NonTerrestrial Networks - 5G Advanced and Beyond.pptx

Presentation about NTN and 5G

1. Non-Terrestrial Networks: 5G-Advanced and Beyond Copyright© 2021 by Nishith D. Tripathi. All rights reserved. Dr. Nishith D. Tripathi Adjunct Associate Professor, Virginia Tech [email protected] Acknowledgments. The research presented here was supported by Samsung Research America. The content is public. Certain diagrams have been borrowed from the world’s first multimedia book on 5G: Nishith D. Tripathi and Jeffrey H. Reed, “5G Cellular Communications- Journey and Destination,” Multimedia Book, The Wireless University, https://thewirelessuniversity.com/ , April 2019.

2. About the Presenter- I Adjunct Associate Professor (Virginia Tech) Consulting Research Interests: 6G Design, Applications of 5G/6G & AI World’s first multimedia book on 5G! (with Prof. Jeff Reed) Textbook on Cellular Communications (with Prof. Jeff Reed) Expertise: 5G, AI, LTE-Advanced Pro, LTE-Advanced, LTE, IMS Pioneering work on applications of AI in cellular networks Contributor to FCC, CTIA, NSF, FTC, GSMA, Scientific American, CNN Business, EE Times University And…more than a decade of co-teaching the cellular communications class at VT! Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

3. About the Presenter- II 24 years with Commercial Cellular Networks Research in various aspects of commercial 3G, 4G, and 5G networks: design, testing, deployment, operations, troubleshooting, and optimization. Nortel: 3G 1x: BS/BSC Design (call admission control, scheduling), Simulation-based Prediction and Real-world Testing (13% capacity gain for load balancing: Can theory and practice meet ?! ). Huawei: 3G 1xEV-DO ( 3GPP: What is 1xEV-DV?! ) and 3G UMTS/WCDMA; Product Design: Many RRM algorithms such as scheduling, handover, and power control. Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

4. About the Presenter- III 24 years with Commercial Cellular Networks Award Solutions: Educated engineers about RF design, operations, troubleshooting, and optimization of live 3G, 4G, and 5G radio and core networks. Samsung: RAN2 lead for NTN (RAN1, RAN3, SA2), 6G vision paper, AI-based handover, Helper-in-Chief!, Educator for SRA and SEA. Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

5. Learning Goals Describe challenges faced by the NTN and discuss example solutions Summarize the security mechanisms used in the NTN Define an NTN and explain the motivation behind an NTN Give examples of future NTN enhancements Provide a “crystal ball perspective” of 6G! Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

6. 01 02 03 04 NTN: What & Why NTN: Challenges and Solutions NTN: Secuiry Mechanisms NTN: Beyond Release 17 05 6G Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

7. 01 NTN: What and Why Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

8. What is an NTN? NTN : A network that utilizes a communications platform at the altitude of more than tens of kilometers Platforms : Satellites (Ex: GEO, MEO, and LEO) and High-Altitude Platform Station (HAPS) Transparent Payload : (gNB on the ground with the platform as a repeater; Focus of Release 17) Future Releases : Regenerative (gNB or gNB-DU on the platform) Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

9. Why NTN? An NTN offers unique advantages such as service ubiquity, service scalability, and service continuity Service Ubiquity (Rural, Airborne, Maritime) Service Scalability (Broadcast/Multicast) Service Continuity (TN-NTN Continuity) NTN Use Cases Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

10. NTN Timeline Copyright© 2021 by Nishith D. Tripathi. All rights reserved. Release 15 Release 16 Release 17 Introduction of 5G (5G Phase 1) (2019) 5G Phase 2 and Completion of the “NTN” Study Item (2020) Introduction to the NTN as a formal feature. Target completion: First Half of 2022 (delayed due to COVID-19) Architecture: Transparent Payload Beams or Cells: Earth-fixed (Ex: GEO and HAPS), Quasi-Earth-Fixed (Ex: LEOs), and Earth-Moving (Ex: LEOs) UEs are GNSS-capable 5G-Advanced: R18 and beyond R18 18-month Timeline: To be identified in September 2021

11. 02 NTN: Challenges and Example Solutions Under Discussion in 3GPP Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

12. NTN Challenges Long and time-varying propagation delays (Ex: GEOs vs. LEOs) Large Doppler shifts (satellite speed: 7 km/s) 3 types of beams/cells: Earth-fixed, Quasi-Earth-Fixed (!) , Earth-Moving Large cells (Ex: 1200 km diameter): fewer resources/user, user location) Moving cells (moving cell identities, frequent and massive handover) Signal strength characteristics Elliptical beam coverage Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

13. Simple NTN Solutions Timing and frequency pre-compensation Extension of Timers (Ex: Extend timer values) Broadcast of Multiple Tracking Area Identities per NTN cell (More soon) Use of Configured Grant and Random Access Resources for reduced uplink scheduling delay (More soon) Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

