适用于突发通信的自适应门限解扩技术

针对微波突发通信的扩频解扩同步问题,介绍了一种基于自适应门限的解扩技术,分析了同步序列的相关性,论述了基于自适应门限的算法,提出了解调器设计结构,给出了采用自适应门限算法的相关峰与门限的定量分析,以及在不同信噪比下的仿真曲线。该技术相比传统的扩频同步搜索性能有明显的改善,具有实时性强、门限自适应和同步稳定可靠等特点。     

低信噪比下突发通信的同步检测

针对低信噪比下突发通信系统的同步检测问题,提出了一种利用接收信号平均信噪比和瞬时信噪比设置动态检测门限的同步方法,实现了信号检测门限的设置与信号脉冲出现时刻噪声能量的自适应匹配,提高了低信噪比下同步检测概率。计算机仿真表明在同步序列长度为63时,信号的有效检测工作信噪比可以降低到-5 dB。该方法适合于低信噪比下运动平台间的突发通信系统。     

一种多体制通信时间同步算法及其FPGA实现

基于新一代无线通信统一平台,本文提出了一种适用于多种通信体制的时间同步算法.该算法由帧同步和位同步组成,帧同步和位同步都利用同步序列实现,只需要改变本地同步序列就可以应用于不同的通信体制.仿真结果证明,该算法是可行而且有效的,可以满足平台对时间同步算法性能、复杂读和兼容性等各方面的需求.     

多天线通信系统中一种自适应分组检测算法

针对多天线通信系统,提出了一种基于信道质量的自适应分组检测算法.该算法首先对信道矩阵作修正的选主列QR分解,然后根据各检测层的后检测信噪比与预先计算并存储在系统中的分组门限相比较的结果,将待检符号矢量分为敏感符号分组和可靠符号分组.对敏感符号分组优先采用具有接近最大似然性能的球形译码算法检测,在消除了敏感符号分组影响后,对可靠符号分组采用低复杂度的逐层检测算法.由于分组门限的设置依据后检测信噪比的统计特性,而后检测信噪比与信道环境密切相关,因此,该算法能够根据信道质量自适应调整敏感符号分组中的符号数目,从而可通过选择分组门限,实现对系统检测性能和复杂度的折中考虑.计算机仿真验证了该算法的有效性.     

支持QoS的自适应门限复合光突发装配技术

该文提出了一种新的光突发装配技术,该技术由自适应门限突发装配算法和基于优先级的随机 化的偏移时间设置方案构成.该装配算法特别适合于多类别分组混合装配,能让所有类别的分组公平有效地使用装配能力,能较好地与IP层的QoS机制相匹配。计算机仿真结果表明该文提出的光突发装配技术在性能上具有一定优越性.     

基于同步序列设计的波束同步

波束赋形天线因具有大覆盖范围和高空间分集增益的特性,受到了广泛关注。在波束赋形系统中,指向性波束的同步是实现通信的前提,也是需要克服的挑战之一。文中提出基于同步序列设计的波束同步方法,对同步序列的帧结构、序列种类和序列模式进行详细的设计。仿真结果表明同步序列具有良好的检测性能,与传统方向估计相比,算法显著降低了硬件资源开销,是一种波束同步的低复杂度实现方案。     

自适应调制编码技术在LTE OFDM系统中的性能分析

文章在给出了自适应LTE OFDM系统模型之后,采用基于SNR的自适应算法,对自适应调制及编码技术在LTE OFDM系统中的误比特率性能进行了分析和仿真验证.仿真结果表明,将基于SNR门限的自适应编码调制技术用于LTE OFDM系统,可提高系统性能,且计算复杂度低.     

基于PN码相关性实现MC-CDMA帧同步的分析

由于多载波CDMA(MC-CDMA)技术自身的特点,其同步性能起着非常重要的作用。在基于PN码相关性实现MC-CDMA帧同步的算法的基础上,通过理论分析和仿真研究了虚假相关性峰值概率和循环自相关性对帧同步的影响,并提出用降低循环自相关性和自适应门限来解决影响的新方法。     

基于自适应多门限算法的变换域窄带干扰抑制

该文分析基于门限检测的直接序列扩频通信系统变换域窄带干扰抑制技术,提出一种基于自适应多门限窄带干扰抑制算法,并对其性能进行详细分析,理论分析和数字仿真结果表明,该算法可有效抑制直扩通信系统中的窄带干扰,并且相对于传统的门限检测算法,有自适应性强,门限设计简单等优点。     

