Non-terrestrial networks (NTNs) have gained significant attention for their scalability and wide coverage in next-generation communication systems. A large number of NTN nodes, such as satellites, are required to establish a global NTN, but not all operators have the capability to deploy such a system. Therefore, cooperation among multiple operators, facilitated by an orchestrator, enables the construction of virtually large-scale constellations. In this paper, we propose a weak-control-based orchestration framework that coordinates multiple NTN operators while ensuring that operations align with the policies of both the orchestrator and the individual operators. Unlike centralized orchestration frameworks, where the orchestrator determines the entire route from source to destination, the proposed framework allows each operator to select preferred routes from multiple candidates provided by the orchestrator. To evaluate the effectiveness of our proposed framework, we conducted numerical simulations under various scenarios and network configurations including dynamic NTN environments with time-varying topologies, showing that inter-operator cooperation improves the availability of feasible end-to-end routes. Furthermore, we analyzed the iterative negotiation process to address policy conflicts and quantitatively demonstrated the “price of autonomy,” where strict individual policies degrade global feasibility and performance. The results also demonstrate that outcomes of the proposed framework depend on the operators’ policies and that hop count and latency increase as the number of operators grows. These findings validate the proposed framework’s ability to deliver practical benefits of orchestrated multi-operator collaboration in future NTN environments.

The interconnection of 5G and non-terrestrial networks (NTNs) has been actively studied to expand connectivity beyond conventional terrestrial infrastructure. In the 3GPP standardization of 5G systems, the 5G Quality of Service (QoS) Identifier (5QI) is defined to characterize the QoS requirements of different traffic requirements. However, it falls short in capturing the diverse latency, capacity, and reliability profiles of NTN environments, particularly when NTNs are used as backhaul. Furthermore, it is difficult to manage individual traffic flows and perform efficient resource allocation and routing when a large number of 5G traffic flows are present in NTN systems. To address these challenges, we propose an optimization framework that enhances QoS handling by introducing an NTN QoS Identifier (NQI) and grouping 5G traffic into NTN slices based on similar requirements. This enables unified resource control and routing for a large number of 5G flows in NTN systems. In this paper, we present the detailed procedure of the proposed framework, which consists of 5QI to NQI mapping, NTN traffic to NTN slice mapping, and slice-level flow and routing optimization. We evaluate the framework by comparing multiple mapping schemes through numerical simulations and analyze their impact on overall network performance.

Satellite communication is increasingly essential and widely used, especially with the rapid development of the Internet of Things (IoT) and networks beyond fifth-generation (B5G), providing ubiquitous coverage. However, the current reactive approaches to optimize resources have become inadequate due to the massive rise in IoT traffic with varying patterns and limited resources of satellite networks. These approaches fail to predict dynamic traffic and its requirements. To efficiently allocate satellite communication resources as necessary, there is a need to proactively predict traffic demand. We propose utilizing mobile edge computing-enabled high altitude platform stations (HAPS) to predict traffic from ground users to satellite networks at HAPS. However, resource control based on traffic prediction in satellite networks faces challenges such as the wastage of resources or insufficient resource availability due to misaligned traffic variations and resource control timing. To overcome these challenges, we propose a dynamic scheduling strategy for resource control based on traffic demand prediction. This strategy aims to reduce resource wastage in satellite communication systems. Our proposed approach can predict traffic with high accuracy and allocate resources with minimal difference between achievable throughput and required throughput, demonstrating high resource utilization. We evaluated the effectiveness of our scheduling strategy through simulation analysis by comparing it with periodic resource control.

At present, discussions on information and communication technologies for Beyond-5G/ 6G are accelerating. In the field of space communications, satellite communications are becoming more advanced and active, and it is expected that an advanced information and communication network will be realized that links the earth and space with satellites. In the Beyond 5G/6G era, spatial network expansion is required, and advanced communication with mobile devices called non-terrestrial networks will become important. This paper describes the efforts and the status of R&D regarding the developments of satellite communications and non-terrestrial networks (NTN) toward Beyond-5G/6G in Japan.

