Coarse Frequency and related stuff

GNU Radio
1

Dear all,

I am trying to use the alamouti code implemented by trondeau.
Studying the gr_ofdm_frame_acquisition I found several concepts that
are not clear to me:

  1. d_phase_count: what does it mean?

  2. coarse_freq_comp(int freq_delta, int count): which is the meaning
    of this function?

  3. what “-M_TWOPIfreq_deltad_cplen/d_fft_length” represents?

Thank you

Vanessa

On Fri, Oct 21, 2011 at 1:39 PM, Vanessa Gardellin
[email protected] wrote:

   num_channels=2,

Moreover, it’s not clear what channels are and how I should address
the 2 devices.

Thanks

Vanessa

–
Vanessa GARDELLIN, Ph.D.
Researcher
Institute for Informatics and Telematics (IIT),
Italian National Research Council (CNR)
Via G. Moruzzi 1
56124 Pisa - ITALY
Phone: +390503153267
Room: B65/c
E-mail: [email protected]
WWW: http://www.iit.cnr.it/staff/vanessa.gardellin/
Skype: gardellin.vanessa

2

On Wed, Oct 26, 2011 at 11:00 AM, Vanessa Gardellin <
[email protected]> wrote:

Dear all,

I am trying to use the alamouti code implemented by trondeau.
Studying the gr_ofdm_frame_acquisition I found several concepts that
are not clear to me:

Wow, this code is pretty old, and we never did finish it. I hope you get
it
working! I’d love to see the results.

  1. d_phase_count: what does it mean?

We have a look up table for various phase rotations to use in the
calculations instead of recalculating them every time. This is the index
into the LUT.

  1. coarse_freq_comp(int freq_delta, int count): which is the meaning
    of this function?

If the frequency offset is larger than a subcarrier spacing, we want to
correct for that. Once the number of subcarrier offset is found, we use
this
function to recenter it. The fine frequency correct has already been
taken
care of to center the signals to the center of a subcarrier.

  1. what “-M_TWOPIfreq_deltad_cplen/d_fft_length” represents?

This is the integer number of subarriers (freq_delta) and the phase
correction per subcarrier.

Thank you

Vanessa

Tom

3

Dear all,

I am trying to use the alamouti code implemented by trondeau.
Studying the gr_ofdm_frame_acquisition I found several concepts that
are not clear to me:

Wow, this code is pretty old, and we never did finish it. I hope you get it
working! I’d love to see the results.

Yes I know… I am trying to implement alamouti and this is the only
thing that I have found… do you know about newer code? and/or
working one?

  1. d_phase_count: what does it mean?

We have a look up table for various phase rotations to use in the
calculations instead of recalculating them every time. This is the index
into the LUT.

In the code you never used “d_phase_lut”… so this explain a lot of
things…

Tom

Thanks

Vanessa

–
Vanessa GARDELLIN, Ph.D.
Researcher
Institute for Informatics and Telematics (IIT),
Italian National Research Council (CNR)
Via G. Moruzzi 1
56124 Pisa - ITALY
Phone: +390503153267
Room: B65/c
E-mail: [email protected]
WWW: http://www.iit.cnr.it/staff/vanessa.gardellin/
Skype: gardellin.vanessa

4

Do you remember which parts you did not implement?

Apparently make the alamouti work is harder than I though…

Thanks
Vanessa

On Thu, Oct 27, 2011 at 9:33 AM, Vanessa Gardellin
[email protected] wrote:

Yes I know… I am trying to implement alamouti and this is the only

care of to center the signals to the center of a subcarrier.

Vanessa
Researcher
Institute for Informatics and Telematics (IIT),
Italian National Research Council (CNR)
Via G. Moruzzi 1
56124 Pisa - ITALY
Phone: +390503153267
Room: B65/c
E-mail: [email protected]
WWW: http://www.iit.cnr.it/staff/vanessa.gardellin/
Skype: gardellin.vanessa

–
Vanessa GARDELLIN, Ph.D.
Researcher
Institute for Informatics and Telematics (IIT),
Italian National Research Council (CNR)
Via G. Moruzzi 1
56124 Pisa - ITALY
Phone: +390503153267
Room: B65/c
E-mail: [email protected]
WWW: http://www.iit.cnr.it/staff/vanessa.gardellin/
Skype: gardellin.vanessa

5

On Tue, Nov 8, 2011 at 4:51 AM, Vanessa Gardellin <
[email protected]> wrote:

Do you remember which parts you did not implement?

Apparently make the alamouti work is harder than I though…

Thanks
Vanessa

I know that we got the 2x1 (2 TX and 1 RX) working, and we did 1x2 with
maximum ratio and equal gain (obviously not Alamouti). I know we were
close
with the 2x2 Alamouti, but we ran out of time and didn’t manage to track
down one of the major bugs. Neither of use has had time since to finish
it.

Tom

6

Thank you.
Unfortunately I am still trying to make the 2x1 working because I can
receive the preamble and compute the estimate matrix but the headers
are always wrong. Did someone solve this problem?

Thank you

Vanessa

On Wed, Nov 9, 2011 at 4:01 AM, Tom R. [email protected]
wrote:

I know that we got the 2x1 (2 TX and 1 RX) working, and we did 1x2 with

thing that I have found… do you know about newer code? and/or

this

WWW: http://www.iit.cnr.it/staff/vanessa.gardellin/
Via G. Moruzzi 1
56124 Pisa - ITALY
Phone: +390503153267
Room: B65/c
E-mail: [email protected]
WWW: http://www.iit.cnr.it/staff/vanessa.gardellin/
Skype: gardellin.vanessa

–
Vanessa GARDELLIN, Ph.D.
Researcher
Institute for Informatics and Telematics (IIT),
Italian National Research Council (CNR)
Via G. Moruzzi 1
56124 Pisa - ITALY
Phone: +390503153267
Room: B65/c
E-mail: [email protected]
WWW: http://www.iit.cnr.it/staff/vanessa.gardellin/
Skype: gardellin.vanessa