Issues with Lenovo T470s laptop / Intel 8260 wireless NIC on Meraki MR56 5Ghz

[DanZ]

I've got a strange issue we are seeing.  We have Meraki MR56s deployed with UNII-1, UNII-2, UNII-2 extended, and UNII-3 channels enabled for 5 Ghz.

Most clients are fine but I've got some Lenovo laptops with horrible performance only on APs on UNII-3 channels 149, 153, 157, 161.  *Edit - I have since seen the issue on other channels.  Not sure why it seems to appear on some APs not others.  Only see it on 5 Ghz though.

The specific laptop model seeing issues is a T470.

[PhilipDAth · Accepted solution]

Tease me, and set the WiFi power-saving performance to maximum and see if the issue is still happening.

powercfg /SETDCVALUEINDEX SCHEME_CURRENT 19cbb8fa-5279-450e-9fac-8a3d5fedd0c1 12bbebe6-58d6-4636-95bb-3217ef867c1a 0
powercfg /SETACVALUEINDEX SCHEME_CURRENT 19cbb8fa-5279-450e-9fac-8a3d5fedd0c1 12bbebe6-58d6-4636-95bb-3217ef867c1a 0

Does the spectrum graph show that those APs on those bands have a good amount of free spectrum available?  Perhaps something else is using it.

[DanZ]

Wireless spectrum, interference, and channel utilization on the APs are all good.  My laptop and others are fine on those APs.  I will try adjusting the power-saving on the laptop card.  Good advice.

[DanZ]

I got a T470s to test with.  Plugging in the laptop into power made the issue go away almost instantly.  Also the issue does not seem to be related to UNII-3 channels only.  I see it on an AP on channel 36 as well.  Testing with a user who also had the problem, plugging in the T470s to a power supply also fixed it.  So it does seem related to power save somehow.

[DanZ]

Also changed the Advanced Power Setting for the Power Plan.  The Wireless Adapter Settings > Power Saving Mode > On Battery setting was set to Medium Power Saving.  When I changed it to Maximum Performance, the issue went away instantly while on battery:

So is this some compatibility issue with Meraki and this wireless card when going into Power Saving Mode?  Also, the issue does not seem to happen on all APs.  I will roam and some connections will seem stable.  So I can't say I fully understand why this is happening and if there is anything on the Meraki side that could be at fault here.

[PhilipDAth]

>So is this some compatibility issue with Meraki and this wireless card when going into Power Saving Mode?

No.  With power-saving mode, the client decides to shut down its radio regularly for a period of time, say 100ms.  It tells the AP it is going to power down for the time.  The AP then knows not to transmit data to the client for that period of time.  The client gets to decide how long to keep the radio powered on versus powered off.

This is all in the name of saving battery power.  Different clients use different times.  Those times are not always the same.  For example, the times can be dependent on the battery level, how long the user has been idle, the current data throughput rate, etc.

[DanZ]

That makes sense.  I just don't understand why the issue happens only roaming to some specific Meraki APs.  At first I thought it was based on channels but now it just seems random.  But it's always the same APs on the floor where the issue occurs.

[DanZ]

https://community.meraki.com/t5/Wireless-LAN/MR-27-4-released-plenty-of-fixes/td-p/94876

Bug fixes:

• Interoperability issue with Dynamic SMPS on certain Intel clients would result in poor performance (802.11ax MRs)

I'm running 27.5.1, so it should include this fix.  But this issue sounds very similar.  Our clients were set to Auto SMPS not dynamic.  But we do have 802.11ax MR56s.

[DanZ]

A driver update didn't improve things.  In Medium Power Saving mode the issue still happened when on battery.  But I did find a driver setting that solved the issue as well:  Changing MIMO Power Save Mode from Auto SMPS to No SMPS

Intel site describes that feature as this:

MIMO power save modeMIMO power save mode, also known as spatial multiplexing power save (SMPS) mode, allows the client to save power by keeping one antenna in a receive idle state.

• Auto SMPS (default): The client decides automatically what SMPS mode to apply depends on different conditions.
• Dynamic SMPS: The client keeps only one antenna active. The access point (AP) must send request to send (RTS) packet to trigger the client to wake the sleeping radios/antenna before sending MIMO packets.
• Static SMPS: The client keeps only one antenna active and the AP cannot send MIMO packets to the client.
• No SMPS: The client always keeps all antennas active and the AP can send MIMO packets to the client.

Note	Some legacy APs may have compatibility issue with supporting the SMPS mode and may cause various link quality problems such as low throughput. Change this setting to No SMPS may help to work around the issue.

[PhilipDAth]

I forgot the other obvious thing.  Have you updated the WiFi driver from Lenovo to the latest?

[DanZ]

This did not help on one of the T470s laptops we tried.

[DanZ]

This is what the client pings look like when they are on APs with channels 149, 153, 157, 161.

[DanZ]

The wireless card on these t470s laptops is an Intel Dual Band Wireless-AC 8260.