02 Ra47042en60gla1 Kpi Overview

LTE Optimization Principles [RL60] Module 03

Physical RF Optimization

1

© Nokia 2014 - RA RA47043EN60GLA0

Module Objectives

• After completing this module, you will be able to: to: • Describe how to detect interference by means of field mesurements • Give an overview on interference and coverage issues via performance measurement counters • Explain the impact of interference on peak throughput • Describe the relation of load and interference • Discuss the importance of interference analysis for the overall network performance

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Index

-

Detecting Detect ing inter interfer ferenc ence e using using field field measu measurem rement ents s Detect Det ecting ing inter interfer ferenc ence e and bad cover coverage age from from counte counters rs Dete De tect ctin ing g ove overs rsho hoot otin ing g cells cells Impact Imp act of of inter interfer ferenc ence e on peak peak thr throug oughpu hputt • idle/loaded other cell interference • PCI collision impact im pact in TD-LTE - PC PCII optim optimiza izatio tion n with with Op Opti timiz mizer er - Impa Impact ct of inter interfere ference nce on on LTE LTE networ network k perform performance ance – importance of physical RF optimization • Impact of network load • MIMO X-feeders • A trial example

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Detecting Interference – Indicators

• Three quantities • SINR • RSRQ • RSRP - Whi Which ch one one shoul should d be use used d for for drive drive test test analy analysis? sis?

5


Detecting Interference – SINR

• SINR measurem measurements ents can indicate indicate inter interferen ference ce areas, areas, but it doesn’t doesn’t necessari necessarily ly see all all interference sources: • Impacted by network load. l oad. Traffic Traffic in the neighboring cells will reduce serving cell SINR. • Depends on the measurement method (RS or SCH) and tool • Depends on PCI planning (RS SINR) • Results can be misleading!

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Detecting Interference – SINR • Example: SSS-CINR + RS CINR versus top-N RSRP

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© Nokia 2014 - RA47043EN60GLA0

Detecting Interference – RSRQ • RSRQ depends on network load, including own cell load

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Detecting Interference – RSRQ

• RSRQ depends on serving and neighbour cell load • Fluctuates quickly • Hence difficult to interpret results • Similar to Ec/N0 in 3G

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Detecting Interference – RSRP

• RSRP measurement with scanner is the most reliable way to detect areas with possible interference problems and bad dominance • Not impacted by network load • RSRP measurement appears to be consistent between UEs/scanners • The number of PCIs in e.g. 5 dB power window is a useful indicator - A scanner with good dynamic range and PCI tracking capability needed

Bad dominance

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SINR (worst case estimate) calculated from RSRP • Measured with PCTel MX scanner in TD-LTE network – RS-SINR, SCH-SINR, RSRP • Calculated SINR is worst case estimate for SINR (i.e.100% neighbor cell load). In TD-LTE it should be equal to SCH-SINR. 60

Calculated SINR goes very high in the locations where no neighbors are detected

40

20

Calculated SINR follows SCHSINR nicely in the most places

0 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 8 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 2 : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4 5 5 5 5 5 5 6 6 6 6 6 6 7 7 7 7 7 7 8 8 8 8 8 8 9 9 9 9 9 9 0 0 0 0 0 0 7 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 5 : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 8 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Average of LTE_Scan_RS_CINR_SortedBy_RSRP_0

-20

Average of LTE_Scan_SCH_CINR_SortedBy_RSRP_0 Average of Calc. SINR dB Average of LTE_Scan_RSRP_SortedBy_RSRP_0 -40

Calculated SINR (worst case) = RSRP_serving/

-60

(∑RSRP_others + Noise) -80

[Noise figure 9dB] -100

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Detecting Interference – Pilot pollution Counting PCIs less than XdB RSRP difference

• From drive test with test terminal. • Serving PCI vs. Top N PCIs • Less than 5dB difference to the serving PCI can be considered a potential interferer. • A common rule for antenna tilt optimization consideration: 3 or more PCIs inside 5dB window.

