## 4 Results
### Configuration of the Simulation Environment
#### 4.2.3 Configuration of DSRC  
First, we set the Wi-Fi standard to IEEE 802.11p and the remote station to constant rate Wi-Fi manager, in order to set up the Wi-Fi class accessible in NS3 using DSRC variables. In vehicular communication, the Media Access Control (MAC) layer was set as Ad Hoc Wi-Fi with Quality of Service (QoS) support because there were no designated access points or user equipment. The Minimum Contention Window (\(CW_{min}\)) and Maximum Contention Window (\(CW_{max}\)) were set to 15 and 1031, respectively. The maximum number of retransmission attempts (\(E\)) for packets whose size was greater than the RTS-CTS threshold was set to 6, in order to utilize all transmission attempts for the previously specified contention window sizes (\(E=log_{2}(\frac{CW_{max}}{CW_{min}}+1)\)). When packet collisions might happen in high-contention conditions, retransmission attempts are set to the provided value (six, as the packet size is always bigger than the RTS-CTS threshold) in order to enhance the dependability of the DSRC connection. As the packet size is always larger than the RTS-CTS threshold, we configured the Request to Send-Clear to Send (RTS-CTS) level to 10 bytes in order to constantly activate the RTS-CTS flow control mechanism. Note that, before packet transfer, an RTS-CTS handshake is required for packet unicasting, avoiding packet collisions in high-contention scenarios in CSMA-CA. In other words, the CSMA-CA protocol is enhanced by the activation of the RTS-CTS flow control mechanism. We set the DSRC queuing parameters as follows: the maximum delay for keeping a packet in the queue was set to 50 s, and the maximum queue size was set to 500 packets (or 500,000 bytes).  
The highest permissible Equivalent Isotropic Radiated Power (EIRP) at the 5.9 GHz band is 44 dBm, as stated by the Federal Communication Commission (FCC) [77]. Coverage refers to the range of communication that can supply information to nearby vehicles [78]. To meet the coverage standards for urban, non-urban, and autobahn vehicular environments of 139 m, 278 m, and 347 m, respectively [76], the transmission power of DSRC was  
Figure 14: Different mobility scenarios for generating mobility traces for the vehicular network. (**a**) Urban mobility scenario in New York City, USA, (**b**) Non-urban mobility scenario in Pelawatta, Sri Lanka, (**c**) Autobahn mobility scenario in TCH expressway, Canada.  
set to 33 dBm, 41 dBm, and 44 dBm for each scenario. This coverage has been standardized based on the highest relative speed in each mobility scenario [76]. A minimum throughput of 10 Mbps is necessary for the exchange of safety-related driving maneuvers. However, a high data rate is preferred for packet routing in the data plane, as most vehicular network applications require a throughput higher than 10 Mbps [79]. As a result, we selected DSRC channel number 178 with a 10 MHz bandwidth and an Orthogonal Frequency Division Multiple Access (OFDM) data rate of 27 Mbps to satisfy the throughput demand. The Cost-Hata (Cost 231) and Three Log Distance Propagation loss models were chosen for urban [80] and sub-urban/autobahn [81] scenarios, respectively. The constant speed propagation delay model was utilized for signal propagation, while the Nist Error rate model was selected to model different error rates for different OFDM modulations in IEEE 802.11p.