## 3 Proposed Methodology
### Estimation of Link Delay  
The total delay in a multihop scenario is the sum of all hop delays. The single-hop total delay for a scenario without flow control, which is given in work [61], can be extended by including a flow control protocol, as given in Equation (6):  
\[\mathcal{D}_{i}=t_{trans,i}+t_{q,i}+t_{cont,i}+t_{proc,i}+t_{control,i}+t_{prop,i} \tag{6}\]  
In Equation (6), \(\mathcal{D}_{i}\) is the total one-hop delay of node \(i\), \(t_{trans,i}\) is the transmission delay for the last data packet of node \(i\), \(t_{q,i}\) is the queuing delay (the total delay for dequeuing all other data packets except the last data packet residing in the queue of node \(i\)), \(t_{cont,i}\) is the contention delay for the last data packet of node \(i\), \(t_{proc,i}\) is the processing delay for the last data packet of node \(i\), \(t_{prop,i}\) is the propagation delay for the last data packet of node \(i\), and \(t_{control,i}\) is the delay corresponding to flow control for the last data packet in the queue of node \(i\). By considering each packet in the queue of a given hop, Equation (6) can be rewritten in the form given in Equation (7):  
\[\mathcal{D}_{i}=\sum_{j=1}^{K}(t_{trans,ij}+t_{cont,ij}+t_{proc,ij}+t_{control, ij}+t_{prop,ij}) \tag{7}\]  
In Equation (7), \(K\) is the total number of packets in the queue of node \(i\), \(t_{trans,ij}\) is the transmission delay for transmitting the \(j\)th packet in the \(i\)th node, \(t_{cont,ij}\) is the contention delay for transmitting the \(j\)th packet in the \(i\)th node, \(t_{proc,ij}\) is the processing delay for transmitting the \(j\)th packet in the \(i\)th node, \(t_{control,ij}\) is the control delay for transmitting the \(j\)th packet in the \(i\)th node, and \(t_{prop,ij}\) is the propagation delay for transmitting the \(j\)th packet in the \(i\)th node. The delay occurrence sequence for a given hop in the case of a transmitter having one packet in the queue for a vehicular network, that implements Carrier Sense Multiple Access-Collision Avoidance (CSMA-CA) with flow control and Carrier Sense Multiple Access-Collision Detection (CSMA-CD) without flow control, can be graphically illustrated, as shown in Figure 6.  
The control delay for the \(j\)th data packet in the \(i\)th node (\(t_{control,ij}\)), when flow control consists of Request to Send-Clear to Send (RTS-CTS) in CSMA-CA, can be formulated using Equation (8). The reader is advised to refer to Figure 6a for an understanding of the formulation. \[ \begin{split} t_{control,ij}&=t_{prop,ij}+t_{rts}+t_{ proc}+t_{cts}+t_{prop,ij}+t_{proc,ij}+t_{ack}+t_{prop,ij}+t_{proc,ij}\\ &=3t_{prop,ij}+3t_{proc,ij}+t_{rts}+t_{cts}+t_{ack}\end{split}  \tag{8}\]  
Note that, in Equation (8), \(t_{rts}\) is the transmission delay for transmitting the RTS packet, \(t_{cts}\) is the transmission delay for transmitting the CTS packet, and \(t_{ack}\) is the transmission delay for transmitting the acknowledgment packet. In CSMA-CD, \(t_{control,ij}=0\), as flow control does not exist. The reader is advised to refer to Figure 6b to understand the preceding argument. Thus, by substituting \(t_{control,ij}\) into Equation (7) using Equation (8), Equation (9) can be derived, which shows the total one-hop delay of the \(i\)th node using wireless communication channel (\(\mathcal{D}_{iWL}\)) when stop-and-wait with RTS-CTS flow control protocol-based CSMA-CA is implemented:  
\[ \begin{split}\mathcal{D}_{iWL}&=\sum_{j=1}^{K}(t_{ trans,ij}+t_{cont,ij}+t_{proc,ij}+t_{control,ij}+t_{prop,ij})\\ &=\sum_{j=1}^{K}(t_{trans,ij}+t_{cont,ij}+t_{proc,ij}+3t_{prop,ij }+3t_{proc,ij}+t_{rts}+t_{cts}+t_{ack}+t_{prop,ij})\\ &=\sum_{j=1}^{K}(t_{trans,ij}+t_{cont,ij}+4t_{prop,ij}+4t_{proc,ij}+t_{rts}+t_{cts}+t_{ack})\end{split}  \tag{9}\]  
Figure 6: Illustration of delay occurrence sequences in CSMA–CA and CSMA–CD, (**a**) Delay occurrence sequence with stop and wait with RTS–CTS flow control in CSMA–CA. (**b**) Delay occurrence sequence without flow control in CSMA–CD.