Strongly fluctuating WiFi download data rate

baba

I have a strongly fluctuating WiFi download data rate. It can be reproduced with different devices. See the video in the attachment. Internet over WiFi is not usable like this. Devices are USG Flex 200 and multiple NWA110AX. Nebula zyxel support access is enabled.

This problem occurs only at Download and not at Upload. The device is not moved during the test. The download rate is stable via network cable.

Video Screenrecording: https://streamable.com/eujl3y

Thanks a lot!

Zyxel_Judy

Hi @baba ,

I would recommend conducting the Speedtest on various servers or even trying out different platforms. Additionally, you can use a different device, excluding the iPhone, to perform the test, such as laptop, tab, etc. This could help to determine if the issue is server-specific/ platform/ end device.

Furthermore, we found that one AP in one site is running in limit speed mode that link at 100M only, which usually occurs due to cable quality, and led to the unstable connection, too. Please replace the Ethernet cables for your AP with certification guarantee, and change connected port on the switch/ gateway that the AP connected to.

In case, the issue of download speed fluctuations still recurs when tracking on the several flatforms, could you please share with us any other specific issues you're encountering while using WiFi, the time you did the test and the SSID/ AP name that client connected to. We’ll try to check whether any abnormal the event logs when you testing.

baba

Hi @Zyxel_Judy!

Sorry for the late reply, it was very hard to narrow down the error. I can say the following for sure:

* The above site is not affected, but thanks for pointing out the limited speed at ap-upstairs.
* It doesn't matter which speedtest I use, that's not the problem.
* Only the ap-floor1-hall40 in Site Home is (probably) affected.
* The problem occurs with different clients (seen on iOS and Andorid) (main test device is still iPhone 13 Pro with iOS 16.1.1)
* WiFi data rate is not affected and is ~300-400Mbits/s (iperf3) even while the problems occur
* Affected is (as seen in the video) only the download and not the upload speed
* After a disconnect and reconnect, it works again for some time

Here are some times where the problem occurred:
07/07/2023 9:37 AM
07/07/2023 9:25 AM
07/02/2023 20:36 PM
07/02/2023 20:26 PM
06/19/2023 16:26 PM

EDIT:

07/10/2023 16:27 PM iPhone 13 Pro iOS 16.1.1, iPhone X iOS 16.5.1

7/11/2023 18:07 PM

7/11/2023 19:00 PM

Best,

baba

Zyxel_Judy

Hi there,

When performing speed tests within the intranet (iPerf), the communication path between the client and the server has fewer hops. For example, wireless client device connecting to the SSID, and acting as a server's laptop may have a direct link to the LAN port of the AP or connect to a switch. However, when conducting speed tests over the internet, the network path may involve routers, hops, and the ISP's network, which introduces more variables that can affect the stability of the speed.
On the other hand, you may consider checking the quality of your network cables and possibly relocating the ap-floor1-hall40 to see if needed.

Related to the configuration, you can consider the following steps:

Adjust deployment selection and maximum output power: based on the number of APs or configuring the radio power on the 5GHz band to be at least 5dBm higher than the 2.4GHz band. This can help optimize the wireless signal strength and coverage.

Change AP channel settings: check the channel settings of your APs and ensure that they are set to channels with minimal interference from other neighboring networks.

Adjust WLAN Rate Control: set up the basic transmission rate of AP.

Enable broadcast/multicast storm control: can prevent network flooding and improve overall network stability.

baba

Hi @Zyxel_Judy ,

I have done and found out the following points and ask you to look into the logs and tell me how I can look into the logs while these problems occur. Zyxel support access is activated in Nebula.

• I have replaced the cable and the switch
• It is independent of the location of the access point ap-floor1-hall40. Also it does not matter how big the distance between client and access point is
• The whole setup worked normally until 6-8 weeks ago. Nothing was changed in software or hardware except for a software update on the NWA100AX after the problems occurred
• When these problems occur, the Internet connection works normally on all other access points and via cable
• I have tried different WiFI channels, that does not solve the problem either
• The maxmimum ouput power has been limited to 15dBm at 2.4Ghz for a long time and is therefore within your 5dBm range

I've put a lot of hours into finding the problem and would love for you guys to take another look at it. As I said, nothing was changed, the problem occurred overnight. The network itself is otherwise stable. All 7 other access points are working normally. Also all wired clients have no problems.

Video reupload:

IMG_3188.MOV.zip

The error pattern is always the same, no matter which client and which speedtest is used. First, the download rate increases to maximum speed and then it drops sharply. The upload speed is permanently correct.

Thanks!

Best,
baba

Zyxel_Judy

Hi @baba ,

We're trying to investigate your issue. However, we require some additional information.

Please check your Community inbox for further details.

Thank you.

baba

Hi @Zyxel_Judy,

I've sent you all necessary additional information.

Thank you!

Best baba