Toward Multi-Connectivity in Beyond 5G Non-Terrestrial Networks: Challenges and Possible Solutions

TL;DR

Challenges related to multi-connectivity in NTNs are discussed, and solutions to the identified challenges are proposed.

Abstract

Non-terrestrial networks (NTNs) will complement terrestrial networks (TNs) in 5G and beyond, which can be attributed to recent deployment and standardization activities. Maximizing the efficiency of NTN communications is critical to unlock its full potential and reap its numerous benefits. One method to make communications more efficient is by the usage of multi-connectivity (MC), which allows a user to connect to multiple base stations simultaneously. It is standardized and widely used for TNs, but for MC to be used in the NTN environment, several challenges must be overcome. In this article, challenges related to MC in NTNs are discussed, and solutions to the identified challenges are proposed.

Figures (2)

• Figure 1: illustrated in the environment. The figure shows the related protocol stacks, where changes to the ’s architecture can be seen: the must be able to receive transmissions from multiple sources, namely the and in the downlink direction, and similarly, to transmit to these different nodes when uplink is considered. A transparent payload architecture is considered, so the service and feeder links use the Nr-Uu interface. The and are connected via the Xn interface for the exchange of control plane and user plane data. The is connected to the via the Ng interface. Adapted from 10195478.
• Figure 2: a) Quasi-earth fixed and b) earth-moving beam deployments. Frequency reuse 3 is considered where adjacent beams operate at different frequencies corresponding to the different colors to mitigate inter-cell interference. The figure shows the difference in the beam deployments as the satellite moves in space from its initial position between times $t_1$ and $t_2$.