Soc Classification level 1© Nokia Siemens NetworksPresentation / Author / Date Enhanced Uplink Carrier Aggregation for LTE-Advanced Femtocells VTC Fall:

Soc Classification level 1 © Nokia Siemens Networks Presentation / Author / Date

Enhanced Uplink Carrier Aggregation for LTE-Advanced Femtocells

VTC Fall: September 6th 2011Authors:Luis G. Uzeda Garcia et. al.


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

?


Preliminaries: UL Fractional power control

Power control formula [TS 36.213]:

P[dBm] = min{ Pmax, P0 + α*L + 10*log10M + Δmcs + f(Δi) }

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


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.


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}

UE1

UE2

UE3

UE1

UE2

UE3

Cell-Specific

Equivalent FAP CC-set

UE-Specific

U

Equivalent FAP CC-set

U

Expected Outcomes


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].

),(),(}{}{}{}{ jijinSnS PSDPSDLLDLUL

),(),(}{}{}{}{ lklknSnS PSDPSDLLDLUL

Cell-Specific

),(),(}{}{}{ jjnSn PSDPSDLLDLUL

),(),(}{}{ llnn PSDPSDLLDLUL

UE-Specific


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 R4-091422• 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

10 m

10 m

10 m

10 m

10 m

ACCS Assumptions• 5 Component Carriers• Minimum required SINR for primary CC

and secondary CC equals 15 and 8 dB, respectively

UL FPC AssumptionsP0 =[-50] dBm

α = [0.2 0.4, 0.6, 0.8,1.0 ]

PTX min = -40 dBm

PTX max = 23 dBm


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


Simulation Results: 1 UE/cellUL 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.

-20 -15 -10 -5 0 5 10 15 20 25 300

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Average UL SINR [dB]

Em

piric

al C

DF

SINR Comparison

=0.2 Original

=0.4 Original

=0.6 Original

=0.8 Original=0.2 Proposed

=0.4 Proposed

=0.6 Proposed

=0.8 Proposed

6 8 10 12 140

0.05

0.1

1 2 3 4 50

0.05

0.1

0.15

0.2

0.25

0.3

0.35CC Usage per Cell Comparison

Rel

ativ

e F

requ

ency

Total # of deployed CCs/cell

=0.2=0.4=0.6=0.8Original

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

)1).(,(}{}{}{ jnSn LLDLULImbalance:


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.

0.2 0.4 0.6 0.8

0

-5

10

20

30

40

50

60

Value of (UL FPC)

Rel

ativ

e P

erfo

rman

ce (

%)

Proposed versus Original

Average Cell TP

5% Outage UE TP

1 2 3 4 50

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Total # of deployed CCs

Rel

ativ

e F

requ

ency

Multi UEs/cell

CCs/cell: =0.6

CCs/UE: =0.6

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.


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.


Thank You!

Questions?

[email protected]


Appendix with additional slides


Perfomance Results: ACCS UL @ 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.


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%

P0 ≈ -60 dBm and high α values [0.6 , 0.8] seem to be the most promising settings.

Documents

Soc Classification level 1© Nokia Siemens NetworksPresentation / Author / Date Enhanced Uplink Carrier Aggregation for LTE-Advanced Femtocells VTC Fall: