上海移动针对位置更新成功率偏低问题的处理案例

位置更新过程由移动终端发起,一般位置更新的失败率在10%以内,造成位置更新失败的原因多为无线链路故障、HLR无用户数据、网络传输故障等,单个LAC区位置更新成功率下降30%基本可以认定为异常。本文通过中创信令监测系统数据,针对上海移动网络发生的位置更新指标恶化进行深入分析,定位了产生位置更新失败的终端型号。     

LEO卫星系统星上VLR数据库管理方案

在低轨(LEO)卫星通信系统中,航行在国外的特殊终端位置更新时需查询国内地面站访问位置寄存器(VLR),导致了长距离的信令开销.为此,提出一种星上VLR数据库管理方案,使移动终端能通过查询星上VLR进行位置更新操作.将该方案运用于具体低轨卫星系统进行仿真.结果表明,该方案能优化系统的位置管理性能.     

七号信令在移动通信故障定位中的应用

7号信令是由ITU-T制定的全球电信业的标准。这个标准指定了在通信中各个网络点通过数字信令网交换信息的过程及协议。在以电路交换为基础的GSM网络中,信令流程是一切通信过程的基本。只有确实掌握MS呼叫、位置更新、切换等通信过程中各接口的信令流程,才能有针对性地对网络故障进行分析定位。文中重点分析了GSM网络中位置更新的信令流程,结合信令监测系统获取的有效信令信息,对故障实例进行了分析,建立了一般的故障处理流程。     

基于C网用户信息的高速公路路况分析算法

物联网的关键理论、技术和应用已成为业界和学术界的研究热点,涵盖了从信息获取、传输、存储、处理直至应用的全过程。通过CDMA网络A信令接口获取信令变化信息,设计高速公路路况分析系统的体系架构和业务流程,在此基础上针对特定C网终端的信令交互数据研究统计分析算法,考虑用户位置更新间隔和基站关联数据密度两个关键属性,以省内部分...     

移动网信令风暴产生原因及解决方案分析

信令风暴的产生来源于终端和网络之间的频繁交互,包括终端发起和网络发起的网络连接过程.信令风暴导致用户体验下降,网络扩容压力增大.为解决信令风暴问题,终端侧可以通过优化操作系统闹钟服务实现心跳分组对齐,降低终端联网次数;网络侧主要通过优化寻呼机制和寻呼区的方式降低信令风暴的影响.还介绍了3GPP标准化组织正在进行的小数据分组传送技术方案,通过信令简化降低网络信令负荷.     

IMS域的位置管理策略研究

UMTS(Universal Mobile Telecommunications System)R6中IMS(IP Multimedia Subsystem)域的用户的位置都要注册到归属地网络,而且终端的所有SIP信令都要经过注册服务器,导致用户在漫游状态下控制信令的迂回路径变长并限制了用户对网络中应用的使用.该文对UMTS R6的IMS位置管理方案进行了改进,提出了IMS用户位置信息的分布式管理和联系人位置信息自适应缓存机制,使得其漫游状态下的位置注册和呼叫建立过程更加迅速.分析及仿真显示:新的位置管理策略从网络信令花费上优于原位置管理策略.     

一种移动终端完备身份信息的识别方案

提出了一种基于GSM基站技术对移动终端完备身份信息的识别方案。利用GSM网络的单向认证特性以及位置更新原理,设计了一种多次对终端不同类型身份请求的机制。模拟基站利用空中接口实现与移动终端交互信令,完成对包括TMSI、IMSI、IMEI及IMEISV在内完备身份信息的识别。该方案在网络原有VLR发生数据丢失,TMSI不可用时,能有效对终端的其他身份信息进行获取识别。测试表明,系统可以有效地对基站管控范围内终端的各类身份信息进行准确地识别与管理。     

一种基于位置更新机制的WCDMA用户屏蔽选通系统实现方案

提出了一种基于位置更新机制的WCDMA用户屏蔽选通系统实现方案。该方案利用WCDMA小区重选、身份识别和位置更新的机制,通过建立虚拟小区,诱使用户发起小区重选。通过控制信令流程,在用户位置更新过程中发起身份识别过程,获得用户的身份信息,并通过伪造位置更新回复信令,实现对覆盖范围内用户的通信屏蔽与选通。WCDMA用户屏蔽选通系统在不影响用户正常通信情况下,屏蔽非法用户的通信,可以有效应对WCDMA移动网络违规使用所带来的安全隐患。     

