# Seamless 5G Multi-Hop Connectivity Architecture and Trials for Maritime Applications
## 1 Introduction
Many, but not all, findings for wireless access backhauls and split options are relevant for the maritime scenario evaluated in this paper. Inspired by these related works, Section 3 contains an analysis of the applicable options for multi-hop maritime scenarios. None of the works cited previously included aspects related to the deployment, testing and trialing of actual mobile networks endowed with a satellite component and multi-hop technology in maritime environments, which was the focus of this paper and one of the main goals of the 5G-ROUTES project. The 5G-ROUTES project is funded by the European Union's Horizon 2020 research and innovation program under the auspices of the European 5G Action Plan [23]. The European 5G Action Plan addresses the need for high-data-rate connectivity everywhere and all the time with a specific focus on the mobility vertical, encompassing all modes of transportation--land (both road and rail) and, especially important for this paper, sea or in the motorways of the sea. The overall objective of the 5G-ROUTES project is to conduct advanced field trials of some representative and innovative connected and automated mobility (CAM) applications,seamlessly functioning across a designated 5G cross-border corridor ('Via Baltic-North'), traversing Finland, Estonia and Latvia, in order to validate features and 3 GPP specifications under realistic conditions so as to accelerate the widespread deployment of 5G end-to-end interoperable CAM ecosystems and services in digitized motorways, railways and shipways throughout Europe. For this purpose, a number of use cases have been identified, some of which address multi-modal transport, and these scenarios considered for trialing are described in the next paragraph. Among the use cases defined in the 5G-ROUTES project in [24], four specific use cases focus on the quality and coverage of connectivity services. Two of these use cases focus on passenger transport services, one focuses on supply chain and freight transparency in multimodal transportation, and one focuses on smart ferries/vessels themselves. The aim of these different use cases is to study and pilot uses cases targeted for different customer groups in maritime transportation. The target is also to combine road and maritime transportation and to aim for continuous multimodal service, tracking and transparency availability. The use cases within the 5G-ROUTES project focus on two different themes. In the first theme, the use cases focus on network availability and coverage and how to improve the current services. The second theme focuses on network quality, e.g., latencies, throughput rates and download speeds. To end this introduction section, we provide a summary of the main novel contributions of this paper and describe how it is structured in the different sections according to our proposed approach and methodology. The main contributions of this paper are:  
* To conduct and present the results of a measurement campaign of 5G coverage at 3.5 GHz and 700 MHz to assess the (poor) mobile coverage in ferries for maritime scenarios. * To propose different architectural solutions to provide a seamless 5G service connectivity to sea ferries operating across country borders, capitalizing on multi-hop and satellite technologies and to discuss on their pros and cons. * To analyze and describe in detail the planned field trials that will take place to validate the architectural solutions, including selected KPIs, to quantitatively assess the performance of the proposed solution and the selected building blocks for the implementation of the end-to-end system. In particular, the present paper is organized as follows. First, Section 2 provides a description of the maritime scenario considered in this paper and, based on the results of the measurement campaign on the maritime coverage referred to above, states the main problem at hand, i.e., that of providing seamless connectivity for maritime applications.