5G World Forum 2020 - Workshop on Satellite and Non-Terrestrial Networks for 5G

Welcome to the 2020 5G World Forum. Here's an  Introduction to the Workshop on Satellite and Non-Terrestrial Networks for 5G with  Andreas Knopp (2020 Workshop on Satellite and Non-Terrestrial Networks for 5G Chair)

The evolution of 5G into beyond 5G and 6G networks aims at responding to the increasing need of our society of ubiquitous and continuous connectivity services in all areas of our life: from education to finance, from politics to health, from entertainment to environment protection. The next generation network communication infrastructure is called to support this increasing demand of connectivity by enforcing: energy- and cost efficiency to guarantee environmental and economical sustainability; scalability, flexibility, and adaptability to ensure support to the heterogeneity of the service characteristics and constraints, as well as the variety of equipment; reliability and dependability to fulfil its role of critical infrastructure able to provide global connectivity no matter the social, political, or environmental situation. In this framework, non-terrestrial networks (NTN) are recognized to play a crucial role. It is in fact generally understood that the terrestrial network alone cannot provide the flexibility, scalability, adaptability, and coverage required to meet the above requirements, and the integration of the NTN component is a key enabler. In this framework, 3GPP has started to address the inclusion of technology enablers in the NR standard to support NTN. However, to fully exploit the potential of the NT component in an integrated terrestrial and NT architecture, several research and innovation challenges shall be addressed. In this presentation, authors first discuss the current development of NTN in 5G and then present the vision of the role of NTN in B5G and 6G networks and elaborate the corresponding research challenges.

 Doppler frequency is a major channel impairment in mobile SATCOM receivers and LEO digital receivers. Due to its random nature, efficient Doppler frequency estimation and tracking algorithms is presented in this talk. Since computational resources especially on space-born platforms is costly, this presentation shows how to implement Doppler frequency tracking with a minimum logic on FPGA or ASIC-based digital receivers. Authors show that Doppler frequency tracking is possible even with limited logic resources where only ADD, MULT and SHIFT operations could be used.

Satellite systems will play an important role in the coming fifth generation (5G) of mobile communications. For a smooth integration of satellite networks into the terrestrial ones, the standardization bodies are pushing for shared spectrum. Therefore, it is of interest to study the applicability of multicarrier waveforms that have already shown promise to meet the requirements of the future mobile networks in the context of satellite specific scenarios. 5G candidate waveforms such as filtered orthogonal frequency division multiplexing (f-OFDM), filter bank multicarrier (FBMC), and universal filtered multicarrier (UFMC) offer sharper out-of-band characteristics, significantly increasing the spectral efficiency. However, like OFDM, these waveforms exhibit a high peak-to-average-power ratio (PAPR). A high PAPR saturates the non-linear high-power amplifier (HPA) causing non-linear distortions in the on-board HPA’s output. Moreover, signal clipping is often proposed in the literature to reduce the PAPR. However, clipping itself introduces non-linear distortions within the signal bandwidth. Digital predistortion (DPD) can be applied to the clipped signal to remove the added non-linear distortions while keeping the overall PAPR low. This talk provides the simulation results on the application of the aforementioned waveforms to a satellite communication chain, and presents the gains achieved by implementing DPD and clipping together in terms of PAPR, power spectral densities (PSDs) and bit error rates (BERs).

In multiuser multiple-input multiple-output (MU-MIMO) systems for beyond-5G, many user groups are served by the same transmitter in a time-based scheduling. Considering all unscheduled users as eavesdroppers puts a high complexity on algorithms to achieve physical layer security (PLS). Moreover, due to the Line-of-Sight channel properties, PLS is even more challenging to achieve in satellite communication (SATCOM) downlinks. In multibeam MU-MIMO satellite systems, which will be part of beyond-5G networks, the spatial degrees of freedom can be used for both throughput and secrecy improvements. Authors extend a user-fairness zero-forcing algorithm with artificial noise to achieve secure precoding even if the channel state information of the eavesdroppers is unknown. Authors define the secrecy outage probability for Line-of-Sight MU-MIMO SATCOM channels and analyze how it can be reduced by the aforementioned algorithm. Moreover, authors introduce a trade-off between a high system throughput and a low secrecy outage probability for the cost-effectiveness considerations of PLS.

This presentation focuses on the data rate that a High Throughput Satellite (HTS) system with fully regenerative payload can achieve when using an intensity modulation/direct detection optical feeder link. A low-order Pulse Amplitude Modulation (M-PAM) with time-packing is used to modulate the intensity of the laser diode beam, making use of an external Mach-Zehnder modulator. These M-PAM symbols are recovered on-board the satellite with the aid of a photodetector and are then encapsulated into the 5G radio frame of the access link. The M-PAM modulation order and the overlapping factor of time packing are jointly selected to tackle the impact of slowly-varying weather conditions. Moreover, the inter-symbol interference that time-packing introduces is mitigated in reception using a Viterbi equalizer. As expected, time-packing enables a finer granularity on the link adaptation capability of the optical feeder link, enabling to adjust its spectral efficiency according to the moderate attenuation that thin cloud layers introduce.