In Cloud AP Scenarios, STAs Receive Weak Signals
Symptom
In cloud AP scenarios, STAs receive weak signals.
Possible Causes
- The actual transmit power of the AP is low.
- If the AP uses external antennas, the antennas are not properly secured or not installed.
- There are obstacles, such as walls and folding screens, between the STA and AP.
- The STA is connected to a remote AP.
- The STA is faulty.
Troubleshooting Procedure
- Check whether the actual transmit power of the AP is low.
- Optional: Check whether the transmit power of the AP meets user requirements on iMaster NCE-Campus.
# Log in to iMaster NCE-Campus, choose Design > Device Management, select the AP to be queried, and click RF to view the transmit power of the AP.
- Check whether the transmit power of the AP is correct.
# Log in to the AP using the CLI tool on the Device Management page of iMaster NCE-Campus.
In V200R019C00 and earlier versions, run the display wifi tx-power radio radio-id command in the diagnostic view on the AP to check the transmit power of the AP.
[AP-diagnose] display wifi tx-power radio 1 ================================================================================ 11a |Speed(Mbps) 6 9 12 18 24 36 48 54 |------------------------------------------------------------------------ |Power(dBm) 21 21 20 20 18 18 18 18 ================================================================================ ht20 |Speed mcs0 mcs1 mcs2 mcs3 mcs4 mcs5 mcs6 mcs7 |------------------------------------------------------------------------ |Power(dBm) 21 20 20 18 18 18 18 17 |------------------------------------------------------------------------ |Speed mcs8 mcs9 mcs10 mcs11 mcs12 mcs13 mcs14 mcs15 |------------------------------------------------------------------------ |Power(dBm) 21 20 20 18 18 18 18 17 |------------------------------------------------------------------------ |Speed mcs16 mcs17 mcs18 mcs19 mcs20 mcs21 mcs22 mcs23 |------------------------------------------------------------------------ |Power(dBm) 21 20 20 18 18 18 18 17 ================================================================================ vht20 |Speed(nss1) mcs0 mcs1 mcs2 mcs3 mcs4 mcs5 mcs6 mcs7 mcs8 mcs9 |------------------------------------------------------------------------ |Power(dBm) 21 20 20 18 18 18 18 17 16 15 |------------------------------------------------------------------------ |Speed(nss1) mcs0 mcs1 mcs2 mcs3 mcs4 mcs5 mcs6 mcs7 mcs8 mcs9 |------------------------------------------------------------------------ |Power(dBm) 21 20 20 18 18 18 18 17 16 15 |------------------------------------------------------------------------ |Speed(nss1) mcs0 mcs1 mcs2 mcs3 mcs4 mcs5 mcs6 mcs7 mcs8 mcs9 |------------------------------------------------------------------------ |Power(dBm) 21 20 20 18 18 18 18 17 16 15 |------------------------------------------------------------------------ |Speed(nss1) mcs0 mcs1 mcs2 mcs3 mcs4 mcs5 mcs6 mcs7 mcs8 mcs9 |------------------------------------------------------------------------ |Power(dBm) 21 20 20 18 18 18 18 17 16 15 ================================================================================ Antenna gain(dBi) : 3 Aggregate gain(dB) : 6In V200R019C10, run the display lmac tx-power radio radio-id command in the diagnostic view on the AP to check the transmit power of the AP.
[AP-diagnose] display lmac tx-power radio 1 ========================================11a====================================== Speed(Mbps) 6 9 12 18 24 36 48 54 --------------------------------------------------------------------------------- Power(dBm) 18 18 18 18 18 18 18 18 --------------------------------------------------------------------------------- ========================================11n====================================== Speed mcs0 mcs1 mcs2 mcs3 mcs4 mcs5 mcs6 mcs7 --------------------------------------------------------------------------------- Power(dBm,HT20) 18 18 18 18 18 18 18 18 --------------------------------------------------------------------------------- ========================================11ac===================================== Speed mcs0 mcs1 mcs2 mcs3 mcs4 mcs5 mcs6 mcs7 mcs8 mcs9 --------------------------------------------------------------------------------- Power(dBm,VHT20) 18 18 18 18 18 18 18 18 17 17 --------------------------------------------------------------------------------- ========================================11ax===================================== Speed mcs0 mcs1 mcs2 mcs3 mcs4 mcs5 mcs6 mcs7 mcs8 mcs9 mcs10 mcs11 --------------------------------------------------------------------------------- Power(dBm,HE20) 18 18 18 18 18 18 18 18 17 17 16 16 ---------------------------------------------------------------------------------
Theoretically, the current transmit power of the AP that can be checked on the AC is calculated using the following formula: Current transmit power = Transmit power of a single AP radio + Combined gain + Antenna gain.
