数字通信系统中一种新型差错控制方案

对当今主流数字通信系统中的差错控制技术进行了分析,并针对其不足提出了一种 新型差错控制方案。利用两条信道同时传输数字信息,传送的信息相位相反,信息中无监督 码元,在接收端利用差分技术对这两个信号进行处理。分析表明,该方案在信号的传信率、 误码率和编码效率指标上优于传统差错控制技术,且实现更为简单。     

一种基于角色和应用上下文的移动网访问控制模型

访问控制是ITU X.805中定义的电信网八个安全维度之一.分析了移动核心网中数据访问的特点,提出了一种应用于移动通信网的访问控制模型基于角色和应用上下文的访问控制模型(R-ACBAC).该模型在基于角色的访问控制模型(RBAC)基础上,引入应用上下文和限定性约束等概念,对移动网访问控制中角色和权限的分配策略、触发机制、动态迁移等内容进行了详细的定义,为移动网中数据访问的检测与控制提供了参考.     

一种语音业务固定无线接入方案

固定无线接入系统中语音业务的接入方法进行了研究,介绍了固定无线接入系统的结构,分析了当前广泛采用的V5接口的优缺点,提出了一种基于ISDN一次群速率接口的接入方案并给出了其具体实现方法。     

一种改进的数字混沌编码器

针对解码器在解码前不需要初始化,攻击者容易重构出解码器结构这一缺陷,提出 了一种新的编解码方法。改进后的解码器只有当编、解码器的初始状态相同时,解码器 才能正确地恢复出原始信息序列。仿真结果表明,改进后的混沌编解码器结构比原结构具有 更好的保密性能。     

A Conditional Role-Involved Purpose-Based Access Control Model

This paper presents a conditional role-involved purpose-based access control (CPAC) model, where users dynamically activate conditional roles in accordance with the context attributes. Based on conditional role, access permissions are assigned that represent what can be accessed for what purpose to roles under certain conditions. On the other hand, conditional purpose is applied along with allowed purpose and prohibited purpose in the model. It allows users using some data for certain purpose with conditions (for instance, Tony agrees that his income information can be used for marketing purposes by removing his name). The structure of a CPAC model is defined and investigated. Access purpose is verified in a dynamic behavior, based on user attributes, context attributes, and authorization policies. Intended purposes are dynamically associated with the requested data object during the access decision. An algorithm is developed to achieve the compliance computation between access purposes and intended purposes and is illustrated with role-based access control (RBAC). Access purpose authorization and authentication in the model are studied with the hierarchical purpose structure. The model separates authorization of access purpose from access decision that improves the flexibility of private data control.     

From the Digital Internet to the Physical Internet: A Conceptual Framework With a Stylized Network Model

Despite the increasing academic interest and financial support for the Physical Internet (PI), surprisingly little is known about its operationalization and implementation. In this paper, we suggest studying the PI on the basis of the Digital Internet (DI), which is a well‐established entity. We propose a conceptual framework for the PI network using the DI as a starting point, and find that the PI network not only needs to solve the reachability problem, that is, how to route an item from A to B, but also must confront a more complicated optimality problem, that is, how to dynamically optimize a set of additional logistics‐related metrics such as cost, emissions and time for a shipment. These last issues are less critical for the DI and handled using relatively simpler procedures. Based on our conceptual framework, we then propose a simple network model using graph theory to support the operationalization of the PI. The model covers the characteristics of the PI raised in the current literature and suggests future directions for further quantitative analyses.     

宽带数字阵列雷达相对时延测量的新方法

基于Dechirping理论,提出了一种能有效测量大时带积线性调频(LFM)脉冲信号在宽带数字 阵 列不同通道间相对时延的新方法。该方法利用了FFT算法,不仅系统所需器件简单易行,而 且测量精度与实时性较好,并能在一次测量过程中对多个通道进行同时测量。从理论角 度分析了这种测量方法的性能与特点,在此基础上确定出系统的各项参数,并提出了进一步 简化系统的方案。仿真实验结果验证了所提方法的有效性。     

一种基于CDMA/TDMA混合多址的GSM与CDMA扩容方法

提出了一种基于CDMA/TDMA混合多址的GSM与CDMA扩容方法。在发送端,通过扩频码对GSM信号进行直接序列扩频,使其多址方式由TDMA变换为CDMA/TDMA,然后与CDMA信号在空间同频传输,这样就可以解决两个系统在Um接口的兼容问题;在接收端,使用相同的扩频码对CDMA/TDMA信号进行解扩,使其多址方式由CDMA/TDMA还原为TDMA,由此可以将GSM与CDMA两种信号进行分离。文章提出了用互补码集作为多址接入码,并给出了一个时隙内GSM用户被扩频调制的具体过程。理论分析和仿真结果表明,该方法可使系统总容量扩大2倍。     

