## 3 System Model
### Intra-Cluster Communication Session
\begin{table}
\begin{tabular}{c c} \hline
**Number of Nodes** & **100** \\ \hline Area & 500 m \(\times\)500 m \\ Packets arrival rate & Varied from 0.01 to 0.1 packets per second \\ Data Packet & 250 bytes \\ Length Packets (RTS,CTS,ACK) & 18 bytes \\ Length Packets (RSU,SCH) & 16 bytes \\ Initial Energy Eo & randomly distributed between (0–50) Joules \\ Pw\_transmit & 462 mW \\ Pw\_receive & 346 mW \\ Pw\_idle & 310 mW \\ Pw\_sleep & 100 μW \\ SNR threshold at receiver & 9 dB \\ \hline \end{tabular}
\end{table} 
Table 2: Simulation parameters. Figure 11 presents the network lifetime results of the proposed framework. The network lifetime depends on the energy consumption of the individual nodes as their lifetime determines the connectivity of the network. The higher the energy consumption on the sensor nodes the faster the nodes energy gets depleted, this has a direct impact on the lifetime of the sensor network. It is observed that the lifetime decreases with the increase in the arrival rate due to the fact that the nodes radio spend most time in the communication mode which consumes more energy on the sensor nodes. The lifetime of the developed EEMACCSN protocol with cooperative communication is longer than when direct communication is used. This is attributed to the high energy consumption in the direct

Figure 10: Total energy consumption per node _vs._ arrival rate. Figure 9: Intra-cluster energy consumption per node _vs._ arrival rate. communication, due to the high probability of retransmission occurrence since there is no measure to mitigate the fading effects of the wireless channels in direct transmission. Figure 12 presents the energy performance of the proposed MAC protocol over variable SNR threshold with varying arrival rate settings. For cooperative communication the energy consumption in the network decreases with the increase in the SNR threshold. The high SNR threshold means that the cooperative communication will often be employed in the network thereby improving the energy performance through the use of more

Figure 11: Network lifetime _vs._ arrival rate. Figure 12: Energy consumption _vs._ SNR_threshold. reliable high capacity channels. However, for cooperative communication, the SNR thresholds in the system should be selected with great care, as they impact the way cooperative systems behave. Low thresholds result in unreliable channels as direct transmission is allowed, even when the received SNR is low, at the same time very high thresholds lead to delay and waste of energy, where additional nodes are used to cooperate while a single transmission would provide enough signal quality. For direct communication, as expected, the energy consumption is not affected by the SNR threshold, since the system does not check the threshold to decide on the communication. It is observed from the results the increase in the traffic load influences more energy consumption in the network. The proposed EEMACCSN protocol provides better energy performance with increasing SNR threshold than BMA-RR with direct transmission. Figure 13 presents results for total energy consumption against increasing network node density for variable data arrival rates. As the network size increases, the interference and overhead for communication packets increases. The number of control packets transmitted to avoid collisions increases, leading to more energy consumption for transmission of communication packets. Increasing the number of network nodes also increases the likelihood of interference during packet transmissions, which reduces the SNR of transmitted packets, leading to more possible retransmissions for reliable communication. Also, since the arrival is independent on each sensor node, increasing the node density in the network increases the arrival in the network leading to increased total energy consumption.