Re: packetized audio transmission using GMSK modulation

[Marcus Müller]

Hi Amir,

regarding the spectrum: Is your data white?

Best regards,
Marcus

On 10.08.20 21:40, Amir Hossein Aalipour wrote:
> I could finally find the correct configuration. I just added a "pack k
> bits" block between the "gmsk demod" and "correlate access code" blocks. I
> found it while I was monitoring and comparing the input and output
> waveforms of the mod and demod blocks. As was written in the gmsk demod
> document, this block produces a stream of bits, one bit per byte and the
> bit is written on the LSB of the corresponding byte. So I searched for a
> block that extracts one bit from a byte and the result was "pack k bits"
> which takes one bit from every input byte and puts the k bits that have
> been taken, in a row beside each other. It worked!
>
> But when I saw the spectrum of the modulated signal, i.e the output of the
> gmsk mod, it was not a well-known bell-shaped spectrum around zero Hz! It
> was like the picture below. Why is it like that?
>
> Sorry for too many questions, can I also ask how to set the right sampling
> rate of the USRP sink? I mean according to a flow graph like the below
> transmitter, how can I calculate the sufficient sampling rate of the USRP
> sink? Any hint is appreciated.
>
> Thank you very much.
>