無(wú)線可見(jiàn)光通信關(guān)鍵技術(shù)研究
發(fā)布時(shí)間：2018-09-09 15:55
【摘要】：無(wú)線可見(jiàn)光通信系統(tǒng)是指利用可見(jiàn)光波作為信息的載體進(jìn)行信號(hào)傳輸?shù)耐ㄐ畔到y(tǒng)。該技術(shù)方案在提供通信的基本需求以外還具有電磁兼容性良好、無(wú)頻譜許可要求、改善特定環(huán)境下通信質(zhì)量以及提高信息安全性等優(yōu)勢(shì),因此受到學(xué)術(shù)界與工業(yè)界的廣泛關(guān)注。室內(nèi)環(huán)境下的無(wú)線可見(jiàn)光通信技術(shù)使得室內(nèi)LED光源兼顧通信與照明等功能,扣除照明本身的能耗,用于無(wú)線傳輸?shù)哪芎娘@著低于傳統(tǒng)射頻無(wú)線通信系統(tǒng)。近年來(lái),作為研究熱點(diǎn)之一的無(wú)線可見(jiàn)光通信技術(shù),已經(jīng)被更多的研究人員關(guān)注。例如,在光波傳輸機(jī)理下無(wú)線光通信技術(shù)能否逼近傳統(tǒng)信道容量；無(wú)線光通信中高效調(diào)制編碼理論研究等。隨著LED綠色高效光源的推廣普及,室內(nèi)無(wú)線可見(jiàn)光通信技術(shù)將會(huì)被廣泛地應(yīng)用在無(wú)線通信“最后一米”的解決方案中。在這一背景下,無(wú)線可見(jiàn)光通信系統(tǒng)的信道模型和容量分析、光電資源配置與優(yōu)化、高效傳輸調(diào)制與接收研究也必然受到人們的關(guān)注。本文針對(duì)上述室內(nèi)環(huán)境下的無(wú)線可見(jiàn)光通信系統(tǒng)的若干關(guān)鍵技術(shù)展開深入研究,具體說(shuō)來(lái),論文作了以下主要貢獻(xiàn)：本論文第二章針對(duì)光波傳輸機(jī)理,研究了無(wú)線光通信系統(tǒng)的信道容量問(wèn)題。本章研究首先基于泊松光子信道模型,推導(dǎo)得出脈沖位置調(diào)制下的光通信系統(tǒng)的傳輸容量表達(dá)式,進(jìn)一步研究了泊松信道的容量下界問(wèn)題；接著本章考慮了系統(tǒng)傳輸信號(hào)的峰值功率約束對(duì)信道容量的影響,推導(dǎo)得出平均功率與峰值功率約束條件同時(shí)或者分別存在情形下的信道容量上下限,并利用計(jì)算機(jī)仿真結(jié)果表明這些結(jié)果的準(zhǔn)確性；本章最后針對(duì)光正交頻分復(fù)用技術(shù)存在限幅截?cái)嗟奶匦?分析了ACO-OFDM與DCO-OFDM系統(tǒng)限幅信號(hào)的功率,并分別給出系統(tǒng)的最大可行傳輸速率的理論推導(dǎo)。本論文第三章研究無(wú)線光通信系統(tǒng)的信道均衡問(wèn)題。本章分析了無(wú)線光通信系統(tǒng)中碼間干擾的主要來(lái)源,針對(duì)室內(nèi)LED光源調(diào)制帶寬相對(duì)較窄的問(wèn)題提出了分?jǐn)?shù)域均衡的方案,利用信號(hào)過(guò)采樣來(lái)提升均衡濾波器抽頭的分辨率；接著本章根據(jù)理論推導(dǎo)得出的分?jǐn)?shù)域均衡器抽頭系數(shù)最優(yōu)解設(shè)計(jì)了兩種均衡算法,分別給出迫零算法與判決反饋算法的濾波器抽頭系數(shù)解；最后利用計(jì)算機(jī)仿真結(jié)果驗(yàn)證了不同速率下分?jǐn)?shù)域間隔均衡的性能優(yōu)越性。本論文第四章主要研究了DCO-OFDM發(fā)送端優(yōu)化問(wèn)題。我們從光正交頻分復(fù)用調(diào)制的原理出發(fā),分別分析了三種光正交頻分復(fù)用調(diào)制的特點(diǎn)。大部分現(xiàn)有研究工作都只考慮到光信號(hào)單極性的特點(diǎn)而采用了信號(hào)下限幅截?cái)嗖僮鳌?shí)際上如何抑制高峰均比一直是OFDM傳輸系統(tǒng)中的一個(gè)重要問(wèn)題。這一章研究采用上下非對(duì)稱限幅截?cái)嗟姆椒?使得發(fā)射信號(hào)功率滿足光源LED的線性工作區(qū)域要求。同時(shí)為了克服因限幅截?cái)嘁鹣到y(tǒng)誤碼率惡化的問(wèn)題,我們對(duì)DCO-OFDM方案中的偏置電流功率進(jìn)行優(yōu)化。本章研究在保證非對(duì)稱限幅截?cái)酀M足系統(tǒng)硬件需求的同時(shí)最小化所有子載波上的信號(hào)限幅失真函數(shù)。依據(jù)優(yōu)化準(zhǔn)則建立起來(lái)的功率控制問(wèn)題是一個(gè)組合優(yōu)化問(wèn)題,目標(biāo)函數(shù)是非凸函數(shù)。接著本章給出了一個(gè)合理的搜索算法對(duì)全局最優(yōu)解進(jìn)行判定,計(jì)算機(jī)仿真結(jié)果表明合理選擇發(fā)送端偏置電流功率對(duì)于DCO-OFDM系統(tǒng)來(lái)說(shuō)非常必要,也在一定程度上緩解了限幅截?cái)嘣肼晫?duì)系統(tǒng)誤碼率的影響。最后,論文第五章考慮了光正交頻分復(fù)用方案接收端優(yōu)化問(wèn)題。本章利用誤差向量幅度值來(lái)表征接收端信號(hào)的失真水平,并理論推導(dǎo)得出上下限幅截?cái)嘈盘?hào)的誤差向量幅度。在此基礎(chǔ)上,本章給出了最大似然檢測(cè)接收誤比特率的理論值。我們接著給出兩種改進(jìn)型的迭代最大似然檢測(cè)接收算法：1.通過(guò)對(duì)殘留限幅噪聲的迭代估算并對(duì)原始估計(jì)序列的更新得到最大似然算法的析出信號(hào)；2.通過(guò)權(quán)重因子將限幅噪聲高斯白化,使得最大似然估計(jì)檢測(cè)算法滿足最優(yōu)線性估計(jì)條件,再通過(guò)迭代算法得出接收機(jī)析出信號(hào)。計(jì)算機(jī)仿真證實(shí)了本章提出的迭代接收算法可以有效地提高系統(tǒng)的性能。
[Abstract]:Wireless visible light communication system is a kind of communication system that uses visible light wave as the carrier of information to transmit signals. This technology scheme has the advantages of good electromagnetic compatibility, no spectrum licensing requirement, improving communication quality and improving information security in a specific environment, besides providing the basic requirements of communication, so it has received academic attention. Wireless visible light communication technology in indoor environment makes the indoor LED light source take into account the functions of communication and lighting, deducting the energy consumption of lighting itself. The energy consumption for wireless transmission is significantly lower than that of traditional radio frequency wireless communication system. More and more researchers pay attention to it. For example, whether the wireless optical communication technology can approach the traditional channel capacity under the optical transmission mechanism; the research of high-efficiency modulation and coding theory in wireless optical communication. In this context, the channel model and capacity analysis, optoelectronic resource allocation and optimization, high-efficiency transmission modulation and reception research of wireless visible light communication systems will inevitably attract people's attention. In general, the main contributions of this paper are as follows: In the second chapter, aiming at the transmission mechanism of light wave, the channel capacity of wireless optical communication system is studied. Firstly, based on the Poisson photon channel model, the expression of the transmission capacity of optical