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Detecting Interference – Summary

•

Absolute SINR measurement values can’t be used as a reliable performance indicator. • Do not to blindly believe measured SINR values. • Relative SINR changes can be used as performance indicator, if the same measurement tool is used all the time.

• SINR measured from S-SCH and RS behaves differently depending on the interference situation (intra/inter eNodeB). • Detailed SINR measurement methods of the terminals and scanners are not known. • The most robust and reliable measurement quantity seems to be RSRP

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Index

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Detecting interference using field measurements Detecting interference and bad coverage from counters Detecting overshooting cells Impact of interference on peak throughput • idle/loaded other cell interference • PCI collision impact in TD-LTE - PCI optimization with Optimizer - Impact of interference on LTE network performance – importance of physical RF optimization • Impact of network load • MIMO X-feeders • A trial example

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Use Case

 A

BTS or a group of BTSs is having bad KPIs

• Q: Is this because of bad coverage, UL/DL interference or both? • How to analyze this from counters?

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Bad Downlink vs Good Downlink • Example from Live Network 70000000

CQI = 14 60000000 Data Sum of M8010C036 UE Reported CQI Level 00 Sum of M8010C037 UE Reported CQI Level 01

50000000

Sum of M8010C038 UE Reported CQI Level 02 Sum of M8010C039 UE Reported CQI Level 03

Good DL coverage

Sum of M8010C040 UE Reported CQI Level 04 Sum of M8010C041 UE Reported CQI Level 05

40000000

Sum of M8010C042 UE Reported CQI Level 06 Sum of M8010C043 UE Reported CQI Level 07 Sum of M8010C044 UE Reported CQI Level 08 30000000

Sum of M8010C045 UE Reported CQI Level 09

Fairly bad DL coverage (or DL interference)

20000000

Sum of M8010C046 UE Reported CQI Level 10 Sum of M8010C047 UE Reported CQI Level 11 Sum of M8010C048 UE Reported CQI Level 12 Sum of M8010C049 UE Reported CQI Level 13 Sum of M8010C050 UE Reported CQI Level 14 Sum of M8010C051 UE Reported CQI Level 15

10000000

0 100589 16


100953 BTS

Check CQI offset from LTE_5432b E-UTRAN Average CQI Offset

Bad uplink vs good uplink Data

UE Power Headroom: -15dB <= PHR < -13dB.

500000

450000

UE Power Headroom: -1dB <= PHR < +1dB.

Sum of M8005C055 UE Power Headroom for PUSCH Level 2

Open-loop UL PC used

400000

Sum of M8005C056 UE Power Headroom for PUSCH Level 3 Sum of M8005C057 UE Power Headroom for PUSCH Level 4 Sum of M8005C058 UE Power Headroom for PUSCH Level 5

350000


300000

Sum of M8005C060 UE Power Headroom for PUSCH Level 7 Sum of M8005C061 UE Power Headroom for PUSCH Level 8

250000

200000


Fairly good UL coverage

Fairly bad UL coverage

150000

Sum of M8005C062 UE Power Headroom for PUSCH Level 9 Sum of M8005C063 UE Power Headroom for PUSCH Level 10 Sum of M8005C064 UE Power Headroom for PUSCH Level 11 Sum of M8005C065 UE Power Headroom for PUSCH Level 12

100000

Sum of M8005C066 UE Power Headroom for PUSCH Level 13 50000

Sum of M8005C067 UE Power Headroom for PUSCH Level 14 Sum of M8005C068 UE Power Headroom for PUSCH Level 15

0 100589 17

100953


BTS

Sum of M8005C069 UE Power Headroom for PUSCH Level 16 Sum of M8005C070 UE Power Headroom for

