b9 radio fine tuning

All rights reserved © 2004, Alcatel

Introduction to Radio Fine Tuning BSS release B9

TRAINING MANUAL3FL10493AAAAWBZZA ed 1

October 2005

2@Introduction to Radio Fine TuningBSS Release B9


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Note : Please print this document with comments pages



Contents

> 1 TYPICAL RADIO PROBLEMS > 2 ALGORITHMS AND ASSOCIATED PARAMETERS > 3 OTHER ALGORITHMS> 4 ALGORITHMS DYNAMIC BEHAVIOR> 5 CASE STUDIES



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1 TYPICAL RADIO PROBLEMS



1 TYPICAL RADIO PROBLEMS Session presentation

> Objective: to be able to characterize typical radio problems in order to trigger an intervention of the appropriate team

> Program:1.1 Theoretical presentation1.2 Coverage problem1.3 Interference problem1.4 Unbalanced power budget problem1.5 TCH Congestion problem1.6 Deducing the right team for intervention1.7 Exercises



1.1 Theoretical presentation



> Several sources of information can alert RFTM team: • QoS indicators• Customers complaints• Drive tests• Other teams information (NSS statistics)

> As many symptoms are common to several causes, it can be necessary to:

• Consolidate standard sources of information• Carryout specific examinations• Deduce the appropriate team for intervention

1.1 Theoretical presentation Justification



1.2 Coverage problem



> Definition: Bad coverage• A network or cell facing coverage problems presents a bad

RxLev and RxQual in the same time on some areas.

> Symptoms:• Customers complain about dropped calls or/and “no network”• OMC QoS indicators

– TCH failure rate– Call drop rate– Low proportion of better cell HO– High rate of DL quality HO

• A interface indicators– High rate of Clear Request messages, cause radio interface

failure

1.2 Coverage problem Definition and symptoms



> Depending on the information sources you have:• Radio Measurement Statistics (RMS) –

– (RxLevel , RxQuality) matrix– Radio Link Counter S vector– Number of calls with DL/UL bad coverage (bad RxLev, bad

RxQual) • Abis interface (for example with COMPASS)

– bad quality > 5%– bad level RxLev < - 95 dBm and RxQual > 4

• OMC-R or A interface– unexpected high traffic, induced by call repetition

• Billing information– High recall rate detected

1.2 Coverage problem Examination



> If the actual coverage is not the one predicted by RNP tools– check antenna system– increase or decrease antenna down-tilt– check BS_TXPWR_MAX

– to be increased if value different to RNP power budget

> If the actual coverage is OK compared to the predicted ones– indoor traffic, to be handled by specific means– if black spot close to cell border, ease outgoing HO

1.2 Coverage problem Typical causes



> Example of an Abis trace analysis

1.2 Coverage problem Investigation with Abis trace (1/2)

Frequency

RxLev_UL

RxLev_DL

RxQual_UL Path_loss_UL

Path_loss_DL

delta_Path_loss Delta_quality AV_MS_PWR Nb_of_samples

RxQual_DL

Frequency

Qual0 Qual1 Qual2 Qual4 Qual5 Qual6 Qual7 Bad_QualityQual3

Frequency


119 -89.29 -84.67 0.42 123.82 123.67 0.15 -0.01 34.53 30740.43

92 -89.77 -89.09 0.41 124.87 128.09 -3.21 0.03 35.11 10 2530.38

111 -83.15 -79.15 0.17 116.05 121.22 -5.16 -0.16 32.9 53390.33

DISTRIBUTION OF UPLINK QUALITY

119 86.50% 3.19% 2.50% 1.92% 2.08% 0.98% 0.26% 3.32%2.57%

92 88.11% 1.82% 1.91% 2.14% 2.17% 1.15% 0.19% 3.51%2.51%

111 77.70% 4.30% 4.30% 3.56% 3.56% 1.70% 0.17%4.36%

119 88.29% 1.82% 2.05% 1.30% 1.46% 1.76% 0.94% 4.16%2.37%

92 87.50% 2.98% 2.60% 2.11% 1.14% 0.74% 0.50% 2.38%2.43%

111 71.30% 3.82% 4.02% 4.16% 4.30% 4.23% 3.16%4.89%

DISTRIBUTION OF DOWNLINK QUALITY

5.43%

11.73%




1.2 Coverage problem Investigation with Abis trace (2/2)

Thresholds

Bad Coverage– RxLev ≤ -95- RxQual > 4

Interference– RxLev > -95– RxQual > 4

3-88.0063-95.3331-71.0031-80.0061-80.003 -80.003

57

111

1212

Number_UL: 10 253Number_DL: 10 253

Int_UL: 2BC_UL:

358Int_DL: 0%

0.02%3.49%

67-104.64

2048-

107.5051

Number_UL: 5339Number_DL: 5339

Int_UL: 0BC_UL:

290Int_DL: 0%BC_DL:

626

0.00%5.43%

Samples<Lev>BSIC63-

101.542

Samples<Lev>BSICNeigh_Cell_Nb

Samples<Lev>BSICNeigh_Cell_Nb

<RxLev_Serving>= -102.17 dBm3.74%BC_DL: 115

57-100.53

2045-98.7121034-98.036533-98.6137

<RxLev_Serving>= -106.56 dBm

BC_DL: 244

2.38% <RxLev_Serving>= -106.17 dBm

Frequency: 92

Frequency: 111

11.73%Neigh_Cell_Nb10



> Suspecting a cell coverage problem• Distribution of samples per RxQual value and RxLev band

• Distribution of samples per RxLev band

1.2 Coverage problem Investigation with RMS (1/2)

012

45

7

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

RxQuality (Nb)

RxLevel(dB)

[0, 14 793]]14 793, 23 446]]23 446, 29 586]]29 586, 34 348]]34 348, 38 239]]38 239, 41 529]]41 529, 44 378]]44 378, 46 892]

Out of RangeX

Interval of numberof samples

Downlink Samples Matrix in log scale

3

6

Not acceptable coverage limit:too low level

too bad quality



> Suspecting a cell coverage problem• Average TA values per RxQual value and RxLev band

1.2 Coverage problem Investigation with RMS (2/2)

16.00%14.00%12.00%10.00%8.00%6.00%4.00%2.00%0.00%

01/1

2/20

01

01/0

1/20

02

02/0

1/20

02

03/0

1/20

02

04/0

1/20

02

05/0

1/20

02

06/0

1/20

02

07/0

1/20

02

08/0

1/20

02

09/0

1/20

02

10/0

1/20

02

11/0

1/20

02

12/0

1/20

02

13/0

1/20

02

14/0

1/20

02

109876543210

%N > TA thres TA max

Maximum Timing Advance and TA > threshold

N > TA thresTA maxTA threshold

012

45

7

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

RxQuality (Nb)

RxLevel(dB)

[0, 2]]2, 4]]4, 6]]6, 8]

Out of Range

Interval of averageTiming Advance

Uplink average TA Distribution

3

6

X

Acceptablecoverage limit:

sufficient level andgood quality

Not acceptablecoverage limit:

too low level andtoo bad quality

% of TA valueover TA threshold

has also to beconsidered



1.3 Interference problem



> Definition: Interference• A network facing interference problems presents good RxLev and bad

RxQual in the same time on some areas.

> Symptoms• Customers complain about bad speech quality (noisy calls) and/or call

drops• OMC QoS indicators

– SDCCH/TCH Drop– Low proportion of better cell HO– High rate of DL/UL quality HO and interference HO– Low HO success rate

• A interface indicators– High rate of Clear Request messages, cause radio interface failure

1.3 Interference problem Definition and symptoms



> Radio Measurement Statistics (RMS)– RxQual/RxLev matrix – CFE/RxLev matrix– C/I vectors for neighbors– C/I vectors for MAFA frequencies

– MAFA is a new standardized GSM feature for mobiles– MAFA mobiles can provide C/I measurements from

non-neighbor cells– Number of calls with DL/UL interference (good RxLev, bad

RxQual)– Number of noisy calls (bad RxQual) with bad voice quality (bad

FER)– A high rate use of the most robust AMR codecs also denounce

interferences problems . But be careful, this can also be due to a pessimistic choice of the thresholds used for codec change.

1.3 Interference problem Examination with RMS (1/3)



> Suspecting a cell interference problem• Number of samples per RxQual value and RxLev band


Quality problems are obvious at any level of RMS data

Interference highlightedNetwork fine tuning needed

012

45

7

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

RxQuality (Nb)

RxLevel(dB)

[0, 14 793]]14 793, 23 446]]23 446, 29 586]]29 586, 34 348]]34 348, 38 239]]38 239, 41 529]]41 529, 44 378]]44 378, 46 892]

Out of RangeX


Downlink Samples Matrix in log scale

3

6

Average DL RxQuality = 2.81

Average RxQual value per RXLev bandhas also to be considered

012345

6

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

RxQuality (Nb)

RxLevel(dB)

Downlink average RxQuality per RxLevel

RxQualityAverage



> Suspecting a Voice Quality problem• Number of samples per BFI band and RxLev band


[0, 1[[1, 2[[2, 4[

[6, 8[[8, 10[

[14, 18[

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

CFE (Nb)

RxLevel(dB)

[0, 14 793]]14 793, 23 446]]23 446, 29 586]]29 586, 34 348]]34 348, 38 239]]38 239, 41 529]]41 529, 44 378]]44 378, 46 892]

Out of RangeX


Consecutive Frame Erasure Matrix in log scale

[4, 6[

[10, 14[

[14, 18[[14, 18[

0123456

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

Average CFE

RxLevel (dB)

Uplink average Consecutive Frame Erasure per RxLevel

78

Average RxQual

0

1

2

3

4

5

6CFEAverage

RxQualityAverage

Consecutive Frame Erasure (BFI) is a measurement based on loss of consecutive

speech frames over one SACCH mw.

It is directly linked to Voice Quality.

RxQual to be compared with CFE since Bad RxQual does not always mean bad VQ.



> GSM interference– co-channel– adjacent

> Non GSM interference– other Mobile Networks– other RF sources

1.3 Interference problem Typical causes



> Adjacent channel interference– +6 dB are sufficient to interfere (9 dB according GSM)

1.3 Interference problem GSM interference: adjacent channel (1/2)

Level

Frequency

F(BTS1)

6 dB

F(BTS2)F(BTS1) = F(BTS2)+1



> Adjacent channel interference:• Symptom

– Usually downlink interference– High rate of quality HO, call drop (due to HO but mainly due to

radio) and TCH assignment failure

• Examination– Neighbor cells in Abis trace (only for BCCH)– Non-neighbor cells in RMS (MAFA frequencies)– Frequency planning C/(I adjacent) < -6 dB

• Correction– Downtilt increase of interferer, or even change of antenna

orientation – Reduction of BS power if necessary, Change of frequency (best

solution)– Concentric cell implementation (1 extra TRX needed if traffic

cannot be supported by Outer+Inner configuration)

1.3 Interference problem GSM interference: adjacent channel (2/2)



> GSM Interference• Co-Channel interference

– -12 dB are sufficient (-9 dB according GSM)

1.3 Interference problem GSM interference: co-channel (1/2)

Level

Frequency

F(BTS1)

-12 dB

F(BTS2)F(BTS1) = F(BTS2)



> Co-channel interference• Symptom

– Usually downlink interference– High rate of quality HO, call drop and call failure

• Examination– Neighbor cells in Abis trace (only for BCCH)– Non-neighbor cells in RMS (MAFA frequencies)– Frequency planning C/I < 12 dB

• Correction– Downtilt increase of interferer, or even change of antenna

orientation – Reduction of BS power, Change of frequency– Concentric cell implementation (1 extra TRX needed if traffic

cannot be supported by Outer+Inner configuration)

1.3 Interference problem GSM interference: co-channel (2/2)



> GSM interference: µcellular

• BTS1: ARFCN 5• BTS2: ARFCN 6

• MS1 indoor– RxLev_UL: - 90 dBm

• MS2 outdoor, connected to BTS2– 1: no level on BTS1

(BTS 1 under-roof)– 2: - 80 dBm on BTS1:

interferer UL/DL– 3: no level on BTS1– µcell algo prevents BTS2-

>BTS1 HO

1.3 Interference problem GSM interference: µcellular

MS 1(indoor)

MS 2(outdoor) 1

2

3

BTS 1(Micro)

BTS 2



> GSM Interference: Forced Directed Retry

• The MS should connect to cell2, but no TCH available

• The MS connects to cell 1 with forced directed retry

• The MS is emitting at high level (far from BTS1)

– UL interference for BTS 3• BTS 1 is emitting at high level

– DL interference at BTS 3

1.3 Interference problem GSM interference: Forced Directed Retry

Cell 2: 45

C ell 3: 23C

ell

1: 2

4

MS

BTS 2

BTS 1

BTS 3



> Other mobile networks: TACS/AMPS/NMT900– Inter-modulation with GSM BS/MS receiver– spurious RACH for AMPS (AMPS Tx bands close to GSM

uplink band)– examination

– TASC: coverage hole with 600 m from TASC BTS– AMPS => 50% reduction of range if AMPS/GSM BTS

collocated

> Other RF interferers (Radar, shop anti-theft mechanisms, medical device ...)

