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Add NRPPA call flow for UL-TDOA positioning

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Signed-off-by: Rakesh Mundlamuri <rakesh.mundlamuri@openairinterface.org>
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Rakesh Mundlamuri
2026-05-28 14:25:15 +05:30
parent 373d0095e7
commit 258c22da60
1 changed files with 72 additions and 0 deletions
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doc/NRPPA/NRPPA-call-flow.md Normal file
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```mermaid
sequenceDiagram
participant UE as UE
participant TRP1 as TRP 1 <br/>(Serving Antenna/RU)
participant TRP2 as TRP 2 <br/>(Neighbor Antenna/RU)
participant DU as gNB-DU <br/>(Single Baseband)
participant CU as gNB-CU
participant AMF as AMF
participant LMF as LMF
participant API as External API
API->>LMF:HTTP Post: <br> Determine Location (InputData)
Note over UE, LMF:TRP Information Exchange
LMF->>AMF: NRPPa TRP INFORMATION REQUEST
AMF->>CU: NGAP Downlink Non-UE Associated NRPPa <br> (NRPPa TRP INFORMATION REQUEST)
CU->>DU: F1AP TRP INFORMATION REQUEST <br> (Query TRP 1 & TRP 2)
DU->>CU: F1AP TRP INFORMATION RESPONSE <br> (Lat/Long for TRP 1 & TRP 2)
CU->>AMF: NGAP Uplink Non-UE Associated NRPPa <br> (NRPPa TRP INFORMATION RESPONSE)
AMF->>LMF: Namf_Comm_N2InfoNotify
Note over UE, LMF: SRS Configuration
LMF->>AMF: NRPPa POSITIONING INFORMATION REQUEST
AMF->>CU: NGAP Downlink UE Associated NRPPa <br> (NRPPa POSITIONING INFORMATION REQUEST)
CU->>DU: F1AP POSITIONING INFORMATION REQUEST
Note right of DU: DU allocates SRS Config<br/>(Comb, Shift, Periodicity)
DU->>CU: F1AP POSITIONING INFORMATION RESPONSE
CU->>AMF: NGAP Uplink UE Associated NRPPa <br> (NRPPa POSITIONING INFORMATION RESPONSE)
AMF->>LMF: Namf_Comm_N2InfoNotify
Note over UE, LMF: Activation
LMF->>AMF: NRPPa POSITIONING ACTIVATION REQUEST
AMF->>CU: NGAP Downlink UE Associated NRPPa <br> (NRPPa POSITIONING ACTIVATION REQUEST)
CU->>DU: F1AP POSITIONING ACTIVATION REQUEST
Note right of DU: DU look for SRS (periodic)
DU->>CU: F1AP POSITIONING ACTIVATION RESPONSE
CU->>AMF: NGAP Uplink UE Associated NRPPa <br> (NRPPa POSITIONING ACTIVATION RESPONSE)
AMF->>LMF: Namf_Comm_N2InfoNotify
Note over UE, LMF: Measurement (Distributed TRPs)
LMF->>AMF: NRPPa MEASUREMENT REQUEST
Note right of LMF: Request: Measure UL-RTOA on TRP 1 & TRP 2
AMF->>CU: NGAP Downlink UE Associated NRPPa <br> (NRPPa MEASUREMENT REQUEST)
CU->>DU: F1AP POSITIONING MEASUREMENT REQUEST <br> (List: TRP 1, TRP 2)
Note right of DU: DU already manages the UE Context<br/>and inherently knows the SRS config to use for both TRPs
Note right of UE: UE Transmits SRS
UE->>TRP1: UL SRS Transmission
UE->>TRP2: UL SRS Transmission
TRP1-->>DU: IQ Samples / Baseband Timing
TRP2-->>DU: IQ Samples / Baseband Timing
Note right of DU: DU calculates UL-RTOA for TRP 1 & TRP 2
DU->>CU: F1AP POSITIONING MEASUREMENT REPORT <br> (UL-RTOAs for TRP 1 & TRP 2)
CU->>AMF: NGAP Uplink UE Associated NRPPa <br> (NRPPa MEASUREMENT RESPONSE)
AMF->>LMF: Namf_Comm_N2InfoNotify
Note over UE, LMF: Calculation
Note right of LMF: LMF computes TDOA:<br/>(RTOA_TRP2 - RTOA_TRP1)
```