基于分布式时隙调度协议的战术互联网媒体访问控制技术

在分析现有移动无线网络TDMA时隙调度问题的基础上,根据战术互联网骨干网拓扑与业务需求,结合跳频电台的特点,提出了一种新的动态分布式TDMA时隙调度协议(DTSP),能够适应不同业务需求,支持单播、广播和组播.DTSP协议以无冲突的预留提高系统吞吐量,以渐增方式适应动态拓扑变化,动态调整的开销较小.最后,以DTSP时隙单播预留协议为例,进行了详细分析和复杂度计算.     

Context-Sensitive Access Control Model for Government Services

During the past two decades, e-government information systems have become less paper-based and more computer-based. Those information systems usually take the form of workflow systems. Due to the large social impact of e-government systems, computer security plays a pivotal role in ensuring its efficiency and effectiveness. Access control is one of the key aspects of computer security. Current access control models do not take into account the context of the system and its environment. In this article, we argue that a formal context-sensitive access control model can improve the development of e-government workflow systems and present a particular context-sensitive access control model. The subject of the article is a specification of the context-sensitive access control model for business processes (COBAC). By using a context-sensitive access control, it is possible to define more sophisticated access control policies that cannot be implemented by existing access control models. The COBAC's context is modeled using Web Ontology Language (OWL) in order to provide formal representation of context, rich representation of diverse contextual information, semantic interoperability between various context-aware systems, and a high degree of inference making. The presented model is applicable in different e-government systems, and supports the definition of access control policies for both simple and complex business processes. The model's prototype is verified by a case study on a real e-government business process—the national petty offense trial proceedings.     

Estimating Contagion on the Internet: Evidence from the Diffusion of Digital/Information Products

Even as the Internet continues to grow as a global platform for communication and commerce, the success of new value offerings on the Internet hinges on acquisition of new customers and retention of existing customers. Central to the flow of customers in and out of trial and repeat behavior in this burgeoning and dynamic environment, characterized by diversity among both producers and consumers of value offerings, is the process of social contagion—active word of mouth that flows among customers or passive observation of others. To estimate contagion on the Internet, the authors develop a trial-repeat purchase diffusion model for successive innovations in value offerings on the Internet. The model extends the state-of-the-art diffusion modeling by incorporating (i) dynamic market potential, (ii) heterogeneity among first-time triers, (iii) heterogeneity in word of mouth due to repeat buyers and non-repeaters (i.e., positive and negative word of mouth), and (iv) dynamic repeat purchase rate. The model also incorporates the influence of product characteristics, specifically source of innovation (i.e., whether the innovation is driven by environmental needs or competitive pressures) and product bundling, and competition. The authors test the model with weekly adoption data for 11 computer software products available on the shareware system, involving over 100 new versions in the period 1991–1994, and in a market whose size grows by a factor of fifty from early 1991 to late 1994. The findings clarify the role of word of mouth effects, competition, and product characteristics in fostering the diffusion process for digital information goods.     

一种新颖的无人机编队拓扑形成与信道接入机制

针对全球导航卫星系统（Global Navigation Satellite System,GNSS）高精度相对定位的无人机编队飞行应用中的信息交互与通信时延问题,首先优化设计了编队飞行网络拓扑,实现所有成员的信息交互且通信代价最小;其次,基于优化设计的网络,提出一种新的通信信道接入机制;最后对16机编队飞行场景进行了仿真分析,评估通信网络及相对定位性能。结果表明,编队成员端到端通信时延小于20 ms,且当通信与载波相位差分处理的总时延小于相对位置感知时间间隔时,相对位置感知精度可达到亚分米级,且感知误差与时延和载体运动状态相关。     

一种新的认知无线电非合作功率控制博弈算法

当认知无线电网络以"衬底式"(Underlay)的方式与主用户网络共享频谱时,需要对认知用户进行功率控制,以确保认知用户在不干扰主用户的前提下,公平地共享认知频谱资源。利用博弈分析的方法,设计了一个基于链路增益因子的代价函数,并据此提出了一种新的非合作功率控制博弈算法。仿真结果表明,该算法的均衡结果既改善了用户的帕累托(Pareto)性能,又提高了链路增益较差的用户的吞吐量,实现了网络资源的平等共享。     