1.3 Interference problem Non-GSM interference



1.4 Unbalanced power budget problem



> Definition: Unbalanced power budget• A cell facing unbalanced power budget problems presents a too high

path-loss difference between UL and DL (often DL>UL)• Rule: try to have delta as small as possible to avoid access network

possible only in 1 direction (usually BTS->MS: OK and MS->BTS: NOK)> Symptoms:

• OMC QoS indicators– High rate of Uplink quality Handover causes– Low incoming HO success rate (no HO Access triggered on the

uplink)– Degradation of TCH failures and OC call drop indicators

• A interface indicators– High rate of Clear Request messages, cause radio interface failure

• O&M Alarms– Voltage Standing Wave Ratio BTS Alarm (VSWR)– TMA Alarm (in case of G2 BTS or Evolium BTS with high power

TRE)

1.4 Unbalanced power budget problem Definition and symptoms



1.4 Unbalanced power budget problem Examination

> Examination• RMS –

– Path Balance vector per TRX– Number of calls with abnormal bad FER (good RxQual & bad

FER)

• Abis monitoring:– |delta path-loss| > 5dB– Check if problem is occurring for 1 TRX or all




1.4 Unbalanced power budget problem Abis trace

106 -94.52 -87.19 0.43 127.55 130.19 -2.64 0.18 33.03 20660.25

Frequency


Frequency


89 -84.29 -75.17 0.65 115.32 118.17 -2.85 0.21 31.03 20010.44

118 -90.75 -83.36 0.46 123.22 126.36 -3.14 0.04 32.46 31930.41

124 -88.89 -85.30 0.29 120.48 128.30 -0.37 31.59 29310.67

DISTRIBUTION OF UPLINK QUALITY

106 84.75% 4.07% 3.68% 1.36% 1.50% 0.92% 0.53% 2.95%3.19%

89 81.41% 1.70% 2.95% 6.35% 2.55% 1.30% 0.10% 3.95%3.65%

118 83.62% 4.23% 4.23% 1.57% 1.79% 0.97% 0.25%3.35%

106 90.27% 3.44% 2.08% 0.92% 1.36% 0.34% 0.05% 1.74%1.55%

89 80.16% 6.45% 7.00% 1.50% 0.50% 0.45% 0.10% 1.05%3.85%

118 86.78% 2.72% 3.95% 1.41% 1.13% 1.19% 1.00%1.82%

DISTRIBUTION OF DOWNLINK QUALITY

3.01%

3.32%

Frequency

RxLev_UL

RxLev_DL

RxQual_UL Path_loss_UL

Path_loss_DL

delta_Path_loss Delta_quality AV_MS_PWR Nb_of_samples

RxQual_DL

-7.82

124 90.79% 1.06% 2.18% 1.77% 1.30% 0.48% 0.07%2.35% 1.84%

124 77.14% 4.37% 5.87% 3.48% 1.36% 0.82% 1.02%5.94% 3.21%



> Suspecting a TRX hardware problem• Average Path Balance

• Fair average Path Balance at Cell level can hide a bad value for one TRX

1.4 Unbalanced power budget problem RMS data

0500

10001500200025003000

[-110,-20[

[-20,-10[

[-10,-6[

[-6,-3[

[-3,0[

[0,3[

[3,6[

[6,10[

[10,20[

[20,110[

Nb Samples

PathBalance(dB)

NbSamples

PathBalance Distribution

Average Cell Path Balance = - 0.9 dB



> Antennae or common RF components, TMA (pb common to all TRXs of the BTS)

> TRX RF cables/LNA ... if problem located on only 1 FU

1.4 Unbalanced power budget problem Typical causes



1.5 TCH Congestion problem



1.5 TCH Congestion problem Definition and symptoms> Definition: TCH Congestion

• TCH Congestion rate (TCH Assignment Phase) is too high (more than 2%)

• Rule: try to meet the offered traffic (asked by users) by providing the right number of resources (TRX extension)

> Symptoms:• Customers complain about ‘Network busy’• OMC QoS indicators

– High “TCH Congestion rate”– Low “incoming Intra/Inter BSC HO success rate” (no TCH

available)– High “Directed Retry rate” if activated

• A interface indicator: “BSS Congestion failure in OC”– High rate of Assignment Failure messages, No radio

resource available



1.5 TCH Congestion problem Examination and typical causes

> Examination: TCH Congestion• On a per cell basis examination, check the evolution of

the TCH Congestion rate.> Typical causes:

• Special events: – Foreseeable: football match, important meeting

– Activate some TRXs already installed (and use Synthesized FH)

– Add special moving BTSs– Not foreseeable:

car crash on the highway



1.5 TCH Congestion problem Typical causes (1/2)

• Daily periodic problems– At peak hour, the cell is not correctly dimensioned.

Hardware solution (refer to Annex 1)

– Estimate the offered traffic: At OMC-R level: Traffic in Erlang/(1- TCH Congestion rate)

– Use the B-Erlang law to estimate the number of TCHsrequired for a 2% blocking rate, thus the target configuration

– Add TRXs to reach the new target configuration and find ‘joker frequencies’ and / or implement concentric cells.

Annex 1



1.5 TCH Congestion problem Typical causes (2/2)

> Daily periodic problems– At peak hour, the cell is not correctly dimensioned.

Software solution– Use specific densification features

» Half Rate» Forced Directed Retry » Traffic handover» Fast Traffic handover » Candidate Cell Evaluation (FREEFACTOR /

LOADFACTOR)



1.6 Deducing the right team for intervention



1.6 Deducing the right team for intervention Process

Problem characterization

Make assumption causes

Check the tuning of default radio parameters

Consult the config. db Choose an (other) classical algo

Identify the tunable parameters

Impact estimation

Standard setting ?

No

Yes

Yes

No

No

Yes

Call expert

- Microcell, multiband- Concentric

=N

No

Yes

No

Yes

No

Yes

Parameters modificationDatabase updating

Impact simulation of aparameter modification

No

- Hopping- Marketing

Yes

QOS alarm on the network,on a BSC or some cells

- Indicators (% call drop)- Field measurements/planning- Subscriber complains

QOS team

DHCPEND

Drive test team

DHCPEND

Dimensionning team

OK

Correctionaction

Maintenance team

Planning team

NOK

Cell corrected ?Neighbor cell ?

RFT team - Interferences- Coverage (indoor)- Power budget- Congestion (TCH, SDCCH)- BSS problemInvestig problem ?

Planning/BSS causes

Standard parameters ?

Onpurpose

Systemproblem ? Simulation

OK ?

Recurrent problem ?

N timesCheck ?

With QOS ?



1.6 Deducing the right team for intervention Coverage problem

> Coverage problem:• If the field reality does not match the RNP prediction

– Maintenance team to change physical configuration (tilt, azimuth, antenna height, etc.) and drive test team to check it

• If the field reality matches the RNP prediction– Deployment team to add sites (tri-sector, micro cellular,

indoor cells)



1.6 Deducing the right team for intervention Others problems

> Interference problem:• Planning team to identify the interference source and correct it

(joker frequency, new frequency planning, etc.)

> Unbalanced power budget problem:• Maintenance team to check the impacted BTS (Antennae, TMA,

RF cables, LNA, diversity system, etc.)

> TCH Congestion problem:• Traffic team (theoretically always in relation with the marketing

team) to manage the need of TRX extension, densification policy, etc.



1. Typical radio problems Training exercise

Time allowed:

10 minutes

High rate of UL QUAL HO causesGood RxLev and Bad RxQualVSWR alarm (OMC-R) (Voltage Standing Wave Ratio)

Bad RxLev and Bad RxQual

OMC QOS indicators: % TCH ASS failure high % call drop high

% QUAL HO % call drop % call failure

Unbalanced Power Budget Bad coverage Interferences TCH

Congestion

High Path-loss difference between UL and DLLow incoming HO success rate


2 ALGORITHMS AND ASSOCIATED PARAMETERS



2 ALGORITHMS & ASSOCIATED PARAMETERS Session presentation

> Objective: to be able to describe the Power control and Hand-over algorithms and list the associated parameters

> Program:2.1 Theoretical presentation2.2 Radio measurements principles2.3 Averaging windows and book-keeping2.4 Radio Link Supervision and Power control2.5 Handover Detection2.6 Handover Candidate Cell Evaluation2.7 Handover Management2.8 Exercise



JUSTIFICATIONWhen the detected problem does not concern another team (Network

planning and frequency planning, Dimensioning, Radio engineering, Maintenance) or

when the other teams cannot give any solution (too tight frequency planning, no additional TRX available, no financial budget for new sites, etc.)

the Radio Fine Tuning team has to find a compromise between: – High traffic density (Erl/km²/Hz)– High quality of service (Call drop, CSSR, Speech quality,

indoor, etc.)

Its role: take charge of radio resources management process> This process can be fully described by Power Control and Handover

algorithms. In-depth knowledge of these algorithms is required for tuning

2.1 Theoretical presentation Justification



2.2 Radio measurements principles



2.2 Radio measurements principlesRadio measurement mechanisms (1/2)

> MS connected (TCH or SDCCH)> The serving cell gives the MS the list of the neighbor cells to

listen to> Every SACCH, the MS reports to the serving cell: measurement

report message• Received level of 6 best cells

(which can change)• DL level and quality

of serving cell

Best cellBest cell

Best cell Best c ellC ell

C ell

Best cell

Cell

Best cellS

erv

in

g cellSYS_INFO_5

message (list)

MS reporting



> For each MS connected to the BTS (TCH or SDCCH)• UL received level and quality

is measured every SACCH• The Timing Advance (TA) is computed• The UL information is gathered

into the measurement report• This is the message result sent by the BTS to the

BSC

• The BSC is computing algorithms

• usually using average value (sliding window) of these measurements

2.2 Radio measurements principlesRadio measurement mechanisms (2/2)

BSC

MS

DL measurements

UL+DL measurements

BTS

Measurementreport

Measurementresult

Candidate cellevaluation

Measurements Active channelpreprocessing

Candidate cellevaluationHO & PCdecision

Candidate cellevaluation

PC execution

HO execution



2.2 Radio measurements principlesStructure of a measurement result

CHAN_NUMBER_IEID

FREQ(5) / BSIC(5) / RXLEV_NCELL(6)

Meas_result_number_IEIDMeas_result_numberElement IdentifierLength

{2} / RXLEV_UL_SUB_{2} / RXQUAL_UL_FULL / RXQUAL_UL_SUBBS_POWER_IEID{3} / BS_POWERElement IdentifierMS_TXPWR_CONF / R{3}TOA / R{2}Element IdentifierLengthLength

