[Discuss-gnuradio] hestimate matrix in Alamouti OFDM communication

[Vanessa Gardellin]

I noticed that the hestimate matrix in the 2x1 ofdm alamouti
communication has crazy values like:

sym: -0.0020 + j-0.0018  ks: -1.0000 + j+0.0000  eq: +282.3798 +
j-254.7796  ==>  -1.0000 + j+0.0000
sym: +0.0017 + j+0.0022  ks: +0.0000 + j+0.0000  eq: +811.7408 +
j-449.4426  ==>  +2.3752 + j+1.0470
sym: +0.0006 + j+0.0003  ks: +1.0000 + j+0.0000  eq: +1341.1019 +
j-644.1057  ==>  +1.0000 + j+0.0000
sym: +0.0001 + j+0.0005  ks: +0.0000 + j+0.0000  eq: +656.4164 +
j-71.1795  ==>  +0.0770 + j+0.3318
sym: -0.0001 + j-0.0020  ks: +1.0000 + j+0.0000  eq: -28.2691 +
j+501.7466  ==>  +1.0000 + j+0.0000

meanwhile when I use a 1x1 ofdm communication I have pretty regular values

sym: -0.0254 + j-0.0084  ks: -1.0000 + j+0.0000  eq: +35.4218 +
j-11.7727  ==>  -1.0000 + j+0.0000
sym: +0.0004 + j+0.0049  ks: +0.0000 + j+0.0000  eq: +33.7460 +
j-10.3629  ==>  +0.0633 + j+0.1618
sym: +0.0289 + j+0.0081  ks: +1.0000 + j+0.0000  eq: +32.0702 +
j-8.9531  ==>  +1.0000 + j-0.0000
sym: -0.0011 + j+0.0022  ks: +0.0000 + j+0.0000  eq: +31.4286 +
j-12.1152  ==>  -0.0078 + j+0.0822
sym: +0.0261 + j+0.0129  ks: +1.0000 + j+0.0000  eq: +30.7870 +
j-15.2773  ==>  +1.0000 + j+0.0000

do you have any idea why this happens?

Any help will be appreciated

Vanessa


On Wed, Nov 9, 2011 at 9:44 AM, Vanessa Gardellin
<address@hidden> wrote:
> 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 Rondeau <address@hidden> wrote:
>> On Tue, Nov 8, 2011 at 4:51 AM, Vanessa Gardellin
>> <address@hidden> 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
>>
>>
>>>
>>> On Thu, Oct 27, 2011 at 9:33 AM, Vanessa Gardellin
>>> <address@hidden> 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.
>>> >
>>> > 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...
>>> >
>>> >>
>>> >>>
>>> >>> 2) 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.
>>> >>
>>> >>>
>>> >>> 3) what "-M_TWOPI*freq_delta*d_cplen/d_fft_length" represents?
>>> >>
>>> >> This is the integer number of subarriers (freq_delta) and the phase
>>> >> correction per subcarrier.
>>> >>
>>> >>>
>>> >>> Thank you
>>> >>>
>>> >>> Vanessa
>>> >>
>>> >> 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: address@hidden
>>> > 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: address@hidden
>>> 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: address@hidden
> 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: address@hidden
WWW: http://www.iit.cnr.it/staff/vanessa.gardellin/
Skype: gardellin.vanessa