频率选择性

• However , to achieve this objective , various technical challenges must be overcome . for example , the deployment of broad - band wireless access systems would require a transmission technique which can mitigate the detrimental effects of frequency selective fading
  为达到这一目的，有一些技术问题必须得到良好的解决，比方说在宽带通信模式下由于延迟扩展造成的频率选择性扩展和由多普勒效应产生的信道时域衰落。
• Q30 values of a - i neurons were within from 0 . 24 to 3 . 36 . the values of q30 can also increase with increasing of cfs of neurons , which indicated that the frequency range of acoustic response of a - 1 neurons widened with increasing of cfs of these neurons
  值都有随着神经元cf增高而增大的趋势，这就表明在al区听皮层，随着听神经元cf的增高，神经元的频率选择性能越强，神经元低强度反应的频率响应范围也有增大的趋势。
• The theoretical results are evaluated by simulation . if the coherent bandwidth of channel doesn ’ t exceed the occupied bandwidth of two chips , with the increase of delay spread of the channel , mc - ss - cldd exhibits a better performance to make the system resistant to frequency - selective fading
  研究结果表明,多载波扩频码片级差分检测在单用户和多用户情况下,均适合于时变频率选择性衰落信道,并具有抵抗频率选择性衰落的能力。
• The conclusion is identified by computer simulation . the paper studies a noncoherent demodulation based on differential encoding in mc - cdma system and makes computer simulation of ber performance compared with that of coherent demodulation based on perfect channel estimation
  研究分析了一种使用差分编码的非相干接收mc - cdma系统，对频率选择性瑞利衰落信道条件下的误码率性能进行了计算机仿真，并且和基于理想信道估计的相干解调方案进行了比较。
• The tapped delay model of the multi - path frequency selective fading channels as well as the diversity receiver technique is introduced , and the principles of rake receiver are described . then various downlink channel estimation techniques , such as simple averaging , wmsa and fbprelms are analysed in detail
  本文首先讨论了移动通信信道的各种参数对信道估计的影响,介绍了频率选择性信道的抽头延迟线模型和分集接收技术,在此基础上阐述了rake接收机的原理。
• Ofdm ( orthogonal frequency division multiplexing ) is one of the promising candidates for the next generation wireless communication system , because it has fine channel granularity , the key to support services with various qos requirement , and can easily cope with frequency - selective fading , the challenge to transfer services with high - speed demand such as video stream
  Ofdm ( orthogonalfrequencydivisionmultiplexing )的可用信道粒度小，对付频率选择性保护衰落能力强，是下一代移动通信中的一种非常有竞争力的物理层技术。因为其信道粒度小，因此可以很容易的承载具有多种qos要求的业务，而对付频率选择性衰落能力强的特点使其很适合用来传输视频等具有高速速率要求的业务。
• Stfs is a good coding arithmetic which is simple and easy to realize . moreimportantly stfs has higher diversity order and encoding gain than sts at the samesymbol rate . it can repel channel fading , improve data rate and wireless systemcapacity availability , stand against frequency selectivity fading , eliminate theintersymbol interference
  该编码算法不仅在方法和原理上简单,而且易于实现,在相同符号率下比空时扩频具有更大的分集度和更高的编码增益,能有效抵抗信道衰落、提高数据速率、提高无线系统容量、很好的对抗频率选择性衰落和消除符间干扰。
• Then , base on the determine channel modeling methods , we present a frequency - selective mimo fading channel with von mises probability density function , which is used to characterize non - uniform angle - of - arrival caused by non - isotropic scattering . then we analyze partial cross correlation function of proposed model and proved the model theoretically
  然后,通过对其它多入多出信道模型的分析和对比,并基于确定性信道建模方法,建立了一种通用的频率选择性多入多出衰落信道模型,借助“ vonmises ”概率密度函数,以描述非均匀散射体导致的非均匀本地来波方向分布。
• The results indicate : ( 1 ) there are interactions between the neurons in iso - frequency laminas and hetero - frequency laminas , and the mutual inhibition is predominant ; ( 2 ) the mutual inhibition of the inferior collicular neurons can increase the frequency selectivity , and play an important role in modifying the discharge features of the neurons
  上述结果表明： （ ）下丘神经元声信号处理过程中，位于同频层内及非同频层的神经元之间存在相互作用，该作用以相对抑制为主； （ 2 ） ic神经元之间的相互抑制作用可增强神经元的频率选择性，并对神经元的发放特征有重要的修饰作用。
• In this thesis , for the merits of high frequency spectrum utility factor and high - speed data communication , the ofdm is introduced into the underwater acoustic communication . combined with fec to combat the frequency - selective fades and isi in the underwater acoustic channel , high speed data transmission is realized by employing ofdm technology
  本研究尝试将ofdm技术引入水声通信领域，利用该技术频谱利用率高，多载波并行传送的特点，结合信道编码，以克服水声信道多径干扰引起的频率选择性衰落和码间干扰，获得高速率数据传输。