On Wed, May 25, 2011 at 12:27 PM, Luis R. Rodriguez <mcgrof@xxxxxxxxx> wrote: > On Wed, May 25, 2011 at 12:24 PM, Luis R. Rodriguez <mcgrof@xxxxxxxxx> wrote: >> On Wed, May 25, 2011 at 12:20 PM, Felix Fietkau <nbd@xxxxxxxxxxx> wrote: >>> On 2011-05-25 5:01 PM, Luis R. Rodriguez wrote: >>>> >>>> On Wed, May 25, 2011 at 7:45 AM, Helmut Schaa >>>> <helmut.schaa@xxxxxxxxxxxxxx> Âwrote: >>>>> >>>>> ÂOn Wed, May 25, 2011 at 4:37 PM, Luis R. Rodriguez<mcgrof@xxxxxxxxx> >>>>> Âwrote: >>>>>> >>>>>> ÂOn Wed, May 25, 2011 at 5:19 AM, Helmut Schaa >>>>>> Â<helmut.schaa@xxxxxxxxxxxxxx> Âwrote: >>>>>>> >>>>>>> ÂOn Wed, May 25, 2011 at 12:54 AM, Luis R. Rodriguez<mcgrof@xxxxxxxxx> >>>>>>> Âwrote: >>>>>>>> >>>>>>>> ÂYes, thanks this is a lot of work already done. Now we just need a >>>>>>>> Âbasic algorithm to parse this, quantify how ideal this channel is and >>>>>>>> Âthen spit out a desired optimal channel. >>>>>>> >>>>>>> ÂThat's what I've hacked some time ago (in form of the attached _ugly_ >>>>>>> shell >>>>>>> Âscript that does auto channel selection with rt2x00, not sure if it >>>>>>> works >>>>>>> Âcorrect with other drivers as the survey dump differs somehow between >>>>>>> Ârt2x00, ath5k and ath9k, and it only does channel 1-11): >>>>>>> >>>>>>> Â- Iterate over all channels and stay on each channel for some time >>>>>> >>>>>> ÂNice, yeah I was thinking of using the offchannel operation if we want >>>>>> Âto spend more time there for inspection and if associated. For first >>>>>> Âiteration it should be possible to just move around. In fact for AP >>>>>> Âpurposes I suppose one will want to just start AP mode ASAP and then >>>>>> Âlater do offchannel operations to do the inspection on the ideal >>>>>> Âchannel. Otherwise we sit there idle until we complete the Automatic >>>>>> ÂChannel Selection thingy. >>>>> >>>>> ÂCorrect, especially if we also consider 5Ghz channels. Offchannel >>>>> operations >>>>> Âwould be nice but how can we ensure AP mode while being offchannel? >>>> >>>> Notification of absence. >>>> >>>>>>> Â- Store busy time stats for each channel >>>>>>> Â- Choose the channel with the lowest busy time (and on 2.4Ghz also >>>>>>> Â check the busy times on adjacent channels) >>>>>> >>>>>> ÂSo I was reviewing this -- if we are TX'ing or RX'ing it seems to me >>>>>> Âwe should skip that time from the busy time, otherwise the "busy" time >>>>>> Âincludes time we induced on TX'ing or RX'ing ourselves. So I was >>>>>> Âthinking of using the: >>>>>> >>>>>> Â (active time - rx time - tx time) Â/ busy time >>>>> >>>>> ÂLooks good ;) just one problem from a rt2x00 POV: We can't report rx/tx >>>>> busy >>>>> Âtime separately, we can only advice the hw to include or exclude rx/tx >>>>> time >>>>> Âfrom the busy time statistics. >>>> >>>> Doh, I see.. well in order for the above math to be useful we'd have >>>> to be consistent across drivers. What is being done by rt2x00 right >>>> now? If the later then the math would still work, otherwise then we'd >>>> need to adjust. >>> >>> Excluding rx time isn't even a good idea, since it makes no distinction >>> between local BSS or other activity in the area. >> >> What if we do an offchannel operation? > > Once we figure out that... > > The missing piece is how to deal with noise info here. In short the > lower noise we have the better signal we'll get. The challenge then is > to take into consideration the noise mathematically in such a that a > high noise value would nullify any clean idle air time ratio > conditions from the formula postulated before. Let me review again > with some modifications. > > Active time is the time we spend on the channel, so to get an idea of > how "busy" that channel is we have to remove the tx and rx time from > that channel. That gives us the time we spent idle on that channel. > Then the busy time is a subset of the entire active time but we should > also exclude the time we spent tx'ing and rx'ing as well. We then > have: > > Â(busy time - rx time - tx time) / (active time - rx time - tx time) > > This is a bounded ratio already, given that if we spent 0 time tx'ing > 0 time rx'ing, but 10 ms on a channel, and all that time we had busy > time as well we'd have a ratio of 10 / 10 = 1. In the best case we'd > have Â0 / 10 = 0. > > What I'd like to do is to affect the ratio to nullify it if the noise > is very low on the channel. Given that noise is logarithmic we'd have > to use a logarithmic function as well. Working on that now. I also noticed that the survey results will stale out after a period of time. As such the offchannel operation should ideally be followed imediately by a survey of the channel. Our current API though allows only for an entire survey, not a channel specific survey query. Not a big deal but just something to keep in mind if we intend on using this further for repetitive heuristics on a channel. We'll have to extend the survey dump later to accept channel specific queries. Luis -- 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
