Channel center freq for 20/30/40 MHz channel

I've looked everywhere and can't seem to find the answer to this question, other than just to try what-if experiments.

When filling out cnMaestro spreadsheet, what center frequency should we choose if we are asking for a 20, 30 or 40 MHz channel width?

Instructional video shows example 3595 MHz for a 20 MHz channel, if I remember correctly.  It seems like the center of a valid 20 MHz channel shouldn't end in 5.

Is this like WiFi with a center and extension channels, like Ce or Ceee?  Do we specify the center of one 10 MHz channel and hope the SAS grants us additional adjacent channels?

If so, is there a strategy for mazimizing the chances of getting what we request?  Will it do Cee or eCe or eeC?  Should we be doing a spectrum inquiry request before finalizing our spreadsheet?  That doesn't sound right.

I have forwarded this to the product and support teams

When asking for channels to the SAS, the edge of the channel needs to line up with a frequency ending in 5 or 0.

If you ask for a 10, 20, 30 or 40 MHz channel, this means that the center frequency needs also to end with 5 or 0. For example, a 10 MHz channel can be 3570-3580 or 3575-3585.

However, the spectrum inquiry request to the SAS is done on the 10 MHz boundary. If you ask for a grant on 3575-3585, the device will send a spectrum inquiry request for both the 3570-3580 and the 3580-3590 channels; they need to be both available for the SAS to allow a grant on the 3575-3585 channel. 

If you ask for a 15 MHz channel, the center frequency now needs to end with 2.5 or 7.5, in order to align the edge of the channel correctly. 

If using the cnMaestro spreadsheet, when you select the channel BW, the center frequency can be selected from a drop-down menu which lists all options. A newer version of the spreadsheet will be available in the next cnMaestro release, which contains also support for 15 MHz channels. 

Currently there is no support for a 5 MHz channel because we think there is no interest. If you find it useful, please let us know and we can make it available in a future release.

When asking for wider channels, there is no concept of center channel and additional channels. If you want a 30 MHz channel, you request the full 30 MHz.

It is always recommended to run a spectrum scan in the area before selecting a channel. Currently, the SAS only protects the incumbents, it does not perform interference calculations between GAAs. If you select a channel that is protected by the SAS (the spectrum inquiry will show it as unavailable) the SAS will reject the request. If you have configured alternate chnanels, the AP will request a grant on those. If you haven't configured alternate channels, just change the center frequency on the primary channel. If the channel you select is not protected by the SAS, today the SAS will give you a grant on that channel regardless if there are other operators in the area using the same channel. In the future, the SAS will actually perform interference calculations and assign channels to devices, so the first request will become less critical, as it is likely the SAS will assign a different channel in congested areas.


Thanks for all the info.

Oh, and I feel a bit foolish for not realizing the SAS doesn't protect one GAA user from another.  I am kind of hoping they at least try not to authorize the same frequency to every GAA user if there are others available.  I guess we still need to do an SA before a grant request, and again periodically.