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What is Signal-to-Noise Ratio and How to Measure it
#1
What does SNR Mean

Of course, the first thing when asking about how to fix “signal to noise ratio” issues is to delve into just what SNR means. Signal to Noise is a measurement of how much relevant WiFi signal there is compared to any other signals that can get in the way.

Usually, when dealing with WiFi issues, there are two main problems:

Dead spots: Places where our signal can’t reach. This can be because of distance to the WiFi router, the materials the building is made out of, and other related issues. With a dead spot, we just aren’t getting any signal at all.

Signal to Noise ratio: With signal to noise, the WiFi radio signals may be reaching just fine, but there are other radio signals that make it hard to pick out.

Think of each problem like a big room. If I’m on one side, and you’re on the other and you try to talk to me, if your voice is too soft I won’t be able to hear you unless you shout louder. That’s an issue with dead zones or signal strength.

Signal to noise is where we are in the same room, but the room is full of other people. As you try to talk to me, we have to complete with all of the noises other people are making. It doesn’t help if someone else has a voice similar to yours, so I have to figure out when it’s you talking versus someone else.


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Understanding Signal-to-Noise Ratios

SNR isn’t a ratio, as in “there is 75% signal to 25% noise”, but is measured by taking the signal strength and subtracting the noise, not dividing it. Adding to the potential confusion is that the signal is measured in decibels. For those who work in audio, most people consider decibels a measure of sound as in how loud something is.

It gets worse. In WiFi, decibels are measured in negatives. If you remember old grade school math, negative numbers are the ones below 0. So if you have -15 dBm (deciBels per milliwatt), that is a stronger signal than -50 dBm. I know - it’s confusing, but once you get that the *higher* the number, the *weaker* the signal, the better off we’ll be.


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#2
Nice article, thanks.
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