# 5G Beyond 3 GPP Release 15 for Connected Automated Mobility in Cross-Border Contexts
## 5 Conclusions and Open Issues  
In this paper we gave an overview the different 5G features from Release 16 and 17 that will be key to enabling or boosting use cases of the CAM domain, specifically in the context of cross-borders. To this end, we took advanced CAM use cases targeted in 3 GPP documents and put them into the cross-border context to identify further communication requirements. Then, we analysed the roles and relevance of identified 5G features to meet CAM requirements, such as: low-latency roaming to ensure service continuity; multi-radio communications to gain interoperability of cross-border networks; multi-SIM connectivity to increase reliability when crossing a border; NR positioning to enhance localisation accuracy and mitigate localisation errors induced by roaming latency; sidelink to further enable distributed architectures; broadcast modes to efficiently share common data; mmWave to expand radio capacity; network slicing to book resources to ensure QoS; and edge computing to deploy a scalable infrastructure. This paper presents a 5G deployment option for CAM over a terrestrial network inspired by the work done in 5G-MOBIX, where other options like satellite communication are also considered. However, there are some open issues not covered in ongoing discussions and working documents of 3 GPP. Firstly, there is a lack of standard MEC APIs to manage the servicing lifecycle, from release  
Figure 8: Quality of experience scenario of the proposed solution. and deployment to operation and management. In a cross-border context this would mean extra and manual work to deploy a MEC service on a network and migrating or cloning it to another one. Moreover, a seamless MEC handover mechanism is also lacking. The MEC system should have a standard mechanism to transfer the session data to the following MEC node as the devices physically navigate along them, including MEC nodes located in different PLMNs. As shown in Section 3, the latency of the V2X messages is critical. In a cross-border context, the roaming adds even more latency and makes the timely delivery of messages to a set of distributed systems very challenging, complicating a common understanding and creating inconsistencies and conflicts. In Ethernet networks, where there is no roaming at all, this is addressed by applying time-sensitive networking standards that ensure bounded latency instead of a best-effort approach. However, wireless networks behave differently from wired links, due to device mobility and the intrinsic characteristics of the physical layer. This paper already proposes some options to minimise latency problems by using 5G technologies such as slicing, edge computing or mmWave communications. Nevertheless, a standard strategy for resource overprovisioning and traffic congestion prediction and management can help mitigate this problem even more. From the business feasibility perspective, the deployment and exploitation options of 5G in cross-border corridors should be studied further. Several aspects need to be considered for a successful deployment of 5G for CAM, such as the base station and MEC density or the backhaul provision. Cost reduction solutions are also necessary that promote infrastructure sharing, and exploit cooperative models between the automotive industry, mobile network operators, road operators and new players such as cloud or edge service providers. Conceptualization, G.V., A.M., G.P. and E.M.; formal analysis, G.V. and A.M.; investigation, G.V., A.M., G.P. and E.M.; writing--original draft preparation, G.V., A.M., G.P. and E.M.; writing--review and editing, G.V., A.M., G.P. and E.M.; visualization, G.V. and A.M.; supervision, G.V. All authors have read and agreed to the published version of the manuscript. This work is a part of the 5G-MOBIX project. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number 825496.