WDM-PON光接入网技术研究

介绍了WDM-PON系统的基本原理及技术优势,重点分析和探讨了其中所涉及到的关键技术,最后分析了WDM-PON的应用前景。     

Pinwheel broadcast paradigm in supporting energy‐saving mobile devices

Because of the limited bandwidth and restricted number of channels in the wireless access environment, the broadcast paradigm has become an important technique for accessing messages. Energy saving is an important issue in the mobile computing environment. In this paper, we propose a multichannel broadcast paradigm that constructs the broadcast channels according to the access frequency of each type of message in order to save energy in mobile devices (MDs). The pinwheel scheduling algorithm (PSA) presented in this paper is used to organize all types of messages in the broadcast channels in the most symmetrical distribution in order to reduce both the tuning time and the access time. The performance of the proposed mechanism is analyzed, and the improvement over existing methods is demonstrated numerically. The results show that the proposed mechanism is capable of improving both the tuning time and the access time due to the presence of skewness in the access distribution among the disseminated messages. When the number of message types increases, both the tuning time and the access time can be further improved as long as a small number of broadcast channels are added. Copyright © 2009 John Wiley & Sons, Ltd.     

A Polynomial Complexity Optimal Multiuser Detection Algorithm Based on Monotonicity Properties

An optimal multiuser detection algorithm with a computational complexity of O(K log K) is proposed for the class of linear multiple‐access systems which have constant cross‐correlation values. Here the optimal multiuser detection is implemented by searching for a monotone sequence with maximum likelihood, under the ranking of sufficient statistics. The proposed algorithm is intuitive and concise. It is carried out in just two steps, and at each step only one kind of operation is performed. Also, the proposed algorithm can be extended to more complex systems having more than a single cross‐correlation value.     

一种空时盲自适应RAKE接收机

多址干扰是直扩码分多址系统中的一个主要问题.多用户检测技术和阵列天线已成为解决这一问题的两种主要方法,将这两种方法结合起来的空时处理能大大提高系统的容量和性能.本文提出了一种空时盲自适应RAKE接收机.研究结果表明,该接收机具有较强的抑制多址干扰和克服"远-近"效应的能力,且能快速收敛.     

Broadband Wireless Access Solutions - Progressive Challenges and Potential Valueof Next Generation Mobile Networks

The growth in mobile communication will accelerate over the next years. Today most of the mobile subscribers use cellular services only. But this will change in the near future towards broadband wireless access services like WiFi and WiMAX. This paper describes a fundamental overview of the broadband wireless access technologies and outlines the market view, major trends and introduces OFDM technologies. New developments for integration of broadband wireless access into the operators' infrastructure are also discussed.     

Hierarchical micro-mobility management in high-speed multihop access networks

1 Introduction A wireless multihop network or Ad-hoc network [1, 2] is a network of independent mobile hosts without any network infrastructure or connection to base stations. In many application areas, however, Internet connectivity and access to service…     

基于访问网格的沉浸式可视化协同设计系统的设计实现

为了处理协同设计中多个分布、异构的组织和个人的复杂数据交互,利用沉浸式可视化技术提供高质量的无间距协作。通过对访问网格进行分析,提出基于访问网格的沉浸式可视化协同设计系统框架,研究系统实现及通过网格服务进行任务智能分解的关键技术。系统实现表明,比传统基于Internet的协同设计系统具有更高的设计效率和更好的设计效果。     

计算机网络系统安全漏洞的研究

为了从根本上解决计算机网络中的漏洞问题,从漏洞产生的原因出发进行研究,针对其中的一类漏洞提出了解决方案:即通过对客户端系统中的软件进行特殊的扫描加密方法,使攻击者不能绕过其访问控制,从而避免了访问验证错误引起的漏洞。最后,指出从漏洞产生的原因来解决系统安全漏洞问题必将是漏洞研究的发展趋势。     

基于Social Cognition粒子群算法多用户检测

最优多用户检测方法具有最优性能,但复杂度高,利用优化算法求解可以降低实现复杂度。粒子群算法是一种简单有效的新型群智能优化算法,研究了一种Socialcognition模型简化粒子群算法,并应用于大用户量CDMA多用户检测问题,主要考虑降低算法复杂度,提高算法的实现效率。分析及仿真表明该方法在系统用户数量较大时具有较好性能。     

INTELSAT的新业务—DAMA系统

本文介绍国际通信卫星组织最新推出的ＤＡＭＡ系统，以及作为系统技术标准制定基础的ＴＥＳ系统，并对系统的网络结构、设备组成和性能作了较全面的描述。