Fast handoff with reducing waste rate approach for wireless resources management in UMTS mobile networks

3G Wideband CDMA systems adopt the Orthogonal Variable Spreading Factor code tree as the channelization codes management for achieving high data rate transmission in personal multimedia communications. It assigns a single channelization code for each accepted connection. Nevertheless, it wastes the system capacity when the required rate is not powers of two of the basic rate. One good solution is to assign multiple codes for each accepted connection but it causes two inevitable drawbacks: long handoff delay and new call setup delay due to high complexity of processing with multiple channelization codes, and high cost of using more number of rake combiners. Especially, long handoff delay may result in more call dropping probability and higher Grade of Service, which will degrade significantly the utilization and revenue of the 3G cellular systems. Therefore, we propose herein an adaptive efficient codes determination algorithm based on the Markov Decision Process analysis approach to reduce the waste rate and reassignments significantly while providing fast handoff. Numerical results demonstrate that the proposed approach yields several advantages, including the lowest GOS, the least waste rate, and the least number of reassignments. Meanwhile, the optimal number of rake combiners is also analyzed in this paper. This research was supported in part by the National Science Council of Taiwan, ROC, under contract NSC-93-2213-E-324-018.     

在ad hoc网络中一种新的节能路由切换模型

提出了一种基于能量消耗的路由切换模型(ERHM),它在路由维护中利用切换技术来使路由的能量消耗最小.仿真结果表明采用切换技术的ERHM模型的能量节省量要比不采用切换技术节约1.5～7.5倍,且节点的移动性越大,能量节约越多.     

基于CPX8216硬件平台的GPRS板间切换的实现

GPRS全称通用分组无线业务,它在改进了现有GSM系统后能实现高速的数据传输。首先对GPRS系统做了简单介绍,然后在此基础上详细介绍了GPRS的板间切换在CPX8216硬件平台上的实现方法。     

Analytical general results for handoff dwell time distribution in wireless networks

1 Introduction The calling dwell time characteristic is critical for the user network planning and deployment, e.g., global system for mobile communications (GSM), as well as the next generation wireless multimedia networks, such as, the currently standar…     

Stateful session handoff for mobile WWW

This paper proposes a web session handoff system that can hand over not only stateless but also stateful sessions between homogenous and heterogeneous user devices to enable uninterrupted and seamless web access. The proposed system adopts a proxy-based approach and an optional client-assisted scheme in order to track and hand over session information. In the proposed system, a session is registered at a User Agent Proxy (UAP) and then tracked by the UAP so that the session can be handed over from one device via the UAP to another device. In addition to session information tracked by a UAP, the UAP can hand over more comprehensive session information by using the client-assisted scheme. Compared with client-based approaches, our design has several advantages, such as less modification to user devices, practicability, and fault tolerance. We have implemented a UAP on a PC and client programs for both PC and PDA. The implementation can successfully hand over between PC and PDA a stateful session for online shopping applications.     

服务自组织途径的信息系统生存性增强

在组件冗余备份的前提条件下,提出一种基于连接迁移技术的服务自组织方法。该方法根据服务处理流程将系统组件分解为通信组件、服务分发组件、数据存储组件;备份组件将其生存性信息实时发送给工作组件,并获取最新服务状态列表,当某一组件生存性最高时,根据组件的功能及其在体系结构中的位置,通过多种连接迁移技术进行服务自组织。利用仿真实验验证了生存性计算的有效性;并通过在网络环境中搭建一个Web服务器证明:在攻击情况下该方法可以有效提高稳态和瞬时的服务可生存性。     

密集WLAN中的分布式接入点功率调整算法

为了解决密集无线局域网( WLAN)中干扰严重、能耗高、网络性能难以优化等问题,提出了一种分布式接入点功率调整算法。终端周期性扫描获得备用接入点集合,并计算关联到备用接入点的功率等级信息。各接入点收集本地关联终端的上述信息,以降低发射功率为准则独立地计算终端的最优接入点。本算法能够在满足终端吞吐量需求的条件下,自适应地完成接入点功率调整和关联接入点的切换,降低WLAN在非高峰时段的整体能耗。     

无源传感器对雷达目标指示中触发准则研究

针对多传感器协同跟踪中无源传感器对雷达的目标指示问题进行了深入分析,重点研究了目标的指示交接需求及其触发机制.分析了协同跟踪中的目标指示交接需求,同时依据无源与有源传感器协同特性建立顺序处理结构的多传感器融合跟踪模型.在此基础上,采用协方差控制思想设定无源传感器对雷达的目标指示触发准则.通过仿真对触发准则进行了验证,并讨论了目标指示触发时机的影响因素,确保传感器间的目标指示能够自发进行.     

WCDMA无线通信系统在煤矿的应用分析

针对当前煤矿对无线通信系统的要求,分析比较了现有矿用无线通信系统的特点,阐述了WCDMA矿用无线通信系统的优势,并对其关键技术进行分析;介绍了该系统的网络架构和功能特点。应用结果表明,该系统能够满足煤矿日常生产管理的通信需要。     

一种基于LWAP的IEEE 802.11平滑切换机制

IEEE 802.11网络中的BSS切换不可避免地产生丢包问题,这会造成网络性能严重下降,进而限制了移动环境下WLAN的广泛应用。为了降低切换过程中的丢包率,本文提出了一种在数据链路层、由无线链路事件触发的用户空间平滑切换机制,并且在基于嵌入式Linux平台的无线AP上进行了实现。大量的实验结果表明,在无需对当前IEEE 802.11协议进行改动的前提下,新切换机制可以保证在允许的时延范围内,较大地降低丢包率,提高网络性能,并且可以支持平滑漫游。改进的平滑切换机制独立于驱动,具有良好的可移植性,可以在现有AP上增量添加,而无需更改STA,降低了升级成本。