18 optimization of umts radio network parameters cases_ppt-62.ppt

8/10/2019 18 Optimization of UMTS Radio Network Parameters cases_PPT-62.ppt

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Optimization of UMTS Radio

Network Parameters cases

Zte university


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Content

Optimization of Handover Parameters (Case 1)


Optimization of Cell Reselection ParametersOptimization of Cell Radius

Optimization of HSDPA Performance (Case 1)


Optimization of Power Control Parameters


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3

Pilot Ec/Io of cell 1

time

Pilot

Ec/Io

Connect to cell 1 Event 1A Event 1C Event 1B

= add cell 2 = replace cell1 with cell 3 = remove



tt

t

Introduction of Soft Handover Algorithm


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Case Description

When the UE moves from thecoverage area on Shuqian

Road site (PSC: 436) to that

of Meihuacun Hotel site

(PSC:434), signals on

Shuqian Road site (PSC: 436)

deteriorate due to theblocking of the dual-deck

viaduct. However, the

Meihuacun Hotel site

(PSC:434) enters the active

set slowly for the highthreshold. Therefore, the

handover success rate is low.


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Adjustment Suggestion for Handover

Parameters

Adjust the handover threshold and Time to Trigger parametersof Event 1A and Event 1B: reduce the handover threshold andTime to Trigger parameters of Event 1A, so that cells withbetter signal quality can enter the active set as soon aspossible; raise the handover threshold and Time to Triggerparameters of Event 1B, so that cells within the active setwould be removed for sudden fading of signals.

Effect after the optimization:

After the optimization, cell 434 on Meihuacun Hotel site canspeedily enter the active set and cell 436 on Shuqian Road sitewould be removed from the active set due to the sudden fadingof signals. Drive test after the parameter adjustment shows thatthe success rate of handovers between Shuqian Road site andMeihuacun Hotel site is greatly improved.

Event Parameter Setting Before Optimization Setting After Optimization

Handover threshold 2dB 4dB

Time to Trigger 640ms 200ms

Handover threshold 5dB 7dB

Time to Trigger 640ms 1280ms

Event 1A

Event 1B


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Content








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Case Study (1)

The main serving cell of the UE is the third cell(SC53) of site BKC0074U, its Ec/Io is -9.83dB.


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Case Study (2)

As the UE moves on, the main serving cell changes to the third

cell (SC48) of site BKC0044U, its Ec/Io is -10.31dB. Cell SC53

of site BKC0074U is removed from the active set and enters

the monitoring set.


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Case Study (3)

After 1s, the signal quality of cell SC53 of site BKC0074U is stronger

than cell SC48 of site BKC0044U, and the Ec/Io of SC48 reaches -2.39dB. Cell SC48 reports to Event 1A and tries to enter the active set

again. At this moment, the pilot quality of the cell SC48 of site

BKC0044U is very bad, with its Ec/Io down to -21.05dB. The UE reports

to Event 1A, but cannot receive the handover command, then the call

drops.


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Optimization Solution

To avoid the condition that cell SC53 of siteBKC0074U cannot enter the active set after being

removed, the value of CellIndivOffset(utranCell) of

cell SC53 of site BKC0074U is changed from 0dB to

3dB to prevent the cell from being removed from the

active set.


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Verification of Optimization Effect (1)

The UE moves in the arrow direction in a call-hold mode, and its main serving

cell is cell SC53 of site BKC0074U.

Then the signal quality of cell SC53 of

site BKC0074U declines, with Ec/Io down

to -13.23dB, which is worse than that of

cell SC48 of site BKC0044U. Then, the

main serving cell of the UE changes to

cell SC48, but cell SC53 remains in the

active set.


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Verification of Optimization Effect (2)

In the end, the main serving cell of the UE changes back to cell SC53

as shown in the following figure, and no call-drop happens.


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Content








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Measurement Criteria for Cell Reselection

If Sx > Sintrasearch, the UE need not perform the intra-frequency

measurement.If Sx Sintersearch, the UE need not perform the inter-frequencymeasurement.

