某医院WLAN网络终端漫游问题处理经验案例
一、组网
医院使用AC为WX5004,AP为WX2620-AGN,AP通过天线(ANT-2503C-M3)释放信号,天线部署在病房走廊,覆盖四个病房;终端手机为Moto ME525+,手机系统为安卓2.0.3(手机支持的最高版本),医院根据手机终端定制了护士查房系统和医生查房系统,依靠我司设备搭建的WLAN网络,查询病人相关数据。
二、问题描述
医院使用WLAN网络构建两套系统:医生查房系统和护士查房系统,医生查房时使用笔记本电脑(无线网卡灵敏度相对较好),医生查房系统目前未正式使用,用笔记本电脑测试效果很好;护士使用Moto Me525+手机查房,护士查房使用WLAN网路时,发现如下问题:
1、 手机搜索到AP信号比较弱;
2、 从护士站移动到病房出现断线,一段时间之后会自动连接或者需要手动断开重新连接;
三、问题分析
1、终端收到AP信号弱分析
(1)AC开启自动功率调整,部分AP发送功率偏低;通过分析AC日志发现AP发送功率不断浮动,AP发送功率明显偏低:
%Aug 15 07:43:22:819 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 53, RadioId 2 from power 10 dBm to power 7 dBm.
%Aug 15 07:43:22:819 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 204, RadioId 2 from power 19 dBm to power 16 dBm.
%Aug 15 07:43:22:819 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 236, RadioId 2 from power 16 dBm to power 19 dBm.
%Aug 15 07:43:22:819 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 46, RadioId 2 from power 13 dBm to power 16 dBm.
%Aug 15 07:43:22:819 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 214, RadioId 2 from power 19 dBm to power 16 dBm.
%Aug 15 07:43:22:819 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 48, RadioId 2 from power 10 dBm to power 7 dBm.
%Aug 15 07:43:22:818 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 216, RadioId 2 from power 19 dBm to power 16 dBm.
%Aug 15 07:43:22:818 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 32, RadioId 2 from power 10 dBm to power 13 dBm.
%Aug 15 07:43:22:818 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 41, RadioId 2 from power 10 dBm to power 13 dBm.
%Aug 15 07:43:22:818 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 202, RadioId 2 from power 16 dBm to power 19 dBm.
%Aug 15 07:43:22:818 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 227, RadioId 2 from power 16 dBm to power 19 dBm.
%Aug 15 07:43:22:818 2012 wx5004 WMAC/6/WMAC_POWER_CHANGE: Power change for APID 56, RadioId 2 from power 7 dBm to power 10 dBm.
由此判断AP开启动态调整功率,导致部分AP发射功率偏低;
(2)AP未切换使用外置天线,AP放置在天花板内,通过连接吸顶天线发射无线信号,检查配置发现AP未切换使用外置天线,AP使用内置天线发送信号,终端接收时明显偏低;
2、终端异常断线分析
护士查房时随机出现手机异常掉线,通过不断模拟情况发现掉线规律,AP1、AP2、AP3线性部署,终端接入时连接AP1,突然移动到AP3下,终端5s之后感觉到所连的AP1信号变弱,弱到无法接入,这时终端显示断开无线连接,通过debug信息分析(搜索测试MAC)发现如下规律:
? 终端断开前最后一个报文
=====================================================================
*Aug 16 09:46:56:973 2012 wx5004 WMAC/7/FRAME : Frame received from station... MAC address : 3c43-8e65-94e4 #测试终端MAC地址
*Aug 16 09:46:56:973 2012 wx5004 WMAC/7/FRAME : Frame type received : Data frame
*Aug 16 09:46:56:974 2012 wx5004 WMAC/7/FSM : Station state : Running
*Aug 16 09:46:56:974 2012 wx5004 WMAC/7/FRAME : Data frame subtype : Null frame received
=====================================================================
? 再次收到终端数据报文
=====================================================================
*Aug 16 09:47:06:627 2012 wx5004 WMAC/7/FRAME : Frame received from station... MAC address : 3c43-8e65-94e4
*Aug 16 09:47:06:627 2012 wx5004 WMAC/7/FRAME : Frame type received : Authentication
*Aug 16 09:47:06:627 2012 wx5004 WMAC/7/FSM : Station state : Running
*Aug 16 09:47:06:628 2012 wx5004 WMAC/7/EVENT : Authentication response sent with status code 0
*Aug 16 09:47:06:628 2012 wx5004 WMAC/7/FRAME : Dot11 frame sent to AP
*Aug 16 09:47:06:628 2012 wx5004 WMAC/7/EVENT : Authentication for open system successful
*Aug 16 09:47:06:628 2012 wx5004 WMAC/7/FSM : Station state : Running
*Aug 16 09:47:06:634 2012 wx5004 WMAC/7/FRAME : Frame received from station... MAC address : 3c43-8e65-94e4
*Aug 16 09:47:06:634 2012 wx5004 WMAC/7/FRAME : Frame type received : Re-association
*Aug 16 09:47:06:634 2012 wx5004 WMAC/7/FSM : Station state : Running
*Aug 16 09:47:06:635 2012 wx5004 WMAC/7/EVENT : Station 3c43-8e65-94e4 trying to connect again when security association is already completed
*Aug 16 09:47:06:635 2012 wx5004 WMAC/7/EVENT : Station 3c43-8e65-94e4 has not included PMKID in assoc request
*Aug 16 09:47:06:635 2012 wx5004 WMAC/7/EVENT : Add mobile (3c43-8e65-94e4) sent
*Aug 16 09:47:06:635 2012 wx5004 WMAC/7/EVENT : Re-association response sent with status code 0
*Aug 16 09:47:06:636 2012 wx5004 WMAC/7/FRAME : Dot11 frame sent to AP
*Aug 16 09:47:06:636 2012 wx5004 WMAC/7/TIMER : State timer created
*Aug 16 09:47:06:636 2012 wx5004 WMAC/7/EVENT : Notifying Driver regarding station
*Aug 16 09:47:06:637 2012 wx5004 WMAC/7/EVENT : ACK received for association response
=====================================================================
通过debug信息发现终端在离开前最后一个报文,在设备上还存在终端接入表项,这个时候看到终端显示无线网络已经断开;当AP再次收到终端发送的报文时,终端却发送接入的全过程,知道关联成功之后,终端才继续数据通信。
综合以上debug信息和手机断线现象,可以推论由于终端漫游灵敏度低,当终端位置移动但未及时漫游,终端将认为自己已经下线,然后等待12s之后重新发起认证,重新接入无线网络,通过对比测试小米1.0和Iphone 4均不存在该问题,由此定位为终端问题。
四、解决方法
现场收集相关信息已分析清楚当前网络存在问题,针对相关网络做如下优化:
1、AP固定发射功率
2、AP切换使用外置天线
3、重新规划无线信道
4、开启二层隔离
5、关闭低速率
优化WLAN网络之后,无线查房系统已可以正常使用,同时规划医生查房系统在5G频段,护士查房系统为2.4G频段,减少相互之间干扰。
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