基于上下文感知的移动协同标绘模型

针对移动计算环境下的协同标绘问题，构建了基于上下文感知的移动协同标绘模型MCPM-CA。从移动协同的特征出发，采用上下文感知技术来捕获移动协同标绘中的多种上下文信息，并对其进行上下文语义描述。然后，通过上下文上的推理得出标绘状态的变迁规则。最后给出MCPM-CA模型的应用实例。目前。该模型已应用于移动协同服务支撑平台，结果表明该模型可行、有效，有力了支撑了移动协同标绘的实现。     

移动IP中改进TCP性能的几点建议

介绍了TCP性能的控制机制,分析了移动IP中的切换对TCP性能的影响,提出了在移动IP中改进TCP性能的方法。     

Piecewise Network Awareness Service for Wireless/Mobile Pervasive Computing

This paper presents a piecewise framework for network awareness service (NAS) for wireless/mobile pervasive computing. We investigate how piecewise consideration of wired and wireless elements of the framework architecture benefits service advertisement and discovery and network-awareness techniques. We also discuss scalability of the NAS framework with respect to platform computing capabilities. The framework is suitable for a wide range of computing devices, from powerful ones with multi-tasking operating systems (OS) to small ones with lightweight OS. Case studies applying the NAS framework to sensor monitoring in home networks and data streaming in pervasive multimedia computing are presented. The analytical results on the performance of the NAS framework in these case studies show that it has significant advantages over traditional network-awareness frameworks in terms of reducing wireless bandwidth consumption and saving battery energy of mobile devices.     

Improving the Quality of Mobile Learning Services

Wireless Personal Communications - The quality of services (QoS) has a key role to improve the performances of the collaborative mobile learning. However, many factors can limit it such as the...     

CSCW系统中的协作支持

设计ＣＳＣＷ系统结构的关键问题是如何提供有效的协作支持本文提出了一个分层的协作支持方案，此方案包括三层：面向系统，面向应用以及面向共享对象的协作支持，相应于这一方案，本文还提出了一个可容纳多种协同应用，并基于公共平台的ＣＳＣＷ系统体系结构，通过对言之有理三层协作支持的实现，多媒体桌面会议系统ＴＨ－ＭＤＣＳ可借助视频，音频，图象，图形，文本等多种媒体形式方便有效地支持分散在各地汪同专业领域的小组成员     

基于情景感知的低交互移动双因素认证系统

针对传统双因素认证缺乏可用性的问题,本文提出了一种基于情景感知的低交互移动双因素认证系统.用户通过本系统登录网站时,除输入用户名和口令外,只需点击令牌程序的认证键即可完成认证,平均登录时间不超过5秒.同其它可用性加强的移动双因素认证系统相比,本系统能够抵抗同一环境下的攻击者,而且支持用户手机浏览器进行网站登录.最终安全分析和实验结果证实了本方法的有效性.     

移动计算中断连操作性能的改善方法

在移动计算环境中,如果移动客户机与固定主机的读/写、写/写冲突机率很高,则暂态事务在固定主机上成功提交的概率就很低,大量的暂态事务就会夭折,这将浪费大量的服务器资源和通信资源,降低了整个系统的性能。为了提高暂态事务重提交的成功概率,我们提出按概率提交暂态事务的方法。该方法在冲突频率非常高的场合,能够节省移动客户机的传送开销、减轻固定主机的负担,提高事务的吞吐量。     

A Cross-Layer Approach for Improving TCP Performance in Mobile Environments

Network-layer mobility protocols have been developed to keep continuous connectivity for mobile hosts while transparent to the higher layers. However, Due to its distinct characteristics of different from traditional TCP/IP environment, mobility poses substantial impacts on TCP performance in mobile environments. This paper proposes a new cross-layer approach, by introducing a mobility detection element in the network layer which interacts with the transport layer to optimize TCP operations. As changes are only made to the endpoints, this approach preserves the end-to-end semantics of TCP. Different from most exiting works, which utilize either transport or network layer alone without much cross-layer cooperation, our approach allows the use of mobility information in TCP. We analytically compare this approach against existing approaches and show that our approach outperforms prior approaches in terms of effective data resumption time. Through performance simulations, our approach demonstrates that it can effectively improve TCP performance in Mobile IPv6-based mobile environments.     

On Improving the Performance of Cache Invalidation in Mobile Environments

Many cache management schemes designed for mobile environments are based on invalidation reports (IRs). However, IR-based approach suffers from long query latency and it cannot efficiently utilize the broadcast bandwidth. In this paper, we propose techniques to address these problems. First, by replicating a small fraction of the essential information related to cache invalidation, the query latency can be reduced. Then, we propose techniques to efficiently utilize the broadcast bandwidth based on counters associated with each data item. Novel techniques are designed to maintain the accuracy of the counter in case of server failures, client failures, and disconnections. Extensive simulations are provided and used to evaluate the proposed methodology. Compared to previous IR-based algorithms, the proposed solution can significantly reduce the query latency, improve the bandwidth utilization, and effectively deal with disconnections and failures.     

