Conference Paper

Contrasting open-loop and closed-loop power control performance in UTRAN LTE Uplink by UE Trace Analysis

Radio Access, Nokia Siemens Networks GmbH & Co. KG, Munich, Germany
DOI: 10.1109/ICC.2009.5198853 Conference: Communications, 2009. ICC '09. IEEE International Conference on
Source: IEEE Xplore


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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    • "A key difference in uplink as compared to downlink is that fractional power control is often used in uplink to fully or partially compensate for the path loss, e.g., as defined in 3GPP-LTE [24]. The influence of fractional power control on system performance is studied in various works, e.g., [25]–[27] under regular hexagonal topology. For networks with random topology and accounting for fractional power control, [28] analytically derives uplink SIR and rate distribution for single-tier networks; [29] investigates uplink outage capacity for two-tier networks with shared spectrum; [30] extends the analysis to multi-tier uplink networks in terms of outage probability and spectral efficiency. "
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    ABSTRACT: The joint user association and spectrum allocation problem is studied for multi-tier heterogeneous networks (HetNets) in both downlink and uplink in the interference-limited regime. Users are associated with base-stations (BSs) based on the biased downlink received power. Spectrum is either shared or orthogonally partitioned among the tiers. This paper models the placement of BSs in different tiers as spatial point processes and adopts stochastic geometry to derive the theoretical mean proportionally fair utility of the network based on the coverage rate. By formulating and solving the network utility maximization problem, the optimal user association bias factors and spectrum partition ratios are analytically obtained for the multi-tier network. The resulting analysis reveals that the downlink and uplink user associations do not have to be symmetric. For uplink under spectrum sharing, if all tiers have the same target signal-to-interference ratio (SIR), distance-based user association is shown to be optimal under a variety of path loss and power control settings. For both downlink and uplink, under orthogonal spectrum partition, it is shown that the optimal proportion of spectrum allocated to each tier should match the proportion of users associated with that tier. Simulations validate the analytical results. Under typical system parameters, simulation results suggest that spectrum partition performs better for downlink in terms of utility, while spectrum sharing performs better for uplink with power control.
    Preview · Article · Dec 2014 · IEEE Journal on Selected Areas in Communications
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    • "The difference between the performance of pure open loop power control and combined open loop and closed loop power control has been studied in [2], [3]. It has been shown in [4] that the fractional path loss compensation factor with closed loop power control can greatly improve the system performance. "
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    ABSTRACT: Uplink power control plays a key role on the performance of uplink cellular network. In this work, the power control factor ($\in[0,1]$) is evaluated based on three parameters namely: average transmit power, coverage probability and average rate. In other words, we evaluate power control factor such that average transmit power should be low, coverage probability of cell-edge users should be high and also average rate over all the uplink users should be high. We show through numerical studies that the power control factor should be close to $0.5$ in order to achieve an acceptable trade-off between these three parameters.
    Full-text · Article · Jan 2014
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    • "For this paper, we used the European Telecommunication Standards Institute (ETSI) traffic model [4], where the packets size and the packet transmission timer are assumed to follow the truncated Pareto distribution. The [4] is a widely used in various analytical and simulation studies of 3GPP networks, such as [7], [10], [12], [16], [17]. "
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    ABSTRACT: The 4G standard Long Term Evolution (LTE) has been developed for high-bandwidth mobile access for today's data-heavy applications, consequently, a better experience for the end user. To extend the user equipment battery lifetime, plus further support various services and large amount of data transmissions, the 3GPP standards for LTE/LTE-Advanced has adopted discontinuous reception (DRX). However, there is a need to optimize the DRX parameters, so as to maximize power saving without incurring network re-entry and packet delays. In this paper, we provide an overview of the fixed frame DRX cycle and compare it against an adjustable DRX cycle of the LTE/LTE-Advanced power saving mechanism, by modelling the system with bursty packet data traffic using a semi-Markov process. Based on the analytical model, we will show the trade-off relationship between the power saving and wake-up delay performance.
    Full-text · Conference Paper · Jun 2012
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