Contrasting Open-Loop and Closed-Loop Power Control Performance in UTRAN LTE Uplink by UE Trace Analysis
ABSTRACT Uplink power control in UTRAN Long Term Evolution consists of an open-loop scheme handled by the User Equipment and closed-loop power corrections determined and signaled by the network. In this study the difference in performance between pure open-loop and combined open and closed-loop power control has been analyzed and the different behavior of fractional vs. full path-loss compensation has been evaluated. A comprehensive system level simulation model has been used with a facility to trace a particular test user during its motion from eNodeB towards the cell border and back to its initial position. This study demonstrates the effect of distance path-loss of a test user on several physical layer performance metrics including throughput, resource allocation as well as modulation and coding scheme utilization. Simulation results in a fully loaded network show high throughput for open-loop fractional power control for the user located in the vicinity of the serving eNodeB, however, steep performance degradation has been observed when the user is moving towards the cell edge. The user throughput at the cell border can be increased by the closed-loop component. The benefit of closed-loop power control is the higher homogeneity in terms of throughput across the entire network area and the ability to automatically stabilize the network performance under different conditions like cell load and traffic distribution.
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ABSTRACT: Uplink power control in 3GPP UTRAN Long Term Evolution (LTE) networks consists of a closed-loop scheme around an open-loop point of operation. The uplink performance of the network is decisively influenced by power control. This paper provides insight into the power control procedure and its interworking with Adaptive Transmission Bandwidth (ATB) as well as Adaptive Modulation and Coding (AMC) presenting a detailed performance evaluation by system level simulations for a fully loaded network. The analysis starts for pure open-loop power control as reference, for which the impact of parameter settings on resource allocation, utilization of specific modulation and coding schemes, retransmission rate, and resulting throughput has been determined. A two-dimensional parameter optimization for full path-loss compensation and fractional power control has been performed to conclude the best strategy for the trade-off between network capacity and coverage. Finally on top of this optimized open-loop power control parameter set the closed-loop component has been enabled and proposals for optimum power control threshold settings are provided. The beneficial effects of closed-loop power control are presented highlighting its ability to adjust the transmission power according to the desired quality and level requirements.12/2008: pages 175-184;
Conference Proceeding: Interference Based Power Control Performance in LTE Uplink[show abstract] [hide abstract]
ABSTRACT: In LTE uplink, the slow varying path gain and shadowing are compensated by the standardized open loop power control (OLPC). Further optimization of the system performance can be done via closed loop power control commands. In this contribution, it is shown that using such commands to control the interference caused by users to the system, it is possible to achieve a gain in the order of 20% on the average cell throughput while maintaining the same outage cell throughput compared to the performance of the OLPC. Furthermore, gain on both average and outage cell throughput can be achieved by tuning the parameters of the proposed scheme.Wireless Communication Systems. 2008. ISWCS '08. IEEE International Symposium on; 11/2008
Conference Proceeding: Performance of Uplink Fractional Power Control in UTRAN LTE[show abstract] [hide abstract]
ABSTRACT: UTRAN long term evolution is currently being standardized in 3GPP with the aim of more than twice the capacity over high-speed packet access. The chosen multiple access for uplink is single carrier FDMA, which avoids the intra-cell interference typical of CDMA systems, but it is still sensitive to inter-cell interference. As a result, the role of the power control becomes decisive to provide the required SINR, while controlling at the same time the interference caused to neighboring cells. This is the target of the fractional power control (FPC) algorithm lately approved in 3GPP. This paper evaluates in detail the impact of a FPC scheme on the SINR and interference distributions in order to provide a sub-optimal configuration tuned for both interference- and noise-limited scenarios.Vehicular Technology Conference, 2008. VTC Spring 2008. IEEE; 06/2008