發(fā)布時(shí)間：2018-05-30 02:14

  本文選題：盲均衡 + 循環(huán)平穩(wěn)　； 參考：《南京大學(xué)》2014年碩士論文

【摘要】：衛(wèi)星通信是目前最有應(yīng)用前途的通信技術(shù)之一,該技術(shù)通信距離遠(yuǎn),對地面上的各種電波干擾很不敏感,普遍應(yīng)用于軍事通信、衛(wèi)星電視廣播等方面。然而衛(wèi)星信道的群時(shí)延特性在很大程度上影響了數(shù)據(jù)傳輸質(zhì)量,使得碼間串?dāng)_非常嚴(yán)重。衛(wèi)星通信系統(tǒng)的廣泛應(yīng)用和迅速發(fā)展,使得人們對其均衡性能的要求不斷提高。均衡技術(shù)能夠有效地改善因信道的各種噪聲和干擾引起的碼元失真,在知曉信道參數(shù)的情況下,可以利用訓(xùn)練序列,通過比較已知的發(fā)射序列和接收到的序列的誤差來迭代調(diào)整均衡器的抽頭系數(shù),使得均衡器經(jīng)過多次調(diào)節(jié)最終可以逼近理想狀態(tài)。但是大量的發(fā)送訓(xùn)練序列會浪費(fèi)較多帶寬,引起傳輸有效信息效率降低。在這種情況下,能夠不需要知道信道參數(shù)不需要發(fā)送訓(xùn)練序列,僅利用信號的一些先驗(yàn)信息就能實(shí)現(xiàn)信道均衡的盲均衡技術(shù)越來越成為人們關(guān)注的重點(diǎn)。本文針對衛(wèi)星信道的群時(shí)延傳輸特性,重點(diǎn)研究了衛(wèi)星信道環(huán)境中的盲均衡技術(shù),所做工作有以下幾點(diǎn)： 首先,本文闡述了衛(wèi)星信道的傳輸特性,點(diǎn)明了衛(wèi)星傳輸對均衡技術(shù)要求的迫切性,并根據(jù)衛(wèi)星信道的傳輸特性選取了具有類似特性的信道參數(shù)作為以后仿真的適用信道。 其次本文介紹了均衡器的基本知識,包括傳統(tǒng)自適應(yīng)均衡技術(shù)和盲均衡技術(shù)的有關(guān)概念,相應(yīng)結(jié)構(gòu)及其相互區(qū)別之處。介紹了最基本的均衡算法以及衡量均衡算法性能的相關(guān)指標(biāo)等內(nèi)容,為下文設(shè)計(jì)分析新型盲均衡算法提供理論基礎(chǔ)。 再次針對不同類型的盲均衡算法,本文概要介紹了基于二階循環(huán)平穩(wěn)統(tǒng)計(jì)量的盲均衡算法。首先介紹了循環(huán)平穩(wěn)信號的基礎(chǔ)知識,闡述了一階循環(huán)平穩(wěn)信號和二階循環(huán)平穩(wěn)信號的相關(guān)特性,并根據(jù)循環(huán)平穩(wěn)信號的特性分析了基于調(diào)制引入循環(huán)平穩(wěn)的單信道盲辨識法,這種盲辨識法無需知曉信號參數(shù),僅僅利用發(fā)送信號時(shí)引入循環(huán)平穩(wěn),就可以根據(jù)循環(huán)平穩(wěn)特性采用一些數(shù)學(xué)方法分析并計(jì)算出信道參數(shù)。針對盲辨識算法所采用的基于聯(lián)合調(diào)制和過抽樣引入循環(huán)平穩(wěn)的信號模型,設(shè)計(jì)了循環(huán)維納均衡器,利用了FROST算法解決了均衡器設(shè)計(jì)過程中的受限自適應(yīng)最優(yōu)化問題。 接著本文又介紹了另一類被廣泛應(yīng)用的盲均衡算法Bussgang類盲均衡算法,簡單的闡述了Bussgang過程和幾種經(jīng)典的Bussgang類盲均衡算法,重點(diǎn)討論了恒模盲均衡算法,針對恒模盲均衡算法對相位旋轉(zhuǎn)調(diào)整不足的缺點(diǎn)引出了修正恒模盲均衡算法,對修正恒模算法采用固定步長這個(gè)缺點(diǎn)提出改進(jìn),利用一個(gè)于剩余誤差有關(guān)的非線性函數(shù)來控制修正恒模算法的迭代步長,從而形成了可變步長的修正恒模算法。新算法與修正恒模算法相比收斂速度和收斂精度有了一定的提高。 最后,在現(xiàn)有的單模算法的基礎(chǔ)上引入了多模盲均衡算法。介紹了多模算法的構(gòu)成原理和優(yōu)缺點(diǎn)。在多模算法中最普遍應(yīng)用的雙模盲均衡算法的基礎(chǔ)上,提出了一種新型雙模盲均衡算法。新算法同時(shí)利用切換模式和加權(quán)模式將可變步長修正恒模算法和判決引導(dǎo)最小均方算法相聯(lián)合,與單模算法相比,新雙模算法有著更好的靈活適用性和更高的均衡性能。
[Abstract]:Satellite communication is one of the most promising communication technologies. This technology has a long communication distance and is very insensitive to various interference on the ground. It is widely used in military communications, satellite TV broadcasting and so on. However, the delay of the group of satellite channels greatly affects the quality of data transmission and makes inter code crosstalk very strict. With the wide application and rapid development of satellite communication system, the demand for the equalization performance is improved continuously. The equalization technology can effectively improve the distortion of the symbol caused by the noise and interference of the channel. In the case of knowing the channel parameters, the training sequence can be used, and the known transmission sequence and reception can be received. The error of the sequence iteratively adjusts the tap coefficient of the equalizer so that the equalizer can eventually approach the ideal state after multiple adjustments, but a large number of training sequences will waste more bandwidth and reduce the efficiency of transmission information. In this case, the training sequence can not be needed without knowing the channel parameters, only The blind equalization technology of channel equalization using some prior information of the signal has become the focus of attention. This paper focuses on the blind equalization technology in satellite channel environment for the group delay transmission characteristics of satellite channels, and the following work has been done.
