fading ratio 中文意思是什麼
fading ratio
解釋
雕萎比-
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。 -
Polarization diversity and maximum ratio combining ( mrc ) is used to restrain the sharp signal fading in the telemetry systems, in which the object is in flight at a high speed and rotating and in low elevation
在信號極化衰弱現象嚴重的環境中對快速飛行目標、低仰角運動目標以及旋轉運動目標等進行遙測接收時，極化分集最大比合成技術可以有效的改善接收性能。 -
3. studying still image transmission systems without channel coding or with turbo codes over both awgn and rayleigh fading channels by matlab simulation. simulation results show that turbo codes not only advance the dependability of communication systems, but also reduce channel signal - to - noise ratio ( snr )
將turbo碼應用於靜止圖像傳輸系統，信源編碼採用矢量量化編碼，分別在awgn通道和rayleigh衰落通道下，對不採用通道編碼和採用turbo碼作為通道編碼的各種情況進行模擬。 -
Finally, performance of adaptive modulation and coding in 11sdpa system is investigated. multi - code channel structure of physical layer, coded modulation schemes and adaptive transmission parameter selection are analyzed. simulation implementation of fading compensation in flat fading channel and maximum ratio combining ( mrc ) in frequency selective fading channel is investigated
最後，本文還研究了hsdpa中自適應調制與編碼性能，分析了物理層多碼通道結構、編碼調制方案、自適應傳輸參數選擇，並研究了平坦和頻率選擇性衰落通道中衰落補償和最大比合併（ mrc ）的模擬實現。 -
Based on the obtained lower bounds on mean squared channel estimation errors, the limits on bit error rate ( ber ) for maximal ratio combining ( mrc ) with gaussian distributed weighting errors on independent and identically distributed ( i. i. d ) fading channels are presented
通過對不同衰落通道多普勒譜的積分，求出了相應的通道估計均方誤差下界的閉合表達式，並在此基礎上得到了分集系統在獨立同分佈的衰落通道中採用最大比合併時的誤碼率下界。 -
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。 -
This article proposes the adaptive algorithm based on equal snr signal noise ratio, and applies it in adaptive ofdm system. in frequency selective fading channel, compared with the traditional ofdm system based on equal power allocation, the system outperforms in ber bit error ratio performance
提出了一種基於最小平均誤碼率的自適應預處理演算法，並將該演算法應用於自適應ofdm系統，在頻率選擇性衰落通道條件下，與等功率分配的ofdm系統相比，誤比特性能有了很大程度的提高。 -
Space - time block codes ( stbc ) based on orthogonal design has attracts enough attentions in its applications in mimo - ofdm systems for its full diversity exploiting and low coding / decoding complexity. these applications include not only system performance improvement, but also reduction of the peak to average power ratio in mimo - ofdm systems. under these backgrounds, this paper first studies space - time block codes under the single carrier, flat fading situation, discusses the encoding / decoding principle and its performance under different channels. then, the author focused on the performance of space - time codes under time selective and frequency selective channels, uncovered the fundamental cause of how maximum doppler shift and power delay profile influences the performance of space - time codes through deduction and simulation
在上述背景下，本文以單載波，平坦衰落通道下的空時分組碼為切入點，深入分析了其編譯碼原理和在不同通道情況下的性能;以此為基礎，後文展開了對空時分組碼在多載波，時間選擇性和頻率選擇性衰落通道下的性能研究，通過理論推導和充分的模擬，揭示了空時/頻分組碼在時頻選擇性衰落通道中的性能變化的根本原因;在以上對多載波系統中空時分組碼的研究的過程中，作者發現了空時分組碼在降低系統峰平比方面應用的可行性，提出了一種降低峰平比的新方法。 -
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。 -
This dissertation researches on wavelet theory applied to information transmission, including cdma spreading code design, waveform coding in digital modulation, over - saturated multi - access communication, diversity techniques for multi - path fading channels, and peak - to - average power ratio ( papr ) reducing methods for the wavelet packet modulation signals, etc.
本文以子波理論為工具，較深入地研究了通道傳輸方面的幾個問題，內容包括cdma擴展碼的設計、數字基帶波形成形技術、過飽和多址通信、克服衰落的分集技術和減小子波包調制信號的峰值功率/平均功率比值的方法等。
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