Impact of user mobility on transmit power control in ultra dense networks

Ultra dense network (UDN) is considered as a promising solution to support high throughput applications with lower operational cost. However, user mobility is even tricky for UDNs, especially in high-speed cases. While handover issues have been widely studied, the impact of high mobility on resource allocation needs to be further studied. In this paper, we investigate the impact of user mobility on transmit power control (TPC) and propose two kinds of mobility-aware TPC schemes which are adaptive to user's speed intelligently: mobility-aware constant TPC (MC-TPC), mobility-aware sub-slotted TPC (MS-TPC). Investigating the distance distribution between the moving user and its access base station (BS), we derive the analytical expressions of system outage probability (OP) and energy efficiency (EE) in the mobile environment to characterize the performance of the proposed and referenced TPC schemes. Numerical results show that the proposed mobility-aware TPCs significantly improve system reliability in terms of OP and data rate, especially with the proper sub-slots division. Meanwhile, in exchange for high reliability, EE degrades within a reasonable range with the increase of moving speed.