5G Call Flows (Session 1): How a 5G UE performs Initial Access
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- Опубліковано 6 лют 2025
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5G Call Flows (Session 1): How a 5G UE/Mobile performs Initial Access
One of the most complex area for beginners is to understand 5G Call Flows and Signaling procedures. 3GPP defines them but they are not easy to understand. So, in this video, I have explained the 5G Call Flows (NSA) in a simplified manner and I have also included the contents of some of the important messages to show what actually goes on between UE/Mobile and the 5G network during the 5G Initial Access or Network Entry procedure! Moreover, I have highlighted some of the important 5G KPIs in the end that will help the audience to correlate the 5G Call Flow & Signaling procedure with the 5G KPI itself. This is also one of a popular 5G Interview topic as well and many questions are asked from this Signaling Procedure.
You can also visit us on our blog site - ourtechplanet.... in order to read our articles in detail and know more about who we are and what we do.
0:00 Start
0:50 5G Network Access Overview
3:13 5G Access Call Flow
3:57 5G B1 Threshold
6:45 5G Measurement Report
7:45 SgNB Addition Setup
8:57 How UE Gets The 5G gNB Configuration Info?
12:00 5G RACH Procedure
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For simplified 5G tutorial sessions, check out the complete playlist below :)
🌐5G Call Flows & KPIs
💡ua-cam.com/play/PL4OXTttOk9WhvApKwJBcZx0G4a2m8N-z6.html
Much appreciated... Tu ce greato quoted from 3 idiots movie hh
Great job brothers. Good luck
Great video explaination ❤
Glad you liked it!
@@OurTechPlanet helllo techie how to config or enable in mobile devices....
The way you explain in your videos, it makes very easy for me to understand. Thank you for your contribution. Stay blessed
Glad to hear that. Thanks a lot :)
Excellent explanation, frame structure also I got understand from your vedio, possibly these are most easiest and shortest to understand the basic of 5G, amongst the utube 🌎.
Thanks Avijeet, this is great to hear!
Brilliant as usual..! Excellent videos on 5G call flow sessions, very easy to understand. Thanks for posting, Ali.
Thanks a lot and I am really grateful to everyone for such an overwhelming response!
FINALLY I UNDERSTAND SHORT EASY AND SWEET CALL FLOW. Thank you!
Thanks. That is good to hear :)
easiest explanation i have ever seen. thank you so much. Please consolidate a complete & detailed video on call flow of 4G as well as 5G.
Sure I will do that as well :)
@@OurTechPlanet it is still awaited
Very well explained! Thanks a lot for explaining with reference to UE logs.
You are welcome!
5g UE is explained really well. I have learned something new today.
Wonderful explanation and you have narrated the call flow very well.
Keep posting, your videos are easy to understand :)
Thanks , this is great to hear :)
This is the best explanation of 5G access call flow. Well done!
Wow, thanks! Really appreciate the feedback!
@@OurTechPlanet Thanks! I’m also interested in DL/UL 5G data scheduling and resources allocation, which explains K0, K1, K2, SLIV and etc. Do you have any training on this topic?
@@AlirezaAlizadeh4 Not yet but these topics are in pipeline :)
@@OurTechPlanet Fantastic! Looking forward to watch it.
That was super cool.
Best part was the UE logs inclusion, that made the things real.
Thanks a lot :)
The best tutorial and explanation. You are the best
That is so nice of you. Really glad to help. Do help us spread the word :)
Excellnt Work...............Can you make video on details 5G KPIs, Counter , solution and with patameters to be implement
Thanks Varun, sure, I will cover these topics soon!
Very well explained especially with IE snippets! Keep positing more videos and this will definitely help everyone to understand the concepts and baisc of 5G !
Thank you! Will do!
It is crisp explanation. i've one doubt: -156dbm which spec is reference? please explain in detail ho to calculate RSRP and rSRQ w.r.t gNB. thank you.
For reference, you can refer to 3GPP 38133. There is a "Table 10.1.6.1-1: SS-RSRP and CSI-RSRP measurement report mapping" that shows conversion and also the lowest value of -156. Also, under 10.1.11.1, you should be able to see RSRQ as well.
Thanks for the explanation..
Please conduct a video for ENDC Setup failure Optimization
Sure, will add that soon!
Hi, Thanks for your videos Bro, In my NSA layer signaling 8:26 I have two messages ERRC and NR-RRC. Two rrc reconfiguration processes happens before NR RACH attempt, preamble, response. I use TEMS.
Thanks very good explaining!! during lectures you had shared UE log.. which tool was used to captured log..
I shared the details about the tool in the following session
ua-cam.com/video/sXgdmudCZzk/v-deo.html
Beautiful and easy explanation over NSA 5G Call flow..
Glad it was helpful! :)
Thank you so much for making it so simple. Do we have any video for SA call flow yet? Thanks again!
yes here it is
ua-cam.com/video/2YN95HMxeb0/v-deo.html
Nice presentation. NSA and SA cover signaling massage!
Thanks Sushil :)
Your videos was very well explained.
I am watching your videos.
If you don't mind can I get this PPT ?