14. Signal Strengths & Beam Coverage: NTN Implications Similar signal strengths: (i) cell center to cell edge (ii) serving and neighbor cells Traditional handover trigger : Neighbor Cell RSRP > (Serving Cell RSRP+ Δ ) Need a different handover trigger! The UE in NTN Cell 1 but incorrectly associated with Cell 2 due to the distance criterion that assumes a circular NTN cell. Need a different “location-based trigger”! Acknowledgment. These diagrams have been borrowed from 3GPP TR38.821 and Samsung R2-2107283. Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

15. Signal Strengths & Beam Coverage: The Solution Key Idea: Use a combination trigger that combines (i) the traditional signal strength criterion for the neighbor cell (NCSM: Neighbor Cell Signal Strength) and (ii) the distance-based criterion that uses an elliptical cell instead of a circular cell. Applicability of the “Inner Area” Idea: Handover, Cell Reselection, Neighbor Cell Search (save UE battery power), Random Access Type Selection (2-step vs. 4-step RA procedure) Criteria Inner Area Copyright© 2021 by Nishith D. Tripathi. All rights reserved. Acknowledgment. These diagrams have been borrowed from Samsung, R2-2107280 and R2-2107283

16. Implications for Handover in the NTN Challenge Implications for NTN Handover Large moving cells Massive handover: Tsunami of signaling! Excessive radio resource consumption for handover signaling Inefficient use of radio resources due to resource reservation at multiple handover candidate cells in case of Conditional Handover Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

17. Handover Enhancements in the NTN Key Ideas The UE informs the Source-gNB about the selected candidate handover candidate cell BEFORE accessing the candidate cell. The Source-gNB releases radio resources reserved at all other candidate cells. This reduces the amount of reserved radio resources. Remember the massive scale of handover! The Source-gNB conveys radio configurations in a suitable message using groupcast signaling instead of unicast signaling. The UE utilizes a resource-efficient method to send the handover completion message. Source gNB Target gNB 1. Radio Config (Groupcast) 2. ID of Selected Handover Candidate 3. Handover Completion Indication Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

18. Uplink Scheduling Enhancement Traditional Approach Proposed Approach Challenge: Overall delay: 2*Round Trip Time (RTT: Tens or hundreds of ms in the NTN!) Solution: Hybrid Scheduling Request + Simplified Buffer Status Report using minimal radio resource (control channel enhancement Copyright© 2021 by Nishith D. Tripathi. All rights reserved. Acknowledgment. These diagrams have been borrowed from Samsung R2-2107280.

19. Moving Cell Implications: Tracking Area Update Tracking Area (TA): A geographic area where a UE in the idle mode is paged by the core network (e.g., incoming voice call). TA Update: An NTN cell broadcasts the TA identity. A UE is registered in one or more TAs by the core network. If the UE encounters a TA that is not in its registered TA list, it carries out a TA Update (TAU) with the core network. TAU Problem in the NTN. A stationary UE sees different TAs being broadcast by the gNB due to moving NTN cells, leading to massive TAUs. Copyright© 2021 by Nishith D. Tripathi. All rights reserved. Acknowledgment. This diagram has been borrowed from 3GPP TR38.821.

20. TAU Solutions Example Solution: Utilize Earth-fixed TAs and broadcast time-varying TA identities as the moving NTN cell moves from one area to another. Challenges: The gNB must keep updating its TAI list, becasue its cell covers different TAs at different times. The TA change can occur any time depending on the layout of Earth-fixed TAs. Enhanced Solution : Define a mapping between Virtual Tas and TAIs broadcast by the cell. The UE does not carry out TAU if the broadcast TAI is part of registered VTAs. No additional work by the gNB! Reference: Samsung, R2-2107284. Copyright© 2021 by Nishith D. Tripathi. All rights reserved. Acknowledgment. This diagram has been borrowed from Samsung R2-2107284.

21. UE Location Requirements Requirement 1. Locate the UE in a geographic area (associated with a “Cell Global Identity” or CGI) that is comparable in size to a TN cell. Requirement 2. Connect the UE to the core network of the correct country. Let’s locate the UE in a “virtual cell” that has a cell radius of about 2 km. NTN Cell 1: Diameter= 1000 km NTN Cell 2: Diameter= 500 km Virtual Cell 1: Diameter= 20 km Virtual Cell 2: Diameter= 10 km Virtual Cell 3: Diameter= 4 km Baseline Concept. The UE compares its GNSS-based location coordinates with location coordinates of virtual cells of the current NTN cell to determine the virtual cell ID. Can the UE even do anything else?!! Copyright© 2021 by Nishith D. Tripathi. All rights reserved. Acknowledgment. This table has been borrowed from Samsung R2-2107284.

