Case Study: A PDA Goes Offline During Roaming Due to Poor Wireless Signal Coverage

Symptom

A PDA goes offline unexpectedly during roaming, and services are unavailable.

Relevant Alarms and Logs

None

Cause Analysis

Insufficient APs cause poor wireless signal coverage.

Procedure

1. Use a radio signal scanning tool to scan the wireless coverage at the position where the PDA is located.

   According to the displayed result, the signal strength is weak at the position where the PDA is located. Adjust the AP transmit power or deploy more APs.

2. Run the display radio all command to view radio information and check whether the low transmit power of radio signals is caused by incorrect configurations.

   <AC> display radio all 
   CH/BW:Channel/Bandwidth  
   CE:Current EIRP (dBm)  
   ME:Max EIRP (dBm)  
   CU:Channel utilization  
   ST:Status  
   WM:Working Mode (normal/monitor/monitor dual-band-scan/monitor proxy dual-band-scan)  
   ------------------------------------------------------------------------------------  
   AP ID Name            RfID  Band  Type    ST  CH/BW    CE/ME   STA     CU    WM  
   ------------------------------------------------------------------------------------  
   36    xxxx-xxxx-xxxx  0     2.4G  bgn     on  6/20M    25/25   0       0%   normal   
   36    xxxx-xxxx-xxxx  1     5G    an11ac  on  36/20M   26/26   0       0%   normal 
   37    yyyy-yyyy-yyyy  0     2.4G  bgn     on  6/20M    25/25   0       0%   normal   
   37    yyyy-yyyy-yyyy  1     5G    an11ac  on  36/20M   26/26   0       0%   normal
   ------------------------------------------------------------------------------------  
   Total:4

   APs are transmitting radio signals at the maximum transmit power, so the transmit power cannot be increased.

3. Use the station-trace and trace functions to check the uplink signal strength of the STA. It is found that the uplink signal strength of the STA is weak.
   • STA trace information:

     (XXXX-XXXX-XXXX):wstak_sta_lb_move_proc[2260]: Dst Bssid:0000-0000-0000,LDBC move, mode[3], reason[2], RestricTime[10]
     (XXXX-XXXX-XXXX):AC send move msg
     (XXXX-XXXX-XXXX):WUAMK_SmartRoamLowSnrQuickTickOffHandleNew[2444]: quick kick sta for btm [1]times.
     (XXXX-XXXX-XXXX):WUAMK_AssocreqCallChainHandle[886]: Enter:
         radio id    :0
         wlan id     :0
         packet type :association req
         result      :Successful (0)
         reason      :0x0
         sta ability :67
         SFN roam    :0
         SNR        :13

   • Trace information:

     [XXXX-XXXX-XXXX]:[Process:19] [WSTA] Receive STA (Re)associate request message.
      Assoc local:0, AP ID:x, Radio ID:0, Wlan ID:1, Type(1:assoc, 2:reassoc):1, Pmk:0, Wapi IE:22, Bk ID Num:0, SFN Flag:0, Ability:43, 2.4G CHs:0, 5G CHs:0. FT Roam:0, FT Access:0, Rssi:-86......

4. Based on the preceding check results and AP deployment analysis, more APs need to be deployed to fill coverage holes. The problem is solved after more APs are deployed.