On 07/21/2020 12:13 PM, Prasad via USRP-users wrote:
Soft reminder!
Thanks,
*From:*Prasad [mailto:kp...@trilcomm.com]
*Sent:* Monday, July 20, 2020 7:58 PM
*To:* 'usrp-users@lists.ettus.com'
*Cc:* 'Rao Yenamandra'
*Subject:* 1 Ts delay in USRP B210
Dear Team.
Hope you are doing well and safe.
We are bringing up our NR-5G UE stack with USRP B210.
If time permits, would you pls. reply to below concern with your
valuable information.
During the synchronization procedure, we observe atleast 1 (Sampling
Time) drift in rx streamer in every ~40ms time period.
Are we missing any time_spec during /uhd_rx_streamer_recv/ api or in
/uhd_tx_streamer_send/ ?
Master clock rate: 30.72e6
Sampling rate: 30.72e6
Carrier frequency: 3.8e9
We use one B210 to transmit time domain samples back to back and
others to receive.
Log snippet:
Init PSS detected with lag: /4469/ (/PSS detection offset from the
slot boundary/ )
sss has been detected
Init PSS detected with lag: 4469
sss has been detected
Init PSS detected with lag: 4469
sss has been detected
Init PSS detected with lag: 4469
sss has been detected
Init PSS detected with lag: 4470 à1 Ts drift
sss has been detected
Init PSS detected with lag: 4470
sss has been detected
Init PSS detected with lag: 4470
sss has been detected
Init PSS detected with lag: 4471 à1 Ts drift.
sss has been detected
Init PSS detected with lag: 4472à1 Ts drift
sss has been detected
Init PSS detected with lag: 4472
sss has been detected
Init PSS detected with lag: 4472
sss has been detected
Init PSS detected with lag: 4484 à12 Ts drift
sss has been detected
Thanks! in advance.
Regards,
Prasad.
Are you just using the on-board reference clock, or using something like
a GPS module?
The drift you show is roughly 0.8PPM (if I've done my math correctly),
which is well within spec for this board without a better reference clock.
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