Dear all, I'm just setting up some script which shell help me to collect data during mesh performance measurements.
When using several boards (single hop distance to each other) I recognized (using the station dump output) that the tx bitrate is varying (in time, depending on the node). But I'm not sure why? I don't move the nodes or change anything else. I use the same hardware for all nodes. How is the bitrate set? Who is setting/changing the bitrate? Why? Is there a formula? I think it is maybe somehow related to the metric but I'm not sure. Would be great if someone has a short explanation or a link for me!!! Thank you in advance and best regards, Marco >-----Ursprüngliche Nachricht----- >Von: Devel [mailto:[email protected]] Im Auftrag von Steger, >Marco via Devel >Gesendet: Montag, 16. Februar 2015 16:22 >An: [email protected] >Betreff: AW: 802.11s performance testing - tools and tips > >Hi all, >today I played around with backports and I also tried to compile a new kernel >version for my Linux PC but I wasn't able to get debugfs running. I don't get >any >files in the ieee80211 directory. > >Any ideas? Would be great! > >Best regards, >Marco > >>-----Ursprüngliche Nachricht----- >>Von: Steger, Marco >>Gesendet: Montag, 16. Februar 2015 11:29 >>An: Steger, Marco; [email protected] >>Betreff: AW: 802.11s performance testing - tools and tips >> >>Hi all, >> >>after my vacation and some research about debugfs I have a short question: >>I read several times about enabling debugfs for the ath9k_htc (e.g. >>[1]). Am I right that this means, that I will have to compile the >>ath9k_htc on myself? (I'm using debian 3.19) If yes, what would be the easiest >way to get the required source? >> >>Best regards, >>Marco >> >> >> >> >> >>[1] >>https://wireless.wiki.kernel.org/en/users/Drivers/ath9k/debug#ath9k_and >>_ath9k >>_htc_debugging >> >>>-----Ursprüngliche Nachricht----- >>>Von: Devel [mailto:[email protected]] Im Auftrag von >>>Steger, Marco via Devel >>>Gesendet: Mittwoch, 21. Jänner 2015 17:23 >>>An: Bob Copeland; [email protected] >>>Betreff: AW: 802.11s performance testing - tools and tips >>> >>>Hi Bob, dear all! >>> >>>Thanks for your explanations. So the data rate will (probably) >>>decrease automatically while increasing the distance between two >>>nodes? There is no way to tell the nodes that the must use e.g. 54.0 >>>MBit/s all the time? (sorry if this is a very stupid newbie >>>question... ;) ). So the best way will be to periodically use ' iw dev mesh >>>station >dump ' >>>during the measurements to get the current bit rate? Am I right? >>> >>>Thanks for the hint regarding debugfs. I have never used this before >>>so I will have to learn more about it. But after a quick google search >>>I think I basically will have to check the files in ' >>>/sys/kernel/debug/ieee80211/phy0/ ' but this folder is empty on my >>>BeagleBone board. How to configure this? Will I have to recompile my >>>ath9k driver or something like that. I found >>>http://wireless.kernel.org/en/users/Drivers/ath9k/debug but I'm not >>>really sure >>how to start. Would be great if you guys can give me a hint... >>> >>>Best regards, >>>Marco >>> >>> >>> >>>>-----Ursprüngliche Nachricht----- >>>>Von: Bob Copeland [mailto:[email protected]] >>>>Gesendet: Mittwoch, 21. Jänner 2015 16:09 >>>>An: Steger, Marco; [email protected] >>>>Cc: Yeoh Chun-Yeow >>>>Betreff: Re: 802.11s performance testing - tools and tips >>>> >>>>On Wed, Jan 21, 2015 at 11:28:32AM +0000, Steger, Marco via Devel wrote: >>>>> Are there any parameters which will change while I'm increasing the >>>>> distance between the two nodes? Bit rate? Anything else? Any >>>>> parameter which can probably change? (I really want to have a clear >>>>> and proper >>>>> result) >>>> >>>>You can expect rate to decrease as distance increases. In practice, >>>>it's difficult >>>to >>>>control for the channel conditions in such an experiment, because >>>>small movements may cause large changes in the channel properties. >>>> >>>>> To get the packet error rate I want to periodically/permanently >>>>> send message from one node to the other one. Can I use normal UDP >>>>> packets for that? Is there a possibility to send packets on a lower >>>>> layer in Linux? (I think raw Ethernet sockets will be helpful but I >>>>> will have to investigate some more here) >>>> >>>>You may wish to distinguish (layer 3) packet loss and (layer 2) frame loss. >>>>The frame loss is probably the more interesting number... for that I >>>>believe there are some counters you can use that are exported in debugfs. >>>> >>>>Note that for unicast traffic over wifi, there is a retry mechanism >>>>at the MAC layer, so some levels of frame loss may not show up as UDP >>>>packet loss but as latency instead. >>>> >>>>For multicast traffic, there's no retry, but there's also no rate scaling. >>>> >>>>Relevant to mesh: besides channel conditions, latency and bandwidth >>>>are also determined by the number of nodes that are communicating, >>>>because only one station in a given listening area can transmit at a >>>>time. So consider that in a 3- node, multihop scenario (A<->B<->C), >>>>you'll probably see a factor of 2 reduction in achievable throughput >>>>compared >>to just two nodes. >>>> >>>>-- >>>>Bob Copeland %% http://bobcopeland.com/ >>>_______________________________________________ >>>Devel mailing list >>>[email protected] >>>http://lists.open80211s.org/cgi-bin/mailman/listinfo/devel >_______________________________________________ >Devel mailing list >[email protected] >http://lists.open80211s.org/cgi-bin/mailman/listinfo/devel _______________________________________________ Devel mailing list [email protected] http://lists.open80211s.org/cgi-bin/mailman/listinfo/devel
