# Review of Communication Technologies for Electric Vehicle Charging Management and Coordination
## 7 Communication in EV Charging Coordination
### DSRC in Charging Coordination  
The authors in [72] adopt DSRC to facilitate the communication between EVs and charging stations, and to enable gathering and dissemination of information in a real-time manner using centralized coordination. The current status of the power system and real-time information of the EVs are all transmitted to a traffic server through multi-hop V2V communication. Then, the traffic sever executes an optimal charging strategy that maximizes the charging energy while minimizing the traveling cost and avoiding system overloading. Finally, charging decisions are forwarded to the EVs through the RSUs or neighboring EVs.  
Another centralized coordination scheme based on DSRC is proposed by the authors in [128], aiming to minimize the total trip time considering traffic conditions. When the battery level is below a predefined threshold, an EV sends a service request to the RSU, including message ID, SoC, vehicle ID, and the current location. Afterwards, the optimal CS selection algorithm that selects the CS with the shortest service time is performed by an electro-mobility management server (EMMS), and responds to the EV by sending a service response message providing information about the selected station. Instead of single-hop communication, the authors adopted a multihop multimetric routing scheme for more efficient charging management to forward charge requests and reservation messages between EVs and EMMS. This scheme selects the next forwarding node with five metrics: distance to destination, vehicle density, vehicle trajectory, MAC losses, and available bandwidth. The forwarding scheme reduces the packet losses and the average packet delay.  
The authors in [129] propose a communication framework based on DSRC for gathering real-time information about parking situations, reservations of mobile EVs, and V2V charging/discharging matching decisions. They enable relay nodes to achieve efficient wireless connection by means of V2V communications. The authors also introduce a semi-distributed coordinated charging system in which each EV decides the best charging/discharging place, while a central device performs optimal EV pair assignment. Hence, in comparison with fully centralized and fully distributed charging management schemes, a semi-centralized scheme can reduce communication congestion and computational complexity while preserving EV user privacy, improving scalability and robustness of charging, and achieving global V2V charging optimization.  
The authors in [130,131] also studied the use of DSRC networks in demand-side management (DSM) for wireless dynamic charging to guarantee the balance between the total demand and supply. Communication between the EV and the charging infrastructure is required to exchange information such as a congestion signal, pricing information, and charging profile. DSRC is implemented to enable information exchange, where the RSU is placed in the middle of the charging lane, and sends a congestion signal to EVs indicating that the charging demand exceeds the supply to reduce the charging rate.