本文選題：可見光通信 + HACO-OFDM��； 參考：《蘭州交通大學》2017年碩士論文

【摘要】：隨著移動互聯(lián)網(wǎng)技術的迅速發(fā)展而無線接入網(wǎng)頻譜資源日趨耗盡,傳統(tǒng)接入網(wǎng)技術正面臨越來越大的挑戰(zhàn)。當今世界正在呼喚一種能拓寬頻譜資源、綠色節(jié)能、可移動的新型接入方式。在此背景下,可見光通信技術應運而生�？梢姽馔ㄐ偶夹g采用白光LED作為光源,利用LED燈光承載的高速明暗閃爍的信號來傳輸信息,適用于各種室內接入場景。它在滿足照明的同時實現(xiàn)通信功能,具有無電磁輻射、高度保密性的優(yōu)勢,是近年來無線通信領域研究的熱點問題之一。然而,LED有限的調制帶寬嚴重限制了可見光通信的傳輸速率,成為了制約可見光通信發(fā)展的瓶頸。解決方法是采用頻譜效率高、調制效果好的正交頻分復用OFDM技術。根據(jù)可見光通信的特點,有學者提出了ACO-OFDM調制方式,但是該調制方式具有頻譜效率低的缺陷。同時,可見光通信中的OFDM同樣面臨著信號峰值平均功率比(PAPR)過高的缺陷,高PAPR的信號在可見光通信的非線性器件中傳輸會引起嚴重失真。因此OFDM應用于可見光通信中,必須對其信號的高PAPR特性進行抑制。針對這些問題,論文進行了相關的研究,主要工作如下:一、針對ACO-OFDM調制系統(tǒng)有用數(shù)據(jù)只在奇數(shù)子載波上傳輸,偶數(shù)子載波閑置,導致頻譜效率低的缺陷,改進一種混合調制方案。在原來的ACO-OFDM調制中偶數(shù)子載波上采用CAP調制。通過比較可以發(fā)現(xiàn),改進后的混合調制方案能夠在不過多增加系統(tǒng)復雜度的情況下提高頻譜利用率。二、針對直接限幅法的不足,研究利用TR算法進行改進。對輸入的OFDM信號進行預處理,經過TR矢量和輸入信號的循環(huán)迭代疊加,抵消了部分輸入OFDM信號的高峰值,之后再進行限幅濾波處理。仿真結果表明,在相同的CCDF值下,改進后的TR-Clipping算法相比于直接限幅法具有更佳的PAPR抑制效果三、針對傳統(tǒng)PTS技術計算復雜度太高和傳輸邊帶信息造成PAPR二次升高的缺陷,研究使用預設閾值和二進制搜索因子作為搜索集合進行優(yōu)化改進。通過比較可以發(fā)現(xiàn),改進算法是一種次優(yōu)迭代算法,由于減少了IFFT運算次數(shù)其計算復雜度低于原來的PTS算法。
[Abstract]:With the rapid development of mobile Internet technology, wireless access network spectrum resources are increasingly depleted, the traditional access network technology is facing more and more challenges. Nowadays, the world is calling for a new type of access which can broaden the spectrum resources, save energy and move. Under this background, visible light communication technology emerges as the times require. The visible light communication technology uses white light LED as the light source and uses the high speed light and dark flashing signal carried by the LED light to transmit the information, which is suitable for various indoor access scenes. It has the advantages of no electromagnetic radiation and high confidentiality. It is one of the hot issues in the field of wireless communication in recent years. However, the limited modulation bandwidth of LED seriously limits the transmission rate of visible light communication and becomes the bottleneck of the development of visible light communication. The solution is to adopt orthogonal Frequency Division Multiplexing (OFDM) technology with high spectral efficiency and good modulation effect. According to the characteristics of visible light communication, some scholars have proposed a ACO-OFDM modulation scheme, but the modulation mode has the defect of low spectral efficiency. At the same time, the OFDM in visible light communication also faces the defect of high peak-to-average power ratio (PAPR). The signal with high PAPR will cause serious distortion in the nonlinear devices of visible light communication. Therefore, when OFDM is used in visible light communication, the high PAPR characteristic of its signal must be suppressed. In order to solve these problems, the main work of this paper is as follows: first, the useful data of ACO-OFDM modulation system is transmitted only on odd subcarriers, and even subcarriers are idle, which leads to the low spectral efficiency. Improve a hybrid modulation scheme. In the original ACO-OFDM modulation, CAP modulation is used on even number subcarriers. It is found that the improved hybrid modulation scheme can improve the spectral efficiency without increasing the complexity of the system. Secondly, aiming at the deficiency of direct limiting method, the tr algorithm is studied and improved. The input OFDM signal is preprocessed, and the tr vector and the input signal are overlapped iteratively, which cancels the high peak value of some input OFDM signals, and then carries on the amplitude limiting filtering processing. The simulation results show that under the same CCDF value, the improved TR-Clipping algorithm has better PAPR suppression effect than the direct limiting method. In view of the disadvantages of the high computational complexity of traditional PTS technology and the secondary increase of PAPR caused by the transmission of sideband information, the simulation results show that the improved TR-Clipping algorithm has better PAPR suppression effect than the direct limiting method. In this paper, the predefined threshold and binary search factor are used as search set to optimize and improve. By comparison, it is found that the improved algorithm is a suboptimal iterative algorithm, and the complexity of the improved algorithm is lower than that of the original PTS algorithm because of reducing the number of IFFT operations.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN929.1

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本文編號：1870913