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Systems and Capacity Planning

GENERAL OPTIMISATION TIPS

Prepared By: Amol Kshirsagar

Approved By: Helen Jones

Approved By: Graham Webb

Document Reference: CR/GUIDE/0183Issue Number: 2.0

Date Issued: 16th May 2003

Document Version: V1

Priority: High



http://view1/ops/o&m/ntsrv/EricBSS/btsfcods.htm



Coverage · There are situations when statistics show that drops are due to Downlink quality, however this may

not always be the case as the drops may be due to poor coverage. In such cases you need to check the layer and layer threshold for the cell. We have SLM defined as Layer 1 with Layer Threshold of

89, 1800 Macro as Layer 2 with Layer Threshold of 87, you can reduce this value so that it willmake early handover to higher layer. You can try a value 80 for SLM, or 83 for 1800 macro. A

change of Layer Threshold will help when the cells are on different layers. If the cells are on thesame layer, then you need to change value of KOFFSET. Presently we have KOFFSET=0, you cantry KOFFSET -4 to make early handover for a particular cell pair. When raising the DT you need to put KOFFSETN=4. If the cells are on different BSCs, then for the cell that you are trying to make

early handover from you need to put KOFFSETN =4 and for the other (External) cell you need to

put KOFFSETP=4.

If the GPRS user is in a high interference area,you will see a high value for BLER and poor

GPRS Throughput.

ERIC_HANDO

VER_CELLPAI

R RLLHPRLNRP



Symptom Cause Action Impact on GPRS Script /VGis

Coverage

We know from trigonometry that Tanq

= h / DTo calculate the value of down-tilt: q = Tan-1 (h / D)But this method does NOT calculate the location of upper 3-db point.

To consider the location of the upper 3dB point of the vertical beam

STEP I: Decide distance D3. This would set a value the cell footprint.

STEP II: Calculate aa = Tan-1 (h / D3)

STEP III: The value of down tilt q = aa + (vertical beamwidth/2)

· Based on this new downtilt produce coverage plots and check the impact using the RPT to see whether it willsolve the problem. Discuss these changes with the C and T planner and if the changes are practical request that

the changes are made.

· If the cell is from lower layer, you can make early handover to higher layer. This can be achieved by changinglayer threshold .We have SLM defined as Layer 1 with Layer Threshold of 89, 1800 Macro as Layer 2 with Layer

Threshold of 87, you can reduce this value so that it will make early handover to higher layer. You can try a value

80 for SLM, or 83 for 1800 macro.

Drops due

to Uplink Signalstrength

Antenna /

feeder /hardware

problem

· There could be problem in the antenna or feeder. Check the ASC database for the condition of the feeder or anyinformation on the antennas. If there is no information about antenna or feeder condition, you can raise a Clarifycase to have antenna and feeders checked.

· Check Clarify to see if there is any open case for faulty hardware.

If the GPRS user is in a high

interference area, you will see ahigh value for BLER and poor

GPRS Throughput.

ASC

general gsm op tim is at ion tips

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