## 5 Simulation Results
### Simulation Results  
#### 5.2.1 Energy Consumption Results  
Energy is one of the key challenges of WSNs. Substantial energy loss happens due to link asymmetry. Figures 9 and 10 show the network's average energy consumption and energy consumption per packet, respectively.  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Parameters** & **Values** \\ \hline Node deployment area & 1000 m \(\times\) 1000 m \\ \hline Number of nodes & 27/54/90 \\ \hline Node’s initial energy & 2000 J \\ \hline Simulation Time & 150 s \\ \hline Sensing Range & 70 m \\ \hline \(T_{x}\) Energy & 0.50 J \\ \hline \(R_{x}\) Energy & 0.25 J \\ \hline Asymmetry (\%) & 10 \(\sim\) 90 \\ \hline ACK Timeout & 0.4 s \\ \hline Queue Length & 256 Packet \\ \hline Waiting Time \(t\) & 1 s \\ \hline \hline \end{tabular}
\end{table}
Table 4: Simulation parameters.  
Figure 9: Average energy consumption: (**a**) for 27 nodes; (**b**) for 54 nodes; and (**c**) for 90 nodes.  
Average energy consumption of the network is calculated as total amount energy used (control packet, data packet, idle listening) by all members of the network divided by the total number of nodes. Here, the proportion of asymmetric links was varied to populate simulation results. Conversely, per packet energy consumption is defined as the energy consumption in the network to the number of successfully transmitted packets.  
\[E_{avg}=\frac{E_{DATA}+E_{cp}+E_{idl}}{N} \tag{5}\]  
Here, \(E_{avg}\) represents average energy consumption per node, \(E_{DATA}\) is energy consumption for transmitting data, \(E_{cp}\) represents energy consumption for the control packet, \(E_{idl}\) represents energy consumption for idle listening, and N represents the network's total number of nodes.  
Figure 9 exhibits the relationship between percentage of asymmetric links and average energy consumption. It was observed that, as asymmetric links increase, the node's power consumption increases as well. In ASYM-MAC, it was identified that if a node switches into sender-initiated mode and transmits the preamble, nearby nodes are not aware of the change. As a result, there are many collisions between the beacon and the preamble, adding to energy consumption. The preamble also creates extra overhead, which consumes more energy. In the case of 50% link asymmetry, the percentage of average energy consumption for COASYM-MAC protocol is reduced by 56% for 27 nodes (Figure 9a), by 51% for 54 nodes (Figure 9b), and by 55% for 90 nodes (Figure 9c) compared to ASYM-MAC protocol.  
\[E_{packet}=\frac{E_{consumption}}{\text{Total generated data packet}} \tag{6}\]  
Here, \(E_{packet}\) is the Energy consumption per packet and \(E_{consumption}\) is the total energy consumption in the network.  
Figure 10: Per packet energy consumption: (**a**) for 27 nodes; (**b**) for 54 nodes; and (**c**) for 90 nodes.  
Figure 10 shows that, with the increase of link asymmetry, energy per packet is also increased. COASYM-MAC can effectively reduce this increase in energy consumption. In the case of 50% link asymmetry, it can reduce the energy consumption per packet by 54% for 27 nodes (Figure 10a), by 49% for 54 nodes (Figure 10b), and by 51% for 90 nodes (Figure 10c) as compared to the ASYM-MAC protocol.