Service Scheduling of Vehicle-Roadside Data Access

As vehicular networks become popular, more and more people want to access data from their vehicles. When many vehicles want to access data through a roadside unit, service scheduling becomes an important issue. In this paper, we identify some challenges in vehicle-roadside data access. As vehicles move pretty fast, the requests should be served quickly. Also, vehicles may upload data to the roadside unit, and hence the download and upload requests compete for the same bandwidth. To address these challenges, we propose several service scheduling schemes. We first propose a basic scheduling scheme called $\mathcal{D*S}$ to consider both service deadline and data size. We then enhance it by using a single broadcast to serve multiple requests. Finally, we identify the effects of upload requests on data quality, and propose a Two-Step scheduling scheme to provide a balance between serving download and update requests. Simulation results show that the Two-Step scheduling scheme outperforms other scheduling schemes.     

云计算的服务安全体系结构和访问控制模型

Security is a key problem for the development of Cloud Computing. A common service security architecture is a basic abstract to support security research work. The authorization ability in the service security faces more complex and variable users and environment. Based on the multidimensional views , the service security architecture is described on three dimensions of service security requirement integrating security attributes and service layers . An attribute-based dynamic access control model is presented to detail the relationships among subjects , objects , roles , attributes , context and extra factors further. The model uses dynamic control policies to support the multiple roles and flexible authority. At last, access control and policies execution mechanism were studied as the implementation suggestion.     

Packet Voice on a Local Area Network with Round Robin Service

In this paper, we propose a combined voice/data protocol suitable for multiple access broadcast networks that provide round robin service to the stations. Such networks are well suited to the integration of voice and data since they guarantee bounded delay and provide high utilization even for high bandwidth channels. Using one such network proposal-namely Expressnet-as a representative scheme, we examine the characteristics of the service that voice traffic experiences under the voice/data protocol. We show that the access protocol is able to utilize the channel efficiently to support a large population of voice sources while maintaining low packet delay and guaranteeing some prespecified minimum bandwidth for data traffic. In addition, we show the advantages of silence suppression, i.e., discarding speech that constitutes silent periods, and we examine the cost of overloading the network in terms of the amount of speech discarded.     

一种基于Web Service的虚拟化目录服务

给出了一种虚拟化目录服务结构,利用轻量级目录访问协议构建分布式目录服务,形成一体化的逻辑视图,通过访问控制策略在保持信息节点自治性的同时提供安全保障。文中基于Web Service封装目录服务,提供目录查询和管理的API,实现了跨平台和松耦合的资源访问方式。     

TDD-CDMA系统中基于业务活动因子的功率控制算法

功率控制技术是CDMA系统克服远近效应、降低多址干扰的一项关键技术.TDD-CDMA系统所要提供的网络业务更多的是基于突发模式的通信,包括各种速率的实时和非实时业务.分析了突发模式业务的统计特性,根据马尔可夫调制贝努利过程,提出了一种基于业务活动因子的功率控制算法,并给出了相应的功率控制模型.通过建立功能模型,验证和评估了提出的功率控制算法.仿真结果表明,这一新的功率控制算法能够更准确地估计干扰信号强度,加快功率控制的收敛,从而提高能量效率和系统容量.     

A Modular Access Control Service for Supporting Application-Specific Policies

Access control services integrated in current middleware technologies fall short whenever application-specific access control policies must be enforced. As a consequence, developers embed access control logic in the code, resulting in an unmaintainable access control enforcement. The authors use aspect-oriented software development techniques to better separate application logic and access control by describing the design and implementation of a modular access control service. They have implemented a prototype in CaesarJ, a research aspect-oriented programming language.     

Security-Enhanced OSGi Service Environments

Today's home and local-area network environments consist of various types of personal equipments, network devices, and corresponding services. Since such prevalent home network environments frequently deal with private and sensitive information, it is crucial to legitimately provide access control for protecting such emerging environments. As a result, the open services gateway initiative (OSGi) attempted to address this critical issue. However, the current OSGi authorization mechanism is not rigorous enough to fulfill security requirements involved in dynamic OSGi environments. In this paper, we provide a systematic way to adopt a role-based access control (RBAC) approach in OSGi environments. We demonstrate how our authorization framework can achieve important RBAC features and enhance existing primitive access control modules in OSGi service environments. Also, we describe a proof-of-concept prototype of the proposed framework to discuss the feasibility of our approach using an open source implementation of OSGi framework known as Knopflerfish.      

基于三级调制的多带OFDM-UWB多址算法

根据多带OFDM-UWB通信系统的特点，提出一种基于三级调制的多带OFDM-UWB多址算法—TSM-MA算法。该算法通过MC-CDMA、OFDMA与FHMA技术的融合，实现多种技术的优势互补，减少了多用户间的干扰，充分利用了各子载波的可用资源。为了降低接收机的复杂度，TSM-MA算法采用了二级扩频与二级跳频的机制。结果表明，TSM-MA算法的多址性能要明显优于时频多址算法的性能，可以改善系统信噪比3dB左右，并且在接收机的复杂度方面也有一定的优势。     

基于扩频与跳频的多带OFDM-UWB多址技术

根据多带OFDM-UWB通信系统的特点,提出一种基于扩频与跳频的多址技术。该多址技术将多载波码分多址和跳频多址相结合,构成一种新颖的多址技术-正交频分多址(OFDMA),实现多载波码分多址技术和跳频多址技术的优势互补,此接收机的复杂性明显小于常规时频码的多用户接收机。仿真结果表明,基于OFDMA多址技术方案的UWB系统在系统误比特率性能上优于常规时频码方案约5dB。     

