2007-1-18_直放站对联通G网干扰的排查分析

2007-1-18_直放站对联通G网干扰的排查分析 直放站对联通G网干扰的排查分析 直放站在今天的应用已非常普遍，从工作原理来看，它本质上是个双向功率放大器，在移动通信网络中主要起填补蜂窝小区信号传输空白区域的作用，体现在消除盲区、改善覆盖、扩展小区边界等应用上。 在无线传输中，它还可以充当中继，以提高链路余量，并为特定的基站吸收业务量。基于其体积较小、价格较低、结构简单、安装方便等特点，它不再是通信运营商的专有物，一些工厂、宾馆、商场、停车场等场所也会根据需要私自安装。 直放站在商业通信网络中发挥着积极作用的同时，由于其为数众多且管理上不够完善，也带来了不少副作用。如它恶化了公众移动通信频段的电磁环境，催生了众多无线电干扰，而且，对这些干扰的排查也并非易事。 直放站干扰排查实录 我们曾接到中国联通的干扰申诉，称:容桂华宝GSM900基站上行信号受到干扰，网络统计分析显示掉话率很高。他们认为是由机床产生的工业干扰，初步确定干扰源就在与基站一路之隔的广东美芝厂区内。我们出动监测车，利用车上的ESMB/DDF190监测/测向设备，同时开启E4407B频谱分析仪，分别接上全向及定向天线，在基站四周及广东美芝一带苦候干扰信号的出现。ESMB/DDF190系统在其高增益有源天线的强力支持下，倒是收到了信号，但却是假信号，频谱分析仪则一点动静都没有。但联通中心机房的网络统计分析显示，这段时间内干扰依然存在。 当监测车行经某知名公司厂房的大门口时，频谱分析仪显示屏上有了反应，底噪提高了近20dB。我们立即换上定向天线作简易测向，测得的信号最大值方向指向该公司办公大楼。于是，我们改用TekNet YBT250基站维护测试仪并配上EB200手持式测向天线入内查寻，绕大楼一周，最后将疑点锁定在电梯机房内。在楼顶电梯机房旁测得信号的最大值约为-70 dBm(频谱图如图1所示)。我们以为该信号是由电梯内的视频监视无线传输设备发出的，但遍寻不获。后来我们无意中发现楼下有两根天线立于停车场入口处的纤维遮光棚一侧，并在棚内又发现另一根。之后以手持天线对准其中一根定向八木天线，测得信号最大幅度接近-50 dBm(频谱图见图2)。我们沿着馈线顺藤摸瓜，发现在停车场入口旁一侧拐角的墙上，上下依次装了3个放大器。放大器的另一端分别接一根鞭状天线，固定于停车场天花板铁架上。 Details of green to introduce "the art of bonsai" concept, plant morphology, leaf color, aromas to create different moods and charms. (B) improving air pollution prevention and control. …… Air pollution sources in the four areas, a dust pollution and industrial enterprises of coal-burning pollution. A significant proportion of gypsum, stone processing enterprises and use of glass furnace standards of environmental protection facilities. Second, poor dust control, wide range of construction dust, road dust capacity. Three is to build coal-fired boilers in the region, particularly within the city's outdoor barbecue gas discharge seriously. Four motor vehicle exhaust is not inIn particular the greening of urban areas, it is necessary to carefully select the species suited to local soils, reflecting ... ... Features also allow for the evergreen trees, so that people walking in the shade. On one handTo expand green areas, improve planting quality fuss; but also to focus on simplicity and generosity of the green on the other hand, to enhance the Visual effect of green scale. Big green landscape according to the terrain the moderate, plant communities in natural, varied colors, flowers and clear principles, reflect the level, color and seasonal change. 图1 办公楼顶电梯机房旁测得的信号频谱 Details of green to introduce "the art of bonsai" concept, plant morphology, leaf color, aromas to create different moods and charms. (B) improving air pollution prevention and control. …… Air pollution sources in the four areas, a dust pollution and industrial enterprises of coal-burning pollution. A significant proportion of gypsum, stone processing enterprises and use of glass furnace standards of environmental protection facilities. Second, poor dust control, wide range of construction dust, road dust capacity. Three is to build coal-fired boilers in the region, particularly within the city's outdoor barbecue gas discharge seriously. Four motor vehicle exhaust is not inIn particular the greening of urban areas, it is necessary to carefully select the species suited to local soils, reflecting ... ... Features also allow for the evergreen trees, so that people walking in the shade. On one handTo expand green areas, improve planting quality fuss; but also to focus on simplicity and generosity of the green on the other hand, to enhance the Visual effect of green scale. Big green landscape according to the terrain the moderate, plant communities in natural, varied colors, flowers and clear principles, reflect the level, color and seasonal change. 