Summary of S4-260149: Updates on Assumptions and Open Issues for NB-IoT GEO Simulation

Document Overview

This contribution from China Mobile addresses outstanding assumptions and open issues for NB-IoT GEO satellite simulation work within the ULBC (Ultra-Low Bitrate Codec) study. The document consolidates discussions from multiple Audio Ad-hoc meetings (June 4, June 17, and July 11) and proposes updates to TS 26.940 clause 5.2.2.4.

Main Technical Contributions

Status Updates on Simulation Parameters

The document provides a comprehensive status table tracking 11 key simulation issues, with updates on their resolution status:

Resolved Issues

1. UE Power Class (Issue 1):
2. Previously pending decision between 23 dBm (specified for NTN NB-IoT) vs. higher commercial values (26-33 dBm)
3. Resolution: 37 dBm adopted based on RAN4 Reply LS S4aA250219

4. Note: 37 dB is under study in ongoing RAN work

5. Latitude-Dependent Loss (Issue 2):

6. Addressed scintillation loss variation (2.2 dB vs. 0 dB) based on latitude per TR 38.821
7. Resolution: Simulation accounts for latitude-dependent loss using X term

8. Additional note: New 10-degree channel model introduced, may increase feasible TBS

9. Elevation Angles (Issue 3):

10. Proposal to maintain both 2.3° and 12.5° elevation angles for worst-case scenarios

11. Resolution: Simulation accounts for elevation angles using X term

12. Simulation Channel Model (Issue 8):

13. Choice between NTN-TDL-C or NTN-TDL-C5

14. Resolution: NTN-TDL-C is used

15. Repetition Numbers (Issue 10):

16. Proposal to specify and report repetition numbers in simulation
17. Resolution: Solved

Partially Resolved Issues

1. Protocol Overhead (Issue 9):
2. Requires clarification of packet header overhead for different protocol combinations (user plane, control plane, IP vs. non-IP)
3. Partial Resolution: SA2 confirmed voice packets transported over User Plane

4. Still Pending: Overhead for User Plane (IP vs. Non-IP) needs RAN confirmation

5. RX G/T for Downlink (Issue 11):

6. Field measurements show 3dB better value than current RAN assumptions
7. Status: Editorial note added in P-doc 5.2.2.3 to capture field-measured data
8. Current Status: Listed as "Unsolved" in table

Unresolved Issues

1. UL/DL Guard Time (Issue 4):
2. Current assumption: 1 ms guard time for UL/DL switching

3. Status: Needs RAN confirmation on feasibility

4. Determine Candidate TBS Values (Issue 5):

5. Multiple proposals from different companies:
   • Xiaomi (S4aA250035)
   • Fraunhofer (S4aA250031)
   • Skylo (S4-251540)
   • Dolby (S4-251390)
   • Huawei (S4aA250230)
   • Qualcomm (S4-251548)
   • vivo (S4aA250215)

6. Status: Unsolved, requires further verification

7. Approaches to Select TBS (Issue 6):

   • Three approaches provided in S4aA250072
   • One approach detailed in clause 5.2.2.4.1
   • Status: Unsolved, requires further discussion

8. Overall Simulation Methodology Description (Issue 7):

   • Need for high-level description of simulation execution, including optimization parameters and result parameters
   • General description documented in P-doc Clause 5.2.2
   • Status: Unsolved, to be addressed after all simulation work completed

Proposal

The document proposes to:
1. Update the P-doc (TS 26.940) based on the status updates provided
2. Continue tracking these issues until full resolution

Key Dependencies

The document highlights several dependencies on other working groups:
- RAN4: UE power class confirmation
- RAN: UL/DL guard time feasibility, protocol overhead confirmation
- SA2: Protocol overhead for different transport configurations