Luca Muscariello <muscarie...@ieee.org> writes: > On Thu, Oct 24, 2019 at 11:34 AM Toke Høiland-Jørgensen <t...@redhat.com> > wrote: > >> Luca Muscariello <muscarie...@ieee.org> writes: >> >> > On Wed, Oct 23, 2019 at 2:27 PM Toke Høiland-Jørgensen <t...@redhat.com> >> > wrote: >> > >> >> Rich Brown <richb.hano...@gmail.com> writes: >> >> >> >> >> On Oct 23, 2019, at 5:54 AM,<erik.tarald...@telenor.com <mailto: >> >> erik.tarald...@telenor.com>> wrote: >> >> >> >> >> >> If you could influence the 4G vendors to de-bloat their equipment, >> >> >> would you recommend BQL, L4S or codel/cake? >> >> > >> >> > I've been enjoying this discussion and wonder whether the work going >> >> > on in the make-wifi-fast >> >> > (https://lists.bufferbloat.net/pipermail/make-wifi-fast/) is >> relevant. >> >> > >> >> > I only have a 30,000 foot understanding of this work, but it seems the >> >> > use of AQL (Airtime Queue Limit) maps better onto the vagaries of >> >> > 4G/5G radio transmissions than BQL. Specifically, having a measurement >> >> > of the actual time it takes to transmit a packet might give additional >> >> > information about the current link speed, with the potential for >> >> > adjusting the codel target, etc. >> >> >> >> Indeed, I suspect something like AQL would work for LTE as well. At the >> >> right level; think this might need to be in the firmware (which in turn >> >> could push back on the host). >> >> >> >> > Separately, I also wonder whether the Air Time Fairness algorithm >> >> > might provide a benefit if the cellphone tower station manufacturers >> >> > chose to get into the game. >> >> >> >> LTE base stations already does TDMA scheduling (which they can do easily >> >> because they are centralised and own the license band); airtime fairness >> >> is about getting the same benefits into WiFi that LTE has been enjoying >> >> from the get-go :) >> >> >> > >> > There is one main difference between ATF and the kind of TDMA >> > realized by an LTE scheduler (but also HSDPA/HSUPA). >> > Toke correct me if I'm wrong. >> > >> > The current ATF scheduler for WiFi does airtime-DRR based on the >> > current PHY rates, is that right? Side question, how do you measure >> > current? >> >> s/current/last/. The ATF scheduler does everything after-the-fact, by >> accounting the actual TX time of a transmission after it has completed. >> So no fancy scheduling or prediction tricks are needed; with the >> tradeoff being coarser granularity of the fairness achieved (i.e., there >> can be unfairness on short timescales). >> >> In the airtime queue limit work that's ongoing, we do ahead-of-time >> airtime estimation to limit queueing in firmware. But this still just >> uses the last TX rate recorded for the given station to calculate the >> estimate. >> >> > In LTE TDMA makes use of what is called multi-user diversity gain >> > by scheduling users when they are at their relative best radio condition. >> > Typically the user with the best current radio condition NORMALIZED >> > over the average radio conditions. The average can be based on a >> > moving average or a sliding window. This is the case of the widely used >> > David Tse's proportional fair scheduler. >> > >> > This means that TDMA is still in place to share air-time fairly but the >> > scheduler will tend to avoid bad radio conditions. >> > >> > From a theoretical point of view if you do that the total capacity >> > of the AP can increase with the number of stations (I think >> logarithmically) >> > as the scheduler surfs across radio quality peaks and not the average >> radio >> > quality. Very smart. >> > >> > In LTE this is doable as the scheduling time slot is 1ms and the >> > feedback channel is as fast. Not all TDMAs are equal. >> >> Yeah, the LTE MAC is pretty cool. Just a shame that the equipment is so >> expensive :( >> > > It looks like there is a positive correlation between the size > of the specifications and the cost to build the associated product :)
Hehe, yeah, funny how that works. IMO the LTE people went a little bit overboard on the complexity, though... ;) -Toke _______________________________________________ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat