System Level Modeling and Optimization of the LTE Downlink

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