# Review of Communication Technologies for Electric Vehicle Charging Management and Coordination
## 2 Vehicular Radio Access Technologies  
Different technologies have been proposed in the literature to support communication between EVs and the different elements of the infrastructure [30]. Direct wired commu  
Figure 1: Overview of EV charging solutions in an IoEV within a smart city infrastructure. nication and message exchange between the EVs and EVSEs are currently established based on the IEC 61850 and ISO/IEC 15118 standards [23; 30]. In addition, high-speed broadband communications over low-voltage power lines are reported in [31; 32], in which the same charging cable is utilized to simultaneously carry communications signals along with the charging power. This power line communication (PLC) system demonstrated a theoretical maximum data rate of 14 Mbps which is significantly higher than the 100 kbps required bandwidth estimated by the US Department of Energy for enabling at-home EV charging [26]. Nevertheless, while wired communication solutions offer high security, high reliability, and a sufficiently high data rate, they can only be utilized for plug-in and static wireless charging systems. They cannot, however, be used for DWC systems due to the mobility of the EVs. Furthermore, low data rate and short-range wireless communication systems such as Bluetooth and ZigBee can also support vehicular communications in wired and static wireless charging [33; 34; 35], but are not appropriate for dynamic charging. This is because, in dynamic charging, micro-charging sessions that last for just a few milliseconds are required, thereby demanding an ultra-low latency solution. Hence, low-latency, high-reliability, and wide-range wireless communication technologies need to be utilized for V2I, I2V, and V2V communications during dynamic wireless EV charging. A detailed review of, and comparison between, the potential of different wireless communication technologies for EV charging management is presented in this work. Vehicular communication solutions are inevitable enablers for wireless EV charging system management as they enable the information exchange required for charge scheduling, coordination, vehicle routing, authentication, and billing. For instance, an EV requesting the charging service has to send a charging request with the EV information including EV speed, current location, destination, maximum battery capacity, initial SoC and desired final SoC. Charging reservation information is also exchanged together with periodic real-time updates on arrival time, expected charging time and location, and charging prices. A sample message exchange sequence for charging coordination and reservation between EVs and a stationary charging station (CS) through a global aggregator (GA) is presented in [36], as shown in Figure 2.  
Figure 2: A sample message exchange sequence for an EV charging coordination and reservation system. ©2021 IEEE. Reprinted, with permission, from [36]. As observed in Figure 2, wireless communication technologies, in this case cellular networks and Wi-Fi communications, are required to enable information exchange between the EVs requesting charge and the charging infrastructure. The choice of the most suitable communication channel and radio interface impacts the speed, security and reliability of the coordination of the charging process. The performance requirements for a vehicular radio access network to be suitable for EV charging management can be summarized as follows:  
* **Latency**: While the end-to-end communication latency requirement for at-home static EV charging is estimated by the US Department of Energy to be around 2 s [26], this value needs to be significantly smaller for dynamic charging, although a specific reference value is not yet defined by the standards. Dynamic wireless EV charging is a time-sensitive, delay-intolerant service given the short lane-crossing duration at typical EV driving speeds [12]. Moreover, vehicular communication networks need to include congestion detection and prevention mechanisms to avoid undesirable delays [37].