Some of you have asked about the lanyard I use with my WLAN Pi R4. So here is how to make yours.
What does it do?
It allows you to ‘wear’ the R4 while keeping your hands free. You can perform 2.4 GHz, 5 GHz or 6 GHz scanning, spectrum analysis, or packet capture from your Mac.
WLAN Pi R4 with 6 GHz Wi-Fi adapter and 6 GHz spectrum analyser as a remote sensor to WiFi Explorer ProWearable WLAN Pi R4
What parts do I need?
My goal is to use a standard conference lanyard. Use your favourite one or order a custom one with your name or company name. In the UK, I use greencotton on eBay and they have been great.
WLAN Pi R4 lanyard, D rings and bolts
After many iterations, I discovered that these D ring picture holders work best. They are made of metal, of perfect size and readily available. So there is no reason to overengineer this or reinvent the wheel.
Finally, we need two M2.5 x 5 mm bolts to attach the D rings to the bottom of the Waveshare heatsink.
D rings attached to WLAN Pi R4Lanyard attached to WLAN Pi R4
WLAN Pi is primarily a Wi-Fi tool, but occasionally I need an iperf server that would be able to deliver more than 1 Gbps of TCP throughput. In a controlled lab environment, I normally use PoE powered NanoPi R5S. I know the IP address of the iperf server by heart. Outside of the lab, I could really do with a WLAN Pi, its preinstalled software, display, buttons and everything it does out of the box. So the question is: “Can we add 2.5 GbE to WLAN Pi M4?”
M.2 slot to the rescue
WLAN Pi M4 doesn’t have any USB 3 ports. How do we add 2.5 Gbps Ethernet to it? If you don’t mind losing the Wi-Fi adapter in favour of 2.5 GbE mGig port, we can install this 2.5 Gbps Ethernet adapter in M4’s PCIe M.2 slot. It is based on Realtek RTL8125B chipset. I paid £17 for it including shipping to the UK.
To my surprise, it just works*. Yes, I hear you, no one likes these asterisks, do you? 😉 Continue reading, it’s not the end of the story.
WLAN Pi M4 with 2.5 Gbps Ethernet2.5 Gbps full duplex
The underwhelming default driver
Linux (and WLAN Pi image) has a driver for this adapter, but upload speeds, that is from iperf client to WLAN Pi iperf server, are very poor. We are talking 300 Mbps poor.
Poor 300 Mbps upload speed
Install Realtek’s latest driver to fix performance
Downloading, compiling and installing the latest Linux driver from Realtek’s website fixes the performance issue. We get symmetric 2.35 Gbps of TCP throughput with standard packet size.
2.35 Gbps of iperf3 TCP throughput
Installation of this driver isn’t as straightforward as it might look. I ended using vanilla Raspberry Pi OS image instead of the WLAN Pi one. Mainly because it is not easy to get the kernel headers for WLAN Pi image and we need them to be able to compile the new driver.
Summary
Yes, it is possible to achieve 2.35 Gbps symmetric TCP throughput on the WLAN Pi M4 with this adapter. But you should be aware of these facts:
This Ethernet adapter doesn’t fit inside WLAN Pi M4 case
You will have to give up the M.2 Wi-Fi adapter in favour of mGig Ethernet
From software perspective, the Realtek driver that ships in WLAN Pi image doesn’t unlock full performance of this adapter (iperf client pushing traffic to WLAN Pi iperf server). Installing the latest driver isn’t trivial on WLAN Pi.
We, WLAN Pi team, currently don’t support this setup. If you have a use case for 2.5 GbE support on the M4, please let us know.
Since Apple hasn’t published any documentation that would cover this subject, I configured a tri-band SSID on Catalyst 9136 AP. The SSID name is the same for all 2.4 GHz, 5 GHz and 6 GHz bands. Now, what band does iPad prefer?
Setup
Wi-Fi 6E iPad Pro 11-inch (4th generation) running iPadOS 16.1
Catalyst 9136 Wi-Fi 6E AP
C9800-CL cloud controller running 17.9.2
Max transmit power and 80 MHz wide 5 GHz channel
All 3 bands are enabled with manual Power Level 1 (PL1), which forces the AP to use highest permitted Transmit Power.
In this case, the 6 GHz SSID had the strongest absolute signal strength (RSSI) of the 3 bands.
