Monday, 8 October 2012

The Missing Channels on 5GHz in the UK : 120, 124, 128

In my recent article : 'WiFi Channels On The 5GHz Band In The UK', I noted that although the 5GHz channels 120, 124 and 128 are unlicensed channels available for use by WiFi equipment in the UK, it appears that a few major WiFi equipment manufacturers do not allow their use (in the UK or EU).

I spoke with a major vendor representative today who advised me that the 3 channels are available for use, but that an update to the ETSI standard 301 893 v1.5.1 introduced some detection techniques for various military equipment used in the EU. However, many access points that were already manufactured (or using chip-sets that had already been manufactured) did not support the granularity of detection that is required for this equipment. So, it was decided to simply disable support for the affected channels.

Apparently, later APs which use an updated chip-set will not be subject to the same limitations (once a few firmware updates are sorted out).

I had a poke about in the standard to see if I could track down the offending addition, but there didn't seem to be a "what's new" or "change log" that accompanies the document. All I could find was the following note in the ETSI work program item that accompanies the standard:

"Include Staggered PRF radar test signals across the 5 250 MHz to 5 725 MHz band. Include narrow pulse widths for the radar test signals (0,8 ┬Ás) across the 5 250 MHz to 5 725 MHz band. Address noise calibration scan ("zero check") in the 5 600 MHz to 5 650 MHz band."

Perhaps the "zero check" scan that is referenced is the offending item that caused the issue - it certainly falls within the range of the channels that have been disabled.

Although this doesn't provide a comprehensive answer, it at least suggests why we have lost a few channels on 5GHz here in the EU (at least for the moment, anyhow).

UPDATE: I now have an answer on this! Check out my later article here.

Update: I've now created a white paper which details 5GHz usage for WiFi in the UK. Find it here