# Intersection-Based Link-Adaptive Beaconless Forwarding in Urban Vehicular Ad-Hoc Networks
## 4 Performance Analysis
### Simulation Results
#### 4.3.2 Node Density Variation  
This section demonstrates the influence of node density variation on the performance of the routing protocols in terms of PDR, average ETE delay and PRC as shown in Figure 6. Node density is considered high when a large number of nodes are in proximity of one another within a particular area and vice versa for low node density scenarios. Here, five scenarios obtained by varying the number of nodes from 10 to 50 with an incremental step of 10 have been tested with a fixed simulation area of 1200 m \(\times\) 1200 m as indicated in Table 2. In all network density scenarios, except one static destination, all nodes are mobile. Also, for these scenarios, the maximum speed of the node is set to 50 km/hr and \(R_{src}\) is fixed to 400 kbps. Figure 6a depicts the PDR performance of the protocols with respect to varying node density. It can be seen that PDR for all the protocols is increasing until the number of node reaches 30, after which it remains almost stable. The major reason for the packet drops in low density scenarios is the lack of availability of suitable relay nodes to forward the data packet towards destination. DBD has the lowest PDR performance due to its lack of forwarding zone criteria which may lead to packet collision and its strict winner relay management condition which rarely allows the relay node to be in \"winner\" state. This further results in packet drops due to buffer overflow, which is one of the drawbacks of frequent relay selection process and is also witnessed in the BLR's PDR performance. ILBFC yields superior PDR performance compared to other protocols due to its better winner relay management based on \(\delta_{eff}\) which enables the relay nodes to stay in \"winner\" state but not for too long as in the case of LBF, possibly reducing packet collision. The average PDR performance gains of ILBFC over LBF, DBD and BLR for the case when the number of nodes is varied from 30 nodes to 50 nodes are 1.5%, 14.7% and 9.4%, respectively. The average ETE delay performance of the data packets received at the destination for all the protocols with respect to varying node density is shown in Figure 6b. All protocols result in high average ETE delay when the node density is the lowest (10 nodes). The reason for this is the scarcity of suitable relay nodes leading to data packets being sent to destination through longer routes causing high average ETE delay. ILBFC, due to its better winner relay management, has the lowest average ETE delay when compared to the rest. Specifically, for this scenario, the mean values of the average ETE delay of ILBFC, LBF, DBD, and BLR are 21 ms, 24 ms, 23.7 ms and 21.9 ms, respectively. Another noticeable aspect of the analysis is the LBF's large average ETE delay at high node density (50 nodes), which is because of the network congestion caused by the redundant packets flowing throughout the network. This in turn is due to selection of more that one relay node at the single hop level which is one of the drawbacks of \"winner\" relay node moving out of the forwarding zone. Figure 6c shows the effect of node density variation on the PRC performance. It can be seen that there is an overall increase in PRC, which corresponds to decreasing unicast efficiency, for all the protocols with rising node density. This is expected since the upsurge in the number of nodes increases the chances of having multiple relay nodes at single hop level. BLR with an average PRC value of 1.1, minimizes the selection of multiple relay nodes at the single hop level and is due to its relay selection process for every received data packet. Here, DBD with an average PRC value of 4, does not have the highest PRC compared with the rest of all node densities.