Case Study: STAs Encounter Weak Signals or Go Offline Because of the Improper Transmit Power Planning for Properly Deployed APs

Symptom

When APs are deployed in proper positions at a site, STAs still suffer from weak Wi-Fi signals or even go offline.

Relevant Alarms and Logs

None

Cause Analysis

It is preliminarily determined that this problem is caused by poor signal coverage. Check the channel and transmit power of AP radios. The check result shows that the transmit power of AP radios is manually set to 9 dBm, which is too low and causes coverage holes.

Procedure

1. In office scenarios where APs are deployed in a certain order, configure automatic channel and transmit power calibration for AP radios.
   # Enable automatic transmit power selection. By default, automatic transmit power selection is enabled.

   <AC> system-view
   [AC] wlan
   [AC-wlan-view] ap-group name ap-group1
   [AC-wlan-ap-group-ap-group1] radio 0
   [AC-wlan-group-radio-ap-group1/0] calibrate auto-txpower-select enable  //Enable automatic radio power calibration.
   [AC-wlan-group-radio-ap-group1/0] quit
   [AC-wlan-ap-group-ap-group1] radio 1
   [AC-wlan-group-radio-ap-group1/1] calibrate auto-txpower-select enable
   [AC-wlan-group-radio-ap-group1/1] quit
   [AC-wlan-ap-group-ap-group1] quit

2. Manually trigger radio calibration. By default, the radio calibration mode is auto.

   [AC-wlan-view] calibrate enable auto
   [AC-wlan-view] calibrate manual startup
   Warning: The operation may cause business interruption, continue?[y/n]:y

3. Run the display radio all command on the AC to check the radio calibration effect. The command output shows that the AP power is within the normal range.

   [AC-wlan-view] 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
   ------------------------------------------------------------------------------------
   1     area_2  0     2.4G  bgn     on      1/20M    28/28   1        10%   normal
   1     area_2  1     5G    an      on      149/20M  29/29   0        15%   normal
   0     area_1  0     2.4G  bgn     on      6/20M    28/28   1        15%   normal
   0     area_1  1     5G    an      on      153/20M  29/29   0        49%   normal
   ------------------------------------------------------------------------------------
   Total:4

Suggestion and Summary

In most cases, to ensure good network coverage, the received signal strength indicator (RSSI) in WLAN coverage areas must reach -65 dBm or higher. In indoor scenarios where WLANs are deployed mainly to provide cellular coverage, automatic channel and power calibration can be enabled to prevent coverage holes caused by low transmit power or minimize signal interference caused by high transmit power. In outdoor or special scenarios, it is recommended that the transmit power of AP radios be configured based on the WLAN plan.