## 3 Required Data Rate in V2V for Safe Overtaking
### Cooperative Perception and Scenario Description
IEEE 802.11p is designed to reduce the latency in V2V communications and consists of two main features. Firstly, it does not require the establishment of a basic service set. Secondly, CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) is adopted to avoid collision due to simultaneous access. However, the usage of the CSMA/CA mechanism degrades the performance in high traffic density areas mainly due to frequent simultaneous access and many hidden nodes [18]. The other option is LTE (Long-Term Evolution) V2V services. From Release 14, LTE has started to support V2V communications. It has a PCsinterface for direct communications and a Uuinterface for long-range cellular network communications. The main advantage of LTE V2V is that it can reuse the same technology for cellular communications. Therefore, we can directly use the already deployed hardware such as base stations. Furthermore, the provided capacity is higher than IEEE 802.11p. However, as the performance of DSRC (Dedicated Short-Range Communication) degrades in high traffic density, the performance of C-V2X also degrades. Currently, not only conventional V2V communications, but also millimeter-wave communications are expected to be used for cooperative perception. In [19], the authors experimented with cooperative perception without using millimeter-wave communications. Although a 2D LiDAR sensor, which generates fewer data points than a 3D LiDAR sensor, was used in the experiment, position estimation errors were still caused, especially for a high vehicle velocity. This suggests that conventional V2V communications are not sufficient to share HD 3D sensor data. Furthermore, applications for automated driving such as machine learning prefer raw sensor data to compressed sensor data, which leads to requiring a very high data rate [20]. These problems can be solved by using millimeter-wave communications, which provide a high data rate. For example, IEEE 802.11 ad has a more than 8 GHz continuous band in four channels, which provides a large channel capacity to transmit sensor data. In [8], as shown in the related works, the requirement for the transmission of raw sensor data rate was estimated as 1 Gb/s. Therefore, we compared the realized safety between conventional and millimeter-wave communications. Using V2V communications and high-speed information processing technology, automated vehicles are expected to improve traffic efficiency and safety in various driving scenarios. Since considering all driving scenarios makes the analysis complicated, we focused on a driving scenario on a two-lane road where head-on collisions often occur. One of the driving maneuvers on a two-lane road is overtaking. In [21], an overtaking maneuver was included in tactical and operational maneuvers of ADS (Automated DrivingSystems), and many Level 4 automated vehicles have the feature of an overtaking maneuver. This fact indicates that, although an overtaking maneuver is riskier than following the leading vehicle, it is necessary to improve traffic flow and shorten the trip time. In human driving, overtaking at a high velocity is very dangerous especially on a road without a lane separator for the oncoming traffic like on a highway. A human driver is trained to slow down to make space behind the leading vehicle and then try to obtain a clear view of traffic to observe the curvature of the road and closer to the center of the neighbor lane. Once the road ahead is considered safe for overtaking, the driver accelerates and starts the maneuver. With traffic information beyond the limitations of a human FOV from a driver seat, automated vehicles with V2V communication are expected to overtake with less acceleration and deceleration at a high velocity. To realize safe overtaking, we assumed an overtaking scenario on a two-lane road, as illustrated in Figure 2, and estimated the amount of generated sensor data. This scenario focused on a transition period in which both automated vehicles and human-driven vehicles drive on the road, which limits cooperating vehicles.