Dear Sir, thanks a lot for this great video, I have a question if you can help please: In UL out of Synch part at 17:30: - How can SN=X+1 reach the eNB MAC layer, but not reach the RLC layer ? - How did UE HARQ know that this sequence was not received ? It seems like I did not understand how the RLC & MAC layers work together at this point. Thanks for this great video Sir.
Hi, Good questions. As per my understanding. Actually for the first QUESTION, in the UL Direction the data passes through UE PDCP Layer to UE RLC Layer and then to UE MAC/PHY Layer until it is received and delivered to the gNB, the gNB will receive the data in the reverse direction which will be started from PHY/MAC Layer then RLC then PDCH. This means the first retransmission will be done in the MAC Layer (HARQ) after all the HARQ Trials are consumed then RLC Layer will retransmit X+1 again from scratch and it will pass through the same procedure For the 2nd question: In general, MAC uses HARQ, In which if an error is detected, the receiver(gNB) buffers the data and requests retransmission from the sender (UE). HARQ protocol relies upon the sender receiving ACK/NACK from the receiver It seems like I did not understand how the RLC & MAC layers work together at this point. For this part, I will try to simplify it, HARQ Start first and if the HARQ reaches the maximum retransmission attempt, then RLC will start retransmission for the packet from scratch, and every time the RLC retransmission starts, HARQ will take effect after. In all Cases, I will try to make a video to cover more details about the RLC & HARQ Processes
Very helpful Mohamed! I have 2 questions : a) Ue estimates PDCCH BLER-out/BLER-in based on SSB RSRP/SINR measurements, if for example Ue measures SSB RSRP for specific time below a threshold then it estimates that it cannot decode PDCCH and sends Qout. Is it correct ? b) Each RLC retransmission happens upon the expiration of RLC Polling Timer. Is it correct? Thank you
Thanks, georgi; For point a yes you are right but it also can be based on CSI RS. For point b; i believe i need to look into it in timers part 2, as i get to know that tpoll timer is not necessary to be triggered at every RLC retransmission; there is another factor which is called poll bit which gives control over this; i am still studying this part to explain it if possible in timers part 2
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Excellent explanation of RLC and MAC Retransmission procedure.
Thanks a lot for your feedback
Very nice and useful parameter to enhance packet loss and latency , great job 👏👏👏
Thank you 🙏
Great session, very simple but also too informative, thanks alot
Thanks, Mena, I am very glad you like it
Very nice video and just in time 😊, you excel in everything you do 😊😊
Thanks a lot, i an glad you like it
Dear Sir, thanks a lot for this great video, I have a question if you can help please:
In UL out of Synch part at 17:30:
- How can SN=X+1 reach the eNB MAC layer, but not reach the RLC layer ?
- How did UE HARQ know that this sequence was not received ?
It seems like I did not understand how the RLC & MAC layers work together at this point.
Thanks for this great video Sir.
Hi, Good questions. As per my understanding.
Actually for the first QUESTION, in the UL Direction the data passes through UE PDCP Layer to UE RLC Layer and then to UE MAC/PHY Layer until it is received and delivered to the gNB, the gNB will receive the data in the reverse direction which will be started from PHY/MAC Layer then RLC then PDCH. This means the first retransmission will be done in the MAC Layer (HARQ) after all the HARQ Trials are consumed then RLC Layer will retransmit X+1 again from scratch and it will pass through the same procedure
For the 2nd question:
In general, MAC uses HARQ, In which if an error is detected, the receiver(gNB) buffers the data and requests retransmission from the sender (UE). HARQ protocol relies upon the sender receiving ACK/NACK from the receiver
It seems like I did not understand how the RLC & MAC layers work together at this point.
For this part, I will try to simplify it, HARQ Start first and if the HARQ reaches the maximum retransmission attempt, then RLC will start retransmission for the packet from scratch, and every time the RLC retransmission starts, HARQ will take effect after.
In all Cases, I will try to make a video to cover more details about the RLC & HARQ Processes
Very nice ..one request one video to explain chain of signal processing in details..like layermapping-precoding-resouce mapping...step by step..thanks
Thanks; okay sure; i will do it
Very helpful Mohamed! I have 2 questions : a) Ue estimates PDCCH BLER-out/BLER-in based on SSB RSRP/SINR measurements, if for example Ue measures SSB RSRP for specific time below a threshold then it estimates that it cannot decode PDCCH and sends Qout. Is it correct ? b) Each RLC retransmission happens upon the expiration of RLC Polling Timer. Is it correct? Thank you
Thanks, georgi;
For point a yes you are right but it also can be based on CSI RS.
For point b; i believe i need to look into it in timers part 2, as i get to know that tpoll timer is not necessary to be triggered at every RLC retransmission; there is another factor which is called poll bit which gives control over this; i am still studying this part to explain it if possible in timers part 2
@@mohamedeladawiashour Thank you Mohamed for your prompt reply.Looking forward for timers part 2.
Good info 👍
Thank you