# On the Needs and Requirements Arising from Connected and Automated Driving
## 6 Related Challenges and Existing Research Works
Infrastructure-based links (i.e., Uu) as well as direct V2V links (i.e., sidelink) have different characteristics and, consequently, are associated to different features. The selection of appropriate communication link, the switching from one mode to another, as well as the joint usage are features that will help to improve QoS and communication service availability. In addition, environments with the availability of multiple Radio Access Technologies (RATs) could be also considered, thus extending above challenges when considering that each RAT has its own features in terms of performance, such as reliability, capacity, latency, etc. * **V2X communication is going to take place in a multi-operator environment**: enhancements may be required for dealing with the proper (in terms of delay and reliability) communication of the vehicles belonging to different operators if we want to avoid complex deployments. Additionally, the case of the cross-country border crossing should be considered, where interruptions shall and can be avoided, since the UE should register to the other country's operator. * **V2X service negotiation can enhance the network awareness of service requirements**: for instance, spatial/time information represents important information associated to a V2X service, as well as information about receiver (i.e., vehicle) status, such as its location, speed, intended trajectory, etc. Such information can be exploited by the network to optimize the delivery of the service. On the other hand, the service might benefit from additional information coming from the network, e.g., network capability in fulfilling QoS in a certain area, network capability for message transfer within a certain deadline. As an example, the service can select the most appropriate vehicle driving status (e.g., speed, route), thanks to its increased network awareness. Table 4 summarizes the technical solutions that can be applied to improve the identified challenges and KPIs in terms of capacity, latency, reliability, and positioning accuracy for future autonomous driving. \begin{table}
\begin{tabular}{c c} \hline \hline
**Technology Components** & **Brief Description** \\ \hline \multirow{3}{*}{Multi-antenna techniques} & Predictor antenna, beam management for \\  & unicast/multicast/broadcast communications, and optimal antenna \\  & design for V2X communications including both vehicle and \\  & infrastructure antennas. \\ \hline \multirow{2}{*}{Radio resource allocation and management} & Efficient radio resource management for both Uu and sidelink in \\  & either centralized and/or distributed way. \\ \hline \multirow{2}{*}{Sidelink design} & Basic design for sidelink (discovery, synchronization signal and \\  & reference signal design). \\ \hline \multirow{2}{*}{Full duplex} & Cognitive resource usage for V2V communication and collision \\  & detection/avoidance. \\ \hline \multirow{2}{*}{Reliability enhancements} & Trade-off between reliability, latency and capacity for reliability \\  & enhancement to both data and control channels. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of Technology components. Finally, it is worth mentioning that 3 GPP is working on enhancing the C-V2X technology within the further 3 GPP New Radio (NR) framework [35]. IEEE is, at the same time, working on enhancing 802.11p in the new project P802.11 bd, with the aim to increase throughput, range, and improve procedures for positioning [36]. The main challenges are related to the design of the new V2V broadcast, groupcast, and unicast SL communication interfaces to support the new demanding KPIs, e.g., the high data rate for cooperative perception, high reliability, and latency for remote driving.