UUU and DDD communicating with N210 @ 10 Msymbol/s

Dear friends,

I am getting some “UUU” at the beginning of a transmission stream and a
lot of “DDDD” during the simultaneous reception stream.

I am sending and simultaneously receiving a BPSK stream at 10 MSample/s
on USRP N210.

I checked that I have the string @my_user_group - rtprio 99 in
/etc/security/limits.conf and that I am running as a user in

I also checked the status of eth0, when connected to the powered USRP
N210. Here the output of ethtool eth0

Settings for eth0:
Supported ports: [ TP MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Advertised pause frame use: Symmetric Receive-only
Advertised auto-negotiation: Yes
Link partner advertised link modes: 1000baseT/Half 1000baseT/Full
Link partner advertised pause frame use: Transmit-only
Link partner advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: MII
Transceiver: internal
Auto-negotiation: on
Cannot get wake-on-lan settings: Operation not permitted
Current message level: 0x00000033 (51)
drv probe ifdown ifup
Cannot get link status: Operation not permitted

If I issue ethtool -a eth0 I get the reply: “Pause parameters for eth0:
Cannot get device pause settings: Operation not supported”

If I analyze the received data I don’t see any troubles due to the
“DDDDDD”, while I can recognize some artifacts due to the few “UUU” at
the beginning of the transmission.

If I reduce the sample rate I am able to have the “DDDDD” disappeared,
but the “UU” are still present.

Can someone help me in understanding what I have to do to solve my

Best regards

Piero, I0KPT

Here, attached, an example of a very basic system that produces a “U”
any time I run it on my N210 USRP. Please note that the sample_rate it
isn’t so high.

The presence of a “U” is it normal or not?

Thank you in advance.

Piero, I0KPT

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