For example, as shown in steps 1 and 2, the current transmit power of the AP with ID 2 displayed on the AC is 30 (the value in the CE field), which is calculated using the preceding formula: Current transmit power (30) = Maximum transmit power of a single AP radio (21) + Combined gain (6) + Antenna gain (3). If the value in the CE field is small, configure the EIRP for the radio. By default, the EIRP value is 127 dBm.
The antenna gain is classified into the typical gain and peak gain. When an AP reports the antenna gain to an AC, the AC determines to use the typical or peak gain based on the AP model and whether authentication is enabled. For some radios of some AP models, the typical and peak gains are the same. In other conditions, the difference between the typical and peak gains of the same radio of the same AP model is no larger than 1 dB.
If no equation can be achieved using the preceding calculation formula, the transmit power of the AP configured on the AC is not properly delivered. You can check the transmit power of the AP in the configuration area of the corresponding AP radio. If the transmit power of the AP is not properly delivered, contact the technical support personnel.
- Check whether the transmit power of the AP configured on the AC is properly delivered.
In V200R019C00 and earlier versions, run the display wsrv wcfg radio-cfg radio-id command in the diagnostic view on the AP to check the transmit power of the AP in the configuration area of the corresponding AP radio.
[AP-diagnose] display wsrv wcfg radio-cfg 1 -------------------------------------- [RADIO_CFG_TYPE] 0x00: 9a [RADIO_CFG_RATEVAL] 0x00: 00 00 00 00 [RADIO_CFG_CALIBRATEINTERVAL] 0x00: 00 00 [RADIO_CFG_SHORTGI] 0x00: 01 00 [RADIO_CFG_BEACONINTERVAL] 0x00: a0 00 [RADIO_CFG_COUNTRYCODE] 0x00: 9c 00 00 00 [RADIO_CFG_CHBANDWIDTH] 0x00: 00 [RADIO_CFG_CHANNEL] 0x00: 95 00 00 00 [RADIO_CFG_TXPOWER] 0x00: 7f 03 //7f is a hexadecimal number, which can be converted into an EIRP value in a decimal number. 03 indicates the antenna gain. [RADIO_CFG_ADMINSTATE] 0x00: 01 ...
In V200R019C10, run the display umac wcfg radio-cfg radio-id command in the diagnostic view on the AP to check the transmit power of the AP in the configuration area of the corresponding AP radio.
[AP-diagnose] display umac wcfg radio-cfg 1 -------------------------------------- [WPC_RADIO_CFG_ADMINSTATE] 0x00: 01 00 00 00 [WPC_RADIO_CFG_COUNTRYCODE] 0x00: 48 03 00 00 [WPC_RADIO_CFG_WORKMODE] 0x00: 01 00 00 00 [WPC_RADIO_CFG_APNAME] 0x00: 36 30 64 37 2d 35 35 62 35 2d 33 63 30 30 00 00 0x10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [WPC_RADIO_CFG_FREQBAND] 0x00: 01 00 00 00 [WPC_RADIO_CFG_PHY_MODE] 0x00: 06 00 00 00 [WPC_RADIO_CFG_SITE_TYPE] 0x00: 00 00 00 00 [WPC_RADIO_CFG_CHBANDWIDTH] 0x00: 00 00 00 00 [WPC_RADIO_CFG_CHANNEL] 0x00: 34 00 00 00 03 00 [WPC_RADIO_CFG_SHORTGI] 0x00: 00 00 00 00 [WPC_RADIO_CFG_HE_SHORTGI] 0x00: 00 00 00 00 [WPC_RADIO_CFG_ANTENNA_GAIN] 0x00: 03 //03 indicates the antenna gain. [WPC_RADIO_CFG_TXPOWER] 0x00: 1e //1e is a hexadecimal number, which can be converted into an EIRP value in a decimal number. [WPC_RADIO_CFG_UTMOST] 0x00: 01 ...
