SDH指针调整机理与故障定位

SDH设备采用指针技术 ,可以时刻指示低速支路信号在净负荷中的位置 ,当与时钟有关的电路板发生故障和时钟配置错误 ,会引起指针频繁调整 ,使传输性能发生劣化 ,可以根据指针调整现象结合组网结构 ,进行故障定位。     

Betacam SP录放机典型故障的处理

放像机PVW—2600P (1)现象:工作一段时间(大约半小时),出现“Error 14”,再过一会儿即自动断电(但此时各种表头指针仍摆动)。过几分钟重新开机,仍显示“Error 14”,长时间后重新开机正常。 分析与处理:查手册知,该故障为电风扇不转,经查发现连接插头松动,重新接好,故障排除。说明该故障是由于电风扇停转造成电流散     

联合收割机远程监测故障数据库设计

目前多数联合收割机故障监测系统上不具备故障数据库,文中设计研发一套基于LabVIEW的联合收割机的远程故障监测系统并带有故障数据库。通过ARM进行数据采集,通过外接多种传感器,可实现对收割机前进速度,滚筒转速等的实时状态监测,通过数据存储,显示及分析,判断故障位置,进而实现远程故障诊断。系统添加故障库功能,可进行故障补救措施查询及新故障添加,对收割机故障进行提前预防和快速的事后处理。     

基于电压暂降测量的配电网故障自动定位

文中提出了一种结合电力系统分析程序、数据库检索方法和模式识别技术自动识别的11kV配电网故障定位方法。该方法采用三相不平衡潮流和故障分析程序,对配电网各节点的故障进行分析生成电压暂降数据库,设计了数据库搜索和模式识别算法,以便配电网在发生实际故障时识别故障位置。利用电力系统EMTDC模拟器对该方法进行了评估和测试。实验结果表明,提出的线性模式识别算法能够识别所研究的11kV配电网的大部分故障区段。     

广电宽带故障排查及提升预警响应能力的Web业务系统

为了提升服务效率及服务质量,使社区工程师能够对针对用户反映的宽带问题实现故障快速定位,同时提升宽带大面积故障预警的能力,江苏有线盐城分公司根据本地化需要定制开发了《宽带查询系统》.该系统使用Java语言基于SpringBoot 2.0框架开发,数据库持久层采用了MyBatis框架,数据库连接池则采用了阿里巴巴Druid...     

H-600透射电镜故障实例检修

最近,我校H-600透射电镜产生高压漏电等故障,现把检修情况概要介绍如下:(1)故障现象:加上25kV高压时,指针越过25kV后,大幅度前摆并立即产生过流保护跳表现象。故障是在前几天,因台风暴雨屋顶渗漏,少量雨水滴落在高压油箱顶盖上,已连续数天进行除湿处理和抽真空维护以后仍发生的。为确定故障部位,首先对电子枪各部件净洁试机,再除下阴极、栅极重行试机,均产生以上高压跳表现象。证明故障并非因电子枪污染或短路引起。把电缆从高压油箱拔出后,再加25kV～100kV高压,指针指示正常,可见故障不在高压发生器,而在电缆身上。用500伏兆欧表检测电缆…     

江苏有线盐城分公司宽带故障排查及预警系统

为了更好地服务宽带用户,使社区工程师可以对宽带故障原因作快速定位,提升宽带大面积故障预警的能力。江苏有线盐城分公司定制开发了《宽带查询系统》,该系统使用Java语言基于SpringBoot 2.0框架开发,数据库持久层采用MyBatis框架,数据库连接池采用阿里巴巴Druid技术。系统自部署以来运行稳定且有效提升了宽带服务效率,操作简单,查询快捷。     

ZXJ10A程控用户交换机故障分析和处理

例1故障现象：一用户电话能呼出，呼入时能听到回铃音，但话机不振铃，用112测试台送铃流时话机振铃。故障分析：产生此种故障一般有3种情况：（1）该用户可能设置了呼叫无条件前转功能；（2）话机故障；（3）用户板故障。故障处理：（1）先检查该用户是否设置了呼叫无条件前转功能。经检查该用户未设置呼叫无条件前转功能。（2）再采取替换法（比较法）对故障进行查找：①先调换话机，调换后，故障依旧；②将不振铃的这个用户的用户板拔下插入其它好的用户板的楷位上进行试验，如故障随该用户极走，证明该用户板有故障（试验结果为故障随用…     

指针推进移动性管理策略中指针链长度的概率

为了降低移动通信网络中位置跟踪操作的代价,指针推进策略被提出.显然,指针链长度的确定对这一策略的有效应用是至为重要的.已有论文假定移动台在位置区的逗留时间服从指数分布的条件下,对指针链的长度进行研究,但指数分布的特殊性,限制了其研究结果的应用.本文推广了上述结果,研究了移动台在位置区的逗留时间服从一般概率分布的指针推进策略,通过构造向量马氏过程,利用密度演化方法,导出了指针链长度的概率公式,这个公式可用于对各种指针推进策略性能的评价.     