图2 停车场入口处天线旁测得的信号频谱 至此，终于真相大白:干扰是由一个公众移动室内覆盖系统发出的。 干扰重组 根据现场布线，可画出地下停车场信号覆盖系统的示意图(如图3所示)。由图3可知，系统主要由直放站、施主天线和重发天线组成。 图3 地下停车场室内覆盖系统框架 直放站为双向功率放大器，它把施主天线接收到的基站下行信号放大后经重发天线发给移动台，同时把移动台收到的上行信号放大后经施主天线发向基站天线。图3为三个独立的系统，三根施主天线分别指向附近移动、联通的G网及联通的C网基站，分别接续移动、联通的G网及联通C网的信号，覆盖信号盲区的地下停车场。 直放站工作时，它产生的热噪声电平在基站接收机输入端等效为: NBTS-R=KTB+NFR+GR-EDoPL (1)。 式(1)中:NFR为直放站噪声系数;GR为直放站增益;EDoPL为有效施主路径损耗，它由基站的馈线接头到直放站施主天线端口的所有增益和损耗组成。 NBTS-R叠加到基站接收机本身的热噪声电平中。当其大于GSM系统允许的最大干扰电平时，就会对其产生干扰;若过大时，会湮没小区内其它移动台的正常上行信号，甚至阻塞基站，使信噪比降低，BTS接收灵敏度下降，出现掉话等情况。本案例就是由于联通G网直放站调校不良以致底噪过高，干扰了上行信号，使附近区域的手机接入困难或掉话。 GSM基站接收机噪声电平为-116 dBm，载干比(C/I)为9 dB ，允许的最大干扰电平大致为-125 dBm，所以，我们要求直放站作用于基站接收前端的噪声电平小于-125 dBm。为不对源站产生干扰，在源站和直放站位置已确定的情况下，直放站正式投入使用前，必须进 第Details of green to introduce "the art of bonsai" concept, plant morphology, leaf color, aromas to create different moods and c 3 页 共 5 页创建时间:2007-1-18 15:08:00 harms. (B) improving air pollution prevention and control. …… Air pollution sources in the four areas, a dust pollution and industrial enterprises of coal-burning pollution. A significant proportion of gypsum, stone processing enterprises and use of glass furnace standards of environmental protection facilities. Second, poor dust control, wide range of construction dust, road dust capacity. Three is to build coal-fired boilers in the region, particularly within the city's outdoor barbecue gas discharge seriously. Four motor vehicle exhaust is not inIn particular the greening of urban areas, it is necessary to carefully select the species suited to local soils, reflecting ... ... Features also allow for the evergreen trees, so that people walking in the shade. On one handTo expand green areas, improve planting quality fuss; but also to focus on simplicity and generosity of the green on the other hand, to enhance the Visual effect of green scale. Big green landscape according to the terrain the moderate, plant communities in natural, varied colors, flowers and clear principles, reflect the level, color and seasonal change. 行现场测试，并对覆盖进行系统调整。根据式(1)，可调节的参数有GR和EdoPL。为减小到达基站的热噪声电平，可降低直放站增益GR或加大EDoPL，使NBTS-R满足小于-125 dBm的条件。 干扰信号查寻过程问 题 快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题 分析 (1)为什么我们转了两天，无论是ESMB/DDF190监测/测向设备还是E4407B频谱分析仪，均收不到干扰信号, 分析:图4为联通基站的周围环境平面示意图。图中，施主天线为定向八木天线，有较好的方向性。当它指向相应基站时，信号传输就有大致固定的空间路径，而且范围较窄;另外，在传输过程中，信号受到旁边的山丘及前方厂房建筑物的阻挡而衰减，在路径之外固然收不到信号或信号相当微弱;即使在路径经过之处，若接收点与施主天线不在视距之内，信号幅度也会大打折扣甚至完全消失，所以接收不到。 图4 基站周围环境平面示意图 (2)从频谱图看，直放站的工作频率范围为885 MHz,915 MHz(上行)，作为宽带放大器，覆盖联通及移动的上行信号频段，但为什么中国移动的基站没有受到干扰? 分析:直放站为宽带放大器，频率范围涵盖移动、联通两大运营商的上行工作频段。当两者的G网共站址时，同时受到干扰的可能性非常大。除非施主天线没对准基站天线，或两者的覆盖区不同，所以天线的朝向不同。当施主天线刚好对着基站天线的旁瓣而非主瓣时，接收增益下降，可折合为EDoPL增大， NBTS-R减小，故干扰程度减弱。 另外，该地下停车场覆盖系统由3个独立的分系统组成，若两者G网共站址，则没必要设3个子系统，两个就足够了。只要调校好系统，就可较好实现直放站与基站两者之间的信号传输。可见，两者并不是共站址的(事后翻查资料，也证实了这一点)。