PUSCH SINR, PUSCH RSSI Measurement • PUSCH RSSI and PUSCH SINR measurement can be used to detect UL coverage and UL interference problems • Interpretation of counter values depends on UL PC settings • Measurements are not correlated

SINR

UL CL PC upper SINR thrshld Ideally all samples are in this box

bad UL coverage

UL CL PC lower SINR thrshld UL interference RSSI

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PUSCH SINR, PUSCH RSSI Measurement • Noise rise impacts SINR versus RSSI

Interference drives counter samples to this region 19


PUSCH SINR, PUSCH RSSI measurement • Impact of power control settings on PUSCH SINR UL tx pwr too high, generates interference

UL tx pwr too high, generates interference

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UL interference and noise rise •PUSCH RSSI and SINR are measured only when ther e is UL traffic •There are no dedicated counters for UL noise rise measurements. Methods for UL noise rise detection: Calculating UL noise rise from PUSCH RSSI and SINR counters. -

Definition, NR = (I+N)/N, N is thermal noise, I is interference

-

Assumption: PUSCH signal power = PUSCH RSSI

-

Calculation in linear: PUSCH_RSSI/PUSCH_SINR/N = PUSCH_RSSI/[PUSCH_RSSI / (I + N) ]/N = (I+N)/N = NR

Measuring UL noise rise with TTI trace -

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Interference power for PUSCH


UL external interference analysis with TTI trace

• TTI trace analysis can be used to verify impact of external interference. • TTI trace results are matching to spectrum analyser measurements.

Lower half-band has low SINR and lot of HARQ NACK and DTX

constant power narrow-band interference

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Fairly clean portion of spectrum

Second dirty portion of spectrum

10MHz Bursty interference over lower half-band

-86dBm interference power

Bad coverage analysis from HO counters M8015 - Neighbour cell HO measurements

•

Visualize HO cell pairs with poor HO performance

•

In the case of poor performance to all neighbors in one directions 

Coverage problems or unsuitable HO parameters (A3 offset)

Example: Cell pairs with HO SR<80% & HO Att>10 shown

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Content Detecting interference using field measurements Detecting interference and bad coverage from counters Detecting overshooting cells Impact of interference on peak throughput • idle/loaded other cell interference • PCI collision impact in TD-LTE - PCI optimization with Optimizer - Impact of interference on LTE network performance – importance of physical RF optimization • Impact of network load • MIMO X-feeders • A trial example • -

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Overshooting cells • Cells with too large or largely distributed dominance area. • Will cause increased interference to other cells • Can collect excessive amount of traffic. • How to detect overshooting cells? • Drive tests • Analyzing HO performance and neighbor cell measurements from drive test logs. • Counters • Cell pair HO analysis with inter site distance information. Indicating HOs to cells with long inter site distance. • Timing Advance trace • Cell Timing Advance trace analyzes to find long distance users.

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Overshooting cells analysis from HO counters Optimizer - Visualize adjacencies and HO KPIs •

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To find long distance cells pairs with HO attemps -> overshooting cell detection.


Overshooting cells analysis from HO counters Other tools to analyse Neighbour cell HO counters •

M8015 - Neighbour cell HO measurements

•

Visualize long distance HO cell pairs (e.g. >10km)

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Index

• -


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RF Peak Throughput under Neighbour Cell Interference

• Measuring peak MIMO dual-stream throughput in the field can be tricky because of interference • An idle cell produces common channel + RS interference to impact peak throughput  need to find good interference-free measurement spot. Inter-site cell border, non-frame synchronized cells

Intra-site cell border, framesynchronized cells

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Impact on Peak Tput from Idle Neighbour Cell Interference • Measurement example #1, Samsung terminal, 20MHz. Inter-site and intra-site neighbour are unloaded (no PDSCH traffic) PHY tput, CINR, RSRP

All neighbour cells attenuated 50dB

120

-50

-60 100

B d R

Inter-site interference, adjacent site cell about 5 dB weaker RSRP than serving cell

