Mobile Phone Signal And Battery Meters

Why does the first bar of the battery life take 36 hours to go away, and the other 3 seem to vanish in 10 minutes? How do my calls get dropped when I CLEARLY have full bars? Read on m'friend.

Battery Meters

We're in a world that sends robots to outerspace, has cured innumerable diseases, and FINALLY allows us to play Super Monkey Ball using accelerometers on a portable device - you'd think we'd be able to measure the amount of charge on a battery. Truth is, we can - and accurately too. But you'd never know it in your every day life...36 hours to dissipate all the power, but plug it in for 10 minutes and miraculously it appears that you're back to full strength? How can that be? We all know it's not actually back to full (or >80% as the bars would suggest), so what is actually going on? Marketing.

Like everything else, that battery meter is controlled by software, and that software is controlled by humans - at least for now. In related news...

Signal vs. Noise

We all know AT&T's pitch, "More Bars in more Places," but what does that really mean? We've also all had calls dropped only to look down at the phone to notice "full bars." The issue is that the meter only tells one half of the story.

When your phone is on standby and you're likely to look at the meter, those "bars" are the combination of two factors: the raw signal strength received from the cell tower, and the signal to noise ratio (the SNR) - essentially, how well the tower can hear your phone based on how much other noise (data) you are competing with. The SNR is by far the most significant component in determining call quality, but because the SNR is constantly changing the phones display a blend of the two measurements, and are set to give far too much weight to the signal strength of the tower.

When you are actually on a call, your phone and the tower are in in two-way communication, and the meter reads more precisely, but you're generally not looking down at the meter at those times.

When you see full bars, what you're seeing is that your phone is hearing the the local signal loud and clear, but what is not shown is if the tower can hear your phone shout back. Throughout your call, the amount of data being sent to your tower can change frequently, and when a deluge hits, it's as though you're pissing into a waterfall. In this case, you're not actually being lied to, just selectively informed. More marketing.

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Homeland Security: We can seize laptops for an indefinite period

The U.S. Department of Homeland Security has concocted a remarkable new policy: It reserves the right to seize for an indefinite period of time laptops taken across the border.

A pair of DHS policies from last month say that customs agents can routinely--as a matter of course--seize, make copies of, and "analyze the information transported by any individual attempting to enter, re-enter, depart, pass through, or reside in the United States." (See policy No. 1 and No. 2.)

DHS claims the border search of electronic information is useful to detect terrorists, drug smugglers, and people violating "copyright or trademark laws." (Readers: Are you sure your iPod and laptop have absolutely no illicitly downloaded songs? You might be guilty of a felony.)

This is a disturbing new policy, and should convince anyone taking a laptop across a border to use encryption to thwart DHS snoops. Encrypt your laptop, with full disk encryption if possible, and power it down before you go through customs.

Here's a guide to customs-proofing your laptop that we published in March.

It's true that any reasonable person would probably agree that Customs agents should be able to inspect travelers' bags for contraband. But seizing a laptop and copying its hard drive is uniquely invasive--and should only be done if there's a good reason.

Sen. Russell Feingold, a Wisconsin Democrat, called the DHS policies "truly alarming" and told the Washington Post that he plans to introduce a bill that would require reasonable suspicion for border searches.

But unless Congress changes the law, DHS may be able to get away with its new rules. A U.S. federal appeals court has ruled that an in-depth analysis of a laptop's hard drive using the EnCase forensics software "was permissible without probable cause or a warrant under the border search doctrine."

At a Senate hearing in June, Larry Cunningham, a New York prosecutor who is now a law professor, defended laptop searches--but not necessarily seizures--as perfectly permissible. Preventing customs agents from searching laptops "would open a vulnerability in our border by providing criminals and terrorists with a means to smuggle child pornography or other dangerous and illegal computer files into the country," Cunningham said.

The new DHS policies say that customs agents can, "absent individualized suspicion," seize electronic gear: "Documents and electronic media, or copies thereof, may be detained for further review, either on-site at the place of detention or at an off-site location, including a location associated with a demand for assistance from an outside agency or entity."

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