Improving WTLS Security for WAP Based Mobile e-Commerce

In recent years, WAP has been gaining increasing popularity as a platform for mobile e-commerce; its security has thus become an important issue. In this paper, we focus primarily on improving WTLS, a sub-protocol of WAP, to achieve enhanced WAP security. We propose using an Anonymous Client Authentication (ACA) scheme, which can be applied in general to most Public Key Infrastructure based mobile e-commerce applications, to be incorporated into WTLS to provide client anonymity in WAP. Further, in order to support the desired security feature forward secrecy, and to resist various attacks which could hardly be coped with by the original WTLS, we exploit Elliptic Curve Cryptography (ECC) for session key establishment. The proposed protocol has been shown able to outperform not only the original WTLS protocol, but also the published improved WTLS protocols in terms of computation cost and communication bandwidth. Besides, the proposed ACA scheme can also be exploited in other internet and wireless network based platforms.     

支持CSCW的多数据库技术

计算机支持的协同工作（CSCWComputerSupportedCooperativeWork）所涉及的应用离不开数据库，而许多数据库是在此之前早已存在的。已有数据库具有多态性、分布性和自治性，为了实现这些数据库之间的共享，文章提出用多数据库的技术来扩展早些时期的分布式数据库技术，并对多数据库的关键技术：多数据库的结构模式、公共数据模型、多数据库查询语言、多数据库事务管理和多数据库完整性约束等加以讨论。     

HMIPv6协议中提高移动业务QoS的策略分析

提出了在HMIPv6中将转交地址池策略与简化资源预留协议策略相结合的改进策略。通过对标准HMIPv6改进前后所产生的切换时延对比分析,得出了有关的重要结论。     

移动话务网管系统的改进方案

为了中国移动"集中监控、集中维护、集中管理"的集中化运维模式可靠实施,本文提出了在现运行网管平台基础上,采取话务网管系统硬软件双备份技术改造方案.     

移动网络寻呼成功率的分析与提高

寻呼成功率是评价一个移动网络优劣的重要指标之一,也是目前中国三大运营商KPI考评指标体系的重要组成部分。寻呼成功率的高低直接影响着手机做被叫的接通率,同时也影响着用户的感知。笔者通过在交换侧对寻呼的流程进行分析,寻找改善寻呼成功率的各方面因素,从而解决移动通信寻呼成功率低的问题,以便提高移动通信质量、进而提高用户满意度。     

一种改进的CSCW组播通信路由算法

组播通信路由算法是CSCW重要研究领域。文章提出了剪枝型改进算法BCSPST，在一定程度上避免了原算法分枝节点分组复制集中而易发生负载过重或拥塞的缺点，同时证明了BCSPST算法的时间复杂度。     

改善移动通信高楼通话质量的方案

通过对无线网络参数、网络结构、天线馈线参数的适当调整等方法以及采用微蜂窝和多层网设计等技术 ,能有效地抑制无线干扰 ,改善移动通信高楼通话的质量。     

ATSC DTV的移动接收技术

文章从改进ATSC标准、引进自适应阵列天线技术和提出快速均衡算法三方面论述了提高ATSC DTV移动接收性能的方法.通过仿真验证了这些方法的有效性.     

Distributed PIN Verification Scheme for Improving Security of Mobile Devices

The main driving force for the rapid acceptance rate of small sized mobile devices is the capability to perform e-commerce transactions at any time and at any place, especially while on the move. There are, however, also weaknesses of this type of e-commerce, often called mobile e-commerce, or m-commerce. Due to their small size and easy portability mobile devices can easily be lost or stolen. Whereas the economic values and privacy threats protected with Personal Identification Numbers (PIN) are not particularly high for normal voice-enabled mobile phones, this is not true any more when phones have developed to Personal Trusted Devices (PTDs). Still, PINs are used also in this new context for authorization and identification purposes. PINs are currently used both for protection of the devices and for authentication, as well as authorization of the users. It is commonly recognized that not many techniques of storing the PINs into the memory of the device or on the SIM card are safe. Even less sophisticated thieves might uncover the PIN inside the stolen mobile devices and for sophisticated thieves uncovering the PIN stored safely might be possible. In this paper we propose a new scheme to cope with the problem of uncovering the PIN that reduces the risks of m-commerce. The basic idea is that instead of storing the entire PIN digits (or some hash value) in the mobile device, we store part of the PIN in a remote machine in the network. The PIN verification then involves both the mobile device and the remote machine, which must verify their respective parts of the PIN. Also, the improvements of the security over the existing schemes are shown using a probabilistic model. In the best case, where the probability of discovering the PIN irrespective of the storage scheme is negligible in relation to directly uncovering it, the increase in security is over 1000%.