Introduction to RACH Procedure in 5G

This video explains how a UE establishes its initial connection using RACH procedure in 5G.
▬ Contents of this video ▬▬▬▬▬▬▬▬▬▬
0:00 - Introduction
0:39 -SSB Burst
2:21 - RACH Transmission (Message 1)
2:41 - Zadoff Chu Sequences
5:05 - Timing Advance Command (Message 2)
5:26 - RRC Connection Request (Message 3)
5:40 - Contention Resolution (Message 4)
7:53 - Contention Free RACH procedure
Correction: 6:18 - UE sends ue-identiy in "RR Connection Request" (Msg3), not TC-RNTI. ue-identiy is typically a random number, hence it will be different for UE 1 and UE 2. Base Station selects one of the ue-identity and sends it over "Contention Resolution" (Msg4). UE matches received ue-identity with its own ue-identity to check if its RACH attempt is a Success or Failure.
References:
1. ETSI TS 138 211
2. ETSI TS 138 321
3. Textbook “5G New Radio in Bullets” by Chris Johnson
4. ShareTechNote: www.sharetechnote.com/html/5G...
5. TechPlayOn: www.techplayon.com/5g-nr-rach...
Music: Erik SATIE - Gymnopedies 1
#5G, #RACH, #Wireless, #WirelessCommunication, #CellularCommunication

[@amitsardanayt]

Very clear video with minimum time wastage. Loved it

[@joeytsai5259]

Very very clear, thanks a lot！

[@chaitug86able]

Highly impressed with the content and the presentation. Looking forward to see more videos

[@WirelessExplained]

Thank you! Will do!

[@yasinmiar3316]

Very well explained

[@ayushibhatt9518]

Thanks for such a brief video. Can you also make a separate video based on Zadoff Chu sequence, that would be incredibly helpful.

[@kevinyuan6685]

Excellent video.

[@kirankumaryakkala]

Appreciate your presentation. The topic is neatly explained in a simplest way. I saw very few videos. Could you please cover more topics. Thanks

[@rakshitverma5016]

excellent video

[@Umer_Aftab]

Great

[@user-lu5wh1sw1i]

Very nice❤❤ thank you

[@user-ov2iz5zt1g]

Excellent. It would be great to do the same for 4G.
Thank you

[@shan35178]

TC-RNTI is issued by gNB to UE in MSG2 first, not MSG4. The UE uses the TC-RNTI to scramble the uplink PUSCH message (MSG3).

[@WirelessExplained]

Agree. UE sends *ue-identity* as the unique identifier, not TC-RNTI. I have added this correction in the description. Thanks a lot for pointing this error 🙂

[@sukshithshetty8349]

First Question, how will one UE know which Zad Off Chu seq was selected by other UE??

[@WirelessExplained]

UE will not know. In contention based RACH procedure, a UE randomly choose a Zadoff Chu sequence, without knowing if any other UE also has chosen the same.

[@sukshithshetty8349]

When and where does RA-RNTI comes into picture???

[@sukshithshetty8349]

What is the use of Timing Advance?

[@WirelessExplained]

BS has to receive uplink signal from all UEs at the same time, i.e., time synchronized. So, far-away UEs transmit earlier than nearby UEs, so that all signals reach BS at the same time.

[@nitsr6053]

vey nice