If Sintrasearch is not sent to the serving cell, the UE performs theinter-frequency measurement.

If Sx > SsearchRATm, the UE need not perform the measurementamong cells adopting different radio technologies.

If Sx


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Rs

Qmeas,s + Qhysts

RnQmeas,nQoffsets,n

The UE would sort all cells satisfying criteria S for cell selection based on their R values.

The optimal cell would have the highest R value. Within the Treselection threshold, if

the queuing order of a new cell is better than the current serving cell of the UE, and the

UE has been camped in this serving cell for more than 1s, then the UE would select

this new cell as its serving cell.

Cell Reselection Criteria

Cell queuing criteria R:

Rs: R value of the serving cell

Rn: R value of neighbor cells

Qmeas: measured value of the cell signals (for FDD cells, CPICH Ec/No orCPICH RSCP is adopted)

Qoffset1s,n: offset value between two cells (used when Qmeas of FDD cells isset to CPICH RSCP)

Qoffset2s,n: offset value between two cells (used when Qmeas of FDD cells isset to CPICH Ec/No)

Qhyst1s: hysteresis value (used when Qmeas of FDD cells is set to CPICHRSCP)

Qhyst2s: hysteresis value (used when Qmeas of FDD cells is set to CPICH

Ec/No) Treselection: value for the cell reselection timer


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Inter-RAT Reselection (Case 1)

Case Description

Wide coverage of 2G network: Frequent 2G/3G Ping-ponghandovers occur at the boundary of the 3G coverage area.

Case Study

Check all parameters of the 2G network. For all GSM cellsconfigured with 3G neighbor cells, set their Qsearch_Iparameters to 7, FDD_Qmin to 0, and FDD_Qoffset to 0.Qsearch_I=7 means that the inter-RAT measurement isperformed unconditionally. FDD_Qmin represents the signalquality of WCDMA cell, and works as one of the judging criteriafor cell reselection. For FDD_Qmin=0, 0 is a logic value, andthe corresponding absolute value is Ec/N0=-20dB.

In the 3G network, Qqualmin=-18, SsearchRAT=2, and

Qqualmin+ SsearchRAT=-16dB. Severe Ping-pong handovers exist within the GSM network,

the signals jitter greatly.

For 2G/3G co-site and co-antenna, the cell edges of 2G and3G cells overlap.


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Inter-RAT Reselection (Case 2)

Solution

Set FDD_Qmin of the corresponding 2G cells to 7, and thecorresponding absolute value is -12dB. Then the ping-pongeffect is solved.

Optimization Criteria

The cell reselection criterion at the 2G side must ensure thatwhen the UE is handed over to the 3G network, the signalquality of the 3G cells can support the UE. In this case, the cellreselection criterion is set to -12dB.

In the 3G network, Qqualmin=-18, SsearchRAT=2, andQqualmin+ SsearchRAT=-16dB. This setting ensures that theUE remains in the 3G network when 3G cells are available.

The reselection criterion changes the serving radius of the cell

to a certain degree. Thus, this parameter must be setreasonably.

Certain margin must be reserved for the bi-directionalreselection threshold to avoid the ping-pong effect. (In thiscase, the margin is 4dB.)


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Content








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Case Description

The RRC establishment success rate for the first cellof site PHGV is low. Usually less than 50% of the

RRC establishments are successful.


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Case Study

We trace the PMS measurement on the OMC, andthen we find that signaling of radio link addition

failure exists. Then it is found out that the cell radius

is set to 40km. In this condition, large amounts of UL

resources are consumed.


