Hi all,
I've attached an image of my flowgraph and the figures it produces to coincide with the following.
I would like to do two things to a BPSK radio implementation. One is feed an SNR estimate to the Costas Loop to improve performance at low SNR. The second is display the measured SNR to a user in the GUI. I'm using the MPSK SNR Estimator Probe to generate SNR messages and feeding that into the Costas Loop, simple enough.
Question 1: Where do you place the estimator block in your flowgraph? Currently, I have it estimating SNR based on the input to the Costas Loop, but I could make estimates based on the stream coming right out of the USRP Source. Does it matter/help/hurt?
Question 2: What type of SNR estimator from this block do people with experience find works best? Welcoming recommendations. In the simple flowgraph attached, I find Simple, 2nd and 4th Moment and SVR produce relatively close estimates, while Skewness is way off and sometimes produces NaN.
Question 3: How do I turn the SNR Estimator messages into a stream that I can pass to QT GUI blocks? I've tried the PDU to Tagged Stream and the Message Source blocks, but they don't work for this purpose. I just get streams of 0's or can't use the block at all (Message Source is the wrong kind of message input). Using the Message Debug block shows the output of the estimator is not 0, which you can see in the terminal of the attached flowgraph image.
Thank you for the help,
Rich
SNR Figures.png
SNR Flowgraph.png