【摘要】：LED可以在滿足照明的同時(shí)實(shí)現(xiàn)高速通信,具有通信速度快、安全、抗電磁干擾等特點(diǎn),具有廣泛應(yīng)用前景。但由于照明需要,采用多個(gè)LED陣列作為信號(hào)發(fā)射源,造成多徑效應(yīng),降低通信質(zhì)量。為此抗多徑能力較強(qiáng)、多信號(hào)源同時(shí)傳輸?shù)腗IMO-OFDM調(diào)制方法得到應(yīng)用。然而MIMO-OFDM中信號(hào)由多個(gè)子信道信號(hào)組成,隨著信號(hào)中同向成為的疊加,必然會(huì)引起較高的PAPR(峰均值比)。實(shí)驗(yàn)表明,較高的峰均功率比會(huì)造成信號(hào)在通過相關(guān)器件時(shí)的非線性失真。因此,降低均峰值比成為提高基于MIMO-OFDM的可見光通信系統(tǒng)質(zhì)量的重要途徑。目前降低峰均值比的方法可以分為三大類：概率類、信號(hào)預(yù)畸變類以及編碼類。其中,概率類算法能夠在不增加誤碼率的條件之下降低系統(tǒng)的PAPR,但是這類算法計(jì)算量加大并且降低PAPR效果不是很明顯；信號(hào)預(yù)畸變類算法結(jié)構(gòu)簡(jiǎn)單、效果明顯,但是會(huì)增加系統(tǒng)的誤碼率。本文從前兩類算法出發(fā),充分均衡了計(jì)算復(fù)雜度、降低PAPR效果以及引入誤差三方面的關(guān)系,提出了一種聯(lián)合使用概率類算法中的部分傳輸序列(PTS)以及信號(hào)預(yù)畸變類算法中的壓擴(kuò)(Companding)的算法—-PTS-Companding算法來降低系統(tǒng)的PAPR。通過研究信號(hào)自相關(guān)性與峰均值比的關(guān)系,疊加自相關(guān)性較低的訓(xùn)練序列來進(jìn)一步降低系統(tǒng)的PAPRo理論分析和MATLAB仿真表明,改進(jìn)算法的計(jì)算復(fù)雜度以及引入誤差與PTS-Companding算法相當(dāng),但是PAPR比PTS-Companding算法的PAPR優(yōu)化了0.7dB左右；引入誤差與壓擴(kuò)算法相當(dāng),但是PAPR比壓擴(kuò)算法的PAPR優(yōu)化了1dB左右；計(jì)算復(fù)雜度與PTS算法相當(dāng),但是PAPT比PTS算法PAPR優(yōu)化了2.2dB左右；比原始信號(hào)優(yōu)化了4.5dB左右。因此本文提出的疊加訓(xùn)練序列的PTS-Companding聯(lián)合算法可以在不增加計(jì)算復(fù)雜度的情況下,降低峰均功率比,提高LED通信系統(tǒng)的通信質(zhì)量。
[Abstract]:LED can realize high speed communication at the same time as lighting. It has the characteristics of high communication speed, safety, anti electromagnetic interference and so on, so it has a wide application prospect. However, because of lighting requirement, multiple LED arrays are used as signal emitters, which result in multipath effect and decrease communication quality. For this reason, the MIMO-OFDM modulation method, which can resist multipath and transmit simultaneously, has been applied. However, the signal in MIMO-OFDM is composed of several sub-channel signals. With the superposition of the same direction in the signal, it will inevitably lead to a higher PAPR (Peak-to-Means ratio). The experimental results show that the higher PAPR results in the nonlinear distortion of the signal passing through the correlator. Therefore, reducing PAPR is an important way to improve the quality of visible light communication system based on MIMO-OFDM. At present, the methods to reduce the peak-to-mean ratio can be divided into three categories: probabilistic class, signal predistortion class and coding class. The probabilistic algorithm can reduce the PAPR, of the system without increasing the bit error rate, but the computational complexity of this algorithm is increased and the effect of reducing PAPR is not obvious. The signal predistortion class algorithm has simple structure and obvious effect, but it will increase the bit error rate of the system. Starting from the first two kinds of algorithms, this paper fully balances the computational complexity, reduces the effect of PAPR and introduces the error. In this paper, we propose a joint use of partial transmission sequence (PTS) of probabilistic class algorithm and compression spread (Companding) algorithm of signal predistortion class algorithm, PTS-Companding algorithm to reduce the PAPR. of the system. By studying the relationship between signal autocorrelation and peak-to-average ratio, we can further reduce the PAPRo theoretical analysis and MATLAB simulation of the system by superposing the training sequence with low autocorrelation. The computational complexity and the introduced error of the improved algorithm are similar to that of the PTS-Companding algorithm, but PAPR optimizes 0.7dB compared with the PAPR of the PTS-Companding algorithm. The introduced error is equivalent to that of the Companding algorithm, but the PAPR of the PAPR algorithm optimizes the 1dB; the computational complexity is similar to that of the PTS algorithm, but the PAPT optimizes the 2.2dB or so compared with the PTS algorithm, and the 4.5dB is optimized than the original signal. Therefore, the proposed PTS-Companding joint algorithm for superposition training sequences can reduce the peak-to-average power ratio and improve the communication quality of LED communication systems without increasing computational complexity.
【學(xué)位授予單位】：東北大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN929.1

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