## 4 Simulation Verification
### Simulation of Retransmission Signal Energy Consumption  
Energy consumption is a direct indicator for the evaluation of the automatic request retransmission strategy. So an experiment on algorithm energy consumption was designed [1; 2; 37; 38; 39; 40; 1]. The experiment was set up with the condition that four relay nodes and one listener node were involved in cooperative communication. The energy consumed by the four different algorithms was calculated; Figure 6 shows the relationship between the four algorithms' energy consumption with the signal-to-noise ratio. When the signal-to-noise ratio is 5 db, the cooperative communication contains three phases, such as signal broadcast, signal forwarding and signal retransmission. Therefore, the collaborative communication consumes the excess energy of 4 J. As the signal-to-noise ratio increases, the four algorithms control the collaborative communication signal-forwarding work and the energy consumed by the system gradually decreases. In Table 3, it can be seen that because the total energy consumed by broadcasting and forwarding in communication is  
Figure 5: Simulation comparison of system gain variation for different number of relay nodes. (**a**) Comparison of System Gain amplification with SNR of 15 db. (**b**) Comparison of System Gain amplification with SNR of 20 db. (**c**) Comparison of System Gain zoomed in with SNR of 25 db. 1.255 J [39, 40], the energy consumed by the system in Figure 6 is greater than 1.255 J. The system contains at least one retransmission signal. However, the number of retransmissions is reduced. As the signal-to-noise ratio continues to increase, the probability of the signal being accepted increases and the energy consumed by the system gradually decreases. Figure 6b shows that when the signal-to-noise ratio is higher than 20 db, the energy consumed is much less than four relays of the dedicated signal, which indicates that the higher the value of the signal-to-noise ratio, the lower the number of cooperative communication relays [40]. This conclusion is verified in Figure 6c. The energy of the improved algorithm is 1.004 J. This is because the number of nodes included in the cooperative communication is four (one relay, one source node, one destination node and one listener node, an average energy consumption of 1.255 \(\times\) 4/5 J). Energy consumption is the key factor affecting the quality of the communication service [34, 36] when it is consumed. Since the LCARQ algorithm in Figure 1 consumes the least amount of energy, the system energy consumption is related to the signal-to-noise ratio, and when the signal-to-noise ratio is the same, the algorithm of LCARQ consumes the least amount of energy. The improved algorithm LCARQ has fewer retransmissions than the other three compared algorithms and consumes the least amount of energy for network communication. This indicates that the quality of service of the LCARQ communication has been improved. The quality of communication services was evaluated by calculating the values of three indicators. The comparison of experimental results shows that the improved algorithm achieves the goal of low-power communication [3, 17, 35, 36]. The BER, number of retransmission relays and energy consumption of various algorithms were calculated and compared under different signal-to-noise ratio conditions. The listening node sends the signal to reduce the value of BER and the energy consumption is also reduced. The experimental results show that the improved algorithm is not the best algorithm under the same conditions (because of interference), but the improved algorithm is the most practical in cooperative communication when considered together. The participation of listening  
Figure 6: Comparison of the energy consumption of the retransmission process for different algorithms. (**a**) Residual energy comparison with SNR of 15 db. (**b**) Residual energy comparison with SNR of 20 db. (**c**) Residual energy comparison with SNR of 25 db.