【摘要】：可見光通信(VLC)是利用LED作為通信信源,光電檢測器PD作為接收器的一種無線通信方式。VLC作為未來潛在的高速無線通信技術,更高速率成為了通信界不懈的追求。由于光通信采用的強度調制/直接檢測方式以及商用LED調制帶寬較低、電光轉換非線性等因素,單個燈芯的傳輸速率往往受限。針對以上問題,本文對發(fā)送端為單個燈具內的多個燈芯、接收端為單一PD構成的疊加傳輸系統(tǒng)展開分析。主要研究工作如下:1.針對單一LED速率受限問題,提出了采用燈具內多個燈芯并行疊加的傳輸方法,以成倍提升可見光通信的傳輸速率。本文在室內視距鏈路LOS下展開分析和研究,由于VLC采用的商用LED具有電調制帶寬有限、電光轉換線性區(qū)間較窄等缺點,以及受LED和PD物理特性限制所采用的強度調制/直接檢測方式制約,使得LED速率受限;正常的照明是由多個燈芯協(xié)作完成,并且室內VLC中信噪比條件較優(yōu)。由此提出了一種多燈芯疊加傳輸方案,該方式下采用K個燈芯時,系統(tǒng)的傳輸速率可以等效的提升K倍。2.為了檢測多燈芯會聚疊加信號,采用疊加編碼調制(SCM)技術,以驅動電壓差異為檢測條件,建立了可見光通信疊加編碼調制(VLC-SCM)模型,給出了聯(lián)合檢測算法。首先提出了VLC-SCM系統(tǒng)發(fā)送端并行傳輸結構;由于LED的瞬時驅動電壓非負,因此在LED前加上一個直流偏置,提出了基于開關鍵控OOK調制的數(shù)據(jù)處理方式;在Lambertian模型基礎上對多燈芯系統(tǒng)的信道進行了研究,得出了疊加傳輸系統(tǒng)并不依賴信道差異性來區(qū)分數(shù)據(jù),為了檢測疊加后多燈芯會聚光強信號,在發(fā)送端引入各燈芯驅動電壓差異。最后針對多燈芯約束、編碼約束,提出了基于OOK的接收端聯(lián)合檢測算法。仿真驗證了VLC-SCM多燈芯疊加傳輸系統(tǒng)較好的高速傳輸性能。3.為了提升疊加傳輸系統(tǒng)的抗非線性性能,采用交織分多址(IDMA)技術,以交織器差異為檢測條件,建立了可見光通信交織分多址(VLC-IDMA)傳輸模型,給出了串并行兩種檢測算法和快速性能估計算法。分析了系統(tǒng)的發(fā)送傳輸結構,采用交織器這一唯一差異來檢測會聚光強信號。提出了采用低碼率編碼時為全+1的重復碼結構,研究了接收端串行和并行兩種檢測方式,指出在系統(tǒng)性能和實現(xiàn)復雜度上要有所權衡;接著給出了一種多燈芯疊加傳輸系統(tǒng)性能估計算法以快速預測多燈芯系統(tǒng)的性能。仿真驗證了VLC-IDMA多燈芯疊加系統(tǒng)優(yōu)異的高速傳輸性能和抗非線性性能。4.依據(jù)驅動電壓差異、交織器差異和LED的非線性特性,提出了一種聯(lián)合功率分配方案,提升了系統(tǒng)的傳輸效率和檢測性能。針對單一驅動電壓差異時LED容易進入非線性區(qū)間,單一交織器差異使得編碼效率較低,提出了多維差異條件下的疊加系統(tǒng)以提升系統(tǒng)性能。由于燈具內燈芯數(shù)目適中,采用的無窮搜索的信噪比演進和規(guī)劃的聯(lián)合功率分配符合實際需求。仿真表明該方案使疊加系統(tǒng)中LED電壓工作在線性范圍內;與低碼率的多燈芯恒定驅動電壓方案相比,該方案傳輸效率更高。
[Abstract]:Visible light communication (VLC) is a wireless communication mode using LED as communication source and photoelectric detector PD as receiver. As a potential high-speed wireless communication technology in the future, VLC has become the unremitting pursuit of the communication field. Because of the intensity modulation/direct detection method used in optical communication and the low modulation bandwidth of commercial LED, electricity is used. The transmission rate of a single wick is often limited due to the non-linearity of light conversion. To solve the above problems, this paper analyzes the superimposed transmission system consisting of multiple wicks in a single luminaire at the transmitter and a single PD at the receiver. Line superposition transmission method is used to multiply the transmission rate of visible light communication. In this paper, the analysis and research are carried out under LOS. The commercial LED used in VLC has the shortcomings of limited bandwidth of electric modulation, narrow linear range of electro-optic conversion, and the intensity modulation/direct detection method limited by the physical characteristics of LED and PD. Constraints restrict the LED speed; normal lighting is accomplished by multiple wicks, and the signal-to-noise ratio of indoor VLC is better. A multi-wick overlay transmission scheme is proposed, in which the transmission rate of the system can be increased by K times when K wicks are used. 2. In order to detect multi-wicks overlay signal, overlay is used. Coded modulation (SCM) technology, taking the difference of driving voltage as the detection condition, establishes the VLC-SCM model and gives the joint detection algorithm. Firstly, the parallel transmission structure of the VLC-SCM system is proposed. Because the instantaneous driving voltage of the LED is non-negative, a DC bias is added to the front of the LED, and the on-off detection algorithm is proposed. Based on Lambertian model, the channel of multi-wick system is studied. It is concluded that the superimposed transmission system does not depend on channel difference to distinguish data. In order to detect the signal of multi-wick convergence intensity after superimposition, the difference of wick driving voltage is introduced at the transmitter. In order to improve the anti-nonlinearity performance of VLC-SCM multi-wick overlay transmission system, interleaved multiple access (IDMA) technology was used to establish the visible light communication interleaving under the detection condition of interleaver difference. The transmission model of VLC-IDMA is presented. Two detection algorithms, serial-parallel and fast performance estimation algorithms, are given. The transmission structure of the system is analyzed. The unique difference between interleavers is used to detect the convergent light intensity signal. A repetitive code structure with low bit rate encoding is proposed. The serial and parallel detection methods at the receiver are studied. Then, a performance estimation algorithm for multi-wick superimposed transmission system is proposed to predict the performance of multi-wick system quickly. Simulation results show that the VLC-IDMA multi-wick superimposed system has excellent high-speed transmission performance and Anti-nonlinear performance. 4. Interleaving according to the difference of driving voltage. A joint power allocation scheme is proposed to improve the transmission efficiency and detection performance of the system, which is based on the difference between the drivers and the non-linear characteristics of the LED. The simulation results show that the proposed scheme makes the LED voltage in the superposition system work within the linear range, and the transmission efficiency of the proposed scheme is higher than that of the low bit rate multi-wick constant driving voltage scheme.
【學位授予單位】：解放軍信息工程大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN929.1

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