## 5 Numerical Results
Thus, the performance of the HHT protocol is generally better than that of the HDT protocol under similar conditions. Figure 4: The impact of different distances between the BS and the sensor nodes on the packet timeout probability. In Figure 6, we investigate the system reliability of the HHT and HDT protocols. where the information transmission time is \((1-\alpha)_{k}=0.19\), the coordinates of the sensor nodes are set to \((x_{k},y_{k})=(0.3,0.3)\)[22], and the energy-harvesting time for the HHT protocol and the HDT protocol is \(\alpha_{0k}=0.01\) and \(\alpha_{0}=0.05\), respectively, and the energy-harvesting efficiency is \(\eta_{k}=0.5\). The figure clearly indicates that as SNR \(\gamma_{0}\) increases, so does the system reliability. This is because an increase in SNR results in more energy being harvested by sensor nodes, which is then used for uplink information transmission, resulting in improved system performance. Furthermore, we observe that the system reliability of the HHT protocol is higher than that of the HDT protocol at the same SNR. This is due to the fact that the HHT protocol harvests energy at the head of each segment, which is less affected by channel status than the HDT protocol, which harvests energy at the head of the total period. Similarly, we also found that under the condition of HHT protocol, the system reliability using MRC technology is better than that of using SC technology. This is because the MRC selects the maximum value of the channel gain, which has a higher channel gain than the average value of the channel gain selected by the SC, which results in the system being able to harvest more energy for information transmission. We can also observe that increasing the number of antennas from \(M=2\) to \(M=3\) increases system reliability by utilizing the HDT protocol with MRC technology. Figure 5: The impact of harvesting efficiency coefficients on the packet timeout probability. Figure 6: The simulation results of the impact of the SNR on system reliability. Figure 7 depicts the impact of energy-harvesting time length on the system reliability of the HHT and HDT protocols in the complete system. We fix energy-harvesting efficiency as \(\eta_{k}=0.5\), and the coordinates of the sensor nodes are set to \((x_{k},y_{k})=(0.3,0.3)\). The figure shows that extending the energy-harvesting time increases the system reliability. This is because the sensor nodes can obtain more energy from the BS, reducing the data packet loss rate during data transmission and improving system performance. Furthermore, we have consistently observed that the HHT protocol outperforms the HDT protocol in terms of system reliability regardless of the energy-harvesting time length. This is because the HHT protocol uses a more reasonable time allocation method, allocating energy-harvesting time at the head of each time slot, and is less affected by complex channel environments. Additionally, the HHT protocol utilizes MRC technology, which results in the highest system reliability and best system performance. Figure 8 shows how the energy-harvesting efficiency coefficient affects the probability of a system outage in our wireless communication system. Specifically, we fix the energy-harvesting time for the HHT and HDT protocols at \(\alpha_{0k}=0.01\) and \(\alpha_{0}=0.05\), respectively, and set the information transmission time as \((1-\alpha)_{k}=0.19\). The energy-harvesting efficiency is held constant at \(\eta_{k}=0.5\). Our simulation results demonstrate that increasing the energy-harvesting efficiency leads to a continuous decrease in the outage probability in our wireless communication system, as shown in Figure 8. Furthermore, the HHT protocol consistently outperforms the HDT protocol in terms of lower outage probability. This superiority can be attributed to the fact that the HHT protocol harvests energy at the beginning of each time slot, which is less susceptible to channel fading. Consequently, more energy is available for information transmission, resulting in a reduced outage probability.