# Evaluating V2X-Based Vehicle Control under Unreliable Network Conditions, Focusing on Safety Risk
## 3 Methodology
### Communication Model  
This section serves as one of the core areas of our research, aimed at facilitating wireless communication between vehicles. For the simulation, we created a basic message frame that contains the most relevant parameters, including global positions, velocities, angular velocities, and the roll, pitch, and yaw values. Additionally, the created frame starts with the actor ID and timestamp with three additional spaces for other parameters at the end of the message structure. These 18 parameters are converted to 16-bit integers. With regard to bit size, this corresponds to the size of a basic container field in a Cooperative Awareness Message (CAM), where these vehicle parameters are stored [21]. In the initial stages of our investigation, it is essential to determine the methodology for computing and adjusting the SNR value. Throughout the simulation, we maintained the transmission power (\(P_{T}\)) at a constant value of 23 dBm, a standard setting for DSRC communication. As one of the objectives of this investigation is to assess the impact of packet loss on a proposed control, it is essential to determine the receiving power (\(P_{R}\)) in accordance with Equation (2). \[P_{R}=P_{T}-FSPL-X_{\sigma} \tag{2}\]  
\[FSPL=10\cdot log_{10}\bigg{(}\frac{4\cdot\pi\cdot d\cdot f_{c}}{c}\bigg{)}^{2} \tag{3}\]  
The free space path loss (FSPL) is a simplified method for simulating the message power attenuation between the transmitting and receiving sides. In Equation (3), we consider the distance between two antennas (\(d\)), the carrier frequency (\(f_{c}\)), and the speed of light (\(c\)). In this research, we employed the single-slope model. According to other measurements, the difference in a double-slope model was minor [22]. Shadowing (\(X_{\sigma}\)) uses a log-normal random distribution with a mean value of zero. For our research, we  
Figure 2: Simulation environment. used 3.7 dB for a standard deviation based on [22]. Once we determined the receiving power, we can calculate the SNR of the communication (see Equation (4)). \[SNR=P_{R}-N_{0} \tag{4}\]  
\[N_{0}=N_{thermal}+N_{other} \tag{5}\]  
The performance of background noise (\(N_{0}\)) can be affected by a number of factors, including ambient noise and radio frequency interference. In the present simulation, thermal noise was employed as the principal noise source, and its value was calculated according to Equation (6). \[N_{thermal}\ [\text{dB}]=10\cdot log_{10}(1000\cdot B\cdot T\cdot k) \tag{6}\]  
For our simulation, we considered the 10 MHz bandwidth (\(B\)), which is dedicated to DSRC communication, and an ideal temperature of 297 K (\(T\)). The last element of Equation (6) is the Boltzmann constant (\(k\)). This allows us to calculate the SNR value by subtracting the noise from the received power. In our study, we wanted to simulate a degraded network, which we were able to perform with a varying SNR value. For this, we considered additional noise (\(N_{other}\)) values that would establish a degraded network (Equation (5)). In the second stage of the process, the created message must undergo a complex series of transformations before reaching the host vehicle (HV). Our approach was to follow the IEEE 802.11p standard to set up the physical layer of DSRC communication in Simulink, as shown in Figure 3.  
Once the required data have been converted into bits, forward error correction (FEC) is applied to the bit stream, depending on the selected modulation. In our work, we have selected four standard modulations [23] in order to investigate the effect of different  
Figure 3: Bit stream way throughout the physical layer. modulations on the proposed control performance. These modulations can be seen in Table 1 with their working conditions. After FEC coding, interleaving is used to prevent the occurrence of long sequences of adjacent noisy bits. The required modulation is then applied to the bit stream before it is transmitted to the channel.