BA_USED / DTX_UL / RXLEV_DL_FULL0 / MEAS_VALID / RXLEV_DL_SUB0 / RXQUAL_DL_FULL / RXQUAL_DL_SUB / NO_NCELL_MNO_NCELL_M / RXLEV_NCELL(1)FREQ(1) / BSIC(1)BSIC(1) / RXLEV_NCELL(2)RXLEV_NCELL(2) / FREQ(2) / BSIC(2)BSIC(2) / RXLEV_NCELL(3)RXLEV_NCELL(3) / FREQ(3) / BSIC(3)BSIC(3) / RXLEV_NCELL(4)

0 / Message Type{7}

RXLEV_NCELL(5) / FREQ(5)


SACCH_BFI / DTX_DL{1} / RXLEV_UL_FULL

CHANNEL_NUMBER


MSG_TYPEMSG_DISK

TI {4} / Prot. Disc{4}

BSIC(4) / RXLEV_NCELL(5)

FREQ(6) / BSIC(6)

L1 Info

L3 Info:

Measurement report from

the MS



> Extended Measurement Reporting mechanisms• Extended Measurement

Order includes the MAFA frequencies the MS is asked to measure

• EMO sent once to the MS on SACCH after TCH seizure

• Extended Measurement Results include the average signal level measured on each MAFA frequency over one SACCH mf duration

• EMR received once per call on SACCH

2.2 Radio measurements principlesExtended Measurement Reporting (EMR)

Channel Activation Acknowledge

Assignment RequestPhysical Context Request

Physical Context Confirm

Channel Activation (TCH)(EMO included)

TCH ESTABLISHMENTTCH

Assignment CompleteAssignment Complete

Assignment CompleteSACCH

SACCH

SACCH

SACCH

SACCH (EMO)(MAFA Freq. List)

SACCH (EMR)(MAFA Freq. RxLev)

TCH ASSIGNMENT (OC or TC)

MS BTS BSC MSC



Time allowed: 5 minutes

• (BSIC, BCCH index)/(LAC, CI) problem

– As LAC and CI information take up too much space, the MS only reports the decoded BSIC and the BCCH index when it sends measurement on the adjacent cell

– The BSC makes the correspondence between the couple (BSIC, BCCH index) and the real neighbor cell concerned [completely defined by (LAC,CI)]

– WHAT IS THE RISK?

2.2 Radio measurements principlesTraining exercise (1/2)



2.2 Radio measurements principlesTraining exercise (2/2)

> Explain why cell 2 has a very high outgoing HO unsuccessful rate and a high call drop

Cell 2

Cell 1

Cell

(7, 62)

CI=1964GSM900

Cell 3

CI=6169GSM900

(7, 62)

(3, 46)

Cell

CI=6169GSM900



2.3 Radio measurements data processing



2.3 Radio measurements data processingFunctional entities

BSC

Active ChannelPre-processing

BTS

Radio LinkMeasurements

Assignment of radio measurements data processing functions in the ALCATEL BSS



> Active channel pre-processing

• ACTIVATED EACH TIME A MEASUREMENT IS RECEIVED

• AVERAGING VALUES OF SIGNAL LEVELS, QUALITIES, TIMING ADVANCE

– USING “SLIDING WINDOW” TECHNIQUE

• BUILDING A BOOK-KEEPING LIST OF NEIGHBOR CELLS– The MS is reporting the 6 best cells at one time– They can change from 1 measurement to another– Maximum for 1 call: last 32 best ones (among 64 maximum

declared as neighbor)

2.3 Radio measurements data processingActive channel pre-processing



> Active channel pre-processing – Principles• HANDLED by the BSC• ACTIVATED when the BSC receives:

– ESTABLISH INDICATION from the MS on SAPI 0, or– HANDOVER FAILURE from the MS, or– ASSIGNMENT FAILURE from the MS (in case of intracell

handover)• STOPPED when a HANDOVER COMMAND is emitted in the

serving BSC

• AVERAGING VALUES OF SIGNAL LEVELS, QUALITIES, TIMING ADVANCE

– USING “SLIDING WINDOW” TECHNIQUE• BUILDING A BOOK-KEEPING LIST OF NEIGHBOR CELLS

2.3 Radio measurements data processingActive channel pre-processing - Principles



> Avoid reacting too early to some “atypical” measurement(s)

2.3 Radio measurements data processingMeasurement averaging (1/2)

75.00

80.00

85.00

90.00

95.00

100.00

105.00-------



> Objective: average measurements to avoid reacting to transient degradation

• Principle: sliding window: level/quality/distance values are averaged for N last samples

N = A_LEV_HO samples for uplink and downlink levelN = A_QUAL_HO samples for uplink and downlink qualityN = A_RANGE_HO samples for distanceN = A_PGBT_HO for level used in power budget equation

• Example (A_LEV_HO=6, A_QUAL_HO=4, A_PBGT_HO=8)

• Experiences• some experiments have shown that the number of HOs is very sensitive to modification of these values

2.3 Radio measurements data processingMeasurement averaging (2/2)

DL LevelAV-RxLevAV-Lev-PGBTDL Qual

AV-RxQual

1 2 3 4 5 6 7 8 9 10 11 12

13

14

15 16 17

18 19

20

21 22

23 24

Meas

2 3 3 43

74

-9575

-99

-90 -92

-93 -98

-100

-98

-90 -80-

97-96 -94-95 -94

7 5 26 7 5

-75

-72 -71 -110 -70-

90-86 -81 -83 -80

-92

-89 -86 -87 -831 1 0 6 04 2 1 2 2

-69-78-8002

-68 -78 -88 -95-77 -78 -81 -78-77 -77 -78 -810 0 1 22 0 0 1

-98-83-8532

-100-110-110-88 -95 -100-83 -88 -936 7 73 5 6

-110-104-9977



> BUILDING A BOOK-KEEPING LIST OF NEIGHBOR CELLS– The MS reports the measurements of the NO_NCELL_M

(≤ 6) best cells every multi-frame– The adjacent cells reported by the MS can change from one

measurement to another– The book-keeping function keeps a table of the last 32

reported adjacent cells– Clearing process of non-reported neighbors during 10s

(signal level=0)

2.3 Radio measurements data processingneighbor cell measurement book-keeping



2.3 Radio measurements data processingTraining exercise

> Measurements averaging• With ‘averaging window’

excel sheet...• Compute averaging on quality,

distance and level• Make charts with different sliding

averaging windows


Raw measurements

Average measurements

AV_RXLEV_DL_HOA_LEV_HO=8

A_LEV_HO=2

2 3 4 5 6 7 8 9 10 11 12 13 14 151-75

-80

-85

-90

-95

Number ofmeasurements

Level

AV_RXQUAL_DL_HO

3

A_QUAL_HO=8

A_QUAL_HO=2

2 3 4 5 6 7 8 9 10 11 12 13 14 151

4

3

2

1

0

Quality

AV_RANGE_HO

10

12

15

A_RANGE_HO=8

A_RANGE_HO=2

2 3 4 5 6 7 8 9 10 11 12 13 14 151

25

20

15

10

5

Distance

DL LevelA_LEV_HO=8A_LEV_HO=4A_LEV_HO=2

DL LevelA_QUAL_HO=8A_QUAL_HO=4A_QUAL_HO=2

DL LevelA_RANGE_HO=8A_RANGE_HO=4A_RANGE_HO=2

-80210

-782

11

-8439

-873

11

-80213

-75112

-774

14

-944

15

-793

16

-77117

-782

18

-843

17

-89319

-90320

-914

19

DL LevelDL QualityDistance

-80-76

-82-82-86

-82-81-87

-82-82-78

-81-82-78

-81-80-81

-82-82-87

-84-85-90

-85-89-91-81

-82-86

-82-84

-82-78-79

A_LEV_HO=4



323

323

333

334

334

334

332

332

33

22

332 3

A_QUAL_HO=4 3

131416

131617

151718

151718

161818

171920

181920

1112

1113

1313

1411 10

A_RANGE_HO=4 10



2.4 Radio Link Supervision and Power Control



2.4 Radio link supervision and power controlFunctional entities

BSCBTS

Radio LinkSupervision

PC CommandPC ThresholdComparison

Radio LinkCommand



Assignment of PC functions in the ALCATEL BSS



> Principles

• Detection (by BTS) of a radio link failure with an MS

– notification to BSC for radio resource release

• Try to recover an MS when radio becomes poor

– optional mechanism “radio link recovery”– by requiring BTS and MS to transmit at maximum power

• Equivalent mechanism in MS for Radio Link Failure detection

2.4 Radio link supervision and power controlRadio link supervision



2.4 Radio link supervision and power controlPrinciples of radio uplink supervision

> For each active radio channel, a counter “S” is• decremented by 1 each time an SACCH frame cannot be decoded

(BFI=1)• incremented by 2 each time a valid SACCH frame is received

> The value of S gives a measure of the “quality” of uplink radio link> Initial value of S = BS_RADIO_LINK_TIMEOUT

• if S reaches N_BSTXPWR_M, a radio link recovery is triggered optional)

• if S reaches 0, a radio link failure is detected> RADIOLINK_TIMEOUT_BS ≥ RADIOLINK_TIMEOUT is important

because the mobile must release the radio channel first.M SBT

SC o u n ter S C o u n ter S '

R L T O _ B S(B S _ R A D IO _ L IN K _T IM E O U T ) 18

16 R L T O (T 1 0 0 )(R A D IO _L IN K _ T IM E O U T )

N _B ST X P W R _ M 13 R ad io lin k

R ec o v e ry

S A C C H b lo cklo s t: - 1

S A C C H b lo c krec e iv ed : + 2

0 0R a d io lin kF a ilu re



2.4 Radio link supervision and power controlS counter for radio link supervision

SACCHnumber

S value

29282726252423222120191817161514131211109876543210

5

10

15

20

25

RADIO_LINK_TIMEOUT_BS

N_BSTXPWR_M

SBFI

S = f [ BFI (t) ]



> The BTS is sending a Connection Failure Indication message– cause ‘001 1111’ reserved for national usage (ALCATEL:

RLR)– On K1205: “set MS/BS_TXPWR_MAX (Alcatel only)”

> The BSC is sending BS and MS POWER CONTROL messages– required for maximum possible values– The MS required level is embedded in the SACCH header

in the downlink

> Optional mechanism– EN_RL_RECOV =ENABLE– useless without power control– “master” vs. power control

2.4 Radio link supervision and power controlRadio link recovery



> Radio link failure

• The BTS is sending a Connection Failure Indication message– Cause ‘radio link failure’

• The BSC is notifying the loss to the MSC– Usually Clear Request “radio interface failure”

• The BSC is releasing locally the radio resource (TCH or SDCCH)– Radio frequency Channel Release message sent to BTS

• The call is dropped !