区域电网光缆线路智能监测系统的数据传输技术研究

以区域电网光缆线路智能监测系统为研究对象,对其数据传输技术进行研究。采用数据库技术、计算机技术、GIS技术、网络通信技术、OTDR测试技术,对电网光缆线路智能监测系统的组成及功能、系统结构设计、系统关键模块OTDR光缆智能监测的实现、GIS光缆监测故障位置的判断、GIS光缆故障智能监测定位进行研究,系统通过对数据库存储的光缆线路地标信息的使用,经OTDR测试,可直接将故障信息显示在地标信息上,提供准确直观可视化故障信息给维护人员,使运维成本得到进一步降低,避免通信中断造成系统瘫痪引起的损失,这为今后应用区域电网光缆线路智能监测系统数据传输技术提供参考。     

One-step pointer forwarding strategy for location tracking indistributed HLR environment

One of the main challenges in personal communication service (PCS) is to locate many mobiles that may move frequently from place to place. Such a system operation is called location tracking. Many network signals flow, and database queries are required to achieve such a task. In addition to the two-level hierarchical strategy in IS-41 and GSM, several strategies have been proposed to improve the efficiency of location tracking. Pointer forwarding was used to reduce the expensive home location register (HLR) accesses. Previously, the distributed HLR scheme was proposed to prevent the HLR from becoming a bottleneck in the signaling network. However, the length of a forwarding pointer chain may be lengthened in a distributed HLR environment. We propose a more efficient strategy to overcome this potential problem. This strategy attempts to migrate the locating chains in a distributed HLR system when a mobile issues a registration operation. As a consequence, the length of any forwarding pointer chain does not exceed one in our strategy. Simulation results indicate that our strategy significantly decreases the locating cost. In fact, this strategy provides an upper bound of location tracking time owing to the fact that the length of any locating path does not exceed one. Furthermore, obsolete entries in local databases visitor location registers can be reclaimed in this strategy     

Location tracking with distributed HLR's and pointer forwarding

Location tracking operations in a personal communications service (PCS) network are expensive. A location tracking algorithm called pointer forwarding has been proposed to reduce the location update cost. The key observation behind forwarding is that if users change PCS registration areas (RAs) frequently, but receive calls relatively infrequently, it should be possible to avoid registrations at the home-location register (HLR) database by simply setting up a forwarding pointer from the previous visitor-location register (VLR). Calls to a given user will first query the user's HLR to determine the first VLR, which the user was registered at, and then follow a chain of forwarding pointers to the user's current VLR. To reduce the “find” cost in call delivery, the PCS provider may distribute HLR databases in the network. This paper integrates the concept of distributed HLRs with pointer forwarding, and the new scheme is referred to as the pointer forwarding with distributed HLR (PFDHLR). Since no registration to the HLR is performed in the pointer forwarding scheme when a user moves to the new locations, the cost of updating multiple HLRs is eliminated in PFDHLR. Our study indicates that PFDHLR may significantly reduce the mobility management cost compared with the single HLR approach     

Two-level pointer forwarding strategy for location management in PCS networks

For a IPCS network to effectively deliver services to its mobile users, it must have an efficient way to keep track of the mobile users. The location management fulfills this task through location registration and paging. To reduce the signaling traffic, many schemes such as a local anchor (LA) scheme, per-user caching scheme and pointer forwarding scheme have been proposed in the past. In this paper, we present a new location management scheme which intends to mitigate the signaling traffic as well as reduce the tracking delay in the PCS systems. In this strategy, we choose a set of visitor location registers (VLRs) traversed by users as the mobility agents (MA), which form another level of management in order to make some registration signaling traffic localized. The idea is as follows: instead of always updating to the home location register (HLR), which would become the bottleneck otherwise, many location updates are carried out in the mobility agents. Thus, the two-level pointer forwarding scheme is designed to reduce the signaling traffic: pointers can be set up between VLRs as the traditional pointer forwarding scheme and can also be set up between MAs. The numerical results show that this strategy can significantly reduce the network signaling traffic for users with low CMR without increasing much of the call setup delay.     

基于阈值的两级指针推进的移动性管理策略

提出了基于阈值的两级指针推进策略(TPFT,two-level pointer forwarding with thresholds)将一部分VLR(visitor location register)中的移动用户选为移动代理(MA,mobile agent),在MA之间建立第一级指针链;在MA与VLR之间建立第二级指针链,两级指针链均设定长度阈值。将该策略与“基本位置管理策略”及“通行用户指针推进策略”和“带门槛的指针推进策略”的开销进行比较得出:选择适当的两级阈值,TPFT策略的开销优于上述策略。同时,TPFT策略是将系统中对HLR(home location register)的修改与查询的信号量分布到各个MA中,提高了系统效率。     

