<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<font face="Tahoma">Thanks for the input, Karl.<br>
<br>
Hopefully someone from Apple is around here and can get some ideas
on how to fix this particular problem set.<br>
<br>
Mark.<br>
</font><br>
<div class="moz-cite-prefix">On 10/31/20 11:37, Karl Auerbach wrote:<br>
</div>
<blockquote type="cite"
cite="mid:aceccbcf-65e6-cbf9-cc31-a496b062f3a5@cavebear.com">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<p>Let me jump in and add a bit more information.</p>
<p>I am not an RF guy - I stopped playing with radios [and TV] in
the days when they used vacuum tubes (yes, really.)<br>
</p>
<p>Many laptops share radio and <span class="q-box
qu-userSelect--text" style="box-sizing: border-box; direction:
ltr;"><span style="font-weight: normal; font-style: normal;
background: rgba(0, 0, 0, 0) none repeat scroll 0% 0%;">antenna
resources between WiFi and bluetooth</span></span>.<br>
</p>
<p>Bluetooth lives on the 2.4ghz band. Wifi presently uses both
that band and also a 5ghz band. <span class="q-box
qu-userSelect--text" style="box-sizing: border-box; direction:
ltr;"><span style="font-weight: normal; font-style: normal;
background: rgba(0, 0, 0, 0) none repeat scroll 0% 0%;">Different
antennas might be used for each.</span></span></p>
<p><span class="q-box qu-userSelect--text" style="box-sizing:
border-box; direction: ltr;"><span style="font-weight: normal;
font-style: normal; background: rgba(0, 0, 0, 0) none repeat
scroll 0% 0%;">I encountered Wi-Fi/Bluetooth contention
issues a couple of years back....<br>
</span></span></p>
<p>My home wifi has (or rather had) distinct SSIDs for Wifi on the
2.4 and 5ghz bands. It was a rough attempt at manual load and
distance balancing.<br>
</p>
<p>(Our house is in a relatively quiet area, RF wise, so there's
not really any seriously competing wi-fi - or for that matter
cell signal, broadcast TV, or FM radio.)<br>
</p>
<p>I began to notice that when I had one of my laptops on the 5ghz
WiFi and was listening to music via some bluetooth speakers that
my remote terminal keystrokes sometimes had that sluggish feel
that is familiar when doing remote terminal command-line stuff
over long paths with a lot of latency/jitter. And at the same
time the music via Bluetooth often broke up or stuttered. There
was a clear correlation between the two problems.<br>
</p>
<p>I had heard from some Linux kernel developers that deep down in
the Linux kernel the simultaneous use of Wifi on a 5ghz channel
and bluetooth on 2.4 causes a lot of thrashing and flogging of
the the radio system. I don't know, but I suspect that as a
result there are queues of outbound traffic waiting for the
radio or <span class="q-box qu-userSelect--text"
style="box-sizing: border-box; direction: ltr;"><span
style="font-weight: normal; font-style: normal; background:
rgba(0, 0, 0, 0) none repeat scroll 0% 0%;">antennas</span></span>
to become operational on the channel they need. I have no idea
what happens to inbound frames when the radio system is tuned
elsewhere - I never measured whether the frames are lost or
delayed.</p>
<p>I suspect similar issues are present in *BSD, MacOS, and
Windows kernels.<br>
</p>
<p>So I did some simple empirical testing to compare life with the
laptop coerced to use an SSID present only on the 2.4ghz band.
The problems went away.</p>
<p>I went back to the laptop, but coerced onto the 5ghz band for
WiFi and, voila, there was trouble.<br>
</p>
<p>I've done this with a MacBook Pro (circa 2015 model) using
various versions of MacOS and with my rather newer Linux laptops
(mostly Dell XPS units with Fedora.) Same sorts of behavior.</p>
<p>These were all i5 based units with 2 or 4 cores - plenty of CPU
power to simultaneously handle an SSH remote console client and
a music player.<br>
</p>
<p>I did not test with mobile phone or tablet platforms.<br>
</p>
<p>I do not know if the single radio issue is the result of cost
savings or some radio-engineering or <span class="q-box
qu-userSelect--text" style="box-sizing: border-box; direction:
ltr;"><span style="font-weight: normal; font-style: normal;
background: rgba(0, 0, 0, 0) none repeat scroll 0% 0%;">antenna
</span></span>issue. I do suspect that these things could
become more troublesome as WiFi 6 and/or 5G start to use some of
the higher frequency allocations around 5.9 and 6ghz.)<br>
</p>
<p>(A few weeks ago we switched our home WiFi to a WiFi 6 [Netgear
Orbi-6] mesh system that does not appear to allow separate SSIDs
for the 2.4 and 5ghz bands, so I can not repeat these tests
without constructing a test network with the now unused access
points. BTW, I did encounter the hell that is known as
"reconfiguring dozens upon dozens of different kinds of IoT
devices to use a different SSID".)</p>
<p>Looking somewhat off topic - it is my sense that we will be
seeing a lot more latency/jitter (and packet resequencing)
issues in the future as radio systems become more agile and as
we begin to use shorter (millimeter) wavelength frequencies with
reduced ability to penetrate walls that, in turn, cause more
frequent access-point transitions (with possibly distinctly
different backhaul characteristics). I've observed that these
things can cause trouble for some TCP stacks and some non-TCP
based VoIP and streaming applications.<br>
</p>
<p> --karl--<br>
</p>
<div class="moz-cite-prefix">On 10/30/20 12:08 PM, Mark Tinka
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:8b8fa0fe-8de0-0cec-5508-f62f0ec82c13@seacom.com"> <font
face="Tahoma">Hi all.<br>
<br>
So I may have fixed this for my end, and hopefully others may
be able to use the same fix.<br>
<br>
After a tip from Karl Auerbach and this link:<br>
<br>
<a class="moz-txt-link-freetext"
href="https://developer.apple.com/forums/thread/97805"
moz-do-not-send="true">https://developer.apple.com/forums/thread/97805</a><br>
<br>
... I was able to fix the problem by disabling Bluetooth. <br>
</font> </blockquote>
</blockquote>
<br>
</body>
</html>