低轨卫星网络中位置寻呼方法

在LE0卫星通信网络中,为了将呼叫传递到移动用户,必需知道用户当前的位置,即移动用户定位,包括位置更新和位置寻呼两个过程。由于LEO卫星覆盖区随时间变化迅速,造成传统位置寻呼方法的信令代价和寻呼时延性能不能满足系统要求。该文针对LEO网络的运动特点,提出了顺序概率位置寻呼(PP:Sequential Paging Based User’s Probability)方法,开通过仿真对SP和其它已有寻呼方法在寻呼时延和寻呼信令代价方面做了比较。     

LEO卫星网络动态混合卫星切换策略

LEO卫星网络切换协议中的路由选择策略应当综合考虑路由本身优化性,路由计算复杂性,路由更新的信令代价。提出适合LEO网络卫星切换要求的动态混合路由选择策略(DHRS:DynamicHybridRouteSelection),即发生卫星切换时,由卫星节点根据移动终端用户切换前所处位置和切换前路由表等信息,为移动终端选择合适的路由。     

LEO卫星网络中基于门限的切换优先资源管理机制

本文针对低轨道(Low Earth Orbit,LEO)卫星网络提出了一种基于门限的切换优先(Threshold-based Handover Prioritization,TBHP)资源管理算法,通过推迟信道锁定的时间来提高资源预留的精度,在保持高优先级用户强制中断概率极小的条件下改善网络用户的新呼叫阻塞概率,从而获得较高的系统无线资源利用率.建立了该算法的理论分析模型,确定了系统参数、业务条件与协议的工作参数之间的量化关系.仿真结果表明,TBHP算法在保留了经典GH算法保证高优先级用户切换过程的优点的同时,增大了系统允许接入新呼叫的概率,从而进一步提高了系统的资源利用率.     

GSM网位置区寻呼容量及其划分的研究

介绍了寻呼原理、寻呼信令流程和寻呼参数，探讨和计算了不同寻呼方式下位置区（LAC）的寻呼容量，并结合现网情况提出了LAC边界划分原则，给出了LAC设置和划分方法。     

一种GEO/LEO卫星网络中的路由优化策略

空间信息网络具有全球覆盖的能力,是能够保证高速率传输和较宽的带宽,支持灵活的、大规模的网络结构。GEO/LEO双层卫星网络由于具有覆盖关系简单、实施复杂性低等优势成为构建多层卫星网络的新思路。基于卫星群和卫星簇的分层结构,提出了一种GEO/LEO卫星网络中的路由优化策略,该策略主要是通过引入优化卫星路由表和路由信息数据报来实现的。最后的复杂性分析表明该策略在降低网络的星上存储开销和星间通信开销方面具有较高的优越性。     

基于蚁群算法的LEO卫星网络QoS优化路由

针对传统低轨卫星网络资源利用严重不均衡和高负载下业务服务质量(Quality of Service,QoS)无法得到保障的问题,提出了一种在负载均衡的基础之上满足多约束QoS保障的路由算法,并基于改进的蚁群算法实现.首先对全球潜在流量需求进行预测,基于此优化了启发函数;然后对路径代价和信息素更新策略进行了改进;最后选择...     

LAC区与寻呼关系浅析

LAC区用于标志不同的位置区域,随着网络的不断发展而进行LAC区的划分是必要的.LAC区的划分受寻呼次数的制约是很明显的.给出了寻呼原理、寻呼信令流程和寻呼参数设置,计算了在不同寻呼方式下的寻呼容量.结合现网情况分析了LAC区划分受寻呼制约的情况.根据话务模型给出了进行LAC区划分的合理方法.     

LEO卫星网基于时间和距离的位置更新策略

针对LEO卫星网中的动态位置区划分提出的一种基于时间和距离的位置更新策略,不同以往的处理方式,提出的更新策略中动态位置区更新半径随着用户的运动速度和业务繁忙程度而改变,对高速用户和低速用户分别采用不同的更新半径,当系统的业务繁忙程度改变时更新半径也相应的改变,仿真结果表明文中提出的位置更新策略对于移动用户比较多并且业务突发情况,能有效的减少位置管理开销,节省了系统资源。     

TD寻呼原理及寻呼策略优化的方法

寻呼成功率是衡量网络性能的一个重要指标,同时对于所有手机用户是否能够成功作被叫来说十分重要。寻呼成功率主要取决于以下因素：位置区、寻呼方式、寻呼组设置和无线环境,本文主要讨论寻呼策略对寻呼成功率的影响,并提出优化建议。     

LEO/MEO卫星网络中运用自组网思想的动态路由算法

分析了基于星际链路的LEO/MEO路由算法的特点及卫星网与自组网的相同之处，借鉴了自组网路由协议中适用于卫星网的部分，提出了LEO/MEO卫星网络中运用自组网思想的动态路由算法，并对算法进行了模型仿真和性能分析，这种算法增强了卫星网络的自适应性，使网络具有自治性强，功能更全面、系统开销小、适用范围广等特点。     