Intra-site interference, adjacent cell about 5 dB weaker RSRP than serving cell

-70

80 NI

-80 C , c e

Data m

s/ B st i

60 b a

d

Average of Phy DL TP(Mbps) R

Average of SCell-CINR R

Average of SCell-RSRP

-90

g S

P

e M t u

-100 pt

40 Y H P

-110 20 -120

0 /2010 09:53:02.801 30

06/11/2010 09:54:45.317


-130 06/11/2010 09:56:29.840

06/11/2010 09:58:14.347

Time

All neighbour cells

Intra-site neighbour frame-synced, no RS interference

Impact on Peak Tput from 100% Loaded Neighbour cell

• Measurement example #2, Samsung terminal, 20MHz. Unloaded and 100% loaded PHY tput, CINR, RSRP

inter-site neighbour

Neighbour site cell attenuated 50dB -50

120 UDP download 100Mbps

neighbouring site cell in idle mode

100

B

Neighbour site cell about 6 dB weaker

80 d

-60

-70

R IN

-80 C , c

60 e /s

Data m B

st i

d

Average of Phy DL TP(Mbps) R

Average of SCell-CINR R

Average of SCell-RSRP

-90 b a g e

S

40 M

P

t u

-100 pt Y H

20 P

-110

0 1 0

0 2

1

.

0 2

1

1

: 1

2

-20

/ 0 6 1

0

:

/ 0 6 0

0 9

1 0

1 0

0 1

3

.

2

5

:

5 0

1

0 1

0 1


0

1 1

1 6

1

0

:

6 0 1

Time

0

6 1

0

: 0

1

0

1

1

1

1

0

0

-130

/ 0

6 0

:

:

9 /

0 6

0

:

2

:

8 /

7 /

1

1 0

2 3

:

7 /

.

6 /

1

1 0

0

2 4

:

7 /

0 6

0

:

1

1

/

5

:

4

.

5 /

4 1

0

2

/ 0

: 1

4

0 4

.

-120 4

3 1

0

2

/

0 4

.

4

6

3 1

0

2

/

0 9

.

4

0

2 1

0

2

6

0

0 9

.

3

4

1 1

0

2

:

0 4

.

3

6

0

:

2

6

0

:

2

8

1 1

9

.

Neighbour / / site cell / 4 3 2 1 : 1 : 1 : 1 3 1 weaker 4 1 5 about 1 dB / / / 0 0 0 2

/

1

0 8

0

2

/

8

9 1

0 0

0

0 3

. 2

2

8 1

8 0

31

5

1 6

1

0

: 0

1

0

:

Typical SINR= 15-17 dB at inter-site cell border, unloaded neighbour.

TD-LTE: Impact of Idle Mode Interference on Tput • UE FTP downloading in the middle of two sectors of the same site, RSRP from both cells ~ -70dBm • First the second cell is off (rebooting), then comes on-air but no traffic carried (only common channels transmitted)

P R S R v r e S

t u p t

R N I S 32

34Mbps vs 15Mbps


Neighbour cell switched on

Index

• -


33


Impact of PCImod3 Collision on Tput, TD-LTE •

Case: UE at the border of two cells who have the same PCImod3, RSRP from both cells = -67dBm in both measurement cases (only PCI changed)

•

NSN 7210 TD dongle, 2.6GHz, 10MHz bandwidth 16 14 12

s 10 p b M , 8 t u p t

no PCImod3 collision PCImod3 collision

6 4 2 0 1

3

5

7

9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 seconds

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PCImod3 Collision Impact, 2.3GHz@20MHz, Qualcomm TD-LTE Dongle Example PCI= 88/90

PCI= 87/90 (mod3 collision)

