The Received Signal Strength of a STA Is Weak
Symptom
The Wi-Fi signal strength displayed on a STA is weak.
Possible Causes
- The actual transmit power of the connected AP is low.
- If the connected AP requires external antennas, the external antennas are not properly fastened 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.
- Check whether the transmit power of an AP meets user requirements.
Run the display radio { ap-id ap-id | ap-name ap-name } command on the AC to check the current transmit power (the value in the CE field) of the AP and the maximum transmit power (the value in the ME field) supported by the AP.
<AC> display radio ap-id 0 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 ------------------------------------------------------------------------------------ 0 60de-4474-9640 0 2.4G bgn on 6/20M 24/24 0 55% normal 0 60de-4474-9640 1 5G an on 56/20M 25/25 0 3% normal ------------------------------------------------------------------------------------ Total:2
- Check whether the transmit power of the AP is correct.
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 ...
- Check whether the transmit power of an AP meets user requirements.
- 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 incorrectly installed, fastened, or damaged, the signal strength of the STA is affected. For details about how to correctly install antennas, see the WLAN Antenna Quick Start.
If the STA connected to an outdoor AP receives weak signals on a WDS or Mesh network, you can perform antenna alignment on the CloudCampus APP.
- On the CloudCampus APP, open Antenna Alignment tool.
- Touch Bluetooth and log in to the Bluetooth serial port of the target device.
- Touch Start antenna alignment, manually adjust antennas, and observe the RSSI on the APP.
If the RSSI value is higher than the standard value, the progress bar is green, indicating that the alignment effect is good.
- 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 { ap-id ap-id | ap-name ap-name } command on the AC to check the STAs associated with the AP and their corresponding SSIDs.
<AC> display station ap-name area_2 Rf/WLAN: Radio ID/WLAN ID Rx/Tx: link receive rate/link transmit rate(Mbps) ------------------------------------------------------------------------------------- STA MAC Rf/WLAN Band Type Rx/Tx RSSI VLAN IP address SSID ------------------------------------------------------------------------------------- 14a1-4846-1041 1/3 5G 11ac 72/52 -67 100 192.168.100.85 wlan-ssid ------------------------------------------------------------------------------------- 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 long distance.
In this case, you can configure the smart roaming function to force the STA to roam from the remote AP to an AP with better signal strength. You can also reduce the transmit power of the remote AP to reduce the signal interference from the remote AP to the nearby AP. However, the prerequisite for implementing the two methods is that the STA is located in a place with good signal coverage. If the signal coverage is poor, re-plan the network by adjusting the AP installation position or adding more APs to meet the signal coverage requirements.
- 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 AC version information.
[AC-diagnose] vrbd
- Collect AC configuration information.
<AC> display current-configuration
- Collect AP version information.
[Huawei-diagnose] vrbd
- Collect diagnostic information about the AP.
<Huawei> display diagnostic-information saved-file <Huawei> display diagnostic-information
If the problem persists for a long time, run the following commands to export logs on the AP or AC.<fce3-3cb6-47e0> save logfile [fce3-3cb6-47e0-diagnose] save diag-logfile <fce3-3cb6-47e0> cd logfile/ <fce3-3cb6-47e0> dir Directory of flash:/logfile/ Idx Attr Size(Byte) Date Time(LMT) FileName 0 -ro- 1,113,850 Aug 31 2015 11:26:57 2015-08-31.12-29-00.dblg 1 -ro- 1,113,970 Aug 31 2015 19:45:02 2015-08-31.23-14-59.dblg 2 -ro- 1,113,920 May 06 2016 08:42:07 2016-05-06.08-47-07.dblg 3 -ro- 1,113,472 May 11 2016 16:19:54 2016-06-09.17-15-52.dblg 4 -ro- 1,114,104 Jun 14 2016 17:55:56 2016-06-14.18-29-52.dblg 5 -ro- 1,114,031 Jun 14 2016 22:22:06 2016-06-14.22-54-08.dblg 6 -ro- 1,113,835 Jun 17 2016 17:29:24 2016-06-17.18-08-54.dblg 7 -ro- 1,113,843 Jun 17 2016 20:34:50 2016-06-17.20-47-59.dblg 8 -ro- 1,113,743 Jun 22 2016 20:06:19 2016-06-22.20-50-06.dblg 9 -ro- 1,113,271 Jun 28 2016 16:58:37 2016-06-28.19-58-45.dblg 10 -ro- 1,113,494 Jun 29 2016 17:33:23 2016-06-29.18-32-36.dblg 11 -ro- 1,113,824 Jun 30 2016 01:22:38 2016-06-30.02-19-21.dblg 12 -ro- 1,113,773 Jun 30 2016 09:10:31 2016-06-30.10-09-39.dblg 13 -ro- 1,125,418 Jun 30 2016 09:26:03 2016-06-30.12-25-03.log 14 -ro- 1,113,801 Jul 11 2016 09:59:38 2016-07-11.10-13-26.dblg 15 -ro- 1,113,732 Jul 13 2016 15:41:02 2016-07-13.15-54-31.dblg 16 -ro- 1,129,531 Jul 13 2016 19:55:33 2016-07-15.10-37-46.dblg 17 -ro- 1,113,787 Nov 26 2018 21:54:45 2018-11-27.01-02-52.dblg 18 -ro- 1,113,604 Nov 27 2018 22:56:38 2018-11-28.00-20-24.dblg 19 -ro- 1,113,723 Nov 28 2018 07:37:57 2018-11-28.08-40-58.dblg 20 -ro- 1,113,744 Nov 28 2018 15:14:40 2018-11-28.16-10-55.dblg 21 -rw- 384,570 Jul 19 2016 10:07:11 log.dblg 22 -rw- 681,533 Jul 19 2016 10:06:57 log.log 11,144 KB total (1,512 KB free)Log in to the AP to collect AP logs.
In V200R008C10 and later versions, you only need to run the save logfile command to save logs. After the logs are saved, use FTP or TFTP to export .log and .dblg log files in the corresponding time period.
Information collection is mainly performed in the diagnostic view. To enter the diagnostic view, run the following commands.
<Huawei> system-view [Huawei] diagnose
