[USRP-users] MIMO bug?

Marcus D. Leech mleech at ripnet.com
Mon Dec 29 16:05:17 EST 2014


On 12/29/2014 12:09 PM, Dan Sego via USRP-users wrote:
> Good morning to the list.
>
> I have 2 N200 r4 units with WBX daughter cards operating with the 
> following Win32; Microsoft Visual C++ version 10.0; Boost_105400; 
> UHD_003.008.000-release. One unit has an internal GPSDO.
>
> In MIMO operation (via the MIMO cable). The slave unit experiences an 
> unexplained 25 dB of attenuation relative to the master. This change 
> does not follow the hardware: that is it tracks the slave.
>
> I am using US HDTV as probing signal: tuning to 575 MHz with fc32 
> formatted data sampled as 12.5 MCSPS per unit. The code operated 
> successfully performing data capture to file (though does have the 
> windows prompt upon completion to terminate). An example run screen 
> capture is pasted below: the collection operation involves continuous 
> sampling saving contiguous packets (28) and skipping 50 for a 
> approximate burst sampling rate of 25 Hz.
>
> Win32; Microsoft Visual C++ version 10.0; Boost_105400; 
> UHD_003.008.000-release
>
> -- Opening a USRP2/N-Series device...
> -- Current recv frame size: 1472 bytes
> -- Current send frame size: 1472 bytes
> -- Creating WSA UDP transport for 192.168.10.3:49156 
> <http://192.168.10.3:49156>
> -- Creating WSA UDP transport for 192.168.10.3:49158 
> <http://192.168.10.3:49158>
> -- Creating WSA UDP transport for 192.168.10.3:49157 
> <http://192.168.10.3:49157>
> -- Creating WSA UDP transport for 192.168.10.3:49159 
> <http://192.168.10.3:49159>
> -- Detecting internal GPSDO.... Found an internal GPSDO
> -- Creating WSA UDP transport for 192.168.10.2:49156 
> <http://192.168.10.2:49156>
> -- Creating WSA UDP transport for 192.168.10.2:49158 
> <http://192.168.10.2:49158>
> -- Creating WSA UDP transport for 192.168.10.2:49157 
> <http://192.168.10.2:49157>
> -- Creating WSA UDP transport for 192.168.10.2:49159 
> <http://192.168.10.2:49159>
> -- Setting references to the internal GPSDO
> -- Initializing time to the internal GPSDO
> Using Devices: Multi USRP:
>   Device: USRP2 / N-Series Device
>   Mboard 0: N200r4
>   Mboard 1: N200r4
>   RX Channel: 0
>     RX DSP: 0
>     RX Dboard: A
>     RX Subdev: WBXv3 RX+GDB
>   RX Channel: 1
>     RX DSP: 0
>     RX Dboard: A
>     RX Subdev: WBXv3 RX+GDB
>   TX Channel: 0
>     TX DSP: 0
>     TX Dboard: A
>     TX Subdev: WBXv3 TX+GDB
>   TX Channel: 1
>     TX DSP: 0
>     TX Dboard: A
>     TX Subdev: WBXv3 TX+GDB
>
> Actual RX Rate Master: 12.500000 Msps...
>
> Actual RX Rate Slave: 12.500000 Msps...
>
> Actual Gain Master: 10.000000 dB...
>
> Actual Gain Slave: 10.000000 dB...
>
> GPS lock status: locked
> GPS epoch time: 1419183071 seconds
> -- Successfully tuned to 575.000000 MHz
> -- 
> -- Successfully tuned to 575.000000 MHz
> -- 
> Checking LO Lock Master LO: locked...
> Checking LO Lock Slave LO: locked...
> Checking MIMO Lock MIMO: locked...
>
> sample time first packet2.3000003
>
> full seconds2.3000003
>
>
> sample time first packet2.34068534
>
> full seconds2.34068534
>
>
> Done!
>
> I have measured the channel signals of the units individually 
> and configured for MIMO. Examples of the individual measurements 
> (power spectra and mean noise power and total signal power are 
> summarized in slide 1 attached. All runs were made at 10 dB of gain. 
> Both units were individually exercised from 0 to 30 dB of gain to have 
> side-by-side responses (indeed one unit is 5 dB less sensitive which 
> track over gain and both have distinctive and repeatable gain 
> responses using identical log periodic antennas and matched length coax).
>
> Slide 2 has the MIMO results in both possible configurations.
>
> Has anyone encountered this? Any suggestions?
>  regards, Dan Sego
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
The only thing I can think of is that the slave gain isn't being set, 
despite the messages shown to the contrary.

Have you tried a GR flow-graph to experiment with this case?



-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

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