简谈道路覆盖场景下的位置更新

基站通过设置独立的LAC/TAC(位置区域代码/跟踪区域代码),可收集用户位置更新信息,从而掌握特定移动用户动态信息。但在用户流动较大区域,频繁的位置更新容易造成接入信道拥塞,影响网络质量和用户感知。设置合理的基站站间距及栽频配置可减小对网络用户的影响。文章讨论在道路覆盖场景,不同制式、不同车速和不同载频配置情况下,保证网络不拥塞,能准确获取位置更新信息时系统所能容纳的最大用户数。指出网络拥塞出现后位置更新将失败,无法追踪相关移动终端,会给用户、网络和服务质量带来的负面影响。     

LTE寻呼优化方案研究

分析了LTE网络中的寻呼优化需求,针对固定位置或低移动性终端,提出2种解决方案,分别是基于网络侧的寻呼优化方案和基于终端的寻呼优化方案,并分析了对现有网元功能的影响,从而在保证一定的寻呼成功率的基础上,通过减小寻呼区域的方式来降低寻呼的信令负荷。     

基于报文的指挥系统性能测试模型研究及应用

指挥系统是现代战争的重要武器装备,其通信性能关乎武器装备的正常工作。在研究前人工作的基础上,为了更加快速、高效地测试系统通信性能,提出了基于报文的指挥系统通信测试模型及其软件、硬件实现的基本思路。对指挥系统通信性能测试具有指导意义。     

Theoretical Limits Analysis of Indoor Positioning System Using Visible Light and Image Sensor

To solve the problem of parameter optimization in image sensor‐based visible light positioning systems, theoretical limits for both the location and the azimuth angle of the image sensor receiver (ISR) are calculated. In the case of a typical indoor scenario, maximum likelihood estimations for both the location and the azimuth angle of the ISR are first deduced. The Cramer‐Rao Lower Bound (CRLB) is then derived, under the condition that the observation values of the image points are affected by white Gaussian noise. For typical parameters of LEDs and image sensors, simulation results show that accurate estimates for both the location and azimuth angle can be achieved, with positioning errors usually on the order of centimeters and azimuth angle errors being less than 1°. The estimation accuracy depends on the focal length of the lens and on the pixel size and frame rate of the ISR, as well as on the number of transmitters used.     

Design and analysis of novel quorum-based sink location service scheme in wireless sensor networks

Geographic routing in wireless sensor networks requires sources nodes to be aware of the location information of sinks to send their data. To provide the sink location service, quorum-based schemes have been proposed, which exploit crossing points between a quorum of a sink location announcement (SLA) message from a sink and a quorum of a sink location query (SLQ) message from a source node. For guaranteeing at least one crossing point in irregular sensor networks with void areas or irregular boundaries, the previous schemes however collect and flood the network boundary information or forward a SLA and SLQ message along the whole network boundary. In this paper, we design a novel quorum-based sink location service scheme that exploits circle and line quorums, which does not require the network boundary information and send a SLA and SLQ message along the whole network boundary. In the proposed scheme, a source node sends a SLQ message to the network center and sends another SLQ message to an edge node in the network boundary, thus generating a SLQ line quorum. On the other hand, a sink node sends a SLA message along a circle path whose center is the network center, thus forming a SLQ circle quorum. By this way, it is guaranteed that the SLQ and SLA quorums have at least one crossing point in irregular sensor networks. Both numerical analysis and extensive simulation results verify that the proposed scheme outperforms the existing schemes in terms of the delivery distance, the delivery hop count, and the energy consumption for providing sink location service.     

面向ZigBee网络节点安全定位的消息签名方案

针对ZigBee网络节点定位中消息的安全性问题,该文提出一种带隐私保护的消息签名方案。方案基于椭圆曲线(ECC)上的无双线性对运算,设计了带身份隐私保护的定位请求消息签名算法和坐标隐私保护的定位参照消息签名算法。理论证明了所提方案可抵御伪造攻击、重放攻击等多种外部攻击,同时具备隐私保护、身份追踪等功能。性能分析结果表明,与同类方案相比,所提方案计算开销和通信开销均具有优势。     

Providing multicast short message services over self-routing mobile cellular backbone network

The short message service (SMS), a bidirectional service for short alphanumeric (up to 160 bytes) messages, is a unique feature of GSM not found in older analog systems. Multireceiver short message traffic has increased amazingly over the years. We propose a multicast SMS architecture over our backbone network. Then, we demonstrate some approaches to maintain the SMS center location information consistent with the home location register and illustrate our scheme for mobile terminated short message transfer. Finally, we simulate and evaluate this architecture. Our simulation indicates that the proposed strong consistency approaches have optimal efficiency by adjusting parameters, and the proposed architecture efficiently provides self-routing capability and multicast functionality in our cellular backbone network. The study also provides a further insight on the issues of multicast wireless cellular backbone network and demonstrates a referable methodology to propose and analyze a multicast cellular backbone network, which can promote the technology of a personal communication network.     

