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Today's Topics:
1. Sych problem in 4*4 MIMO (Farrukh Aziz)
2. Re: shorten Rx window based on received power (Sanat Gulvadi)
3. Getting separate IQ samples and work with them in GRC
(Lu?s Correia)
4. Re: Sych problem in 4*4 MIMO (Nick Foster)
5. Building UHD using MSVC 2008 (Pol Henarejos)
----------------------------------------------------------------------
Message: 1
Date: Mon, 21 May 2012 01:17:23 -0700 (PDT)
From: Farrukh Aziz <[email protected]>
To: USRP user forum <[email protected]>
Subject: [USRP-users] Sych problem in 4*4 MIMO
Message-ID:
<[email protected]>
Content-Type: text/plain; charset="utf-8"
John,
I had all the settings entered correctly as you have described (so there is no
problem with my USRP settings). However the last thing that I did was to swap
my master and slave nodes, and this solved the problem. I dont know why, but
the issue is now solved and I am getting 4 complex, synchronized data streams.
The system is working properly with the external references (clock and PPS) fed
from signal generators, and it is also working with GPSDO references.
Just wondering if MIMO cable is alike at its both ends.
Thanks
Farrukh Aziz Bhatti
Department of Electrical & Computer Engineering
University of Auckland
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Message: 2
Date: Mon, 21 May 2012 13:02:21 +0200
From: Sanat Gulvadi <[email protected]>
To: [email protected]
Subject: Re: [USRP-users] shorten Rx window based on received power
Message-ID:
<CAH12yLs4rZaiW_=z2cnrejhe+ehx86zim1hwcf9a3jfgnd5...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hello again,
Was rather hoping to get some ideas about this. Maybe I could make it more
to-the-point:
I implemented a sort of energy detector at the receiver so that a presence
or absence of transmission could be detected. The receiver waits say 4
seconds and times out if there is none. Otherwise if it does detect a
transmission, it starts saving the samples to a file. In order to detect a
transmission, I consider each packet and take the mean of the sum of the
squares of the real and imaginary parts of my complex samples and compare
it to some threshold. After trial and error, I worked out some value to use
for the threshold. This algorithm is working but I face some issues when it
picks up some stray transmissions in the air. To fix this, I do it for a
certain number of consecutive packets. But this way, I am sacrificing many
packets. I was wondering if there was a better way to do this. I also
assume that I will each time have to adjust this threshold value depending
on the distance between the devices and the receiver gain etc.
Regards,
Sanat
On Tue, May 15, 2012 at 11:25 AM, Sanat Gulvadi <[email protected]>wrote:
> Good Morning,
>
> I am attempting a wireless transmission between 2 USRP2 rev 4 devices
> using 2 RFX2400 daughterboards connected to 2 different host PCs. There is
> no synchronization between the devices since time and frequency offset
> estimation needs to be part of the receiver algorithm. What I am doing to
> make sure I get what I transmit is :
> *Start Rx-> Start Tx -> Stop Rx after Tx has had sufficient time to send
> all digital data*
> Since the algorithm takes much longer to compute the timing estimates for
> start of symbol values when the total Rx window is much larger compared to
> how many symbols were actually transmitted, I was wondering if there was a
> way to detect an apparent increased received signal power or something like
> that so that I can somehow shorten my Rx window such that the algorithm can
> be just provided with a smaller number of samples. Any suggestions on how I
> can do this ? When I observe the abs() or real() plotted time domain
> digital data from my Rx window, should I be seeing a time duration within
> this window, where the amplitudes are higher than the rest of the window ?
> Because I don't see anything like that.
>
> Thanks and Regards,
> Sanat
>
--
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Message: 3
Date: Mon, 21 May 2012 13:06:25 +0100
From: Lu?s Correia <[email protected]>
To: [email protected]
Subject: [USRP-users] Getting separate IQ samples and work with them
in GRC
Message-ID:
<CAOt7J2E+D5pgusKHeM5nkfzO1mZNr0TYcswtNuAG=Z=ekgh...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hi all,
last week Marcus suggested me to do a simple grc flowgraph in GNURadio
Companion:
decimate(low_pass(I**2 + Q**2))
I've been trying to do that to detect a presence/absence of a signal (the
signal strength).
So far I've done something like this:
******************** ******
* Signal Source *---->*exp*--|
******************** ****** |
(cosine) | ******* *************
***********************
*------>*add*-------->* low
pass*-------->* gui scope / gui fft*
| *******
************* ************************
******************** ****** |
* Signal Source *--->*exp*--|
******************** ******
(sine)
But i'm getting a peak in every frequency that I tune the B100 to..
Can someone please have a look and correct my flowgraph?
Thnks in advance,
Luis
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Message: 4
Date: Mon, 21 May 2012 08:15:39 -0700
From: Nick Foster <[email protected]>
To: Farrukh Aziz <[email protected]>
Cc: USRP user forum <[email protected]>
Subject: Re: [USRP-users] Sych problem in 4*4 MIMO
Message-ID:
<CALALHJXChhUxCkckh6UR29nSHKRzbd8rTGZ63SjQFi8VGc=u...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
On Mon, May 21, 2012 at 1:17 AM, Farrukh Aziz <[email protected]> wrote:
> John,
> I had all the settings entered correctly as you have described (so there
> is no problem with my USRP settings). However the last thing that I did was
> to swap my master and slave nodes, and this solved the problem. I dont know
> why, but the issue is now solved and I am getting 4 complex, synchronized
> data streams.
> The system is working properly with the external references (clock and
> PPS) fed from signal generators, and it is also working with GPSDO
> references.
> Just wondering if MIMO cable is alike at its both ends.
> Thanks
>
Strange! The cable is identical and has no polarity. I'm guessing that it
may not have been fully inserted before, and when you swapped it you
plugged it in fully.
Glad it's working now.
--n
> *Farrukh Aziz Bhatti*
> Department of Electrical & Computer Engineering
> University of Auckland
>
>
>
>
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
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Message: 5
Date: Mon, 21 May 2012 17:20:27 +0200
From: Pol Henarejos <[email protected]>
To: [email protected]
Subject: [USRP-users] Building UHD using MSVC 2008
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
Dear list,
I am trying to build UHD driver using MSVC 2008, since it is my
compiler. I know that in Build Guide MSVC 2010 is required but I have
not it. I would like to request you if you could provide me support for
this compiler.
When I build UHD using MSVC 2008 everything goes fine. But when I start
some example or test the program closes suddenly with no useful error
(windows error 0xc0000005). I tried to run the program as Administrator
but no luck. Dependancy walker does not say anything anormal. All
libraries are x64. I use the release mode and the master branch (git
003.004.001-145-g38043612). I also do not provide usb support, only usrp2.
Do you have some hint?
Thank you.
Sincerely.
--
Pol Henarejos
Research Engineer, MSc
[email protected]
Centre Tecnol?gic de Telecomunicacions de Catalunya (CTTC)
Engineering Unit
Parc Mediterrani de la Tecnologia
Av. Carl Friedrich Gauss, 7
08860 Castelldefels, Barcelona (Spain)
Tel: +34 93 396 71 70 Ext: 2177
Fax. +34 93 645 29 01
www.cttc.es
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