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SA Initial Attach Sequence

 

Following is high level sequence of call processing with SA(Stand Alone) initial attach process. For the simplicity, I have listed the sequence that is exchanged between UE and NW(Network) over the air (OTA). In reality, there are a lot of other signalings happending in corenetwork during the attach process. For corenetwork side signaling, refer to ref [2] from event Helix which is very nicely written sequence diagram.

The detailed mechanism for each of these step is very complicated process which cannot be described in the single page. Try follow through the hyperlink at each step if you want further details. Notice that there are multiple linkes even at single step. I am just trying to provide just high level / skeleton in this page.   

 

Step

Direction

Message

Comment

1

UE <- NW

SSB (PSS,SSS,MIB)  

2

UE <- NW

PDCCH / CORESET 0 / DCI 1_0  

3

UE <- NW

SIB1  

4

UE <- NW

PDCCH / DCI 1_0  

5

UE <- NW

Other SIBs  

6

UE -> NW

Msg1 (PRACH/Preamble)  

7

UE <- NW

(PDCCH / DCI 1_0, RA_RNTI)

 

8

UE <- NW

Msg2 (PDSCH / Random Access Response)  

9

UE -> NW

Msg3 (RRC Setup Request)  

10

UE <- NW

(PDCCH / DCI 1_0, T_C_RNTI)

 

11

UE <- NW

Msg4 (PDSCH / CR+RRC Setup)  

12

UE <- NW

(PDCCH / DCI 0_0 or 0_1, C_RNTI)

 

13

UE -> NW

PUCCH or PUSCH / UCI (HARQ ACK/NACK)

 

14

UE -> NW

(PUSCH) RRCSetupComplete+NAS:RegistrationRequest  

15

UE <- NW

(PDCCH/ DCI 1_0 or 1_1, C_RNTI)

 

16

UE <- NW

(PDSCH) NAS:IdentityRequest

 

17

UE -> NW

PUCCH or PUSCH / UCI (HARQ ACK/NACK)

 

18

UE <- NW

(PDCCH/ DCI 0_0 or 0_1, C_RNTI)

 

19

UE -> NW

(PUSCH) NAS:IdentityResponse

 

20

UE <- NW

(PDCCH/ DCI 1_0 or 1_1, C_RNTI)

 

21

UE <- NW

(PDSCH) NAS:AuthenticationRequest

 

22

UE -> NW

PUCCH or PUSCH / UCI (HARQ ACK/NACK)

 

23

UE <- NW

(PDCCH/ DCI 0_0 or 0_1, C_RNTI)

 

24

UE -> NW

(PUSCH) NAS:AuthenticationResponse

 

25

UE <- NW

(PDCCH/ DCI 1_0 or 1_1, C_RNTI)

 

26

UE <- NW

(PDSCH) NAS:SecurityModeCommand

 

27

UE -> NW

PUCCH or PUSCH / UCI (HARQ ACK/NACK)

 

28

UE <- NW

(PDCCH/ DCI 0_0 or 0_1, C_RNTI)

 

29

UE -> NW

(PUSCH) NAS:SecurityModeCommandComplete

 

30

UE <- NW

(PDCCH/ DCI 1_0 or 1_1, C_RNTI)

 

31

UE <- NW

(PDSCH) RRC:SecurityModeCommand

 

32

UE -> NW

PUCCH or PUSCH / UCI (HARQ ACK/NACK)

 

33

UE <- NW

(PDCCH/ DCI 0_0 or 0_1, C_RNTI)

 

34

UE -> NW

(PUSCH) RRC:SecurityModeCommandComplete

 

35

UE <- NW

(PDCCH/ DCI 1_0 or 1_1, C_RNTI)

 

36

UE <- NW

(PDSCH) RRCReconfiguration + NAS : Registration Accept

 

37

UE -> NW

PUCCH or PUSCH / UCI (HARQ ACK/NACK)

 

38

UE <- NW

(PDCCH/ DCI 0_0 or 0_1, C_RNTI)

 

39

UE -> NW

(PUSCH) RRCReconfigurationComplete + NAS : Registration Complete

 

40

UE <- NW

(PDCCH/ DCI 0_0 or 0_1, C_RNTI)

 

41

UE -> NW

(PUSCH) ULInformationTransfer + UL NAS Transport

            + PDU Session Establishment Request

 

42

UE <- NW

(PDCCH/ DCI 0_0 or 0_1, C_RNTI)

 

43

UE -> NW

(PDSCH) DLInformationTransfer + DL NAS Transport

           + PDU Session Establishment Accept

 

44

UE -> NW

PUCCH or PUSCH / UCI (HARQ ACK/NACK)

 

 

 

 

Example 01 > NR SA Initial Registration Sequence - Amarisoft

 

Following is a sample protocol sequence for NR SA Registration kindly provided by Amarisoft in its web based log viewer

For the example of the contents of these messages click on the message link shown in the above table.

 

 

 

Reference

 

[1] 5G Standalone Access Registration Signaling Messages

[2] 5G Standalone Access: Registration Procedure