2.4 Radio link supervision and power controlRadio link failure



2.4 Radio link supervision and power controlRadio link supervision: training exercise

> With the “RLS” excel sheet...• Taking into account the

measurements with BFI andthe parameter values (N_BSTXPWR_Mand RADIOLINK_TIMEOUT_BS)

• Indicate when – A radio link recovery is triggered– A radio link failure is triggered


0

1

1000

01111

1101

0111111101

1

1

0

1

0

1

1

1

1

1

18

5

17181818

1817161514

12111312

1211109876576

10

6

8

17

18

4

11

7

3

13 Radio Link Recovery

BFI S Action

Radio Link Supervision

N_NSTXPWR_MAXRLTO_BS

1318

Parameters:



> Aims of Power control• Reduce emitted power to the

minimum possible

• Minimum power levels:– GSM: 11dBm, 9dBm, 7dBm

and 5dBm– DCS: 2dBm, 0dBm

• Ensuring quality and received level of peer entity

• Adapted in real-time• For Uplink PC: decrease UL

interference and save MS battery• For Downlink PC, decrease DL

interference

2.4 Radio link supervision and power controlPower control

Output Power (dBm)GSM-900

Output Power (dBm)DCS-1800

Powerlevel

14

15

16

17

18

19

15

13

11

9

7

5

2

0

-

-

-

-

BTS MS

Uplink

RXLEV_UL

MS_TXPWRDownlink

BS_TXPWR

RXLEV_DL



> Based on a threshold comparison mechanism

> Decrease emitted power when received level AND quality measured by peer entity are better than a given value

> Increase emitted power when the received level OR quality is lower than a given value

> Does not decrease power if the resulting level is below the low level threshold

FEATURE REAL FAST PC GIVES REACTIVITY TO THE ALGORITHMS

2.4 Radio link supervision and power controlPower Control principles



> MS Power control (for BS PC, replace MS by BS and UL by DL)

2.4 Radio link supervision and power controlPower Control detection

U_RXQUAL_UL_P

L_RXQUAL_UL_P

1

2

-95 -93 -85

L_RXLEV_UL_P

POW_RED_STEP_SIZE

U_RXLEV_UL_P

Quality

Level

-90 -75-94

3



> Power increase: If• AV_RXQUAL_UL_PC > L_RXQUAL_UL_P +

OFFSET_RXQUAL_FH• AV_RXQUAL_UL_PC ≤ L_RXQUAL_UL_P +

OFFSET_RXQUAL_FHand AV_RXLEV_UL_PC < L_RXLEV_UL_P

Then PC_COMMAND(MS, INC, MS_P_INC dB, <min(MS_TXPWR_MAX, P))

> Power decrease: If• AV_RXQUAL_UL_PC < U_RXQUAL_UL_P

and AV_RXLEV_UL_PC >= L_RXLEV_UL_P + POW_RED_STEP_SIZE

• AV_RXQUAL_UL_PC ≤ L_RXQUAL_UL_P + OFFSET_RXQUAL_FHand AV_RXQUAL_UL_PC ≥ U_RXQUAL_UL_P

d AV RXLEV UL PC U RXLEV UL P

2.4 Radio link supervision and power controlMS PC Threshold comparison



> Power command philosophy:

• Target received level TARGET_RXLEV_UL– middle threshold between U_RXLEV_UL_P and

L_RXLEV_UL_P

• Adaptive power step size– According to the average received level– Limited power step size to MAX_POW_INC and

MAX_POW_RED– If only Quality problem: fixed power step size

– POW_INC_STEP_SIZE and POW_RED_STEP_SIZE – Two weighting factors to modify the algorithm reactivity when

level problem– POW_INC_FACTOR for power increase– POW_RED_FACTOR for power decrease

2.4 Radio link supervision and power controlMS Power Control Command



2.4 Radio link supervision and power controlFast and Normal PC comparison

> Example

4800 960 1440 1920 2400

-110

-100

-90

-80

20 dB

Time(ms)

Power level(dB)

6 dB (POW_INC_STEP_SIZE)

4 SACCH =1 Measurement Report (MR)

MR 2 MR 3 MR 4

Need for PC Command detected

PC Command

Normal Power Control

Fast Power Control



> PC_COMMAND (MS, INC, MS_P_INC dB, < power max)• If MS_TXPWR < power maxthen increase MS_TXPWR by min(MS_P_INC, MAX_POW_INC,

powermax-MS_TXPWR)• Where MS_P_INC is evaluated by the following algorithm:

if (AV_RXLEV_UL_PC < L_RXLEV_UL_P) (problem of level)if (AV_RXQUAL_UL_PC ≤ L_RXQUAL_UL_P +

OFFSET_RXQUAL_FH) (sufficient quality)then MS_P_INC = roundup[ POW_INC_FACTOR*

(TARGET_RXLEV_UL -AV_RXLEV_UL_PC)]else MS_P_INC = roundup[ MAX ( POW_INC_FACTOR *

(TARGET_RXLEV_UL - AV_RXLEV_UL_PC ), POW_INC_STEP_SIZE )]

else (problem of quality)MS_P_INC = POW_INC_STEP_SIZE

2.4 Radio link supervision and power controlMS Power Increase Command computation



> PC_COMMAND (MS, RED, MS_P_RED dB, > power min)• If MS_TXPWR > power minthen decrease MS_TXPWR by min(MS_P_RED, MAX_POW_RED,

MS_TXPWR- power min)• Where MS_P_RED is evaluated by the following algorithm:

if (AV_RXLEV_UL_PC > U_RXLEV_UL_P) (good level)if (AV_RXQUAL_UL_PC ≥ U_RXQUAL_UL_P) (sufficient

quality)then MS_P_RED = roundup[ MAX(POW_RED_FACTOR*

(AV_RXLEV_UL_PC- TARGET_RXLEV_UL)), 2dB]else MS_P_RED = roundup[ MAX ( POW_RED_FACTOR *

(AV_RXLEV_UL_PC- TARGET_RXLEV_UL), POW_RED_STEP_SIZE )]

else (good quality)MS_P_RED = POW_RED_STEP_SIZE

2.4 Radio link supervision and power controlMS Power Decrease Command computation



> OFFSET_RXQUAL_FH

• This variable allows to take into account the frequency hopping in the RxQual evaluation (see Annex 2)

• Defined on a per cell basis

• Algorithm:If Frequency hopping applied – then OFFSET_RXQUAL_FH = Offset_hopping_PC– Else OFFSET_RXQUAL_FH = 0

2.4 Radio link supervision and power controlFrequency Hopping cases

Annex 2



> Timers

• T_SDCCH_PC allows the inhibition of PC on SDCCH

• When a new power is required, the confirmation is awaited: – MS_P_CON_ACK– BS_P_CON_ACK

• As soon as the new power is acknowledged, a fixed duration is awaited to trigger a new change of power, if necessary:

– MS_P_CON_INT– BS_P_CON_INT

2.4 Radio link supervision and power controlPower Control timers (1/2)



> IF xx_P_CON_ACK is expiring, it is a system problem: • Wrong setting of xx_P_CON_ACK (too short)• No reception of power command by the MS

– a radio link recovery can be activated• Problem on Abis

– repetition of BS power command

> The expiry of P_CON_INT is a normal mechanism

2.4 Radio link supervision and power controlPower Control timers (2/2)



> LEVEL and QUALITY USED in EQUATION are average ones with window size A_QUAL_PC and A_LEV_PC

> BS POWER CONTROL INHIBITED ON BCCH frequency– BCCH must be emitted at the maximum level

> MS dynamic constraint– minimum 2dB every 60 ms

> Emitted power can be changed by radio link supervision algorithm– Radio link supervision has a greater priority

> Activation of power control can slow down HO decision– some causes can be triggered only if the MS (BTS) is

emitting at the maximum power

2.4 Radio link supervision and power controlExtra information



2.4 Radio link supervision and power controlPower Control: Training exercise (1/3)

> Power control UL(Remark: Use the default parameters document)

• What happens if we do not use Frequency Hopping?

• Why is it better to have A_LEV_PC=A_LEV_HO/2?• Thresholds:

– Lower QUAL of RX uplink = 3– High QUAL of RX uplink = 2– Lower LEV of RX uplink = -90dBm– Upper LEV of RX uplink = -75dBm– POW_RED_STEP_SIZE= 4– POW_INC_STEP_SIZE= 6

• Put the right threshold in the next slide chart




2.4 Radio link supervision and power controlPower Control: Training exercise (2/3)> Power control UL

QUESTION

For each case:• PC triggered?• Step size value?

With POW_INC_FACTOR = 0,6and POW_RED_FACTOR = 0,6and MAX_POW_INC = MAX_POW_RED = 8

Quality

Level

Nb of case

AV RXQUAL UL PC

AV RXLEV UL PC

Power control

Delta value

1 2 3 4 5 6

0 1 2 6 3 4

-98 -80 -73 -69 -86 -91



2.4 Radio link supervision and power controlPower Control: Training exercise (3/3)

> Power control DL• Thresholds:L_RXLEV_DL_P = -85dBm POW_INC_FACTOR = 0.6

U_RXLEV_DL_P = -75dBm POW_RED_FACTOR = 0.8

L_RXQUAL_DL_P = 2.9 MAX_POW_INC = 16dBU_RXQUAL_DL_P = 1 MAX_POW_RED = 16dBA_QUAL_PC = 4 BS_P_CON_ACK = 3sA_LEV_PC = 4 BS_TXPWR_MIN = -16dB

• Using the Trace Abis Excel file, find each parameter value:POW_INC_STEP_SIZE = ? BS_P_CON_INT = ?POW_RED_STEP_SIZE = ? OFFSET_RXQUAL_FH = 0 or 1

?

• Which phenomenon can you observe as regards the successive PC commands?



2.5 Handover Detection



2.5 Handover DetectionHandover main objective

> Send connected MS to another cell• When needed: “rescue/emergency” handover• If useful: “better cell” handover

> Toward the “best” cell• From a radio point of view

– Power budget– Level

• From a traffic point of view– Less loaded target

• From a dynamic point of view– MS speed– “History” of the call

• From an operator point of view



> The BSC is analyzing averaged measurement results– active channel pre-processing (measurements averaging

and book-keeping)

> To detect need/utility to handover– Handover detection process

> To choose/rank target cells according to several criteria– Candidate cell evaluation process

> To perform the handover– Handover management process

2.5 Handover DetectionPrinciples



2.5 Handover DetectionFunctional entities

BSCBTS


HO Detection


HO Preparation

HO CandidateCell Evaluation

HO Management

HO Protocol

MSC

Assignment of HO functions in the ALCATEL BSS



> Based on the contents of the measurement results

> The BSC is computing the need or utility to trigger a handover

> HO causes 25, split into 2 main categories: • Emergency handover

– quality, level, distance, etc.• Better cell handover

– power budget, traffic, etc.

> Some are specific to hierarchical and concentric architectures

2.5 Handover DetectionHandover causes detection



2.5 Handover DetectionHandover causes

> HO causes for standard networksEmergency HO

Cause 2Cause 3Cause 4Cause 5Cause 6

Cause 10

Cause 11

Cause 15

Cause 16

Cause 26

Too low quality on the uplinkToo low level on the uplinkToo low quality on the downlinkToo low level on the downlinkToo long distance between theMS and the BTSToo low level on the uplink inthe inner zoneToo low level on the downlink inthe inner zoneHigh interference on the uplink(intracell HO)Aigh interference on the downlink(intracell HO)AMR channel adaptation HO(HR to FR)

Better conditions HO

Cause 12Cause 13

Cause 20Cause 23

Cause 24

Cause 27

Cause 28Cause 29

Power budget evaluationOuter zonelevel Uplink &DownlinkForced directed retryTraffic(Modified in B8)General capture(Modified in B8)AMR channel adaptationHO (FR to HR)Fast traffic HOTFO HO

30 Move from PS to CS zone



> CAUSE 2: too low quality on the Uplink

AV_RXQUAL_UL_HO > L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO <= RXLEV_UL_IHand MS_TXPWR = min (P, MS_TXPWR_MAX)and EN_RXQUAL_UL= ENABLE

• Size of window for averaging quality: A_QUAL_HO• Size of window for averaging level: A_LEV_HO

2.5 Handover DetectionHandover Cause 2: UL Quality

Quality

Level



> CAUSE 3: too low level on the uplink

AV_RXQUAL_UL_HO <= L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO < L_RXLEV_UL_Hand MS_TXPWR = min (P, MS_TXPWR_MAX)and EN_RXLEV_UL= ENABLE


2.5 Handover DetectionHandover Cause 3: UL Level

Quality

Level



> CAUSE 4: too low quality on the downlink

AV_RXQUAL_DL_HO > L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_DL_HO <= RXLEV_DL_IHand BS_TXPWR = BS_TXPWR_MAXand EN_RXQUAL_DL= ENABLE


