The Negotiated Rate Is Low After a WDS Link Is Established
Symptom
The negotiated rate is low after a WDS link is established.
Possible Causes
- The signal strength of the link is incorrect.
- AP antennas are not properly installed.
- The distance parameter is incorrectly configured.
- Interference from other devices exists.
- The RTS-CTS function is not configured.
Troubleshooting Procedure
- Check whether the WDS link signal strength is weak.
[AC-wlan-view] display wlan wds link all Rf : radio ID Dis : coverage distance(100m) Ch : channel Per : drop percent(%) TSNR : total SNR(dB) P- : peer WDS : WDS mode Re : retry ratio(%) RSSI : RSSI(dBm) MaxR : max RSSI(dBm) --------------------------------------------------------------------------------------------------------------- APName P-APName Rf Dis Ch WDS P-Status RSSI MaxR Per Re TSNR SNR(Ch0~2:dB) --------------------------------------------------------------------------------------------------------------- 8038-bc1b-8820 ap-yuan 1 3 161 leaf normal -31 -29 83 0 62 57/56/59 ap-yuan 8038-bc1b-8820 1 10 161 root normal -35 -34 0 0 61 56/57/55 --------------------------------------------------------------------------------------------------------------- Total: 2
If the RSSI of the WDS link between a root AP and a leaf AP is lower than –75 dBm, the negotiated rate after the WDS link is established is low. To increase the RSSI of the WDS link, increase the transmit power of the APs or shorten the distance between the root AP and leaf AP.
If the configured power does not reach the maximum value, configure the maximum power.<AC> system-view [AC] wlan [AC-wlan-view] ap-id 25 [AC-wlan-ap-25] radio 1 [AC-wlan-radio-25/1] eirp 127 [AC-wlan-radio-25/1] display this # radio-5g-profile huawei vap-profile huawei wlan 1 wds-profile huawei-root wds-whitelist-profile huawei channel 20mhz 161 erip 127 coverage distance 10 # return
- Check whether AP antennas are installed correctly.
Outdoor APs with external antennas are generally used in a WDS system. If the negotiated rate is low after a WDS link is established, check whether the external antennas are correctly installed and antenna angles are correct. This is because external antennas and antenna angles affect the RSSI of the WDS link and the negotiated rate.
When a WDS network is deployed for service backhaul, use antennas based on the following rules:
- When the backhaul distance is shorter than or equal to 2 km, use antennas with the gain of 18 dBi to ensure that no bandwidth loss occurs on backhaul links.
- When the backhaul distance is longer than 2 km and shorter than or equal to 3 km, use antennas with the gain of 23 dBi to ensure that no bandwidth loss occurs on backhaul links.
- When the backhaul distance is longer than 3 km, use antennas with the gain of 28 dBi to ensure that no bandwidth loss occurs on backhaul links.
If the rate of an outdoor AP is low because no antenna is installed, you are advised to install an antenna and then perform the test. In addition, you are advised to install a correct antenna on each antenna port to ensure the link setup rate.
If antennas have been installed, check whether the antennas are correctly installed. For example, check whether the antenna ports are tightened, whether 2.4 GHz and 5 GHz antennas are installed in the correct positions, and whether the antennas are aligned. You can check whether an antenna is aligned by referring to Antenna Alignment.
- Check whether the WDS distance parameter is properly configured.
# Check the radio coverage distance parameter.
<AC> display ap config-info ap-id 1 Radio 0 ...... Coverage distance(100 m) : 3 ...... Radio 1 ...... Coverage distance(100 m) : 3 ......
# Adjust the improper coverage distance parameter settings. For example, if the actual radio coverage distance between the root AP and leaf AP is 600 m but the radio coverage distance parameter is set to 300 m, you need to change the radio coverage distance parameter to 600 m by running the following commands:
[AC-wlan-view] ap-id 25 [AC-wlan-ap-25] radio 1 [AC-wlan-radio-25/1] coverage distance 6 [AC-wlan-radio-25/1] display this # radio-5g-profile huawei vap-profile huawei wlan 1 wds-profile huawei-root wds-whitelist-profile huawei channel 20mhz 161 coverage distance 6 # return
- The unit of the radio coverage distance parameter is 100 m. For example, if the configured value is 5, it indicates 500 m.
- The radio coverage distance parameter needs to be configured on both root APs and leaf APs.
- Check whether any interference from other devices exists.
The negotiated rate after a WDS link is established is affected by the air interface environment. If the interference on the air interface is severe, the negotiated rate is low.