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Setting of Cell RadiusParameter name (Preamble Detection

Threshold, T) [dB]

Constant Value

[dB]

Pp-m

Block Size=1*168 Block Size=1*360

Cell radius

TTI=20ms

Message

Dual-antenna -24 -21 -2 1

Single-antenna -21 -18-2 1

TTI=10ms

Message

Dual-antenna -24 -21 1 4

Single-antenna -21 -181 4

Cell radius

TTI=20ms

Message



TTI=10ms

Message



Cell radius

TTI=20ms

Message



TTI=10ms

Message



Cell radius

TTI=20ms

Message

Dual-antenna -21.5 -19 -2 1

Single-antenna -18.5 -16-2 1

TTI=10ms

Message

Dual-antenna -21.5 -19 1 4

Single-antenna -18.5 -161 4

Note: Change the preamble detection threshold and initial TX power of the UE accordingly when changing the cell radius.


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Processing Procedure & Result

Set this parameter to 5km in urban, 15km in theedges, and 40km for isolated sites or sites providing

coverage for highways. Check the KPIs after the

changes, the RRC establishment success rate for

the first cell of site PHGV is greatly improved.

Begin time

Time

Granularity Cell Name Cell ID

RRC

Establishment

Success Rate

(Service)

Radio

Access

Success

Rate

2009-4-5 1 Week PHGV_Cell1 15401 56.66% 56.54%

2009-4-12 1 Week PHGV_Cell1 15401 38.91% 38.89%

2009-4-19 1 Week PHGV_Cell1 15401 99.43% 99.40%2009-4-26 1 Week PHGV_Cell1 15401 99.81% 99.80%

2009-5-3 1 Week PHGV_Cell1 15401 94.77% 93.79%


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Experiences

Cell radius would influence the UL coverage. The larger cell

radius is set, the larger the UL coverage and the search

window will be. Meanwhile, the consumed resources would

also increase. Therefore, the setting of cell radius would have

greater impacts on the system performance. The cell radius

must be set based on specific radio environment.

At the initial stage of the network construction, the number of

subscribers is small, then the cell radius can be set to a large

value to ensure the coverage. For network under commercial

operation, the site spacing becomes small. Under this condition,

a large cell radius would become meaningless, and it should

be adjusted based on the network construction condition. Notethat the random access parameter should be changed

accordingly.


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Content








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MPO Description

Parameter name HS-PDSCH Measurement Power Offset (dB)

Abbreviated name MeasPwrOffset

Description This parameter indicates the assumed HS-PDSCH power

offset relative to PCPICH/S-CPICH power used for CQImeasurement

Range and Step -613dB step 0.5 dB

Unit dB

Default Value 6


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MPO Adjustment and Testing Area

The test object is Cluster 11, MPO is changed from6 to 8, and the testing route is shown below:


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RSCP before and after Adjustment (1)

Before

After


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RSCP before and after Adjustment (2 )

Before

After

Best Aggr RSCP

0

10

20

30

40

50

0

500

1000

1500

20002500

3000

3500

4000

4500

5000

P er ce nt (% ) C um _N um be r

Percent(%) 20.82 45.01 27.85 5.95 0.37 0

Cum_Number 1984 4291 2654 567 35 0

(+INF, -

60.00) [-60, -70) [-70, -80) [-80, -90) [-90, -105) [-105, -INF)

Best Aggr RSCP

0

10

20

30

40

50

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Percent(%) Cum_Number

Percent(%) 26.15 43.37 23.98 6.29 0.21 0

Cum_Number 2444 4054 2241 588 20 0

(+INF, -

60.00) [-60, -70) [-70, -80) [-80, -90) [-90, -105) [-105, -INF)

The comparison shows that MPOadjustment has little impact on

RSCP value.


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EC/IO before and after Adjustment (1)

Before

After


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EC/IO before and after Adjustment (2)

Before

After

After adjustment, Ec/Io reduces.

The occupancy of the value larger

than -8dB changes from 58% to

40%.