2.4 GHz enabled, PL1
5 GHz channel 36, 80 MHz wide, PL1
6 GHz channel 5, 80 MHz wide, PL1
The iPad prefers the 5 GHz band and joins using this band.
Reduce transmit power on 5 GHz radio
Let’s use the exact same configuration as above and reduce 5 GHz radio’s transmit power to the lowest, Power Level 8 (PL8). Will that make it prefer 6 GHz?
2.4 GHz enabled, PL1 (RSSI on the iPad -31 dBm)
5 GHz channel 36, 80 MHz wide, PL8 (RSSI on the iPad -55 dBm)
6 GHz channel 5, 80 MHz wide, PL1 – strongest absolute RSSI (RSSI on the iPad -30 dBm)
Yes! The iPad Pro prefers 6 GHz every single time. As you can see, the 6 GHz RSSI is 25 dB stronger than the 5 GHz one, which is why (as far as I can tell).
Narrower 5 GHz channel
We are using the the same configuration as in our very first scenario, but 40 MHz we will reduce 5 GHz channel width to 40 MHz.
2.4 GHz enabled, PL1
5 GHz channel 36, 40 MHz wide, PL1
6 GHz channel 5, 80 MHz wide, PL1
Using narrower 5 GHz channel makes the iPad connect using 6 GHz instead.
Disable 5 GHz radio
This time we disable 5 GHz radio and see if 2.4 GHz or 6 GHz wins. I have high hopes for 6 GHz, you?
Now, let forcefully shut the 6 GHz radio on the AP. iPad moves to its only available option, the 2.4 GHz radio and happily lives there. We now reenable the 6 GHz radio. The iPad doesn’t automatically jump back to 6 GHz, although 6 GHz has stronger RSSI. When we disabled iPad’s Wi-Fi radio, and reenable, it connected on 6 GHz.
Make 2.4 GHz stronger than 6 GHz and disable 5 GHz
Can we make 2.4 GHz appealing enough to the iPad so that it would prefer it over 6 GHz? Let’s disable 5 GHz radio, keep max transmit power on 2.4 GHz, and reduce 6 GHz transmit power to the lowest Power Level 8 (PL8).
2.4 GHz enabled, PL1
5 GHz disabled
6 GHz channel 5, 80 MHz wide, PL8
The 6 GHz RSSI (-45 dBm) is now weaker than the 2.4 GHz RSSI (-33 dBm) by 12 dB. Is it good enough reason for the iPad to prefer 2.4 GHz?
Not really. It connected on 6 GHz 2 times out of 3. Once it connected on 2.4 GHz.
Summary
When 80 MHz wide 5 GHz channel is used, the iPad prefers 5 GHz. If 5 GHz drops below a certain threshold, and is much weaker than 6 GHz, it then prefers 6 GHz.
It prefers 6 GHz over 40 MHz wide 5 GHz channel.
It doesn’t use 2.4 GHz unless it has no other option.
Please take these tests with a pinch of salt. Ideally I would repeat each of them 10 or so times. Time is of the essence and I only repeated each test 3 times.
Same as in the iPad test, we are going to test how well the 6 GHz SSID discovery works and learn a thing or two about Pixel 6.
Discovery with 6 GHz only SSID
Let’s configure Catalyst 9136 AP running 17.9.2 release with 6 GHz only SSID. This is the only SSID this AP broadcasts. There are no 2.4 GHz or 5 GHz SSIDs enabled. They only way for the AP to discovery the SSID is to scan the 6 GHz channels. We refer to these methods as in-band discovery.
Reduced Neighbour Report (RNR), which normally uses 2.4 GHz or 5 GHz beacons to tell the client about 6 GHz SSIDs, is not available to us, because we don’t have any 2.4 GHz or 5 GHz SSIDs on the air.
We are using 80 MHz wide 6 GHz channel 7, which uses primary channel 5. That is a Preferred Scanning Channel (PSC), which means that clients should scan it. Our 6 GHz only SSID is called Cisco 6.
6 GHz only SSID is the only one enabledChannel Number allows us to configure the Primary channel
Unfortunately, our Pixel 6 won’t discover the SSID.
