field notes troubleshooting

Non-wifi interferers

I was analyzing a set of surveys and found some interesting interference sources. Except for the first three, they are all above 5.725 GHz which is home to the U-NII-3 (5.725-5.850 GHz) and the 5.8 GHz ISM band (5.725-5.875 GHz).

Feel free to comment if you have seen it in the wild.

This looks like Godzilla, consistent interference in a wide area, source unknown.

Possibly some video surveillance system, there are two in the area, see next.
Possibly video surveillance systems

Movement sensors for lighting fixtures
Movement sensors for lighting fixtures
Movement sensors for lighting fixtures

Strong interference spilling over from U-NII-3 up to channel 136. Source unknown.
This interferer is spilling up to channel 132. Unknown source.
Different site, similar interference pattern.
Yet another site, same pattern with harmonics reaching channel 140.

Possibly a non-wi-fi security camera on channels 60-64.

field notes tools

Subway wi-fi

A new subway line has opened in Milan, the M4 connecting the city airport with the city center. It’s a driverless fully automated transport system.

The active section of M4 subway in Milan.

There’s a WPA2-Personal SSID in every station, powered by Cisco APs. No wi-fi in the tunnel between stations.

As usual, quick wi-fi analysis and packet capture done with my Analiti for Android app.

You can download the pcap file here.

field notes

Wi-fi at the cinema

At my local cinema, an Apple AirPort (possibly Extreme 802.11n) quietly keeps the show running. The pcapng was captured with Analiti on Android.

design eduroam events

My talk at GARR Workshop 2022

In my talk at GARR Workshop 2022 in Rome, I made the case for professional WLAN design in the Italian university and academic world.

Feedback in the audience has been overwhelming! My thanks to my employer unimi, to GARR and the Italian WLAN community for supporting, contributing ideas and criticism.

Designing wi-fi networks in the academic and research institutions requires specialized knowledge and tools to deal with this sector’s requirements (size, high density, BYOD, student dorms, IoT devices). An investment in knowledge and best practices is needed to design high performance wireless networks. There’s an open, inclusive community of WLAN professionals where problems and solutions are shared, where knowledge and skills grow – worldwide and now also in Italy.

From the abstract of my presentation

Full video, slide deck and profile here.

Update 17/2/2023: interview in GARR News magazine:

field notes troubleshooting

Bruker NMR interference?

I was called to discuss the installation of an access point in a chemistry research facility where a Nuclear Magnetic Resonance (NMR) spectrometer by Bruker is operating. It’s a model slightly smaller than the one pictured below.

Credits: Mike25. Source: Wikipedia

Researchers operating the laboratory were concerned about the signal from a wi-fi access point in the same room possibly interfering with the instrument. My concern was in turn that the NMR would interfere with the wi-fi operations, given the much higher energy in play in an NMR spectrometer.

Upon discussion with the lead researcher, it was ascertained that the spectrometer works with RF below 1 Ghz, mainly in the 400 Mhz range. According to Wikipedia, it operates in the 60-1000 Mhz range.

Interestingly, a spectrum analysis with Metageek Chanalizer in the lab showed a distinctive interference on 2.4 Ghz centered on channel 2 and a lesser signal on channel 1. The measure was taken from a fixed position at 3m from the spectrometer, while it was operating.

The signal on channel 2 has a high duty cycle with 95% at -50dBm in a 20 minute interval.

At -70 dBm the duty cycle on channel 1 was above 80%.

Moving away from the NMR into adjacent rooms, the interference weakened and wasno longer detectable. I was not able to identify the exact source of the interference, besides it being related to the Bruker device operations. The access point was moved out of the room into the corridor.


Passed the CWISA exam

Last Friday I did the Certified Wireless IoT Solutions Administrator (CWISA) exam. It’s a prerequisite on the CWNE path and the starting point of the CWNP IoT track. It’s a surprisingly easy exam that draws heavily from CWNA, with an additional high-level view of cellular and IoT protocols.

Because CWISA is a prerequisite for new and renewing CWNEs, the majority of real-world CWISA takers are wireless experts with several professional wi-fi certifications under their belt.

