[USRP-users] 4*4 MIMO

Ben Hilburn ben.hilburn at ettus.com
Thu Sep 13 18:33:56 EDT 2012


Many architecture questions are described in the datasheet for the N210,
which you can find on the product page:
https://www.ettus.com/product/details/UN210-KIT

The ADC in the N210 is the ADS62P44.

Cheers,
Ben
----------------------------
Ben Hilburn <http://goo.gl/5DdZ3> @ Ettus Research, LLC<http://www.ettus.com/>
 |   USRP <http://goo.gl/Ixjhh>



On Thu, Sep 13, 2012 at 3:03 PM, Farrukh Aziz <farrukh59th at yahoo.com> wrote:

> Hi Ben, I am sorry for not being very precise initially. Yes I am doing a
> synchronized receiver only. I am trying to receive 4 synchronized complex
> data streams. In doing this I only require time and frequency
> synchronization whereas phase synchronization is not required.
> I want to clarify further on how this is done inside. USRP (N210) has two
> ADCs, so this feeds two real signals into the FPGA at 12.5 MHz IF.
> Downcoversion to baseband is performed inside the FPGA, where a
> cos(2*pi*f*t) and sin(2*pi*f*t) generated from NCO are multiplied, thus
> generating two IQ pairs at baseband. 1) What is the sampling interval 't'
> 2) Which chip is used in ADC?  This link shows my question.
> http://tinypic.com/view.php?pic=35bihi0&s=6
>
> *Farrukh Aziz Bhatti*
> PhD Candidate
>
> Department of Electrical & Computer Engineering
> University of Auckland
>
> +64 21 02973964
>
>
>
> --- On *Thu, 13/9/12, Ben Hilburn <ben.hilburn at ettus.com>* wrote:
>
>
> From: Ben Hilburn <ben.hilburn at ettus.com>
> Subject: Re: [USRP-users] 4*4 MIMO
> To: "Farrukh Aziz" <farrukh59th at yahoo.com>
> Cc: "USRP user forum" <usrp-users at lists.ettus.com>
> Received: Thursday, 13 September, 2012, 10:32 PM
>
>
> Hi Farrukh -
>
> I had originally interpreted your question to mean you wanted to use only
> TVRX2s to achieve a full 2x2 MIMO system.  After re-reading your question,
> however, I just realized that you may have been asking if you could use
> TVRX2s for the receive portion of a full MIMO setup, while using a
> different radio / USRP / daughterboard / etc for the transmit portion.
>
> If this is your question, then YES, you are correct in your understanding.
> Please pay careful attention to the synchronization notes I linked to you
> before, as they will be critical to using the TVRX2s appropriately.
>
> Sorry for the confusion!
>
> Cheers,
> Ben
> ----------------------------
> Ben Hilburn <http://goo.gl/5DdZ3> @ Ettus Research, LLC<http://www.ettus.com/>
>  |   USRP <http://goo.gl/Ixjhh>
>
>
>
> On Thu, Sep 13, 2012 at 10:20 AM, Ben Hilburn <ben.hilburn at ettus.com<http://mc/compose?to=ben.hilburn@ettus.com>
> > wrote:
>
> Farrukh -
>
> You cannot do MIMO, of any size, with the TVRX2, because the TVRX2 is
> receive-only.
>
> You can receive synchronized samples across two boards, although the
> boards will not maintain relative phase after a tune.
>
> Please see:
>
> http://files.ettus.com/uhd_docs/manual/html/sync.html
>
> Cheers,
> Ben
> ----------------------------
> Ben Hilburn <http://goo.gl/5DdZ3> @ Ettus Research, LLC<http://www.ettus.com/>
>  |   USRP <http://goo.gl/Ixjhh>
>
>
>
> On Tue, Sep 11, 2012 at 3:35 PM, Farrukh Aziz <farrukh59th at yahoo.com<http://mc/compose?to=farrukh59th@yahoo.com>
> > wrote:
>
> Hi, I was looking at this (new) document that shows different ways of
> making a MIMO system.
> http://www.ettus.com/content/files/kb/mimo_and_sync_with_usrp.pdf
>
> Since it did not discuss one of the options that I have used, so I thought
> to clarify myself. Can we implement a 2*2 MIMO by using a TVRX2
> daughterboard on a USRP N210 without using any external reference signals?
>
> Secondly can we implement a 4*4 MIMO by using 2 USRPs (N210) each fitted
> with a TVRX2 daughterboard. The USRPs are inter linked with a MIMO cable.
> The 1 PPS and 10 MHz synch signals are provided using a GPSDO (to the
> master node). However the GPSDO is not connected with a GPS antenna.
>
> Please let me know if my approach is correct.
>
> *Farrukh Aziz Bhatti*
> Department of Electrical & Computer Engineering
> University of Auckland
>
> +64 21 02973964
>
>
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>
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>
>
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