Log in to the AC and check the AP channel utilization to determine whether the interference on the air interface is severe.[AC--wlan-view] display radio ap-id 25 CH/BW:Channel/Bandwidth CE:Current EIRP (dBm) ME:Max EIRP (dBm) CU:Channel utilization ----------------------------------------------------------------------- AP ID Name RfID Band Type Status CH/BW CE/ME STA CU ----------------------------------------------------------------------- 25 ap-yuan 0 2.4G bgn on 8/20M 29/29 1 21% 25 ap-yuan 1 5G an11ac on 165/20M 23/30 0 4% ----------------------------------------------------------------------- Total:2
If the channel utilization of an AP is greater than 50%, the interference on the air interface is severe. Change the AP's working channel to a channel with less interference to reduce the channel utilization.
- Change the AP's working channel to a channel with less interference.
[AC-wlan] ap-id 25 [AC-wlan-ap-25] radio 1 [AC-wlan-radio-25/1] channel 20mhz 157 [AC-wlan-radio-25/1] display this # radio-5g-profile huawei vap-profile huawei wlan 1 wds-profile huawei-root wds-whitelist-profile huawei radio disable channel 20mhz 157 eirp 127 coverage distance 6 # return
It is recommended that APs be configured to work on channels with less interference or non-overlapping channels.
- Search for and remove interference sources.
- Change the AP's working channel to a channel with less interference.
- Check whether RTS-CTS parameters are configured.
[AC-wlan-view] display radio-5g-profile name wj ------------------------------------------------------------ ...... RTS-CTS-mode : CTS-TO-SELF RTS-CTS-threshold : 2347 ......
The following RTS-CTS operation modes are supported:
- In rts-cts mode, an AP sends an RTS frame before sending data to a STA. After receiving the RTS frame, all the devices within the coverage of the AP do not send data within the specified time. Upon receiving the RTS frame, the STA sends a CTS frame. This ensures that all the devices within the coverage of the STA do not send data within the specified time. Using the rts-cts mode to avoid conflicts involves transmission of two frames (RTS and CTS frames), increasing the overhead.
- In cts-to-self mode, an AP sends a CTS frame with the AP's own address as the receiver address (RA) before sending data to a STA. This ensures that all the devices within the coverage of the AP do not send data within the specified time. In cts-to-self mode, an AP only needs to send a CTS frame to avoid channel conflicts in most scenarios. However, if there is a device within the STA's coverage area but not within the AP's coverage area, a channel conflict may still occur.
Compared to the rts-cts mode, the cts-to-self mode reduces the number of control frames sent on the network. In some cases, however, a channel conflict may still occur when hidden nodes do not receive the CTS frame from the AP. Therefore, the rts-cts mode is more effective in avoiding channel conflicts than the cts-to-self mode. Configure an RTS-CTS mode based on site requirements.
RTS-CTS threshold: If APs implement RTS/CTS handshakes each time before sending data, the channel bandwidth will be consumed by too many RTS frames. You can set an RTS-CTS threshold to specify the length of data frames to be sent. When the length of data frames to be sent by an AP is shorter than the RTS-CTS threshold, no RTS/CTS handshake is implemented.
Run the following commands to set the RTS-CTS operation mode to rts-cts and set an RTS-CTS threshold (with a 5 GHz radio profile as an example):
[AC-master-wlan-view] radio-5g-profile name huawei [AC-master-wlan-radio-5g-prof-huawei] rts-cts-mode rts-cts [AC-master-wlan-radio-5g-prof-huawei] rts-cts-threshold 100 [AC-master-wlan-radio-5g-prof-huawei] display this # rts-cts-threshold 100 rts-cts-mode rts-cts # return
RTS-CTS needs to be configured for both root APs and leaf APs.
- Collect fault information.
- Check AC version information.
[AC-diagnose] vrbd
- Check the AC configuration.
<AC> display current-configuration
- Check AP version information.
[Huawei-diagnose] vrbd
- Collect AP information by one click.
<Huawei> display diagnostic-information saved-file <Huawei> display diagnostic-information
- Collect kernel logs of the AP.
[Huawei-diagnose] display kernel-logbuf record-range 1 [Huawei-diagnose] display kernel-logbuf record-range 2 [Huawei-diagnose] display kernel-logbuf record-range 3
If the problem persists for a long time, export logs on the AP or AC as follows.
<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)You must log in to the AP to collect AP information.
In V200R008C10 and later versions, you only need to run the save logfile command. After the logs are saved, use FTP or TFTP to export the log files with the extension name .log and .dblg 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
- Check AC version information.
