Building upon the significant number of already published 6G position papers, we are concentrating on the immediate next steps toward turning the research vision of software-centric networks into reality. This is accomplished, by summarizing and assessing the various requirements documents and providing a significant number of specific research directions and approaches in order to fulfill them. This article complements the existing body of work, by focusing on future core networks and their infrastructures, yet maintaining a system level perspective and progressing in the direction of scoping key technology elements and providing high-potential research approaches for them. Additionally, we rigorously discuss the impact different technological advancements have on the other parts of the system, so as to provide a coherent, end-to-end network understanding. This is in strong contrast to current approaches where from the challenges, each research direction becomes independent and thus, its advances are cancelled out by the next technology in the chain. By maintaining this system perspective, the adoption of the different technologies becomes easier, as they are developed in unison. To address the requirements in a coherent, holistic and unified way, we introduce the high-level architecture concept named “Organic 6G Networks”. A holistic software-centric system, adapting the latest software development advancements from the IT industry. The Organic 6G network provides the support for building a streamlined software network architecture and to provide a next development and specification step for future mobile networks.

The 5G vision embraces a broad range of applications including the connectivity in underserved and remote areas. In particular, for these applications, satellites are going to play a role in future 5G networks to provide capacity on trains, vessels, aircraft, and for base stations around the globe. In this paper, a 5G edge node concept, developed and evaluated with over-the-air tests using satellites in the geostationary orbit, is presented. The article covers a testbed demonstration study in Europe with a large-scale testbed including satellites and the latest standardization for the network architecture. The main goal of this testbed is to evaluate how satellite networks can be best integrated within the convergent 5G environment. The over-the-air tests for 5G satellite integration in this article are based on a 3GPP Release 15 core network architecture.

Satellite communications systems provide a means to connect people and devices in hard-to-reach locations. Traditional geostationary orbit (GEO) satellite systems and low Earth orbit (LEO) constellations, having their own strengths and weaknesses, have been used as separate systems serving different markets and customers. In this article, we analyze how satellite systems in different orbits could be integrated together and used as a multi-layer satellite system (MLSS) to improve communication services. The optimization concerns combining the strengths of different layers that include a larger coverage area as one moves up by each layer of altitude and a shorter delay as one moves down by each layer of altitude. We review the current literature and market estimates and use the information to provide a thorough assessment of the economic, regulatory, and technological enablers of the MLSS. We define the MLSS concept and the architecture and describe our testbed and the simulation tools used as a comprehensive engineering proof-of-concept. The validation results confirm that the MLSS approach can intelligently exploit the smaller jitter of GEO and shorter delay of LEO connections, and it can increase the availability and resilience of communication services. As a main conclusion, we can say that multi-layered networks and the integration of satellite and terrestrial segments seem very promising candidates for future 6G systems.

With the widespread adoption of 5G as a communication standard, satellite mega-constellations have emerged as viable alternatives and complement terrestrial networks, offering extensive and reliable communication services across a broad spectrum of users and applications. These constellations are already equipped with inter-satellite links and adaptable payloads capable of supporting Radio Access Network (RAN) and core network functionalities, forming complex space-based networks characterized by overlapping layers of multi-orbit, grid-like topologies that undergo continuous, yet predictable, changes—peculiarities not currently addressed within the 5G standards framework. To cope with this technology gap, this paper introduces a novel architecture for 5G services relying on satellite mega-constellations, which adhere to the principles of self-organized networks. This architecture is designed to align seamlessly with 5G service requirements, while also accommodating the unique topological and infrastructural constraints of mega-constellations. In more detail, the paper first outlines the fundamental principles of self-organizing networks that facilitate real-time system adaptation to internal topological shifts and external fluctuations in service demand. Then, we detail a 5G network architecture incorporating these principles, which includes i) dynamic placement and migration of radio and core network control plane functions, ii) the strategic positioning of the data path, service, and AI decision functionalities to improve end-to-end service quality and reliability, and iii) the integration of dynamically established multi-connectivity options to increase the overall service dependability. These innovations aim for a seamless integration of space-based networks with terrestrial counterparts, creating a robust, cost-effective convergent telecommunication system.

With the wide adoption of edge compute infrastructures, an opportunity has arisen to deploy part of the functionality at the edge of the network to enable a localized connectivity service. This development is also supported by the adoption of “on-premises” local 5G networks addressing the needs of different vertical industries and by new standardized infrastructure services such as Mobile Edge Computing (MEC). This article introduces a comprehensive set of deployment options for the 5G network and its network management, complementing MEC with the connectivity service and addressing different classes of use cases and applications. We have also practically implemented and tested the newly introduced options in the form of slices within a standard-based testbed. Our performed validation proved their feasibility and gave a realistic perspective on their impact. The qualitative assessment of the connectivity service gives a comprehensive overview on which solution would be viable to be deployed for each vertical market and for each large-scale operator situation, making a step forward towards automated distributed 5G deployments.