# Maximum Transmit Power for UE in an LTE Small Cell Uplink
## 4 Performance Evaluation
### HetNet Deployment with Uniformly Distributed Small Cells  
In this section, the performance analysis for the first HetNet deployment scenario is presented. Uniform macro/small cell deployments in above section were considered as reference cases. From Figure 2, it is clear that there were two interfering rings of small cells around the central small cell. The \(P_{\text{max}}\) limit was varied for the small cell uplink from 16 dBm to 23 dBm. The target was to find the \(P_{\text{max}}\) value which resulted in the same SIR value as compared to the uniform macro cell deployment with \(P_{\text{max}}\) = 23 dBm and uniform small cell deployment with \(P_{\text{max}}\) = 18 dBm.  
To see the result of interference offered to the central small cell from the interfering rings as well as the macro cells, Equation (19) was plotted in Figure 11. It can be observed that the interference was slightly increased as compared to Figure 8 due to the addition of macro cell interference. However, the interference from the small cells was dominant as compared to the macro cell interference. The macro cell interference was lower, as the major interference was only from the macro cell containing the small cells. The neighboring macro cells were at \(5R\) from the central small cell eNodeB; therefore, their interference had a minor impact on the central small cell. In Figure 11, it can be clearly seen that for small cells, \(P_{\text{max}}\) = 17.48 dBm corresponded to the same interference level as compared to the reference cases with \(P_{\text{max}}\) = 23 dBm and \(P_{\text{max}}\) = 18 dBm in uniformly distributed macro and homogenous small cell deployments, respectively.  
To see the impact of increased interference and decreased \(P_{\text{max}}\) value, received SIR was obtained in Figure 12 using Equation (20). The trend with an increase in \(\alpha_{\text{small}}\) can be observed clearly for the UE near eNodeB (i.e., UE with the index 1); the received SIR decreased from 10.53 dB to 4.5 dB. Compared to Figure 5, the received SIR showed a loss of 0.17 dB and a gain of 0.3 dB for \(\alpha_{\text{small}}\) = 0.7 and \(\alpha_{\text{small}}\) = 1, respectively.  
Figure 10: Spectral efficiency for small cells as a function of distance and \(\alpha_{\text{small}}\) in homogenous small cell deployment.  
Similarly, compared to Figure 9, the received SIR loss was 0.03 dB and 0.15 dB for \(\alpha_{\text{small}}=0.7\) and \(\alpha_{\text{small}}=1\), respectively. Meanwhile, for the UE near the cell edge (i.e., UE with the index 6), the received SIR improved from 3.15 dB to 4.5 dB. The received SIR compared to Figure 5 showed a loss of 0.05 dB and a gain of 0.3 dB, for \(\alpha_{\text{small}}=0.7\) and \(\alpha_{\text{small}}=1\), respectively. While the loss compared to Figure 9 was 0.05 dB and 0.15 dB. Like the previous section, the lower value of \(\alpha_{\text{small}}\) resulted in a better SIR for the UE near the eNodeB, while the UE near the cell edge suffered from degradation in received SIR and vice versa. Also, the results support our argument of adopting FPC instead of full compensation in the small cell uplink in a HetNet environment with a reduced \(P_{\text{max}}\) value, as the comparison of Figure 7  
Figure 11: Interference comparison as a function of \(P_{\text{max}}\) in the uniform macro cell and HetNet deployments.  
Figure 12: SIR as a function of \(\alpha_{\text{small}}\) in the HetNet deployment.  
with Figure 12 showed a clear gain in received SIR by adopting FPC. This trend can be validated further by comparing the spectral efficiency in Figure 10 with Figure 13, where the reduced \(P_{\text{max}}\) value in small cells had a negligible impact on the small cell UE's performance.