基于快速卷积实现滤波多音调制系统的研究

发布时间：2018-05-12 10:15

本文选题：FMT调制 + 多相分解　；参考：《重庆邮电大学》2016年硕士论文

【摘要】：为适应未来海量移动数据流量的飞速增长,第五代移动通信要求最大限度地利用各种频带资源,这对物理层的传输波形提出了更高频域分辨率、更高频带效率等苛刻的特性要求。滤波多音(Filtered MultiTone,FMT)调制是一种基于滤波器组的多载波调制系统。与第四代移动通信物理层核心技术——正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)相比,FMT可以灵活地选择平滑的滤波函数代替OFDM中的矩形函数,从而达到更高的频谱分辨率和更好的频谱约束能力,避免了循环前缀和虚载波等额外开销。但为了满足特定的频率特性要求,滤波器的设计长度往往大于系统符号周期,造成FMT实现工作频率高,运算复杂度大,灵活性差,极大地约束了其在未来下一代网络物理层的应用前景。针对这些问题,本文对FMT系统进行了详细的研究,研究成果如下:1.研究了基于快速卷积的FMT(Fast-Convolution FMT,FC-FMT)实现方案。该方案放弃传统时域实现方式,从FMT系统输入输出信号的频域变化分析出发,利用基于重叠保留法的快速卷积原理,将时域卷积转换为频域乘积,并采用频率抽样法设计原型滤波器,在频域实现了FMT调制系统。通过对子载波滤波器互不重叠的FC-FMT系统进行仿真,验证了该实现方案的有效性,表明了原型滤波器的设计和重叠因子的大小是影响系统的主要因素。2.比较了直接实现、多相实现和快速卷积实现三种FMT系统方案。通过比较得出,快速卷积实现方案因需要引入过采样因子,其频谱利用率低于其他两种实现方案,但其运算速率较低,运算量较少,更适用于实际的高速数据传输。同时,该实现方案可以灵活地选择使用或关闭某段频谱,也可以灵活地控制子信道的中心频率和带宽,具有更好的灵活性。3.提出了一种提高FC-FMT系统频谱利用率的方案(Overlapping FC-FMT)。该方案针对FC-FMT系统频带效率低下的问题,通过控制相邻滤波器间重叠点数来提高系统频谱利用率。首先从理论上推导了由频谱重叠引入的干扰滤波器,并通过仿真验证了在提高频谱利用率的前提下,额外增加的载波间干扰可被控制在一定范围内。然后建立Overlapping FC-FMT系统仿真平台,仿真结果表明在参数(重叠因子、重叠点数、滚降系数)配置不同的情况下,系统表现出不同的性能(运算复杂度、频谱利用率、均方误差等)。正因为Overlapping FC-FMT系统具有这种良好的灵活性的特点,因而在实际应用中,可通过简单地配置最优参数以满足各种业务的不同需求。
[Abstract]:In order to adapt to the rapid growth of mass mobile data flow in the future, the fifth generation mobile communication needs to maximize the use of various frequency band resources, which brings forward a higher frequency domain resolution for the transmission waveform of physical layer. Higher bandwidth efficiency and other demanding characteristics. Filtered multitone FMTM modulation is a multi-carrier modulation system based on filter banks. Compared with the core technology of the physical layer of the fourth generation mobile communication, orthogonal Frequency Division Multiplexing OFDM (OFDM), FMT can flexibly select smooth filtering functions instead of rectangular functions in OFDM, thus achieving higher spectral resolution and better spectral constraint. The overhead of cyclic prefix and virtual carrier is avoided. However, in order to meet the requirements of specific frequency characteristics, the design length of the filter is often longer than the symbol period of the system, which results in the high frequency, high computational complexity and poor flexibility of the FMT implementation. It greatly restricts its application prospect in the next generation network physical layer in the future. In order to solve these problems, this paper studies the FMT system in detail, and the research results are as follows: 1. The implementation scheme of FMT(Fast-Convolution FMT FC-FMT based on fast convolution is studied. This scheme gives up the traditional time domain realization, starting from the frequency domain variation analysis of the input and output signal of FMT system, using the fast convolution principle based on the overlapping reservation method, the time domain convolution is converted into the frequency domain product. The prototype filter is designed by frequency sampling method, and the FMT modulation system is implemented in frequency domain. The effectiveness of the scheme is verified by the simulation of the FC-FMT system where the subcarrier filter is not overlapped. It is shown that the design of the prototype filter and the magnitude of the overlap factor are the main factors affecting the system. Three kinds of FMT system schemes, direct realization, multiphase realization and fast convolution realization, are compared. By comparison, it is concluded that the spectrum efficiency of the fast convolution scheme is lower than that of the other two schemes because of the need to introduce oversampling factor, but its operation rate is lower and the calculation amount is less, so it is more suitable for the practical high-speed data transmission. At the same time, the scheme can flexibly choose to use or close a certain section of the spectrum, but also can flexibly control the central frequency and bandwidth of the subchannel, so it has better flexibility. 3. A scheme to improve the spectral efficiency of FC-FMT system is proposed. Aiming at the problem of low bandwidth efficiency in FC-FMT system, the scheme improves the spectral efficiency by controlling the overlap points between adjacent filters. Firstly, the interference filter introduced by spectrum overlap is deduced theoretically, and the simulation results show that the additional inter-carrier interference can be controlled in a certain range on the premise of improving spectrum efficiency. Then the Overlapping FC-FMT system simulation platform is established. The simulation results show that the system has different performance (computational complexity, spectrum efficiency, mean square error, etc.) when the parameters (overlap factor, overlap number, roll down coefficient) are different. Because of the good flexibility of Overlapping FC-FMT system, in practical applications, the optimal parameters can be simply configured to meet the different needs of various services.
【学位授予单位】：重庆邮电大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN929.5;TN911.3

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