有色观测噪声下的自适应 UKF 在北斗多路径误差削弱中的研究

针对由环境复杂性而造成的北斗多路径误差不能有效削弱的问题, 提出了一种基于新的误差模型下的自适应无迹卡 尔曼滤波(UKF)方法。 该方法首先利用量测状态扩增法来解决量测噪声为有色噪声的问题,再用改进的 Sage-Husa 自适应 UKF 来动态估计系统噪声和量测噪声,从而解决噪声统计特性未定造成的误差削弱效果不明显的情况。 实验结果表明在有色 观测噪声下的改进 Sage-Husa 自适应 UKF 算法相比于传统 UKF,能够将多路径误差削弱近 60%,该方法在针对北斗定位中由于 多路径误差产生的噪声不可知的情况具有很强的适用性。     

Modeling GPS multipath effect based on spherical cap harmonic analysis

Most GPS positioning errors can be eliminated or removed by the differential technique or the modeling method, but the multipath effect is a special kind of system or gross error, so it is difficult to be simulated or eliminated. In order to improve the accuracy of GPS positioning, the single-epoch pseudorange multipath effects at GPS station were calculated, and firstly modeled based on the spherical cap harmonic (SCH), which is the function of satellite longitude and latitude with the robust method. The accuracy of the kinematic point positioning technique was improved by correcting pseudorange observations with the multipath effect calculated by the SCH model, especially in the elevation direction. The spherical cap harmonic can be used to model the pseudorange multipath effect.     

SDN‐based dynamic multipath forwarding for inter–data center networking

Equal‐cost multipath (ECMP)–based traffic engineering (TE) methods are commonly used in intra–data center (DC) networks to improve the transmission performance for east‐west traffic (ie, traffic from server to server within a DC). However, applying ECMP on inter‐DC wide area network (WAN) offers limited performance enhancement as a result of irregular network topology. Since TE can be intelligently and efficiently realized with software‐defined networking (SDN), SDN‐based multipath becomes a popular option. However, SDN suffers from scalability issue caused by limited ternary content‐addressable memory (TCAM) size. In this paper, we propose an SDN‐based TE method called dynamic flow‐entry‐saving multipath (DFSM) for inter‐DC traffic forwarding. DFSM adopts source‐destination–based multipath forwarding and latency‐aware traffic splitting to reduce the consumption of flow entries and achieve load balancing. The evaluation results indicate that DFSM saves 15% to 30% of system flow entries in practical topologies and reduces the standard deviation of path latencies from 10% to 7% than do label‐switched tunneling, and also reduces average latency by 10% to 48% by consuming 6% to 20% more flow entries than do ECMP in less‐interconnected topologies. Note that the performance gain may not always be proportional to flow entry investment, with the interconnectivity between nodes being an important factor. The evaluation also indicates that per‐flow provision consumes several times the flow entries consumed by DFSM but reduces latency by 10% at most. Besides, DFSM reduces the standard deviation of path latencies from 14% to 7% than do even traffic splitting.     

稳定水声通信判决反馈盲均衡算法研究

水声信道环境恶劣,尤其是多径效应常会造成水声通信系统同步位置发生偏移,对均衡算法造成严重影响。从提高均衡算法稳健性的角度出发。在稳定性较高的归一化常数模算法基础上,借助早迟积分比相原理完成对采样位置的跟踪,并结合判决正方形方法提出一种归一化修正常模盲均衡算法。仿真结果表明．这种基于判决正方形的归一化修正常模盲均衡算法具有更好的收敛能力与稳定性,具有较强的抗干扰能力,能保证水声通信高效运行。     

一种多载波MFSK信道编码方案

目前随着硬件和编码技术的提升,逐渐成熟的多载波技术在通信过程中得到广泛的推广和应用。为了在较严重的多径衰落条件下获取更高的频谱利用效率,采用静态多抽头信道建模的方式对无线信号传播进行模拟。以信道冲击响应数据的误码率作为分析基础,设计了一种引进正交频分复用及多天线技术概念进行改良的多载波MFSK编码方案,并验证了在多径衰落条件下的频谱使用效率及误码率,从而证明了该方案在提高频谱效率方面的可行性。     

多路径环境下电信流量模型研究

在下一代通信网络中,一个终端可同时拥有多个网络接口,在一对源、目的终端间存在多条可用路径。这为网络通信提供了一种全新的思路,即利用多条路径并发进行数据传输。针对多路径传输出现的问题,文章为多路径传输建立了流量模型,分析了多路径传输流媒体的优势,提出了＂流体带宽＂和＂流体调度＂的概念,并引入网络流理论计算了多路径环境下的目标流量。     

划分相位空间的PN码捕获性能分析

频率选择性衰落信道中,接收伪噪声(Pseudo-Noise,PN)码的不确定相位空间中存在多个同相单元。建立检测模型获得了检测过程的检测概率和虚警概率。通过状态转移图结合划分码相位子空间的方法对捕获状态的循环流转进行了描述,获得了捕获性能对信道特性的依赖关系。数值仿真给出了捕获性能随路径数量和接收信噪比等主要参数的变化趋势。     

移动自组织网络中能源信息熵的需求多路径路由协议(英文)

This paper provides a critical review of energy entropy theory in Mobile Ad Hoc Networks (MANETs) and proposes an Energy Entropy on Ad Hoc On-demand Distance Vector Multipath (EEAODVM) routing protocol. The essential idea of the protocol is to find every route which can minimize the node residual energy in the process of selecting path. It balances individual node battery energy utilization and hence prolongs the entire network lifetime. The results of simulation show that, with the proposed EEAODVM routing...     

一种抗信道多径的扫频-扩频调制技术

水声信道是复杂的多径快衰落信道,其信道特性严重影响了水声通信的数据率和性能,抗多径干扰是提高水声通信系统性能的重要技术之一。对一种新的调制方法——扫频-扩频载波（Sweep-Spread Carrier,SSC）调制技术进行了深入研究,通过系统在水声信道实际数据的仿真,探究SSC的抗多径性能,简化了抗信道多径算法。SSC的基本思路是采用连续变化的载波频率,通过相关接收,将接收的多径信号在频域上分离,从而克服了码间干扰的影响。分析了在给定系统时不同信道多径时延对SSC性能的影响,以及给定信道时不同SSC参数对SSC性能的影响。仿真结果表明,选择合适的参数,SSC调制具有良好的抗多径性能。     

水下报文通信抗干扰方法

针对水声通信中的衰减信道和多途效应对报文通信的影响,利用混沌编码方式以获取处理增益,并利用拷贝相关器对信道进行估值的基础上,提出了用相干重置的方法对多途效应加以利用,以降低误码率.仿真结果表明,相干重置的方法相对于直接相关解码方法具有更低的误码率.由此可见,以上的方法对减少多途干扰的影响是有明显的效果的.水声通信一般部...