Comment 33 for bug 481432

Nice program there -- I've never used wavemon before. In all my previous tests, I was just repeatedly issuing iwconfig and averaging the results.

I don't see the same results as you, where your signal repeatedly drops really low. I do get the occasional drop in signal quality, but it's neither as pronounced nor as consistent as what you see. Still, the basic effect is the same. Ubuntu doesn't properly sense wireless signals, and thus connection quality fails. I wouldn't be surprised if your occasional drop in signal quality is enough to kill your connection, especially if it lasts for more than a second.

I've mentioned that I want to figure out what the broadcast power is under Vista. I couldn't find any way to directly measure how much power is being sent to my wireless card under Vista, but I designed a test that effectively tells me the same thing. I logged into my WAP/Router, and found a tool which reports the signal quality of devices communicating with the WAP. The tool does not report signal quality in dB or nW, but rather as a percentage (of the theoretical best connection quality).

So, I went to various locations around my house, started pinging google with my laptop, and looked at the signal quality as reported by the WAP. Note that the location numbers below correspond with the location numbers I gave in post #29.

Location 1
Ubuntu: 100%
Vista: 100%

Location 2
Ubuntu: 90+%
Vista: 99-100%

Location 3
Ubuntu: 100%
Vista: 100%

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So what does it all mean? Here's my best shot at interpreting these numbers thus far.

If a computer and WAP are having trouble communicating, then there are four possible problems.
1) WAP is not properly sending a signal.
2) WAP is not properly receiving a signal.
3) Computer is not properly sending a signal.
4) Computer is not properly receiving signal.

I know, this is really broad so far, but stick with me for a few paragraphs.

Case 1 and 2 are immediately ruled out. There are several different wireless devices in my house which use the WAP. My iPod touch, two other family members' laptops, and my own laptop (running Vista) all communicate with the WAP just fine. If the WAP was not properly sending or receiving signals, all the other people in this household would be having problems, too. Furthermore, my computer only has problems when running Ubuntu, further indicating that the problem lies with a particular computer, not the WAP.

Case 3 is also ruled out. Why? Well, the tests I just performed indicate that the WAP receives signals just fine, whether Vista or Ubuntu is broadcasting those signals. I verified this empirically in this post. The absolute lowest quality signal that the WAP sensed was 90%. A signal quality that high should be just fine for communication.

Furthermore, I did some research on the intertubes, and several technical folks seem to think that 100mW of power being sent to a wireless card is more than enough. As I understood it, 80mW of power is the point of diminishing returns -- send more power than that to a wireless card, and you're not getting much benefit. They were even discussing using 30 to 40mW of power in wireless cards. Therefore, the 100mW of power that Ubuntu sends to my wireless card should be plenty enough.

So far, cases 1, 2, and 3 are ruled out. My WAP is working just fine (case 1 and 2), and a strong enough signal is being sent to from my laptop (case 3). That leaves case 4: Ubuntu is not properly receiving signals. I verified this empirically in post #29. Now, why and how Ubuntu fails to receive signals is up for debate. Perhaps, as Smot indicates, Ubuntu is simply under-estimating signal strength. Maybe Ubuntu tells the wireless card to listen to the wrong frequency/channel. This is, by the way, possible: the frequencies defined for use in the 802.11 standard are SO close that one could be listening on channel 10 and receive signals on channel 11.

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Well, that was a long-winded way of saying that Ubuntu has problems. :'(

Thanks for the feedback, Smot.