It’s What’s Always There
The idea of the noise floor is pretty fascinating to me. The noise floor is the total sum of signals detected in a given frequency range. It’s the white noise, the static that’s just there. Lot’s of things contribute to it: microwaves, distant thunderstorms, cosmic radiation, and your neighbor’s quadcopter drone.
It’s the Noise at the Party
The noise floor makes it harder or easier for wireless protocols to detect a signal. It’s kind of like the ambient noise at a work party making it difficult to hear your colleague. If the noise around your conversation is too loud (or high) then you won’t be able to make out the words (signal) that your friend is saying to you. However, if the noise around is suddenly quieter and the noise level much lower, then you can make out your friend’s words much easier even if they are speaking at the same volume.
It’s the Pile of Your Carpet
And so it is with the noise floor. If a signal is transmitted in a noisy environment, one in which the noise floor is high, then it is more difficult to detect the signal in the noise, it blends in. If the signal is louder than the noise, it is easily detected. Having a high noise floor is like dropping a pencil in a very, very plush carpet. Having a low noise floor is like dropping the pencil on a commercial grade carpet with low pile.
The noise floor is measured in dBm. “The unit dBm denotes an absolute power level measured in decibels and referenced to 1 milliwatt (mW).” Thank you isa.org. When comparing the noise floor level in one environment versus another you would say something like city A has a noise floor of -105 dBm and city B has a noise floor of -76 dBm. The lower (or more negative) the noise floor, the better. It’s like having lower carpet pile so the pencil (signal) more easily sticks out.
It Represents All the Interference
Perhaps the biggest takeaway for anyone using wireless technology is that the noise floor represents the interference levels in a given place over a given frequency range. It is the total sum of noise in that area and frequency range. Thus, if your technology is able to successfully detect signals with that noise floor, it has dealt with many of the RF issues in that environment. In my next post, I’ll discuss what this means for technologies trying to send wireless messages.