Noise Power Estimation in Packet-based Digital Link Example

[YYYs]

Hey everybody,

since nobody has answered this question (https://decibel.ni.com/content/docs/DOC-18801#comment-24601). I would like to ask the same question on this board. 

Could someone please explain the sub_est_noise_power.vi within the Packet-based Digital Link Example?

Any help is appreciated.

Best regards

[Anthony_F]

Hello YYYs,

I've recently read through that same subVI and asked the same question.  Here is what I believe:

An idea input to the SubVI will contain both a "large" amplitude signal and also "small' amplitude noise, separated in time like this:

The subVI then divides the signal into chunks and computes the average of the magnitude squared (roughly related to average power).

With enough samples of noise and enough samples of signal, the minimum of the array should be the average noise power and the maximum should be the average power of the signal.

The MathScript version is actually a little easier to "read" Find the file named sub_est_noise_power - MS.VI

[edwardfu]

i have modified a little bit to the example to serve my purpose that measuring bit error rate.i have add some matlab code in the receiving part to compare the receving data with original data in binary number in order to get the BER.the example works perfectly which i incresed the tx gain and BER drops.but there is one problem which talking about BER we have to find the coesponding signal to noise rato to indicate how it will react. and the SNR that i calculated is from the sub vi noise estimate chop part but when tx gain is increased the ber dropped the SNR dropped too.here doesn't make any sense.or maybe the reading from that part is not real power level of signal and noise?? if so how should i find the real reading of the power level of noise and signal?please help me understand better to find the correct way calculate SNR.thanks a lot.

[Alex550]

To the best of my knowledge,  some people would use the simplest way to directly calculate K*T to evaluate the level of noise power, where K denotes the Boltzman constant, and T denotes the Kelvin Temperature. But It is just a kind of theoretical estimates.  There are different algorithms to estiamte the practical SNR, but I am not a expert on that.