Signal Processing for beyond 5G Non-Terrestrial Networks

Signal processing has been playing an essential role in wireless terrestrial and satellite communications. Terrestrial networks are deploying new 5G based networks in different frequency bands, some of those in the traditional realm of satellite networks, so that flexible mechanisms of sharing and co-existence will become more relevant. At the same time, the advent of new non-terrestrial wireless solutions such as High Altitude Platforms or highly dense Low Earth Orbit (LEO) constellations is positioning non-terrestrial networks (NTN) for a more decisive role in global data provision. However, a real integration between terrestrial and non-terrestrial networks still seems far in the future; the 3rd Generation Partnership Project (3GPP) has concluded some initial studies on the role of NTN in 5G, and a Work Item is expected to finalize in 2021. It is likely that for the years to come, both networks will still remain separate, with a potential real integration given by the timeframe of 6G, where NTN is considered key in providing connectivity to rural and underprivileged areas.
There is a strong need for signal processing R&D in the new NTN, which at the same time helps to close the bridge with terrestrial networks: the farther away we move from the physical layer, the more commonalities can be found between space and terrestrial segments. The sharing of radio frequency bands and the dynamic usage of resources allow to operationally reconfigure network connections. In this context, the signal processing in the transmitters, receivers, and network control systems face significant requirements to access frequency resources dynamically, detect interference, optimize the network configuration, and configure the radio resources operationally. Signal processing must be used to leverage the flexibility of resource allocation in NTN, including GEO, MEO and LEO satellites, aerial platforms and even unmmaned aerial vehicles (UAV).

This Collection has the objective of covering novel contributions with emphasis on signal processing techniques in NTN. Prospective authors are invited to submit original manuscripts on the following topics.
Topics of interest include, but are not limited to:
• Advanced signal processing techniques for non-orthogonal multiple-access
• Trade-offs between performance, latency and complexity for the selection of signal processing algorithms
• Software-Defined Radio (SDR) for PHY&MAC and NTN prototypes
• Signal processing techniques based on big data processing
• Signal processing for IoT over NTN
• Role of signal processing on the integration of satellite, airborne platforms and terrestrial networks
• Signal processing for enabling direct access from NTN to User Equipment
• Signal processing for dynamic configuration of radio resources following the traffic needs *
• Signal processing for dynamic access to the spectrum
• Signal processing for realizing Time Division or Full Duplexing in NTN
• Beam management in NTN
• Signal processing for reconfigurable intelligent surfaces
• Characterization of the land mobile aerial and satellite channel at mmWaves
• On-board signal processing for new satellites and aerial platforms
• On-board gNodeB implementation
• Non-geostationary orbit (NGSO) satellites directly accessing NR-enabled User Equipment (UE) in mmWaves
• Signal processing for NTN physical layer security
• Machine learning methodologies for improving traditional signal processing algorithms
• Signal processing for optical NTN communication