韩国宽带发展现状

目前，韩国宽带网络的普及率已经跃居世界首位。这与其市场环境公平，进入自由、竞争充分，政府的大力推动，娱乐业和网络游戏的带动是分不开的，密集的居住环境也为韩国的宽带普及提供了便利。分析了韩国宽带市场的发展现状和财务状况，介绍了韩国宽带发展步骤和成功经验。     

基于IEEE 802.16a的OFDM-FDMA与OFDM-TDMA的性能比较

对于使用OFDM传输技术的多载波系统,将OFDM技术与传统的多址接入方案,FDMA和TDMA相结合,可以实现多用户OFDM系统,这样派生出两种多址接入方案:OFDM-FDMA和OFDM-TDMA。研究了这两种多址技术,并基于IEEE 802.16a协议比较了他们的性能,用Matlab语言仿真实现了这两种多址系统。仿真结果表明OFDM-FDMA系统的误比特率性能要优于OFDM-TDMA系统。     

WADA Service: An Extension of DICOM WADO Service

The Web Access to Digital Imaging and Communication in Medicine (DICOM) Persistent Objects (WADO) service is standardized as the Web extension to DICOM. This paper analyzes the operational specifications of the WADO service and extends its access capability to the whole DICOM hierarchy (patient, study, series, and object). The proposed Web Access to DICOM Archives (WADA) service, as opposed to WADO, also includes an extrainternal query mechanism and support of medical reports submission. A pilot implementation of WADA as software components and their integration into a three-tier architecture are also presented. Advanced security mechanisms are augmented to ensure communication encryption, user identification, and access restriction to data according to user roles. The proposed service is a simple approach, and can be embedded in any system managing medical images and reports. WADA can also be integrated into the Cross-Enterprise Document Sharing-Imaging (XDS-I) standard, which is considered to be the most likely future standard for medical imaging exchange.     

数字图书馆中的仓储服务系统

数字图书馆以电子格式存储海量的多媒体信息并能对这些信息进行高效的操作，如检索、提供访问接口、信息保护等。文章介绍了数字图书馆中的仓储服务系统，它提供对分布式数字对象的持久保存、安全访问和管理。仓储服务系统的基本存储单元是数字对象，整个系统就是为了存储、访问、管理数字对象而设计的。     

SDMA系统FD方案阻塞率的仿真

现代无线移动通信系统广泛考虑采用空分多址（SDMA）多址接入技术来提高系统容量。比如在频分复用（FDMA）时分复用（TDMA）,码分复用（CDMA）。分析研究SDMA系统中的FD信道分配机制,给出了理论推导,并在此基础上进行了仿真。仿真结果表明：采用该机制以后,用户可以在同一时间共享同一信道。     

综合业务接入区业务承载方案

随着中国移动在全国范围内开展的综合业务接入区建设的基本完成,如何充分利用综合业务接入区资源,降低投入成本,有效地支撑业务发展,提高各接入区业务接入能力,是未来综合业务接入区发展的基本要求。本文通过对已建成的综合业务接入区承载业务诸多问题进行分析,提出了综合业务接入区内基站、WLAN、集团客户专线、家庭宽带等各类业务承载方案。     

ComUNITY的宽带业务接入解决方案

ComUNITY是美国COM21公司开发的一套以HFC为接入网的互联网数据通信系统，该系统主要包含通信头端、线缆调制解调器和网络管理软件等产品。介绍ComUNITY系统的技术原理和产品特点，并提出一种基于ComUNITY系统的宽带业务接入解决方案。采用该接入方案可以为用户提供如虚拟局域网(VLAN)、综合数据业务等各种多级付费管理服务。     

A tutorial on multiple access technologies for beyond 3G mobile networks

In this article, some fundamental technical concepts of the main multiple access schemes for wireless mobile systems are reviewed, and a path for the development of appropriate multiple access technologies for next-generation mobile networks, or so-called beyond 3G (B3G), is established. We first review the multiple access technologies in second- and third-generation wireless cellular systems from historical and technical points of view. This review is followed by a novel formulization of the multiple access schemes through mathematical expressions that could simplify the process of development of new multiple access schemes for B3G wireless cellular systems. We then list the most important features of multiple access schemes in 3G mobile systems. Finally, we conclude the article by reviewing the most promising multiple access technologies for B3G mobile cellular systems     

如何在宽带接入网中融合现有窄带业务

本文介绍了宽、窄带接入网的定义 ,在接入网中融合多种业务的必要性及其面临的难题 ,支持现有窄带业务接入的三种方式以及相关建议等。     

数据业务中公共控制信道的优化方法

近几年数据业务发展迅速,由于数据业务对GSM无线网络公共控制信道资源占用的快速增长,部分小区在业务忙时出现了公共控制信道的拥塞,从而导致该小区无线网络的寻呼性能及网络接入性能下降。湖州移动创新使用多种方法对公共控制信道进行了优化,缓解了公共控制信道的拥塞,并在高数据业务压力及高语音业务负荷之下依旧维持了较好的小区寻呼性能和网络接入性能。湖州移动现网的运营经验证明,这些优化方法是行之有效的。     

彩铃业务WWW接入系统的改进

WWW接入方式是目前彩铃业务最主要的接入方式之一。本文针对原有彩铃业务WWW接入系统中的不足,采用Struts2 MVC框架,使用Spring容器作为系统的IoC容器,并结合现有的Web新技术,重新设计和实现了彩铃业务WWW接入系统,提高了该系统的灵活性、可扩展性、可维护性、安全性等。最后采用测试工具对原有系统和改进后的系统进行了性能比较,并对本文提出的改进方案进行了讨论。