Common Bcch Multi-bcf Cbcch

7/21/2019 Common Bcch Multi-bcf Cbcch

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Multi-BCF and Common CBCCH

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BSSPAR1: Chapter 10Multi-BCF and Common BCCH


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2 Nokia Siemens Networks RN2010AEN14GLN0

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Module Objectives

Give an overview of the common BCCH and Multi BCF feature

Explain the concept of segments and associated Common BCCHparameters


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Dual Band Operation Every BTS has its BCCH and SDCCH channels

Common BCCH Control Improved spectral efficiency (one BCCH)

Optimised use of signalling channels

Tighter reuse of non BCCH carriers

Better quality (decreased number of HOs)

Non BCCH freq. BTS

BCCH/SDCCH

BCCH freq. BTS

Cell 2

BCCH/SDCCH

Cell 1

BCCH/SDCCH

Common BCCH


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Allows integration of TRXs from different frequency bands into onecell (segment)

Provides service to MSs in all frequency bands which they support Improved spectral efficiency: different bands of a cell share the same

BCCH

BCCH is allowed in any of the supported frequency bands Improved trunking gain

Base stations: Talk Family, Ultra, Flexi and Metrosite

Common BCCH


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BCCH Allocation mainly similar to the single band networkimplementation

Adjacency information sent to the mobile station is based on theBCCH frequency of a common BCCH segment

Other frequency layers in a segment are invisible to the mobilestations

MS sees a segment as one BCCH frequency cell

MS sees many segments as a BCCH frequency network

Modified BA list to an MS on the non BCCH frequency layer of asegment

the BCCH frequency of the segment itself is added among the BCCH

frequencies the MS measures

Common BCCH


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Initial SDCCH on the BCCH carrier band

the multiband capabilities of an accessing mobile station are notknown at the time of the initial SDCCH allocation

no way to define the usability of the non-BCCH layer of the segmentbecause the MS starts sending measurement reports only after it hasmoved to a dedicated channel

While the MS is on an SDCCH the BSC receives

in Classmark Change message Mobile Station Classmark 3 indicatingthe terminal's frequency capability of using other frequency bandsthan BCCH frequency band

SDCCH allocation in CBCCH


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1. SYS INFO-1 (BCCH)- CA list of BCCH frequency band

2. IMMEDIATE ASSIGNMENT COMMAND(AGCH)- MA list of BCCH frequency band (if FH)

Initial SDCCH allocation always from BCCH frequency band

Non BCCH freq. layer

BCCH freq. layer

SDCCHSDCCH

Common BCCHInitial SDCCH allocation


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Segment and BTS objects

Segment

Segment = Telecom cell A segment may consist of severalBTS objects. BTSs of a segment are co-locatedand synchronised. The maximum number of BTSs in asegment is 32. The maximum number of TRXs in asegment is 36.

BTS object in a segment must consist

of TRXs of the same frequency bandand base station type

This is an example only. Itis also possible to have

EGSM and PGSMresources in the same BTS

object.


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Allows combination of several BTSs into one logical cell

BSC supports Multi BCF Control for Talk family, UltraSite, Flexi and MetroSitebase stations (specific BTS combinations)

Allows the operator to increase the capacity of a cell to 24 TRX (Metro, TalkFamily) or to 36 TRXs (Ultra, Flexi)while maintaining the maximum spectralefficiency (no extra BCCH)

Site expansion path from Talk Family to UltraSite/Metrosite (thus providingEDGE support to the site)

In the case of MetroSite the BSC allows only MetroSite base stations in a multiBCF segment

When Multi BCF Control and Common BCCH are combined you are allowed toconfigure both BTSs of different frequency bands and BTSs of different basestation types to one segment.