2.5 Handover DetectionHandover Cause 4: DL Quality

Quality

Level



2.5 Handover DetectionHandover Cause 5: DL Level> CAUSE 5: too low level on the downlink

• AV_RXQUAL_DL_HO <= L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

• AV_RXLEV_DL_HO < L_RXLEV_DL_H• BS_TXPWR = BS_TXPWR_MAX• and EN_RXLEV_DL= ENABLE


Quality

Level



> CAUSE 6: Too long distance between the MS and the BTS

AV_RANGE_HO > U_TIME_ADVANCEand EN_DIST_HO= ENABLE

• Size of window for distance averaging: A_RANGE_HO

2.5 Handover DetectionHandover Cause 6: Distance

Too long distanceBTS



> Emergency handovers specific to concentric cells• Intracell handovers from inner to outer zone• cause 10: too low level on the uplink in inner zone• cause 11: too low level on the downlink in inner zone

> May be triggered– From inner zone of a concentric cell– Towards outer zone, same cell

2.5 Handover DetectionHandover algorithms for concentric cells

Concentric cell

I n n e r z o n e

Outer zone



> CAUSE 10: too low level on the uplink in the inner zone

AV_RXLEV_UL_HO < RXLEV_UL_ZONEand MS_TXPWR = min (P, MS_TXPWR_MAX_INNER)

• Averaging window: A_LEV_HO

2.5 Handover DetectionHandover algorithms for concentric cells: cause 10



> CAUSE 11: too low level on the downlink in the inner zone

AV_RXLEV_DL_HO < RXLEV_DL_ZONEand BS_TXPWR = BS_TXPWR_MAX_INNER

• Averaging window: A_LEV_HO

2.5 Handover DetectionHandover algorithms for concentric cells: cause 11



> CAUSE 13: too high level on UL and DL in the outer zone• Better condition intracell handover• If the cell is a multi-band cell, cause 13 is checked only for multi-

band MSs

> May be triggered– From outer zone of a concentric cell– Towards inner zone, same cell

2.5 Handover DetectionHandover algorithms for concentric cells: cause 13 (1/6)

Concentric cell

I n n e r z o n e

Outer zone



> CAUSE 13: too high level on UL and DL in the outer zone

AV_RXLEV_UL_HO > RXLEV_UL_ZONE ++ ZONE_HO_HYST_UL ++ (MS_TXPWR -

MS_TXPWR_MAX_INNER) ++ PING_PONG_MARGIN(0,call_ref)

and AV_RXLEV_DL_HO > RXLEV_DL_ZONE ++ ZONE_HO_HYST_DL ++ (BS_TXPWR - BS_TXPWR_MAX_INNER)

++ PING_PONG_MARGIN(0,call_ref)

and AV_RXLEV_NCELL_BIS(n) <= neighbour_RXLEV(0,n)and EN_CAUSE_13 = ENABLE (B7)and EN_BETTER_ZONE_HO = ENABLE

• Averaging windows: A_LEV_HO and A_PBGT_HO (for n)




> ZONE_HO_HYST_UL• UL static hysteresis for interzone HO from outer to inner

– In case of multi-band cell, should take into account the difference of propagation between GSM and DCS

• Added to cause 10 threshold RXLEV_UL_ZONE

> ZONE_HO_HYST_DL• DL static hysteresis for interzone HO from outer to inner

– In case of multi-band cell, should take into account the difference of propagation between GSM and DCS and the difference of BTS transmission power in the two bands

• Added to cause 11 threshold RXLEV_DL_ZONE




> PING_PONG_MARGIN(0,call_ref)• Penalty PING_PONG_HCP put on cause 13 if

– The immediately preceding zone in which the call has been is the inner zone of the serving cell

– And The last handover was not external intracell– And T_HCP is still running

• PING_PONG_MARGIN(0,call_ref) = 0– If the call was not previously

in serving’s inner zone– Or T_HCP has expired


Concentric cell

I n n e r z o n e

Outer zone



> neighbour_RXLEV(0,n)

• Concentric cells are designed to create an INNER zone

– protected from external interferers– and creating no interferences on other cells– … to be able to face more aggressive frequency reuse in

INNER zone TRXs• neighbour_RXLEV(0,n) tuning enables to avoid handovers if the

MS position will lead to interferences• the condition is checked towards all neighbor cells belonging to

the same layer and band than the serving cell


Concentric cellOuter zone

?

Inner zoneinterferer 1

Inner zoneinterferer 2Inner zone



> EN_CAUSE_13• Load balance between inner and outer zones may be allowed by

setting EN_LOAD_BALANCE = ENABLE

• If EN_LOAD_BALANCE = ENABLE– If INNER zone is less loaded than OUTER,

EN_CAUSE_13 = ENABLE– If INNER zone is more loaded than OUTER,

EN_CAUSE_13 = DISABLE

• If EN_LOAD_BALANCE = DISABLE– EN_CAUSE_13 = ENABLE




> Outgoing intercell handovers from concentric cells• As explained here before, the MS located in a

concentric cell can make intercell, emergency orbetter condition HO regardless their current zone

– For example, an MS locatedin the INNER zone of aconcentric cell can makedirectly a HO cause 12towards another cell,WITHOUT having totrigger any cause 10 or 11to the OUTER zone before.

2.5 Handover DetectionOutgoing intercell handovers from concentric Cell


Inner zone


Inner zone


Inner zone



> Incoming intercell handovers towards a concentric cell• In case an MS is making an incoming handover towards a

concentric cell (due to outer PBGT measurements,etc.), a TCH maybe allocated

– either in the INNER or in the OUTER zone, as for call setup– depending on radio conditions

• In case of a multi-band cell, if the MS is not multi-band, it will always be sent to the OUTER zone

2.5 Handover DetectionIncoming intercell handovers towards Concentric Cell

(1/2)


Inner zone

Cell

??



> Use part of Handover cause 13 algorithm on each potential target> IF Cell(n) is external

– The MS is directed to the OUTER zone of (n)> ELSE (cell(n) is internal)

• IFAV_RXLEV_NCELL(n) > RXLEV_DL_ZONE + ZONE_HO_HYST_DL

++ (BS_TXPWR - BS_TXPWR_MAX_INNER)

and EN_BETTER_ZONE_HO = ENABLE

– The MS is directed towards the INNER zone• ELSE

– The MS is directed towards the OUTER zone

2.5 Handover DetectionIncoming intercell handovers towards Concentric Cell

(2/2)



> CAUSE 12: Power budget• Decision based mainly on comparison of serving and neighbor

cells for: – downlink level of serving and neighbor cells– maximum emitting level of MS

• Aiming at decreasing UL & DL emitted power

• Should be the “normal” handover type– no matter of emergency

2.5 Handover DetectionHandover Cause 12: Power Budget (1/11)



> CAUSE 12: Power budget equation

PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO - (BS_TXPWR_MAX – AV_BS_TXPWR_HO)- (MS_TXPWR_MAX(n) – MS_TXPWR_MAX)- PING_PONG_MARGIN(n, call_ref)




> CAUSE 12: Power budget

• AV_RXLEV_NCELL– received level of BCCH of neighbor cell

• AV_RXLEV_PBGT_HO– received level of serving cell (BCCH or not)

• AV_RXLEV_NCELL - AV_RXLEV_PBGT_HO– the highest is the best neighbor cell– but serving might not be at the maximum level (with DL

power control)– necessity to have a corrective factor


PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO - (BS_TXPWR_MAX –

AV_BS_TXPWR_HO)- (MS_TXPWR_MAX(n) –

MS_TXPWR_MAX)- PING_PONG_MARGIN(n, call_ref)




• BS_TXPWR_MAX – AV_BS_TXPWR_HO

– BS_TXPWR_MAX are attenuations, not absolute level– = (“bts_max_power”+BS_TXPWR_MAX) -

(“bts_max_power”+AV_BS_TXPWR_HO)– AV_BS_TXPWR_HO: average of BS_POWER over

A_PBGT_HO measurements– corrective factor used to compensate for the fact that the

serving cell may not emit at the maximum level

• AV_RXLEV_NCELL-[AV_RXLEV_PBGT_HO+(BS_TXPWR_MAX-AV_BS_TXPWR_HO)]

– compare received level of neighbor and serving cells as if the serving one was emitting at the maximum level







2.5 Handover DetectionHandover Cause 12: Power Budget (5/11)> CAUSE 12: Power budget

• MS_TXPWR_MAX(n)– maximum emitting power for the MS in neighbor cell n

• MS_TXPWR_MAX– maximum emitting power for the MS in the serving cell

> MS_TXPWR_MAX(n) - MS_TXPWR_MAX• Corrective factor to compensate for the difference of maximum

power of each cell• MS_TXPWR_MAX(n) - MS_TXPWR_MAX = bts_max_power(n)

- bts_max_power– which should be the case if delta_path_loss is equilibrated– if not exact, can be corrected with HO_MARGIN(0,n)







• Hysteresis to avoid ping-pong HO

• Static hysteresis defined for each couple of cells:HO_MARGIN (0,n)

– can also be used to correct delta_path_loss

• “Dynamic” penalty for call coming from cell n: ping_pong_margin(n,call_ref)

– penalty applied during a limited duration: T_HCP– not used if call arrived with a forced directed retry– penalty defined on a cell basis







> CAUSE 12: Power budget• ping_pong_margin example


Cell Cell Cell

Case 1

Case 3

Case 2

OK1

Ping-pong in normal case OK with ping_pong_margin

Not a ping-pong case OK with ping_pong_margin and T_HCP

2

3




> If EN_TRAFFIC_HO(0,n)=ENABLE> Then

PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER+ max(0, DELTA_HO_MARGIN(0,n))

(n=1…BTSnum)> Else PBGT(n) > HO _MARGIN(0,n)

+OFFSET_HO_MARGIN_INNER

> AND AV_RXLEV_PBGT_HO ≤ RXLEV_LIMIT_PBGT_HO

> AND EN_PBGT_HO = ENABLE> Size of window for level averaging: A_PBGT_HO




> Mechanism to avoid PBGT HO if the level from the serving cell is high enough

> RXLEV_LIMIT_PBGT_HO: threshold above which it is not necessary to trigger a handover on power budget

> AV_RXLEV_PBGT_HO: average of the received levels over A_PBGT_HO measurements

> Specific to particular algorithms (not mentioned in this course)> OFFSET_HO_MARGIN_INNER: offset which allows to take into

account the radio differences between outer and inner zones (especially in case of multi-band cells)




> Specific to traffic considerations> DELTA_HO_MARGIN(0,n): evaluated according to the traffic situation

of the serving cell and the neighbor cell n (Traffic_load(n)) in the following way:

> If Traffic_load(0) = high and Traffic_load(n) = low, – DELTA_HO_MARGIN(0,n) = - DELTA_DEC_HO_margin

> If Traffic_load(0) = low and Traffic_load(n) = high,– DELTA_HO_MARGIN(0,n) = DELTA_INC_HO_margin

> Else – DELTA_HO_MARGIN(0,n) = 0

> Philosophy> This mechanism aims at penalizing cause 12 detection when the

traffic in the serving cell is low and is high in the cell n.




