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Feasibility Study of Function Splits in RAN Architectures with LEO Satellites

Siva Satya Sri Ganesh Seeram, Luca Feltrin, Mustafa Ozger, Shuai Zhang, Cicek Cavdar

TL;DR

Addresses the feasibility of RAN function splits (FS) for NTN using LEO satellites to handle rising mobile traffic. The authors evaluate static and mobile NTN scenarios across ten FS options, focusing on fronthaul latency, maximum separation distance, FH bandwidth, and CHO performance, with propagation-delay estimates for SL/FL/ISL/IGSL as a function of elevation angle. They find that strict FH latency constraints and small separation distances largely constrain lower-layer splits, though relaxing LTE NR NTN assumptions (e.g., HARQ/CSI) can render LLS feasible; higher-layer splits reduce FH burden but require more onboard processing and payload. The results highlight a trade-off between onboard computation and FH performance, suggesting hybrid architectures with selective onboard gNB functions to balance mobility performance and payload.

Abstract

This paper explores the evolution of Radio Access Network (RAN) architectures and their integration into Non-Terrestrial Networks (NTN) to address escalating mobile traffic demands. Focusing on Low Earth Orbit (LEO) satellites as key components of NTN, we examine the feasibility of RAN function splits (FSs) in terms of fronthaul (FH) latency, elevation angle, and bandwidth (BW) across LEO satellites and ground stations (GS), alongside evaluating performance of Conditional Handover (CHO) procedures under diverse scenarios. By assessing performance metrics such as handover duration, disconnection time, and control traffic volume, we provide insights on several aspects such as stringent constraints for Low Layer Splits (LLSs), leading to longer delays during mobility procedures and increased control traffic across the feeder link in comparison with the case when gNodeB is onboard satellite. Despite challenges, LLSs demonstrate minimal onboard satellite computational requirements, promising reduced power consumption and payload weight. These findings underscore the architectural possibilities and challenges within the telecommunications industry, paving the way for future advancements in NTN RAN design and operation.

Feasibility Study of Function Splits in RAN Architectures with LEO Satellites

TL;DR

Addresses the feasibility of RAN function splits (FS) for NTN using LEO satellites to handle rising mobile traffic. The authors evaluate static and mobile NTN scenarios across ten FS options, focusing on fronthaul latency, maximum separation distance, FH bandwidth, and CHO performance, with propagation-delay estimates for SL/FL/ISL/IGSL as a function of elevation angle. They find that strict FH latency constraints and small separation distances largely constrain lower-layer splits, though relaxing LTE NR NTN assumptions (e.g., HARQ/CSI) can render LLS feasible; higher-layer splits reduce FH burden but require more onboard processing and payload. The results highlight a trade-off between onboard computation and FH performance, suggesting hybrid architectures with selective onboard gNB functions to balance mobility performance and payload.

Abstract

This paper explores the evolution of Radio Access Network (RAN) architectures and their integration into Non-Terrestrial Networks (NTN) to address escalating mobile traffic demands. Focusing on Low Earth Orbit (LEO) satellites as key components of NTN, we examine the feasibility of RAN function splits (FSs) in terms of fronthaul (FH) latency, elevation angle, and bandwidth (BW) across LEO satellites and ground stations (GS), alongside evaluating performance of Conditional Handover (CHO) procedures under diverse scenarios. By assessing performance metrics such as handover duration, disconnection time, and control traffic volume, we provide insights on several aspects such as stringent constraints for Low Layer Splits (LLSs), leading to longer delays during mobility procedures and increased control traffic across the feeder link in comparison with the case when gNodeB is onboard satellite. Despite challenges, LLSs demonstrate minimal onboard satellite computational requirements, promising reduced power consumption and payload weight. These findings underscore the architectural possibilities and challenges within the telecommunications industry, paving the way for future advancements in NTN RAN design and operation.
Paper Structure (6 sections, 6 figures, 2 tables)

This paper contains 6 sections, 6 figures, 2 tables.

Table of Contents

  1. Introduction
  2. RAN Architectures
  3. Analysis of FSs in a Static NTN Scenario
  4. Analysis of FSs based on mobile NTN scenarios
  5. Results and analysis
  6. Conclusions

Figures (6)

  • Figure 1: Overview of RAN architecture.
  • Figure 2: Reference scenarios (a) A - 1 satellite and 1 GS, (b) B - 2 satellites and 1 GS, (c) C - 2 satellites and 2 GSs.
  • Figure 3: Complete message exchange associated with each procedure.
  • Figure 4: CHO performance for scenario A.
  • Figure 5: CHO performance for scenario B.
  • ...and 1 more figures