduated at the Universisty of Padova in Electronic Enginering on 1990 and got his
Ph.D. at the Univeristy of Padova in 1994. Since 1994 he is with the Dipartimento di Elettronica e Informatica of the University
of Padova as a researcher and assistant professor on digital communications. Between 1994 and 1995 he spent 8 months at Hewlett-Packard
Laboratories, Bristol (UK), working on equalization for a DECT receiver. His research activity in the past has regarded optical
fibre communications systems and now is devoted to wireless communication systems.
Silvano Pupolin was born in Venice, Italy, on February 17, 1947. He received the Laurea degree in Electronic Engineering from the University
of Padova, Padova, Italy, in 1970. Since then he joined the Dipartimento di Elettronica e Informatica of the Universita' di
Padova, where he currently is a Full Professor of Electrical Communications. He spent the summer 1985 at AT&T Bell Laboratories
on leave from Padova, doing research on digital radio systems. He has been actively engaged in researches on digital communication
systems since 1970. The topics covered has been: performance of baseband digital comunication systems, line encoding for spectral
shaping, timing extraction, direct detection fiber optic system, spread spectrum communication systems, digital radio communications,
with emphasis to the adaptive linearization of the High-Power-Amplifier. Actually, he is actively engaged in researches on
digital radio, spread s pectrum systems, packet radio networks, personal communication systems and Cellular access to broadband
systems for interactive communications. He is also National Project leader for a research on Personal Communication Systems.
Dr. Pupolin is a Senior Member of IEEE and Member of AEI. 相似文献