Satellites enable the provision of global 5G coverage utilizing a customized protocol stack for direct access of 5G devices. This paper reports the results of a field trial based on an Open Source Software (OSS) 5G protocol stack modified for Satellite Communications. 5G New Radio (NR) functions have been adapted to support 3GPP Non-Terrestrial Networks (NTN) standardization for Release 17. Some of the currently discussed enhancements for 5G New Radio (NR) direct access for NTNs were evaluated in this study utilizing a geosynchronous satellite system. Non-Terrestrial Networks (NTN) devices and base station were software-defined solutions communicating via satellite through a standardized 5G NR waveform. The results show that Open Source Software (OSS) implementations running on general purpose platforms greatly support the research and standardization process for 5G-Beyond NTNs. New functions related to NTNs can be evaluated at an early stage over channel emulators or real world satellites to highlight the capabilities of space based 5G-Beyond networks. Therefore, OSS can be a starting point to turn the vision of 6G protocols on-board the satellite into reality.

Summary: A secure and flexible communication infrastructure for the use of broadband and IP‐based services is becoming more and more important in the context of Public Protection and Disaster Relief (PPDR). Government agencies and emergency responders need to be able to react quickly to emergencies across the globe. In particular, satellite‐based 5G mobile networks can support government agencies during their critical tasks. To support the standardization committees and the industry, it is required to evaluate new architectures for such networks by utilizing testbeds and field trials. In this article, we propose and investigate architectures for mobile PPDR networks with satellite backhaul to ensure Communication on‐the‐Move. The flexibility within the architectures comes with the distribution of the core network nodes at the edge of the network applying the Core‐Edge Split concept. The presented results show that already existing interfaces of the Evolved Packet Core 3GPP standard allow satellite‐based 5G networks tailored to the needs of government authorities.

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.

The 3rd Generation Partnership Project (3GPP) aims to integrate non-terrestrial networks (NTNs) with terrestrial 5G networks. In this context, prototyping and testing are essential to demonstrate the readiness of new 5G-NTN releases. However, commercial 5G protocol stack implementations are usually costly and closed solutions, which makes it challenging for universities and nonprofit research institutions to adapt and customize them for 5G-NTN testing and development purposes. Software-defined radio testbeds that utilize open-source software implementations are an attractive alternative. In this article, we describe our protocol stack adaptation of an open-source implementation for 5G-NTN based on OpenAirInterface (OAI), which runs on commodity hardware. We evaluate the performance of our 5G-NTN in various layers in real-world environments with a transparent geostationary satellite. We validate our testbed with a variety of Internet applications. These include streaming video, web browsing, and voice over IP. The results indicate that the current implementation utilizing the 5MHz bandwidth is reliable over several hours and achieves both downlink and uplink speeds of 3.6Mb/s while maintaining a typical geostationary latency of approximately 530 ms. The tests demonstrate that our 5G-NTN testbed is an reliable alternative to costly commercial implementations.

Visibility and communication are the essential pillars for safe flight operations in dense airspaces. Small Unmanned Aerial Vehicles (UAVs) of the order of up to 25 kg are increasingly being used at airports as a cost-effective alternative for maintenance and calibration work. However, the joint operation of manned and unmanned aircraft in busy airspaces poses a major challenge. Due to the small diameter of such UAVs, the established principle of “see and avoid” is difficult or even impossible to implement, especially during take-off and landing. For this reason, a certified Mode A/C/S transponder supporting ADS-B was extended with an embedded system and a cellular interface to realize a Multi-Mode-Transceiver (MMT). Integrated into a UAV, the MMT can provide aircraft visibility in the context of traditional manned Air Traffic Management (ATM) and future UAS Traffic Management (UTM) at the same time. This multimodal communication approach was investigated in flight test campaigns with two commercially available UAS that were connected to an experimental UTM with a simulated controlled airspace. The results confirm the safety gain of the multimodal cooperative approach. Furthermore, the collaborative interface with ATC enables the digital transmission of transponder codes, entry clearances and emergency procedures without the need for a voice radio communication. However, the parallel operation of both radio technologies in a confined space requires modifications to the transmission power and alignment of the radio antennas to avoid mutual interference. Furthermore, different reference planes of barometric altitude measurement in manned and unmanned aviation pose additional challenges that need to be addressed.