带门槛的环形搜索移动性管理策略中移动台所 越过的位置区环数

位置管理或移动性管理是移动计算研究领域的一个具有挑战性的问题.我国及其他国家目前正在使用的个人通信网络如GSM、IS-41中,用两层数据库HLR/VLR支持位置管理.在这些网络中,每当移动台从一个位置区LA(Location area)移动到另一个位置区,其基本的位置管理策略(简称"基本策略")不管是否必要均立即进行位置更新操作,因而造成系统资源的极大浪费,降低了系统的性能.本文给出一种带门槛的环形搜索策略(简称"门槛环形策略")——将位置区分成环,设定一个门槛(整数),当移动台越过的位置区的环数没有达到门槛时,系统不进行位置更新操作,以减少位置管理的费用.在假定移动台的呼入是一个泊松过程,移动台在各个位置区的逗留时间是符合一般概率分布的随机变量的条件下,推导出在两次呼入之间移动台处于各位置区环的概率及移动台所越过的位置区环数公式,给出了"门槛环形策略"的位置管理费用小于"基本策略"的条件.     

小区分层依概率寻呼的位置管理策略

位置管理是移动通信领域的一个具有挑战性的问题,涉及到位置更新和位置查找操作.我国及其他国家目前正在使用的个人通信网络中,基本的位置管理策略(简称"基本策略")的位置查找操作采用的是,在整个位置区中同步寻呼移动台.由于所要寻找的移动台只在由众多小区所组成的位置区内的一个小区中,因此,"基本策略"会造成系统资源的极大浪费.本文给出一种对位置区内的小区进行分层,按移动台在各层小区的概率从大到小的次序,逐层进行寻呼的位置管理策略(简称"分层策略").在假定移动台在各个小区的逗留时间是符合一般概率分布的随机变量的条件下,推导出移动台处于各层小区的概率及"分层策略"所需搜索的小区平均个数公式.证明了"分层策略"的位置管理费用不大于"基本策略".     

蜂窝网络中环状搜索移动性管理策略

位置管理是移动通信领域的一个具有挑战性的问题,涉及到位置更新和位置查找操作.在现行蜂窝系统的位置管理策略(简称"基本策略")中,一旦移动台越区,就需要进行位置更新.由于移动台的越区具有局部性,基本策略会造成系统资源的极大浪费.因此,降低位置管理的费用成为移动通信领域的一个研究热点.该文给出不需要进行位置更新的环状搜索位置管理策略(简称"环状策略"),并推导出搜索位置区平均层数的一个公式,然后利用这一公式对基本策略、指针推进策略与环状策略的费用进行了对比研究,得出:在一定条件下,环状策略的费用要比基本策略及基本指针推进策略小.     

移动台越区次数的概率

在移动通信系统中，移动性管理即位置管理是一个具有挑战性的研究内容。移动台越区漫游规律的研究，对评价各种位置管理策略的代价及性能有着重要意义。通过构造向量马氏过程，利用密度演化方法，我们导出了移动台越区次数的一个概率公式，并用此公式对同行的位置管理策略及指针推进策略的代价进行了研究。     

码分务址数字蜂窝移动通信技术讲座──第三讲 码分多址蜂窝移动通信的特点和优越性

码分务址数字蜂窝移动通信技术讲座──第三讲码分多址蜂窝移动通信的特点和优越性朱云龙，吴彦群在蜂窝移动通信系统中，移动台与基站之间采用多址方式进行连接。频分多址就是对信号的频率参量进行分割，各个通话的移动台占用不同的频道。时分多址是将一个频道分成几个时...     

浅谈蜂窝移动系统中的定位技术

随着CDMA技术的应用与发展,蜂窝移动通信系统呈现出迅猛发展的势头。蜂窝网络中各种基于移动台位置的服务,如公共安全服务、基于移动台位置的计费、网络规划与设计、网络QoS和无线资源管理等,无不与准确定位移动台位置有关,使得对蜂窝网络中移动台定位技术的研究日趋活跃。本文综合论述了无线定位技术在第三代移动通信系统中的发展与应用现状,并对影响蜂窝网络无线定位精度的原因进行了详细分析与研究,最后指出了以后的研究方向。     

应用于第三代移动通信系统中的中继技术

分析了一种可应用于TD-SCDMA蜂窝移动通信系统的中继技术.该技术将Ad hoc和蜂窝系统相结合.在蜂窝移动通信系统中,移动台和基站之间的信号可以通过其他移动台转发.这种中继技术可以减少小区内移动台的发射功率,从而增加系统容量.作者在通用仿真平台OPNET上建立时分双工CDMA系统物理信道模型,并在系统中应用中继技术,通过仿真分析比较了系统的性能.     