LTE系统时频同步算法及其DSP实现

介绍了LTE—FDD系统主同步序列的产生,给出了一种基于主同步信道的时频同步算法,包括符号定时同步算法和频偏估计算法。定时同步算法引入了多径能量窗,并且根据LTE系统同步信道的特点,对多个同步信道上的相关值进行非相干合并,有效地提高了同步性能。对所给出的算法进行仿真,并采用DSP实现同步算法。仿真和实验结果表明,所给出的算法具有良好的性能,能够满足LTE系统对同步性能的要求。     

A Novel Artificial Intelligence Based Timing Synchronization Scheme for Smart Grid Applications

The smart grid control applications necessitate real-time communication systems with time efficiency for real-time monitoring, measurement, and control. Time-efficient communication systems should have the ability to function in severe propagation conditions in smart grid applications. The data/packet communications need to be maintained by synchronized timing and reliability through equally considering the signal deterioration occurrences, which are propagation delay, phase errors and channel conditions. Phase synchronization plays a vital part in the digital smart grid to get precise and real-time control measurement information. IEEE C37.118 and IEC 61850 had implemented for the synchronization communication to measure as well as control the smart grid applications. Both IEEE C37.118 and IEC 61850 experienced a huge propagation and packet delays due to synchronization precision issues. Because of these delays and errors, measurement and monitoring of the smart grid application in real-time is not accurate. Therefore, it has been investigated that the time synchronization in real-time is a critical challenge in smart grid applications, and for this issue, other errors raised consequently. The existing communication systems are designed with the phasor measurement unit (PMU) along with communication protocol IEEE C37.118 and uses the GPS timestamps as the reference clock stamps. The absence of GPS increases the clock offsets, which surely can hamper the synchronization process and the full control measurement system that can be imprecise. Therefore, to reduce this clock offsets, a new algorithm is needed which may consider any alternative reference timestamps rather than GPS. The revolutionary Artificial Intelligence (AI) enables the industrial revolution to provide a significant performance to engineering solutions. Therefore, this article proposed the AI-based Synchronization scheme to mitigate smart grid timing issues. The backpropagation neural network is applied as the AI method that employs the timing estimations and error corrections for the precise performances. The novel AIFS scheme is considered the radio communication functionalities in order to connect the external timing server. The performance of the proposed AIFS scheme is evaluated using a MATLAB-based simulation approach. Simulation results show that the proposed scheme performs better than the existing system.

     

Modelling and performance of packet synchronization in A data communications system

This paper deals with some problems of packet synchronization in a slotted packet-radio communications system. The problems considered are bit-synchronization and unique word detection for bursty systems. The necessary overhead for synchronization purposes is dimensioned for applications in land-mobile satellite communication systems. The performance of synchronization is evaluated using hardware measurement equipment, including a commercial bit-synchronizer. Using these results, the performance loss of communication systems due to packet synchronization effects can be estimated. This is done for the additive white Gaussian noise channel and the class of land-mobile satellite channels.     

无线分组通信网精确定时技术的研究

IEEE 1588标准的基本功能是使分布式网络内的各个时钟与最精确的时钟保持同步,目前主要用于以太网中,无线分组网中尚未移植该协议.本文旨在研究无线分组通信网精确定时技术,分析IEEE 1588定义的PTP(Precision Time Protocol)体系结构和时钟同步原理,提出能在无线分组网络中通过IEEE 15...     

Innovation of EtherCAT adaptive synchronization control in embedded CNC

EtherCAT is a real-time Ethernet protocol and has been widely used in the field of motion control owing to its high speed (100 or 1000 Mbps), low processor occupancy, and good synchronization performance in slaves. However, the master–slave synchronization method is blank in the EtherCAT protocol. The study proposes a novel master–slave synchronization method that relies on the stable sync0 of reference slave by adjusting the trigger moment of master interpolation period to settle packet loss caused by EtherCAT master–slave un-synchronization, adaptively and dynamically. Furthermore, the proposed method improved EtherCAT to a whole new level, indicating that the EtherCAT master no longer depended on the real-time operating system (RTOS). In addition, a synchronization predictive compensation mechanism was adopted to eliminate the compensation lag defect of existing synchronization methods. Compared with conventional studies, the synchronization method improved compensation efficiency, settled inaccurate compensation with evaluation derived from different working frequencies, and eliminated accumulative error in clock. Finally, the proposed method added almost no computation and communication load and only required eight or 16 bytes to modify the EtherCAT frame coding in the interpolation period. Experiments were carried out on machine tools to demonstrate the advantage of the proposed method in improving the synchronization performance, with an average communication jitter of only 32–71 ns.     