Thanks Mana. Unfortunately, we do not share the slide packs, thanks for understanding.
Excellent it is best video for 5G Access, thank you very much.....
You are most welcome
Nice video, very well explained. Thank you for creating such videos
You are most welcome
very nice explanation..... log file explanation is really helpful
Thanks for the feedback :)
Easy to understand explanation, thanks.
One quick question, what are the contents of NR RACH MSG-3 in this scenario ? From the ue perspective I don't think there is anything at RRC level to send out to the NR Cell after MSG2, please do let me know.
yes, in NSA , there is no RRC so MSG3 is just a PUSCH allocation
Could you please explain rach process, SA/NSA call flow as well in details. Like what exactly goes inside message.
Sure, will do it in near future
many tech students can benefit from this video
Glad to learn that it helps :)
Excellent way of explaning!
please, why has SCG split been more preferred by industry vs. MCG split?
Thanks. I think it was a more natural transition from 4G to 5G SA and a seamless co-existence of NSA and SA. Also, to take traffic away from the already congested LTE and move to higher capacity 5G with better user experience, the SCG split seems to be the better choice.
Thanks a lot for the detailed explanation.
You are welcome :)
Mind blowing. Keep up the good work.
Thank you so much 😀
Perfect videos. can you please explain a little about PRB and digitally beam forming and beam and null steering??. very much appreciated.
Yes, I plan to create a session on this topic soon
Great work gents. Good luck
Much appreciated!
Thank, one question here please, RRC Re-config messages containing 5G NSA cells info, is it sent to all devices or only 5G capable devices ?
Only to the particular 5G Device
Very very helpful 👍 thanks 👍😊
Most welcome 😊
I suppose this is contention free RACH procedure
?
This can depend on vendor implementation!
You gave an excellent explanation on the 5G. It is nice to learn something on 5G, since soon or late we are all going to use the system. Thanks for sharing your knowledge.
Really happy to hear that and glad to add value :)
Is this 5g Setup attempt / Success & Endc setup SR same ?
Yes 5G Setup is similar to ENDC Setup in case of NSA networks.
Well explained. Thanks for sharing 👍
Glad it was helpful!
may we understand, why there are two times for ueCapabilityEnquiry ?
The 5G brings along lots of band combinations which increases UE capability message size. The 2 step enquiry is thus a way to reduce the size as it can be split into two messages.
one suggestion some time in voice disturbance occurs.....may be some optimization required for it haha....
Lol, yeah I bought a new Mic so it should be better in the new videos now :)
Thanks, very nicely explained. the idea of showing the UE logs made things much interesting! What is the periodicity the 5G UE is asked to do B1 measurements? Is that included in the RRC config messages too?
Thanks Haider. Yeah, reportAmount and reportInterval are sent to the UE in RRC measurement control message.
@@OurTechPlanet Thanks , what is a typical interval in ms?
Thank you and very well explained
Thanks, Nandeesh.
Very well explained. Thanks
Thanks!
In this case what is msg-3 exactly?
Is it RRC message?
In 5G NSA, the msg3 is just a PUSCH allocation. Not a RRC message.
Very helpful! I would like to mention that although msg3 (Rrc connection setup request) between Ue and gnb (after endc setup) is considered RRc message, it is sent by the Ue directly to gNB and not via eNB.Do you agree with this?
Yes, correct, the MSG3 for NR RACH is sent by UE directly to gNB.
can you please share Powerpoint for the same
I generally do not share PPTs :)
Can you add NSA DC - 5G CA flow in similar way .. thanks
Sure, will add this topic in the To-Do list!
Excellent explanation sir.. thank you. I need guidance for future job opportunities and hike in this technology. Will you please help me??
Stay connected on linkedin, I think that is the best place to land good opportunities :)
Thanks for best explanation...
Thanks and welcome.
Excellent video.Good explanation
Thanks!!!
Wonderful Explanation Sir
Thanks Sir
Thanks Suraj
Excellent
Thanks Sarfraz!
Excellent explanation
Glad it was helpful!
easy as it comes. Great
Thanks :)
NR RACH MSG 3 refers to RRC Setup Request right?
This is NR NSA so it does not have RRC on NR in NSA mode. Thus, the MSG-3 is just a PUSCH transmission and not an RRC signaling
@@OurTechPlanet but in SA mode this would have been RRC Request attempt?
@@munzirkhalil4213 Yeah in SA, it would be a RRC Request.
Well explained.
Thanks
Perfect, thanks a lot.
You are welcome!
Really nice job, so what is the order recomended to watch all the videos in 5G workshop lectures list.? For beginers.
I have made some playlists that might be helpful here.
To begin with, you can watch the following playlist which covers the 5G overview
ua-cam.com/play/PL4OXTttOk9WjWV1HDB9q_L20rByAx8Xgt.html
After this, the more detailed topics are in the following playlist
ua-cam.com/play/PL4OXTttOk9WiLsz4fR62lpPcT3Wx3l5OP.html
Hi, Thanks for sharing knowledge with all of us. Can you also please post some good video on URLCC specially MiniSolt understanding and how to implement minislot concept in my 5G Stack. Thanks for the help in advance.