22. Solution: Hierarchical Geographic Areas Ideas: - Locate the UE in hierarchical geographic areas (Super Area/Area/Sub Area). - Define “Special Mobility Areas” to detect country crossing. Implication: Much less work for the UE to determine the virtual cell ID. Copyright© 2021 by Nishith D. Tripathi. All rights reserved. Acknowledgment. This diagram has been borrowed from Samsung R2-2107284.

23. 03 Security Mechanisms for the NTN Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

24. Security Mechanisms in 5G NTN: Re-use the existing security mechanisms of 5G defined for the TN! Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

25. Authentication and Key Agreement Framework Generate security keys for ciphering and integrity protection of user traffic and signaling Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

26. 04 NTN: Example Features Beyond R17 Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

27. Regenerative Payloads Regenerative Payload: At least some part of gNB processing on the NTN platform Copyright© 2021 by Nishith D. Tripathi and Jeffrey H. Reed. All rights reserved.

28. Inter-Satellite Link (ISL) The ISL enables the NTN to serve areas that are far away from the land (e.g., in the middle of an ocean). Copyright© 2021 by Nishith D. Tripathi and Jeffrey H. Reed. All rights reserved.

29. 05 6G Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

30. 6G: Target Services & Performance Goals Services: Digital Replica/Digital Twin High-fidelity holograms on a massive scale Energy harvesting Coordinated swarms of drones Sensing as a Service Performance Targets: Peak Data Rate: X Tbps ? Latency: Y microseconds? Z-year Long battery life for selected IoT devices? (Z > 10) Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

31. Key Enabling Technologies for 6G Artificial Intelligence (AI) Advanced RF and Optical Technologies Advanced Network Technologies Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

32. Example 6G Research Areas of Interest- I Multi-Network Super Connectivity - Go beyond Dual-RAT Dual Connectivity - TN+NTN, Higher-Performance + Regular-Performance, Multi- spectrum per service needs - Flexible and intelligent network selection (device types, service types, resource availability) Reconfigurable, Open, and Intelligent (ROI) Network - End-to-End design of the network - 6G-RAN, 6G Core Network, 6G Services Network, 6G Management Network - Reconfigurable and flexible aggregation and disaggregation - Security-hardened configuration as an option (not an afterthought!) - Support for AI-based optimization (device, network- various, hybrid) Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

33. Example 6G Research Areas of Interest- II Multi-Protocol Radio Protocol Stack - Selection of the most relevant protocol stack for a given service - Minimize signaling and processing overhead while maximizing utility - Support for 4G, 5G, and new 6G radio protocol stack Compact Representation of Ultra-rich Media - Need to represent holograms and immersive videos efficiently - Digital twin or digital replica - Support for ultra-rich media for a massive number of users Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

34. 6G Research Areas of Interest- III Spectrum Usage - THz for X-link communications (X: access, front haul mid haul, back haul, a-haul for adaptive haul!) - Recall: OFDM/OFDMA used in both 4G and 5G - Get an early start to be ready when time for standardization comes! Security-hardened 6G System - Security for defense applications: No longer an afterthought! - Provision adequate flexibility for commercial & defense applications - Significantly enlarged attack surface due to a massive number of devices connected to the network - Quantum Computing may break the existing 5G security framework Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

35. Key Takeaways An NTN involves the use of a radio equipment operating at the altitude of more than tens of kilometers. Key NTN challenges include long and variable propagation delays, moving cells, different types of beams, and large cells. To address the NTN challenges, solutions are needed for time and frequency synchronization, timers, tracking area management, and handover. The NTN reuses the comprehensive security framework defined by 5G for the TN. 6G will build on 5G and would likely achieve Tbps peak data rate and sub-1 ms latency. Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

36. References 3GPP, TS 38.821, “Solutions for NR to support non-terrestrial networks (NTN).” Samsung, R2-2107280,”User Plane Issues and Enhancements for an NTN,” https://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_115-e/Docs . Samsung, R2-2107281,”Remaining Beam Issues in an NTN: Tracking Area Management and Elliptical Beams,” https://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_115-e/Docs . Samsung, R2-2107282,”Cell Reselection, System Information, Paging Enhancements, and Power-Efficient Neighbor Cell Search for an NTN,” https://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_115-e/Docs . Samsung, R2-2107283,” Remaining Issues on Handover and Neighbor Search for an NTN,” https://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_115-e/Docs . Samsung, R2-2107284,”Area Management in an NTN,” https://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_115-e/Docs . Copyright© 2021 by Nishith D. Tripathi. All rights reserved.

37. Well wishes for your journey… May the Force be with you! Copyright© 2021 by Nishith D. Tripathi. All rights reserved.