selective fading 中文意思是什麼
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And then facing the problem of the channel estimation of the adaptive modulation system, we conclude out the channel estimation algorithms on maximum likelihood ( ml ) estimation and maximum a posteriori ( map ) estimation under the condition of flat fading channel and selective fading channel in detail. to meet flat fading channel, we simulate the relationship of the ratio between the error covariance in map estimation and ml estimation and pilot symbol message length. the conclusion can be drawn from these results
接著，對自適應調制系統中的通道估計問題難點，詳細推導了平衰落通道條件下和選擇性衰落通道條件下最大似然（ ml ）估計和最大后驗概率（ map ）估計演算法，針對平衰落通道，我們模擬了map估計和ml估計的方差與導頻符號長度的關系，模擬結果表明，錯誤方差受多譜勒頻率的變化影響最大，並且對實際的自適應調制系統，導頻符號長度的取值超過20個符號長度時， map通道估計明顯優于ml通道估計。 -
Because of the simplicity of differential detection system, we could consider to apply it to the selective fading channels instead of coherent detection
由於差分檢測的簡單易實現性，當通道衰落比較嚴重時，可以考慮採用該方法替代相干檢測。 -
Single carrier frequency domain equalization for high data rate transmission systems over frequency selective fading channels
頻率選擇性通道下高速數據傳輸中的單載波頻域均衡技術 -
Under rayleigh fading channel, we also simulated and compared ber in siso 、 simo and mimo systems. secondly, based on careful study the ber and the channel capacity under white noise channel under mpsk modulation when the channel is rayleigh fading, we duduced the expressions of stbc ’ s ber and channel capacity under rice and nakagami fading. and also analysed the performances through numerical simulation using matlab to testify the exactitude of the dudeced expressions. finally, there exists an error floor of stbc through studying on its performance on time - selectiv fading channel. we analysed the reason and proposed two new decode combination scheme to eliminated the error floor and the performance of stbc on time - selective fading channel is improved. and also compared the two scheme ’ s complication and snr gain
這些結果大部分是閉式結果，能比較準確地衡量空時塊碼的性能，並對不同衰落的性能做了相互比較，其結果對空時塊碼的實際應用具有一定的指導意義。實際的通道是時變的，分析了空時塊碼在時間選擇性衰落通道中產生誤差地板效應的主要原因是存在碼間干擾（ isi ） ，在此基礎上提出了兩種能消除誤差地板效應的譯碼合併方案，並對這兩種方案的復雜度和信噪比增益進行了比較。 -
A new approach to equalization of linear single - input single - output time - selective fading channel
時間選擇性衰落通道迫零均衡新方法 -
The following algorithms have been proposed and tested in the thesis : 1 frequency selective fading : combine the isomorphism between the input space and the output space and propose a new approach to blind equalization of the channel. compared with conventional methods, the new approach offers lower computational complexity, better performance, and more robust against the over - determination of the system order ; 2 time selective fading : a new approach to the equalization of time selective channel based on the zero - forced equalizer is proposed which is more simple in its structure of algorithm ; 3 time - varying channel : using the instantaneous mean value changes of the output signal to extract the information of channel variations and model it using ar model, kalman filter is then employed to track channel variations, it bears faster ability in tracking the variation of tv channels ; based on the isomorphism between the inputs and the outputs and some of the approaches using in mimo system, a new algorithm of equalization of simo time - varying channel is proposed, which also share the merits of being robust against the over - determination of the system order ; model the time - varying channel using the multi - resolution decomposition wavelets, and then a blind identification method based " on the model is proposed ; at last, a new model for equalization and identification of mimo system is proposed
