LTE-A载波聚合中的载波接入和切换管理策略研究

提出了几种主频点接入的选择策略,以及不同RRC信令开销的频点切换管理方法。通过理论分析结合系统级动态仿真,对提出的策略和方法进行了比较。从不同的载波聚合场景、用户移动速度、频点测量周期等方面研究分析了切换次数、切换失败率、RRC重配置数量等性能。     

A seamless handoff scheme for IEEE 802.11 wireless networks

The advance of computer network technologies such as IEEE 802.11 wireless local area network has made it possible for users to connect to Internet almost anywhere. A mobile node (MN) is likely to move between different base stations while running applications. The IETF has defined the Mobile IP (MIP) to allow MNs to maintain their communication uninterrupted while roaming across different IP subnets. However, the mechanisms defined in MIP may cause undesired connection disruptions or packet losses, which will significantly degrade the quality of real‐time applications. It is an important and challenging issue to support seamless handoff management. To achieve seamless handoff, we propose a unified scheme to address application quality degradation. Our main contribution is the concept and implementation of utilising buffering and resending method to eliminate the packet losses while keeping the end‐to‐end delay of real‐time traffic flow in an acceptable value. The NS‐2 simulation results show that our proposed scheme can significantly maintain application quality during layer‐2 and ‐3 handoffs. Copyright © 2011 John Wiley & Sons, Ltd.     

虚拟物流中心和信息平台的设计与构建

对虚拟物流中心的性质、职能、运作模式及关键成本进行深入分析提出了构建虚拟物流中心需要解决的三个关键问题提出了构建虚拟物流中心的系统方法和理论提出虚拟物流中心的信息平台建设的重要性。提出物流的实体网络与虚拟网络的无缝结合已成为现代物流需求的首要目标和物流行业的发展方向。     

Outage Performance with Handover Triggering in Cellular Mobile Networks

An approach to performance evaluation of cellular mobile networksis proposed, which includes the behavior of handover algorithmsin the computation of outage probability.In a general system scenario, with a central cluster and interferingbase stations, the average outage probability is computed along a trip of themobile terminal that involves crossing the boundary between adjacent cells.The effects of correlated co-channel interferersare accounted for in the computationof outage probability, as well as in the dynamics of a relative signalstrengthhandover algorithm.Numerical results are provided and discussed as obtained over a wide rangeof values of system parameters, namely cluster size and channel parameters.Trade-off curves are shown in terms of outage probability and cross-overpoint versus the average number of handovers, and possible design criteriaare outlined.It is also seen that the local outage analysis (without handover triggering)can be referred to as a lower performance bound in cases of practicalinterest.     

无缝钢管激光视觉准直技术

应用多个激光线结构光传感器对无缝钢管进行光切,求出各个光切面中心点的空间三维坐标,由此确定钢管轴线的直线度。本文提出了无缝钢管直线度激光视觉测量方法,推导了数学模型,进行了实验研究,给出了实验结果。     

Adaptive distribution‐based handover scheme for cellular communication networks

In this paper, we propose a new Generalized Distribution‐Based Handover (DBHO) to deal with the inefficient utilization of spectral resources due to the non‐uniform cell loads. The DBHO scheme is different from the existing adaptive schemes since it uses a new criterion to initiate handover when moving from/to a congested cell. Two risk factors are used to dynamically change handover boundaries according to the distribution of traffic loads. This controls the handover initiation process such that a user in a congested cell that is moving to a free cell is allowed to initiate a handover to a new cell earlier, as long as the signal received from the target cell is higher than a certain threshold. While delaying the handover initiation process for a user moving in the opposite direction, as long as the signal received from the serving cell is not lower than a certain threshold. Our results show a substantial reduction in the handover and call dropouts rates. Our scheme is complementary to the existing adaptive schemes proposed in the literature. The proposed scheme also gives cellular system designers a new tool to optimize the overall network performance by initiating handovers based on the traffic intensities. Frequent handovers increase the load on switching networks, which consequently degrades the Quality of Service (QoS). Existing handover schemes usually use parameters such as the received signal strength for initiating a handover with some additional measurements to reduce unnecessary handovers and call dropouts. These schemes perform well when cell loads are somewhat evenly distributed, but fail to account for nonuniform traffic, as is often the case in microcells. Hence, it is desirable to design efficient handover schemes to avoid unnecessary handovers, reduce call dropouts and yet dynamically adapt to the variation of traffic among cells. In this paper, we present a new adaptive handover scheme that dynamically changes the handover boundaries to balance cell loads and to effectively reduce the average number of handovers. Copyright © 2004 John Wiley & Sons, Ltd.     

A Handover Strategy in the LEO Satellite-Based Constellation Networks with ISLs

A new handover strategy named minimal-hops handover(MHH) strategy for the lowearth orbit(LEO) satellite constellations networks equipped with inter-satellite links(ISLs) is proposed.MHH strategy,which is based on the hops of the end-to-end connection paths and makes good use of theregularity of the constellation network topology,can appropriately combine the handover procedure withrouting and efficiently solve the inter-satellite handover issue.Moreover,MHH strategy can providequality of services(QoS) guarantees to some extent.The system performances of the MHH strategy,suchas time propagation delay and handover frequency,are evaluated and compared with that of otherprevious strategies.The simulation results show that MHH strategy performs better than other previoushandover strategies.     

基于OPNET的TD-SCDMA系统切换的研究

TD-SCDMA是由我国提出的第三代移动通信系统标准,采用一系列先进技术,具有较高的系统性能和频谱利用率,其中提出了一种新的切换技术-接力切换技术.文章通过功能强大的网络建模仿真工具OPNET对接力切换的算法进行动态仿真,研究在典型的车载环境下接力切换在多任务条件下如何提高TD-SCDMA系统切换质量.     

基于媒体独立切换并提供QoS保证的跨UMTS和WiMAX无线异构网络的网络切换方案

The rapid growth and innovation of the various mobile communication technologies have caused a change in the paradigm of internet access. Wireless technologies such as WiMAX, WiFi and UMTS/LTE networks have shown great potential in dominating the wireless access markets. The existence of various access technologies requires a means for seamless internetworking to provide anywhere, anytime services without interruption in the ongoing session, especially in multimedia applications with rigid Quality of Services (QoS) requirements. The IEEE 802.21 Media Independent Handover (MIH) working group was formed to develop a set of mechanisms under a standard framework with the capability to support migration of mobile users across heterogeneous networks. Therefore, the implementation of handover is extremely important in the heterogeneous network environment. In order to guarantee various QoS requirements during handover execution especially in multimedia applications, in this paper we propose a novel MIH-based capacity estimation algorithm to execute handover with QoS provision supporting both horizontal and vertical handovers across UMTS and WiMAX networks. Simulation shows that the proposed mechanism achieves lower call dropping rate (highest approximate 3% ) and higher system throughput (average 92% ) than the basic handover method does.     

一种金属填充硅通孔工艺的研究

硅通孔(Through silicon via)的互连技术是3D IC集成中的一种重要工艺。报道了一种高深宽比的垂直互连穿透硅通孔工艺,其通孔的深宽比达到50以上;研究了利用钨填充硅通孔的一些关键工艺,包括阻挡层淀积工艺和钨填充工艺,分析了不同填充工艺所造成的应力的变化。最后获得了一种深宽比达到58∶1的深硅通孔无缝填充。