SyncML数据同步协议研究

SyncML(Synchronization Markup Language)数据同步规范是数据同步的国际标准,它支持多种传输协议,能在多种网络和设备上进行数据同步。文中主要介绍了SyncML规范的结构,SyncML同步协议,分析了同步过程中客户端和服务器的会话,并提出了协议的改进意见。     

SyncML同步协议分析

SyncML是领先的开放工业标准,为使多个网络、平台和设备上的远端数据和个人信息可通用同步。SyncML支持多种传输协议,适用于在多种网络和网络化设备上传递数据。文章对SyncML规范进行分析,描述SyncML协议的关键组件,介绍7种同步类型的SyncML过程,详细分析SyncML的双向同步过程。     

On the scalability of data synchronization protocols for PDAs andmobile devices

Personal digital assistants and other mobile computing devices rely on synchronization protocols in order to maintain data consistency. These protocols operate in environments where network resources such as bandwidth, memory and processing power are limited. We examine a number of popular and representative synchronization protocols, such as Palm's HotSync, Pumatech's Intellisync and the industry-wide SyncML initiative. We investigate the scalability performance of these protocols as a function of data and network sizes and compare them to a novel synchronization approach, CPISync, which addresses some of their scalability concerns. The conclusions of this survey are intended to provide guidance for handling scalability issues in synchronizing data on large, heterogeneous, tetherless networks     

基于SyncML协议的中间件同步体系结构研究

在一个复杂的异构数据环境中如何对各种数据资源进行有效的同步是一个很有意义的课题。这里在SyncML协议的基本框架之上,借助中间件的思想,提出进行异构数据源进行同步的系统结构,最终实现Sync池服务器的数据同步工作。     

移动终端数据同步协议研究

作为移动因特网的一种重要的应用，数据同步可以使人们能够使用各种各样的无线或者移动终端设备处理和存储各种个人数据，像电话号码，个人记事本，会议信息以及进行移动设备之间的信息交换和数据同步，国际上由SyncML发起组制定的SyncML同步协议已经成为WAP2.0的一个标准应用，在SyncML所支持的有限的几个文本数据类型基础上，本文利用XML语音定义了一种全新的数据类型，它包含了图像，声音等SyncML没有定义的多媒体数据类型，从而大大丰富了SyncML的数据类型。     

SyncML数据同步协议的核心模块实现

概述SyncML的现状与框架，并重点探讨了SyncML同步过程的几个难点问题。根据SyncML RTK分析该协议实现的核心细节，利用代码剖析找到XML消息在核心模块中的工作方式及流转模式。     

Distributed slot synchronization (DSS): a network-wide slotsynchronization technique for packet-switched optical networks

Distributed slot synchronization (DSS) is a network-wide packet synchronization technique which coordinates node transmissions so that packets arrive aligned to one another at a reference point in the network, independent of propagation delays. DSS was developed for use in the contention resolution with delay-lines (CORD) project, a DARPA-funded 2.5 Gb/s/λ, wavelength division multiplexer (WDM) optical packet-switched network testbed. In this implementation, it was experimentally demonstrated that the DSS system, operating with 80 MHz control logic, achieves a packet arrival jitter of less than 13 ns with 12 km node spacings. DSS was also shown to be robust against noise and node failure or fiber breaks. The technique is data rate and format independent and can be used in other star, extended ring, or tree-and-branch network architectures for metropolitan area network (MAN) and access applications     

基于蓝牙技术的数据同步的实现

为某车型设计了一款蓝牙信息娱乐设备,在实现免提通话的同时实现了对手机的电话本数据的同步,介绍了PBAP、SyncML、AT命令、OPP4种下载电话本的方式,通过对协议和下载过程的分析与实验,提高了下载速度;介绍了2种形式的电话本数据的解析方法,通过对不同手机电话本数据形式的分析,进行兼容性设计,保证了解析的准确性;实验结果表明可以实现对大部分手机的电话本同步功能。     

Wavelet-based Burst Event Detection and Localization in Water Distribution Systems

In this paper we present techniques for detecting and locating transient pipe burst events in water distribution systems. The proposed method uses multiscale wavelet analysis of high rate pressure data recorded to detect transient events. Both wavelet coefficients and Lipschitz exponents provide additional information about the nature of the signal feature detected and can be used for feature classification. A local search method is proposed to estimate accurately the arrival time of the pressure transient associated with a pipe burst event. We also propose a graph-based localization algorithm which uses the arrival times of the pressure transient at different measurement points within the water distribution system to determine the actual location (or source) of the pipe burst. The detection and localization performance of these algorithms is validated through leak-off experiments performed on the WaterWiSe@SG wireless sensor network test bed, deployed on the drinking water distribution system in Singapore. Based on these experiments, the average localization error is 37.5 m. We also present a systematic analysis of the sources of localization error and show that even with significant errors in wave speed estimation and time synchronization the localization error is around 56 m.     