主要工作在以下幾個方面： 1 、針對頻率選擇性衰落通道：結合輸入輸出空間同構關系提出一種新的頻率選擇性通道均衡方法，與傳統方法相比，該方法計算量更小，收斂速度更快，性能更優，且對系統階次的過確定表現穩健，具有實際均衡應用價值； 2 、針對時間選擇性衰落通道：提出一種基於迫零均衡的時間選擇性通道均衡方法，演算法結構簡單； 3 、針對時變色散通道：利用瞬態均值曲線提取通道時變信息，對之ar建模，利用卡爾曼濾波器跟蹤時變通道抽頭變化，可以快速跟蹤通道變化；基於輸入輸出空間之間的同構關系以及多輸入多輸出系統的處理方法，提出了新的單輸入多輸出色散時變通道均衡與識別演算法，同樣具有對通道階次過確定保持穩健的優點；結合小波多解析度分析提出一種基於小波模型的通道盲識別演算法；研究時變的多輸入多輸出系統的盲均衡與盲反卷積問題，給出一種時變系統處理模型。 -
The problems of carrier frequency offset estimation under the condition of the agwn channel, frequency flat - fading channel and frequency selective - fading channel are studied in detail respectively
本文仔細研究了在高斯白噪聲通道下、頻率平坦衰落通道下和頻率選擇性衰落通道下高精度估計信號載頻偏差的問題，並對相應演算法提出了一些改進辦法。 -
A time - varying disperse channel is a channel that contain both frequency selective fading and time selective fading
時變色散通道則是同時存在頻率和時間選擇性衰落的通道。 -
Frequency selective fading
頻率選擇性衰落色散衰落 -
Because of the different time delay among multi - paths, the received signal undergoes frequency - selective fading
由於多徑干擾之間具有不同的時間延遲，接收信號將承受頻率選擇性衰落。 -
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
本文首先討論了移動通信通道的各種參數對通道估計的影響，介紹了頻率選擇性通道的抽頭延遲線模型和分集接收技術，在此基礎上闡述了rake接收機的原理。 -
Subsequently the channel was modeled for three types namely additive white gaussian noise, flat fading and frequency selective fading. lastly, the receiver was studied
接下來通道建模成三種不同的類型，即加性高斯白噪聲通道、平坦衰落通道和頻率選擇性衰落通道。 -
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。 -
Based on the research of mimo detections under the flat fading channel, this paper focuses on the mimo detection under the frequency selective fading channel, chiefly aiming at the lll detection algorithm
在對平坦衰落通道下mimo檢測技術研究的基礎上，本文展開了對頻率選擇性通道下mimo檢測技術的研究。 -
In wireless digital transmissions, due to the delay dispersion of the transmitted symbols and the limitation of channel bandwidth, the channel may induce inter - symbol interference ( isi ), which results the frequency selective fading
在無線數字傳輸中，由於時延擴展和通道帶寬限制，引起碼間串擾，產生頻率選擇性衰落。 -
In recent years, there has been a lot of interest in applying orthogonal frequency division multiplexing ( ofdm ) in wireless systems because of its various advantages in lessening the severe effects of frequency selective fading
近年來，正交頻分復用（ ofdm ）作為一種具有高傳輸效率以及良好的抗頻率衰落性能，得到了廣泛的關注。 -
Also, new expression of ser of mqam in frequency selective fading channel with rake combining is obtained, and throughput performance adaptive mqam with rake receiver in multipath rayleigh fading channel is analyzed
本文還得到了mqam在頻率選擇性衰落通道中採用rake合併新的誤碼率表達式，並對採用rake接收的自適應mqam在多徑瑞利衰落通道中吞吐量性能進行分析。 -
Comparison study between the constant modulus decision feedback equalizer ( dfe ) and several others is made on combating the frequency selective fading of uwac, and their tracking performance to time varying is also investigated
?針對水聲通道的頻率選擇性衰落，對比研究了常數模判決反饋盲均衡演算法與其它幾種盲均衡演算法的性能。針對水聲通道的時變特性，研究了該演算法的跟蹤摘要性能。 -
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
為達到這一目的，有一些技術問題必須得到良好的解決，比方說在寬帶通信模式下由於延遲擴展造成的頻率選擇性擴展和由多普勒效應產生的通道時域衰落。 -
With the downlink simulation model constructed, performance of wideband cdma under different radio propagation environment and vehicular speed is simulated. based on system model of mc ds cdma under flat fading channel with relative shifts of spreading sequences within 1 chip and frequency selective fading channel with arbitrary relative chip shifts, performance of multicarrier cdma system with go sequences under different radio environment is investigated
基於多載波直接序列碼分多址在乎坦衰落通道中序列偏移小於1個碼片及在頻率選擇性衰落通道中偏移任意個碼片的系統模型，本文還分析了採用廣義正交序列的多載波碼分多址系統在不同無線傳播環境下的性能。
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