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Showing posts from May, 2018

The 5GHz “Problem” For Wi-Fi Networks: DFS

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Wi-Fi networking provides us with 2 bands for the operation of wireless LAN networks: the 2.4Ghz band and the 5GHz band. The 2.4GHz band has a reputation of being something of a “sewer” of a band, due to its limited number of usable channels, the number of Wi-Fi devices already using the band, and the high levels of non-Wi-Fi interference that it experiences. Many wireless LAN professionals will generally advise that you put your “important stuff” on the 5GHz band whenever possible. 5GHz has far more channels available, a corresponding lower number of devices per channel, and generally suffers much lower non-Wi-Fi interference. However, beneath the headline of “2.4Ghz = bad, 5Ghz = good”, there lurks a shadowy figure that can be troublesome if you’re not aware of its potential impact: DFS.

Background
Wi-Fi networks operate in areas of RF spectrum that require no licence to operate. This is in contrast to many other areas of the radio spectrum that generally require some form of (paid-…

802.11 Roaming Variations Cheatsheet

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I recently saw a very interesting post from Gjermund Raaen about Fast Secure Roaming, where he discusses OKC and 802.11r. This reminded me of some roaming issues I had recently observed with OKC myself, which got me looking up information to refresh my memory on a variety of roaming methods and standards.

While looking in to the issue, I came across a classic blog post from Andrew Von Nagy about 802.11 roaming. It provides a superb summary of various roaming and security methods. I've read the post several times in the past, but thought that I would really benefit from a summary of its content to act as a memory jogger, rather than reading through the whole document again. For me, things get a little hazy when I start trying to remember the intricacies of the differences between EAP session resumption, PMK caching, OKC and PMK.

To save myself some time for the next time I go through this loop, I put together a summary (Cheatsheet) of the content of the roaming variations post. If…

Updated White Paper on Licence-Exempt Spectrum in the 5GHz band for Wireless LANs in the UK

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For the past few years, I've maintained a white paper on the use of the 5GHz spectrum for Wi-Fi networks here in the UK. As Wi-Fi text books tend to focus on the spectrum available in the USA, I put this document together to clarify how 5GHz spectrum may be used in the UK.

Following the release of a Voluntary National Specification document by Ofcom in August 2017 (VNS 2030/8/3), additional channels became available for use in the UK on 5GHz.

As we now have additional spectrum, it's time for an update to my white paper to detail the new spectrum that is available.

Prior to updating the white paper, I published a summary sheet that shows the new spectrum allocation. This can be obtained obtain from my previous blog article: UK 5GHz WLAN Spectrum Allocation (August 2017) (this is definitely one to print off and laminate).

I have now completed my updates to the white paper, which I am pleased to share with you now. Note that in addition to adding the new spectrum details, I have…