Single BCCH Dual Band Cell Principles and Optimisation

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Agenda Single BCCH Dual Band description Parameters involved Direct TCH allocation procedure Handover procedures Synthesis of handover procedures Engineering rules Parameters optimization process Interaction with others V12 features Specific metrics to be monitored

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Single BCCH Dual Band description 1/3Band1 layer (GSM or DCS) carries only TCH

Band0 layer (GSM or DCS) carries BCCH, SDCCH and TCH SDCCH and BCCH are only defined in band 0 and are common for both bandsslide - 3

Single BCCH Dual Band description 2/3 The GSM900/DCS1800 are managed by the same cell : a dualcell If no Classmark 3 information (early classmark sending) are displayed, the HO (MS DB or not) are allowed only in band 0 of either serving or neighboring cells

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Single BCCH Dual Band description 3/3 Direct TCH allocation:

Signaling reduction A TCH may be allocated directly in band 1 => less HO intra cell from band 0 to band 1. Capacity increase No more BCCH and SDCCH in band 1, only TCH or PDTCH configured on band 1 TDMA frame.

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Parameters involved The parameters which need to be tuned are the following :- concentAlgoIntRxLev : minimum signal strength below which a HO is triggered from band1 to band0. - concentAlgoExtRxLev : maximum signal strength beyond which a HO is triggered from band0 to band1. - biZonePowerOffset : an offset in the serving cell which is used to estimate the virtual RxLev of band0. Only used when the MS leaves the current bizone cell out of its small zone. - biZonePowerOffset (n) : an offset in neighboring cell which is used to estimate the virtual RxLev of band1 signal to determine if the MS can directly access this band in the neighboring cell.

The offset is introduced to compensate the difference of propagation between the signal of both bands.slide - 6

Parameters involvedconcentAlgoExtRxLev

concentAlgoIntRxLev

Estimated RxLev900

biZonePowerOffset

RxLev900 RxLev1800slide - 7

Parameters involvedconcentAlgoExtRxLev

concentAlgoIntRxLev

biZonePowerOffset(n)

RxLev900_N RxLev1800_N Estimated RxLev1800_N RxLev1800slide - 8

Direct TCH allocation procedure The following conditions have to be verified:band0 to band1 : concentAlgoExtRxLev < RxLev_DL and MS_band_supported Where RxLev_DL is an arithmetic average computed with all available measurements (from one up to Rxlev_HreqAve)

The TCH is allocated in band 1

If conditions are not true: The BSC allocate a TCH in band 0The BSC doesnt send the inquiry if the call is established on a TCH signaling

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Handover procedures(1/4) Inter-zone HO (intracell inter-band) :- band1 to band0 : concentAlgoIntRxLev > RxLev_DL

- band0 to band1 : concentAlgoExtRxLev < RxLev_DL and MS_band_supported

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Handover procedures(2/4) Intracell intra-band :same requirement as a classic one

Intercell intra-band :band0 to band0 : same requirements as a classic HO intraBSS / inter BSS

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Handover procedures(3/4) Intercell intra-band :band1 to band1 : exp1 > 0 : RxLevNCell(n) > RxLevMinNCell(n)exp2 > 0 : RxLevNCell(n) > RxLev_DL+ hOMargin exp3 > 0 : RxLevNCell(n) > [RxlevMinCell(n) + bizonePowerOffset(n) MS_band_supported exp1 computed by L1M to make a list of eligible cells exp2 computed by L1M to select the best possible cells exp3 computed by L1M to check if direct HO to the small zone is possible

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Handover procedures(4/4)

Intercell inter-band :band0 to band1 : exp1 > 0 exp2 > 0 exp3 > 0 MS_band_supported band1 to band0 : exp1 > 0 exp2 > 0 exp1 computed by L1M to make a list of eligible cells exp2 computed by L1M to select the best possible cells exp3 computed by L1M to check if direct HO to the small zone is possible

Inter-BSC HO is only done towards band0.

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Synthesis of Handover proceduresPrinciples : : Principles Interzone HO: band1 --> band0 :rxLevDLt < concentAlgoIntRxLev

Intracell intraband HO: band0 --> band0 or band1--> band1normal intracell HO

Interzone HO: band0 --> band1 :rxLevDL > concentAlgoExtRxLev MS_Band_supported(standardIndicatorBand1) is true

Intercell interband HO: band0 --> band11_ EXP1 > 0 2_ PBGT 3_ EXP2 > 0 4_ EXP3 (bizonePowerOffset(n)) > 0 5_ MS_Band_supported(standardIndicatorBand1) is true

Intercell intraband HO: band0 --> band0:normal intercell inter or intra BSS

Intercell intraband HO: band1 --> band1 Intercell interband HO: band1 --> band01_ EXP1 > 0 2_ PBGT (msTxPwrMax2ndBand, bizonePowerOffset) 3_ EXP2 > 0 1_ EXP1 > 0 2_ PBGT (msTxPwrMax2ndBand, bizonePowerOffset) 3_ EXP2 > 0 4_ EXP3 (bizonePowerOffset(n)) > 0 5_ MS_Band_supported(standardIndicatorBand1) is true

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Engineering RulesconcentAlgoExtRxLev = concentAlgoIntRxLev + biZonePowerOffset + margin the higher the margin, the fewer ping-pong HO between both zones, HO & direct TCH allocations toward band 1 are delayed impacting the traffic distribution strategy

concentAlgoIntRxLev < RxLevMinCell(n) + biZonePowerOffset(n) the more RxLevMinCell(n) + biZonePowerOffset(n) is superior to concentAlgoIntRxlev, the more it will avoid the call to be redirect in band 0 after a handover intercell directly in band 0.

