# The Traffic Adaptive Data Dissemination (TrAD) Protocol for both Urban and Highway Scenarios
## 4 Performance Evaluation
The Friis Free Space Path Loss (FSPL) propagation model is used, in which the exponent \(\alpha\) of FSPL is assigned to 3.0, for the value from 2.7 to 5.0 is estimated for the outdoor shadowed urban environment [33]. According to the setting of propagation model, the radio communication range is about 366 m. For the Bit Error Rate (BER) model of 6 Mbit/s data rate proposed by [PERSON], _et al._ is implemented [34]. We adopt the empirical model of IEEE 802.11p radio shadowing in urban environments proposed by [PERSON] _et al._[35]. For all simulations, the size of data messages is set to the maximum single packet size allowed by the IEEE 802.11p standard (_i.e._, 2312 bytes), because we would like simulate the worst case of the network traffic. To be noted that each source node broadcasts periodically the data message every 2 s. The broadcast frequency could be changed to adapt to the requirements of an application. In this work, we use the same broadcast frequency for evaluating all the investigated protocols in the defined scenarios. Moreover, the size of beacon is set to 378 bytes, where the entry number of message list is set to 40. The beacon sending period is 1 s, and we focus mainly on the simulation of one-hop neighborhood worst case refresh update. The vehicular densities are from 40 \(\mathrm{v}\)/km\({}^{2}\) to 160 \(\mathrm{v}\)/km\({}^{2}\), the interval is 20 \(\mathrm{v}\)/km\({}^{2}\). The simulation setting parameters are summarized in Table 1. \begin{table}
\begin{tabular}{c|c|c} \hline \hline  & Frequency band & 5.89 GHz \\  & Bandwidth & 10 MHz \\  & Tx power & 300 mW \\
**Physical Layer** & Receiver sensitivity & \(-\)100 dBm \\  & FSPL exponent \(\alpha\) & 3.0 \\  & Thermal noise & \(-\)110 dBm \\  & Radio range (Friis) & \(\sim\)366 m \\ \hline  & Bit rate & 6 Mbit/s \\  & CW & [15; 1023] \\
**Link Layer** & Slot time & 13 \(\mathrm{\SIUnitSymbolMicro\second}\) \\  & SIFS & 32 \(\mathrm{\SIUnitSymbolMicro\second}\) \\  & DIFS & 58 \(\mathrm{\SIUnitSymbolMicro\second}\) \\ \hline
**Data Broadcasting** & Broadcast frequency & 0.5 Hz \\  & Data size & 2312 bytes \\ \hline  & Beacon frequency & 1 Hz \\
**Beaconing** & Beacon size & 378 bytes \\  & Message list entries & 40 \\ \hline  & \(ti\) & 5 ms \\
**TrAD** & \(\alpha\) & 10\({}^{\circ}\) \\  & \(max.\#\)Neighbor & 25 \\  & \(max.RadioRange\) & \(\sim\)366 m \\ \hline  & st & 5 ms \\
**AMD** & tsd & 1 \\  & ADij & DIFS \\ \hline
**UV-CAST** & \(\tau_{\mathrm{max}}\) & 500 ms \\ \hline  & st & 5 ms \\  & \(N_{st}\) & 5 \\  & WAIT I & 120 s \\  & WAIT II & 120 s \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation setting. The quantitative analysis considers the following metrics:  
* _Packet Delivery Ratio (PDR):_ It represents the average number of data messages received by the vehicles in the ROI as a percentage of the total number of data messages sent by the source node. It also can be called the coverage of data dissemination. * _Number of Transmissions:_ It is the total number of transmissions performed by the vehicles for broadcasting in the ROI during the whole simulation time. * _Delay:_ It is the average time interval between the sending of a data message by the source and its reception by the vehicles in the ROI. * _Data Dissemination Speed:_ This metric represents how fast the data can be disseminated among vehicles in the ROI. To record this metric, the source only sends data message once, and then the simulation computes the increase of data coverage with time. If the data coverage increases greatly in a short time, which means the protocol achieves a high dissemination performance. This metric is mainly used to estimate the impact of GPS drift on the performance of protocols. To comprehensively evaluate the performance of TrAD, various experiments were designed to analyze the impact of different urban maps, different traffic routes, network density and GPS drift. The geographic data were retrieved from OpenStreetMap (OSM) database.