Difference between signal strenght and quality?

[mahesh18]

Hi all,

As per Cisco documentation

Low RF signal strength does not mean poor communication.

Low signal quality does mean poor communications.

If someone can explain me difference  between signal strength and signal quality?

As per my home AP  i can see that signal strengh is measured in numbers like 50 %  or 100%.

But what is signal quality and how me measure it ?

thanks

mahesh

[George Stefanick · Accepted solution]

Great question ....

First, lets look at the concept of signal quality and strength ... Suppose for a minute you are front row at a rock concert right next to the speakers. The sounds is so loud you cant hear anything but screaming. This is an exmaple of a loud signal but poor quality.

As for measuring the signal and noise or should we say quality of signal. Vendors sometimes give you a % or dB scale when grading the signal.You really cant make headers or tails from the % scale becuase each vendor has different % measurements. But check your ap, becuase you may have the option to change it to dB.

Lets look at dBm. Right now my client is showing:

Signal -59 dBm

Noise -98 dBm

The dB scale is simple. The lower the dB the LOUDER the signal. You will see -59 of signal is good, in fact I am about 50 feet from the AP. If you are right under the ap you will get like a -30ish. Noise, we dont want to be loud, so we want to see noise at -100. The lower the noise dB the louder the noise is.

So back to out example above. Next to the speaker, you are showing say -30dBm but your noise may be like -70dBm...

Does this make sense?

You normally like to see your signal no higher than -67 for voice or -76 for data. And your noise should be higher than -90.

[mahesh18]

Hi George,

Many thanks for great explanation with very good example.

regards

mahesh