Re: [Discuss-gnuradio] Agile Solutions is Pleased to announce USRP STAR. Yet another addition to GNURADIO

[Matt Ettus]

On 04/18/2011 10:13 AM, address@hidden wrote:
> We went through this published article you sent to us for review
> http://newport.eecs.uci.edu/~hyousefi/publ/sdrMC08.pdf
> 
> We didn't see anything particular to STBC/SFBC.

http://lmgtfy.com/?q=usrp+stbc+filetype%3Apdf

> For a beamformong
> system phase coherence is the fundamental requirement. By varying
> phase(weighting the antenna co-efficient) we can steer the beam. In
> USRP1/2/200/210 there is no guarantee of the phase reference every time
> you send the packets for transmitting or receiving. Every packet
> transmission they start with arbitrary phase.

That is fundamentally incorrect.  Every packet will NOT start with
arbitrary phase.  All of our systems have been used for beamforming.
All beamforming systems need calibration and the USRP is no different.
Here are some examples:

http://lmgtfy.com/?q=usrp+beamforming+filetype%3Apdf

> So every time the beam
> will be switching in arbitrarily. Particularly transmitter DAC doesn't
> have control over the phase plus deviation in the LO phase lock with
> track length of the common clock. And for for a phased array system,
> DOA(Direction of arrival) depends on the phase reference of the system.
> So every time the phase reference needs o be tracked in the algorithm to
> know actual DOA. For a diversity transmitter and diversity receiver
> employing MRC would only be realized with USRP1 system as per our
> understanding.

That is incorrect.  The USRP will maintain a constant phase relationship
between antennas for as long as you leave it running.

> We would like to know if USRP1 is capable of these things and how ?    

Yes.  I have answered the question of how to do this many times on this
mailing list over the years.

> Although we haven't come across any projects with USRP1 for successful
> testing for STBC and SFBC codes. 
> If any team or individual has published this work, we would be happy to
> check that part.

Steve answered that for you, and you can find a lot more at the link I
sent above.

> To verify from our end we took IQ samples for 2x2 Almouti scheme from
> Agilent-VSA example files. 
> We have then transmitted and received these IQ samples via
> USRP1+RFX2400. Transmission and reception done at 1MSPS with 4x
> interpolation.
> Received IQ samples when loaded into VSA for analysis, it failed to
> demodulate and decode. We have used Agilent VSA for years now and we
> consider it as a golden reference for demodulation and decoding. 
> 
> We respect your timely suggestions and advice.

Tom and I wrote Alamouti OFDM code and used it on USRPs in my office.
You can find some other people who did the same here:

http://lmgtfy.com/?q=alamouti+usrp+filetype%3Apdf

Matt Ettus