Wireless Stability Testing

Discussion in 'Sylvania Tablets' started by leighw101, Sep 25, 2011.

  1. leighw101

    leighw101 Member

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    After doing quite a bit of investigation into the reasons for the wireless being unstable on our tablets I made an interesting discovery.I attempt to stream a 10 minute youtube video using the built in app which normally with no changes will drop the wireless connection anywhere between 30 seconds and 3 minutes.

    If the txpower is reduced there is maybe a 10 second improvement but nothing more.Altering the txbeacon setting can add another minute to the playback but tends to knock the wifi out on my router when it does drop.

    As an observation I found the wifi card gets incredibly hot during use, made worse with high data throughput so with this in mind I took the tablet apart and streamed the video while directing compressed air onto the wifi chip. This made a massive difference and kept everything stable for the entire video.
    I'm summising that the wifi dropouts we are seeing are mostly relating to heat as the wifi card is literally stuck to the mainboard with tape with no ventilation at all.As a test I have built up a heatsink "pad" on the chip with "cool tape" which is used to insulate items on turbo cars to reduce heat build-up. I've also coated the back of the case with it and added some thermal compound to help transfer the heat away from the wifi card and into the body of the tablet.

    So far it's looking good as I've had a good connection from loading the browser right through to posting the message - yesterday I could only hold the connection for a minute at a time if I was lucky.

    Will post back my findings on how the heatsink mod goes but the early signs are very promising!
     
    Last edited: Sep 25, 2011
  2. leighw101

    leighw101 Member

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    So after a few days testing on and off the wireless is now much more stable than before and tonight I've gone through a lot of youtube videos to test and used dropbox to test data throughput.
    Under normal use the wireless is stable unlike before and I've not experienced any dropouts since making the mod - txpower is unchanged at 1%.
    The heat now spreads further away from the wifi card and the area around the card just below the buttons is much cooler.
    Still more testing required but this may be a worthwhile mod for anyone having wifi dropouts as bad as I was experiencing where it would disconnect and reconnect every few minutes.

    Sent from my disgo6000 using Android Tablet Forum
     
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  3. leighw101

    leighw101 Member

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    So then, some more testing and it seems the wireless has now returned to it's previous level of instability.
    Not sure if the heatsink has moved or something but I can now get it to drop out simply by trying to access this forum in Dolphin HD - not good at all!

    Will try stripping down again soon and look at possibilities of relocating the wireless card to a more suitable position but I still feel this is kernel driver related more than anything else. Yes the firmware update may have helped out a bit but in general it seems to be more like a bad/old driver compile which is driving the heat up to the point of failure.
    I've also noticed that it's started pulling the wireless down on my router again when it drops too (router is a D-Link DIR-615) so I've now pulled the router into b/g mode instead of b/g/n mode to see if that could be one of the issues.

    Will report back with my findings as I get them :)
     
  4. lohtse

    lohtse Member

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    if it helps.on original froyo installed on tablet when purchased had NO wifi issues.
    but with manual one on forum i have issues....
     
  5. leighw101

    leighw101 Member

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    I stupidly forgot to take a copy of the original firmware to test that so if anyone has a copy of it somewhere it would be great to test with that too.
    I've also done a bit more research into the wifi card and it seems the ralink cards are used a lot in the cheaper tablets with similar problems.
    One suggestion which seems to have merit is the antenna inside isn't quite up to scratch and this causes the card to overheat as it's trying too hard to keep the signal strength up. Will look into this as there's a few people using antennas from old wireless routers with good success rates - certainly this does make sense as the stock antenna is far too short to allow full 2.4ghz bandwidth so the wifi card will be fighting to keep the connection alive far more than it should do and overheats as a concequence.
    There are also a few people replacing the internal card for an external usb dongle using the same chipset and the problems never reoccur - just seems to go against the idea of having an internal wifi connection though and on ours having the mini usb connectors it would look rather ugly hanging off the extension lead :(

    Sent from my disgo6000 using Android Tablet Forum
     
  6. lorenii

    lorenii Senior Member

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    I tried several different lengths of "antenna" wire and if anything, it got worse. I am not sure of the optimal length of an antenna winding would be for 2.4ghz.
     
