# Wireless Communication Technologies for Safe Cooperative Cyber Physical Systems
## 3 Communication Technologies for SafeCOP Co-CPSs
### Vehicular Applications  
There are two potential solutions to support V2X communications: Dedicated Short Range Communication (DSRC)/Intelligent Transport Systems (ITS)-G5 and cellular network technologies such as 4G/5G. ITS-G5 generally refers to a wireless technology used for automotive and intelligent transportation system applications via short-range exchange of information among onboard units(OBUs) located inside the vehicles, RSUs placed on the side of the road, or handheld devices carried by pedestrians. Cellular networks provide an off-the-shelf solution for this type of communications. 4G cellular networks is a scheduled network: transmission rates are granted by network scheduler, collisions are avoided and mutual interference is minimized. Quality-of-Service (QoS) can also be guaranteed (e.g., bit rate or delay) by allocating radio resources. On the other hand, some drawbacks that have been recognized (e.g., increased latency in case of high user density, non-optimized channel for small data, unavailability for out of coverage areas, etc.) are addressed by the Proximity Services (ProSe) feature, being specified within 3 GPP [59]. ProSe, similarly to ITS-G5, allows user equipment to discover and communicate with each other directly within communication range, regardless of whether they are in or out of network coverage.The ProSe specifications do not cover the whole V2X requirements (it has been designed with the requirements of public safety and commercial consumer applications in mind). Enhancements are required for high speeds (e.g., in highway scenarios), guaranteed QoS and support for broadcast and unicast communications. 5G will most likely integrate into a heterogeneous network the already available communication technologies like LTE ProSe and IEEE 802.11p and will provide the necessary extensions to enable the future V2X use cases. 5G, as a general objective, will exploit safety, security and privacy support both from the infrastructure and application point of view. From the application point of view, the 5G integrated architecture will allow new business models characterized by services and applications ensemble with an increasing interaction, cooperation and complexity level as well as a great level of flexibility for service tailoring on customer demands. At the infrastructure level, the research aims to satisfy most vertical use case requirements, improving and enhancing the current technologies in an evolutionary scenario, thus solving the foreseen weakness of LTE and ProSe for the vehicular use case. To support the requirements of different vehicular applications, each vehicle must be aware of the position, status and intention of its surrounding vehicles through message broadcasting. The European Telecommunications Standards Institute (ETSI) defines two types of messages: periodic Cooperative Awareness Messages (CAM) [60], and event-triggered Decentralized Environmental Notification Messages (DENM) [61]. CAMs include information such as geographical location, speed, and acceleration, and are only sent to a close neighborhood, as the validity of the information they contain is very limited in time. A large variety of C-ITS based safety applications are built upon the periodic exchange of CAMs, and their timely and reliable transmission is vital as a vehicle that continuously fails to deliver its beacon becomes invisible to its neighbors, which may result in potentially hazardous situations. Based on American standardization, CAMs are periodically generated, while ETSI recently decided upon a set of kinematic CAM triggering rules that trigger beacons when needed rather than keeping it strictly periodic. On the other hand, DENMs are only generated when an event of common interest occurs, and it is spread within an area of interest for the duration of the event. An IEEE 802.11p network contains no access points or base stations, and consequently, will not experience coverage problems. This is the main benefit of IEEE 802.11p compared to other WLAN technologies.