Best Aggr Ec/Io

0

5

10

15

20

25

30

35

40

45

0

5001000

1500

2000

2500

3000

3500

4000

Percent(%) Cum_Number

Percent(%) 18.46 21.5 40.56 16.15 2.6 0.73

Cum_Number 1725 2010 3791 1510 243 68

(+INF, -

6.00) [-6, -8) [-8, -10) [-10, -12) [-12, -14) [-14, -INF)

Best Aggr Ec/Io

0

5

10

15

20

25

30

35

40

0

500

1000

1500

2000

2500

3000

3500

P er ce nt (% ) C um _N um be r

Percent(%) 27.9 30.12 33.37 6.98 1.24 0.39

Cum_Number 2659 2871 3181 665 118 37

(+INF, -

6.00) [-6, -8) [-8, -10) [-10, -12) [-12, -14) [-14, -INF)


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Average CQI before and after Adjustment (1)

Before

After


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HSDPA Throughput before and after Adjustment (1)

Before

After


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Content








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HSDPA Handover AlgorithmUE

Target

Node B

Serving

Node B

Serving

RNC

1.Measurement Report

1D 2.Decide to

Change Serving

HS-DSCH Cell

NBAP NBAP

NBAP NBAP

3.Radio Link Reconfiguration

Prepare

4.Radio Link Reconfiguration Ready

NBAP NBAP 5.Radio Link ReconfigurationPrepare

NBAP NBAP

6.Radio Link ReconfigurationReady

7.ALCAP Iub Data Transport Bearer Setup(HS-DSCH)

NBAP NBAP

8.Radio LinkReconfiguration Commit

NBAP NBAP 9.Radio Link Reconfiguration Commit

RRC

RRC

RRC

RRC

10.Physical Channel Reconfiguration

11.Physical Channel Reconfiguration Complete

12.ALCAP Iub Data Transport Bearer Release(HS-DSCH)


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Event 1D Triggering Condition

Event 1D indicates that there is a cell outside the active set, which has

better quality than the cells in the active set, i.e., the best cell in theband changes. Upon the receiving of Event 1D, soft handover (cell

outside the active set reports Event 1D and the link number in the

active set does not reach its maximum), soft replacement (cell outside

the active set reports Event 1D and the link number in the active set

reaches its maximum) will be triggered or the best serving cell will

change (for HS-DSCH/E-DCH channel). When the cell satisfies the

following formula, and Time to Trigger duration is long, UE will report

1D to RNC.

/2HCIOLogM10CIOLogM10 1dBestBestNotBestNotBest


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HSDPA Handover

Impact on Download Rate

There are mainly two aspects:

Handover punctuality

Handover frequency


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Handover Punctuality Impact on Download Rate

HS-DSCH related physical channels do not support

soft handover. HS-DSCH services consume

relatively greater code resources, and HS-DSCH

transmission is based on packet scheduling and

does not support multi-cell transmitting data to one

subscriber. Therefore untimely handover will lead tothe deterioration of HS-PDSCH quality and the

decrease of CQI value reported by the UE, which

will result in a deterioration of the download rate.

Ensuring the timely handover is important forHSDPA download rate optimization.


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Handover Frequency Impact on Download Rate

HSDPA does not support soft handover, and services will be

interrupted shortly if cell update and channel handover are

initiated. Frequent hard handover will change HSDPA

download rate and the throughput. Therefore, reducing hard

handover is a primary method to increase HSDPA download

rate.

Reducing hard handover number and increasing handover

punctuality is contradictory, thats why too frequent Event 1D

will cause Ping-pong effect and reduce the download rate.

Therefore, the optimization of handover parameters will make

HSDPA download rate reach the highest value, and handover

frequency and punctuality become reasonable.


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Event 1D Related Parameters

In order to know Event 1D triggering threshold

impact on HSDPA download throughput, in intra-

frequency measurement we change hysteresis

value and Time to Trigger value and keep other

parameter value unchanged, the existing network

parameters relating to 1D are shown in the followingtable:

Parameter Value

PS domain intra-frequency measurement

event 1D Time to trigger320ms

PS domain intra-frequency measurement

event 1D Hysteresis3

PS domain HSPA global variables T1d 0ms


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Areas where Parameters are Changed

Areas are mainly office buildings and high-level residence quarters,

where population is dense. The coverage of single cells in the testedareas is favorable, as shown below:


