# Energy-Efficient Resource and Power Allocation for Underlay Multicast Device-to-Device Transmission
## 5 Simulation Results  
In this section, numerical results are provided to demonstrate the performance of our proposed strategy. We use the clustered distribution model adopted in [17], where a 400 m \(\times\) 400 m square area is used to simulate the network. Cluster heads are randomly distributed in the simulation area according to the uniform distribution and the D2D users are randomly distributed in the corresponding multicast cluster. The distance-based path loss and shadowing fading are considered for the transmission channel. We still consider the scenario that D2D clusters and CUs share uplink cellular RBs together. Suppose that all available resource is divided into RBs and each CU is allocated with one RB at each scheduling slot. Other related simulation parameters are listed shown in Table 1.  
In order to demonstrate the performance of the proposed energy-aware resource and power allocation scheme, three other different algorithms are considered. The first one is the QoS-aware resource allocation scheme proposed in [7], which aims at minimizing the interference among D2D multicast cluster and CU through resource allocation. Moreover, the power control policy in [7] assumes that both CU and D2D cluster transmit at the maximum power when the channel condition is good enough. The second one is the cluster based scheme proposed in [18], which employs social information to facilitate file transfer process. In the absence of resource pairing scheme between D2D cluster and CU, the resource assignment between D2D cluster and CU in [18] is assumed to be chosen randomly while power control method is not applied. The third one is the energy-efficient scheme proposed in [14], which aims at improving the energy efficiency multicast transmission through proper power control. The power control principle of [14] is similar to our proposed scheme which tries to allocate more transmit power to D2D pairs when the channel condition becomes good. For clarity, our proposed scheme is referred to as the \"Proposed energy-aware\" scheme. Figure 2 illustrates the sum energy efficiency of the D2D multicast cluster with the variation of the D2D cluster radius. From Figure 2 we can see that with the increase of the D2D cluster radius, the energy efficiency performance of our proposed scheme is better than other referenced schemes. This is because the channel gain of the D2D link will decrease with the increase of D2D cluster radius. Hence, a larger transmit power is required for the D2D clusters so as to satisfy the SINR threshold constraint. Accompanied with the increase of D2D cluster radius, our proposed scheme gradually increases the transmit power. This results in the decreased energy efficiency of the D2D cluster. Compared with the scheme in [14], our proposed resource allocation method minimizes the interference from CUs to co-channel D2D receivers, which improves the channel gain of D2D links. Furthermore, it is shown that when there are more UEs in the considered scenarios (\(N\) varies), the overall energy efficiency also increases due to the increased total transmission rate of all D2D multicast clusters. Figure 3 compares the total throughput of D2D multicast clusters of the proposed scheme with three other schemes. From the figure, we can see that the total throughput performance of the proposed \begin{table}
\begin{tabular}{l l} \hline \hline
**Parameter** & **Value** \\ \hline Cell Radius & 400 m \\ Total UE number & 500, 1000 \\ Spectrum bandwidth & 10 MHz \\ Bandwidth of each RB & 180 KHz \\ The path loss Component (\(\alpha\)) & 4 \\ Shadowing & Log-normal fading with standard deviation of 8 dB \\ Noise power spectrum density (\(\sigma^{2}\)) & \(-\)174 dBm/Hz \\ Minimum SINR Threshold (\(\Gamma_{\min}^{\text{D2D}}\)\(\Gamma_{\max}^{CU}\)) & 10 dB \\ Maximum transmit power of UE (\(P_{\max}^{\text{D2D}}\)\(\rho_{\max}^{\text{D2D}}\)) & CU: 23 dBm, D2D user: 20 dBm \\ D2D cluster radius (\(r\)) & 30–90 m \\ UE Transmission range & 90 m \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The simulation parameters.