# Performance Analysis of DF Relay-Assisted D2D Communication in a 5G mmWave Network
## 4 Numerical Results and Discussion  
This section presents the simulation results of the proposed scheme to evaluate its performance. A single-cell mmWave network scenario was considered for the simulation. The operating frequency was taken to be 28 GHz for the mmWave band in Mode 2 and Mode 3. The considered path loss model for signal propagation was in accordance with Release 15 [20] of the 3 rd Generation Partnership Project (3 GPP) as per Equations (1) and (2). The path loss exponents considered for the simulation were 2, 2.5, and 3. A higher system bandwidth of 1 GHz was chosen for the simulation. The simulations were performed in the MATLAB R2021a (version) software developed by MathWorks. The simulation parameters are listed in Table 2.  
In Figure 3, a graph is plotted showing the variation in the EE with the change of the threshold SNR when varying the path loss exponents, i.e., 2, 2.5, and 3, respectively. The scattering power and circuit power consumption were taken into consideration for the accurate analysis of the EE. It can be observed from the graph that as the SNR value increased, the EE also increased exponentially. Again, the EE was also affected by the path loss exponent. The curve portraying the EE with a lower path loss exponent has a higher efficiency. This was due to the fact that higher path loss exponents encountered more interference due to blockages and fading. In Figure 4, the coverage probability of the D2D users is portrayed with the variation in the threshold SNR values for varying path loss exponents, i.e., 2, 2.5, and 3, respectively. Equation (39) justifies the curves, which shows that higher path loss exponents have lower coverage. Furthermore, with an increase in the SNR value, the coverage area of the D2D users reduced. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Sl. No.** & **Symbols** & **Significance** \\ \hline
1 & Cell radius & 500 m \\ \hline
2 & Bandwidth \(\Omega\) & 1 GHz \\ \hline
3 & Frequency (mmWave mode) & 28 GHz \\ \hline
4 & Thermal noise density & \(-174\) dBm\(/\)Hz \\ \hline
5 & Cellular power \(P_{c}\) & 30 dB \\ \hline
6 & D2D power (relay mode) \(P_{r}\) & 20 dB \\ \hline
7 & Circuit power \(P_{C}\) & 5 dB \\ \hline
8 & Scattering power \(P_{S}\) & 4 dB \\ \hline
9 & SINR threshold \(\gamma_{th}\) & 0–30 dB \\ \hline \end{tabular}
\end{table} 
Table 2: List of notations. Figure 3: EE vs. threshold SNR for varying path loss exponents. Figure 5 portrays the graph for the EE for increasing values of the distance between the D2D transmitter and the relay node for varying path loss exponents of 2, 2.5, and 3. Similar to the previous graphs, this graph also shows better performance for lower path loss exponents. However, the EE kept on decreasing as we increased the distance between the D2D transmitter and the relay node. The maximum value of the EE attained in the simulation for DF relay-assisted D2D communication was over 700 Mbps/J. Again, in Figure 6, a graph is plotted showing the comparison of the proposed DF relay-assisted D2D communication with the AF relay-assisted D2D communication for varying path loss exponents of 2 and 3, respectively. The same environment was considered for the simulation with a carrier frequency of 28 GHz. In a Rician channel, the scheme with the AF relay undergoes much interference at the receiver end due to noise amplification, whereas, in the DF scheme, the interference is canceled due to the encoding of the information at the relay node, and the D2D receiver has a better data rate with a higher SNR. Furthermore, the different modes in the proposed scheme operating at different frequencies helped reduce the co-channel interference. From Figure 6, it is evident that the EE of the proposed work at  
Figure 4: Coverage probability vs. threshold SNR for varying path loss exponents. Figure 5: EE vs. distance between the D2D transmitter and the relay node for varying path loss exponents.