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Parameters optimization process (1/4) Tune concentAlgoXXXRxlev according to the trafficdistribution strategy.

Then tune the BiZonePwrOffset and BiZonePwrOffset(n) Monitor the trafic distribution, the global QoS, the calldrop ratio, the TCH and SDCCH blocking rates

Perform drive tests, radio survey, and call (path) trace toreach a fine tuning and to validate the settings. Correlation with counters is necessary

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Parameters optimization process (2/4)First step: concentAlgoXXXRxLev Reduce Blocking, Preferred Band (e.g. better Freq Plan)

Parameters can be changed by step of 1 or 2 dB (two at the beginning andthen one to reach a fine tunning) 1dB reduces cell coverage by roughly 13% Too much traffic in band 0 decrease concentAlgoExtRxLev Too many direct TCH assignments in band 1 increase concentAlgoExtRxLev Assignments failure too high harden access by increasing value of concentAlgoExtRxlev

concentAlgoExtRxlev concentAlgoIntRxlevslide - 17

Parameters optimization process (3/4)Second step: offsets Tread-off between number of HO and HO performances.

Parameters can be changed by step of 2 then 1 dB. Bad ho performances between two different bands, try to harden the access by increasing1. 2.

First BiZonePwroffset or BiZonePwroffset(n) Second concentAlgoExtRxlev and concentAlgoIntRxlev

Bad ho performances between two same bands, try to harden the access by:

Increasing BizonePwrOffset classical tuning (Homargin, Thresholds)

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Parameters optimization process (4/4)biZonePowerOffset= Delta 900/1800 propagation + Delta 900/1800 coupling + Margin (Fading)

- Lower Margin (Fading) required due to SFH over 8 frequencies on 1800Mhz - Less risks of big discrepancies between estimated and real signal => better performancesslide - 19

Interaction with others V12 Features Can use the TF821 protection against ping ponghandover feature to improve network behavior

A V12 feature TF716 HO according to adjacent cellload & priority used with dual band cell can brings some improvement on the ho success ratios.

A V12 feature TF132 HO for traffic reason used withdual band cells brings congestion improvements

All features can be used all together and may improvethe network behavior, but it needs a deep tuning.

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Metrics to be monitored General indicators on OMCR report to evaluate: Traffic (total, band0, band1) SDCCH and TCH Blocking rates QoS Establishment Failure rate (Assignment Failure) Handover Failure rate Call Drop ratio

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Questions

Dual band Indicators Dual Band (DB) indicators on OMCR report to evaluate: Dual Band penetration estimation Direct TCH Allocation TCH Assignment failure rate Successful Incoming Handovers rate Successful Inter-zone Intra-cell HO rate Success Out band0 to band1 Msdualb ratio Success Out band0 to band0 Msdualb ratio Success Out band1 to band1 Msdualb ratio Success Out band1 to band0 Msdualb ratioslide - 23

Specific metrics to be monitored (1/4) MS Dual band penetration :1207_0 / i=0; 1; 4; 5; 6; 7 [1192_ i]

Direct TCH allocation :call establishment C1799 / (C1715 - C1798)

TCH assignment failure :1 - (C1716 / 1715)

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Specific metrics to be monitored (2/4) Ratio of Intracell HO (execution)Success: C1798/C1797 HointracellTCHRatio (inner to outer): C1138/11 /(1138/15+1138/16+1081/0) HointracellTCHRatio (outer to inner): C1138/12 /(1138/15+1138/16+1081/0)

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Specific metrics to be monitored (3/4) Ratio of Outgoing HO (execution)Success Out band0 to band1 Msdualb ratio : C1209 / C1789 Success Out band0 to band0 Msdualb ratio : C1786 / C1790 Success Out band1 to band1 Msdualb ratio : C1787 / C1791 Success Out band1 to band0 Msdualb ratio : C1788 / C1792

Ratio of Incoming HO (execution)Success Inc HO Msdualb ratio : C1795 / C1794

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Specific metrics to be monitored (4/4) TCH Blocking :

(1613/0 - 1081 + 1082 + 1614/0 + 1617/0 + 1617/1) (1613/0 + 1614/0 + 1617/0 + 1617/1 + 1609/0 + 1609/1 + 1609/2 + 1610/0)

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