Frame and carrier frequency synchronization algorithm for wireless body area network

A wireless body area network (WBAN) is a radio‐frequency‐based wireless communication technology that consists of a number of different sensor and actuator nodes interconnected with a body gateway. Considering the constrained resources in WBAN devices, simple and noise‐robust synchronization algorithms are required. Frame synchronization and frequency offset estimation are extremely important in the design of a robust WBAN receiver. In this paper, a detection strategy such as frame synchronization and frequency estimation is described in the WBAN system, which can improve the receiver performance. In doing so, algorithms are designed or chosen for the frame detection, carrier frequency offset synchronization, and joint fine‐time and phase‐offset estimation by exploiting the spike‐like property of the physical layer convergence protocol preamble and the frame structure in the WBAN system. The performance of the WBAN synchronization receiver is verified by computer simulation. Copyright © 2015 John Wiley & Sons, Ltd.     

Syxaw: Data Synchronization Middleware for the Mobile Web

In this paper, we present a middleware for synchronization of opaque and structured data in a mobile and resource-constrained environment. The presented Syxaw (Synchronizer with XML-awareness) system distinguishes itself from related proposals in that it interoperates transparently with resources on the World Wide Web, and by exhibiting a model of synchronization that is both easy to understand and well suited for weak devices in a mobile and ubiquitous environment. We demonstrate the feasibility of the proposed system by considering several usage scenarios, including working on the Web and collaborative XML editing. We consider system performance on a mobile wireless device, and examine the impact of different optimization techniques to the performance. According to our analysis, Web interoperability suggests that the data share model be kept simple and conservative, and that moving functionality onto the client is advantageous. We find that the techniques of operation bundling and concurrent use of network downlink and uplink improve network utilization, but that achieving full bandwidth usage with a weak client is challenging in practice.     

一种基于多天线簇的新型LTE室内定位系统

随着移动互联网业务的迅速发展,位置服务需求越来越多样化,定位技术也变得越来越重要.LTE(long term evolution)室内蜂窝网络可以解决GPS(global positioning system)信号无法进入室内的问题,从而提供高精度的位置服务.LTE室内定位需要不同基站之间进行精确同步,这给室内网络部署带来了新的挑战.针对上述问题,提出了一种基于多天线簇的LTE新型无线定位系统,通过上行探测参考信号(sounding referencesignal,SRS)获取信号到达时间差(time difference of arrival,TDOA).该方法不需要簇间同步,可有效降低网络部署难度.其次,针对此系统设计了一种新的TDOA定位算法,可支持灵活的天线簇配置.最后,通过仿真及实验验证了该定位系统及算法的有效性,实验结果表明可实现米级室内定位精度.     

基于LXI总线的数据采集系统数据同步方法研究

对于大型的航空发动机数据采集系统而言,需要采集的信号众多.其不仅仅是不同设备信号的简单叠加,还要求不同设备信号间具有更高精度数据同步能力.LXI总线是新一代的仪器总线,其基于开放的工业网络标准,具有分布式的架构、高速的数据传输、高精度的系统同步等优势.某型航空发动机数据采集系统基于LXI总线设备进行设计和组建,充分利用了LXI总线的优点,有效解决了大型数据采集系统数据同步的问题,提高了系统的精度和测试效率.     

Power allocation in wireless asynchronous localization networks

Wireless localization systems based on determination of signal runtime, such as time of arrival and time difference of arrival, are of great importance for a variety of applications. In many cases, synchronization of the clocks of the agent nodes to those of the network nodes (anchors) has to be performed together with the localization. The current paper investigates the fundamental accuracy limits of such a joint localization/synchronization. In particular, we analyze the impact of allocating power to the different anchor nodes and optimize this power allocation to maximize accuracy. Optimal trade‐offs between localization and synchronization can be drawn according to the presented frameworks. Simulation results confirm the importance of proper power allocation; known special cases (time difference of arrival localization, localization with already‐synchronized clocks) are recovered from our general solution. Copyright © 2016 John Wiley & Sons, Ltd.     

On the characteristics of queueing and scheduling at encoding nodes for network coding

Synchronization can greatly influence the performance of network coding. In this paper, we shall investigate the synchronization issue based on the use of queueing theory. We shall first propose a queueing model, referred to as the classic model, to investigate the characteristics of the encoding process. It will be proved that given the packet arrival processes are stationary, i.e. the distribution of the arrival processes does not depend on time, and obey independently and identically Poisson distribution and that the encoding time is exponentially distributed, the output flow will be an asymptotically Poisson flow with the same parameter. Through simulation we shall show that the network is sensitive to the arrival rate of input flows and becomes unstable with the input queue size increasing to infinity. This indicates that the classic coding scheme would impose strict requirements on synchronization over the whole network. In order to address this, we shall propose a combined opportunistic scheduling and encoding (COSE) strategy, in which the classic coding scheme and the traditional forwarding algorithm are well integrated. Theoretical analysis and simulation will demonstrate that the COSE strategy is able to control the input queue sizes and keep the network operating in a stable state while maintaining a relatively high throughput, low blocking probability and small waiting delay under various levels of traffic load. Copyright © 2009 John Wiley & Sons, Ltd.     

