how to find the SNR of a signal?

[ujjvalshah]

Hi ,

I am doing a project on MIMO (Multiple Input Multiple Output), which involves use of multiple transmitter and multiple receiver antennas for transmission and reception of a single signal.

In this method there is a technique which is called selection combining. In this technique the receiver scans all the receiver antennas and picks the antenna which has the best SNR. Can anyone please tell me that how do the receiver find out the SNR of a given signal?

The most obvious technique that came to my mind is to send pilot symbols which receiver already knows and thus determine the SNR by comparing the received symbols and transmitted symbols.

Is this how SNR is determined or it is something else?

Any help will be really grateful; thanks in advance!

 

[Sceadwian]

Signal-to-noise ratio - Wikipedia, the free encyclopedia
It's all there.
Google is your friend.
Wikipedia helps too.

 

[ujjvalshah]

thanks but i do know the SNR formula,
what my question is how do i find out how much is the noise and how much is the signal information in a single received signal (which is a combination of both - noise and info) at the antenna?

 

[Hayato]

You have to analyse the channel.
And see how much noise power is there, when there is anything being transmitted/received.

 

[Mikebits]

The hard part is to distinguish noise from signal. I think this is done through filtering and advanced DSP processing. Simple method is threshold detect of signal. Strongest signal is used.

https://www.electro-tech-online.com/custompdfs/2009/04/sc2.pdf

Selection Diversity

Diversity combining - Wikipedia, the free encyclopedia

 

[dougy83]

What is being transmitted? For voice, the selector, or 'voter' calculates the 'SNR' based on the power present in, say, 2 frequency bands (of the demodulated signal): the low frequency band (0..2700Hz, say) and the high frequency band (all signal above xx Hz is assumed to be noise).

Real voters use a number of parameters derived from the signal to choose the best signal, e.g. articulation index/depth, signal autocorrellation, SNR', etc.

For SNR of non-speech signals, e.g. data, you might define some method of measuring what you think the signal should be (e.g. frequency at the bitrate and some (sub-) harmonics), and calculate the power. Likewise for the expected noise spectrum part of the signal (everything that's not in the 'signal' part of the spectrum).