Help : Where is the demodulation blocks implemented in gnuradio [ GMSK,PSK etc]

GNU Radio
1

Hi guys ,
I Just want to confirm a thing regarding the demodulation of the
digital
dat in the gnuradio as the signals are received from the usrp. The doubt
are,

  1. Where is the demodulation is implemented in the gnuradio .
  2. What demodulation is implemented by default in the urp_rx_cfile …
    please do help me someone in clearing my doubts .

Thanks

–
Phenomenon

Life is the most precious phenomenon ever happen …

Lets pray and give emotional strength to the innocent brave victims of

japan

they are human and m also a human which implies we are one.

2

On Thu, 2011-04-07 at 20:04 +0530, ton ph wrote:

Hi guys ,
I Just want to confirm a thing regarding the demodulation of the
digital dat in the gnuradio as the signals are received from the usrp.
The doubt are,

  1. Where is the demodulation is implemented in the gnuradio .

In any of the demodulation blocks. AM demod, FM demod, PSK demod, etc.

  1. What demodulation is implemented by default in the
    urp_rx_cfile …

None.

3

On 07/04/2011 10:34 AM, ton ph wrote:

Hi guys ,
I Just want to confirm a thing regarding the demodulation of the
digital dat in the gnuradio as the signals are received from the usrp.
The doubt are,

  1. Where is the demodulation is implemented in the gnuradio .
  2. What demodulation is implemented by default in the urp_rx_cfile …
    please do help me someone in clearing my doubts .

Thanks
Gnu Radio is a generic digital-signal-processing framework. Which
includes many pre-built processing blocks, including demodulators
and modulators, correlators, detectors, etc, etc.

There is no default demodulation scheme anywhere in the basic
architecture, and usrp_rx_cfile is used to simply copy samples as they
come off the USRP hardware into a file.

The USRP hardware doesn’t do any demodulation–the signal you see
delivered to the host PC is just filtered/decimated baseband
samples as they come off the ADC, appropriately scaled for use inside
Gnu Radio. The USRP hardware doesn’t know anything
about modulation or demodulation, per se. All of that is the
responsibility of the host software. Correspondingly, the transmit
side of the USRP hardware doesn’t know anything about modulation,
either. It is entirely up to the host software to provide
appropriately-modulated samples for the hardware to dutifully turn
into analog signals and then (usually) up-convert to the
desired RF band of interest. Generally, the host interface operates
in “baseband” mode–the (complex) samples are centered at DC.

Cheers

4

Thanks nick for your immediate reply , if we have different demodulation
modules and as i have learnt recently that usrp/gnuradio does not do
any
default demodulation , than what captured file from usrp_rx_cfile
contains
… is that the captured file contains the complete baseband information
present in a particular frequency … and as per the demodulation block
applied to the captured file , we get the required information.
Thanks.

On Thu, Apr 7, 2011 at 9:51 PM, Nick F. [email protected] wrote:

urp_rx_cfile …

Life is the most precious phenomenon ever happen …

–
Phenomenon

Life is the most precious phenomenon ever happen …

Lets pray and give emotional strength to the innocent brave victims of

japan

they are human and m also a human which implies we are one.

5

Thanks Marcus for your valuable information .
Now as per you have said that the usrp/gnuradio doesnt do any default
demodulation , that means if i apply a demodulation technique to the
captured file from usrp_rx_cfile.py , i will get the required output.For
example if i apply GMSK demodulation to the captured file i ll get the
properly formatted output as per the GSM protocol … right.
Thanks

On Thu, Apr 7, 2011 at 10:02 PM, Marcus D. Leech [email protected]
wrote:

Thanks
to the host PC is just filtered/decimated baseband

–
Phenomenon

Life is the most precious phenomenon ever happen …

Lets pray and give emotional strength to the innocent brave victims of

japan

they are human and m also a human which implies we are one.

6

the demodulation and modulation is done in GNU Radio. the raw digitized
signal from USRP will be proccessed by gnu radio either we want to
filtered, do FFT, demodulate and etc. all is done using GNU Radio.

USRP is the hardware to interfare the digital world with the analog
world…

anil ph wrote:

wrote:

please do help me someone in clearing my doubts .
come off the USRP hardware into a file.
either. It is entirely up to the host software to provide

Life is the most precious phenomenon ever happen …

Mohd Adib Sarijari
Universiti Teknologi Malaysia
www.fke.utm.my
www.utm.my

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