The Hierarchy of Internet Communication Effects: A New Paradigm for Understanding Internet Promotion

ABSTRACT

The applicability of the traditional marketing models to online marketplaces has been of great interest since the advent of the Internet. This study examines the applicability of the Hierarchy of Communication Effects model to the online auction environment through the use of proprietary archival data. The results provide support for a new model, which we call the Hierarchy of Internet Communications Effects, which is applicable to online environments. The Hierarchy of Internet Communications Effects is analogous to other hierarchical effects models from consumer behavior literature known as the learning hierarchies. We provide suggestions to promote products or services at different stages in the Hierarchy of Internet Communications Effects; several implications and limitations are discussed, and future research is suggested.     

E-Business Method: A Cyclical-Model for Internet Commerce Development

ABSTRACT

This paper presents a methodology for designing and deploying electronic enterprises–a step beyond intuitive or rule-based approaches. As a starting point, the paper presents a cyclical-model consisting of three e-business development phases: conceptualization, simulation, and implementation. Since an e-business “idea” rarely springs forth complete and ready to go, realizing the idea–that is, turning it into a commercial product, system, process, or profitable enterprise–requires business development. Business development requires analysis of the potential organizational structures, IT architectures, HR policies and procedures, strategies, market niche, partnership agreements, and so on, until a satisfactory enterprise design is found. Such consideration and experimentation can be done mentally (intuitively), or by drawing on a napkin (informally), or more logically using strategic and marketing analysis, revenue/cost/asset/operational business models, computer simulations, and other quantitative and qualitative management practices and techniques. In any case, only rarely is the result of the first development effort completely satisfactory, perhaps the business system or process will be too difficult to develop, too complex, or too costly to implement, maintain, or sell. So, once again the business idea goes into the cycle of developing, testing, redeveloping, implementing, and re-testing. Succinctly, the methodology advocated in this paper provides a framework for guiding the e-business development process.     

Designing Effective Websites: The Moderating Role of User Internet Experience

ABSTRACT

The objective of this study was to analyze the effectiveness of various aspects relating to execution of a Website: Presentation format, quantity and type of content. We developed experimental Websites and we found that in high-involvement context this effectiveness is not influenced as much by the format of presentation of the Website as by the quantity and type of content offered. The extension of the Website content generates more favorable, affective and behavioral responses only when such extension has an informative nature. Moreover, we found evidence of the moderating role of the individual's Web experience in the advertising persuasion process. Therefore, the results of this investigation can provide recommendations to the organizations on how to create effective Websites.     

Experts and Amateurs: The Role of Experience in Internet Auctions

The use of auctions as a pricing mechanism has grown dramatically over the last few years. The introduction of electronic auctions has significantly widened the pool of consumers who participate in auctions and increased the number of companies attempting to sell their products in an auction format. Previous empirical research on auctions has focused almost exclusively on the behavior of professional bidders in high stakes common value auctions or the behavior of students in laboratory experiments. We collect data on a large number of electronic auctions, across four product categories, to explore the behavior of consumers bidding in a real marketplace. In particular, we focus on the role experience plays in their bidding behavior to uncover whether consumer learning drives the bidding process towards outcomes described in the theoretical literature on auctions. We find that experience does indeed lead to behavior which is more consistent with theory although the proportion of experienced bidders who behave in a manner inconsistent with theory remains quite large.     

一种利用短时DFT分析实现全数字2DPSK接收机解调的新算法

本文提出了一种简单而实用的利用短时DFT（ST-DFT）分析实现全数字2DPSK接收机的解调算法。该算法对由多谱勒效应引起的时变频率漂移具有鲁棒性。由于该算法是通过检测在载频处的瞬时能量谱的跳变来实现2DPSK信号的解调，所以该算法不需要进行专门的载波相位恢复、符号定时，且具有较好的抗噪性能，实现起来简单。     

基于 TCP/IP 的远程数字监控系统

根据美国国家经济研究局（NBER）的最新宣布,美国经济自2001年3月已经进入衰退。本文认为,美国此次衰退是难以避免的,这是经济周期的必然规律,由于此前虚拟经济与实体经济的发展脱离,形成泡沫,那些过剩的资本终究会退出,于是造成人们心理预期的过度反应,消费和投资需求出现大幅萎缩,而恐怖袭击事件则加速了衰退的进程。对中国而言,美国衰退的影响是利弊兼有,主要表现在出口、引资、经济格局等方面。