[srsran-users] Time Alignment Error and Timing Advance

[Alessio Scalingi]

Dear srsRAN community,
I am currently working on a project that involves channel estimation using DMRS in SrsRAN, and I have a couple of questions that I was hoping someone in the community could help me with.

First, I was wondering if anyone has experience with the Time Alignment Error (TAE) and why this value is important to calculate during the channel estimation procedure of the DMRS. I understand from the 3GPP standard that TAE refers to the misalignment of frames in the NR signals present at the BS transmitter antenna connectors, and I would appreciate any insights on how this affects the accuracy of the channel estimation.

Specifically, in the srsRAN code, the calculation of this TAE is computed in the chest_ul.c located in this path:   lib/src/phy/ch_estimation/  (line of code 308).
Secondly, I am curious to know if the concept of Time Alignment Error is different from the Timing Advance, which corresponds to the length of time a signal takes to reach the BS from UE. Is there any relationship between these two concepts that I should be aware of? 

And lastly, at a high level, in the ue.conf file: set the rf.time_adv_nsample = 100 , means that the UE is transmitting BEFORE the allocated time-slot to compensate the propagation delay, is this correct??
Any information or suggestions on these topics would be greatly appreciated. Thank you for your time and expertise.

Best regards,
Alessio Scalingi                                                               
Ph.D. Student
IMDEA Networks Institute

E-mail: alessio.scalingi at imdea.org
Phone: +34  623 067 475‬
Address: Av. Del Mar Mediterraneo, 22, 28918, Leganés, Madrid, Spain

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