# Intersection-Based Link-Adaptive Beaconless Forwarding in Urban Vehicular Ad-Hoc Networks
## 4 Performance Analysis
### Scenario Setup and Performance Metrics  
With an aim to replicate urban environment, a city scenario in the form of Manhattan grid is created using a software called simulation of urban mobility (SUMO) [50]. Figure 3 shows an illustration of a scenario highlighting the position coordinates of road intersections and destination. As depicted in the figure, the roads are bidirectional with each direction consisting of two lanes. In addition, to make the scenario more realistic, traffic signals were installed at some of the road intersections. Mobility traces generated from SUMO are then imported in QualNet 8.1 network simulator [51] through mobility model generator for vehicular networks (MOVE) [52] tool for performance analysis. Figure 2: ILBFC architecture. Also, in order to simulate a realistic vehicular wireless channel, the path loss must be beyond basic path loss estimation models such as free-space path loss [53] as the radio propagation needs to take into account the different sources of interference. One such path loss model is the two-ray interference model [54] which considers the constructive/destructive self-interference while taking into account the transmitter (\(h_{t}\)) and receiver (\(h_{r}\)) antenna heights over the ground and the relative permittivity (\(\varepsilon_{r}\)) of the ground surface. The path loss (\(L_{t}\)) for two-ray interference model mentioned in [54,55] is calculated using Equation (14). The sub-variables for Equation (14) are given in the expressions (15)-(21):  
\[L_{t}=20\times\log(4\times\pi\times\frac{d}{\lambda}\times|1+(\mathrm{Y}_{\perp }\times e^{j\times\varphi})|^{-1}), \tag{14}\]  
\[\varphi=2\times\pi\times\frac{d_{ref}-d_{los}}{\lambda}, \tag{15}\]  
\[\mathrm{Y}_{\perp}=\frac{\sin\theta_{i}-\sqrt{\varepsilon_{r}-\cos^{2}\theta_ {i}}}{\sin\theta_{i}+\sqrt{\varepsilon_{r}-\cos^{2}\theta_{i}}}, \tag{16}\]  
\[\epsilon_{r}=\varepsilon_{r}-(j\times 60\times\mu\times\lambda), \tag{17}\]  
\[d_{los}=\sqrt{d^{2}+(h_{t}-h_{r})^{2}}, \tag{18}\]  
\[d_{ref}=\sqrt{d^{2}+(h_{t}+h_{r})^{2}}, \tag{19}\]  
\[\sin\theta_{i}=\frac{h_{t}+h_{r}}{d_{ref}}, \tag{20}\]  
Figure 3: Illustration of the scenario. \[\cos\theta_{i}=\frac{d}{d_{ref}}, \tag{21}\]  
where \(d\) is the distance between the transmitting and receiving antennas, \(\lambda\) is the wavelength, Y\({}_{\perp}\) is the reflection coefficient, and \(\varphi\) is the phase difference. \(d_{los}\) and \(d_{ref}\) are the distances covered by direct and reflected rays, respectively. \(j\) represents the complex number (\(\sqrt{-1}\)) and \(\theta_{i}\) is the angle of incidence for reflected ray, where subscript \(i\) indicates \"incidence\". As mentioned in [55], the material generally used for road surface is asphalt and has a relative permittivity value (\(\epsilon_{r}\)) of 5 and a conductivity value (\(\mu\)) of 0. Although two-ray interference model offers increased level of realism compared to the free-space model for unobstructed scenarios, it does not consider the shadowing effect due to obstructions such as buildings, trees, etc. Therefore, in the proposed scenario, the total path loss (\(L\)) is computed as follows:  
\[L_{t}=20\times\log(4\times\pi\times\frac{d}{\lambda}\times|1+(\mathrm{Y}_{\perp }\times e^{j\times\varphi})|^{-1}), \tag{14}\]0  
where \(X_{\sigma}\) is a zero mean Gaussian distributed random variable with \(\sigma\) being the standard deviation. The Gaussian distribution is used to take into account the random effects of shadowing that a moving vehicle may face from the surrounding obstructions. \(L_{sys}\) represents the system loss that occurs during the data transmission at the sender side and the data reception at the receiver side, and is computed as follows:  
\[L_{t}=20\times\log(4\times\pi\times\frac{d}{\lambda}\times|1+(\mathrm{Y}_{\perp }\times e^{j\times\varphi})|^{-1}), \tag{14}\]1  
where \(A_{eff}\) is the loss due to antenna efficiency, \(A_{mismatch}\) is the antenna mismatch loss, and \(A_{connection}\) is the antenna connection loss.