communication system under pulse position modulation is derived, and the capacity of Poisson channel is further studied. Secondly, considering the influence of peak power constraints on channel capacity, the upper and lower limits of channel capacity are deduced when the average power and peak power constraints exist at the same time or respectively, and the computer simulation results show the accuracy of these results. The cross-frequency division multiplexing (OFDM) technology has the characteristic of limiting truncation. The power of limiting signals in ACO-OFDM and DCO-OFDM systems is analyzed, and the theoretical derivation of the maximum feasible transmission rate is given. In the third chapter, the channel equalization problem in wireless optical communication systems is studied. The main sources of ISI in wireless optical communication systems are analyzed. In order to solve the problem of narrow modulation bandwidth of indoor LED light source, a scheme of fractional domain equalization is proposed, which uses signal oversampling to improve the resolution of equalization filter tap. Then two equalization algorithms are designed according to the optimal solution of fractional domain equalizer tap coefficient derived from theory, and zero forcing algorithm and decision are given respectively. The filter tap coefficients of the feedback algorithm are solved. Finally, the performance of fractional-domain interval equalization at different rates is verified by computer simulation results. In the fourth chapter, the optimization problem of DCO-OFDM transmitter is studied. In fact, how to suppress the Peak-to-Average Ratio (PAPR) is always an important problem in OFDM transmission system. In this chapter, the method of upper and lower asymmetric amplitude-limiting truncation is used to make the transmitted signal power satisfy the light source. In order to overcome the deterioration of BER caused by clipping, we optimize the bias current power in the DCO-OFDM scheme. The power control problem established by the optimization criteria is a combinatorial optimization problem with the objective function being non-convex. Then a reasonable search algorithm is given to determine the global optimal solution. The computer simulation results show that it is necessary and necessary to select the bias current power of the transmitter reasonably for the DCO-OFDM system. Finally, in the fifth chapter, the receiver optimization problem of OFDM scheme is considered. In this chapter, the distortion level of the received signal is represented by the amplitude of the error vector, and the amplitude of the error vector of the upper and lower limit truncated signal is deduced theoretically. In this chapter, we give the theoretical value of the maximum likelihood detection receiver bit error rate. We then give two improved iterative maximum likelihood detection receiver algorithms: 1. The resultant signal of the maximum likelihood algorithm is obtained by iteratively estimating the residual limiting noise and updating the original estimation sequence; 2. The limiting noise is high by weighting factor. The whitening makes the maximum likelihood estimation detection algorithm satisfy the optimal linear estimation condition, and then obtains the receiver emitted signal through the iterative algorithm. Computer simulation proves that the iterative receiver algorithm proposed in this chapter can effectively improve the system performance.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TN929.1
[Abstract]:Wireless visible light communication system is a kind of communication system that uses visible light wave as the carrier of information to transmit signals. This technology scheme has the advantages of good electromagnetic compatibility, no spectrum licensing requirement, improving communication quality and improving information security in a specific environment, besides providing the basic requirements of communication, so it has received academic attention. Wireless visible light communication technology in indoor environment makes the indoor LED light source take into account the functions of communication and lighting, deducting the energy consumption of lighting itself. The energy consumption for wireless transmission is significantly lower than that of traditional radio frequency wireless communication system. More and more researchers pay attention to it. For