基于CMMB传输系统的粗符号定时同步算法

为了减少无线信道中存在的多径和频偏对中国移动多媒体广播(CMMB)系统传输信号同步的影响,结合CMMB标准协议规定的具体帧结构,分析了符号同步对系统的影响,讨论了传统最大似然(ML)算法的优缺点,并基于文献中的无数据辅助算法,提出了一种适合该系统并且复杂度较低的粗符号定时同步算法。仿真结果表明,在AWGN及多径信道环境下,新算法可以有效克服传统算法相关峰不明显的缺陷,其估计性能更好。

基于CMMB手机电视的粗符号定时改进算法

结合CMMB标准协议规定的特殊帧结构,分析了符号同步定时误差对系统的影响,讨论了常用的无数据辅助算法,并在分析该算法特点的基础上,根据CMMB手机电视特点,提出了一种粗符号定时改进算法,然后在AWGN信道和多径信道环境下对改进算法的可行性进行了验证。仿真结果表明,改进算法的估计性能较好,不会出现无数据辅助算法所担心的"平顶"现象,并且该算法不会受到SNR的限制,即使在恶劣的多径信道条件下也能估计出符号的大致起始位置。

OFDM系统符号粗同步技术

OFDM作为一种无线信道环境下高速传输技术近来受到越来越广泛的关注。而符号同步是OFDM系统优良性能的基础,本文提出了正交频分多径(OFDM)的符号粗同步的三种算法。通过Matlab仿真确定其三种算法的优劣,并选择最好算法设计相应的符号同步估计器。

突发OFDM系统中的快速符号定时同步

提出了一种在突发OFDM系统中,基于改进前导序列的快速粗符号定时方法。与传统算法比较,该算法不受频率偏移的影响,适合于频偏捕获之前的符号定时同步。运算复杂度降低,适合于突发通信中的快速同步。提高了定时精度,克服了传统算法符号定时模糊的缺点,所以特别适合于突发模式下频偏捕获之前的快速粗符号定时同步。

Geo-rough Space

Rough set is a new approach to uncertainties in spatial analysis.In this paper,rough set symbols are simplified and standardized in terms of rough interpretation and specialized indication.Rough spatial entities and their topological relationships are also proposed in rough space,thus a universal intersected equation is developed,and rough membership function is further extended with the gray scale in our case study.We complete three works.First,a set of simplified rough symbols is advanced on the basis of existing rough symbols.Second,rough spatial entity is put forward to study the real world as it is,without forcing uncertainties into crisp set.Third,rough spatial topological relationships are studied by using rough matrix and their figures.The relationships are divided into three types,crisp entity and crisp entity (CC),rough entity and crisp entity (RC),and rough entity and rough entity (RR).A universal intersected equation is further proposed.Finally,the maximum and minimum maps of river thematic classification are generated via rough membership function and rough relationships in our case study.