Cell Outage Compensation in LTE - FP7 2015-02-04آ  3/14 Mehdi Amirijoo, Ericsson Introduction A...

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Transcript of Cell Outage Compensation in LTE - FP7 2015-02-04آ  3/14 Mehdi Amirijoo, Ericsson Introduction A...

  • FP7 ICT-SOCRATES

    Presented by Mehdi Amirijoo

    Ericsson Research, Ericsson AB

    FP7 SOCRATES final workshop

    Karlsruhe, Germany

    22 February 2011

    Cell Outage Compensation

    in LTE

    Contributors: Remco Litjens (TNO ICT), Ljupco Jorguseski (TNO ICT), Lars Christoph Schmelz (NSN)

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    Outline

    � Introduction

    � Solution

    � Simulation assumptions

    � Simulation results

    � Conclusion

    � For more information refer to D5.9 Section 8.6

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    Introduction

    � A cell/site does not transmit any radio signal

    � Reasons for outages:

    – software and hardware failures (radio unit, antenna etc),

    – external failures such as power supply or network connectivity

    � Outages result in loss of coverage

    – customer complaints and dissatisfaction

    – loss of potential revenues

    � Automatic mitigation of coverage loss

    � Challenges:

    – Timely response

    – Handling tradeoffs between coverage and quality

    – Observing coverage

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    Solution

    Measurements

    CompensationOperator policy

    Control parameters

    Detection

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    Solution – Operator Policy

    � Manage tradeoff between coverage and quality

    � Quality Q: Xth-percentile of UE throughput

    – e.g., 10th-percentile UE throughput

    � Network is dimensioned according to a cell-specific nominal target

    quality QT

    � Nominal target quality may not be satisfied during an outage

    � Compensating cells have a cell-specific outage target quality Q’T

    Example: maximize coverage subject to Q ≥ Q’T

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    Solution – Controllability & Observability Study

    � Control parameters: – Reference signal power, tilt, UL power control parameters

    � Scenarios – Site density and load – Operator policy

    � Performance metrics – Coverage probability (SINR) – Quality (uplink/downlink user throughput)

    � Controllability result: – UL coverage is the limiting factor in the studied scenarios (and simulation

    assumptions) – Tilt and UL target received power are most effective in improving coverage

    � Coverage observability is one of the main challenges – Coverage probability estimation – Timely estimation – Use X-maps

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    Solution – Algorithms

    � Algorithm tunes

    – target received power spectral density (PSD) in UL denoted P0 – antenna tilt

    � UL transmit PSD T is defined as

    where

    – P0 = SNRtarget × N0 – N0 is the noise PSD

    – PL is the path loss, including shadowing and antenna gains

    – α is the path loss compensation fraction

    � Decreasing P0 will decrease the spectral efficiency leading to

    – more resource consumption per user

    – more contention among the users and lower quality

    α PLPT ×=

    0

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    Solution – Algorithms

    � By decreasing P0 in the cells around the outage site we

    – decrease the UL power by users in these cells

    – thereby decrease the UL inter-cell interference

    – thereby extend UL coverage

    � If Q > Q’T (DL & UL)

    P0(k) = max(P0_MIN,P0(k-1) - δ)

    else

    P0(k) = min(P0_MAX,P0(k-1) + δ)

    Received signal power

    Distance from base station

    High P0

    Medium P0

    Low P0

    Power-limited UEs

    Reduction of UL inter-cell interference

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    Simulation Assumptions

    � Static snapshot simulator

    � Network with 57 cells (wrap-around)

    � Propagation:

    – Okumura-Hata (urban)

    – Shadow fading

    � UEs distributed uniformly

    � Truncated Shannon model

    � 3D antenna pattern (3GPP)

    � SISO system

    � User requested data rate

    – DL = 1 Mbps

    – UL = 250 kbps -1000 -500 0 500 1000

    -1000

    -800

    -600

    -400

    -200

    0

    200

    400

    600

    800

    1000

    -140

    -130

    -120

    -110

    -100

    -90

    -80

    -70

    Pathgain [dB]

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    PRE-OUTAGE SITUATION POST-OUTAGE SITUATION WITHOUT COMPENSATION

    U P

    L IN

    K U

    S E

    R

    T H

    R O

    U G

    H P

    U T

    C O

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    IL IT

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    H P

    U T

    POST-OUTAGE SITUATION WITH OPTIMISED P0

    PRE-OUTAGE SITUATION POST-OUTAGE SITUATION WITHOUT COMPENSATION

    U P

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    POST-OUTAGE SITUATION WITH OPTIMISED P0

    PRE-OUTAGE SITUATION POST-OUTAGE SITUATION WITHOUT COMPENSATION

    U P

    L IN

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    H P

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    POST-OUTAGE SITUATION WITH OPTIMISED P0

    Simulation Results – Controllability Result (P0,High Load)

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    Simulation Results – Algorithm (P0,High Load)

    Outage

    Start of compensation

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    Simulation Results – Algorithm (P0,High Load)

    Outage target quality

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    Conclusion

    � Outages result in customer dissatisfaction & loss of potential revenues

    � Solution that alleviates negative impact of outages considering practical limitation (coverage observability)

    � Antenna tilt and UL power control parameters have shown to be most effective

    � Operator specifies tradeoff between quality and coverage

    � Solution adjusts tilt and UL power control parameters in order to balance coverage and quality

    � Solution shows that a large portion of the users can be recovered

    � Future work: – Develop solutions that can translate a variety of operator policies into algorithms

    – Combination of several control parameters

    – Observability of coverage using X-maps

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    Contact

    Mehdi Amirijoo, Ericsson Research, Ericsson AB

    E-mail: mehdi.amirijoo@ericsson.com

    Phone: +46107115290