> Traffic_load() is a function managed for every cell of a BSC> Traffic_load() can have three values:

• high: cell is loaded• low: cell is unloaded• indefinite: cell is neither loaded nor unloaded

> Traffic_load() value is modified according to the long term traffic evaluation algorithm using the following parameters:

• A_TRAFFIC_LOAD, N_TRAFFIC_LOAD, HIGH_TRAFFIC_LOAD, IND_TRAFFIC_LOAD, LOW_TRAFFIC_LOAD: can be modified per cell

• TCH_INFO_PERIOD: cannot be modifiedAnnex 3



2.5 Handover DetectionHandover Cause 23: Traffic (1/2)> CAUSE 23: Traffic Handover

> DELTA_HO_MARGIN(0,n) < 0dB

> AND PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGNIN_INNER + DELTA_HO_MARGI (0,n)

(n=1…BTSnum)

> AND EN_TRAFFIC_HO(0,n) = ENABLE

> Size of window for level averaging: A_PBGT_HO



2.5 Handover DetectionHandover Cause 23: Traffic (2/2)> CAUSE 23: Traffic Handover

• DELTA_HO_MARGIN(0,n) computation is already described in Cause 12 HO

• DELTA_HO_MARGIN(0,n) < 0dB means that

– The serving cell is loaded

– The target cell is unloaded

• PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

+ DELTA_HO_MARGIN(0,n) (n=1…BTSnum)

– This constraint is less discriminative than Cause 12

– In specific traffic distribution, this cause is triggered beforecause 12



2.5 Handover DetectionHandover Cause 12 & 23 interworking

> Cause 12 & 23: A dynamic way to handle traffic loadPBGT (n2)

PBGT (n1)

Traffic_loadTraffic_load(n2)=highTraffic_load(n1)=low

Other cases Traffic_load(n2)=lowTraffic_load(n1)=high

HO_MARGING(n1, n2) + DELTA_INC_HO_margin

HO_MARGING(n1, n2)

HO_MARGING(n1, n2) - DELTA_DEC_HO_margin

HO_MARGING(n2, n1) - DELTA_DEC_HO_margin

HO_MARGING(n2, n1)

HO_MARGING(n2, n1) + DELTA_INC_HO_margin

PBGT Handover

PBGT Handover

2 x HO_MARGIN+ DELTA_INC_HO_margin- DELTA_DEC_HO_margin

2 x HO_MARGIN

PBGT Handover

Traffic Handover

PBGT Handover

Traffic Handover

Handover from n1 to n2

Handover from n2 to n1

N2 loaded

N1 loaded



> Directed Retry is:• an SDCCH to TCH intercell handover• Triggered during call setup procedure

> If the serving cell is completely congested, the MS is allocated an SDCCH

> If no TCH is available, the MS is queued• Under certain conditions, the MS obtains TCH in another cell

> SDCCH-TCH handover on:• better condition or emergency causes = Directed Retry• cause 20 = Forced Directed Retry

> Internal and External Directed Retries are possible (since B6.2)

2.5 Handover Detection Directed Retry principles



> Directed Retry

• Set on a per cell basis with parameter EN_DR

• Same behavior as TCH HO

• Intercell handover causes are checked (i.e. all HO causes except 10, 11 and 13 (concentric cells) and causes 15 and 16 (intracell HO))

• candidate cell evaluation process: same as for TCH HO

2.5 Handover Detection Directed Retry



> CAUSE 20: Forced Directed Retry

AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n)And EN_FORCED_DR = ENABLE

• EN_FORCED_DR value is only relevant if EN_DR = true

• AV_RXLEV_NCELL_DR(n) is calculated with A_PBGT_DRwindow

• if less than A_PBGT_DR samples are available, the average value is calculated with the available samples and the averagingwindow is filled in with -110 dBm

2.5 Handover Detection Forced Directed Retry: cause 20



> Pre-ranking• using PREF_LAYER, PRIORITY(0,n), frequency band

> Filtering process• AV_RXLEV_NCELL_DR(n) > RXLEVmin(n)

+max(0,MS_TXPWR_MAX(n) - P)• Number of free TCHs t(n) > FREElevel_DR(n)

> Remaining cells are sorted according their PBGT_DR(n) (averagingwindow A_PBGT_DR)

• PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) -AV_RXLEV_PBGT_DR -(BS_TXPWR_MAX - BS_TXPWR)

- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

2.5 Handover Detection FDR: Candidate cell evaluation



> L_RXLEV_NCELL_DR(n): level required in the neighbor cell n– The parameter considered is the one set in the neighbor cell– The default value depends on network architecture– See next slide

> Freelevel_DR(n): number of free TCH channels required in the neighbor cell n

– The parameter considered is the one set in the neighbor cell– Default value = 0 to 4 TCHs (linked to the nb of TRXs)

> A_PBGT_DR: Averaging window– Default value = 4 SACCHs

2.5 Handover Detection FDR: parameters



2.5 Handover DetectionCause 24: general capture

Serving cellCell

Cell

Cell

Cell

> CAUSE 24: general capture

• Capture handover– Modified in B8:Inhibition of capture handovers for “Single

layer serving cell”

• May be triggered– From all cells– Towards all cells except serving– Can be used to capture traffic by any cell,

whatever its type, band, etc.



> CAUSE 24: general capture

AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) + max (0, [MS_TXPWR_MAX(n) - P])

and Traffic_load(0) = CAPTURE_TRAFFIC_CONDITIONand Traffic_load(n) ≠ HIGHand EN_GENERAL_CAPTURE_HO = ENABLE

• Size of window for averaging level: A_PBGT_HO• CAPTURE_TRAFFIC_CONDITION can take 3 values: ANY_LOAD

(default), HIGH, NOT_LOW• Anti ping-pong: not checked if T_INHIBIT_CPT is running – new in

B8 for single layer

2.5 Handover DetectionCause 24: general capture



2.5 Handover DetectionHandover Cause 28: Fast Traffic HO (1/4)> CAUSE 28: Fast Traffic HO

• Push out of a cell a mobile in dedicated mode to allow a queued request to be served in the serving cell

– Complement the current traffic HO (Cause 23), for sudden traffic peaks (no averaging window used)

– More efficient where the overlap of adjacent cells is reducedMost appropriate MS

to be pushed outNew call attempt

CongestedServing cell

Neighbor cell Cell

Neighbor cell Cell

Upper layer cell

HO

HOMost appropriate MSto be pushed out

New call attempt

CongestedServing cell



2.5 Handover DetectionHandover Cause 28: Fast Traffic HO (2/4)> CAUSE 28: Fast Traffic Handover

• Cause 28 is only checked if the channel of the candidate MS can support the channel rate (HR or FR) required by the queued request:

• HO is triggered when a request is queued at the top of the queue

Queued Request Candidate MS

HR

HR

HR orFR on dual rate TRX

FR (whatever the TRX type)



2.5 Handover DetectionHandover Cause 28: Fast Traffic HO (3/4)> CAUSE 28: Fast Traffic Handover equation

AV_RXLEV_NCELL(n) > L_RXLEV_NCELL_DR(n) + max(0,[MS_TXPWR_MAX(n)-P])

AND t(n) > FREElevel_DR(n)AND EN_CAUSE_28 = ENABLEAND EN_FAST_TRAFFIC_HO = ENABLE

Size of window for averaging level: A_PBGT_DR

Same thresholds and window as Cause 20 (Forced Directed Retry)EN_CAUSE_28 is an internal HOP process variable



2.5 Handover DetectionHandover Cause 28: Fast Traffic HO (4/4)

> CAUSE 28: Fast Traffic Handover process

DHCPEND

- Cause number 28- Reference of the call to handover(which corresponds to the firstcandidate MS received)

Start HO

Assignment request queued - Queued request reference- Channel rate of queued request

Fast Traffic HO Request

Yes

EN_CAUSE_28=enable

EN_CAUSE_28=disable

HO alarm:cause 28?

NOK

DHCPEND

Requeststill queued?

Resource AllocationManagement

HandoverPreparation

T_FILTERis started

HandoverManagement

OK

Check first2 conditions of cause 28

- Queued request reference- Reference of MS can perform HO

Fast Traffic HO Acknowledge

Yes

No

NO



> CAUSE 15: High interference on the uplink • Intracell HO

AV_RXQUAL_UL_HO > THR_RXQUAL_CAUSE_15 +OFFSET_RXQUAL_FH

AND AV_RXLEV_UL_HO > RXLEV_UL_IHAND EN_CAUSE_15 = ENABLEAND [ no previous intracell handover for this connection

failed OR EN_INTRACELL_REPEATED = ENABLE ]


2.5 Handover DetectionHandover Cause 15: UL Interference



> CAUSE 16: High interference on the downlink

• Intracell HOAV_RXQUAL_DL_HO > THR_RXQUAL_CAUSE_16 + OFFSET_RXQUAL_FH

AND AV_RXLEV_DL_HO > RXLEV_DL_IHAND EN_CAUSE_16 = ENABLEAND [ no previous intracell handover for this connection failed

OR EN_INTRACELL_REPEATED = ENABLE ]• Size of window for averaging quality: A_QUAL_HO• Size of window for averaging level: A_LEV_HO

2.5 Handover DetectionHandover Cause 15: DL Interference



2.5 Handover DetectionNew parameters for causes 15 & 16

> CAUSE 15 and CAUSE 16:• THR_RXQUAL_CAUSE_15 (or 16) and EN_CAUSE_15 (or 16)

are specific to HOP• THR_RXQUAL_CAUSE_15 (or 16) =

– L_RXQUAL_XX_H for a non AMR call (same threshold as CAUSE 2 or CAUSE 4)

– L_RXQUAL_XX_H_AMR for an AMR call• EN_ CAUSE _15 (or 16) =

– EN_INTRA_XX for a non AMR call– EN_INTRA_XX_AMR for an AMR call



2.5 Handover DetectionAdaptive Multi-rate codec (AMR)> Principles:

• Two consecutive encodings: speech coding and channel coding• With current codecs, the share of each coding is FIXED (not

optimized)

Speech protection"against degradation"

22.8 Kbit/s (FR TS)

Speech protection"against degradation"

11.4 Kbit/s (HR TS)

Channel coding

Channel coding

FIXEDFIXEDFIXED

Radio

Radio

Speech codingSpeech information "useful part"

13 Kbit/sou 12.2 Kbit/s

(FR)(EFR)

Speech information "useful part"

5.6 Kbit/s (HR)

Speech coding

Voice

Voice



2.5 Handover DetectionAMR: codec and channel adaptation

• AMR uses a variable balance between speech coding and channel coding (CODEC Mode Adaptation)

• Choice between FR and HR Codecs: Channel Mode Adaptation

Variable channelcoding rate

22.8 Kbit/s (FR TS)

Variable channelcoding rate

Channel coding

Channel coding

Radio

Speech codingVariable speech coding rate

Variable speech coding rate

Speech coding

Voice

Voice

FLEXIBLEFLEXIBLEFLEXIBLE4.75 Kbit/s5.15 Kbit/s5.9 Kbit/s

6.7 Kbit/s7.4 Kbit/s7.95 Kbit/s

10.2 Kbit/s12.2 Kbit/s




11.4 Kbit/s (HR TS)(AMR HR 7.95 not supported)

Radio



• Based on adaptive trade-off between the share of throughput given to speech coding and the one given to channel coding (speech protection)

• Depends on radio conditions estimated in real-time

2.5 Handover DetectionAMR codec adaptation objective

Mediumradio conditions

Badradio conditions

Goodradio conditions

Speech coding = speech information

Channel coding = speech protection



2.5 Handover DetectionAMR: codec mode adaptation (1/3)

> Codec mode adaptation• Only a subset out of these codecs can be used• This subset may include from 1 to 4 codecs• The same codec subset is used for both the Uplink and the

Downlink• Uplink codec mode adaptation:

– For each SACCH frame, the BTS compares C/I value to the threshold corresponding to the current codec (belonging to the codec subset defined by the operator)

• Downlink codec mode adaptation:– Same process as uplink adaptation– Nevertheless, the BTS remains the master

• Unrelated processes ⇒ uplink and downlink codecs may be different at a given time



2.5 Handover DetectionAMR codec mode adaptation (2/3)

> The Codec mode can be modified on one frame out of two (CMI / CMC-CMR).

