I hack on b43 a little and I try to understand wireless channels. There are few things that seems magic to me, could I get help here? *** First some info I grabbed from specifications: 20 MHz and 5 GHz: 17.3.8.3 start + 5 x channel [0, ..., 200] [start = dot11RegulatoryClassesRequired ? (500 * dot11ChannelStartingFactor) : 5000] 20 MHz and 2.4 GHz 18.4.6 [standard 1-14 channels table?] 40 MHz and 5 GHz: 20.3.15.2 start + 5 x channel [0, ..., 200] [start = dot11RegulatoryClassesRequired ? (500 * dot11ChannelStartingFactor) : 5000] 40 MHz and 2.4 GHz: 20.3.15.1 2407 + 5 x channel [1, ..., 13] This shows channels like 1, 5, 8 (some random numbers) can be actually from any: 2.4 GHz or 5 GHz. Wikipedia [1] seems to agree with this as it contains for example channel 9 with freq 5045. However checking util.c::ieee80211_channel_to_frequency it looks we assume channels lower/equal 14 are always 2.4 GHz. Something weird can also be found in specs: 17.3.8.3.2 Channel numbering This definition provides a unique numbering system for all channels with 5 MHz between center frequencies, as well as the flexibility to define channelization sets for all current and future regulatory domains. So... how does it really work? Are channels uniq? Is our channel<->freq translation bad/OK? *** Are there some forbidden channels at specific ranges in 5 GHz? Wikipedia starts 5 GHz channels from 7, doesn't mention 0 - 6. Same for 17 - 34. Starting with 34 Wikipedia skips odd channels, but only until 149. Checking for 5 GHz channels Broadcom can work with [2] I don't see anything between 0 and 31. Then it goes every even number until 145. *** 802.11j... this is disaster (I know it's Japanese-only). Wikipedia shows channels 183 - 196 as 4.9 GHz. However according to specifications channels between 0 and 200 can be 5 GHz! Similar thing is visible in Broadcom's specs: 182 is last channel in 5 GHz (5910 MHz) and starting with 184 we go down to 4.9 GHz (4920 MHz for 184). Any explaination, please? :| *** Channels above 200?! According to specifications range of 5 GHz channels is 0-200. Wikipedia agrees with that, however Broadcom's code seems to support channels up to 228 (5140 MHz!).The crazy part for me is Broadcom treat's channel 216 as 5080 MHz, while Wikipedia uses 16 for 5080 MHz. Of course there is no "16" channel in Broadcom's specs :| *** [1] http://en.wikipedia.org/wiki/List_of_WLAN_channels [2] http://bcm-v4.sipsolutions.net/802.11/Radio/2056/ChannelTable -- RafaÅ -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
