help in modulation detection in SDR

[Shruti01]

Given a received signal samples, the objective is to determine the modulation scheme that is present in the signal and demodulate data if required.

Example : Assume that we know that the received signal contains one of the two schemes BPSK or QPSK in the presence of noise. The problem is to say which is present. How to go on with this problem statement. What will be the good solutions.

 

[heyo]

Assume that we know that the received signal contains one of the two schemes BPSK or QPSK in the presence of noise.

You also know the Baud rate and encoding? I assume BPSK31 Varicode and QPSK31 Varicode?!
If yes, why not demodulating and decoding both and decide on the decoded output text?
For programmatic decision you may look for "CQ"s or other well known words. A simpler alternative would just present both texts to the user and let him decide. This way one could utilize "error correction" of the human eye - and eliminate false (automatic) decision.

 

[Shruti01]

Could you please elaborate more about it.....


Thanx...

 

[heyo]

sorry - i'would not know what part to elobarate. please write which part you did not understand!

[ howto write a private message in this forum? ]

 

[Shruti01]

Could you explain me the alternative which you have suggested.


Thanx..

 

[MSM_Maria]

Hello Shruti01.

Please look at these links, maybe it will help You

Signals Analyzer`s (SA) description in English
Signals Analysis

In general case, Your question is typical task of analysis.

 

[Shruti01]

I have do signal analysis coding. Could you help me out with the coding in matlab.....

 

[MSM_Maria]

Sorry, we are talking about different things. Determine the mode of modulation/manipulation some unknown signal(e.g. PSK-2, PSK-4, QAM, OFDM, C4FM etc) and direct analysis of the bitstream a bit different things. I'm sorry again.

 

[Shruti01]

Could you tell me how to do the coding in matlab for determination of modulation scheme.....

Thanx