Data rate change simultaneously

[Junior_Silalahi]

Hi All,

I have an issue on my Access Point WiNG AP7522. 
My data-rate change simultaneously even i don’t move mobile. (I just stay on my desk, but my data-rate change)

[Tomasz · Accepted solution]

Hi,

78 and 104 Mbps are MCSes 4 and 5 for 2x2 MIMO device running on 20 MHz channel with long Guard Intervals. 173.3 and 115.6 Mbps are MCSes 5 and 8 for the same with short Guard Interval (https://mcsindex.net/).

Double check please, is the Guard Interval set to auto for the radio interface? Seems so. Or perhaps your device is jumping between bands? That’s not enough to judge. We’d need to look at some connection details such as from WiNG or your laptop’s cmd ‘netsh wlan show interface’ which shows the channel number so we can tell whether it’s 2.4 GHz or 5 GHz.

MCS 5 is theoretically available for a device at 20 dB SNR in such setup with MCS 4 at 18 dB of SNR (https://d2cpnw0u24fjm4.cloudfront.net/wp-content/uploads/LaminatedCard_MCSValuesforVariousSNR2.pdf),... not a big difference tbh. MCS 8 for 11ac requires at least 29 dB SNR however and that seems to be a stronger jump in RSSI. I’d like to check for some interferences or changing radio environment. More than this, at the end you could see the signal power level bars going one less. Could be the APs are trying to adjust their power between them with Smart RF constantly. Is it enabled or are the channels static?

I wouldn’t bother much unless the user experience under normal operation is fair enough.

Now I have perfect environment at home (nothing around on 5 GHz and no other devices than my AP and the laptop, and nothing moving around) so the datarate doesn’t jump around, but I remember similar tests in the past and I hade similar thing, datarates varying.

Hope that helps,

Tomasz

[Junior_Silalahi]

Hi Tomasz,

Please see this link, https://drive.google.com/file/d/1LnzfWhhyCp9ULsA29jy89JsSK7tRKrJU/view?usp=sharing. I have captured the video for 1 minute, we can see the data-rates change simultaneously.

Regards,

Junior

[Tomasz]

Hi,

How much does it change? It will change all the time but sometimes you may not notice the change, and if the connection is stable the changes might be small.

First thing is, are you testing with 1 AP and 1 client connected to it? Please have in mind moving objects and interferences and some other RF wave effects that may affect received signal strength, and thus SNR, and thus selected datarate.

Please let us know more on your environment to be able to give you any further advice.

Hope that helps,

Tomasz