# Wireless Communication Technologies for Safe Cooperative Cyber Physical Systems
## 5 5G Open Challenges  
In this section, the open challenges raised from the architectures of the SafeCOP use cases presented above are discussed in relation to 5G use cases. The reason to choose 5G to discuss about the technical challenges is the fact that 5G system can accommodate (from wireless communications standpoint) most of the SafeCOP use cases as identified from above discussion. Notably, 5G promises to facilitate new vertical industries through network slicing and network softwarization [81]. Our study below proves that 5G communications can facilitate most of the innovative CPS related use cases of SafeCOP project. Safecop had as a major objective to provide cooperative safe CPS using wireless communications technologies and 5G could be considered the most promising candidate solution.  
Work on 5G is currently in progress to meet the 2020 objectives of a ready-to-use technology. The European Union promoted the METIS project in 2012 [82; 83], followed by the 5 GPP program [84], as well as other significant projects like e.g., CROWD [85]. The NGMN Alliance, which was founded by major mobile operators in 2006, provided an important contribution to 5G by publishing the NGMN 5G White Paper in March 2015 [86].  
As the future cellular network's evolution, the 5G ecosystem is a multi-provider/multi-tenant environment. It is designed as a heterogeneous network supporting business and applications services [87]. It is structured in a set of layers divided into two basic groups:  
1. _The higher service-centric layers_ modeling the business implementations driven by the vertical use cases.
2. _The lower network-centric layers_ representing the physical implementation and its abstraction based on software network technologies like software defined networking (SDN) and Network Function Virtualization (NFV).  
The 5G protocol stack is based on IPv6, as defined in [88; 89; 90]. Network flexibility is obtained by the establishment of slices, configured for the purposes of specific application scenarios. Slicing allows the creation of multiple virtual networks on top of a shared physical infrastructure. They allow specific operators to offer ITS related services, ensuring the right prioritisation of communication channels (e.g., road monitoring for safety over other INTERNET traffic). Additional issues are network coverage and densification, where the latter consists in adding more cell sites to increase the available network capacity. Device-to-Device communications and the concept of virtual cells contribute to addressing both issues.  
As 5G is designed according to specialized application requirements, its applicability to the SafeCOP use cases should be accurately discussed.  
For the maritime use case, the radio high frequency transmission could suffer from hard degradation and interferences due to water surface and possible adverse weather conditions, challenging the use of 5G technology. Satellite communication is still possible, but latency and response time are generally not acceptable except for critical situations as a backup solution.  
In case of a healthcare use case, the currently foreseen protocols like 802.15.4 and 802.11 are very suitable for indoor and intra-robot communications. 5G can be considered exploiting the \"femtocell\" indoor solution and integrating the system to a wider infrastructure for possible future expansion or effective service distribution.  
The set of automotive use cases will take a great advantage by 5G evolution, since the research and improvement area of 5G aim to solve the limitations of current mobile and Ethernet-based technologies (i.e., LTE Proximity Service and 802.11p) [91; 92; 93; 94].  
Table 1 summarizes the 4G and 5G technology challenges related to SafeCOP use cases. We then outline how 5G standards may meet SafeCOP requirements and the open challenges ahead.