去极化信道中的自适应极化调制研究

发布时间：2018-04-22 22:01

本文选题：极化调制 + 去极化效应　；参考：《北京邮电大学》2015年硕士论文

【摘要】：极化调制(Polarization Modulation, PM)可以突破传统无线通信调制技术对射频功放线性要求的限制,确保功放可以工作在具有高转换效率的非线性区,而且不对承载信息的信号属性造成失真,从而保证较高的有效数据速率。然而将极化状态承载信息引入到无线通信中,面临的一个最大挑战是无线信道特有的去极化效应。无线通信环境的多径和富散射特性会产生严重的去极化效应,如极化相关损耗(Polarization Dependent Loss, PDL)、极化模式色散(Polarization Mode Dispersion,PMD)会严重改变发射信号的极化状态,降低极化调制的传输性能：1)对单载波极化调制造成的损害主要是由PDL效应带来的,表现为信号在信道传播中所遭受到的功率衰减与该信号的发射极化状态相关；2)在多载波通信场景下,由于无线信道的PMD效应,每个载波上的去极化效应呈现出与频率相关的特性,如不同的载波具有不同程度的PDL效应,导致不同载波上的误比特率性能具有差异性。因此,若要在无线通信中利用极化调制,研究抗无线信道去极化效应(如PDL、PMD)的机制或算法很有必要。本论文选题来源于国家自然科学基金项目《基于认知与极化信号处理的功放节能研究,项目批准号：61271177》。论文具体研究了降低极化相关损耗和极化模式色散对极化调制造成影响的自适应极化调制技术,对相关算法或机制进行了较深入的分析和研究。本文的主要研究工作及成果包括： (1)对现有极化信息处理技术、极化调制技术研究、去极化效应分析研究及自适应调制(Adaptive Modulation,AM)技术等关键技术与相关理论进行了分析与综述,指出了利用自适应技术来降低无线信道中PDL效应与PMD效应对极化调制影响的可行性,为展开本论文研究工作奠定了理论与技术基础。 (2)针对单载波通信场景下信道中的PDL效应会导致信号功率衰减,影响极化调制系统误比特率的问题,本文提出了自适应极化调制机制：发送端根据接收端发回的反馈信息自适应的选定最优阶极化调制来传输数据。仿真结果及其分析表明,在满足相同误比特性能前提下,与固定极化调制相比,自适应极化调制在频谱效率方面获得了提升,使极化调制系统得到了优化。 (3)针对多载波通信场景下基于极化调制的正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)系统受到无线信道PMD效应的影响而使得性能下降的问题,本文提出了基于子载波分块的自适应极化调制机制：发送端根据接收端发回的有关当前信道质量情况的反馈信息来计算出每一个子载波块的平均信噪比并与信噪比门限值对比,进一步选定每一个子载波块采用最优阶极化调制来传输数据。仿真结果表明,该机制能有效削弱PMD效应对基于极化调制的OFDM系统中总体误码性能的影响。
[Abstract]:Polarization Modulation (PMN) can break through the limitation of traditional wireless communication modulation technology on the linear requirements of RF power amplifier, and ensure that the amplifier can work in a nonlinear region with high conversion efficiency and does not cause distortion to the signal properties of the information. In order to ensure a higher effective data rate. However, one of the biggest challenges to the introduction of polarization state information into wireless communication is the unique depolarization effect of wireless channels. The multipath and rich scattering characteristics of wireless communication environment will produce serious depolarization effects, such as polarization dependent loss polarization (PDL), polarization mode dispersion polarization Mode dispersion (PMDs) will seriously change the polarization state of the transmitted signal. The damage caused by reducing the transmission performance of polarization modulation: 1) to single carrier polarization modulation is mainly caused by the PDL effect. It is shown that the power attenuation of the signal in the channel propagation is related to the transmitting polarization state of the signal) in the multi-carrier communication scenario, due to the PMD effect of the wireless channel, The depolarization effect on each carrier shows the characteristics related to frequency, for example, different carriers have different PDL effect, which leads to the difference of bit error rate performance on different carriers. Therefore, in order to utilize polarization modulation in wireless communication, it is necessary to study the mechanism or algorithm to resist the depolarization effect of wireless channel (such as PDLPMDs). This thesis comes from the project of National Natural Science Foundation of China < Research on Energy Saving of Power Amplifier based on Cognitive and polarized signal processing, Project approval No.: 61271177 >. In this paper, the adaptive polarization modulation technology which can reduce polarization dependent loss and polarization mode dispersion on polarization modulation is studied, and the related algorithms or mechanisms are analyzed and studied deeply. The main research work and achievements of this paper are as follows: In this paper, the current polarization information processing technology, polarization modulation technology, depolarization effect analysis and adaptive modulation (AM) technology are analyzed and summarized. The feasibility of using adaptive techniques to reduce the effects of PDL and PMD on polarization modulation in wireless channels is pointed out, which lays a theoretical and technical foundation for the research work in this paper. Aiming at the problem that the PDL effect in the single carrier communication scenario will lead to the signal power attenuation and affect the bit error rate of the polarization modulation system, In this paper, an adaptive polarization modulation mechanism is proposed: the sender adaptively selects the optimal order polarization modulation to transmit data according to the feedback information from the receiver. The simulation results and its analysis show that the adaptive polarization modulation improves the spectral efficiency and optimizes the polarization modulation system compared with the fixed polarization modulation under the same bit error performance. In view of the problem of orthogonal Frequency Division Multiplexing (OFDM) based on polarization modulation in multicarrier communication scenarios, the performance of orthogonal Frequency Division Multiplexing (OFDM) systems is degraded due to the influence of the PMD effect over wireless channels. In this paper, an adaptive polarization modulation mechanism based on sub-carrier block is proposed. The transmitter calculates the average SNR of each sub-carrier block based on the feedback information from the receiver about the current channel quality and compares it with the signal-to-noise ratio threshold. Each sub-carrier block is further selected to transmit data using optimal order polarization modulation. Simulation results show that this mechanism can effectively weaken the effect of PMD effect on the overall error performance of OFDM systems based on polarization modulation.
【学位授予单位】：北京邮电大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN761

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