> Decision based on thresholds (OMC-R settable), for the uplink and the downlink

AMR_FR_THR_3 + AMR_FR_HYST

C/I norm

AMR_FR_THY_3


AMR_FR_THR_2

Low

High


AMR_FR_THY_3

CODEC_MODE_4(less robust)

CODEC_MODE_3

CODEC_MODE_2

CODEC_MODE_1(most robust)



2.5 Handover DetectionAMR: codec mode adaptation (3/3)

Codec Mode Request(new codec mode)

Codec Mode Indication(new codec mode)

Codec Mode Request(new codec mode)

MS BTS TC


C/I evaluation &thresholds comparison


Codec Mode Command(new codec mode)

MS BTS TC


C/I evaluation &thresholds comparison

> Codec mode adaptation• Uplink

adaptation

• Downlink adaptation



2.5 Handover DetectionAMR: codec and channel mode adaptation

> Codec mode adaptation is dynamically performed through a set of pre-defined “codec modes”:

– In FR mode:

– In HR mode:

> Choice between HR and FR (Channel mode adaptation) is done atcall setup and during call through HO causes 26 & 27


Channel codingSpeech coding


To endof chain

Fromacoustic part

22.8 Kbit/s (FR TS)

12.2 Kbit/s10.2 Kbit/s7.95 Kbit/s7.4 Kbit/s





Channel codingSpeech coding


Fromacoustic part

To endof chain

11.4 Kbit/s (HR TS)7.4 Kbit/s6.7 Kbit/s5.9 Kbit/s


7.4 Kbit/s6.7 Kbit/s5.9 Kbit/s




2.5 Handover DetectionAMR gain> AMR: always gives end user the best satisfaction

• Comparison between different codecs in terms of capacity and quality:

Speech quality requirement

AMR-FR + AMR-HR

AMR-HR

AMR-FR

HR

EFR

FR

Capacity requirement



> FR / HR discrimination• Cell load AV_LOAD() computed from

– load samples = NB_BUSY_TS / NB_TS * 100– non sliding window (LOAD_EV_PERIOD) averaging

process

2.5 Handover DetectionAMR: TCH allocation

AV_LOAD

Time

THR_FR_LOAD_U_SV1 = 80%

THR_FR_LOAD_U_SV3 = 60%

THR_FR_LOAD_L_SV1 = 50%

THR_FR_LOAD_L_SV3 = 40%

100%

FR for any MS

HR for AMR MSFR for other MS

HR for any MS

HR for AMR MSFR for other MS

FR for any MS

THR_FR_LOAD_U_SV1=

THR_FR_LOAD_U_SV3=

THR_FR_LOAD_L_SV1=

THR_FR_LOAD_L_SV3=



2.5 Handover DetectionCause 26: AMR HR to FR HO (1/4)

> CAUSE 26: AMR channel adaptation HO (HR to FR)

• Cause 26 is triggered if :– Current channel rate is HR– Current channel is dual rate and changes are allowed– AMR_FR speech codec is allowed:

EN_AMR_FR = ENABLE



2.5 Handover DetectionCause 26: AMR HR to FR HO (2/4)> CAUSE 26: AMR channel adaptation HO (HR to FR) equation> [ a previous intracell HO cause 15 or 16 has been triggered for this call

in the serving cellOREN_INTRA_DL_AMR = DISABLE and EN_INTRA_UL_AMR = DISABLE]

> ANDAV_RXQUAL_UL_CA_HR_FR > THR_RXQUAL_CA + OFFSET_CA+ OFFSET_RXQUAL_FH and AV_RXLEV_UL_HO > RXLEV_UL_IHORAV_RXQUAL_DL_CA_HR_FR > THR_RXQUAL_CA + OFFSET_CA+ OFFSET_RXQUAL_FH and AV_RXLEV_DL_HO > RXLEV_DL_IH

> AND EN_AMR_CA = ENABLE

> Size of window for averaging quality: A_QUAL_CA_HR_FR



2.5 Handover DetectionCause 26: AMR HR to FR HO (3/4)> CAUSE 26: AMR channel adaptation HO (HR to FR)

• THR_RXQUAL_CA and OFFSET_CA are set as follows :if LOAD_SV3(0) = false then

THR_RXQUAL_CA = THR_RXQUAL_CA_NORMALOFFSET_CA = OFFSET_CA_NORMAL

if LOAD_SV3(0) = true thenTHR_RXQUAL_CA = THR_RXQUAL_CA_HIGHOFFSET_CA = OFFSET_CA_HIGH



2.5 Handover DetectionCause 26: AMR HR to FR HO (4/4)> CAUSE 26: AMR channel adaptation HO (HR to FR)

• Calculation of LOAD_SV3(0):If previous value of LOAD_SV3 = false then

If AV_LOAD > THR_FR_LOAD_U_SV3 thenLOAD_SV3 = true

Else LOAD_SV3 = false

Else (if previous value of LOAD_SV3 = true then)If AV_LOAD <= THR_FR_LOAD_L_SV3 then

LOAD_SV3 = falseElse LOAD_SV3 = true

Annex 3



2.5 Handover DetectionCause 27: AMR FR to HR HO (1/2)

> CAUSE 27: AMR channel adaptation HO (FR to HR)

> Cause 27 is triggered if :

– Current channel rate is FR– Current channel is dual rate and changes are allowed– AMR_HR speech codec is allowed:

EN_AMR_HR = ENABLE



2.5 Handover DetectionCause 27: AMR FR to HR HO (2/2)> CAUSE 27: AMR channel adaptation HO (FR to HR) equation> AV_RXQUAL_UL_CA_FR_HR <= THR_RXQUAL_CA

+ OFFSET_RXQUAL_FH> AND

AV_RXQUAL_DL_CA_FR_HR <= THR_RXQUAL_CA+ OFFSET_RXQUAL_FH

> AND EN_AMR_CA = ENABLE

> Size of window for averaging quality: A_QUAL_CA_FR_HR



2.5 Handover DetectionCause 26 & 27 interworking> Cause 26 & 27 interaction

THR_RXQUAL_CA_NORMAL

Quality

THR_RXQUAL_CA_NORMAL +OFFSET_CA_NORMAL

THR_RXQUAL_CA_HIGH

THR_RXQUAL_CA_HIGH +OFFSET_CA_HIGH

Bad quality: 7

Bad quality: 7

Load = False Load = True

Half Rate

Full Rate

Half Rate

Full Rate

HO cause 26

HO cause 27

HO cause 26

HO cause 27



2.5 Handover DetectionIntroduction to TFO (1/2)> Tandem Free Operation (TFO) solution

TC TC

Codec GSM (A)(8 or 16 Kbit/s)

MS A MS B

Codec GSM (B)(8 or 16 Kbit/s)

A/µ law(64 Kbit/s)

Double transcoding without TFO

TC TC

Codec GSM (A)(8 or 16 Kbit/s)

MS A MS B

No transcoding withTFO



2.5 Handover DetectionIntroduction to TFO (2/2)> Applicability: Only MS to MS speech calls> TFO is based on information exchanged between transcoders

TRAU

MS MSBTS

64 Kbit/s Speech Sample carrying:

- TFO frames on the LSB containing: - compressed speech samples - control bits - TFO messages

- original PCM speech samples on the MSB

TRAU

BSC

IPE

MSC

IPE

MSC

BTS

BSC



2.5 Handover DetectionTFO principles> In the case of first allocation (normal assignment at call setup, inter-

BSS handover, intra-BSS handover where no TFO was previously on-going):

Exchange of Codec capabilities

New call setup

Match

Found

Yes No

Look for common codec

NoYes

Normal operationTFO mode ON

Intracell HO



2.5 Handover DetectionCause 29: TFO HO> CAUSE 29: TFO HO

• Intracell HO used in case of codec mismatch between two MSscalling, in order to match their speech codec

• No radio measurements needed No priority and may be triggered at any time

• Conditions:HO_INTRACELL_ALLOWED = ENABLE

ANDEN_TFO_MATCH = ENABLE



2.5 Handover DetectionCause 29: TFO parameters (1/5)

> EN_TFO– enables/disables the feature, per cell

> EN_TFO_MATCH– enables/disables resolution of codec mismatch, per cell

> EN_TFO_OPT– enables/disables codec optimization, per cell

> FORCE_TFO_VS_AMR– enables/disables the basic functions of TFO for GSM EFR, FR

and HR codec types when the current codec is AMR FR or AMR HR

> FORCE_TFO_HR_WHEN_LOADED– controls the establishment of TFO in HR when the cell is

loaded> KEEP_CODEC_HO

– indicates if the BSC tries to keep the same codec in case of internal intercell HO



2.5 Handover DetectionCause 29: TFO parameters (2/5)> EN_TFO_OPT: enables/disables codec optimization, per cell

• Allows new TFO negotiation on an on-going MTM call to find a better common codec

– For example, HR is used at both sides, but FR is possible too

– HO cause 29 will be triggered on both sides towards best codec



2.5 Handover DetectionCause 29: TFO parameters (3/5)> FORCE_TFO_VS_AMR:

• TFO AMR not specified– Call setup in AMR is not followed by TFO negotiation– FORCE_TFO_VS_AMR enables HO cause 29 after AMR

call establishment towards best TFO codec

ERF + TFOThe MS A can only use HR/EFR/FR

The MS B can use HR/EFR/FR

Cell cap:A MR/HR/EFR/F R Cell cap:HR/EFR/FR

The MS A using AMR, could use HR/EFR/FR


MS A MS B

TFO not possible

Enable (Alcatel patent)

FORCE_TFO_VS_AMR

Disabled(ETSI implementation)



2.5 Handover DetectionCause 29: TFO parameters (4/5)> FORCE_TFO_HR_WHEN_LOADED:

• Gives control on load regulation precedence vs. TFO– 3 values: TFO_HR_NOT_FORCED, TFO_HR_ONLY,

TFO_HR_PREFERRED enable different behaviours in case of loaded cell

HR + TFOThe MS A can only use HR


Loaded cellMS/cell cap:

Unloaded cellMS/cell cap:

The MS A can use HR/EFR/FR


MS A MS B

EFR + TFO

Enable (Alcatel patent)

FORCE_TFO_HR_WHEN_LOADED

Disabled(ETSI implementation)

H/EFR/FR HR/EFR/FR



2.5 Handover DetectionCause 29: TFO parameters (5/5)

> KEEP_CODEC_HO• keeps the same codec type in the new cell in case of internal

intercell HO in order to avoid resolving a new mismatch codec situation

• Avoids double speech quality transition:TFO --> non-TFO --> TFO

• 3 possible behaviors:– TFO_CALLS_ONLY: codec is preferably kept in case of

internal intercell HO for TFO calls only– ALL_CALLS: codec is preferably kept in case of internal

intercell HO for all calls (whatever the TFO state)– FREE: the choice of the codec type is free and depends on

the situation in the target cell



2.5 Handover DetectionCause 30: Move from PS to CS zone

> If EN_RETURN_CS_ZONE_HO = enable> AND a CS call is inside both

• The Non pre-emptable zone and• The MAX_SPDCH_LIMIT_ZONE then

> An intra cell HO cause 30 is triggered

TRX3 TRX1

BCCH SDCCH

PS PS PS PSCS CS CS

Non pre-emptable zone

MAX_SPDCH_HIGH_LOAD zone

MAX_SPDCH_LIMIT zone

PS traffic zone

HO cause 30

PS PS

B9



2.5 Handover DetectionHandover causes priorities

Emergency Handover

Uplink Quality Cause 2

Downlink Quality Cause 4

Uplink Level Cause 3

Downlink Level Cause 5

Distance Cause 6

Too Low Level UL Inner Cause 10

Too Low Level DL Inner Cause 11

HR to FR Channel Adaptation Cause 26 intracell

Uplink Interference Cause 15 intracell

Downlink Interference Cause 16 intracell

Better Condition Handover

Capture Handover Cause 24

Power Budget Cause 12

Traffic Cause 23

Outer UL/DL Level Cause 13

FR to HR Channel Adaptation Cause 27 intracell

Forced Directed Retry Cause 20

Fast Traffic HO Cause 28

HANDOVER PRIORITIES

TFO

Move from PS to CS Zone

29

30



> Emergency causes1- What is the HO cause 2? 2- Which is the flag to activate the HO

cause 2?

