On Thu, Apr 21, 2016 at 07:12:53PM +0300, Petko Bordjukov wrote: > On Thu, 21 Apr 2016 17:07:21 +0300, > Seth Forshee wrote: > > This is almost certainly because these frequencies require transmit > > power control. We drop the TX power limits by half (i.e. 3 dB) when TPC > > is required on account of not supporting TPC. > > I was under the impression that the underlying kernel infrastructure had support > for TPC. What I am observing is that hostapd automatically includes the Power > Constraint IE in beacons sent out on any channel with DFS enabled. The default > transmit power reduction is 3dBm. > > This means that the TX power of any clients would be limited to 3dBm below the > TX power of the AP even though it's not required. > > Would there be any merit in providing additional information regarding the TX > power and the target average TX power reduction for the system when TPC is > supported? I'm frankly not certain about the status of kernel support, but my impression was that some drivers might have some level of TPC support but that it's not universal. I really haven't been keeping track of it though. However, even if there is universal TPC support in the kernel we still lack any way to encode the TPC requirement for a given rule in the database or inform the kernel about it. > > > WAS/RLANs 5150-5250 MHz > > > 200 mW maximum mean e.i.r.p. > > > 10 mW/MHz maximum spectral density of the mean e.i.r.p. > > > > If this range doesn't require TPC then it could be bumped up to 200 mW > > (23 dBm). > > Yes, the CRC's list explicitly states that TPC is required in the 5250-5350 MHz > and 5470-5725 MHz bands and there's no further comments on the 5150-5250 MHz > band. EN 301 893 has the notes below for the 5150-5250 MHz band that could have > lead to the 3 dBm drop though, maybe linked to the AUTO-BW flag? > > > NOTE 1: The applicable limit is 20 dBm, except for transmissions whose nominal > > bandwidth falls completely within the band 5 150 MHz to 5 250 MHz, in which > > case the applicable limit is 23 dBm. > > > > NOTE 2: The applicable limit is 7 dBm/MHz, except for transmissions whose > > nominal bandwidth falls completely within the band 5 150 MHz to 5 250 MHz, in > > which case the applicable limit is 10 dBm/MHz. It shouldn't be required for the AUTO-BW flag, so based on everything I'm seeing here 23 dBm seems fine. > I changed the TX power values to mW to be consistent with what is stated in the > CRC's list. I'll resubmit the patch with the values in dBm and with the 3 dBm > drop for the 5250-5350 MHz and 5470-5725 MHz bands. Great, thanks. I think you should be fine to bump up the 5150-5250 MHz rule by 3 dBm as well. If someone knows a reason it shouldn't be raised they can let us know. Thanks, Seth
