查询词典 transmission channel

Images are also corrupted during transmission, due to interference in the channel used for transmission.

图像传输过程中还损坏，由于干扰的频道用于传输。

In frequency selective fading channels, different channel has different fading, that is to say, different channel has different transmission quality.

在频率选择性衰落信道中，不同的子信道受到不同的衰落，也就是说有不同的传输质量。

One of their crucial functions is to make up the error recovery due to the deteriorative channel transmission conditions, provide better links condition to the transmission control protocol of upper layer. Then, the study of RLC and MAC two layers retransmission mechanism is very important to whole wireless system.

这两层有一个重要的作用就是弥补无线通信系统中信道条件不理想或底层不理想造成的传输错误，为上层的传输协议提供性能良好的链路环境，提高上层数据业务在无线传输通信系统中的性能，因此研究RLC和MAC层的重传性能对整个无线传输系统是很重要的。

By time-varying filtering, we realize the signal selectivity and interference suppression, especially for the signals with time-varying power spectrum. It is shown herein that conventional eigenstructure based methods are lower dimensional special case of the time-frequency subspace fitting method. The closed-form array response estimation algorithms for blind source separation in wireless communication is also developed in the dissertation by exploiting the data structure of second-order statistics of the array output in the presence of multipath. The proposed method achieves array response estimation with little constraint on signal property and propagation environment such as scatters or angular spread. Moreover, the array utilized here can be of arbitrary geometry and even uncalibrated. Since the closed-form solution is obtained, no misconvergency may occur and large amount of computation can be saved. The equivalent feed model and corresponding optimization designation are proposed to realize the downlink multi-user selective transmission. By coherent and non-coherent superposition of the electromagnetical field, multiple beams can be formed using a single array, so that each co-channel user signal is transmitted in each beam and will not interfered with each other. The proposed system scheme implements the digital beamforming and the channel allocation in the base band, therefore is suitable for the utilization of the radio software technology. The feasibility and effectiveness of the proposed model are proved by the RF experiment.

在窄带条件下，GSC－SSF方法还可以提高阵列的虚拟孔径，从而提高估计的性能；可以证明，Cyclic DOA 和SC-SSF方法可看作该方法的特例或近似； 3、提出了二维GSC－SSF方法和宽带谱相关DOA矩阵方法，利用信号的循环平稳特性解决了宽带条件下二维 DOA 估计问题，并具有阵元数少、计算量较小的特点； 4、提出了时频子空间拟合和宽带时频DOA估计算法，将联合时频分析的理论和方法引入到阵列信号的空间谱估计研究中，利用时变滤波实现信号选择性测向和干扰抑制，特别适合于谱时变信号；可以证明传统特征结构法可看作是时频子空间拟合方法的特例； 5、提出了多用户环境下阵列响应的估计方法——CARE方法，该方法对信号结构和传播参数（主要是散射源分布与角度散布）的约束较少，适用于各种几何结构的阵列甚至未校准的阵列，能够直接得到阵列响应的闭式解，因此计算量小、稳健性好，不存在收敛问题； 6、提出了针对多用户下行选择性发送的阵列等效激励模型、优化设计方法及其系统实现方案，通过空间场的相干叠加与非相干叠加使得单一阵列能够形成多个波束，并保证各波束内的用户信号各不相同且相互干扰最小；其系统方案具有在基带实现数字波束成形、信道分配并便于软件无线电实现的特点，其有效性已得到外场实测数据的证实。

Firstly , we introduce the basic theory of the coding and decoding of the channel which describe the possibility of the errorless transmission in the channel existing interference .

首先从信道编码的基本定理入手论述了在有干扰存在的信道上进行无差错传输的可能性，这是纠错编码研究的理论依据与努力方向。

And then, the paper also introduces the simulation tool software MATLAB which is used in the project, and introduces each module of OFDM including the channel coding, interleaves, modulation, the fast Fournier transformation and the wireless channel in this simulation. Finally, the paper analyzes the flowing diagram of OFDM and carries on the simulations on the simplification module which does not affect the research of the transmission, and then discusses the results obtained from the simulation experiments.

首先介绍了OFDM的历史背景发展现状及趋势研究意义和研究目的及研究方法和OFDM的基本原理基本模型OFDM的基本传输技术及其应用，然后介绍了本课题所用的仿真工具软件MATLAB，并对其将仿真的OFDM各个模块包括信道编码交织调制方式快速傅立叶变换及无线信道进行介绍，最后是对于OFDM的流程框图进行分析和在不影响研究其传输性的前提下进行简化，并且对其仿真出来的数据图形进行分析理解

Based on the channel transmission theory,a complete and concise procedure for calculating the HF skywave's transmission loss is proposed in this paper by using and optimizing the available independent and disperse models reasonably.

根据信道传输理论，在合理选用和优化各种现有的独力分散数学模型的基础上，设计了一种完整而简洁的短波天波传输损耗计算流程，并针对流程中的每一步给出了详尽的数学模型。

Since the method makes joint optimization to the the number of transmission sublayers and the protection level according to the feedback parameter, it can be more adaptive to the channel situation and can obtain higher performance compared with MDFEC method proposed by Puri, which design the object functions and perfoms optimization according to the fixed channel situation.

同时由于该方法根据反馈的出错分组数进行传输子层数和纠错强度的联合优化，与Puri等人提出的按照确定信道条件设计目标函数进行优化的MDFEC方法相比，更能够适应信道条件的变化，从而获得更高的性能。

To overcome the above described drawbacks,P.W.Baier and other researchers propose a novel multi-user transmission scheme for the downlink of TD-CDMA termed joint transmission. This paper discusses the application of JT technology in the FDD system,and proposes a new solution: Through feedback signal,channel pre-estimation is accomplished at the base station.

为此提出了名为联合传输的多用户传输方式，可以利用TDD模式上下行链路移动无线信道脉冲响应相等的优点，只在上行链路对信道进行估计，下行链路利用估计得到的信道冲击响应值，把在移动台判决传输信号的任务交给基站来完成，利用这种技术可以提高系统性能和减少系统复杂性。1系统模型及JT原理联合传输技术[1～3]，可由信道传输概念引出，如图1所示。

AMC selection module periodically measures the wireless channel, updates the state transition matrix of finite-state Markov chain to trace the channel status, and dynamically selects transmission mode, which includes modulation and forward error coding, so as to guarantee packet error rate performance and improve spectrum efficiency.

AMC选择模块周期性地测量无线信道，更新马尔可夫模型转移概率矩阵以跟踪当前的信道特征，动态选择物理层传输模式（包括调制方式和前项纠错编码方式），在保证系统误包率要求的同时，最大可能地提高系统频谱效率。

Neither the killing of Mr Zarqawi nor any breakthrough on the political front will stop the insurgency and the fratricidal murders in their tracks.

在对危险的南部地区访问时，他斥责什叶派民兵领导人对中央集权的挑衅行为。

In fact,I've got him on the satellite mobile right now.

实际上 我们已接通卫星可视电话了