Hello Curt,
It has always been possible to use channels 12 and 13 in the USA because they are perfectly "in band" channels. However, it is very difficult for a WLAN device to pass the FCC tests on those channels, so most manufacturers simply choose to disable them. Some manufacturers choose to reduce the power on those channels. Of course, if the whole device has sufficiently low power, then it might pass channels 12 and 13 (or just 12) without additional power reduction. This means that most WLAN devices use only channels 1 to 11 but some do use 1 to 12 or 1 to 13. (12 is easier to get passing than 13, since the tricky test is a band edge issue) It has always been the case that if you only test and certify your device up to channel 11, then you cannot sell a device which could transmit on channels 12 or 13. In the past, manufacturers have asked the FCC if their devices can passive scan on 12 and 13, even if their device is only certified up to channel 11. Of course the answer was "yes, you can passive scan" because passive scanning does not include transmission. Of course, the assumption then should be that if the client device sees a working access point on channel 12 or 13, it must not actually form a link and transmit! You can imagine that as a TCB, if we see an application which states that a device transmits on channels 1 to 11 and can also passive scan on channels 12 and 13; it looks perfectly reasonable. Many did not realise the need to ask: "Please confirm that it cannot transmit on channels 12 or 13 if instructed to do so by the access point". It seems that some manufacturers did not make that final step. I am not going to say if this was a misunderstanding or avoidance of the rules by the manufacturer or lack of explanation by the FCC; this is not my comment to make and I'm sure there is a variety of answers. So, last summer 2013, the FCC clarified the point that you can passive scan on those channels but you cannot transmit on those channels if you are not certified to use them, even if instructed to do so by an access point. (Remember that the access point could be using channels 12 and 13 by implementing power reduction, or could simply be breaking the rules!) This 'clarification' came as a surprise to some manufacturers (but not all). Due to this 'surprise', the FCC gave a "6 month amnesty" where they would not actively enforce/investigate this issue. I don't like to call it a transition period because nothing has actually changed. It is a clarification/explanation of the existing rules, it is not a change in the rules. I believe the "amnesty" expires next month. I hope this helps. Michael. Michael Derby Regulatory Engineer ACB Europe From: Curtis Mc Namara [mailto:mcnam...@umn.edu] Sent: 30 January 2014 23:48 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] FCC draft comments on WiFi operation in channels 12 and 13 FCC Draft KDB 594280 Software Configuration Control DR04-41649: https://apps.fcc.gov/eas/comments/GetPublishedDocument.html?id=352 <https://apps.fcc.gov/eas/comments/GetPublishedDocument.html?id=352&tn=40250 1> &tn=402501 This draft says that operation on channels 12 and 13 in the US cannot rely on passive scanning alone. However, at this point it is a draft, and the introductory paragraph says to follow previous guidance. Has a anyone here evaluated this? I have a customer with products in the field which use passive scanning, and they are curious whether there will be a transition time, and whether it is still permissible and practical to ship devices with passive scanning. Thanks! Curt - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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