FP7 ICT-SOCRATES

Automatic Cell Outage

Compensation

M. Amirijoo (Ericsson),

R. Litjens, L. Jorguseski (TNO ICT),

L. C. Schmelz (Nokia Siemens Networks)

WWW.FP7-SOCRATES.EU

2/18

Mehdi Amirijoo, Ericsson

Background

� Reasons for outages, e.g.:

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

– external failures such as power supply or network connectivity

� Frequency of outages depends on, e.g.,

– operator policy (level of hardware redundancy)

– geographic location (e.g weather condition)

– maturity and type of technology

– power supply quality (probability of electricity outages)

� Outages

– last from several hours to days

– result in loss of coverage

– customer complaints and dissatisfaction

– loss of potential revenues

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3/18

Mehdi Amirijoo, Ericsson

Solution

MeasurementsDetection

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4/18

Mehdi Amirijoo, Ericsson

Solution

Measurements

CompensationOperator policy

Control parameters

Detection

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5/18

Mehdi Amirijoo, Ericsson

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 nominal target quality QT, e.g.,

– QT,DL = 256 kbps

– QT,UL = 128 kbps

� Nominal target quality may not be satisfied during an outage

� Compensating cells have an outage target quality Q’T, e.g.,

– Q’T,DL = 128 kbps

– Q’T,UL = 64 kbps

Maximize coverage such that Q ≥ Q’T

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6/18

Mehdi Amirijoo, Ericsson

Solution – Algorithms

� UL coverage is the limiting factor

� Extensive sensitivity analysis

– control parameters, scenarios, etc

� Control parameters:

– uplink target received power P0

– antenna downtilt

WWW.FP7-SOCRATES.EU

7/18

Mehdi Amirijoo, Ericsson

Solution – Definition of P0

� Used in open-loop power control

� P0 is the target received power in UL

� UL transmit power spectral density (PSD) is

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

αPLPPSD ×= 0

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8/18

Mehdi Amirijoo, Ericsson

Solution – Tuning of P0

� Let k denote interation number

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

– decrease the UL inter-cell interference

– improve the UL coverage

� If QDL > Q’T,DL AND QUL > Q’T,UL then

P0(k) = max(P0_MIN,P0(k-1) - δ)

else

P0(k) = min(P0_MAX,P0(k-1) + δ)

WWW.FP7-SOCRATES.EU

9/18

Mehdi Amirijoo, Ericsson

Solution – Tuning of P0

� P0_MIN is set such that UL SINR is sufficient for lowest MCS

� Let SINRmin be the minimun tolerable UL SINR

� Received signal power must satisfy

� Base max UL interference Imax on historic measurements

� In practice introduce an UL interference margin IM

)()(max0min0max0min

INSINRPINSINRS +≥⇒+≥

)(max0min0 M

IINSINRP ++≥

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10/18

Mehdi Amirijoo, Ericsson

Solution – Compensation Network

� Cells that tune P0 are referred to as the

compensation network (CN)

� CN can be derived using UE measurements during nominal operation

� Number of cells in CN is a tradeoff

between

– Coverage improvement

– Overall quality degradation

� Consider the blue cells as the

compensation network (CN)

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11/18

Mehdi Amirijoo, Ericsson

Simulator and Scenario

� Static snapshot simulator

� Network with 57 cells

� Propagation:

– Okumura-Hata (urban)

– Shadow fading

� UEs distributed uniformly

� Channels/signals:

– Reference signal

– DL data channel (”PDSCH”)

– UL data channel (”PUSCH”)

� Truncated Shannon model

� 3D antenna pattern

� SISO system

-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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12/18

Mehdi Amirijoo, Ericsson

Simulator and Scenario

� Data traffic characterised by requested data rate DL = 1 Mbps and UL = 250 kbps

� Quality/Coverage network planning targets– Coverage > 98 %

– 10th-% DL Throughput > 256 kbps

– 10th-% UL Throughput > 128 kbps

� Loads– High load: max load such that coverage/quality targets are satisfied (47 UEs/cell)

– Medium load: 50 % of high load (23 UEs/cell)

– Low load: 1 UE/cell

� Capacity driven layout– ISD = 500 m

– Antenna downtilt = 15º

– P0 ~ -96 dBm

– Consider high load, medium load, low load

� Coverage driven layout– ISD: max ISD such that coverage/quality targets are satisfied => ISD = 2200 m

– Antenna downtilt = 5º

– P0 ~ -114 dBm

– Consider low load

� Show results for capacity driven layout with high and medium load

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13/18

Mehdi Amirijoo, Ericsson

Simulation Results

Compensating cell (blue)

Cell in outage (red)

Compensated coverage hole (grey)

10th-perc DL throughput [Mbps] (averaged over compensating cells)

10th-perc UL throughput [Mbps] (averaged over compensating cells)

Increase in number of served UEs (relative to no compensation)

Control Parameter P0

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14/18

Mehdi Amirijoo, Ericsson

Simulation Results – High Load

Outage

Start of compensation

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15/18

Mehdi Amirijoo, Ericsson

Simulation Results – High Load

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16/18

Mehdi Amirijoo, Ericsson

Simulation Results – Medium Load

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17/18

Mehdi Amirijoo, Ericsson

Conclusion

� Outages result in customer dissatisfaction & loss of revenues

� Operator specifies tradeoff between quality and coverage

� Our solution can improve coverage during an outage

� Future work:

– Algorithms for tilt tuning

– Compensation network based on, e.g., UE measurements

– Observability of coverage

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18/18

Mehdi Amirijoo, Ericsson

Contact

Mehdi Amirijoo, Ericsson Research, Ericsson AB

E-mail: mehdi.amirijoo@ericsson.com

Phone: +46107115290