No signs of 6 GHz
But, if we move the AP to channel 23, which uses primary non-Preferred Scanning Channel channel 17, the smartphone discovers Cisco 6 instantly! How bizarre.
6 GHz SSID discovered
I went through the “test all lower 6 GHz channels” exercise and here is the outcome.
When I use these primary channels, Pixel 6 will happily discover the 6 GHz only Cisco 6 SSID: 13, 17, 21, 25, 29, 33, 53, 57, 61, 65, 69, 73, 89
Using these primary channels will make the smartphone not discover it: 1, 5, 9, 37, 41, 45, 49, 77, 81, 85, 93
Here is graphical representation of this. Credits to Keith Parsons and the WLAN Pros team for creating this chart.
For the record, on some channels it took little longer to connect.
Changing channel width to 20 MHz, 40 MHz, or 160 MHz did not help with SSID discovery. Which makes me think that Pixel 6 does not scan these channels at all.
Here is what is happening on the 6 GHz channel when we only enable 6 GHz SSID (with no 2.4 GHz and 5 GHz) on the AP. The AP automatically starts broadcasting FILS frames to help the client discover the 6 GHz SSIDs.
6 GHz only SSID plus 5 GHz only SSID and out-of-band discovery
Now the torture is over and we are calling 5 GHz for help. We will use out-of-band discovery.
5 GHz only and 6 GHz only SSIDs enabled
By keeping the 6 GHz only SSID enabled, and adding 5 GHz only SSID, we will allow the AP to tell the Pixel 6 about 6 GHz SSIDs in its 5 GHz beacons. There is a Reduced Neighbour Report (RNR) Information Element (IE) included in the 5 GHz (and 2.4 GHz beacons when we use 2.4 GHz), which is the preferred way of discovering 6 GHz.
RNR IE in 5 GHz beacon informing the client about 6 GHz AP
The client failed discovery on primary channel 5. Let’s use that this time and see if RNR fixes discovery for good.
Yes! We see both SSIDs instantly. By enabling 5 GHz (or 2.4 GHz) SSID with the same or different SSID name, Pixel 6 can now discover all channels. This is the preferred way of discovering 6 GHz networks.
RNR IE in 5 GHz beacons helps the client discover 6 GHz SSIDs
Note: When RNR is active, the AP will automatically stop sending FILS frames and there is no way (and no reason, because RNR is a much better method) to force-enable FILS.
Summary
With 6 GHz only SSID (without 2.4 GHz and 5 GHz), Pixel 6 will only discover it using in-band methods if we use primary channels 13, 17, 21, 25, 29, 33, 53, 57, 61, 65, 69, 73, 89.
After enabling 5 GHz (or 2.4 GHz) SSID, Pixel 6 discovers the 6 GHz SSID by looking into the RNR IE in the 5 GHz (or 2.4 GHz) beacon frames.
I am very happy with how well the 6 GHz discovery using 2.4 GHz or 5 GHz beacons works. It definitely is production ready. The test with only one 6 GHz only SSID on the AP is more of a corner case. Most customers I work with, if not all, will also deploy 5 GHz alongside 6 GHz, so there is absolutely nothing to worry about.
Packet capture or it didn’t happen 😉
Download 2.4 GHz an 5 GHz RNR, 6 GHz FILS, and 6 GHz unsolicited probe response packet captures from here.
Download WLAN Pi Profiler report and packet capture of 5 GHz association request, and also 6 GHz association request. We can see client’s capabilities in these frames.
Bonus: Add second 6 GHz SSID and see how it impacts RNR
Same setup as before, we have 5 GHz only SSID Cisco 5 and 6 GHz only SSID Cisco 6, but this time we add an extra 6 GHz only SSID Cisco 66.
Both 6 GHz SSIDs are now advertised to clients using the RNR IE in 5 GHz beacons.
Both 6 GHz SSIDs advertised using RNR IE in 5 GHz beacons
iPad Pro 11-inch (4th generation) is the first Apple device to feature Wi-Fi 6E. With the significant amount of new 6 GHz spectrum, active scanning for 6 GHz SSIDs is not practical. Other methods are being used instead. Let’s see how iPad Pro actually does it.
As of writing, iPadOS 16.1 is the latest version and that’s the one I am using for all tests here.