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Parameter Modification Items

Parameter Name 1 2 3 4 5

PS domain intra-frequency

measurement event 1D Time

to trigger

320 320 320 320 320

PS domain intra-frequency

measurement event 1D

hysteresis

2 3 4 5 7

Parameter Name 6 7 8 9 10

PS domain intra-

frequency measurement

event 1D Time to trigger

640 640 640 640 640

PS domain intra-


event 1D Hysteresis

2 3 4 5 7


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Testing Result and Analysis (1)

1 2 3 4 5 6 7 8 9 10

PS domain intra-

frequency measurementevent 1D Time to trigger

320 640 320 640 320 640 320 640 320 640

PS domain intra-


event 1D Hysteresis

2 2 3 3 4 4 5 5 7 7

Average throughput

4341.

48

4197.

46

4429.

41

4298.

98

4400.

24

4484.

39

4369.

02

4376.

62

4371.

57

4352.

93

Rate of values lower than1Mbps 8.16 7.55 5.23 6.96 5.83 5.39 6.27 7 6.39 5.62

Best cell change times 104 94 96 80 92 69 89 72 84 64

Rate higher than 69.7 66.84 68.02 67.9 71.49 73.23 71.7 71.89 70.39 69.19

CQI 25 24.34 25.05 24.46 24.66 24.8 24.6 24.8 24.53 24.35

[3600, 2000) 16.26 19.11 21.63 18.75 17.39 16.53 16.99 15.85 17.9 17.81

[2000, 1024) 5.88 6.5 5.12 6.39 5.29 4.85 5.04 5.26 5.32 7.38

[1024, 0) 7.61 6.04 4.42 6.03 5.22 5.15 5.51 6.13 5.26 5.08

[0, -INF) 0.55 1.51 0.81 0.93 0.61 0.24 0.76 0.87 1.13 0.54


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Testing Result and Analysis (2)

HSDPA Throughput&Event 1D parameter

8.16 7.55 5.23 6.96 5.83 5.39 6.27 7.00 6.39 5.62

104

94 96 92

69

89

72

84

6469.7

66.84 68.02 67.9 71.49 73.23 71.7 71.89 70.39 69.19

25.00

80

24.3524.5324.8024.6024.8024.6624.4625.0524.34

4341.48

4197.46

4429.414400.24

4484.39

4369.02 4376.62 4371.57 4352.934298.98

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

110.00

2-320 2-640 3-320 3-640 4-320 4-640 5-320 5-640 7-320 7-640Event 1D Hystereris in intra-measurement

Percent

%

4000.00

4100.00

4200.00

4300.00

4400.00

4500.00

4600.00

4700.00

4800.00

4900.00

5000.00

5100.00

AverageThroughput

Scale of less then 1Mbps Times of best cell change Scale of more then 3.6Mbps


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Test Comparison Result (1)

DT data shows that when hysteresis value is 4 and

Time To Trigger is 640ms, the performance is the

best: downloading rate is 4.484Mbps; handover

number is 69 which is a relatively small number;

average CQI value is 24.80 which indicates that it

has a good downlink service channel quality and thehandover is timely.


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Parameter 3 Parameter 4

Parameter

Modification

PS service intra-frequencymeasurement event 1D

Time to trigger

320 640

PS service intra-frequency

measurement event 1D

Time hysteresis

3 3

HSDPA

Average throughout 4429.41 4298.98

Rate of values lower than

1Mbps5.23 6.96

Best cell update number 96 80

Rate of values higher than 68.02 67.9

CQI 25.05 24.46

When configuring parameter 4, handover number is 80, but CQI reported by UE is 24.46,

and throughput is 4.29mbps, which indicate that the handover is unpunctual, and the

primary serving cell is not the best cell. When configuring parameter 3, handover number

is 96, but CQI reported by UE is 25.05, which indicate that the handover is punctual, and

the primary serving cell is the best cell, and the rate is higher than that of parameter 4.


