# A Cross-Layer Media Access Control Protocol for WBANs
## 5 Simulation Results
Figure 7 illustrates the packet reception ratios of the simulated networks under different packet sizes. Since sensors always use the maximum transmission power to upload packets in the IEEE 802.15.6 scheme, a higher packet reception ratio can be achieved. When PACR-PA or PACR-CP is deployed, a base transmission power is used when uploading periodic data, and the packet reception ratio is lower compared with the IEEE 802.15.6 protocol. However, for event-triggered data, emergency data, and periodic data beyond the normal range of health, the packet reception ratio can be guaranteed since the priority-based transmission adjustment scheme is used. Data can be re-transmitted during the CAP. Adaptive adjustment of appropriate transmission power can ensure acceptable packet arrival rates while effectively extending network lifetime. Because heterogeneous data have varying priorities, it is important to guarantee the reliability of high-priority data. Our proposed scheme can effectively prolong the network lifetime and ensure the reliability of high-priority data, whereas a desired packet reception ratio can also be achieved for periodic data. However, for applications where the importance of data cannot be determined, it can be challenging to evaluate the impact of periodic data loss. Figure 6: Lifetimes of networks in simulated scenarios. (**a**) Lifetime of the first network; (**b**) Lifetime of the second network. Finally, we evaluated the overall throughput of the network to provide a better comparison of the performance improvement achieved by our proposed protocol. Figure 8 shows the total throughput of different schemes under the two considered networks. When a smaller transmission power is used to upload data, more packets can be sent by a sensor. However, sending more packets does not necessarily mean that more packets can be received by the coordinator. To achieve higher throughput, a proper packet reception ratio should also be guaranteed. In our proposed protocol, a suitable transmission power can be chosen based on the channel status, which is neither too high nor too low. This allows more packets to be sent while maintaining the desired packet reception ratio. Therefore, the total throughput is higher for our protocol compared to the IEEE 802.15.6 protocol. As shown in Figure 8, the total throughput of the PACR-PA scheme is 3.4 to 2.8 times that of the IEEE 802.15.6 protocol under different packet sizes in the first scenario. Furthermore, the total throughput is improved by 17% to 20% for the PACR-CP scheme compared to the PACR-PA scheme. In the second network, the total throughput of the PACR-PA scheme is 3.6 to 3.0 times that of the IEEE 802.15.6 protocol under different packet sizes. Moreover, the total throughput is improved by 38% to 44% for the PACR-CP scheme compared to the PACR-PA scheme. The simulation results demonstrate that with the use of our proposed cross-layer protocol, the network is able to transmit more packets and achieve higher energy efficiency, even with the initial energy distribution being the same across the network. The simulation results above demonstrate that our proposed cross-layer protocol can effectively improve the overall performance of the network. Regarding the limitations of the protocol, firstly, the protocol mainly considers the data transmission requirements of  
Figure 8: Total throughput in simulated scenarios. (**a**) Total throughput in the first scenario; (**b**) Total throughput in the second scenario. Figure 7: Packet reception ratios in simulated scenarios. (**a**) Packet reception ratio in the first scenario; (**b**) Packet reception ratio in the second scenario. common applications, such as periodic data and sporadic event-triggered data. However, for nodes that do not have a clear pattern in data generation timing, further research is needed on how to adaptively improve their data transmission efficiency and reliability.