# Seamless 5G Multi-Hop Connectivity Architecture and Trials for Maritime Applications
## 3 Maritime Network Architecture and Solutions for Seamless Connectivity  
As has been discussed previously, it is important that the vessels are always (best) connected. The need for communication and connectivity increases when a vessel is operating on more crowded or more challenging waters. When a vessel goes to open waters, the requirements for connectivity might decrease. This also sets the scene for maritime clusters, where one solution does not fulfill all the requirements, or it might be too sophisticated or expensive for some cases, while in some environments, it could be a minimum requirement in the future. Hence, in this paper, we studied several different connectivity scenarios, which might supplement each other with the vision presented in the previous section, according to which 5G will become the primary technology for seamless connectivity in the maritime industry in the near future. Terrestrial network connectivity is already used in ports and on ships close to the coast, but in order to ensure seamless connectivity and real-time data exchange, it is necessary to develop the provision of 5G connectivity between ships by creating a 5G multi-hop network, as well as to ensure connectivity with 5G non-terrestrial connectivity in offshore waters. Coverage with 5G is only one aspect of deploying a 5G network at sea level, where the most important thing is to ensure the QoS required for each use case (usually measured via more fundamental KPIs such as latency, throughput, availability, etc.).  
In the following, we will separately discuss the relevant architectures for the maritime multi-hop connectivity scenario. For this purpose, it will be useful to define three types of links (Link A, B and C) among the different elements that are depicted in Figure 4, depending on the geographical nature of the involved communication pairs (sea, land, air/space). Link A covers land (sea communication), Link B addresses sea (sea communication) and Link C relates to communications with the presence of an air/space segment (see Figure 5).  
We first discuss the possible architectural splits between the components on the ships (onboard) and those not on the ships (onshore) related to Link A. Within this discussion, we assume IP network connectivity between the components without discussing how it is realized (all nodes, also known as network functions, forming a mobile radio network are interconnected over internet protocol (IP) connections. This also applies for the interfaces between the RANand the core. Theoretically, any internet connection with endpoints at arbitrary geographic distances could be used, but practically, the requirements regarding latency, reliability, throughput and security need to be fulfilled.). The second discussion focuses on possible realizations of this IP connectivity, starting from single-hop ones and then considering multi-hop, covering Links B and C. Finally, for the case that IP connectivity is realized through an onshore mobile radio network, we discuss how to achieve  
Figure 4: Vision for the high-level solution of the seamless connectivity problem in maritime environments.  
uninterrupted service delivery if ships operate between the shores of different countries and where those countries are served by different mobile network operators (MNOs).