brighton 3goverview final

8/12/2019 Brighton 3GOverview Final

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BrightonOptimisation


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3G Evaluation for Brighton-Driven on 05-MAY-2006

Summary

A Dual Mode Drive Survey performed over 1 - 5 May 2006 in Brighton, collected log files showing the following:

3 DroppedCalls0 Blocked CallsAll the drops were in residential areas. Coverage throughout the CBD was good.

The 1stdropwas due to overshooting of cells D57791 and D35062 located on the opposite side of the bay and addedincorrectly as neighbours to the cell G00882. The TEMS mobile handed into a foreign cell and had no relationship to return to

the original server. It is recommended that the overshooting cells be down tilted from 0 > 6deg and removed as neighbours to

the serving cell G00882.

The 2nddropappears to have been due to interference as RxQ was poor in spite of RxSS being good. The source of thisinterference only seem to be over a small area in which the TEMS mobile happened to be travelling very slowly, causing the

downlink RLT timer to elapse after 24 SACCH frames.The source of the interference cannot be traced yet, but a freq retune of

the server might resolve the issue. The drop rate of the server is only about 0.4%, insinuating that most of the traffic either dont

use that route or travel at sufficient speed to prevent RLT timeout. It is also suggested that the target neighbour G11931 be

uptilted by 2deg in order to increase the measurement window in favour of the target neighbour, prior to handover.

The 3rddropwas caused by a combination of crossed feeders between cells G32141 and G32143, and a clash of BCCHfrequencies between G11942 and G32141. This drop should be fixed by retuning either of the mentioned cells BCCHs, and by

investigating and if necessary, repairing site G3214s crossed feeders.

About 3003G and 2G neighbour additionshave been requested. Their handover stats will be analysed after a two weekperiod after which a neighbour culling exercise will follow, deleting unused neighbours and speeding up handover processes.


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Light Grey Demarcated Area = Populated AreasDark Grey Area RED Polygon) = CBD

Live 3G Sites

Central Business Area


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Upcoming 3G Sites



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Live 2G Sites



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Upcoming 2G Sites



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1stPart of Dual Mode Drive Survey showing RSCP


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2ndPart of Dual Mode Drive Survey showing RSCP


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3rdPart of Dual Mode Drive Survey showing RSCP


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4thPart of Dual Mode Drive Survey showing RSCP


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Predicted 3G RSCP Coverage


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Predicted 3G EcNo Coverage


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Predicted 2G RxSS Coverage


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Predicted 2G RxQ Coverage


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Serving Cell

1sthand over to site G5779with ET=0 and MT=0 7

2nd hand over to site G35062 withET=0 and MT=0

Analysis of 1stDropped Call


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Analysis:

Drop call was encountered in this region when the serving cell G00882handed over to a neighbour cell,

D57791, being nearly 20kms away.

The call was then handed to D350621,which was even further away, but had no neighbour relationship

back to the original server, G00882.

GSM sites D35062 and D57791 have 0deg electrical and mechanical tilt andfaces the bay, which

increases their propagation capability over a much longer distance.

Solution:

Delete Ncell D57791 as a neighbour to the site G00882

Mechanically down tilt cell D350621 and D57791 to 6deg



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Sector ID BSIC UARFCN Comments Category Log file Date TimestampG00882 60 83 Serving Active

NodeDeletion ofNcell relation

defined too far

0427_03.log 05 May2006.

15:26:38

D57791 42 551 1stsuccessful

handover, site has

ET and MT=0

Antenna Tilt

change

0427_03.log 05 May

2006.

15:26:38

G350621 53 559 2ndhand over, site

is over shooting

along the coast

and the site has

ET and MT=0

Antenna Tilt

Change

0427_03.log 05 May

2006.

15:26:38



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Site 1193

Area of drop

Area of Call drop

Analysis of 2ndDropped Call


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RxQual of the signal is

very low in this region,

due to interference

Area of call drop



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Cell ID BSIC UARFCN Comments Category Log file Date TimestampG11931 53 93 Site has a down tilt of

4 at the moment

Antenna Tilt

Change

0427_17.log 05 May

2006,

15:26:50

Analysis:Serving cell G57873 has good signal strength at the drop location, but poor RxQ.

90% of the receiving neighbour cells (G11931) footprint is elevated above ground level, yet thecell has a down tilt of 4deg. A mechanical up tilt of -2deg might help to increase the neighbours

RxSS thereby allowing for a longer neighbour measurement window and possibly sufficient time

for handover.

Drop call rate for the serving cell is 0.4%, suggesting a low impact from the RxQ problem.

Solution:Recommend freq retune of G57873 and an uptilt of G11931



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Area of Call drop

Site G1194 withBCCH=85

Cell G321431 withBCCH=85

Area of drop

Analysis of 3rdDropped Call


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Analysis:

RxSS deteriorates due to the TEMS mobile losing line of sight with serving cell G32143

Co-sector G32141BCCH (85) is measured as being a possible candidate for handover. However, a

faraway cell G11942has clear line of sight to the mobile and also has the same BCCH.

Presumably the mobile experienced sufficient interference from the similar BCCH freqs and incorrectly

decodes the BSICs, causing it to incorrectly handover to the co-sector G32141.

It is also suspected that the co-sector neighbour and the serving cell (G32143 and G32141) have cross

feeders as it is quite unusual for a co-sector pointing 120deg away from the serving co-sector, to be

received by the mobile as having a comparable signal level, in spite of the mobile being more then 1kmaway.

Solution:

Successful handover and call completion could be attained by retuning the frequencies of either of the

sites G32141 and site G11942

The possibility of cross feeders between cells G32143 and G32141 will be investigated and the situation

rectified if necessary



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Sector ID BSIC UARFCN Comments Category Log file Date TimestampG32143 52 73 Serving Active

Node

0428_20.log 05 May

2006

15:26:02

G32141 43 85 Handover to

Frequency 85

which is the co-

sector site

Possible

Crossed

Feeder

0428_20.log 05 May

2006

15:26:02

G11942 33 85 Server should

have handed

over to this site

for successful

call completion

Possible

Crossed

Feeder

0428_20.log 05 May

2006

15:26:02



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Rscp and EcNo Distribution over the 1stQuarter of the Route


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Rscp and EcNo Distribution over the 3rdQuarter of the Route


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Rscp and EcNo Distribution over the Last Quarter of the Route


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Antenna Tilt Changes

Recommendations

Cell ID ExistingElectrical Tilt ExistingMechanical Tilt Total ProposedElectrical Tilt ProposedMechanical Tilt Total Comments

D57791 0 0 0 0 6 6 6 degrees

mechanical down tiltD350621 0 0 0 0 6 6 6 degrees

mechanical down tilt

G11931 0 4 4 0 -2 2 2 degrees

mechanical up tilt

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