蜂窝移动通信系统

模拟蜂窝移动电话在我国已有11年的发展史，1996年模拟网已实现全国联网，目前模拟手机用户已超过500万户。数字蜂窝移动电话1995年进入我国，现在数字手机用户已接近200万户。我国已成为世界最大的移动通信市场。下面介绍用户较关心的几个问题。一、蜂窝移动电话系统的组成和制式我国的蜂窝移动电话采用三级网结构，由移动台、基地站、移动业务交换中心构成。移动业务交换中心又与公用电话交换网相连，从而构成一个有线、无线相结合的移动通信系统。基地站提供移动台（手机）与移动通信系统联系的无线接口，并完成信令与话音的双向通信。每…     

一种蜂窝网中的跟踪算法

移动台定位技术是未来移动通信的方向。为了实现动态连续定位跟踪服务和提高定位精度,提出了一种在蜂窝网络中非视距（NLOS,Non-line of Sight）环境下对移动台（MS,Mobile Station）的定位跟踪算法。在用经典定位算法获得定位初始估计值后,利用卡尔曼滤波器对移动台的初始位置估计值进行修正,并配合检测门限对移动台进行跟踪。仿真结果表明,该跟踪算法能够实现对移动台动态定位跟踪,并且取得了良好的效果。     

蜂窝网络移动用户位置识别

随着蜂窝网络的出现和网络用户的日益增加,各种服务需求也逐渐增多,其中很多时候需要识别移动用户的确切位置。识别移动用户的确切位置的主要目的是当移动用户身处危难或移动用户发出最近的查询请求时,给他们提供服务帮助,当移动用户身处危难中时,服务基站通过收到的信号强度计算移动台到基站的距离．最后服务基站根据该距离以及移动台到其余近邻基站的距离．计算出移动台的确切位置,但是一旦移动台在发出请求后就改变了位置．在这种情况下．移动台在一定的时间间隔后发出另外一个信号．服务基站根据相继收到的两个信号计算出移动台的最后位置。     

Derivation of Moving Distance Distribution to Enhance Sequential Paging in Distance-Based Mobility Management for PCS Networks

The total signaling cost of distance-based location management scheme, which is the lowest among dynamic location management schemes for PCS networks, can be further reduced by a sequential paging strategy that pages first the cells in which the mobile is most likely located. To enable this strategy, we derive the probability distribution of a mobile's moving distances between the last location update and the next call arrival. An efficient and effective sequential paging scheme is presented, which guarantees that a mobile can be located during the first paging step with a probability equal to or better than a predefined value. The features of the proposed model include flexible cell topologies, general cell residence time, and full use of mobile's moving pattern     

Predictive distance-based mobility management for multidimensional PCS networks

This paper presents a mobile tracking scheme that exploits the predictability of user mobility patterns in wireless PCS networks. In this scheme, a mobile's future location is predicted by the network, based on the information gathered from the mobile's recent report of location and velocity. When a call is made, the network pages the destination mobile around the predicted location. A mobile makes the same location prediction as the network does; it inspects its own location periodically and reports the new location when the distance between the predicted and the actual locations exceeds a threshold. To more realistically represent the various degrees of velocity correlation in time, a Gauss-Markov mobility model is used. For practical systems where the mobility pattern varies over time, we propose a dynamic Gauss-Markov parameter estimator that provides the mobility parameters to the prediction algorithm. Based on the Gauss-Markov model, we describe an analytical framework to evaluate the cost of mobility management for the proposed scheme. We also present an approximation method that reduces the computational complexity of the cost evaluation for multidimensional systems. We then compare the cost of predictive mobility management against that of the regular, nonpredictive distance-based scheme, for both the case with ideal Gauss-Markov mobility pattern and the case with time-varying mobility pattern.     

