Your Computer and Cell Phone Are Lying To You

Ant writes with a story from Dan's Data, which says that the battery meter and connection-strength displays in your portable electronics are lying to you, "and not just when they whisper to you in the night." Quoting: "Mobile phones, and most modern laptops, have signal strength and battery life displays. One or both of these displays has probably been the focus of all of your attention at one time or another. Neither display is actually telling you what you think it's telling you. The signal strength bars on a mobile phone or laptop do, at least, say something about how strong the local signal is. But they don't tell you the ratio between that signal and the inevitable, and often very considerable, noise that accompanies it ..."

Comments

Wifi meters

[lisaparratt]

Exsqueeze me?

I've written a wifi signal strength meter for an embedded product. During my research, I found it was pretty much standard to base the bumber of bars on the signal to noise ratio, not the raw signal strength.

Re:Wifi meters

[tlhIngan]

I've written a wifi signal strength meter for an embedded product. During my research, I found it was pretty much standard to base the bumber of bars on the signal to noise ratio, not the raw signal strength.

... which is then overruled by the marketing department because brand 'B' only uses the signal strength, so that makes your product look bad when compared side-by-side, since theirs has more signal bars.

In the case of cellphones, it's the carrier that determines how the bars map to signal strength (or quality, if it's possible to estimate). Some carriers demand that you show 5 bars down to a really pathetic signal strength value (I've seen close to -100dbi - just as a quick comparison, most wifi chipsets lose all connectivity between -80 to -90dbi, and the best tend to disconnect around -96dbi). The headroom between that and when the baseband loses the signal completely isn't that much.

Which is why I laugh when I hear "More bars in more places". It's easy to get a "stronger" signal if you mandate that a phone must show more bars all the time.

Now, this was for a non-GSM phone, so it was mandatory to get carrier qualified. But GSM carriers are equally bad, except they don't have as much control since you can bring in any compatible phone onto the network. The only thing the carrier can claim is their phones get a "better" signal (see? more bars than your phone!).

I wonder if Apple had to jump through these hoops with the iPhone or just said to the carriers to screw it - they're designing the software their way and that includes battery and signal strength meters that make sense. Given what I see of cellphones, there's often a special baseband/firmware build for each carrier to cope with the differences... but the iPhone software seems to be either unified, or just a single build around the world. (Carriers oblige because the customers want the phone).

Laptop Battery Dying Too Soon

[Renegade Lisp]

This article gives me a hunch why my no-name laptop battery dies so quickly even when Ubuntu still thinks it has 10% charge and several minutes left. Didn't happen with the manufacturer's battery...

Ubuntu usually does an excellent job analysing how good your battery really is (not sure if it's the kernel ACPI or HAL or GNOME that's actually doing it). But when the battery lies so blatantly, it seems even Ubuntu can't keep my laptop from sudden death without a proper warning or shutdown.

Batteries

[fitten]

Dan doesn't seem to know much about batteries. Check out batter power discharge curves and such...
  http://www.mpoweruk.com/performance.htm Remaining power is estimated based on the charge of the battery. If you notice on those graphs, when you get out to the end of the stored charge, it drops off very quickly, which is why the gauge goes from half to empty quickly.

Grey-ware needs input.

[Therefore I am]

It really does not matter what these meters say as long as they are consistent. From long experience, my grey-ware then interprets the bars to give me a realistic expectation of battery life or signal strength. Move along now please. Nothing of interest here.

Re:[Citation-Needed]

[dotancohen]

Car manufacturers so the same thing with the gas gauge. the top half is more than the bottom half. If the gauge on my car is sitting at half, I'm down to 24 Litres out of a 60 Litre tank. Also, there's a gallon or two left when the needle is at E.

Cadillac invented this in 1984 when they rolled out the electronic gauges which were linear. Customers complained about bad mileage despite the car being thriftier than it's predecessor. Some research showed that they were going by *how*often* they were filling up, not by *how*much*. So they made the gauge logarithmic and allowed another unaccounted for gallon at the end for safety.

Re:gauges

[compro01]

They REALLY should bring that back, Hell, all manufacturers should put that kind of thing in their cars. I can't think of a better way to make going for high mileage widely "cool". Like trying for the high score on an arcade game.

"Hey, guess what? I got 48MPG on my way to work!"
"Oh yeah? Well I got 52MPG! Beat that!"

Just simply harnessing people's competitive drive (not to mention the desire to save money) could do more than all the hybrids in the world, though that would likely lead to people buying hybrids in a quest for ever higher mileage.