Soc Classification level 1© Nokia Siemens NetworksPresentation / Author / Date Enhanced Uplink Carrier Aggregation for LTE-Advanced Femtocells VTC Fall: September 6 th 2011 Authors: Luis G. Uzeda Garcia et. al.

Soc Classification level 2© Nokia Siemens NetworksPresentation / Author / Date Outline Motivation : Problem Definition Preliminaries: UL FPC and ACCS Proposed Solution Simulation Assumptions & Results Conclusions

Soc Classification level 3© Nokia Siemens Networks Motivation: Problem Definition UL Carrier Aggregation in Macro Cells: – Possible to schedule UEs on multiple CCs – Problem: single or multiple CCs? – Answer: distinguish between power limited and non-power limited UEs UL Carrier Aggregation in Femto Cells: – Problem: single or multiple? – Fact: power limited UEs are unlikely – Poor answer: always multiple CCs – Better answer: consider CA for ICIC Hua Wang, et al., “Uplink Component Carrier Selection for LTE-Advanced Systems with Carrier Aggregation,” in IEEE ICC, June 2011

Soc Classification level 4© Nokia Siemens Networks Preliminaries: UL Fractional power control Power control formula [TS ]: P [dBm] = min{ P max, P 0 + α*L + 10*log 10 M + Δ mcs + f(Δ i ) } Power control in uplink aims at: – Controlling inter-cell interference – Prolonging UE battery life time – Achieving lower receiver dynamic range Thinking multi-cell: – Uncoordinated femtocell deployments – Close Subscriber Groups – Severe inter-cell interference – Introduce UL FPC information into the CC selection procedure Not considered in this study UL “interfered zones” may differ from UE to UE

Soc Classification level 5© Nokia Siemens NetworksPresentation / Author / Date Preliminaries: ACCS in a nutshell Femto is powered on Select Base CC Traffic Increases Select Supplementary CCs Evaluation based on BIM entries BIM relies on DL measurements! Nice DL simulation results! What about the UL? ACCS Framework Autonomous Component Carrier Selection (ACCS) is a self-organizing and fully distributed interference management concept on a CC level.

Soc Classification level 6© Nokia Siemens NetworksPresentation / Author / Date Proposed Solution (1/2) Apply ACCS ACCS Assumptions BIMs: predict C/I experienced whenever two cells (serving and interferer) use the same CC at the same time with equal transmit Power Spectral Densities UL {1} → {2} ≈ DL {1} ← {2} UL {1} ← {2} ≈ DL {1} → {2} UE 1 UE 2 UE 3 UE 1 UE 2 UE 3 Cell-Specific Equivalent FAP CC-set UE-Specific U Equivalent FAP CC-set U Expected Outcomes

Soc Classification level 7© Nokia Siemens NetworksPresentation / Author / Date Proposed Solution (2/2) “Fixing” BIMs UE (i) is the UE, among the ones served by HeNB {1}, with the largest path loss towards it, in this example UE [B]. This UE is potentially the worst victim of incoming UL interference. UE (j) is the UE responsible for cell’s {1}, i.e. cell’s {2}. This is the UE served by HeNB {2} that potentially is the worst source of UL interference towards HeNB {1} – in this example UE [C]. UE (k) in (5) is the one responsible for cell’s {1}, i.e. the worst source of outgoing uplink interference towards HeNB {2}. In this case, it is UE [B] as well (k=i), but this is not necessarily always true. Either way, this has no impact in terms of signaling since UEs (i,k) are served by the same evaluating cell. Finally, UE (l) is analogous to UE (i), in that, it is the UE with the largest path loss towards its serving cell {2} and hence the worst potential victim of outgoing interference, in our example: UE [D]. Cell-Specific UE-Specific

Soc Classification level 8© Nokia Siemens NetworksPresentation / Author / Date Simulation Assumptions Dual Stripe scenario: Deployment Assumptions Topology: – Three floors (up to 120 Femtos) – Deployment ratio 75% Closed Subscriber Group (CSG) No co-channel Macro layer Antenna configuration: 2x2 Path loss model from R Wall penetration loss: 5/10 dB (inner/outer) walls Uniform distribution of 1 UE and 3UEs per residence (always indoors) Simple full buffer traffic Equal resource packet scheduling ACCS Assumptions 5 Component Carriers Minimum required SINR for primary CC and secondary CC equals 15 and 8 dB, respectively UL FPC Assumptions P 0 =[-50] dBm α = [ , 0.6, 0.8,1.0 ] P TX min = -40 dBm P TX max = 23 dBm

Soc Classification level 9© Nokia Siemens NetworksPresentation / Author / Date Key Performance Indicators UL SINR CC usage/cell and CC usage/UE Average UL Cell TP – Aggregated throughput from all UEs connected to a single cell [Mbps] UL Outage User TP – 5%-percentile of UE throughput [Mbps] Normalized (relative) versions of the two variables: – Baseline performance: Unmodified ACCS

Soc Classification level 10© Nokia Siemens NetworksPresentation / Author / Date Simulation Results: 1 UE/cell UL SINR: Original ACCS versus proposed method. The 0% to 10% outage region is highlighted. The correction is much more relevant for low values of α as the imbalance between DL and UL estimations increases. The share of UEs who have access to at least 2 CCs increases when compared to the original case. That combined with the SINR improvement led to the significant relative gains in outage throughput Imbalance:

Soc Classification level 11© Nokia Siemens NetworksPresentation / Author / Date Perfomance Results: 1 UE/cell and 3 UEs/cell The potential of the proposed scheme, especially in terms of UL 5% outage throughput where relative gains of up to 52% are seen with respect to the original non-FPC-aware ACCS concept. UE specific with 3UEs/cell: the effective CC usage per cell is the set union of the CC usage of its served UEs. Cells reuse CCs more aggressively when compared to UEs.

Soc Classification level 12© Nokia Siemens NetworksPresentation / Author / Date Final Remarks and Conclusions ACCS provides a fully distributed (scalable) and self-adjusting frequency re-use mechanism for the UL as well. Enhanced Uplink Component Carrier Selection Scheme boosts UL performance further. User Specific Uplink Component Carrier Selection allows a “virtual” and controlled reuse-1, thus solving the UL CA problem in Femtocells. Actively tweaking FPC parameters using the proposed framework are suggested for future studies.

Soc Classification level 13© Nokia Siemens Networks Thank You! Questions?

Soc Classification level 14© Nokia Siemens NetworksPresentation / Author / Date Appendix with additional slides

Soc Classification level 15© Nokia Siemens NetworksPresentation / Author / Date Perfomance Results: ACCS 75% ACCS seems to capture the benefits from the ‘best’ frequency reuse cases in terms of both KPIs. Results inline with DL ones. All results are normalized with respect to plain frequency re-use with no power control.

Soc Classification level 16© Nokia Siemens Networks Performance Summary Deployment Ratio Configuration Average cell capacity Outage capacity 25% 1/1 {-60; 0.6} -5% +25% 1/3 {NO PC} -43% +116% ACCS {-60; 1} +18% +235% 75% 1/1 {-60; 0.6} -8% +69% 1/3 {-60; 0.8} -7% +332% ACCS {-60; 0.8} +26% +416% P 0 ≈ -60 dBm and high α values [0.6, 0.8] seem to be the most promising settings.