A direction-based location update scheme with a line-pagingstrategy for PCS networks

On the problem of location update and terminal paging, many schemes using ring-paging strategies have been proposed. However, sequentially paging the rings surrounding the mobile user's last updated location may cause large paging cost. We propose a direction-based location update (DBLU) scheme using a line-paging strategy to reduce the paging cost. A moving direction identification mechanism using only simple computations detects the change of moving direction and updates the mobile's location. The numerical results show that our DBLU scheme achieves good performance when the paging cost is high     

Load-Balanced Location Management for Cellular Mobile Systems Using Quorums and Dynamic Hashing

This paper presents a new distributed location management strategy for cellular mobile systems. Its salient features are fast location update and query, load balancing among location servers, and scalability. The strategy employs dynamic hashing techniques and quorums to manage location update and query operations. The proposed strategy does not require a home location register (HLR) to be associated with each mobile node. Location updates and queries for a mobile node are multicast to subsets of location servers, which change with time depending on the location of mobile node/querying node and load on the servers. Simulation experiments demonstrate that such dynamism prevents situations of heavy load on some location servers when mobile nodes are not uniformly distributed in space, or when some mobile nodes have their location updated or queried more often than others. Also, queries return the latest location information of a mobile node with a very high probability. The proposed scheme requires at most one unicast and two rounds of message multicasting for location update and query operations. All multicast messages have a small payload and are restricted to the high bandwidth wired part of the mobile network resulting in low communication overhead. Moreover, if a quorum of location servers gets overloaded, part of its load can be transferred to another lightly loaded quorum using dynamic hashing techniques.     

移动通信中一种新的位置查询方案及其性能仿真

移动用户的剧增和移动通信业务的发展,对位置管理提出了更高的要求,因此,在移动通信的结构中,设计一个有效的位置管理方案是十分必要的。回顾了针对PCS网络的4种已经存在的位置查询方案,并提出了一种新的查询方案。仿真结果表明,这种新的位置查询方案在性能上要优于4种旧方案。     

Determination of the Registration Point for Location Update by Dynamic Programming in PCS

Location management is important to effectively keep track of mobile terminals with reduced signal flows and database queries. Even though dynamic location management strategies are known to show good performance, we in this paper consider the static location management strategy which is easy to implement. A system with single home location register and pointer forwarding is assumed. A mobile terminal is assumed to have memory to store the IDs of visitor location registers (VLRs) each of which has the forwarding pointer to identify its current location. To obtain the registration point which minimizes the database access and signaling cost from the current time to the time of power-off probabilistic dynamic programming formulation is presented. A Selective Pointer Forwarding scheme is proposed which is based on one-step dynamic programming. The proposed location update scheme determines the least cost temporary VLR which point forwards the latest location of the mobile. The computational results show that the proposed scheme outperforms IS-41, pure Pointer Forwarding, and One-step Pointer Forwarding at the expense of small storage and a few computations at the mobile terminals.     

移动IP网络中基于遗传算法的多步寻呼策略及性能分析

在移动IP网络中，层次移动IP协议可降低移动IP位置管理的信令消耗。该文研究支持寻呼的HMIPv6，提出了时延限制下的多步寻呼策略以及基于遗传算法的多步寻呼方案——根据移动节点的位置概率分布，采用遗传算法对寻呼区域内的所有子网进行分组，每步寻呼一个组，使平均寻呼信令开销达到或接近最优。此外，对HMIPv6、单步寻呼的HMIPv6以及基于遗传算法的多步HMIPv6寻呼方案的信令开销进行了比较分析，得出寻呼节省信令开销的必要条件。最后，给出一组数值结果以说明所提出的寻呼策略的有效性。     

Call admission control for mobile multimedia communications withtraffic asymmetry between uplink and downlink

The call admission control (CAC) for mobile communications is one of the most important engineering issues since it belongs to the category of resource management and the radio spectrum is a very scarce resource. In future mobile cellular systems, the CAC scheme should be efficient for multimedia services as well as for voice services. This paper proposes an advanced CAC scheme for mobile multimedia communications. A characteristic of the proposed scheme is that it takes account of the traffic (load) asymmetry between uplink and downlink in mobile multimedia environments, we evaluate the performance of the proposed scheme using Markov analysis. The performance measures on which we focus are the utilization of resources and the blocking probabilities of handoff calls and new calls. We present some numerical examples with practically meaningful parameter values. As a result, we show that the proposed CAC scheme can be a good choice for mobile multimedia systems such as the International Mobile Telecommunications-2000 systems