LFM-MPSK雷达通信一体化系统时频联合同步技术研究

相比于传统的单一的雷达或通信设备,雷达通信一体化系统具有易集成、小型化、高谱效等优势,其中基于线性调频的一体化信号的系统方案应用广泛。在一体化系统通信功能实现方案中,传统的同步技术会降低通信速率。针对这一问题,设计了一种包含两类线性调频载波的一体化信号,并利用线性调频良好的自相关特性,提出了一种基于Costas环的时间和载波频率联合同步技术。在该技术中,首先设计了基于线性调频的Costas环结构,实现对两类调频载波的跟踪,然后根据两类载波的频率信息反演出通信时延和载波频偏。仿真结果表明,该同步技术在不影响通信效率及雷达性能的情况下,可实现一体化信号的时频联合同步,且误码率与传统同步技术的性能相当。      

ANT-on-YARDS: FPGA/MPU hybrid architecture for telecommunicationdata processing

This paper presents a novel system architecture that combines tightly coupled field programmable gate arrays (FPGA's) and a microprocessing unit (MPU) that we have developed. This system architecture comprises three main programmable devices which yield high flexibility. These devices are a reduced instruction set computer (RISC)-type MPU with memories, programmable interconnection devices, and FPGA's. This system supports various styles of coupling between the FPGA's and the MPU which makes several data processing operations more effective. Furthermore, we indicate the most suitable applications for the system. They are telecommunication data processes involving complex protocol operations and network control algorithms. In this paper, two applications of the system are given. One is for operation, administration, and management (OAM) cell processing on an asynchronous transfer mode (ATM) network. The other is a dynamic remote reconfiguration protocol that enables the functions of the transport data processing system to be updated or changed on-line     

RAPS: a precision‐adaptive protocol towards improved data fidelity in wireless sensor networks

Achieving high data quality and efficient network resource utilization is two major design objectives of wireless sensor networks (WSNs). However, these two objectives are often conflictive. By allowing sensors to report sampled data at high rates, fine‐grained data quality can be obtained. However, the limited resources of a WSN make it difficult to support very high traffic rate. Therefore, the capability of adaptively adjusting sensor nodes' traffic‐generating rates on the basis of the availability of network resources and application requirements is critical. This issue has attracted much attention recently, and some work has been carried out. To achieve high data quality and improved utilization of network resources, in this paper, we propose rate‐based adaptive precision setting (RAPS) protocol, which works in a way that each sensor can adaptively adjust its traffic‐generating rate on the basis of the current network resources availability and application requirements. RAPS introduces the following two key factors into its design: application's precision requirement and packet arrival rate. Analytical and simulation results show that RAPS can achieve improved data quality while reducing packet delivery latency. Copyright © 2012 John Wiley & Sons, Ltd.     

Short-range cognitive radio network: system architecture and MAC protocol for coexistence with legacy WLAN

To increase possible data transmission rate and to provide non-primary user’s desired throughput in short-range communications, in this paper we propose new cognitive radio (CR) network architecture with the coexistence with the legacy IEEE 802.11 WLAN. The legacy WLAN ISM band channel is mostly used for common control channel for cognitive operation on the licensed bands to manage CR devices when they join the network and to announce the utilization of the licensed band or primary system appearance on the current used channels. The proposed CR-WLAN MAC protocol is designed to accommodate new CR related features in the proposed network architecture and it has backward compatibility to the legacy WLAN system: (1) Network entry procedure is modified to inform CR users the current licensed band status and to manage CR user group separately by AP; (2) During the operation, two types of CR beacon multicasting mechanisms are proposed, CR beacons help CR users to decide its service change or spectrum handover and to immediately evacuate from the current used channel when primary signal is detected, (3) When the CR user need to change the serving CR AP, not only the beacon frame body of neighbor APs but also the licensed and unlicensed band status is delivered to CR node to search the target CR-WLAN AP fast and (4) A new type of hidden node problem is introduced that focuses on possible signal collisions between incumbent devices and cognitive radio CR-WLAN devices, and a simple and efficient sensing information exchange mechanism between neighbor APs is proposed. The simulation results show that the proposed CR system can provide reliable protection to primary systems, as well as efficient utilization of given licensed spectrum resources, in which the network throughput can be greatly enhanced.     

Robust Synchronization of Absolute and Difference Clocks Over Networks

We present a detailed re-examination of the problem of inexpensive yet accurate clock synchronization for networked devices. Based on an empirically validated, parsimonious abstraction of the CPU oscillator as a timing source, accessible via the TSC register in popular PC architectures, we build on the key observation that the measurement of time differences, and absolute time, requires separate clocks, both at a conceptual level and practically, with distinct algorithmic, robustness, and accuracy characteristics. Combined with round-trip time based filtering of network delays between the host and the remote time server, we define robust algorithms for the synchronization of the absolute and difference TSCclocks over a network. We demonstrate the effectiveness of the principles, and algorithms using months of real data collected using multiple servers. We give detailed performance results for a full implementation running live and unsupervised under numerous scenarios, which show very high reliability, and accuracy approaching fundamental limits due to host system noise. Our synchronization algorithms are inherently robust to many factors including packet loss, server outages, route changes, and network congestion.