Aerial base stations (ABSs) have emerged as a promising solution to meet the high traffic demands of future wireless networks. Nevertheless, their practical implementation requires efficient utilization of limited payload and onboard energy. Understanding the power consumption streams, such as mechanical and communication power, and their relationship to the payload is crucial for analyzing its feasibility. Specifically, we focus on rotary-wing drones (RWDs), fixed-wing drones (FWDs), and high-altitude platforms (HAPs), analyzing their energy consumption models and key performance metrics such as power consumption, energy harvested-to-consumption ratio, and service time with varying wingspans, battery capacities, and regions. Our findings indicate that FWDs have longer service times and HAPs have energy harvested-to-consumption ratios greater than one, indicating theoretically infinite service time, especially when deployed in near-equator regions or have a large wingspan. Additionally, we investigate the case study of RWD-BS deployment, assessing aerial network dimensioning aspects such as ABS coverage radius based on altitude, environment, and frequency of operation. Our findings provide valuable insights for researchers and telecom operators, facilitating effective cost planning by determining the number of ABSs and backup batteries required for uninterrupted operations.

Given the advancements in next-generation low Earth orbit (LEO) satellites, there is an expected shift from transparent architectures (acting as radio repeaters) to regenerative architectures (hosting a part or all of the gNodeB (gNB) onboard). Such regenerative architectures enable disaggregation and distribution of radio access network (RAN) functions between the ground and space. Open RAN is a promising approach for non-terrestrial networks and offers flexible function placement through open interfaces. The present study examines three open RAN-based regenerative architectures, namely, Split 7.2x (low-layer physical functions onboard), Split 2 (Layers 1 and 2 onboard), and a gNB onboard the satellite. Handover (HO) management becomes increasingly complex in this disaggregated RAN, particularly for LEO satellites, where the part of the gNB is constantly in motion. The choice of regenerative architecture and its dynamic topology influence the additional HO control signals required between the satellite and ground stations. Using a realistic dynamic LEO constellation model, we analyze the interplay among conditional handover (CHO) delay, computational complexity, and control signaling overhead under different network architectures. Our findings reveal that transitioning from a transparent architecture to Split 7.2x does not reduce CHO delay despite the introduction of additional onboard processing. The gNB onboard the satellite minimizes cumulative CHO delay but demands 55%-70% more computational resources than the Split 7.2x architecture. Conversely, although Split 7.2x is computationally more efficient, it increases the cumulative CHO delay by 25%-30%. Additionally, we observed that under limited onboard processing conditions, only the transparent and Split 7.2x architectures supported delay-sensitive services up to 100 ms. In contrast, under ample processing conditions, gNB was suitable for stringent 50 ms requirements, while Split 2 best supported delay-tolerant services with 200 ms requirements.

This paper addresses the challenge of optimizing handover (HO) performance in non-terrestrial networks (NTNs) to enhance user equipment (UE) effective service time, defined as the active service time excluding HO delays and radio link failure (RLF) periods. Availability is defined as the normalized effective service time which is effected by different HO scenarios: Intra-satellite HO is the HO from one beam to another within the same satellite; inter-satellite HO refers to the HO from one satellite to another where satellites can be connected to the same or different GSs. We investigate the impact of open radio access network (O-RAN) functional splits (FSs) between ground station (GS) and LEO satellites on HO delay and assess how beam configurations affect RLF rates and intra- and inter-satellite HO rates. This work focuses on three O-RAN FSs - split 7.2x (low layer 1 functions on the satellite), split 2 (layer 1 and layer 2 functions on the satellite), and gNB onboard the satellite - and two beam configurations (19-beam and 127-beam). In a realistic dynamic LEO satellite constellation where different types of HO scenarios are simulated, we maximize effective service time by tuning the time-to-trigger (TTT) and HO margin (HOM) parameters. Our findings reveal that the gNB onboard the satellite achieves the highest availability, approximately 95.4%, while the split 7.2x exhibits the lowest availability, around 92.8% due to higher intra-satellite HO delays.

As Non-terrestrial Networks (NTNs) becomes integral to future 6G systems, ensuring seamless connectivity and service continuity over Low Earth Orbit (LEO) satellite constellations is essential. This work investigates the impact of Open Radio Access Network (RAN) functional splits on handover performance in NTNs, focusing on minimizing service interruptions. We propose Effective Service Time as a novel availability metric that accounts for end-to-end Conditional Handover (CHO) delay, Radio Link Failures (RLFs), coverage gaps, and constellation-specific propagation dynamics-factors often simplified or ignored. Unlike baseline models that assume ideal, instantaneous switching with no protocol delays or topology changes, our CHO model reflects 3GPP-compliant, real-world constraints. Leveraging a digital twin-based satellite handover framework, we evaluate availability across multiple constellations, geographic regions, and Open RAN architectures (gNB onboard, Split 2, and Split 7.2x). Results reveal that increasing satellite density beyond a threshold yields diminishing returns, as denser constellations suffer more frequent handovers and higher downtime. For instance, a medium-density constellation with lower altitude achieves an average of 11 minutes of daily downtime, which rises to 13-16 minutes under a denser deployment. In contrast, a higher-altitude but sparser constellation provides only 5-7 minutes of downtime, benefiting from fewer handovers. Our analysis revealed that the claim of 99.9% availability in LEO is impractical, where we demonstrated that maximum 99.2% can be achieved with lower-altitude constellations. Moreover, functional splits impact performance: transitioning from gNB onboard to Split 7.2x can reduce availability from say about 99% to 98.5%. Finally, we construct a four-dimensional suitability map to identify optimal constellation-architecture pairings across a variety of service requirements defined by delay, modulation, reliability, and availability. Notably, stringent 50 ms delay requirements are not supported by higher-altitude constellations despite their higher availability, whereas lower-altitude constellations can satisfy them. This study provides valuable insights into NTN design, highlighting the interplay between satellite constellation, network architecture, and service-level guarantees.