System Level Modeling and Optimization of the LTE Downlink

More documents

Recommendations

Info

5. Performance Evaluation of Fractional Frequency Reuse in LTE5.1. Principles of Fractional Frequency ReuseFFR is based on dividing the cell into a center part, where interference is lower andreuse-1 is employed, and an outer part, where a higher frequency reuse factor isemployed (typically a reuse factor of three). This accomplishes an improvement ofthe SINR at cell edge, while still allowing the UEs placed at the cell center to usethe whole bandwidth.In this chapter, the assumed FFR scheme is the most commonly found scheme inliterature, which combines a reuse-1 center zone, denoted as the Full Reuse (FR)zone, and an outer zone employing reuse-3, denoted as the Partial Reuse (PR) zone.As shown on Figure 5.1 (from left to right): (i) the cells are divided into a centerFR and an edge PR zone. In the PR zones, three frequency bands are cyclicallyallocated (reuse-3), while in the FR zones, the same frequency is reused. (ii) Afraction β FR of the total bandwidth is allocated to the frequency band employedin the FR zones. The remaining bandwidth (a fraction of 1 − β FR of the total) isequally allocated to each of the three PR bands. i.e., (1 − β FR )/3 to be assigned toeach PR zone.cell 1cell 1cell 3cell 2cell 2cell 3Frequency allocationFR Zone: reuse-1,PR Zone: reuse-3,Figure 5.1: Principles of FFR. Left: frequency allocation over the cells. Middle: separationof the cell into a Full Reuse (FR) and a PR zone, employing reuse-1 and reuse-3,respectively. Right: bandwidth allocation of the frequency bands employed.Thus, two parameters configure the allocation of the PHY resources to the FR/PRzones: (i) the distribution of the bandwidth, and (ii) the cell area allocated to eachzone. The first parameter is defined by the bandwidth partitioning factor β FR , asshown in Figure 5.1. For the division of the cell area among the FR and PR zones,some prior work has proposed a distance-based metric [132]. However, such a metricis only meaningful for a circularly-symmetric case, and not applicable for the morerealistic sectorized case. Thus, in this case, the employed metric for dividing the cellinto the FR and PR zones is that of an SINR threshold, denoted as Γ thr , which isfurther explained in Section 5.2.66
5. Performance Evaluation of Fractional Frequency Reuse in LTEThis work assumes a hexagonal grid of sites with three cells per site, with a constantnumber of UEs per cell and a full-buffer traffic model assumption. This results ina cell layout such as that in the example in Figure 5.1, where each cell contains acenter area employing reuse-1 and an outer area employing reuse-3.5.2. Previous WorkWhile capacity is commonly employed to determine the switching point between theFR and PR zones (simplified into a distance metric for circularly symmetric casesand a SINR threshold for sectorized cases), such a capacity-based approach does nottake into account the presence of multiple UEs and is thus incomplete [133].With the premise that a UE should be assigned to the FR or PR zone so as tomaximize its throughput, and that the PHY resources are shared among all UEsin a cell, capacity density (analogous to UE throughput through the assumptionof a uniform UE density over the cell area) was initially employed to evaluate thepotential benefits of FFR.pos y [m]35030025020015010050FR zone PR zone Combined FR&PR (FFR)pos y [m]pos y [m]350300250200150100503503002502001501005050 100 150 200 250pos x [m]50 100 150 200 250pos x [m]50 100 150 200 250pos x [m]2520151050−5−109008007006005004003002001000Figure 5.2: Capacity density-based FFR results for β FR = 0.75 and Γ thr = 3.20 dB. The cellarea combines a reuse-1 zone (marked green) with a reuse-3 area (marked red).The FR and PR areas of the cell are depicted in terms of SINR (center row) andcapacity density (bottom row). Column-wise, the spatial distribution is shownfor the FR zone (left), the PR zone (middle), and combined (right). FR and PRzone boundaries are marked with dashed lines.67
Page 1:
DissertationSystem Level Modeling a
Page 5:
I hereby certify that the work repo
Page 9:
KurzfassungDie vorliegende Arbeit p
Page 13 and 14:
ContentsContents1 Motivation and Sc
Page 15 and 16:
Contentsix
Page 17 and 18:
1. Motivation and Scope of Work1. M
Page 19 and 20:
1. Motivation and Scope of Worklaye
Page 21 and 22:
1. Motivation and Scope of Workperf
Page 23 and 24:
BibliographyThe combined throughput
Page 25 and 26:
2. 3GPP Long Term Evolution2. 3GPP
Page 27 and 28:
2. 3GPP Long Term Evolutionup to 30
Page 29 and 30:
2. 3GPP Long Term EvolutionNAS proc
Page 31 and 32: 2. 3GPP Long Term Evolutionchannel
Page 33 and 34: 2. 3GPP Long Term EvolutionSince th
Page 35 and 36: 2. 3GPP Long Term EvolutionThe chan
Page 37 and 38: 2. 3GPP Long Term EvolutionTable 2.
Page 39 and 40: 3. Physical Layer Modeling and LTE
Page 67 and 68: 4. Extensions to the L2S Model4. Ex
Page 69 and 70: 4. Extensions to the L2S Model4.1.2
Page 71 and 72: 4. Extensions to the L2S ModelTo ac
Page 73 and 74: 4. Extensions to the L2S ModelBLER1
Page 75 and 76: 4. Extensions to the L2S ModelThe M
Page 77 and 78: 4. Extensions to the L2S Modelthe a
Page 79 and 80: 4. Extensions to the L2S ModelIn th
Page 81: 5. Performance Evaluation of Fracti
Page 85 and 86: 5. Performance Evaluation of Fracti
Page 97 and 98: 6. Summary and Outlook6. Summary an
Page 99 and 100: 6. Summary and Outlook6.2. OutlookW
Page 101 and 102: A. SNR-independence of the CLSM Pre
Page 107 and 108: B. Correlation Matrices for Shadow
Page 109 and 110: C. Taylor Expansion of the ZF MSEC.
Page 111 and 112: C. Taylor Expansion of the ZF MSEAp
Page 113 and 114: D. Evaluation of Multi-User GainD.
Page 115 and 116: D. Evaluation of Multi-User GainAvg
Page 117 and 118: Abbreviations and AcronymsAbbreviat
Page 119 and 120: Abbreviations and AcronymsKPILLRL2S
Page 121 and 122: Abbreviations and AcronymsU-PlaneUT
Page 123 and 124: Abbreviations and AcronymsBibliogra
Page 125 and 126: Abbreviations and Acronymsdescripti
Page 127 and 128: Abbreviations and Acronyms[69] Tech
Page 129 and 130: Abbreviations and Acronymsfemto cel
Page 131: Abbreviations and Acronyms[134] Z.
show all

System Level Modeling and Optimization of the LTE Downlink

Create successful ePaper yourself

Delete template?

Save as template?