fading characteristics 中文意思是什麼
-
Shortwave channel is time varying transmission channel. it has dispersion in frequency and time domains. this characteristics hinds the data transmi - ssion at high speed and the correction of received data. in this dissertation i have analyzed the statistic characteristic of shortwa - ve channel, established the model of shortwave channel and simulated the rayl eigh fading distribution. the technology of spreading spetrum has been proved that it has the capability for anti - multipath and discerning multipath
在短波通信中，由於通道的時間色散和頻率色散，引起多徑展寬和多徑衰落，前者限制了數據的傳輸速率，後者造成短波數據通信中出現突發錯誤，為了解決多徑效應對短波通信的影響，本文所做工作如下：首先詳細分析了短波通道的統計特性，建立其數學模型；其次分析了擴頻通信的特點，從理論上證明擴頻技術不僅具有抗多徑干擾能力，而且具有分離多徑的能力；介紹了傳統的rake分集合併技術的特點。 -
In this thesis, first, we present the theory of sess system, the generation of the sess spreading code and its characteristics and the acquisition theory of conventional spread spectrum communication system. an efficient acquisition scheme based on periodically transmitting the synchronization head, which is composed of binary chaotic codes, using the matched filter and automatic decision threshold - level control based on a so - called constant false alarm criterion for sess system is present. the acquisition model of sess system is built and simulated in the awgn channel, the raleigh fading channel and imulti - address interfere condition
本文首先概述了自編碼擴頻通信的原理、自編碼擴頻序列的產生方法及其特性和擴頻通信系統編碼同步的理論，然後針對自編碼擴頻通信系統提出了擴頻序列捕獲方案:周期性地加入混沌序列同步碼，並採用恆虛警率匹配濾波器捕獲法;在加性白高斯噪聲通道、瑞利衰落通道和多址干擾情況下進行了模擬，分析了各種捕獲性能:在選擇性能最優的混沌序列、適當的序列長度、虛警概率及門限值的情況下，可以獲得較短的捕獲時間和較大的捕獲概率。 -
First of all, the characteristics of different adaptive algorithms and equalizers are theoretically researched. then digital microwave communication system model is build by simulink. based on this model, the convergent behavior and bit error rate performance of three equalizers ( nlms, kalman and rls ) are compared in multi - path fading channel
為了達到這個目的，首先需要從理論上對各種自適應均衡演算法以及自適應均衡器的特性進行深入研究;然後利用simulink建立接近實際環境的數字微波通信系統，在多徑衰減通道環境下比較了三種基帶均衡器（ nlms ， kalman和rls ）的收斂特性以及系統誤碼特性，並比較了nlms基帶均衡器和通帶均衡器的性能。 -
The propagation characteristics of underwater acoustic channels and their influences on long - range information transmission are studied thoroughly. based on the sonar equation, the optimal frequency band is abtained. from the calculation about transmission loss, the source level is forecasted. based on the random time varying channel theory, the fading characteristics of long - range underwater acoustic channels are analyzed
系統、深入地研究了水聲通道特性及其對水聲遠程信息傳輸系統的影響；從聲納方程出發，確定了系統的最佳工作頻段；在聲傳播損失計算的基礎上，給出了聲源級的預報；基於時變通道理論，描述了遠程水聲通道的衰落特性。 -
The simulation results based on siso and mimo systems show that the proposed scheme could effectively eliminate the time - variant fading characteristics of wireless channel and under an acceptable demand of ber, the frequency efficiency is enhanced greatly and besides, dynamic encoding is implemented with low complexity and high efficiency
通過在單天線和多天線系統中的模擬，表明該方案可以有效的克服無線通道的時變衰落特性，在滿足誤碼率性能要求的基礎上可以提高系統頻譜利用率，且實現復雜度低。 -
With the characteristics of large ambient noise, very narrow bandwidth, low carrier frequency, great propagation latency and time - space - frequency variant multipath effect ( mpe ), the stochastic ocean channel has demonstrated the greatest complexity and difficulty for underwater acoustic wireless communications. among them multipath effect ( mpe ) is the most difficult obstacle that results in signal fading and inter - symbol interference ( isi )
但是噪聲高、帶寬窄、載波頻率低、傳輸時延大、多途徑效應隨時間?空間?頻率變化等通道特性都會給有效、可靠的水聲通信帶來很大的麻煩，其中多途徑效應是最主要的困擾因素，它會導致信號幅度衰落和碼間干擾。 -
The author considered great numbers of transmission characteristics of real channel in lms model and properly simplified it according to requirement in the project. the key characteristics in the model include multi - path fading, shadow fading, doppler shift, propagation noise, multi - path delay and and state transform of three status homogeneous markov chain described by lms model, etc. the key characteristics of channel are properly collocated and made to be the evidence theory of hardware implementation
Lms模型考慮了大量的實際通道傳輸特性，結合課題需求，實現過程中對lms模型做了適當簡化，考慮了其中的多徑和陰影衰落、多普勒頻移、傳播噪聲、多徑延遲以及lms模型所描述的三狀態齊次markov鏈的狀態轉換等，對其所描述的主要通道特性適當組合，以此作為硬體實現時的理論依據。 -
Rtce is based on forecasting the inherent vulnerabilities to propagation of hf time - varying channel, including multipath delay, doppler spread, selective fading, interference, so this paper also introduces characteristics of hf channel in the beginning. familiar rtce systems all adopt envelope method that bello brought forward
實時選頻技術是基於對短波電離層時變通道固有的不利於電波傳播的各種因素，包括通道的多徑展寬、多普勒展寬、選擇性衰落、噪聲干擾等的預測的基礎上實現的，所以在開篇對短波通道的特點進行了詳細的介紹。 -
The problem of signal processing for direct - sequence code - division - multiple - access ( ds - cdma ) signal over multipath frequency - selective mobile channels is considered. a new blind receiver is proposed. without the knowledge of the multiple - access interference users spreading code and the channel characteristics, the receiver achieves blind detection with prior knowledge of only the desired users spreading code and approximate timing. by using reduced rank adaptive decorrelating filter and adaptive multipath combiner which is based on decision - directed algorithm, the receiver gets the ability to combat both fading and the near - far effect at low cost. simulation results demonstrate that the proposed receiver offers high performance
本文研究多徑頻率選擇性衰落通道下直接序列擴頻碼分多址（ ds - cdma ）信號的處理問題，提出了一種新型的盲接收機.該接收機不需預知多址干擾用戶的擴頻碼，不需預知通道參數，只需已知期望用戶的擴頻碼和粗略的定時，就可以完成用戶的盲檢測.同時，該接收機通過降維自適應去相關濾波和基於判決指導的自適應多徑合併，來獲得低成本和良好的抗衰落、抗遠近效應性能.模擬結果驗證了本文提出的接收機的優良性能 -
And key elements of channel modeling are small - scale fading and multi - path transmission model. therefore the generating principles, statistical characteristics and simulation methods are intensively analyzed and discussed
而小尺度衰落和多徑傳播模型又是通道模型的難點與重點，所以本文對其產生原理、統計特性和模擬方法進行了深入的分析與探討。 -
At this part, it firstly comes up with a quasi - static frequency selective fading channel model. based on this channel model, considering about the characteristics of the model and the lattice reduction complexity, we proposed a new detection strategy, which is the lll detection algorithm combined with decision - feedback technique
首先提出了準靜態頻率選擇性多徑通道模型，然後基於該模型提出了一種新的用於準靜態頻率選擇性通道的檢測方案，即與判決反饋相結合的格約簡輔助檢測方案。
分享友人