RSRP = -97dBm

RSRP=-101dBm

SINR = 12dB

SINR=2dB

Tput = ~21Mbps

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Tput = ~15Mbps

Tools for Parameter Planning - NetAct Optimizer • PCI planning • PRACH planning • UL DM RS sequence planning is a future feature candidate - Atoll • Automatic PCI planning supported - Asset 7 • PCI planning - Alpha (NSN-internal tool) • PCI planning • UL DM RS planning - MUSA (NSN internal) - post processing - Daisy (NSN-internal tool) • PCI planning

36


Index

• -


37


Optimizer- detecting PCI collisions

Confusion: cell’s neighbors or neighbors’ neighbors have the same PCI

38


Collision: direct neighbors have the same PCI

Visualizing the Collisions on Map

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Optimizer- detecting PCI violations

Violation types: PCI reuse distance is too small Group-wise allocation rule is violated Forbidden PCIs were allocated Frequency rule violated: the frequencies don’t use identical PCIs

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Minimum Reuse Distance settings

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Allocating New PCI Codes

New allocation: allocate totally new PCIs according to the settings. Fix collisions and violations: fix collisions taking the settings into account. The collisions are corrected only within the selected scope.

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Allocation Results The new PCI values will be highlighted with blue color.

43


PCI reuse visualization

44


PCI code distribution histogram

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Index

• -


46


RF Optimization

• Basic physical RF optimization is very important (of course..) • Clear cell dominance areas, minimize cell overlapping • Avoid sites shooting over large areas with other cells • “Can’t fix bad RF by tuning parameters” • Antenna tilting and antenna placement has big impact on other cell interference!! • What is the impact on network performance?

47


Impact of DL load, 0% vs. 70% DL load

•The same drive test route driven twice, with the same UE setup -

LTE819: DL Inter-cell Interference Generation to generate load

-

0% load versus 70% DL load

-

Compare distribution of throughput and SINR, the same drive test route twice with and without load

-

20MHz OL-MIMO, FTP download, 1UE inside the car, Samsung BT-3710, UE-internal antennas

-

average throughput is 58% better without interference

-

Selection of drive test route strongly affects result, here only results for one drive test route Empirical CDF 1

0.9

0.9 70% OCNG 0% OCNG

0.8

F D C

Empirical CDF

1

0.8

0.7

0.7

0.6

0.6

0.5

Mean = 36Mbps

0.4

Mean = 57Mbps

48

F D C

0.5 0.4

0.3

0.3

0.2

0.2

0.1

0.1

0

70% OCNG 0% OCNG

0

10

20

30

40 50 60 70 [Mbps] © Nokia 2014 -throughput RA47043EN60GLA0

80

90

100

0 -5

0

5

10 15 SINR [dB]

20

25

30

Index

• -


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MIMO X-Feeder

Assuming: •

ANTL-1 and ANTL-7 are defined active for sector 1

•

ANTL-3 and ANTL-9 are defined active for sector 2

•

Then the configuration in the upper picture is correct

•

The configuration in the lower picture is incorrect and results in sectors overlapping with each other  bad throughput due to interference

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MIMO x-feeder, Example 1 Scanner Measurement

242

241

51


Sectors 241 and 242 equally strong in area where 242 should dominate

MIMO X-Feeder Example 2 Scanner Measurement

22 21 Site (PCIs=21,22) PCIs

52


MIMO X-Feeder Example 2, Scanner measurement Corrected Feeders

21 PCIs

53


22 Site (PCIs=21,22)

Index

• -


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Antenna tilt tuning example (1/3) A reference cluster in Korea • Drive test measurements • SINR before and after tilt tuning.

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Antenna tilt tuning example (2/3) A reference cluster in Korea • Drive test measurements • CQI before and after tilt tuning.

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Antenna tilt tuning example (3/3) A reference cluster in Korea • Drive test measurements • HO attempts before and after tilt tuning.

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Summary • Building good dominance is essential for network performance – also in LTE !!! • “Can’t fix bad RF with parameters…” • …except by fixing missing neighbours

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02 Ra47042en60gla1 Kpi Overview

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