# Maximum Transmit Power for UE in an LTE Small Cell Uplink
## 2 Cell Topology and Related Work
In terms of uplink power control for the UE, the optimization of the network performance is fundamentally dependent on the uplink measurements. Therefore, from the user's perspective, energy consumption at the UE needs to be addressed for static small cell deployment. In particular, the maximum transmit power limit \(P_{\max}\) needs to be revisited, as it is the major contributor towards interference. Similarly, by focusing on reduction of the downlink energy consumption, a dynamic small cell deployment strategy can be considered, where the base station can be deployed in areas with higher UE density to improve the service quality in the case of mega events or disaster management--that is, in the case of network failure. By considering approaches such as stochastic geometry, several recent works presented dynamic base station deployment schemes by considering mobile base stations (aerial drone or vehicular mounted), which can roam in the network coverage area to address capacity issues. In Reference [28], a game theory-based mobility control scheme for flying drone base stations was presented, which can guide the movement of the drones in macro cell hotspots. The results designate that the proposed scheme can efficiently optimize the spectral efficiency by minimizing the number of drones in the network, while maintaining the safety perspectives to avoid the risk of the collision of drones and maintain an optimal altitude. However, the focus was on downlink performance enhancement and the issue of frequent handoffs on the UE's end was not considered while discussing the user association. Similarly, by considering the recovery of the network infrastructure to sustain user communication for disaster management, the authors in Reference [29] studied the efficient utilization of autonomous mobile base stations (aerial or vehicular) to improve network reachability in emergency situations. A mobile base station fit mechanism was proposed which employs mobile base stations to automatically construct new routes and assess and adaptively respond to the fitness of pause positions, such that mobile base stations can provide links to recover the disconnected network infrastructure based on dynamic and local interaction with the stationary macro and small cells. In Reference [30], an extensive analysis of cell coverage, capacity, and inter-cell interference for an aerial base station was presented. From the coverage results, the optimal altitude for an aerial base station was reported and the coverage dependency for power transmitted by a base station was shown. However, the focus was only on the downlink and the impact on UE association was not considered. Due to the free movement of mobile base stations over the entire service area, UE may frequently find different base stations available for communication, resulting in increased power consumption due to the frequent handoffs. More importantly, the negative impact of base station height relative to the UE discussed in Reference [31] was neglected, which presented a new and significant theoretical discovery, i.e., the serious problem of area spectral efficiency crash. It showedthat if the absolute height difference between base station antenna and UE antenna is larger than zero, then the area spectral efficiency performance will continuously decrease with network densification for an ultra-dense small cell network. Thus, the network capacity suffers from severe degradation compared to fixed-cell topology as the drone base station flies higher. Additionally, during the travel period, a mobile small cell is unable to provide service due to the serious channel fading, and thus, a loss in the service time occurs, as discussed in Reference [32]. Due to the mobility of the base station, the availability of reliable wireless backhaul links and the related resource allocation are principal issues that should be considered while adopting the dynamic small cell base station deployment strategy [33].