The access points in this test are Catalyst Wireless CW9162I-ROW APs running IOS-XE 17.9.2.
iPad Pro ignores FILS Discovery frames on 6 GHz
I am using 6 GHz only SSID (which doesn’t broadcast on 2.4 GHz and 5 GHz) and 80 MHz wide channels.
3 APs in lower 6 GHz in the UK
Of course, there are Beacon frames sent by the APs every 100 ms or so, and there are FILS Discovery frames sent by my APs every 20 ms. These FILS frames are automatically enabled on Catalyst Wireless APs in DNA persona only when the only SSID enabled on the AP is a 6 GHz one (and there is no 2.4 GHz or 5 GHz SSID). At this point, we need FILS, because at that point FILS is the only method for 6 GHz capable clients to discover 6 GHz networks.
6 GHz beacons every 100 ms and FILS frames every 20 ms
Think of FILS frames as of condensed beacons. They are nearly 4 times smaller than Beacons.
FILS frames are smaller than beacons
Unfortunately, the iPad completely ignores the FILS frames, and it has no in-band (6 GHz) method of discovering 6 GHz networks. That results in no visibility of the 6 GHz only SSIDs on the iPad, and we can’t connect.
The 6 GHz only “Cisco 6” SSID isn’t being discovered by the iPad
Airport Utility doesn’t show the 6 GHz only SSID either.
The 6 GHz only “Cisco 6” SSID isn’t being discovered by the iPad
iPad Pro only uses Reduced Neighbour Reports (RNR) for discovery
Let’s keep the 6 GHz only SSID Cisco 6 enabled, and also enable a 5 GHz only SSID called Cisco 5.
If we now do a packet capture on one of the active 5 GHz channels, we will see 5 GHz beacons. These beacons contain Reduced Neighbour Report Information Element, which announces to the client device “there is a 6 GHz AP on channel 5”.
RNR in 5 GHz beacons allows the iPad discover the 6 GHz SSID.
iPad sees both the 5 GHz “Cisco 5” and 6 GHz “Cisco 6” SSIDs
Airport Utility also reports both the 5 GHz only and 6 GHz only SSIDs.
iPad sees both the 5 GHz “Cisco 5” and 6 GHz “Cisco 6” SSIDs
By doing a packet capture on 6 GHz channel number 5, we verify that the AP only sends 6 GHz beacons every 100 ms or so. There are no signs of FILS, which is a good thing. By default, FILS is disabled. It only gets automatically enabled when 6 GHz is the only active band on the AP (with no 2.4 GHz and no 5 GHz SSIDs), because it is then the only method for a 6 GHz capable client to discover a 6 GHz AP.
6 GHz beacons without FILS, because we don’t need FILS, we use 5 GHz RNR
Apparently, the iPad only leverages Reduced Neighbour Reports for 6 GHz SSID discovery.
Does RNR included in 2.4 GHz beacons allow the iPad to discover the 6 GHz only SSID?
Andrew McHale made me to lab this up. Thank you, Andrew 😉 The short answer is yes.
This time we only enable 2.4 GHz only SSID and 6 GHz only SSID and verify that we can see them on the air using WLAN Pi in Remote Sensor mode to WiFi Explorer Pro macOS app.
Practically instantly after enabling these, the iPad discovers the 6 GHz one using 2.4 GHz RNR.
Here is the RNR Information Element included in 2.4 GHz beacons.
RNR IE in 2.4 GHz beacons tells the client to look for 6 GHz AP on 6 GHz channel 5iPad sees both the 2.4 GHz “Cisco 2.4” and 6 GHz “Cisco 6” SSIDs
Summary
The new iPad Pro with Wi-Fi 6E only relies on Reduced Neighbour Reports (RNR) when it comes to discovery of 6 GHz Wi-Fi 6E networks. It will only discover a 6 GHz SSID, if you also enable the same or different SSID name on 5 GHz (and/or 2.4 GHz if needed).
It ignores FILS sent by the AP on its primary 6 GHz channel.
It also ignores unsolicited probe responses sent by the AP on its primary 6 GHz channel if we enable them explicitly.
It doesn’t actively scan 6 GHz to discover new SSIDs.
I recommend you enable a 5 GHz (or 2.4 GHz) SSID, which will allow the iPad to use RNR Information Element included in the 5 GHz (or 2.4 GHz) beacons. It will help other clients like Google Pixel 6, which I’ve tested here, too.
