System Level Modeling and Optimization of the LTE Downlink

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5. Performance Evaluation of Fractional Frequency Reuse in LTECombining the number of β FR values and Γ thr values taken into consideration, 3 366FFR simulations are required to evaluate throughput performance for each schedulerconfiguration. An example UE and eNodeB distribution from one of the 3 366 simulatedones in shown in Figure 5.4. The figure corresponds to the FFR configurationβ FR = 0.7, Γ thr = 12.75 dB. In blue are the UEs the results of which are takeninto account (center cells, grey-marked). In order to reduce simulation time andavoid border-map artifacts, UEs not attached to the center cells, marked pale-red,are skipped. Marked as blue dots, are the FR UEs, while crosses mark the PR UEs.As shown in Figure 5.2, the FR zone extends in the direction the antennas of theeNodeB radiate (marked with a line), extending in a petal-shape from each site.The same set of channel realizations have been employed by all simulations, so asto avoid a necessary averaging over channel realizations if independent ones wouldhave been taken into account. While employing the same channel realizations foreach simulation will not yield statistically significant throughput results, the relativedifference between FFR and reuse-1 will still be valid, which can equally answer thequestion of the usefulness of FFR applied to LTE.100080081318600400371217200y pos [m]0−200−400211651110161519−600−800−10004914−1000 −500 0 500 1000x pos [m]Figure 5.4: Network layout and UE distribution for one of the 3 366 LTE system levelsimulations employed in one FFR performance evaluation batch. β FR = 0.7,Γ thr = 12.75 dB. Marked grey are the cells taken into acocunt for the results.Outside of this area, UEs are not simulated (red UEs). In blue are the UEs inthe considered cells (dots represent FR UEs, crosses PR UEs).70
5. Performance Evaluation of Fractional Frequency Reuse in LTE5.4. Round Robin Simulation Results and Fairness MetricThe UE throughput results for the round robin scheduling case, in which the PHYresources are equally distributed among the 30 UEs in the cell, are shown in Figure5.5. Every colored dot in each of the figures represents the average UE throughput(from left to right: mean, edge and peak throughput) obtained from an LTEsystem level simulation with β FR and Γ thr corresponding to the values in the x- andy-axis, respectively.In the upper row, mean, edge, and peak UE throughput in Mbit/s is depicted,while the lower row exhibits throughput gains (%) respective to the reuse-1 case.Additionally in the lower row, the area corresponding to an improvement of averageand edge throughput are highlighted. As previous treatments of FFR focused on anoptimization of the average and edge throughput, this aims at visualizing a similarthroughput region of interest.SINR threshold [dB]20151050Mean throughput [Mbit/s] Edge throughput [Mbit/s] Peak throughput [Mbit/s]0.90.70.50.30.176543211.81.61.41.210.80.60.40.20.9 0.7 0.5 0.3 0.1 0.9 0.7 0.5 0.3 0.170605040302010SINR threshold [dB]20151050Mean throughput gain (%) Edge throughput gain (%) Peak throughput gain (%)120501004080306020401020000.9 0.7 0.5 0.3 0.1 0.9 0.7 0.5 0.3 0.1 0.9 0.7 0.5 0.3 0.1400350300250200150100500−50Figure 5.5: LTE FFR throughput results with round robin scheduling. Mean/edge/peakthroughput (Mbit/s) over the simulated β FR and Γ thr set (top row) and throughputgain relative to the reuse-1 case (%) for the area where mean and edgethroughput gain is positive (bottom row).Just taking into account these metrics, results indicate the existence of FFR configurationsthat improve average, edge, and peak throughput, and thus offer an apparentoverall performance increase. However, more careful examination of such cases showthat these performance metrics do not properly reflect the throughput distribution.71
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DissertationSystem Level Modeling a
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I hereby certify that the work repo
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KurzfassungDie vorliegende Arbeit p
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ContentsContents1 Motivation and Sc
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Contentsix
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1. Motivation and Scope of Work1. M
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BibliographyThe combined throughput
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2. 3GPP Long Term Evolution2. 3GPP
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2. 3GPP Long Term Evolutionup to 30
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2. 3GPP Long Term EvolutionNAS proc
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2. 3GPP Long Term Evolutionchannel
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System Level Modeling and Optimization of the LTE Downlink

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