## 4 Performance Evaluation of Millimeter-Wave V2V  
### Millimeter-Wave V2V Communications with Antenna Height Diversity  
In the current V2X (Vehicle-to-Everything) communication system, DSRC (Dedicated Short-Range Communication) is the most popular V2X communication system. It is natively designed to support communication with high-speed vehicles. However, since it uses 5.8 or 5.9 GHz, which provides a several Mbps transmission rate, it has difficulty supporting cooperative perception. Moreover, when the density of vehicles becomes high, the performance becomes rapidly degraded due to CSMA/CA. On the other hand, C-V2X (Cellular-V2X) was developed by 3 GPP (3 rd-Generation Partnership Project) to enhance ITS (Intelligent Transport Systems) and support automated driving. The main characteristics of C-V2X are that the Uu and PC5 interfaces are prepared for different use cases. When a user wants to access infrastructure such as an application server, the Uu interface is used. The PC5 interface is prepared for direct communications between the users. This direct communication can be utilized for cooperative perception. Although the C-V2X function of scheduling can avoid communication collision, the data rate of PC5 is not enough for cooperative perception due to it using 5.9 GHz [29]. As introduced above, the conventional V2X communications are not suitable for cooperative perception in terms of the data rate. Therefore, new V2X communication systems such as IEEE 802.11 bd and NR-V2X (New Radio-V2X) are currently under development. Both IEEE 802.11 bd and NR-V2X plan to include millimeter-wave communications to support sending high-resolution 3D maps [30]. This use case can be realized by millimeter-wave communications, which provide high throughput. However, millimeter-wave has a greater path loss and is more easily blocked than the frequency used in conventional V2X \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**LiDAR Parameters**} \\ \hline
**Parameter** & **Value** \\ \hline Location & Vehicle’s roof +20 cm \\ Range & 200 m \\ Elevation Angle Range & \(\pm 15^{\circ}\) \\ Elevation Angle Resolution (\(r_{\phi}\)) & \([0.2^{\circ},\ 0.1^{\circ},\ 0.08^{\circ},\) \\  & \(0.06^{\circ},\ 0.04^{\circ},\ 0.02^{\circ}]\) \\ Azimuth Angle Range & 180\({}^{\circ}\) \\ Azimuth Angle Resolution (\(r_{\theta}\)) & \([0.2^{\circ},\ 0.1^{\circ},\ 0.08^{\circ},\) \\  & \(0.06^{\circ},\ 0.04^{\circ},\ 0.02^{\circ}]\) \\ Non-Linear Spacing & dense spacing (\(-7.5^{\circ}\)–\(7.5^{\circ}\)) \\  & sparse spacing (otherwise) \\ Return Mode & Strongest \\ Scan Period & 20 Hz \\ Data Size of One Point & \(16\) bit (coordinate) \\  & \(+12\) bit (power) \\ \hline \multicolumn{2}{c}{**V2V System Parameters in the [5, 30, 60] GHz Bands**} \\ \hline
**Parameter** & **Value** \\ \hline Height of Tx(\(h_{t}\)) & 38 cm \\ Height of Rx1(\(h_{t1}\)) & 38 cm \\ Height of Rx2(\(h_{t2}\)) & [98, 48, 43] cm \\ Height of Rx3(\(h_{t3}\)) & [182, 50, 5] cm \\ Transmitted Power & 10 dBm \\ Boresight Gain & [4.3, 20, 26] dB \\ Antenna Aperture Size & 2.6 cm \(\times\) 2.6 cm \\ Polarization & vertical \\ Vertical Antenna Vibration Model & Gaussian(\(\sigma=\)3.2 cm) \\ Bandwidth & [10, 500, 1000] MHz \\ Antenna Diversity & selection diversity \\ Noise Figure & 10 dB \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters. communications. To compensate for these defects, strong directivity and ensuring LoS are necessary. From a different point of view, these defects can be advantages for spatial re-usability. In other words, blockage effects and strong directivity reduce interference to surrounding vehicles [31]. In this paper, we compared the outage capacity of millimeter-wave communication and conventional communication and estimated how much this contributed to safe driving. In this paragraph, the V2V (Vehicle-to-Vehicle) channel model for moving vehicles is introduced. In [32; 33], the authors measured 5 and 60 GHz and performed modeling of the measured data.