M湍流无线光通信系统的性能分析

发布时间：2018-11-21 07:31

【摘要】：随着通信技术的不断发展,人们对信息交换、互联网络、无线通信以及移动通信技术的要求越来越高。无线光通信以其抗电磁干扰能力强、保密性好、频段无需申请、机型方便架设以及容量大等优点,成为解决新一代通信技术长期演进过程中一种可行的替代技术和有前途的补充技术。本文针对M湍流无线光通信系统,建立更加符合实际的信道模型并提出提高系统传输性能的设计方案,主要的研究工作包括:(1)在对大气传播特性的分析之后,针对引起信号衰减的原因:大气的衰减作用、M湍流作用以及非零指向误差,提出M湍流无线光通信系统的信道模型,此模型可以表征不同程度湍流情况下的无线光通信系统,在此基础之上推导出M湍流无线光通信系统衰减因子的概率密度函数表达式,更加全面地考虑影响无线光通信系统传输性能的因素。(2)根据提出的M湍流无线光通信系统信道衰减因子的概率密度函数表达式,以及容量分析的基础知识,本文对无线光通信系统各态历经容量的上界、下界和中断概率的性能进行分析。研究表明,传输距离、发送信噪比以及大气的衰减情况对M湍流无线光通信系统的性能的影响不容忽视。本文提出的M湍流无线光通信系统各态历经容量的上界和下界之间的差距非常小,并且远小于香农公式推导的各态历经容量,更加符合实际的传输情况。经过仿真发现,减小光接收机的接收半径以及控制瞄准线位移偏差,可以降低系统的中断概率。(3)利用多载波调制系统的速率高以及抗频率选择性干扰强等特点,将正交频分复用的调制技术运用到M湍流无线光通信系统中,分析影响直流偏置光正交频分复用无线光通信(DCO-OFDM)系统平均误码率的因素。因为无线光通信系统的传输信号是非负的实信号,DCO-OFDM系统在发送端加上直流偏置电压,所引起的非线性失真等效为固定的增益与非相干噪声之和。仿真结果表明,系统的平均误码率与发送功率和大气湍流情况有关。一定程度地提高系统的直流偏置电压值,可以降低M湍流无线光DCO-OFDM系统的平均误码率,提高系统传输性能。
[Abstract]:With the development of communication technology, the requirements of information exchange, Internet, wireless communication and mobile communication are becoming higher and higher. Wireless optical communication has the advantages of strong ability of resisting electromagnetic interference, good confidentiality, no need to apply for frequency band, convenient erection of type and large capacity, etc. It has become a feasible alternative technology and a promising supplementary technology to solve the long-term evolution of new generation communication technology. In this paper, a more practical channel model for M turbulent wireless optical communication system is established and a design scheme to improve the transmission performance of the system is proposed. The main research work includes: (1) after analyzing the characteristics of atmospheric propagation, Aiming at the causes of signal attenuation, such as atmospheric attenuation, M turbulence and non-zero pointing error, the channel model of M turbulence wireless optical communication system is proposed, which can represent the wireless optical communication system with different degree of turbulence. On this basis, the probability density function expression of attenuation factor for M turbulence wireless optical communication system is derived. The factors that affect the transmission performance of wireless optical communication system are considered more comprehensively. (2) according to the probability density function expression of channel attenuation factor of M turbulent wireless optical communication system, and the basic knowledge of capacity analysis, The performance of ergodic capacity upper bound, lower bound and interrupt probability of wireless optical communication system is analyzed in this paper. The results show that the influence of transmission distance, transmit signal-to-noise ratio and atmospheric attenuation on the performance of M turbulent wireless optical communication system can not be ignored. The difference between the ergodic capacity of each state and the lower bound of M turbulent wireless optical communication system proposed in this paper is very small, and is much smaller than the ergodic capacity of each state derived from Shannon's formula, which is more in line with the actual transmission situation. The simulation results show that the interruption probability of the system can be reduced by reducing the receiving radius of the optical receiver and controlling the offset of the line of sight. (3) the characteristics of the multicarrier modulation system such as high rate and strong anti-frequency selective interference are utilized. The modulation technology of orthogonal frequency division multiplexing (OFDM) is applied to M turbulent wireless optical communication system. The factors affecting the average bit error rate (BER) of DC biased optical orthogonal frequency division multiplexing (DCO-OFDM) system are analyzed. Because the transmitted signal of the wireless optical communication system is non-negative real signal, the nonlinear distortion caused by the DC bias voltage in the DCO-OFDM system is equivalent to the sum of the fixed gain and the incoherent noise. The simulation results show that the average bit error rate (BER) of the system is related to the transmission power and atmospheric turbulence. To a certain extent, increasing the DC bias voltage of the system can reduce the average bit error rate of M-turbulence wireless optical DCO-OFDM system and improve the transmission performance of the system.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.1

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