# Review of Communication Technologies for Electric Vehicle Charging Management and Coordination
## 7 Communication in EV Charging Coordination  
Charging coordination is a key factor that contributes to the massive adoption of electric vehicles by allowing EV energy demand/supply management and resource allocation. The utilization of the charging energy can be improved by effective coordination of the charging plans. Usually, it is difficult to obtain an optimal charging decisions that satisfies the EV users' demand while achieving load balancing. This is because utility providers aim to maximize their profit under energy constraints, while EV users aim to maximize their received energy and QoS with minimum cost. In addition, minimizing the delay in the information exchange process is essential to ensure that EVs receive the latest scheduling information within the dynamic network changes [114]. Charging coordination strategies can be divided into two main categories: stationary charging coordination and mobility-aware charging coordination. Stationary coordination is mainly concerned with the load balancing of vehicles that are parked at home networks or public parking areas [115] and, hence, the mobility of the vehicle is ignored. Mobility-aware coordination, on the other hand, acknowledges the temporal factor of the EV motion in addition to the spatial and energy factors, by including details of the arrival/departure times to/from the charging points as well as the trip destination and the energy consumption for traveling toward the charging points [36; 116; 117]. This coordination of on-the-move EVs is essential to address EV charging demands to acknowledge both the charging time and the queuing time at the charging stations. It is also crucial in coordinating the motion of EVs toward the nearest wireless charging lane(s) in DWC systems to address urgent demands of EVs with relatively lower SoCs and provide EV drivers with a better quality-of-experience (QoE) [36]. Charging coordination can also be classified into centralized and decentralized coordination [118; 119]. In centralized scheduling for plug-in charging stations (CS), a centralized controller makes charging decisions based on the statuses of the CSs and the EVs, which are received through reliable communication channels [120; 121; 122]. In decentralized/distributed coordination, on the other hand, each vehicle individually selects a suitable charging station based on the available information [123]. For both cases, the information should be efficiently exchanged between the charging stations and the EVs for optimal decisions. Centralized coordination is particularly useful in mobility-aware charging coordination in which EVs need to communicate with the public charging infrastructure to regulate the charging process [36]. For dynamic and quasi-dynamic EV charging systems, centralized mobility-aware scheduling also helps in defining the switching sequences of the charging pads at different charging lane locations to optimize the power transfer process [124]. Nevertheless, while centralized coordination ensures global optimal solutions due to the overall network visibility of the controller, centralized management raises privacy concerns as the participating EVs need to share real-time location updates and other information with the centralized controller for optimum decisions. This highlights the importance of implementing different physical layer security techniques, as described in Section 6, as well as application layer cryptographic techniques [104; 105; 106]. Different charging coordination and routing optimization techniques have been addressed in the literature [72; 117; 122; 125; 126], together with proposals for coordinating the communication and energy exchange with mobile energy disseminators (MEDs) [18; 19]. A semi-distributed V2V charging scheme is also discussed in [92], in which the charging price is determined by a central device, while the charging decisions are made by vehicles.