Multi BCF




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BTS-1, BCCH-1

- BB hopping- 6 TRXsBTS-5, BCCH-5

- RF hopping- 6 freq, f1-f6- 2 TRXs

BTS-3, BCCH-3


- RF hopping- 6 freq, f1-f6- 2 TRXs BTS-2, BCCH-2



BTS-1, BCCH-1

- BB hopping- 6 TRXsBTS-5

- RF hopping

- 6 freq, f1-f6- 2 TRXs

BTS-3, BCCH-3


- RF hopping- 6 freq, f1-f6- 2 TRXs BTS-2, BCCH-2



UltraSite 8+8+8 configurationwith separate BCCH (DualBCCH)

altogether 6 BCCH carriers

UltraSite 8+8+8 configurationwith Multi BCF

improved spectral efficiency, 3BCCH carriers

Multi BCF, example




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GSM 1800

GSM 900

BCCHBTS1

BTS2

GSM 1800

GSM 900

BCCHBTS1

BTS2

bsTxPwrMax = peak power 0 dBbsTxPwrMax1x00 = peak power 0 dB

GSM 900 signal tends to be stronger than GSM 1800

-> wider coverage for GSM than for GSM 1800-> useless if BCCH is taken from GSM 1800

Band specific maximum output power of BTS

bsTxPwrMax used for GSM 800/900bsTxPwrMax1x00 used for GSM 1800/1900

bsTxPwrMax = peak power 6 dBbsTxPwrMax1x00 = peak power 0 dB

Common BCCHBand Specific Power Control




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Common BCCH

TXP230 dBmThe maximum transmission power an MS may use

when accessing a CCH in the cell for GSM

1800/1900 bands.

Range:

GSM 1800: 0..36 dBm (step size 2)

GSM 1900: 0..32 dBm (step size 2) and 33 dBm

0...36 dBm, step 2 dBmmsTxPwrMaxCCH

1x00

BTS

TXP133 dBmThe maximum transmission power an MS may use

when accessing a CCH in the cell for GSM 900/800

bands.

5...39 dBm, step 2 dBmmsTxPwrMaxCCHBTS

BSC - MML

Name

Default

value

DescriptionRange And StepAbbreviated

Name

MO

Class




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Common BCCHAccess to non-BCCH layer

LAR-90 dBmThreshold value for the estimated downlink

signal level on non-BCCH layer for a

moving MS from BCCH layer to non-BCCH

layer.

-110...-47 dBm,

step 1 dBm

nonBcchLayerA

ccessThr

HOC

NBL0Defines whether the predefined offset

margin is used when evaluating the signal

level of the non BCCH layer.

-40...40, step 1nonBCCHLayer

Offset

BTS

BSC - MML

Name

Default

value


Name

MO

Class




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MS indicates its capabilities while on an SDCCH

=> BSC finds out if non BCCH frequency band resources could be included inchannel allocation for the terminal

MS reports the downlink signal level on the SDCCH

=> BSC finds out if radio conditions are good enough for the MS to use nonBCCH frequency resources of the segment with the criterion

RXLEV_DL NonBcch LayerOf fset>= NonBCCHLayerAccessThreshold

Where: RXLEV_DL is last received signal strength on the serving channel

With the decisions above the BSC determines the applicable frequency bands ofa segment for an MS during call setup when the MS moves from an SDCCH to aTCH

Common BCCHCall Setup




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In BSC internal handovers between separate cells the usability of BCCH frequency handresources in a target cell is defined using the BTS specific offset parameter and aneighbour parameter defined for the target cell:

AV_RXLEVNCELL (n) >= rxLevMin Cell (n)

In BSC internal handovers between separate cells the usability of non BCCH frequencyband resources in a target cell is defined using the BTS specific offset parameter and a newthreshold parameter defined for the target cell:

AV_RXLEVNCELL (n) NonB cch LayerOffset (n)>=NonBCCHLayerAccessThreshold (n)

Applies to both SDCCH and TCH allocation cases

Common BCCHIntercell Handover




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When the call is going on on a non-BCCH frequency band the usability of differenttypes of resources is defined based on the averaged BCCH measurement results.The following formulas are used:

AV_BCCH_RXLEV_DL NonBcchLayerOffset >= rxLevAccessMin

AV_BCCH_RXLEV_DL NonBcchLayerOffset >= NonBCCHLayerAccessThreshold

The first formula is used to evaluate the usability of BCCH frequency resources of thesegment. The second formula is used to evaluate the usability of non-BCCH frequencyresources of the segment.

