# Usrp b210 and mimo

**URL:** <https://www.ruby-forum.com/t/usrp-b210-and-mimo/233342>\
**Category:** GNU Radio\
**Created:** [December 5, 2014, 2:51pm UTC](https://www.ruby-forum.com/t/usrp-b210-and-mimo/233342 "2014-12-05T14:51:48Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [December 5, 2014, 2:51pm UTC](https://www.ruby-forum.com/t/usrp-b210-and-mimo/233342/1 "2014-12-05T14:51:48Z")

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I’ve slowly gathered the courage to try out the B210 devices. I was  
impressed by the fact that I could get 50 MHz of bandwidth out of it.  
However, I immediately ran into problems with absolute timing.

I’ve been using the B210 for mimo with USRP N200 devices for testing.  
The  
N200 devices all nicely synchronize themselves to the external PPS and  
after multiple restarts, their timing will be accurate. However, the  
starting time of the B210 seems to have a random component with a  
standard  
deviation of about 100 microseconds. Every time I restart sampling, the  
offset between the N200 and the B210 is slightly different. There is no  
change in the timing offset between the N200 devices.

Is this a known issue, or am I doing something wrong?

This is how I configure the devices:

u.set\_clock\_source(“external”)  
u.set\_time\_source(“external”)  
tt = time.time()  
while tt-math.floor(tt) \< 0.2 or tt-math.floor(tt) \> 0.3:  
tt = time.time()  
time.sleep(0.01)  
print("Latching at "+str(tt))  
u.set\_time\_unknown\_pps(uhd.time\_spec(math.ceil(tt)+1.0))  
time.sleep(1)  
u.set\_start\_time(uhd.time\_spec( starttime ) )

juha

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**Author:** ![Juha\_V](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/4af34b/32.png) [@Juha\_V](https://www.ruby-forum.com/u/Juha_V)\
**Post date:** [December 11, 2014, 2:27am UTC](https://www.ruby-forum.com/t/usrp-b210-and-mimo/233342/2 "2014-12-11T02:27:03Z")

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I appreciate this a lot. I’ll owe you guys beers the next time I see  
you.  
I’ll be in SF next week at AGU if you guys want to meet up.

I’m itching to start using the b210 with our incoherent scatter radar.  
It  
has more bandwidth and the tuner copes with the high dynamic range RFI  
environment better than our existing receiver.

Our application requires continuous streaming, so I do hope that you  
figure  
out how to get this working too.

juha

On Wed, Dec 10, 2014 at 7:47 AM, Balint S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)