Sure, will work on it!
Very good explanation, keep it up 👏
Thanks a lot 😊
Thanks! Since the message "RRC Reconfig (NR Bearer)" carries all the configuration of the gNB, is there still a need for the UE to decode MIB, SIB1, and SI-messages of the gNB?
In case of NSA, since RRC message contains all system information, so SIBs are not necessary for NSA.
Thanks for the reply.
What happens if the RACH procedure fails?
1. Will the UE loose 5G connection?
2. Is data transmission to the UE started after sgNB addition success or RACH success?
3. Which KPIs will be impacted if there’s a RACH failure? only RACH SSR or sgNB drop inclusive?
4. If there is sgNB failure after RACH failure, will it be counted as a service drop?
TIA
In NSA, a RACH failure will result in 5G call drop so yes the UE will lose 5G connection.
The data transmission starts after the RACH success
Both RACH Success Rate and SgNB Drop including RACH failures will be impacted
SgNB Addition happens before RACH. SgNB failure after RACH is basically an abnormal release. Have a look at this video, it should explain most of your doubts
ua-cam.com/video/BYa7r_-awZE/v-deo.html
One Question , if UE doesn't support 5G BW ( suppose BW is 100 MHZ while UE supports only 60MHZ) , what will happen?
Then it will not get 5G
Perfectly clear! You made it so easy to understand. Thank you!
That is great to hear. Thanks!
Do you have 5G call flow etc on Udemy?
No, currently the main source of our content is on UA-cam. I am considering Udemy - let me explore this option :)
@@OurTechPlanet thank you for the knowledgeable content.
Nice explanation
Thank you :)
Good explanation....
Thanks Wasim
thanks for knowing us how 5g work
You are welcome mate.
Thank you :)
You are welcome!
after RACH nothing required more in call setup to make data session? or remaining part is coming?
Yeah, in case of NSA, RACH completion indicates that data can now flow on NR leg. So, in short, no further signaling is required over the air interface after RACH is successful.
Great work!
Thanks!
Thank you Sir.
You are welcome!
Offset means... Please give clear explanation
Can you elaborate a bit . . . which offset are you referring to? frequency offset in RRC Recfg?
@@OurTechPlanet Asking mean generally...
@@m.karthikeyan6482 Generally, when referring to frequency, the offset can indicate the difference from the start of the frequency. In case of mobility, offset can mean the cell individual offset or A3 offset etc.
@@OurTechPlanet Great thanku ❤️❤️❤️❤️❤️❤️❤️❤️❤️❤️
Excellent...
Thanks :)
Hi Ali , Excellent one . For any reason if the NSA UE is not sending back the B1 measurement report back to 4G node on Time . How long it will wait to measure the NR again . ( i am assuming that the likely case is Radio connection lost , UE connects to LTE again ,RRC reconfiguration to the UE from eNB and the gNB addition follows with B1 measurement report from UE RRC . If we exclude this scenario is there any periodic timer NSA UE will follow )
No, as long as measurement control is active, the UE should measure but there are parameters like reportInterval and reportAmount that eNB sends to the UE in RRC Recfg
i am ec student ..thanks
you are very talented
Thank you, Julia :)
i have like it to much
Glad to hear that! :)
Thank you
Welcome!
Nice explanation.. in my network i am facing one problem....we have 2 5g bands 3.5 100mhz and 2.6 80 mhz... for example we have 2 neighbouring sites lets say site A(lte + 3.5 5g) and site B(lte and 2.6 5g) and ue is near site B and from site B lte when its start adding 5g many times its added site A 5g with bad coverage logically it should add site a 5g but he cant even on site A i define B1 threshold for 2.6 is 46(-110) and for 3.5 b1 threshold 56(-100) but still its adding 3.5 any suggestion to reduce that my aim it should add collocated 5g ..i am having nokia equipment even we have one priorty parameter ..even i gave high priorty to 2.6 but still its adding 3.5 5g band
Maybe the UE supports 3.5G band combination only?
@@OurTechPlanet it support both band
Great video !!!
Thanks, Youssef.
Amazing thanks for sharing
You are welcome!
excellent
Thanks!
Nice 👍
Thanks :)
Sir r15 kiya hai
3GPP Release 15
I Like It
Thanks
Great
Thanks
useful video for me
Glad to have helped mate :)
❤️❤️❤️❤️❤️
Thanks
👍
Thanks
You r a superstar Muhammad Ali Khalid
Thanks :)
"5G NR B1 threshold"? I tought 38.331 spec call it "xQrLvl" which is equivalent to SSB RSRP level in dB.
Maybe this B1 for NSA only. All this legacy approach is a nightmare of ProtocoloStack engineers, and headache for investors that need to keep army of PS.
Yes, B1 threshold is used for NSA
🙏🙏🙏🙏🙏🙏💗
Thanks
We need to make clear that this call flow is NSA.
Yes. Correct, it is NSA
Very well explained. Thanks
You are welcome!
Very good explanation.
Glad it was helpful!
Excellent
Thanks