Common BCCHIntra cell handover




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In case of handover to a segment of another BSC, the non-BCCH layer of the segmentis usable if it is at least as strong as the BCCH layer.

The nonBCCHLayerOffset(n) on the target non-BCCH BTS must be equal to zero orless than zero for the BTS to be used for incoming handover

Applies to both TCH and SDCCH cases

Common BCCHExternal handover




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Common BCCHSDCCH Handover based on duration of reservation

Since the allocation of the initial SDCCH takes place in the band where the BCCH is, a method is defined totrigger SDCCH handovers to other band(s)

Based on the SDCCH reservation duration on the initial band

Guided by a parameter IntraSegSdc chHo Guard (ISS)

SDCCH reservation duration exceeds IntraSegSdcchHoGuard

There are resources outside the initial band in a cell and satisfy the following:

RXLEV_DL - non BCCH layer offset >= non BCCH layer access threshold

MS has the required support for the other resource types

ISS255 sguard time for attempting an

SDCCH handover from the

BCCH BTS resource layer to

another resource layer in a

segment.

0...255 s, step 1 s

0: no time limit set for starting an SDCCH

handover attempt from the BCCH BTS

resource layer, attempt can be made as

soon as possible1..254: time after which an SDCCH

handover from the BCCH BTS resource

layer is attempted

255: no SDCCH handover from the BCCH

BTS resource layer is attempted based on

SDCCH reservation duration

intraSegSdcchHoG

uard

BSC

BSC - MML

Name

Default

value


Name

MO

Class




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BSC initiates an intra cell handover when TCH load in a some BTS of the

segment reaches a level defined with the BTS level parameterBTSLoadInSEG.

Triggering level = BTSLoadInSEG +((100 - BTSLoadInSEG )/2)

BSC checks the load of the BTSs every time it receives a TCH request for thesegment

BSC accepts as target only the segment's BTSs whose load is below the respective BTSLoadInSEG value

in which the radio conditions are good enough

which are not same resource type as the source BTS and the BCCH BTS

The handover is primarily used to move TCH load from the BCCH resourcetype but handovers can also be made between other resource types

Common BCCH & Multi BCFHandover for balancing load




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Common BCCH & Multi BCFBTS Load in SEG

LSEG70%Determines the load limit for a BTS.

It is used in controlling the load distribution

between BTSs in a segment.

0...100 %, step 1 %btsLoadInSegBTS

BSC - MMLName

Defaultvalue

DescriptionRange And StepAbbreviatedName

MOClass


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Common BCCHIntra cell handover from non BCCH layer based on signal level

BSC initiates an intra cell handover from non BCCH layer to BCCH layer when the averageddownlink signal level on serving channel decreases below the threshold defined by

parameter NonB cch LayerExitTh resho ld (LER, Nx, Px) This decreases the number of inter cell handovers from non BCCH layer

Handover is applicable in cells where BCCH layer has more coverage than non BCCH layer

BSC uses general Power Control and Handover Algorithm functions to trigger the handover

If intra cell handover fails then inter cell handover can be triggered

LER-95 dBmWith this parameter you define a threshold value

for the measured downlink signal level on non-

BCCH layer for a moving MS from non-BCCH layer

to BCCH layer

-110...-47 dBm, step 1

dBm

rxLevelHOC

LEP1Px value for the above threshold1...32, step 1nonBcchLayerExit

Thr_px

HOC

LEN1Nx value for the above threshold1...32, step 1nonBcchLayerExit

Thr_nx

HOC

BSC - MML

Name

Default

value


Name

MO

Class

Documents

Common Bcch Multi-bcf Cbcch