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Thanks for the nice explanation ... when you get time can you kindly also elaborate about the parallel HARQ processes in MAC layer and how this is used for continuous transmission on teh air interface ?
Thanks for your clear explanation! I want to ask for some applications (such as 5G MBS PTM), RAN1 has decided to add the feature of HARQ in PHY layer. However, PTM only supports UM at RLC layer. Under this scenario, can we state that the gNB will know the reception status of each UE?
The example in this session is for RLC AM mode which is used for most of the data type sessions. For RLC UM mode, the HARQ retransmissions is the only medium since there will be no RLC retransmissions. So, if all HARQ retransmissions fail then the packet is lost. However, the usual approach for such scenarios is to make the HARQ very robust by increasing the number of retransmission count for HARQ and also by decreasing the modulation to improve the link budget.
Thanks for the nice video. I subscribed to your channel for such videos. Can you please confirm if the understanding is correct 1) RLC nack will come into picture after max harq retransmissions? 2) So if the UE is in poor radio condition or high bler, then rlc nack will occur? 3) RLC nack can cause an increase of RLC delay. 4) What can be the other causes of RLC delay? can it be due to rlc buffer size full? Can you make a video related to RLC buffer size and its consequences?
Correct. Max HARQ Retx should result in a NACK for RLC. So, higher BLER will result in more RLC NACKs which should increase the RLC buffer delay. Usually bad radio conditions or congestion can increase the RLC buffer and thus, increase the RLC delay.
@@OurTechPlanet can you explain more about rlc congestion? I mean if any videos? By congestion, my understanding is excessive buffering of packets, i.e. A timestamp is added to every ingressed packet and time delay is when the packet is egressed after certain time delay.
However, the eNB or gNB can reduce MCS to make the service more robust. This is done after HARQ ReTx (4 times) are exhausted so can it be said that it will happen (if it does happen) with RLC ReTx?
It can happen after first NACK? Then this new MCS lowered packet should be re-sent by RLC? But then this should happen after harqs have expired and there's an RLC re-transmission?
For 5G topics discussed in 5G Job Interviews, check out the complete playlist below :)
🌐5G Interview Topics
💡ua-cam.com/play/PL4OXTttOk9WiLsz4fR62lpPcT3Wx3l5OP.html
Your explanation is more useful...
Thanks for your contribution.
Glad to hear that. Thanks :)
Great Job !
Thanks
Thanks for the nice explanation ... when you get time can you kindly also elaborate about the parallel HARQ processes in MAC layer and how this is used for continuous transmission on teh air interface ?
Sure, will work on that too!
Thanks for making learning simple...Please share a vedio on 5G CA
Thanks, sure, will address CA topic soon as well!
Thanks for your clear explanation! I want to ask for some applications (such as 5G MBS PTM), RAN1 has decided to add the feature of HARQ in PHY layer. However, PTM only supports UM at RLC layer. Under this scenario, can we state that the gNB will know the reception status of each UE?
The example in this session is for RLC AM mode which is used for most of the data type sessions. For RLC UM mode, the HARQ retransmissions is the only medium since there will be no RLC retransmissions. So, if all HARQ retransmissions fail then the packet is lost. However, the usual approach for such scenarios is to make the HARQ very robust by increasing the number of retransmission count for HARQ and also by decreasing the modulation to improve the link budget.
Thanks loved it understood thanks
Great to hear that!
Thanks for clear points about harq.
could you please explain more about harq process in ul/dl as 5g uses asynchronous harq in both ways.
Sure, let me add that to my list. Thanks :)
Thanks for the nice video. I subscribed to your channel for such videos.
Can you please confirm if the understanding is correct
1) RLC nack will come into picture after max harq retransmissions?
2) So if the UE is in poor radio condition or high bler, then rlc nack will occur?
3) RLC nack can cause an increase of RLC delay.
4) What can be the other causes of RLC delay? can it be due to rlc buffer size full?
Can you make a video related to RLC buffer size and its consequences?
Correct. Max HARQ Retx should result in a NACK for RLC. So, higher BLER will result in more RLC NACKs which should increase the RLC buffer delay. Usually bad radio conditions or congestion can increase the RLC buffer and thus, increase the RLC delay.
@@OurTechPlanet can you explain more about rlc congestion? I mean if any videos? By congestion, my understanding is excessive buffering of packets, i.e. A timestamp is added to every ingressed packet and time delay is when the packet is egressed after certain time delay.
@@bijitdeb2010 Ok , will add it to my To-Do list :)
Thank 😊 🙏
Every set of 4 HARQ retransmissions is considered as HARQ process with specific id. Is it correct ? Thank you
Yes, the HARQ retransmissions use the same HARQ ID
Thanks for the video
So means these 5 Harq retransmission is nothing but CRC Failure?
Yes, actually a HARQ retransmission usually happens due to a CRC failure
@@OurTechPlanet thanks
@@irfanetrx1 You are welcome :)
Could you please make a learning session on NR RNTI
Sure, let me add that to my list!
thank you sir
Most welcome
However, the eNB or gNB can reduce MCS to make the service more robust.
This is done after HARQ ReTx (4 times) are exhausted so can it be said that it will happen (if it does happen) with RLC ReTx?
No, it can actually happen after first NACK or a couple of retransmissions as well. It is open to implementation.
It can happen after first NACK? Then this new MCS lowered packet should be re-sent by RLC? But then this should happen after harqs have expired and there's an RLC re-transmission?
@@filthykid84 Any MCS reduction is a MAC layer concept. RLC does not interact with that.
Hence we cant change MCS during HARQ process and CRC bits of RedundancyVersion didnt help, we got RLC to retry with lower set of MCS. Good one mister
Thanks
We can change the MCS for a HARQ retransmission, no?
Maximum HARQ used in 5G?
Max number of HARQ processes in 5G are 16
What is offset to carrier and offset to point A in ssb
Please make a short video with images
Sure, let me work on creating one for this topic too
Offset to carrier defines start of the BWP and offsettopointA defines offset between pointA and SSB start position or kssb
Sir plz pdf dijiye❤
Unfortunately, at the moment, we are not sharing the content in this format :)