I am very happy with how well the 6 GHz discovery using 2.4 GHz or 5 GHz beacons works. It definitely is production ready. The test with only one 6 GHz only SSID on the AP is more of a corner case. Most customers I work with, if not all, will also deploy 5 GHz alongside 6 GHz, so there is absolutely nothing to worry about.
Packet capture or it didn’t happen 😉
Download 2.4 GHz an 5 GHz RNR, 6 GHz FILS, and 6 GHz unsolicited probe response packet captures from here.
Download WLAN Pi Profiler report and packet capture of 5 GHz association request, and also 6 GHz association request. We can see client’s capabilities in these frames.
This question comes up and every now and then. So, let’s put it to bed.
If you have a ceiling-mounted internal antenna AP (with built-in antennas), or external antenna AP with dipole antennas (AIR-ANT2524D), or with short dipole antennas (AIR-ANT2535SD), here are the correct Azimuth and Elevation angle settings.
This is how 0° Azimuth and 0° Elevation look like. Plus “squished doughnut” as a bonus to illustrate the coverage pattern 🍩
Azimuth angle does not matter in this case (it does for directional antennas), because these antennas have the same pattern regardless of how you rotate them clockwise or counterclockwise. Simply use the default value of 0°.
Elevation angle is 0° for this orientation.
Cisco DNA Center Azimuth and Elevation configuration
Let’s take this “Back to the basics” question and test things out.
So, we have this 20 MHz capable Windows 11 Wi-Fi client and we want to see what happens when it attempts to join an SSID that uses 80 MHz wide channel. Will it associate? Will it fail?
Here is my client with Intel AX201 adapter forced to only support 20 MHz wide 5 GHz channel.
My AP uses 80 MHz channel width.
Let’s verify the settings from a Mac. Yes, the AP broadcasts 80 MHz wide “lab5” SSID with primary channel 36.
Finally, what happens if the client device is only capable of 20 MHz channel width? As you can see, it will happily join using Primary channel 36.
More capable client devices that support 80 MHz channel width will benefit from the 4 bonded channels and use the 80 MHz channel in its entirety.
My Catalyst 9800-CL controller is hosted on a cloud, so I don’t need any hardware for that. Finally, my Catalyst 9136 Wi-Fi 6E AP is powered by a Catalyst 3560CX 10 Gigabit Ethernet multigigabit switch.
6 GHz 2×2 MIMO setup powered by PoE+
Catalyst 9136 is Cisco’s premium AP with all the bells and whistles including hexa-radio architecture and built-in environmental sensors for smart building use cases. It requires an 802.3bt/UPOE power source to enable 6 GHz radio in full performance 4×4 MIMO mode. The switch I use supports 802.3at/PoE+, which is great, but 6 GHz radio downshifts to 2×2. And that’s where an 802.3bt power injector comes to the rescue.
Since the Cisco injector isn’t widely available yet, I decided to test this Zyxel one. It provides 802.3bt power and allows the AP to run in full power and full 4×4 6 GHz radio mode with no compromise.
Do I like power injectors in production?
Absolutely not! Ideally you should design for 802.3bt/UPOE switches to power all your new APs via PoE.
It allows you to:
easily, centrally and remotely monitor how much power the APs use
enable/disable power on a port to bounce an AP
leverage redundant Platinum-rated power supplies for the AC to DC power conversion
manage the solution with ease – just think how difficult it is to manage more than 1 power injector, the number of AC power sockets, and what happens when someone disconnects the injector?
I still use C3650 UPOE mGig switch in my lab. Catalysts 9300 and 9400 the best choice these days.UPOE and mGig capable C3650 providing full power to the AP
Final look
Carrying a full-size switch is not really an option for me, because small form factor is my main goal. So a power injector works best for me. But if I could I would love to use a compact 802.3bt switch.
Are you wondering if the PoE splitter connected to my iperf3 server (the little black box with 3 Ethernet interfaces) actually negotiated 2.5 Gbps Full duplex with the switch? Yes, it did. But keep in mind that the PoE splitter is technically only rated for 1 GbE. So use as short patch cable as possible and ideally CAT6.
Still few things to tidy up and perhaps I could build this into a nice Pelican case
