DCO-OFDM可见光通信系统自适应传输与系统方案改进

发布时间：2018-03-21 15:48

本文选题：可见光通信　切入点：DCO-OFDM　出处：《东南大学》2017年硕士论文　论文类型：学位论文

【摘要】：可见光通信技术,以其诸多的优点,成为近年来无线通信领域研究的热点之一。而OFDM是可见光通信高速传输的基本调制方法,本文针对DCO-OFDM可见光通信系统的自适应传输与系统方案改进问题进行了研究,主要工作如下:一、改进了 DCO-OFDM室内可见光通信系统的频域LS信道估计算法和信道冲激响应抽头个数估计方法。论文在介绍基于DFT变换的信道估计算法基础上,在存在虚拟子载波条件下,仿真比较了一些已有的改进的方法:外推法、迭代法、时域LS估计算法。此外,还提出了 DCO-OFDM系统信道冲激响应有效抽头个数估计的改进方案,并将此改进方案应用到存在STO的DCO-OFDM系统,降低了"平台效应",提升了系统MSE性能。二、改进了 DCO-OFDM室内可见光通信系统的自适应调制算法。论文在介绍注水原理的基础上,结合Greedy算法,根据充分利用功率余量原则,提出了一种改进的固定门限自适应调制算法。此外,还对子载波自适应和子带自适应这两种自适应方案的性能进行了仿真比较,并给出了最佳分组策略。三、推导了 DCO-OFDM室内可见光通信系统的最优直流偏置所满足的非线性方程,可以通过迭代解法给出该方程的数值解。在AWGN信道条件下,以光信噪比为基准,在给出了 SNDR表达式的基础上,进一步得到了单边裁剪和对称双边裁剪的最优直流偏置所满足的非线性方程。四、提出DCO-OFDM的改进调制方案PSO-OFDM,该方案是将DCO-OFDM信号极性分离分为正负两个部分,然后分别用两个符号传输。并证明了 PSO-OFDM系统的SNDR性能优于DCO-OFDM以及PSO-OFDM对LED动态范围的要求要低于 DCO-OFDM。五、介绍了作者参与的课题组共同完成的DCO-OFDM室内可见光通信系统接收端数字基带硬件实现方案的设计与实现,主要内容包括:系统总体及参数、硬件实现时的具体框图;接收端各个模块的具体算法,包含帧同步AGC模块、信道估计与均衡模块、相位补偿模块以及QAM软解调模块;定点方案、关键IP核的关键参数以及各个模块的关键时序。
[Abstract]:The visible light communication technology, with its many advantages, has become one of the hotspots in the field of wireless communication in recent years, and OFDM is the basic modulation method for the high speed transmission of visible light communication. In this paper, the adaptive transmission and system scheme improvement of DCO-OFDM visible light communication system are studied. The main work is as follows: 1. This paper improves the frequency domain LS channel estimation algorithm and the channel impulse response tap number estimation method for DCO-OFDM indoor visible light communication system. Based on the introduction of channel estimation algorithm based on DFT transform, under the condition of virtual subcarrier, the paper introduces the algorithm of channel estimation in frequency domain. Some improved methods, such as extrapolation method, iterative method, time-domain LS estimation algorithm, are simulated and compared. In addition, an improved scheme to estimate the number of effective taps for channel impulse response of DCO-OFDM system is proposed. The improved scheme is applied to the DCO-OFDM system with STO, which reduces the "platform effect" and improves the MSE performance of the system. Secondly, the adaptive modulation algorithm of DCO-OFDM indoor visible light communication system is improved. Combined with Greedy algorithm, an improved fixed-threshold adaptive modulation algorithm is proposed according to the principle of power margin. In addition, the performance of two adaptive schemes, subcarrier adaptive and sub-band adaptive, is simulated and compared. The optimal grouping strategy is also given. Thirdly, the nonlinear equation of optimal DC bias for DCO-OFDM indoor visible light communication system is derived, and the numerical solution of the equation can be obtained by iterative method. Under the AWGN channel condition, Based on the optical signal-to-noise ratio (SNR) and SNDR expression, the nonlinear equations of optimal DC bias for unilateral clipping and symmetric bilateral clipping are obtained. An improved modulation scheme of DCO-OFDM, PSO-OFDM, is proposed, in which the polarity separation of DCO-OFDM signals is divided into positive and negative parts. Then it is proved that the SNDR performance of PSO-OFDM system is better than that of DCO-OFDM and the requirement of LED dynamic range of PSO-OFDM is lower than that of DCO-OFDM.5. This paper introduces the design and implementation of the digital baseband hardware realization scheme of DCO-OFDM indoor visible light communication system, which is jointly completed by the author's research group. The main contents include: the whole system and its parameters, the concrete block diagram of the hardware realization; The algorithm includes frame synchronization AGC module, channel estimation and equalization module, phase compensation module and QAM soft demodulation module; fixed point scheme, key parameters of key IP core and key timing of each module.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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