室内可见光通信LEDs选择及调制技术的研究

发布时间：2018-02-02 04:18

本文关键词： 可见光通信通信LED 自适应位置调制多脉冲位置调制进化算法　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：智能终端设备的蔚然兴起导致全球数据业务迅猛增长,给原本已经紧张的射频频谱资源带来了巨大挑战,一种新型的绿色节能通信方式——可见光通信(VLC:Visible Light Communication)应运而生。VLC具有超高带宽、频谱无需授权即可使用、无电磁干扰、低功耗等优势,自提出后便迅速受到世界各国关注。近几年关于VLC的研究更是如火如荼。为了照明均匀,实际室内VLC系统中,光源由多LED(Light Emitting Diode)单元组成的阵列构成。然而,多单元LED阵列存在因光程差不同而导致的符号间干扰(ISI:Inter Symbol Interference)问题。此外,多LED阵列带来的ISI还加剧了室内信噪比(SNR:Signal Noise Ratio)分布的不均匀性,且ISI随调制阶数的动态变化给自适应调制阶数的选择带来了困难。本文通过比较了所有LEDs参与通信与部分LEDs参与通信下的接收SNR,发现所有LEDs参与通信下的SNR效果不佳,这引起了我们探索最佳通信LEDs选择的兴趣。本文将最佳通信LEDs选择问题建模为优化SNR的问题,针对单终端场景提出基于有效比阈值的通信LEDs选择方法,针对多终端同时通信的场景提出基于进化算法的通信LEDs选择方法。在自适应调制阶数选择的问题上,提出基于逐步递增的调制阶数选择方法。本论文的主要工作论述如下:(1)探讨下行单终端通信情况下的最佳通信LEDs选择问题。从一个新的视角看,每个通信LED信号包含了积极和消极两部分。提供有用功率的部分为积极成分,产生干扰噪声的部分为消极成分,两者之比定义为有效比(VR:Valid Ratio),有效比的阈值表示为Th VR。对于单用户的场景,本文提出了基于有效比阈值的方式来优化SNR。LED单元是否参与通信取决于有效比,其有效比大于Th VR,则参与通信,否则仅提供照明。这样,通过选择一个合适的Th VR来确定最佳的通信LEDs,终端可以达到较高的数据速率。此外,本文还探讨了视场角、数据速率对SNR和通信LEDs选择的影响。(2)在下行广播系统中,一般存在多个终端同时通信,在这种场景下,基于有效比阈值的方法不再适用,因为不同位置的终端对应的最佳通信LEDs是不一样的,接收SNR随不同通信LEDs呈无规律变化。一个LED可能为某一终端提供较多的有用功率,但它同时可能给其他终端带来严重的干扰。为了多个终端用户能同时保障高质量通信,本论文构建了一个通信LEDs选择的优化问题,寻求多个终端用户中最小信噪比达到最大时的通信LEDs。为了找到最佳的通信LEDs,本论文提出基于进化算法的通信LEDs选择方案并通过仿真分析验证。(3)由于各位置接收器与光源间的距离不同,信噪比的分布呈现不均匀性,且多LEDs带来的ISI问题加剧了信噪比分布的不均匀性。为了充分利用信道,本文提出了自适应位置的多脉冲位置调制(MPPM:Multiple Pulse Position Modulation),不同位置的SNR不一样,所选择的MPPM调制阶数也不同。SNR高的位置可以选择高阶的调制方式,但是高阶调制方式又会增大ISI,从而降低SNR,ISI随调制阶数的动态变化给调制阶数的选择带来了挑战。因此,本论文提出逐步递增的方法来选择最佳的调制阶数,研究所有LED参与通信和部分LED参与通信时的自适应位置阶数选择问题。本论文从新角度、新方法探索研究室内可见光通信的通信LED选择问题、MPPM自适应位置调制阶数选择问题,研究成果可为VLC的广泛应用提供一定的理论依据和参考价值。
[Abstract]:Intelligent terminal equipment leads to the rise of global business data increase rapidly, which brings a great challenge to the already tense radio spectrum resources, a green energy-saving new communication mode: visible light communication (VLC:Visible Light Communication) came into being.VLC with high bandwidth, the spectrum can be used without authorization, no electromagnetic interference, low power consumption the advantages of quickly attracted world attention. The research on VLC in recent years is like a raging fire. For uniform illumination, the actual indoor VLC system, the light source is composed of multi LED (Light Emitting Diode) array unit formed. However, multi unit LED array optical path difference caused by the presence of different symbols interference (ISI:Inter Symbol Interference). In addition, the multi LED array brings ISI also intensified the indoor signal-to-noise ratio (SNR:Signal Noise Ratio) inhomogeneity, The dynamic changes of ISI with the modulation order and brings difficulty to the adaptive modulation order selection. By comparing all the LEDs in communication with some of the LEDs in receiving SNR communication, found that all the LEDs in communication under SNR effect is poor, which caused us to explore the best choice in LEDs communication. This paper will be the best communication LEDs selection problem is modeled as optimization problem of SNR for single terminal presents is more effective than the threshold selection method based on LEDs communication, the communication terminal at the same time the scene selection method is proposed based on LEDs algorithm. The communication in the adaptive modulation order selection problem, modulation order selection method is proposed based on the gradually increasing. The main work of the thesis are as follows: (1) to explore the best communication LEDs downlink single terminal communication case selection problem. From a new perspective, each communication signal LED The two part contains positive and negative power. Provide a useful part of active ingredients, the interference noise is passive components, both the ratio is defined as the effective ratio (VR:Valid, Ratio) is more effective than the threshold expressed as Th VR. for the single user scenario is proposed in this paper based on the effective way to optimize the threshold the SNR.LED unit is involved in communication depends on the effective ratio of the effective ratio is greater than Th VR, is involved in communication, otherwise only provide lighting. In this way, by choosing a suitable Th VR to determine the best communication LEDs, the terminal can achieve high data rate. In addition, this paper also discussed the effect of data rate on the angle of view SNR and LEDs communication options. (2) in the downlink broadcast system in general, there are multiple communication terminals at the same time, in this scenario, the effective ratio threshold method is no longer suitable for different positions based on the corresponding terminal Good communication is not the same as LEDs, receiving SNR with different communication LEDs irregular changes. The useful power of a LED may provide more for a terminal, but it may also bring serious interference to other terminals. In order to multiple end users can also guarantee the high quality of the communication, this paper constructs a communication LEDs selection optimization problem for multiple end users in the minimum signal-to-noise ratio of LEDs. reached the maximum when the communication in order to find the best LEDs communication, this thesis proposes alternative communication LEDs evolutionary algorithm and verified by simulation. Based on the (3) due to the different position of the receiver and the distance between the light source and the distribution of signal-to-noise ratio the present is not uniformity, ISI and multi LEDs has exacerbated the signal-to-noise ratio of the uneven distribution. In order to make full use of the channel, this paper proposes the adaptive location of multi pulse position modulation (MPPM: Multiple Pulse Position Modulation, SNR) in different positions are not the same, MPPM modulation order choice of different.SNR high position can choose high order modulation, but high order modulation will increase ISI, reduce SNR, dynamic changes of ISI with the modulation order is a challenge to the modulation order selection. Therefore, the proposed method progressively to select the optimal modulation order, of all the LED adaptive position order selection problem in communication and LED communication. In part this paper from a new perspective, explore new methods of communication of LED indoor visible light communication selection problem, MPPM adaptive position modulation order selection problem and the research results can provide a theoretical basis and reference value for the application of VLC.

【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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