WiFi mysteries resolved once and for all — Power saving is clearly the culprit!


porg

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To me the Pandora is also "the weak wifi kid on the block", which cannot "make itself heard" among a surrounding "loud" crowd (interference). A shy kid!

But with the help of a USB WiFi adapter, its ego can be really boosted. Sadly though, stronger egos require more energy (battery).  ^_^
 

porg

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Performed some more tests under my recent suspicion:

I have a totally new idea concerning my WiFi and charging issues. What has NOT changed throughout all the 3 Pandoras (2 originals, 1 rebirth) I have had is ……… the battery!!! Maybe this is causing both my issues with charging and potentially WiFi, as the WiFi chip is directly connected to the battery, according to notaz. It is likely that at the OpenPandora workshop the testing was done with their spare batteries, and therefore the issues were unnoticed? I will ask ED & Askarus directly, and if I get infos, follow up here.
Booted my Pandora without a battery, just connected to the original OpenPandora charger.

Result: WiFi has the same behavior (mostly faulty, sometimes amazingly speedy).

Details: Now since Sysinfo 0.6 having the ability to toggle WiFi, and to toggle its powersaving, giving you instant control & feedback, the correlation between powersaving and speed felt even more obvious.

Again: Not so obvious that without powersaving WiFi was working 100% and without powersaving not, but quite tendentially: With powersaving working 0-10% (0-60 KB/sec, stalling soon, but rarely if "critical treshhold" (see details in my previous posts) is reached sometimes keeping almost max WAN speed of 650 KB/sec steadily), without powersaving working 30-60% (not always maximum speed, but at least better than with powersaving at the very recent moment, i.e. getting 30 KB/sec instead of 0, or 60 KB/sec instead of <10 KB/sec, and often if it reaches high speed, it then keeps it, if switching to powersaving mode, sometimes keeps it up, sometimes drops down).

Conclusion / Follow-Up: I have almost nothing left than to believe that I have had enormous bad luck by getting 3 Pandoras all with HW faults (WiFi & charging).

(Except if the battery is needed in the circuitry to "smooth the current" (or something like that) before it reaches the WiFi chip, but I doubt that. Confirmation anyone?)
 
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F_Slim

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Have you tried switching your Router to a different Wifi-channel already? If the Pandora is very sensitive to interference this could be your problem. I set my Router to a channel which is not occupied by another access-point. But probably also one of those phones without a cable could cause problems, so it's definately worth a try.

Also, what is the reported connection quality? I start to get problems only if it falls below 50%.
 

Binky

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Is there any way you could get a setup where your pandora and your router were the only transmitting wifi devices within range?
 

Franko

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Is there any way you could get a setup where your pandora and your router were the only transmitting wifi devices within range?
Good idea.  Finally I have a reason to continue my "subspace dampening field" research.  I knew that all of these years watching Star Trek reruns would come in handy...
 

porg

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@F_Slim: I am far beyond that point (if interested: see this whole thread and the massive amount of my already performed tests and falsifications).

@Binky: Testing in an isolated WiFi environment, as mentioned earlier in this thread, is one of my last outstanding tests. Nevertheless, even if it would work then, it would not be satisfying, as the Pandora should be able to transmit in normal WiFi environments, as all other common WiFi devices do.

@Franko got that point, made his joke about that ;-)
 
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F_Slim

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The strangest thing just happened to me: I got the Wifi-issue! Out of the blue basically. No page would load in Firefox unless powersaving was disabled. It worked fine an hour or so before!!

So I checked for other interfering Wifi-Hotspots using the same channel: nothing. BUT: something else on the same frequency. After I changed the channel everything is fine again.

I also noticed another network within the same 20MHz bandwidth which moved away after I changed to a closer channel.

So the problem was either caused by the interference on the same channel or by the other network in the bandwidth.

This is the first time this ever happened to me, just a few days ago I've been in a room with at least 20 other people using Wifi and had not problems at all.
 

notaz

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I visited my parents last weekend with a pandora, and it turned out they have "incompatible" router with wifi power saving. PS is working fine here at home and disabling it doesn't give much positive effect, but there it went from 10-20KB/s with PS to ~350KB/s without (maxing out their Internet connection). However occasionally that router works fine with PS too, so as usual it's all inconsistent and confusing.

So when it went bad, I was able to do a bit driver-level debugging and found, with certain level or confidence, which firmware commands were causing problems. I've also found out that Linux wifi stack (mac80211) is trying to do dynamic power saving, i.e. it automatically turns off power saving when there is data to transfer and turns it back on when queues are empty for ~100ms. But what I found later is that this wifi chip is not very happy to change powersave modes too often, it takes it ~150+ ms to turn on PS and ~50ms to turn it off. Meanwhile, depending on load, stack may be switching states at 100ms internals, which means the chip is often interrupted in it's PS change sequence, which causes it misbehave. I did not have time for much coding at my parents' and had to go home (it's over 3h drive to them so I don't go there too often).

So I did some driver tweaks during this week, mainly to stop it switch PS states too often. I've also optimized scheduling a bit (moved transfers to dedicated thread to avoid context switching), optimized firmware command polling and register reads (see http://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=shortlog for code changes). With this I seem to get a bit of performance improvement and more stable transfers here at home. I don't know if it fixes problems with my parents' router as I won't be able to test with it for some time.

The wifi tweaks are available along with slightly newer kernel through "System->upgrade pandora OS". Everyone's invited to test.
 
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Gausen

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Works fast without any command line tweaks. Thanks Notaz!

130523-210546.png
 

notaz

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Forgot to say this won't help if your wifi is slow without power saving, which is the case with my CC pandora.

skeezix reported no improvements too, but I'm not sure on what kind of unit.
 

TrashyMG

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I've only tried my 1Ghz unit, I can try my Rebirth and CC units this weekend. My 1Ghz unit wasn't as good as my Rebirth where WiFi is concerned, but better than my CC unit.
 
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ShleeDragon

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Amazing. My wifi was always horrible and that's made it obviously more stable.. how stable is unknown.
 

Gyges

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So, what if your wifi is sufficiently unreliable that you can't download the update? :(
 

TrashyMG

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So, what if your wifi is sufficiently unreliable that you can't download the update? :(
Plug in a USB Ethernet or Wifi adapter and download it.. or wait for the next full updater to come out so you can do an SD card update.
 

F_Slim

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It does seem to be better with the update. Posting this will be the best test, since I am far away from the router here, and usually sending a post on the forum is impossible unless I turn off powersaving. (Works fine closer to the router).


So .. here we go! (click)


... nah ... Firefox failed as usual. Now trying Arora ... (click)


[EDIT:] ah, so that worked! So Wifi did improve! (Also judging from the responsiveness of other websites in Firefox)


On the other hand, sending this EDIT fails again also under Arora ... so maybe the forum isn't such a good test after all.


Anyway, thanks again Notaz. Overall I still think it got better when being far away from the router.
 
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notaz

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PowerGod

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wow, just... WOW !!  :eek:  I had a vnc session open and went out to the balcony, every time I did this I always had to reconnect it to the router at my return, but now the session was still open and working !!  ^_^
 
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