# Maximum Transmit Power for UE in an LTE Small Cell Uplink
## 4 Performance Evaluation
### Homogenous Macro/Small Cell Deployment
Therefore, it was proposed not to employ the FPC, but the full pathloss compensation in the small cell environment instead [25]. Figure 6: Outage probability as a function of SIR for the UE at the cell edge. To see the impact of \(P_{\rm max}\) on the interference generation, Equation (10) was plotted in Figure 8 for both macro and small cell cases. For the small cell case, \(P_{\rm max}\) = 23 dBm resulted in a very significant increase in interference compared to the macro cell case. The target was to find the \(P_{\rm max}\) limit which resulted in almost similar received SIR performance as compared to the uniform macro cell deployment with \(P_{\rm max}\) = 23 dBm. The maximum transmit power for the small cell was varied so that the same interference level as the macro cell could be achieved. Figure 8 shows that a decrease in \(P_{\rm max}\) resulted in a decrease in the interference. At \(P_{\rm max}\) = 18 dBm, the received SIR for the small cell was almost similar to that achieved in the macro cell case, as depicted in Figure 9. This justifies our intention of reconsidering the \(P_{\rm max}\) for the small cell case and not adopting the same value as that adopted in the macro cell case. Figure 8: Interference comparison as a function of \(P_{\rm max}\) in the uniform macro and small cell deployments. Figure 7: SIR as a function of \(a_{\rm small}\) in the homogenous small cell deployment. Also, it is interesting to note from comparing Figures 5 and 9 that with the FPC, the SIR performance in the case of small cells with \(P_{\text{max}}=18\) dBm showed a similar pattern with that in the macro cell case in Figure 5, which suggests that the FPC can be adopted in small cells as well. A comparison between Figures 7 and 9 clearly supports our argument that the FPC mode with \(P_{\text{max}}=18\) dBm showed much better performance than the case in which \(P_{\text{max}}=23\) dBm, where the cell edge as well as the cell average received SIR showed a clear difference in performance. In Figure 10, the spectral efficiency for the cell average as well as for the user near the eNodeB and cell edge computed using Equations (12) and (13) is presented as a function of the pathloss compensation factor \(\alpha_{\text{small}}\). It can be seen in Figure 10, that for the users near the serving eNodeB, the spectral efficiency dropped as the pathloss compensation factor increased and for cell edge users there was an increase in the spectral efficiency. This trend was attributed to the FPC, where the cell edge user performance can be improved at the cost of a decrease in performance for users near the cell center. The average spectral efficiency showed a slight decrease as the \(\alpha_{\text{small}}\) value approached from 0 to 1. From this trend, we can infer that the FPC mode can be adopted in small cells with a slight trade-off between the cell-average and cell-edge UE performance. The above analysis suggests that for the case with the small cells, the \(P_{\text{max}}\) level must be kept to 18 dBm instead of 23 dBm, and the FPC mode can be employed instead of the full compensation mode since it shows a significant improvement in the network performance. Figure 9: SIR as a function of \(\alpha_{\text{small}}\) in the homogenous small cell deployment.