First, this paper describes the transmission characteristics of satellite channel, points out the urgency of satellite transmission for equalization technology, and selects channel parameters with similar characteristics according to the transmission characteristics of satellite channel as the suitable channel for future simulation.
Secondly, this paper introduces the basic knowledge of equalizer, including the concepts of the traditional adaptive equalization technology and the blind equalization technology, the corresponding structure and the differences between them, and introduces the basic equilibrium algorithm and the related indexes to measure the performance of the equalization algorithm, which provides the theoretical basis for the design and analysis of the new blind equalization algorithm below.
The blind equalization algorithm based on the two order cyclostationary statistics is introduced in this paper. The basic knowledge of the cyclostationary signal is introduced, and the correlation characteristics of the first order cyclostationary signal and the two order cyclostationary signal are described, and the modulation based on the characteristic of the cyclostationary signal is based on the modulation. The blind identification method of cyclic stationary single channel is introduced. This blind identification method does not need to know the signal parameters. It can be used to analyze and calculate the channel parameters by using some mathematical methods based on the cyclostationary characteristics. A steady signal model is designed, and a circulant Wiener equalizer is designed. The FROST algorithm is used to solve the constrained adaptive optimization problem in the design of the equalizer.
Then this paper introduces another kind of blind equalization algorithm Bussgang blind equalization algorithm, which is widely used. It simply describes Bussgang process and several classical Bussgang blind equalization algorithms, and focuses on the constant modulus blind equalization algorithm, which leads to the correction of the constant modulus blind equalization for the shortcoming of the constant modulus blind equalization algorithm to adjust the phase rotation. A modified constant modulus algorithm is proposed by using a nonlinear function related to the residual error to control the iteration step of the modified constant modulus algorithm, thus forming a modified constant modulus algorithm with variable step length. The new algorithm is compared with the modified constant modulus algorithm. High.
Finally, the multimode blind equalization algorithm is introduced on the basis of the existing single mode algorithm. The principle and the advantages and disadvantages of the multimode algorithm are introduced. A new double mode blind equalization algorithm is proposed on the basis of the most commonly used double mode blind equalization algorithm in the multimode algorithm. The new algorithm simultaneously uses the switching mode and the weighted mode to change the variable step length. The modified constant modulus algorithm is combined with the decision - guided least mean square algorithm. Compared with the single mode algorithm, the new dual mode algorithm has better flexibility and higher equilibrium performance.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN911.5;TN927.2

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