# Distance-Based Resource Allocation for Vehicle-to-Pedestrian Safety Communication
## 4 Classification of Vulnerable Road Users  
In this section we will classify the V2P users in three different clusters as shown in Table 3. Type 1 (very critical) V2P users are in most crucial state which requires an ultra-reliable link, Type 2 (critical) users are slightly less vulnerable, and Type 3 users are also classified according to their requirements. The classification is distance dependent (distance between the vehicle and cellular user). A 50-meter distance initiates the V2P communication and thereafter the users are classified accordingly. In the next two sections, we will use this classification for resource allocation.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **V2P Link** & **CUE Link** \\ \hline Path loss model & 127 + 30 log\({}_{10}\)(\(\ell\)) & 128.1 + 37.6 log\({}_{10}\)(\(\ell\)) [21] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Path Loss Model.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Symbol** & **Definition** \\ \hline \(h_{c,B}\) & Desired channel Gain between CUE and BS \\ \(h_{v_{c}}\) & Interference channel gain from V2P to CUE \\ \(h_{v}\) & Desired channel gain between V2P \\ \(h_{crp}\) & Interference channel gain from CUE to V2P \\ \(P_{crx}\) & CUE transmit power \\ \(P_{v_{v}x}\) & V2P transmit power \\ \(h^{a,b}\) & Channel gain between two users \\ \(PL\) & Path loss \\ \(Y\) & Log normal shadowing \\ \(\ell^{-}\gamma\) & \(\ell\) is the distance between two users and \(\gamma\) is the decay exponent \\ \(g^{a,b}\) & Small scale fading component \\ \(Pmax^{c}\) & Maximum allowable transmit power for CUE \\ \(Pmax^{v}\) & Maximum allowable transmit power for V2P \\ \(p\) & Probability of outage \\ \(\gamma_{0}\) & Threshold SINR for CUE \\ \hline \hline \end{tabular}
\end{table}
Table 2: List of Symbols.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **V2P Link** & **CUE Link** \\ \hline Path loss model & 127 + 30 log\({}_{10}\)(\(\ell\)) & 128.1 + 37.6 log\({}_{10}\)(\(\ell\)) [21] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Path Loss Model.  
In Figure 2, we can see the V2P users classified into three types, depending on their vulnerability. Users involved in direct communication with infrastructure are referred as CUEs. The shortest distance between two users is found using the coordinates during simulation.  
In a real-life scenario, a number of methods can be used to calculate the distance between devices. The first and foremost is the global positioning system (GPS) that can be used to find the coordinates. However, accuracy of this method is still low especially when we talk about safety communication. Secondly, received signal strength indicator (RSSI) can be used to estimate the distance between two devices. The author in [22] has used the RSSI-based technique, assuming the absence of the GPS, to find the distances between the vehicles for short-range communication. In our scenario distance is calculated between two users once they enter a D2D range. User equipment (UE) location reporting is defined in the 3 GPP TS 23.303 standard, where UE reports its location on periodic basis to their corresponding servers [23]. This information is available at the network level.