# Authentication and Billing for Dynamic Wireless EV Charging in an Internet of Electric Vehicles
###### Abstract
This energy can also be wirelessly exchanged between traveling vehicles, using direct vehicle-to-vehicle (V2V) wireless energy transfer, given effective coordination and alignment between the EVs [13; 14]. With the increasing penetration of EVs and the corresponding advantages and drawbacks of the different charging systems, these systems need to be integrated and collectively utilized within the city infrastructure to address the increasing demand for EV charging facilities. This requires effective energy management and coordination to avoid grid disturbance and overload from unregulated and/or unscheduled charging [15; 16; 17]. Accordingly, a network of electric vehicles, also referred to as the Internet of EVs (IoEV), needs to be established, in which EVs can communicate and exchange information securely with one another and with the surrounding infrastructure and the power grid, to enable charging coordination, effective energy management, grid load balancing and traffic optimization [18; 19; 20]. Hence, an IoEV consists of the different EVs and the corresponding charging infrastructure, including plug-in charging stations, static and dynamic wireless charging units and vehicle-to-vehicle (V2V) energy exchange facilities. These are shown in Figure 1.  
Figure 1: Overview of EV charging solutions in an Internet of Electric Vehicles (IoEV) [21]. The concept of an IoEV leverages on the capabilities of vehicular ad hoc networks (VANETs) by defining each EV as an intelligent entity that communicates with other surrounding entities using V2X communications, to ultimately establish a framework for reliable EV charging coordination and effective demand management. Accordingly, the key requirements of V2X communications in an IoEV are high-speed communications, ultra-low latency and ultra-high reliability, particularly for DWC systems due to their relatively short charging durations compared with static charging [21; 22; 23]. Different V2X communication technologies are addressed in the literature, including Dedicated Short Range Communication (DSRC), cellular-V2X (C-V2X) and 5G-V2X communications [24; 25], each of which offers different features to address the different requirements for effective EV communication and coordination in an IoEV [21]. A heterogeneous network integrating the different radio access technologies (RATs) with other 5G advanced technologies such as MIMO, mmWaves and D2D communications, further improves the capabilities of vehicular communications in an IoEV and helps satisfy the requirements of the different use cases in terms of throughput, reliability, latency, security and quality-of-service (QoS). In addition to effective vehicular communications, accurate authentication algorithms with fair and efficient billing schemes are essential to establish effective EV charging coordination and demand management strategies. This is because, whether the coordination strategy is implemented using game theory as in [26; 27] or fuzzy logic inferences as in [17; 28; 29], accurate user authorization is crucial to ensure reliable scheduling of the charging resources among the EVs demanding energy, while ensuring protection against free riders and other unauthorized drivers. Fair billing, on the other hand, maximizes EV drivers' satisfaction and motivates their participation in EV charging coordination programs. The effective operation of these programs ultimately helps reduce power network congestion and overloading, and ensures grid load balancing between the different charging points [30; 31]. Nevertheless, the implementation of effective authentication and billing schemes for dynamically charged EVs is a challenging task. This is mainly due to the continuously varying charging rate during the vehicle's motion and the charging \"handover\" from one charging pad to another. In addition, the fast EV traveling speeds impose the need for low latency communications, and fast authentication protocols to guarantee accurate billing during the EV motion over the charging lanes.