Help regarding identification of modulation(GMSK) type of a signal

i want to identify the presence og GMSK modulation in the incoming
signal at the receiver side. and can u clarify what is meant by. '
relative to what ?PSK ?QAM?Voice?'

i want to identify the presence og GMSK modulation in the incoming
signal at the receiver side. and can u clarify what is meant by. '
relative to what ?PSK ?QAM?Voice?'

   regards,
   ravi

"ravi" <rkant_nitw@rediffmail.com> wrote in message
news:1138745295.249752.68540@f14g2000cwb.googlegroups.com...
> i want to identify the presence og GMSK modulation in the incoming
> signal at the receiver side. and can u clarify what is meant by. '
> relative to what ?PSK ?QAM?Voice?'

What do you know about your input signal? Do you know that it can only
contain GMSK and some other type of modulation or can it contain pretty much
anything and you only want to see if GMSK is present? In the latter case,
you pretty much have to demodulate it assuming that it is a GMSK signal (if
it is GMSK, is it part of the GSM standard or a custom GMSK modulated
signal?). After demodulation, you can use metrics based on the demodulation
to see if you got GMSK or not (say EVM). If your input signal has a lot of
noise, your detection algorithm will need to take that into account as well.

Cheers
Bhaskar

Bhaskar,
Ravi might not know what is EVM - error vector magnitude. Does EVM
exists for GMSK?
I guess we normally measure phase error(RMS(0 to 10 degree) and peak(0
to 40 degree)) for GMSK modulation type and
EVM (RMS(0-20%) and peak(0-40%) for 8PSK modulation. Please correct me
if I am wrong.
Santosh