An efficient multicast protocol for PCS networks

In a Personal Communication Services (PCS) network, mobile hosts communicate with other mobile hosts through base stations on a wired (static) network. The mobile hosts connect to different base stations through wireless links and the base stations to which mobile hosts are connected change depending on the current location of the mobile hosts. In this environment, the problem of efficiently delivering a multicast message from one mobile host to a group of other mobile hosts becomes challenging. In this paper, we present a multicast protocol that delivers multicast messages from a mobile host to a group of other mobile hosts without flooding the wired network. The multicast protocol is built on top of a user location strategy that should follow one of the three models of user location described in the paper. The basic multicast protocol proposed guarantees exactlyonce message delivery to all mobile hosts in the multicast group and also ensures that multicast messages are delivered in FIFO order from the point of view of the base station that originates the multicast message (referred to as BSFIFO). More importantly, an extension of the basic protocol is provided that, unlike earlier work, delivers multicast messages in FIFO order from the point of view of the mobile host that initiates the multicast message (referred to as MHFIFO). The modifications to be made to the multicast protocol to accommodate each of the three models of user location is also described.     

Reconstructing insulin secretion rate after a glucose stimulus byan improved stochastic deconvolution method

Reconstructing insulin secretion rate (ISR) after a glucose stimulus by deconvolution is difficult because of its biphasic pattern, i.e., a rapid secretion peak is followed by a slower release. Here, we refine a recently proposed stochastic deconvolution method by modeling ISR as the multiple integration of a white noise process with time-varying statistics. The unknown parameters are estimated from the data by employing a maximum likelihood criterion. A fast computational scheme implementing the method is presented. Monte Carlo simulation results are developed which numerically show a more reliable ISR profile reconstructed by the new method.     

Optimal Utilization and Effects of Inaccurate Estimation in Mobile Database Failure Restoration

Mobility databases such as home location register and visitor location register are adopted to support mobility management in personal communications services networks. If a visitor location register fails or crashes, the subscribers' services will be seriously degraded due to the loss or corruption of location information. In this paper, we optimize utilization of demand re-registration messages for an adaptive p-persistent backoff database failure restoration scheme. An analytical model is developed and validated with simulations to obtain the optimal utilization using appropriate parameters so that the failed visitor location register is restored with the fastest speed. Some interesting aspects on the performance are studied and their deep insights are observed, such as effects of message sizes on choices of system parameters, effects of the inaccurate estimated number of stations, etc. One observation is that optimizations of utilization and successful transmission probability are two different goals, and a value to achieve the optimal successful transmission probability does not necessarily ensure optimal utilization. Furthermore, we also propose a scheme how to handle the problem with inaccurate (estimated) number of stations.     

A Privacy-Preserving Location Assurance Protocol for Location-Aware Services in VANETs

A location-aware service on a vehicular ad hoc networks (VANETs) is to provide services that distribute on-demand information for a certain geographic area of interest by taking advantage of vehicular communications. In this paper, we propose a secure and location assurance protocol in order to guarantee privacy preservation in vehicular communications and trustworthiness of location-aware services over VANETs. The proposed protocol enables a message verifier to have confidence that the location-aware information was responded from the vehicles passing through the target location area of interest without violating location privacy of the responders. To achieve our security objectives, we consider a pseudonym-based privacy-preserving authentication and a hierarchical identity-based cryptographic scheme. Furthermore, we demonstrate experimental results to confirm the efficiency and effectiveness of the proposed protocol.     

基于信息熵的美军C4ISR系统效能评估

随着美军信息化水平的不断提高,C^4ISR系统“战斗力倍增器”的作用更加突出,对美军C^4ISR系统的效能进行评估并分析其对作战效能的影响,具有重要的理论和现实意义。对影响C^4ISR系统效能的相关因素进行了分析,利用香农信息熵和图论的方法,建立了C^4ISR系统效能评估方法,研究了信息、网络、作战流程等因素对作战效能的影响,并建立了数学模型;以美军航母战斗群空袭作战为例,比较了“平台中心战”和“网络中心战”两种作战方式中C^4ISR系统的效能。