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Re: [Discuss-gnuradio] How to implement MIMO transmissions


From: Josh Blum
Subject: Re: [Discuss-gnuradio] How to implement MIMO transmissions
Date: Wed, 13 Feb 2013 00:07:14 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130106 Thunderbird/17.0.2


On 02/12/2013 01:38 PM, Lara Deek wrote:
> Thank you Josh for your reply!
> 
>> Well in gnuradio, you dont have access to the send function.
> 
> I created a usrp sink using uhd_make_usrp_sink(), and using the pointer to
> the multi_usrp that is returned from calling get_device() on the usrp sink
> variable, I access send() (ofcourse including the necessary uhd libraries).
> In fact, the method I use to access the send() function is the same as that
> used in the gr_uhd_usrp_sink.cc work() and start() functions.
> 
>> The 
>> scheduler will deliver two streams of equal length (from 2 ports). 
> 
> I use the uhd send() function to transmit data, as shown in
> rx_multi_samples.cpp for the receiver, and I actually referred to
> tx_bursts.cpp to implement the transmitter. Then I guess to control the data
> [source] in the streams, I would have to transmit samples from a .dat file
> (as done in tx_samples_from_file.cpp) using an ifstream, correct? Can I
> avoid the gnuradio usrp_sink scheduler by doing this?

Of course, you can use the same API (UHD) that the gr-uhd component. So,
you dont really need to make a usrp sink block, but, this method works
too :-)

> 
> I also want to control when to use MIMO vs SISO, sometimes I only want to
> use a single antenna/transmitter. I can't find a method to specify which
> usrp/channel to use in send(). Is there a way to transmit on a single
> antenna/channel in a MIMO setting? There's set_antenna() in gr-uhd
> (set_tx_antenna() in UHD multi_usrp.hpp), can it be used to implement this?
> 

It depends how quick you need to be able to reconfigure. You could

1) send out zeros to one of the channels when in single output (quick)
2) tear down the device object and make a new one for one channel (not
quick)
3) tear down the streamer, and create a one channel one (not quick)
4) make two streamers, and feed them both TX data for MIMO, and just one
for SISO

-josh


> Thanks again,
> Lara
> 
> 
> 
> --
> View this message in context: 
> http://gnuradio.4.n7.nabble.com/How-to-implement-MIMO-transmissions-tp39546p39574.html
> Sent from the GnuRadio mailing list archive at Nabble.com.
> 
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