fading spectrum 中文意思是什麼
fading spectrum
解釋
衰落頻譜-
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。 -
The advantages of spread spectrum communication are as follows : low probability of intercept, good anti - fading and anti - multipath interference capability. it is widely used in military and civil communication
擴頻通信具有低截獲率、抗衰落能力強、抗多徑干擾等優點，廣泛應用於軍事通信和民用通信。 -
However, multipath components can be resolvable due to the autocorrelation of the spread spectrum signal, thus the optimal receiver equals coherent rake reception, i. e. maximum ratio combining the independent components which endure flat fading or frequency non - selective fading. synchronization of pn code and separation of resolvable multipath components need to estimate the exact time delay among the multipath components
但是利用擴頻信號的自相關特性，可分辨多徑可以被有效分離，最優接收機等效為對多個具有獨立平坦衰落通道（或頻率非選擇性通道）特性的多徑信號進行最大比合併，即相干rake接收。 -
It has been proven that the spread spectrum technologies have good capabilities of overcoming isi in electromagnetic wireless channel. the feasibilities of their applications to underwater acoustic channel have been analyzed, the frequency hopping technology is chosen. instead of using time - frequency diversity, convolutional coding and viterbi decoding are employed to combat signal fading, consequently the bit - rate and bit - error - rate performance of the underwater acoustic voice communication system can be balanced and controlled
由於擴頻技術在抗碼間干擾方面具有優良的特性，因此在分析了各種擴頻技術于本研究應用的可行性之後，確定了跳頻技術作為具體實現方案；在克服幅度衰落方面，選用卷積編碼和維特比譯碼方法來替代原有的分集技術以綜合調節系統的通信速率與誤碼性能，達到差錯可控的目的。 -
Because of the affection of noise and signal fading, in order to high data rate access and high quality, wireless communication need new technology to improve the link reliability and enhance the spectrum efficiency. mimo ( multiple input and multiple output ) can enhance the spectrum efficiency and increase channel capacity greatly, and reduce the multipath affection without spectrum band and power increasing. the 3th generation mobile communication wcdma is coming, with the purpose of putting mimo, stbc ( space time block coding ), space diversity into practice of wcdma systems, in order to lay the foundation of 3g toward 4g, this dissertation has done some research under this background
在發射機和接收機使用多個天線進行數據傳輸的多輸入多輸出（ mimo ）技術，可以在不增加帶寬和天線發送功率的條件下，成倍的提高頻譜利用率，提高系統的通道容量，還可以抗多徑干擾。第三代移動通信wcdma即將到來，為了將多天線技術（ mimo ） ，空間分集技術，空時編碼技術用到wcdma系統中去，為第三代移動通信向第四代移動通信系統平穩過渡奠定一定的基礎，需要做一些理論上的研究。 -
Recently spread spectrum technique has been used widely in wireless data communication, cellular mobile communication, military communication and telemetry monitor system with resistance to interference, high usage of spectrum, resistance to multi - path fading, so investigators in communications field pay more attention to the technique, especially direct sequence spread spectrum ( dsss ) technique
近年來，擴頻技術以其抗干擾能力強、頻譜利用率高、抗多徑等優越性能在無線數據通信、蜂窩移動通信、軍事通信以及遙測監控系統中獲得了廣泛的應用，並日益受到通信領域研究人員的重視，特別是直接序列擴頻技術（ dsss ） 。 -
And the orthogonal frequency division multiplexing ( ofdm ) is given more and more attention in wireless area, because ofdm lessens the severe effects of frequency selective fading and improves the spectrum efficiency, and this technology has been indicated to become a key technology in the fourth moving communication
其中ieee802 . 11a協議中使用到的ofdm （正交頻分復用）技術，由於其先天具有抗多徑衰落及頻譜使用率高等特性，成為當代無線通信領域研究的熱點，並預示著為第四代移動通信的關鍵技術。 -
Future wireless communication systems trend to provide multi - services to mobile users. cdma technique is adopted by the 3rd generation mobile communication systems due to its flexibility in supporting multi - services. how to keep qos of heterogeneous services and utilize the scarce radio spectrum resources is challenging for 3rd generation mobile communication systems in this thesis we developed a radio resource allocation framework for wireless code division access ( cdma ) networks that support multi - class traffic with different data rates and bit error rate requirements. we proposed a new resource allocation scheme using joint adaptive power control and mmse multiuser receiver in multipath fading system
為移動用戶提供多種業務服務是未來無線通信網路的主要發展方向。由於cdma技術具有靈活支持多種業務的優點，因而被第三代移動通信系統所采納。如何在惡劣的無線傳播環境里以及用戶運動且相互干擾的情況下為為各類業務提供qos保證，同時充分利用珍貴的無線頻譜資源，是基於cdma技術的第三代蜂窩通信系統必須致力解決的問題。 -
The closed - form performance formulae of cck modulation are derived under awgn channel and rayleigh fading channel, whose validity is proved by simulations. multi - carrier wideband cdma architecture based on complete complementary codes spread ( ccc - cdma ) has high spectrum efficiency without mai theoretically, which meets the general requirements of b3g communications
研究了高速無線局域網ieee802 . 11b中的基帶技術，特別是基於互補碼擴頻的cck調制，推導出其在高斯噪聲通道和在多徑衰落通道條件下的性能公式。 -
The direct sequence spread spectrum ( dsss ) signal has been widely used, owing to the ability of lower working signal - to - noise ratio ( snr ), strong anti - jamming, lower probability interception and mitigating the effects of multi - path fading
直接序列擴頻（ dsss ）信號由於具有工作信噪比低、強抗干擾性、低截獲率、能夠抑制多徑效應等優點，已經得到廣泛應用。
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