## 8 Simulation Setup and Analysis of Results
### Network Coverage Efficiency
Figure 17: Average packet delay at different intervals. Figure 18: Average packet delay at different mobility levels (speed in m/s). Figure 19 presents the number of packets delivered by BN-MAC and other protocols using variable packet sizes. BN-MAC delivers more packets than the other protocols. BN-MAC uses a balanced semi-synchronous schedule between the neighbor nodes. A semi-synchronous schedule helps to reduce energy consumption. Thus, the node energy exhibits a sharp decrease as the packet size exceeds an optimal length. This trend can be attributed to the maximum overhead, which increases the average re-transmission and thus decreases throughput. As the packet size increases, the exposed interval and probability of an interfering node increase. When BN-MAC uses 256 contention windows to avoid interfering nodes, there is a marginal likelihood that the packets will be dropped. In this manner, the size of the packets does not decrease the performance. BN-MAC also uses the dynamic adjustment of packet size (DAPS) function, which handles the variable size of the packets. Thus, there is a marginal likelihood of packet re-transmission. BN-MAC is also advantageous in terms of sampling and randomization, thus avoiding the packet loss. The other MAC protocols use 1-16 contention windows for randomized listening before sending their preamble message. BN-MAC configures the contention window to 256 slots. Thus, there is small probability of dropping the data packet because only 5% of the nodes may choose the same slots at the same time. Figure 20 presents the energy consumption for 20,000 variable-length packets delivered and acknowledged using BN-MAC and other hybrid MAC protocols. BN-MAC consumes less energy than A-MAC, ADC-SMAC, LPRT-MAC, Speck-MAC, and Z-MAC. The variable size of the packets does not significantly affect BN-MAC due to the use of the DAPS function to handle the variable packet lengths. Less energy is consumed because the idle listening time is controlled, as the sensor node consumes the maximum amount of its energy without performing actions on the channel. The AAS model brings the sensor node into the sleep state after the event processes are no longer being monitored. Thus, the AAS model helps to maintain the fairness of the energy in the network during events. In Figure 21, we present the duty cycle for BN-MAC and other hybrid MAC protocols at different sensing ranges. BN-MAC exhibits a low duty cycle, whereas the other MAC protocols exhibit a higher duty cycle. The capacity to send packets at faster rate is affected as the sensing range is increased. In duty cycling, the node is periodically placed into the sleep state, which is effective for decreasing the  
Figure 19: Number of packets delivered with variable packet sizes. energy dissipation in the network. In BN-MAC, energy is saved to bring the sensor node into the sleep state using the AAS model and a semi-synchronous technique. The packet adjustment-based duty cycle feature of BN-MAC also effectively reduces energy consumption without significantly reducing throughput and increasing latency. Other participating MAC protocols take an even longer period of time to access the channel and deliver the packets, thus increasing the energy consumption. As a result, the sensor node consumes additional energy when sending larger control messages, which consume 40%-70% of the network bandwidth. Thus, there is not a sufficient amount of power remaining in the other MAC protocols to send data for longer distances. For example, when the sensing range is 700 m, the duty cycle of BN-MAC is approximately 11%-12%, whereas A-MAC, ADC-SMAC, LPRT-MAC, Speck-MAC, and Z-MAC have duty cycles of 20%-29% because it takes a longer period of time to access the channel and forward the data packets. Figure 21: Average duty cycles at variable sensing ranges. Figure 20: Energy consumption with variable packet sizes.