However, the CWISA certification and exam objectives are designed for an entry level audience. The official study guide is rich in easy introductions, wide preambles, repetitions of concepts, high level overviews and market consulting summaries. It’s not a thrilling read.

The exam is 60 questions with the usual 70% minimum pass score. It’s materially impossible for a CWNE level candidate to fail. A newcomer would find it engaging, but less complex and less taxing than CWNA.

CWISA-101 will be replaced by CWISA-102 in September 2022, which will probably improve some of the shortcomings. The professional certifications in the IoT certification track look really interesting and I will probably take it in the future.


Disable AP status light in Extreme CloudIQ

This is so stupid and still not so easy to find out: to turn off the LED of an AP in Extreme Networks CloudIQ, go to Manage > Devices, select your APs, click on Utilities > Tools > Locate your device.

You will be presented a dialog to switch-off the light or start a blinking pattern.

This feature is meant for troubleshooting and device location, when you are on-site and don’t know where a specific AP is. Just configure a blinking pattern on XcloudIQ and see which AP blinks.

If you place APs in hotel rooms, student dorms or home bedrooms, you MUST turn the LED light off. Otherwise, people will cover it with chewing gum, stickers, tampons or anything at hand.


The safety of Wi-Fi in Europe

In 2015 the European Commission has published a scientific opinion on the health impact of electromagnetic field exposure, via it’s Scientific Committee on Health, Environmental and Emerging Risks (SCHEER).

The Opinion was first published in 2009 and updated in 2015 in the final official version. It is an analysis of existing research on the health impact of a broad range of EMF, including those typical in WLAN technologies.

In case you are wondering: under the conditions dictated by the European regulatory domain, wi-fi is safe.

An easy to read fact-sheet (1 page pdf) is available, in a format and language accessible to non-specialists. An easy to navigate summary of the Opinion is also published, good for high level browsing and quick drill-downs. The full document is 218 pages and is freely downloadable from the EU Commission site.

This documents can be referenced in the WLAN policy documents of your organization. Users concerned about the health aspects of the coroporate WLAN should be directed to the policy, or to the original documents.


Towards wi-fi 6E in Italy

The approval of 6Ghz spectrum for wi-fi 6E use in Europe is governed by the European Commission decision 2021/1067/UE from 17 June 2021.

This Decision harmonises the conditions for the availability and efficient use of the 5945-6425 MHz frequency band for wireless access systems including radio local area networks (WAS/RLANs).

Commission Implementing Decision (EU) 2021/1067

By 1 December 2021 Euroean member states had to make available the 5.945-6.426 Ghz frequency band. The deadline expired and as of now, only the Netherlands have harmonized it (23 December 2021) and Ireland (11/1/2022).

Frequency band allocation in Italy is regulated by the Piano Nazionale di Ripartizione delle Frequenze (PNRF) from the Ministry of Economic Development. The latest PNRF is from 2018 and does not allow 6Ghz for WAS/RLAN.

An open consultatin on a new PNRF draft (which includes the 5.945-6.426 Ghz frequency band use) is underway with a deadline at 31 January 2022. The timetable after the consultation closes is not known.

It is possible that an updated PNRF will be published in the first months of 2022, opening up the 6Ghz frequency band in Italy and making wi-fi 6E possible in Italy.

I will follow the developments closely.


Notes from GARR Workshop 2021

Interesting wi-fi talks at GARR Workshop 2021 last November.

Paul Dekkers from SURFnet speaks about Eduroam, openroaming (Hotspot2.0 and Passpoint), CAT and the geteduroam app. Geteduroam has many advantages over CAT and will eventually supersede it. Slides and video.

GARR’s Pasquale Mandato presents eduroam usage data during the 2020/2021 pandemic in Italy, GARR’s self-service tools for Eduroam technical contacts in Italy, highlights and pitfalls of geteduroam, and the little known companion app. Slides and video of the talk (Italian).

Daniele Albrizio from University of Trieste analyzes the security of eduroam and the importance of using CAT for device onboarding. Communicating with the eduroam user base is crucial, and tough choices must be made, such as phasing-out support for older, obsolete client devices. Slides and video (Italian).