核心通信网的光分组交换

文章首先简单说明了新一代通信网需要使用分级交换的由来。接着详细叙述了光分组交换在未来光通信网的应用，包括节点结构、分组格式、输入、输出接口和一些特别重要的技术，如再生、同步、信头处理、缓冲、空间交换和波长转换等。     

A multimedia synchronization model and its implementation intransport protocols

An implementation of a synchronization mechanism in transport protocol to support multimedia applications over a packet or cell switched network is proposed. In designing such a mechanism for practical use, ease of implementation and capability of handling random delay of packets are two key issues for success. Since the random delay of packet or cell switched networks makes synchronization among media more complicated after the transmission across the network, a model which considers the random transmission delay is hence required to specify the temporal relationship among media. Therefore, a real-time synchronization model is presented to satisfy this requirement in the paper. Based on the proposed synchronization model, a transport protocol, namely the multimedia synchronization transport protocol (MSTP), is designed and implemented. We have implemented a prototype system using the MSTP protocol and built a simulation system for the wide area network (WAN) environment in order to evaluate the performance of the MSTP protocol     

PTP技术分析与应用

在通信系统全网IP化的大背景下,分组网络作为统一承载网将面临新的同步需求问题。传统的同步技术精度较低,无法满足新应用对高精度同步的需求。IEEE 1588标准精密时间同步协议(PTP)的提出,成为一种有效解决高精度同步问题的方案。首先分析了PTP技术的同步原理,接着通过综合比较当今几种常用的同步技术的特点得出PTP技术的优势,最后提出了应用方案,并分析了实施过程和部署灵活性。PTP技术可方便灵活地应用于分组网络中,同步精度可达亚微秒级,将成为GPS的有效替代。     

Multimedia synchronization protocols for broadband integratedservices

Protocols to provide synchronization of data elements with arbitrary temporal relationships of both stream and non-stream broadband traffic types are proposed. It is specified that the provision of a synchronization function be performed within a packet switched network, and, accordingly, a two-level communication architecture is presented. The lower level, called the network synchronization protocol (NSP), provides the ability to establish and maintain individual connections with specified synchronization characteristics. The upper level, the application synchronization protocol (ASP), supports an integrated synchronization service for multimedia applications. The ASP identifies the temporal relationships among an application's data objects and manages the synchronization of arriving data for playout. The proposed NSP and ASP are mapped to the session and application layers of the open-systems-interconnection (OSI) reference model, respectively     

A programming model and system infrastructure for real-timesynchronization in distributed multimedia systems

One of the major requirements of distributed multimedia applications is the need to maintain often complex, real-time synchronization constraints. More specifically, it is necessary to be able to manage arbitrary intra- and inter-media synchronization across activities in the distributed environment. Furthermore, it is important that such developments are integrated into emerging object-oriented standards for distributed computing. This paper presents an object-oriented programming model and associated implementation to meet these requirements. The main concepts behind the proposed approach are, firstly, the use of reactive objects for real-time control and synchronization and, secondly, quality of service controlled bindings for predictable communication between objects. The flexibility of the approach is demonstrated by three contrasting examples of real-time synchronization. The implementation extends the real-time capabilities of the Chorus micro-kernel by introducing the concepts of rtports, rthandlers and quality of service controlled connections. The paper demonstrates how reactive objects and bindings are realized on this infrastructure     

分布式仿真系统实时性实现技术研究

针对分布式仿真系统的结构和特点,阐述了计算实时性、通讯实时性和调度实时性3个方面影响系统仿真实时性的主要原因。对于计算实时性问题,提出基于扩展实时操作系统的多线程技术。对于通讯实时性问题,提出采用UDP协议和共享内存技术;对于调度实时性问题,提出采用硬件和软件同步结合的方法来实现时钟同步。通过实践表明,提出的方法是可行和有效的。