## 4 Simulation Results
As shown in Figure 6, the values of total energy consumption of the ABF, the DBF, the single-hop, the multi-hop, the DF, the AF, the IDF, and the IAF schemes were 28.74, 45.62, 22.032, 21.879, 27.273, 16.917, 27.277, and 16.918 mJ at a spectral efficiency of 1, respectively. In addition, at a spectral efficiency of 4 the schemes consumed a total energy of 8.982, 13.204, 7.306, 13.037, 7.104, 4.378, 7.105, and 4.378 mJ, respectively. According to the result, it shows the IDF and the IAF schemes consumed lower total energy in an overall spectral efficiency range than the other schemes in which the IDF and IAF schemes compared with the DBF scheme could save a total energy consumption of 66.8% at a spectral efficiency of 2. The reason is that the the IDF, the IAF schemes could save the time slot  
Figure 5: Optimal transmitted power. Figure 6: Spectral efficiency vs. total energy consumption. according to a feedback from the destination node. In other words, the IDF, the IAF schemes coujld save energy consumption by the channel environment. On the other hand, the DBF scheme used a higher total energy consumption in an overall spectral efficiency than the others, due to RF chains depending on the number of the equipped antenna K. In the case of the total energy consumption of the multi-hop scheme, it was similar with the ABF, the single-hop, the DF, and the AF schemes. However, when the spectral efficiency was high, the total energy consumption increased gradually. The reason was that the optimal transmitted power was applied to the amplifier \(P_{AMP}\). Thus, according to the related equations the optimal transmitted power of single-hop, multi-hop, and cooperative schemes was different from each other due to a different impact of the channel response. Therefore, when the spectral efficiency was over around 3, the transmitted power of the multi-hop scheme increased more than other schemes, which caused the total energy consumption of multi-hop scheme to increase as well. In Figure 7, the impact of the ACK is displayed at the IDF scheme, when the ACK or the NACK messages were sent from the destination node. The maximum energy consumption was 10% of total energy consumption of the IDF, which was estimated [42]. According to the result, the energy consumption of ACK was small enough to neglect, and the IDF performance still maintained better than the others in Figure 6 in which the IDF with ACK compared with the DF at a spectral efficiency of 2 could save a total energy consumption of 7.11 \(m\)] more. In Figure 8, in the cases of the ABF, the DBF, single-hop, and multi-hop schemes the total energy consumption increased in the target outage probability range between \(10^{6}\) and \(3.1\times 10^{5}\) because the schemes needed more energy to satisfy the high target probability. However, the growth ratio of total energy consumption of the cooperative schemes was low due to a complement by the relay node which played a role as a redundancy in which the incremental cooperation schemes compared with the DBF could save the total energy consumption of 61.9% more at the target outage probability \(1\times 10^{-3}\). Whereas, the total energy consumption of all the schemes were constant when the target outage probability approached \(10^{-3}\). The reason was that the BPSK modulation was applied to all the schemes and the nodes were deployed within a maximum of 10 m [6]. In Figures 9 and 10, we present the throughput and normalized throughput performance as the spectral efficiency regarding eight schemes at SNR 0 dB. In Figure 9, the beamforming scheme had a better performance over the other scheme at a spectral efficiency from 0.1 to 4 in which at a spectral efficiency of 1 the beamforming, the single-hop, the multi-hop, the cooperation, and the incremental cooperation schemes had 0.7165, 0.3678, 0.1041, 0.2497, and 0.4337 [bits/s/Hz], respectively. According to the result, the throughput performance of the beamforming scheme achieved 39.4% better than the incremental cooperation scheme.