example, whether the wireless optical communication technology can approach the traditional channel capacity under the optical transmission mechanism; the research of high-efficiency modulation and coding theory in wireless optical communication. In this context, the channel model and capacity analysis, optoelectronic resource allocation and optimization, high-efficiency transmission modulation and reception research of wireless visible light communication systems will inevitably attract people's attention. In general, the main contributions of this paper are as follows: In the second chapter, aiming at the transmission mechanism of light wave, the channel capacity of wireless optical communication system is studied. Firstly, based on the Poisson photon channel model, the expression of the transmission capacity of optical communication system under pulse position modulation is derived, and the capacity of Poisson channel is further studied. Secondly, considering the influence of peak power constraints on channel capacity, the upper and lower limits of channel capacity are deduced when the average power and peak power constraints exist at the same time or respectively, and the computer simulation results show the accuracy of these results. The cross-frequency division multiplexing (OFDM) technology has the characteristic of limiting truncation. The power of limiting signals in ACO-OFDM and DCO-OFDM systems is analyzed, and the theoretical derivation of the maximum feasible transmission rate is given. In the third chapter, the channel equalization problem in wireless optical communication systems is studied. The main sources of ISI in wireless optical communication systems are analyzed. In order to solve the problem of narrow modulation bandwidth of indoor LED light source, a scheme of fractional domain equalization is proposed, which uses signal oversampling to improve the resolution of equalization filter tap. Then two equalization algorithms are designed according to the optimal solution of fractional domain equalizer tap coefficient derived from theory, and zero forcing algorithm and decision are given respectively. The filter tap coefficients of the feedback algorithm are solved. Finally, the performance of fractional-domain interval equalization at different rates is verified by computer simulation results. In the fourth chapter, the optimization problem of DCO-OFDM transmitter is studied. In fact, how to suppress the Peak-to-Average Ratio (PAPR) is always an important problem in OFDM transmission system. In this chapter, the method of upper and lower asymmetric amplitude-limiting truncation is used to make the transmitted signal power satisfy the light source. In order to overcome the deterioration of BER caused by clipping, we optimize the bias current power in the DCO-OFDM scheme. The power control problem established by the optimization criteria is a combinatorial optimization problem with the objective function being non-convex. Then a reasonable search algorithm is given to determine the global optimal solution. The computer simulation results show that it is necessary and necessary to select the bias current power of the transmitter reasonably for the DCO-OFDM system. Finally, in the fifth chapter, the receiver optimization problem of OFDM scheme is considered. In this chapter, the distortion level of the received signal is represented by the amplitude of the error vector, and the amplitude of the error vector of the upper and lower limit truncated signal is deduced theoretically. In this chapter, we give the theoretical value of the maximum likelihood detection receiver bit error rate. We then give two improved iterative maximum likelihood detection receiver algorithms: 1. The resultant signal of the maximum likelihood algorithm is obtained by iteratively estimating the residual limiting noise and updating the original estimation sequence; 2. The limiting noise is high by weighting factor. The whitening makes the maximum likelihood estimation detection algorithm satisfy the optimal linear estimation condition, and then obtains the receiver emitted signal through the iterative algorithm. Computer simulation proves that the iterative receiver algorithm proposed in this chapter can effectively improve the system performance.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TN929.1
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