由于不共站址，同时Details of green to introduce "the art of bonsai" concept, plant morphology, leaf color, aromas to create different moods and charms. (B) improving air pollution prevention and control. …… Air pollution sources in the four areas, a dust pollution and industrial enterprises of coal-burning pollution. A significant proportion of gypsum, stone processing enterprises and use of glass furnace standards of environmental protection facilities. Second, poor dust control, wide range of construction dust, road dust capacity. Three is to build coal-fired boilers in the region, particularly within the city's outdoor barbecue gas discharge seriously. Four motor vehicle exhaust is not inIn particular the greening of urban areas, it is necessary to carefully select the species suited to local soils, reflecting ... ... Features also allow for the evergreen trees, so that people walking in the shade. On one handTo expand green areas, improve planting quality fuss; but also to focus on simplicity and generosity of the green on the other hand, to enhance the Visual effect of green scale. Big green landscape according to the terrain the moderate, plant communities in natural, varied colors, flowers and clear principles, reflect the level, color and seasonal change. 施主天线具有方向性，所以当移动的基站偏离其传输路径时，信号较弱甚至没有，因而联通的该直放站并没有干扰到移动的基站。而联通的C网上行频率为825 MHz,835 MHz，与G网的相去甚远，构不成干扰。 总结 初级经济法重点总结下载党员个人总结TXt高中句型全总结.doc高中句型全总结.doc理论力学知识点总结pdf 与体会 (1)干扰排查时，最好能与通信运营商的技术人员紧密配合，加强交流沟通。因为只有他们才能与中心机房很好地联络，及时掌握一些基站工作参数及统计数据的现况，如RSSI等，这些数据可以较好地指导干扰查处工作，并能了解具体受干扰的扇区，缩小查找范围，使工作更有目标性和针对性。另外，他们还能比较方便地带领我们出入一些基站机房——这其中很多是租借的私人物业。 (2)在基站周围测不到信号但干扰仍然存在时，应考虑去安装基站天线的天台附近测试，因为即使在下边某处收到干扰信号，该干扰信号也未必会影响到该基站、该扇区。这一方面是由于路径衰减，另一方面该干扰信号可能是定向信号，对基站接收天线而言，可能存在较大的方向性衰减。不管是哪种原因，只要衰减量足够大，使信号小于BTS最大的可允许干扰电平，就不会构成影响。所以，这种情况下要以基站天线附近收到的信号为准。当牵涉到具体某一扇区受干扰时，应弄清与该扇区相对应的天线及其朝向，并选择该方向对干扰信号进行测向。 (3)建立基站、直放站资料数据库。鉴于施主天线主波瓣宽度较窄，除在受干扰基站扇区的天线旁边外，附近可能很难再找出一个主波瓣内的制高点再测向交叉定位。另外，由于手持测向天线频带宽、方向图不够尖锐，所以测向精度不是很高。在主波瓣内即使能找到另一个制高点，也可能由于两点之间距离较近、示向线夹角较小而使交出的点误差较大。所以，查找干扰时，可能会以一点测向，然后沿测向示向线追查的方式进行。显然，这不是一个最佳的方法。若有如直放站布点及工作参数等庞大的资料库作后盾，则可减小工作的盲目性，大大缩短排查干扰所需时间。 (4)建立在用设备周期检测制度。干扰的查寻实际上是对未知信号源(发射机)的发射特性的远场测试，要做到对特定设备的无线参数心中有数，很有必要推行对在用或拟用的发射设备(这里是直放站)进行周期性检测的制度。这一方面可以杜绝劣质、不合格设备投入使用或继续使用;另一方面为上述的台站数据库收集原始资料，同时也是从源头上防止干扰的必要举措。 结语 干扰的排查 表 关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf 面上是一项技术工作，实际情况却并不完全是这样，还有许多技术外的东西起着主导性的作用。精细的管理、完善的台站资料数据库，可以使根据现象结合资料线索从理论上推断干扰源地点成为可能。技术上的查找只是查干扰过程中初步找准大方向后的一个环节，起到验证和查实的作用。尽管最终仍由其断论，但如有强有力的数据库支持，干扰查找往往能事半功倍，整项工作技术环节上的耗时会大大减少。 第Details of green to introduce "the art of bonsai" concept, plant morphology, leaf color, aromas to create different moods and c 5 页 共 5 页创建时间:2007-1-18 15:08:00 harms. (B) improving air pollution prevention and control. …… Air pollution sources in the four areas, a dust pollution and industrial enterprises of coal-burning pollution. A significant proportion of gypsum, stone processing enterprises and use of glass furnace standards of environmental protection facilities. Second, poor dust control, wide range of construction dust, road dust capacity. Three is to build coal-fired boilers in the region, particularly within the city's outdoor barbecue gas discharge seriously. Four motor vehicle exhaust is not inIn particular the greening of urban areas, it is necessary to carefully select the species suited to local soils, reflecting ... ... Features also allow for the evergreen trees, so that people walking in the shade. On one handTo expand green areas, improve planting quality fuss; but also to focus on simplicity and generosity of the green on the other hand, to enhance the Visual effect of green scale. Big green landscape according to the terrain the moderate, plant communities in natural, varied colors, flowers and clear principles, reflect the level, color and seasonal change.