Location Management in PCS Networks by Caching Two-Level Forwarding-Pointers

One of the challenging tasks in Personal Communication Services (PCS) is to efficiently maintain the location of PCS subscribers who move from one region to another (hereafter called mobile users). When a mobile user receives a call, the network has to quickly determine its current location. The existing location management scheme suffers from high signaling traffic in locating the mobile users. Two-level forwarding pointer scheme has been proposed from per-user forwarding pointer scheme to reduce the cost of signaling traffic. In this paper, we enhance the two-level forwarding pointer scheme. When a mobile user moves from its current Registered Area (RA), which is served by Mobile Switching Center (MSC), to another RA the local switch that acts as a parent of those two MSCs maintains this movement in its memory (hereafter called cache entry). A cache entry is used to locate rapidly the mobile user instead of querying the Home Location Register (HLR) and waiting for its reply. HLR is centralized in the network and far away from the mobile users so that the signaling traffic crossing it is expensive. Sometimes the cache entry may be failed to reach the mobile user then a two-level forwarding pointers will be created from the corresponding Visitor Location Register (VLR), attached to its MSC, through a correct path to locate the mobile user. Thus, there is a saving in cost of querying the underlying HLR. The analytical results indicate that such proposal efficiently reduces the signaling traffic cost for all values of Call to Mobility Ratio (CMR), this is especially considerable when CMR ≥1, without any increase in the call setup delay. Salah M. Ramadan (samohra@yahoo.com) received the BS and MS degrees from Computers Engineering Department, Al-Azhar University, Cairo, Egypt, in 1995 and 2002, respectively. From 2002, he was a Ph.D. student in Computers Engineering Department at Al-Azhar University and is currently pursuing the Ph.D. degree, where he is a research assistant in the Wireless Networks Branch. His research interests include traffic management in ATM networks, routing protocols, mobility management in PCS networks, and mobile computing. He is currently an instructor in Cisco Academy, Egypt. Ahmed M. El-Sherbini (Sherbini@mcit.gov.eg) received the Ph.D. in Electrical and Communication Engineering, Case Western University, U.S.A. March 1983 and M.Sc. in Communication Engineering, Cairo University, Giza, Egypt, June 1980. (M. Sc. Research Studies at the Ecole Nationale Superieure des Telecommunications (ENST), Paris, France). He is the Director, National Telecommunication Institute – Ministry of Communications and Information Technology, Egypt and Professor of Electrical and Communication Engineering Dept. Faculty of Engineering, Cairo University, Egypt. M. I. Marie received his B.Sc., M.Sc. and Ph.D. in electronic and communication engineering from Cairo University on 1972, 1981, 1985, respectively. Now he is a professor of communications at Computer and System Engineering department Al-Azhar University, Cairo, Egypt. His fields of interest includes digital communication, computer networks and protocols development. M. Zaki (azhar@mailer.scu.eun.eg) is the professor of software engineering, Computer and System Engineering Department, Faculty of Engineering, Al-Azhar University at Cairo. He received his B.Sc. and M.Sc. degrees in electrical engineering from Cairo University in 1968 and 1973 respectively. He received his Ph.D. degrees in computer engineering from Warsaw Technical University, Poland in 1977. His fields of interest include artificial intelligence, soft computing, and distributed system.     

Improving the fault tolerance of GSM networks

A PCS network constantly tracks the locations of the mobile stations so that incoming calls can be delivered to the target mobile stations. In general, a two-level database system is used to store location information of the mobile stations. When the location databases fail, incoming calls may be lost. This article describes the standard GSM database failure restoration procedure which reduces the number of lost calls. Then we propose an efficient visitor location register (VLR) identification algorithm for the home location register (HLR) failure recovery procedure, which utilizes mobile station movement information to speed up the recovery procedure     

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.     

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。     

移动网络前向指针策略的鉴权管理研究

鉴权管理是移动通信移动管理中非常重要的技术,其策略的选择将直接影响网络中各网元的信令负荷。本文主要讨论移动通信系统前向指针位置管理策略中的鉴权管理。当用户在远离其HLR的不同VLR对应覆盖区域移动时,系统通过向其原VLR索取剩余鉴权数据或向其HLR申请新鉴权数据来实现用户的鉴权管理。通过鉴权开销及被呼处理时延等指标的分析,本文提出的鉴权管理算法较适合于CMR较小的MS鉴权管理;当MS的CMR增大时,本文提出的鉴权管理算法与二层管理策略如GSM或IS-41移动系统的开销及时延等指标逐渐接近。     

Group registration with local anchor for location tracking in mobile networks

In mobile networks, the location of a mobile user needs to be traced for successful and efficient call delivery. In existing cellular networks, as a mobile user changes his/her location area (LA), a location registration request is sent to the home location register (HLR) to update the user profile to point to the new LA. With a large number of mobile subscribers, this conventional registration strategy will incur a high volume of signaling traffic. We propose a new location registration strategy, called Group Registration (GR), which efficiently reduces the location registration cost by reporting location changes to the HLR for multiple mobile terminals (MTs) in a single location update request message. Specifically, the IDs of the MTs newly moving into an LA are buffered and sent to the HLR for location update in the route response message of the next incoming call to any MT in the LA. An analytic model is developed and numerical results are presented. It is shown that the proposed GR strategy can achieve significant cost reductions compared to the conventional strategy and the local anchor strategy over a wide range of system parameters. Moreover, the GR strategy results in a much smaller call delivery latency than the local anchor strategy.