5G-gNB

5G secondary node addition

5G-gNB.pdf

LTE-5GNR LTE- 5GNR UE

LTE eNodeB

5G-NR gNodeB

4G Core Network

UE

MN-eNB MNeNB

SN-gNB

SGW

 

Measure 5G NR Synchronization Signal Blocks (SSBs) 1:NR 1:N R PSS P SS

UE acquires the 5G-NR Primary Synchronization Signal.

2:NR SSS

UE acquires the 5G-NR Secondary Synchronization Signal and measures the signal quality.

RRC Connection Reconfiguration for dual connectivity with the 5G network 3:X2AP SgNB S gNB Addition Request Request

 The 4G LTE eNo  The Node deB B de deci cide dess to to add th the e 5G-NR ba base se st sta atio ion n as a secondary node. The eNodeB sends a Secondary Node Addition Request to the gNodeB. The message carries the RRC and Radio Bearer configuration. UE capabilities and security information are also included in the message.  The ne  The nettwo work rk in indi dica cattes whe whetthe herr the the UE sh sha all us use e eit ithe herr Ke KeNB (m (ma ast ste er node key) or S-KgNB (secondary node key) for the 5G DRB.

allocate 4:PScell and SCells allocate 5:5G Resources (C-RNTI, CQI, SR, SRS) 6:Prepare NR RRC Configuration [SGC Radio Resource Configuration]

Allocate 5G cells Allocate the 5G radio resources needed for the secondary session.

 The NR RRC Con  The onfig figu ura rattio ion n will be tr tra ans nsm mit ittted to th the e UE via th the e MN-eNB.

7:X2AP SgNB Addition Request Acknowledge

 The gN  The gNod ode eB re resp spon ond ds wit with h in info form rma atio ion n abou outt th the e ra radi dio o re reso sour urce cess and and bearers admitted with the 5G network. The NR RRC configuration message is included in the message.

8:X2AP SgNB Reconfiguration Complete

 The 4G eNo  The Node deB B in info form rmss the the se seco cond nda ary no node de (g (gNo Node deB) B) abo bout ut the reconfiguration complete. The "NR RRC Reconfiguration Complete" message is delivered to the SN-gNB via the "MeNB to SgNB" container.

eNodeB starts copying data to the gNodeB 9:SN Statu Statuss Transfer

eNodeB informs the gNodeB about the PDCP SN and HFN for all the bearers that are being transferred to 5G.

10:Data

SGW is sending data to the MN-eNB. The MN-eNB keeps forwarding that data to the SN-gNB.

begin 11:Buffering data

At this point, the gNodeB is buffering the data as the UE has not established the 5G path.

Path update procedure 12:GTPv2 End Marker Packet

13:GTP PDU

Send the End Marker to the eNodeB. This marks the end of data transmission to the 4G-eNodeB. Subsequent data transmissions will be towards the 5G-gNodeB. Data is now being sent directly to the 5G-gNodeB.

UE connects to the 5G network 14:NR PSS

20-Feb-19

UE acquires the 5G-NR Primary Synchronization Signal.

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5G secondary node addition

5G-gNB.pdf

LTE-5GNR LTE- 5GNR UE

LTE eNodeB

5G-NR gNodeB

4G Core Network

UE

MN-eNB MNeNB

SN-gNB

SGW

15:NR SSS

 

UE acquires the 5G-NR Secondary Synchronization Signal.

16:NR PBCH [MIB]

UE acquires the 5G-NR Broadcast Channel.

17:NR RACH Preamble (Msg1)

 The UE in  The init itia iattes th the ra rand ndom om-a -acc cce ess pr proc oce edu dure re wit ith h th the e 5G gN gNod ode eB. Non-contention based random-access will be attempted if the preamble assignment was received in the RRC Connection Reconfiguration message.

18:NR PDCCH DCI 1_0 [RA-RNTI]

NR PDCC P DCCH H signals downlink resource allocation allocation for the RA Response.

19:NR PUSCH RA Response (Msg2)

 The 5G se  The seco con nda dary ry no node de gN gNod ode eB re resp spon ond ds wit with h an RA Re Resp spon onse se.. The The message also carries an uplink grant for Msg3 transmission.

end 20:Buffering data

 The  Th e gN gNod ode eB st stop opss buf buffe ferin ring g da data ta and st sta art rtss da data tra ran nsm smiss issio ion. n.

Data flow resumed over 5G 21:GTP PDU 22:NR PDCCH DCI 1_0

Data is now being directly routed from the 4G SGW to the 5G gNodeB. NR PDCCH signals downlink resource block allocations for PDSCH.

23:NR 23:N R PDSCH [MAC PDU] P DU]

 The  Th e eNo Node deB B tra ran nsm smit itss the the PDS PDSC CH.

24:NR PDCCH DCI 0_0

gNodeB gNode B assigns uplink resource blocks.

25:NR 25:N R PUSCH P USCH [MAC PDU]

 The UT re  The rece ceiv ive es the the DCH 0_0 gr gra ant and tra ran nsm smit itss the the PUSC PUSCH H in the uplink direction. 26:GTP PDU

Periodic reporting between eNB and gNB 27:RRC Container 28:Secondary RAT Data Usage Report 29:gNB Status Indication

20-Feb-19

 The  Th e MN-e MN-eNB NB re rep por ortts the these se measu sure rem ment ntss to to th the e SN SN-gN -gNB. B. Periodically, the SN-gNB reports the usage statistics for 5G NR bearers to the MN-eNB.  The  Th e SN SN-gN -gNB B also re repo port rtss any any ov ove erlo rloa ad in info form rma ati tion on to the MN-e MN-eNB NB..

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