  7. leighw101

    leighw101 Member

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    Did the same today - best I managed was -43db while it was sat next to the router.
    With the external antenna added it dropped to -67db so looks like it's a no go with those lines of investigation at least :(
    According to all the calculations I've read a monopole antenna for 2.4Ghz should be 4.8" long - which the stock one is about 1.2" long (remember it's not the wire that goes to the antenna end that's included in the calculations as it's shielded cable).

    I've gone with a new heatsink though when putting it all back together by using a sheet of aluminium about 2"x3" contacting the chip head with everything else insulated to reduce the risk of shorting out so I'll get a few tests done with that configuration soon.
    Hopefully it's something that can be resolved though and would be interesting what the guys who've done custom rom development have found with the wifi on their new kernels to see if it really is a driver issue or a hardware issue.
     
  8. mvancil

    mvancil Member

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    Thats good work and good info there. Old school method of thinking. I like it.

    I've noticed some dropped connections, but not a whole lot. I've updated my driver and adjusted the beacon timing. I can usually get about 40 minutes with no drops, and recover from drop is about 30 seconds. So it's not much of an issue for me. I've checked for hotspots when it drops, and the pad seems cool. So I don't think I have the same problem as you.
     
  9. leighw101

    leighw101 Member

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    Well the drops are now less frequent but still occuring.

    Tempted to blow the image over the tablet to reset it to default in case it's something else that I've done to the OS as it wasn't this bad when I first got the tablet, just a shame we don't have a factory 2.2 image for the Disgo 6000 like the one it came with :(
     
  10. leighw101

    leighw101 Member

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    Well seeing as I've now got my hands on another tablet I decided to flash the 2.2 beta3 image onto the Disgo 6000 last night so the other half can have it to play with.

    So far we've only had one drop off on the wireless - a massive improvement on the official Disgo release as that would drop so regularly it almost wouldn't be worth enabling the wireless at all!

    I did notice though that before the re-image the wifi would just say that nothing was in range at all which required a reboot to get it to detect any wireless networks at all.
    After the drop out last night the same thing happened but the reboot seems to have cleared that up fine.

    Will do more tests though and am thinking of removing the heatsink as it made no real difference at all to the functionality of the tablet which hopefully should stop the interference I now get through the speaker when the wifi is active.

    Will keep everyone posted as to how things go and hopefully someday we'll get to the bottom of the problem!
     
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  11. Marikar

    Marikar Member

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    Hi,
    great job looking at the stability. I have a Disgo6000 stock 2.2 os. My wifi was awful but I have tried some different approaches. Changing the mode on the router didn't seem to matter if it was b,g or n. However I changed the encryption a few days ago and that has made my disgo connection fairly stable. I am using wep2. perhapse there is a problem in the code for dealing with wep1 ? I have also added an app that checks the wifi status and repoles this helps if the connection does drop as it reloads in just a few secs rather that around a minute or so and having to turn the wifi off and then on again.

    Hope this helps.
     
  12. leighw101

    leighw101 Member

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    Hi,

    I also tried a few different encryption modes but it seemed to have little effect on my tablet.
    I have got a few things to try from cfrocket which may well make a bigger difference than the other mods but I'll know more once it's been tested fully.

    Sent from my Scroll 7 using Android Tablet Forum
     
  13. giveen

    giveen Senior Member

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    I've noticed setting it to the 802.11b on routers sometimes results in a more stable signal on the device.
     
  14. mvancil

    mvancil Member

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    Setting it to a B signal will boost the range that it can cover, and if thats what it takes...you might have some other factor in the situation.

    Older homes may have lead based paint which would degrade a signal badly. Another unexpected item you might find is that a straight line between the device and router could have a mirror between it. You'd be surprised how often I see that.

    Also, with these tablets, I've noticed that setting the beacon to a value of 75 has increased stability with some chipsets. Usually Linksys based routers.
     
  15. mvancil

    mvancil Member

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    Another thing to consider...if you drop it to a B connection, you will slow the data transfer rate between devices in the home. Unless you have something faster than a 10MB pipe to the house, the Internet should be fine. However, if you have a media server or transfer large files between devices, this might not be the best way to go.
     

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