在衰落

The channel property of frequency selective fading and Doppler frequency shift are the biggest challenge to the broadband mobile communication service.

在信道的衰落特性中，对宽带无线移动业务影响最大的是多径衰落和多普勒频移。

Studies of the working class anywhere in the world, once a staple of history and sociology, have declined along with labour movements as a political force; in recent years, perhaps only in France has writing of real distinction appeared.

世界各地的工人阶级研究都曾经是历史学和社会学的最主要内容，如今随着劳工运动作为政治力量的衰落而陷入衰落。在最近一些年，或许只有在法国才有真正突出的著作出现。

Based on the analysis of the Doppler effect of the mobile channel, the performance of two MIMO-OFDM systems (STTC-OFDM and SFBC-OFDM) in the fast-moving environment is studied. Then, the algorithm for channel estimation based on the training sequence is extended into the fast-moving environment by introducing the space-frequency coding, the method of the equal-interval pectinate pilot-inserting, and the complete Maximum-Likelihood space-frequency decoding.

针对快速移动环境中存在的多普勒效应，研究了两种多输入多输出正交频分复用系统在快衰落信道中的误码性能，采用空频编码梳状等间隔导频插入方式，以及完全最大似然空频分组码解码算法，使用导频与接收信号进行信道参数估计，将一般多输入多输出正交频分复用系统中的基于训练序列的最小均方误差信道估计算法推广到了快衰落信道环境中。

To off set the very high economic rents, they live in composted tenement blocks, or terraced houses in the "twilight areas"

为要减低高昂的租金，他们只好挤迫地区住在衰落区的廉价公寓，天台屋

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。

Howard Johnson's, Burroughs, Wimpies, Hallicrafter, Lifeboy, TWA --- moribund brands are legion. All of these were well-advertised and promoted names, but they lost the fight to bring superior value to target customer segments.

Howard Johnson旅馆，Burroughs， Wimpies， Hallicrafter， Lifeboy，，环球航空等等——许多品牌都在衰落，这些品牌过去的广告做得很好，名声也很响，后来却丧失了带给目标客户群更佳价值的战斗力。

While Haass thought that, the present powerful US can not cover up the relative decline in the world position and the absolute decline in the influence and independence, monopolarity era is only a twinkle,21th century is a "dangerous and confused nonpolarity era ".

哈斯则认为，当前美国的强大实力不能掩盖其在世界所处地位的相对衰落及其在影响力和独立性上的绝对衰落，单极时代只是历史的一瞬，21世纪是&混乱危险的无极时代&。

The two transpolar shortwave time signal circuits,Moscow and Irkutsk to the Great Wall Station in Antarctica, are used to study the fading characters for shortwave long circuit.

为了研究过极区的短波长电路的衰落特性，在南极长城站收测莫斯科、依尔库茨克的短波授时台信号，并给出各频率对应的衰落深度、衰落率、衰落平均持续时间等参数的统计特征和衰落幅度分布曲线。

The performance of the concatenated scheme is investigated by both the theoretical analysis and numerical simulations.

我们提出将LDPC与MIMO级联起来的方法，并在衰落信道中进行仿真。

The paper investigates both block-type pilot linear minimum mean square error algorithm and IEEE802.16 OFDM channel estimation analysis. Simulation results confirm the block-type pilot structure is more suitable for IEEE802.16 system. An optimal pilot setting algorithm, based on space frequency domain, is explored and the pilot chart is presented. The proposed algorithm finds its application in MIMO-OFDM. Simulation results show the algorithm presents a good approximation to the perfect channel state information curve, with about 2dB difference in SNR. The simulation results also demonstrate the algorithm achieves fairly high stability in the environment of fast fading, performance of the proposed algorithm is better that of pilot training channel estimation.3. Taking into account the characteristics of IEEE802.16 OFDM system, OFDM system simulation platform is constructed in Matlab, exploiting simulink as a tool. OFDM modulation and demodulation simulation system are configured on LabVIEW platform. All the system signal processing is simulated, including defining system parameters, designing modulation model, and verifying all the proposed algorithms under different environments, such as white Gaussian noise, multi-path fading, with or without guard interval etc. Bit error performance is evaluated. The research provides valid theoretical basis for practical OFDM system performance evaluation.4. Taking advantage of software radio, the paper designs a hardware platform with both 256-IFFT/FFT and 512-IFFT/FFT OFDM schemes co-existing in one platform. You can predetermine one from the two schemes to carry out almost the same model function with different system performance and parameter setting.5. Referring to IEEE802.16 standard, the paper proposes a design method for generating signals and frames suitable for laboratory investigations implemented in laboratory environment.6. Based on 6701evm digital evaluation card, combined with analogy front-end, the paper designs a DSP software model to deal with baseband signal processing. An overall OFDM scheme, with modulation and demodulation function, is accomplished.

讨论分析了MIMO-OFDM中一种基于空频域的最优导频设置算法，给出了导频图案，通过仿真实验表明，该算法与理想的信道状态信息曲线非常接近，信噪比差距约在2dB左右，并且在快衰落条件下具有较好的稳定性，其性能要优于基于前导训练的信道估计方法。3、根据IEEE802.16OFDM系统特点，论文分别在Matlab中应用Simulink工具构建OFDM系统仿真平台、在LabVIEW平台上实现了OFDM调制解调仿真系统，模拟了整个系统的信号流程，进行了OFDM仿真系统参数的选择和调制模块的仿真设计、论证各算法性能，并根据各种不同的条件：例如高斯噪声、多径衰落、有无保护间隔等，对系统的误码特性进行了评估，为正确评价实际OFDM系统的性能提供了有效的理论依据。4、论文以软件无线电思想作为指导，提出了以256点IFFT／FFT为核心和以512点IFFT／FFT为核心的两种OFDM算法模式并存于同一个硬件平台、且可预选的方案，它们在参数选取和性能指标上有所差异，均实现了相似的模块和功能。5、论文参考IEEE 802.16无线网络标准的参数设置，针对本设计系统的应用环境和系统硬件的性能速率，提出了一种应用于实验室环境的信号结构、帧格式等参数设计。6、论文基于TI公司的6701evm数字评估板卡，结合模拟前端搭建数字中频平台，设计了基带处理的DSP软件模块并进行系统调试，基本实现了一套完整的OFDM调制解调方案。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。