## 3 System Model
### Intra-Cluster Communication Session
Figure 13 illustrates that the EEMACCSN provide minimal energy consumption than the BMA-RR in response to node density, due to its better adaptive coordination of the medium access and its ability to improve the signal strength of the received packets at the destination through cooperation. The results in Figure 14 depict the behavior of the EEMACCSN against average received SNR in the network, for variable SNR thresholds. It indicates that the energy consumption reduces with the increase of the received SNR values, since the number of retransmission is reduced due to high channel quality. It is observed at low average SNR, the energy consumption of the high SNR threshold model is better, as it compensates the capacity of the channel by diversity, while others are prone to

Figure 13: Energy consumption against number of nodes. retransmission due to SNR values, resulting in more energy consumption due to retransmissions. At high average SNR values, the energy performance of all the models is the same in terms of energy, as they all fall back to the direct transmission model, and the energy consumption is lower due to the high capacity channel. Though cooperative channels are considered to be prone to signalling packets overhead, however their effect is minimal as cooperation is implemented only when direct communication fails at low SNR. At higher SNR cooperative transmission falls back to direct transmission cutting off the signalling overhead. Also the overhead of a small size signalling packet is smaller than the one caused by the retransmission of a communication packet on the direct low quality link. The average end to end delay performance results are presented in Figure 15. The end to end delay is averaged as the time from inception to the correct reception at the destination, including the time for retransmission. Figure 14: Energy consumption per node against average SNR. Figure 15: Average end to end delay _vs._ arrival rate. It is observed from Figure 15 that the delay performance is better with the proposed MAC under cooperative communication. Though cooperative transmission adds another node and an extra slot in the transmission, it does however come with the benefit of reduced retransmission due to diversity and enhanced channel quality. In Figure 16 the throughput results are presented for EEMACCSN framework and the BMA-RR protocol with direct transmission for different number of communication sessions. It is observed form the results in this figure that a higher throughput is achievable if the number of sessions is high. This is due to the fact that the system spends most of its time in the transmit state, than when there are few communication session. It is also observed that with the use of cooperating channels the number of successful transmission increases. The results also show a steady throughput as the arrival rate in the system increases, indicating that throughput is also dependent on the systems available resources. Figure 17 displays the dynamics of the system in terms of the nodes state for variable traffic rates. At high arrival rates, the number of nodes in the active state increases and in the back off state it also increases. This is due to fact that at high traffic rate most nodes have data to send, but only the nodes that have gained access to the channel transmit their packets. Also at low data rate it is observed that there are a large number of nodes in the sleep state. The nodes that do not have data to transmit are scheduled for the sleep state to conserve the energy during the communication frame. The traffic on the sensor node has an impact on the state behaviour of the sensor node, the nodes experiencing low data arrival rates have the higher probability of staying in the sleep and hence conserving energy resources. However the number of back-off state increases with the increase of the data traffic as more nodes contend for communication resources. The system dynamics further validate the energy consumption, lifetime and throughput results presented.