- Optional: Check whether the transmit power of the AP meets user requirements on iMaster NCE-Campus.
- If the AP to which the STA is connected uses external antennas, check whether the external antennas are correctly installed.
If the external antennas are damaged or incorrectly installed, the signal strength of the AP is affected. For details about how to correctly install antennas, see the WLAN Antenna Quick Start.
- Check whether there are obstacles between the AP and STA.
Walls or other obstacles will attenuate the signal strength received by the STA to some extent. You are advised to remove obstacles or re-plan the network to move the AP to a proper installation position.
The following table lists the signal attenuation caused by typical obstacles.
Obstacle
Thickness (mm)
2.4 GHz Signal Attenuation (dB)
5 GHz Signal Attenuation (dB)
Example
Wooden door
40
3
4
-
Synthetic material
20
2
3
Ceiling
Asbestos
8
3
4
Interior wall and office partition
Glass window
50
4
7
Glass window and flint glass partition
Heavy colored glass
80
8
10
Interior wall and office partition
12 cm brick wall
120
10
20
Exterior wall
24 cm brick wall
240
15
25
Exterior wall
Concrete
240
25
30
-
Armored glass
120
25
35
-
Metal
80
30
35
Office, office partition, elevator, file cabinet, and heating ventilation air conditioning (HVAC) devices
- Check whether the STA is connected to a remote AP.Run the display station {sta-mac sta-mac-address | all | interface interface} command on the AP to check the STAs associated with the AP and the corresponding SSIDs.
<AP> display station all Rf/WLAN: Radio ID/WLAN ID Rx/Tx: link receive rate/link transmit rate(Mbps) --------------------------------------------------------------------------------------------------------------------------- STA MAC Ap name Rf/WLAN Band Type Rx/Tx RSSI VLAN IP address SSID Status --------------------------------------------------------------------------------------------------------------------------- 14a1-4846-1041 area_2 1/1 5G 11ac 173/173 -23 1 21.21.21.71 wlan-ssid Normal --------------------------------------------------------------------------------------------------------------------------- Total: 1 2.4G: 0 5G: 1
If a STA is connected to a remote AP, the signal strength received by the STA is weakened due to the long distance.
In this case, configure the smart roaming function to force the STA to roam from the remote AP to an AP with better signal strength, or lower the transmit power of the remote AP to reduce its interference to the nearby AP. However, the prerequisite for implementing the two methods is that the STA is covered by good signal. If the signal strength is poor, replan the network by adjusting AP positions or deploying more APs to meet the signal coverage requirements.
The following table lists typical transmission attenuation values in different scenarios.
Indoor Semi-Open Scenario
Outdoor Coverage Scenario
Distance (m)
2.4 GHz Path Loss (dB)
5 GHz Path Loss (dB)
Distance (m)
2.4 GHz Path Loss (dB)
5 GHz Path Loss (dB)
1
46
53
50
76.4
84
2
53.5
62
100
84.2
91.9
5
63.5
74
200
92
99.7
10
71
83
300
96.6
104.2
15
75.4
88.3
500
102.4
110
20
78.5
92
800
107.7
115.4
40
86
101
1000
110.2
117.9
- Check whether the STA is faulty.
If the problem persists after you perform the preceding steps, update the NIC drive of the STA or replace the STA.
- Collect fault information.
- Collect operation results of the preceding steps and record the results in a file.
- Collect the AP configuration.
<AP> display current-configuration
- Collect version information about iMaster NCE-Campus.
- Collect operation logs on iMaster NCE-Campus.
On iMaster NCE-Campus, choose System > System Management > Logs > Operation Logs and click Export to export operation logs.
- Collect AP version information.
Check basic AP information on the Device Management page of iMaster NCE-Campus.
- Collect diagnostic information about the AP.
- Collect AP logs.
Download the .dblg and .log files.