低轨卫星系统中结合时间和移动的位置更新策略

低轨(LEO)卫星快速运动,移动终端(MT)相对于卫星的位置信息也在不断变化,如何有效地管理MT的位置信息,减小位置更新频率和寻呼开销是研究位置管理的主要目的。为此,提出一种低轨卫星系统中的动态位置管理策略,基于时间和移动相结合进行位置更新,在不增加寻呼开销的条件下,减小了位置更新频率,从而有效降低了位置管理的总开销。     

LEO卫星网位置管理策略研究

本文总结了传统的 LEO卫星网的位置管理策略 ,并提出了 LEO网基于卫星自主定位的距离门限位置管理方案。该方案定位直接通过本网络卫星实现 ,减小了移动终端的代价和复杂度。另外 ,该方案虽然增加了定位开销 ,但是大大减小了位置更新和寻呼开销     

Efficient Location and Paging Area Planning in Future Cellular Systems

Efficient resource utilisation in future cellular systems is partly related to the location update and paging operations, which rely on proper planning of location and paging areas, and the application of efficient paging schemes. Important is the design of low complexity planning algorithms that may enable the system to dynamically adapt to new traffic and mobility conditions. In this paper we define and solve versions of the location and paging area planning problems focusing also on algorithms that are applicable in real-time. Thus, they can be used to adapt location and paging areas to traffic and mobility conditions. Starting from a formal definition and an optimal formulation, we solve efficiently by means of a low complexity heuristic, a general version of the location area planning problem. Regarding paging area planning, we provide a low complexity algorithm, under the assumption that the scheme applied falls within the last interaction based paging (LIBP) category. The results presented, and the low cost and complexity induced by the proposed schemes, indicates that the real-time application of the schemes is feasible.     

适于低轨卫星IP网络的特定源组播算法

为了解决低轨卫星IP网络中现有特定源组播算法的信道资源浪费问题,本文提出了一套新的特定源组播算法,即基于核心群的特定源组播算法(CSSM)和加权的CSSM算法(w-CSSM).CSSM算法以源节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,所得的树代价最小,从而大大提高了网络的带宽利用率和传输效率.在w-CSSM算法中,加权因子可以自适应调整以适度增大树代价、降低端到端传播时延,以支持某些有严格端到端时延要求的实时组播业务.通过与低轨卫星IP网络中典型特定源组播算法MRA的仿真比较,可以看出CSSM和w-CSSM算法的树代价性能比MRA有较大改善,不过端到端传播时延略高.     

A Model for the Handover Traffic and Channel Occupancy Timein LEO Satellite Networks

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A New Connection Admission Control for Spotbeam Handover in LEO Satellite Networks

Frequent spotbeam handovers in low earth orbit (LEO) satellite networks require a technique to decrease the handover blocking probabilities. A large variety of schemes have been proposed to achieve this goal in terrestrial mobile cellular networks. Most of them focus on the notion of prioritized channel allocation algorithms. However, these schemes cannot provide the connection-level quality of service (QoS) guarantees. Due to the scarcity of resources in LEO satellite networks, a connection admission control (CAC) technique becomes important to achieve this connection-level QoS for the spotbeam handovers. In this paper, a geographical connection admission control (GCAC) algorithm is introduced, which estimates the future handover blocking performance of a new call attempt based on the user location database, in order to decrease the handover blocking. Also, for its channel allocation scheme, an adaptive dynamic channel allocation (ADCA) scheme is introduced. By simulation, it is shown that the proposed GCAC with ADCA scheme guarantees the handover blocking probability to a predefined target level of QoS. Since GCAC algorithm utilizes the user location information, performance evaluation indicates that the quality of service (QoS) is also guaranteed in the non-uniform traffic pattern.     

Satellite handover techniques for LEO networks

Low earth orbit satellite constellations could play an important role in future mobile communication networks due to their characteristics, such as global coverage and low propagation delays. However, because of the non‐stationarity of the satellites, a call may be subjected to handovers, which can be cell or satellite handovers. Quite many techniques have been proposed in the literature dealing with the cell handover issue. In this paper, a satellite handover procedure is proposed, that investigates and exploits the partial satellite diversity (namely, the existing common coverage area between contiguous satellites) in order to provide an efficient handover strategy, based always on a tradeoff of blocking and forced termination probabilities for a fair treatment of new and handover calls. Three different criteria were examined for the selection of a satellite. Each one of them could be applied either to new or handover calls, therefore we investigated nine different service schemes. A simulation tool was implemented in order to compare the different service schemes and simulation results are presented at the end of the paper. Copyright © 2004 John Wiley & Sons, Ltd.