The demand for satellite communication increases with digitalization and globalization in the era of 5G and beyond; therefore, research and development of high-throughput satellites (HTSs) to increase the communication capacity and improve the flexibility of satellite communication systems is underway. Additionally, digital beamforming (DBF), which can control the directivity of multiple beams through high-speed digital signal processing, has received significant attention as a technology to improve the flexibility of resource allocation with HTSs. The principal control parameters in the DBF-based HTS, including the transmission power, beam gain, and placement location of each beam, cause alterations in the positional characteristics of the total throughput in the coverage area of an HTS. However, there are no power resource allocation models with dual control of these control parameters, based on the above positional characteristic. This study clarifies the effect of such control parameters on the total throughput in the coverage area of an HTS. We demonstrate a method for improving the flexibility of resource allocation to satisfy the geographic distribution of traffic requirements by constructing a power resource allocation model with a DBF-based fusion control in the HTS communication system. We evaluated the effectiveness of our proposed method through a simulation analysis using exponential annealing.

In recent years, the expectations for high throughput satellite (HTS) have diversified based on rapid increase in traffic demands. However, the Ku-band and Ka-band utilized by HTS are growing tighter. It is necessary to utilize the limited frequency ranges efficiently and share resources with other communication systems. The digital beam forming (DBF), which has a high area flexibility for allocating power resources, is being developed to adapt to the diversification of communication applications. However, it remains unclear how multi-spot beam placement is related to throughput in an HTS communication system equipped with DBF. In this study, we attempted to determine how the distances between spot beams in the same frequency band and the distances between adjacent spot beams in different frequency bands are related to overall system throughput and to derive a multi-spot beam arrangement to improve overall system throughput. The main contributions of this study are the clarification of relationships between the positions of multi-spot beams and overall system throughput and the construction of a novel mathematical model to derive multi-spot beam arrangements to enhance overall throughput. The effectiveness of our proposal is evaluated through numerical analysis.

Satellite communication systems have attracted considerable attention recently because they can communicate in various conditions, including terrestrial, airspace, and marine terrain. In addition, high-throughput satellites (HTSs) that allow high-speed and large-capacity communication are currently being launched. However, the allocation of communication resources to each beam is fixed in conventional HTSs, which exhibit low flexibility under state changes. This includes requests to the satellite communication systems or environmental changes around the systems. Therefore, the use of a digital channelizer in a satellite communication system can allocate frequency resources to each beam. However, even if a digital channelizer is used, conventional frequency resource allocation methods that consider inter-beam interference do not use the same frequency resource as the adjacent beam. As a result, the frequency resources cannot be used effectively. To alleviate this issue, we propose a frequency resource allocation method with inter-beam interference so that the satellite communication system can allocate frequency resources more flexibly. In addition, we extend the conventional flexibility analysis model such that it quantifies the flexibility more accurately. Finally, the effectiveness of the proposed method is demonstrated under state changes of the satellite communication system using the extended flexibility analysis model.

High Throughput Satellite (HTS), which has large communication capacity, is being developed to meet the rising demand for satellite communication system at the time of disaster. However, HTS adopts static frequency resource allocation, hence it is difficult to effectively utilize frequency resources. Therefore, many technologies for effectively utilizing frequency resources have been developed. However, the effectiveness of such technologies was not revealed clearly, because there was no quantitative evaluation method to measure their effectiveness. To create such method of evaluation, it is essential to consider the flexibility of frequency resource allocation. Thus, the construction of an evaluation method for flexibility is an important research issue. Therefore, in this research, we aim to construct a system analysis model to measure the effectiveness of frequency flexibility of satellite communication systems. Furthermore, we evaluate the effectiveness of frequency flexibilization technologies and quantitatively show the validity of such technologies.

Helicopter videoing is one of the most popular methods to acquire on scene information for disaster management and relief. We developed an on scene disaster information transmission system using Ku-band helicopter satellite communications. The main obstacle for a helicopter satellite communication link is the interruption by the rotating blades of the helicopter. To overcome the blade interruption, we use a time diversity transmission technique at the forward link and a blade-synchronized transmission technique at the return link. Furthermore, onboard position estimation is done for the on scene videoing pictures. Some primary field experiments have been done with satisfactory results.

A real time system for disaster information collection and transmission using ka-band aeronautical satellite communications has been developed. This system is composed of three subsystems: a Ka-band aeronautical satellite communication (KASC) subsystem, a position-estimation and data-processing (PEDP) subsystem, and an information-distributing Internet application subsystem. Experiments to examine the performance of the overall system have been carried out. In this paper, we'll outline the overall experimental system and present some experiment results.