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What Do Cell Phone Signal Bars Really, Really Mean?

What Do Cell Phone Signal Bars Mean?
We need to jump in here and stop the spread of some misinformation. A story that started as a round of Ask Metafilter (a blog that seeks answers by harvesting the minds of commenters) has been picked up by a number of big name blogs. We're not sure if the others went back and read the original post, or if they all just got their info from the first blog to pick it up, but they all managed to get the facts wrong.

We're about to get a little technical here, but read along. This is actually pretty interesting stuff if you like to know how your cell phone works.

The question? "What exactly do those cell phone reception bars represent?" The answer is a technical explanation, that is admittedly not very clearly phrased, but careful reading reveals that despite what others are reporting, cell phone signal bars do not represent noise floor levels or EC/I0, which essentially represents the amount of usable signal a cell phone has.

EC/I0 (ee see over eye naught) plays an important role in your ability to place a call, but due to wild fluctuations, you would never see it visually represented on a phone in the form of bars. If EC/I0 were measured, your signal would vary constantly from 4 bars to 1 bar and back, often in a matter of seconds. This would be very unsettling to the user. Instead, the bars measure absolute signal strength, which is measured in dBµV/m, or decibel-microvolts per metre.

The problem with measuring cell reception is that there is no industry standard for measuring signal strength. What is 2 bars on one phone may be 4 bars on an other. This can vary even among phones from the same manufacturer. Additionally, EC/I0 measurements can have more of an influence over reception than signal strength. That is even if you have 4 bars sometimes you'll be unable to place a call, but occasionally be able to place a call fine with no interference, even with no bars.

So the simple answer to ""what exactly do those cell phone reception bars represent?" Nothing of much value.

From Ask Metafilter

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Tags: bars, cell phone, CellPhone, mobile, noise floor, NoiseFloor, reception, signal, signal strength, SignalStrength

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