Performance comparison between open-loop and closed-loop uplink power control in UTRAN LTE networks

Abstract

Uplink power control in 3GPP UTRAN Long Term Evolution networks supports an optional closed-loop component around an open-loop point of operation. In this study the performance difference between pure open-loop and combined open- and closed-loop power control has been evaluated using a full blown system level simulation model. The interworking between power control, adaptive transmission bandwidth, and adaptive modulation and coding has been thoroughly analyzed and the resulting performance differences depending on the users' locations within the cells are demonstrated by two-dimensional network plots. A deep inhomogeneous throughput distribution throughout the deployment area has been observed for pure open-loop power control. Enabling the closed-loop component results in a more homogeneous performance albeit at lower mean throughput. Significant impact is given by the selected quality and level targets for the closed-loop component. The benefit of closed-loop power control is the higher homogeneity in terms of throughput across the entire cell area and its ability to adjust the transmission power according to the desired quality and level targets. Hence the network performance is stabilized in various cell environments.