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Parameter 1 Parameter 3 Parameter 6

Parameter

modification

PS domain intra-


event 1D Time to trigger

320 320 640

PS domain intra-


event 1D hysteresis

2 3 4

HSDPA

Average throughput 4341.48 4429.41 4484.39Rate of the value lower

than 1Mbps8.16 5.23 5.39

Best cell update number 104 96 69

Rate of the value higher

than69.7 68.02 73.23

CQI 25.00 25.05 24.80

Keep the primary serving cell with good coverage, because frequent

handovers will affect the throughput. When CQI is relatively low, less

handover number will lead to a higher rate.


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Handover

Impact on Download Throughput

To explain handovers impaction downloading throughput, we select parameter

1 (2320) and parameter 6 (4640) to be set in a small scenario to make acomparison.

In the area, the handover number of parameter 6 is smaller than that ofparameter 1, but throughput and CQI increase, which indicates that reasonablehandover number and area are good for throughput increment.

Average throughput is 4474.33Kbps and average CQI

is 25.22 (parameter 6)

Average throughput is 4352.98Kbps and average

CQI is 24.85(parameter 1)


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Parameter Configuration at Crossroads 1

Left Right

Para

Hysteresis 4 3

Time To Trigger 640 320

Throughput 4.157Mbps 4.256Mbps

CQI 23.97 25.34

If the parameter configuration is (4

640ms), the test shows that it brings a good result,but at crossroads, the testing result is not the best, and parameter configuration (3.

320ms) can bring good testing result.


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Parameter Configuration at Crossroads 2

Signals at the corner changes swiftly, and signalsare easily mutated, which requests UE to quicklyrespond to the change of signals. Comparativelysmall hysteresis and Time to Trigger can satisfy therequirement. As shown in the experimental result,CQI of configuration (3,320) is higher than that ofconfiguration (4, 640) , i.e., configuration (3,320) canbetter satisfy the quick handover requirements atcrossroads.

From above, conclusion can be made: handover

parameter configuration is closely related to theradio environment. Handover parameters shall bechanged according to the radio environment, thusnetwork optimization can achieve the best result.


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Experiences

The method to control handover number is to adjust Event 1D

triggering threshold. Through Event 1D threshold adjustment,handover punctuality can be guaranteed and handover

frequency can be reduced, and the target of HSDPA handover

optimization is reached.

From the test, we can see in dense urban area, hysteresis

value shall be set to 4 and Time To Trigger to 640ms.

Radio environment is varying. We shall configure the handover

parameters based on the actual environment to ensure that

UEs handover is performed at proper time and that the

download rate is the highest.


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Content



Optimization of Cell Reselection Parameters

Optimization of Cell Radius





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FACH Power Modification

In P project, RRC connection setup success rate is relatively

low. Take RNC203 to make a test, and change MaximumFACH Power (dB) from 1.0 to 2.5.


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RRC Connection Setup Success Rates

Make observance of RRC connection setup success

rate for four days, and find that 0.45% increase is

obtained, as shown below:


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Other Indicators - TCP

KPI November 10 November, 20

Maximum Cell TCP>95% 15 28

Average Cell TCP 18.50% 19.50%

Number of rejected services,

DCH downlink TCP limit

1884 2709

Average Cell TCP increases due to the increase ofthe number of the rejected TCP limit service.


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Other Indicators - Call Drop Rate

Call drops and little fluctuation of the traffic volume

is quite normal, as shown below:


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Conclusion and Suggestions

Case Conclusion:

Generally if FACH power is increased to 2.5dB, RRCconnection setup success rate is increased by 0.45%,and other indicators are quite normal.

Suggestions: 1. ACH power can be set too high, which will lead to

the waste of the downlink power resources and bringinterference to other radio links.

2. Its recommended that FACH power is not changed.

If RRC connection setup rate is comparatively low, tryincreasing FACH power gradually upon demands, andthe change of RRC connection setup success rateand other indicators shall be carefully observed at alltimes.


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18 optimization of umts radio network parameters cases_ppt-62.ppt

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