2.5 Handover DetectionTraining exercises (1/16)




> Emergency causesComplete the diagram below and fill in the chart with:

L_RXQUAL_UL_H = 3RXLEV_UL_IH = -70 dBmP=MS_TXPWR_MAX=33dBm


Quality

Level

Nb of case

AV_RXQUAL_UL_HO

AV_RXLEV_UL_HO

Current MS power

HO cause 2: YES/NO?

1 2 3 4 5 6

4 1 3 4 4 4

-81 -79 -75 -70 -69 -72

33 33 33 33 33 29(0.8 w)



2.5 Handover DetectionTraining exercises (3/16)> Better condition causes (simple case)

• There are only 2W cells and 2W MS• EN_TRAFFIC_HO(0,n) =Disable• No Ping-Pong margin• HO_MARGIN(0,n) =5 dB• NO DL PC,

RXLEV_LIMIT_PBGT_LIMIT=-47dBm,The serving is not a concentric cell.

> Fill up the chart:

Serving cell N cell

Nb of case

AV_RXLEV_NCELL(n)

AV_RXLEV_PBGT_HO

PBGT(n)

HO cause 12: YES/NO?

1 2 3 4 5 6

-70 -70 -80 -70 -70 -75

-80 -70 -75 -75 -79 -96



2.5 Handover DetectionTraining exercises (4/16)> Better condition causes (ping-pong case)

• EN_TRAFFIC_HO(0,n) =Disable• Ping-Pong margin

PING_PONG_HCP=15dbT_HCP =15s

• HO_MARGIN(0,n) =5 dBA_PBGT_HO = 8 SACCHA n to 0 HO has just been triggered, what happens after 4s?

N cellServing cell?

Nb of caseAV_RXLEV_NCELL(n)AV_RXLEV_PBGT_HO

PBGT(n) «a» onlyHO cause 12: YES/NO? PBGT>HO margin

PING_PONG_HCP=15 -> PBGT(n)HO cause 12:YES/NO?

1 2 3 4 5 6-70 -70 -80 -70 -70 -75-80 -70 -75 -75 -79 -9610 0 -5 5 9 21

YES NO NO NO YES YES



2.5 Handover DetectionTraining exercise (5/16)> Training exercise: Handover Detection

• Better condition causes (traffic case)• EN_TRAFFIC_HO(0,n) =Enable• No Ping-Pong margin• HO_MARGIN(0,n) =5 dB• DELTA_DEC_HO_margin =5dB• DELTA_INC_HO_margin =5dB N cellServing cell

HO



> Better condition causes (traffic case)

Fill up the chart:


N cellServing cell

HO ?

Nb of caseAV_RXLEV_NCELL(n)AV_RXLEV_PBGT_HO

Traffic distribution

PBGT(n)DELTA_HO_MARGIN (0, n)

Cause 12 HO: YES/NO?Cause 23 HO: YES/NO?

1 2 3 4-71 dBm -71 dBm -76 dBm -71 dBm

-780 dBm -80 dBm -80 dBm -80 dBm0: traffic lowN: traffic high

0: traffic highN: traffic low

0: traffic highN: traffic low

0: traffic lowN: traffic high



2.5 Handover DetectionTraining exercises (7/16)> Channel adaptation (cause 26 and cause 27)1- Why is it recommended to have A_QUAL_CA_FR_HR ≥

A_QUAL_CA_HR_FR ?2- An operator may be willing to:

- Under normal load, use only HR calls for quality 0- Under high load, use HR calls for qualities 0 to 3, with an

hysteresis of 1Find the thresholds and offsets for normal and high load:THR_RXQUAL_CA_NORMAL = ? OFFSET_CA_NORMAL = ?THR_RXQUAL_CA_HIGH = ? OFFSET_CA_HIGH = ?



2.5 Handover DetectionTraining exercises (8/16)> Channel adaptation (cause 26 and cause 27)

• EN_INTRA_XX_AMR = Disable• RXLEV_XX_IH = -110 dBm• OFFSET_RXQUAL_FH = 0• A_QUAL_CA_FR_HR =4 and A_QUAL_CA_HR_FR = 2

> Use the previous thresholds and fill up the chart:

UL_QUAL 0 1 2 3 3 1 1 0 0 1

DL_QUAL 0 0 1 1 1 0 0 2 4 3

LOAD_SV3 False False False False True True True True True True

AV_RXQUAL_UL_CA_HR_FR

AV_RXQUAL_DL_CA_HR_FR

AV_RXQUAL_UL_CA_FR_HR

AV_RXQUAL_DL_CA_FR_HR

CHANNEL TYPE FR FR FR



2.5 Handover DetectionTraining exercises (9/16)> Capture HO (Cause 24 )

• There are only 2W cells and 2W MS• L_RXLEV_CPT_HO(0,n) = -85dBm• EN_GENERAL_CAPTURE_HO = ENABLE

>> Fill up the chart: N cellServing cell

HO ?

Nb of case 1 2 3 4 5 6

AV_RXLEV_NCELL(n) - 70 - 70 - 80 - 70 - 70 - 85

CAPTURE_TRAFFIC_CONDITION NOT_LOW HIGH ANY_LOAD HIGH HIGH HIGH

TRAFFIC_LOAD(0) HIGH LOW INDEFINITE HIGH LOW HIGH

TRAFFIC_LOAD(n) HIGH LOW INDEFINITE LOW LOW LOW

HO cause 24: YES/NO?



2.5 Handover DetectionTraining exercises (10/16)> Fast Traffic HO (cause 28)> Find the appropriate candidate MS for this queued request:

• Channel rate required: HR• L_RXLEV_NCELL_DR(n) = -85 dBm (whatever n)• FREElevel_DR(n) = 1 (whatever n)• Channel rate: MS1 FR on Full rate TRX, MS2 HR, MS3 FR

on Dual rate TRX• t(n) for neighbor cells: t(1)=1, t(2)=2, t(3)=2• AV_RXLEV_NCELL(n) in dBm:

Neighbors

MS 1

MS 2

MS 3

1 2 3

- 82 dBM

- 79 dBM

- 90 dBM

- 85 dBM

- 86 dBM

- 82 dBM

- 78 dBM

- 92 dBM

- 89 dBM




> TFO HO (cause 29): after call setupFind the 2 speech version types of the following MS to MS call • EN_TFO = enable, EN_TFO_MATCH = enable• FORCE_TFO_HR_WHEN_LOADED = TFO_HR_NOT_FORCED



MS A MS B

TCH = ? TCH = ?

TCH = ? TCH = ?

Aftercall setup

After TFOnegociation

HR/EFR/FR EFR/FR




> TFO HO (cause 29): after call setupFind the 2 speech version types of the following MS to MS call • EN_TFO = enable, EN_TFO_MATCH = enable• FORCE_TFO_HR_WHEN_LOADED = TFO_HR_ONLY



MS A MS B

TCH = ? TCH = ?

TCH = ? TCH = ?

Aftercall setup


HR/EFR/FR EFR/FR




> TFO HO (cause 29): after call setupFind the 2 speech version types of the following MS to MS call • EN_TFO = enable, EN_TFO_MATCH = enable• FORCE_TFO_HR_WHEN_LOADED = TFO_HR_PREFERRED



MS A MS B

TCH = ? TCH = ?

TCH = ? TCH = ?

Aftercall setup


HR/EFR/FR EFR/FR




> TFO HO (cause 29): after call setupFind the 2 speech version types of the following MS to MS call • EN_TFO = enable, EN_TFO_MATCH = enable• FORCE_TFO_HR_WHEN_LOADED = TFO_HR_ONLY



MS A MS B

TCH = ? TCH = ?

TCH = ? TCH = ?

Aftercall setup


HR/EFR/FR HR/EFR/FR




> TFO HO (cause 29): after handoverFind the speech version types of the following MS to MS call

• EN_TFO = enable, EN_TFO_MATCH = enable• FORCE_TFO_HR_WHEN_LOADED = TFO_HR_ONLY

1. KEEP_CODEC_HO = TFO_CALLS_ONLY 2. KEEP_CODEC_HO = FREE

??



MS 1


MS 2

HO

?

MS 2Call setup +

TFO negociationMS 2HO

?TFO? TFO

HR/EFR/FR HR/EFR/FR HR/EFR/FR



??



MS 1


MS 2

HO

?

MS 2Call setup +

TFO negociationMS 2HO

?TFO? TFO

HR/EFR/FR HR/EFR/FR HR/EFR/FR


> TFO HO (cause 29): after handoverFind the speech version types of the following MS to MS call

• EN_TFO = enable, EN_TFO_MATCH = enable• FORCE_TFO_HR_WHEN_LOADED = TFO_HR_ONLY• KEEP_CODEC_HO = TFO_CALLS_ONLY

1. EN_TFO_OPT = disable2. EN_TFO_OPT = enable



2.6 Handover Candidate Cell Evaluation



> Used to rank potential target cells:

• Ranking based on radio characteristics

• Ranking based on operator preferences

• Ranking based on traffic intensity

2.6 Handover Candidate Cell EvaluationPrinciples



2.6 Handover Candidate Cell EvaluationEvaluation process

MeasurementPreprocessing

A_LEV_HOA_QUAL_HOA_PBGT_HOA_RANGE_HO

HO Detection

Cause 2: uplink qualityCause 3: uplink levelCause 4: downlink qualityCause 5: downlink levelCause 6: distanceCause 12: power budget

Performed every SACCHPerformed every SACCH

Pre-ranking

Priority (0, n) = 0Cell 2: cause C2Cell 3: cause C2Cell 4: cause C2

Priority (0, n) = 1Cell 1: cause C2

Priority (0, n) = 2Priority (0, n) = 3

Cell 5: cause C2Cell 6: cause C2Cell 7: cause C2Cell 8: cause C2



Priority (0, n) = 1Priority (0, n) = 2Priority (0, n) = 3

Cell 6: cause C2Cell 8: cause C2


PBGT filteringHO_MARGIN_XX(0,n)

Grade





Order





Cell evaluation process (Order or Grade)

HO Candidate Cells Evaluation

Maxevery SACCH

Preprocessmeasurement

Measurementresult

Raw cell list

Cell 1: cause C2Cell 2: cause C2Cell 3: cause C2Cell 4: cause C2Cell 5: cause C2Cell 6: cause C2Cell 7: cause C2Cell 8: cause C2... max 32 cells



> Pre-ranking in hierarchical or multi-band networks:

2.6 Handover Candidate Cell EvaluationPre-ranking

Priority(0,n) = 0Cell_layer_type = Pref_layerCell_band_type = serving_cell

Priority(0,n) = 1

Priority(0,n) = 5

Cell_band_type = serving_cell

Priority(0,n) = 0Cell_layer_type = Pref_layer

Priority(0,n) = 1

Priority(0,n) = 5

List ofcandidate

cells n



2.6 Handover Candidate Cell EvaluationPre-ranking

> with priority(0,n) settings, the operator can, for each couple of cells:

• tag the target cell with a defined priority (from 0 = max to 5 = min)• this definition has an higher priority than usual order/grade ranking

> especially useful for multi band/hierarchical architectures: • a simple way to force a target cell whatever its RxLev level and

PBGT• nevertheless can be skipped over by filtering processes• low interest for standard networks

RxLev: - 90 dBmPBGT: + 5 dB

Serving cell

Candidate cell 1

Candidate cell 2

RxLev: - 70 dBmPBGT: + 10 dB

Priority

P1

P0



2.6 Handover Candidate Cell EvaluationPBGT Filtering> PBGT filtering:

• optional, flag EN_PBGT_FILTERING• filter out cells from the target list• inhibited for better cell handovers• based on power budget• per couple of cells

• was needed for multiband architecture

• PBGT(n) > HO_MARGIN_XX (0,n) + OFFSET_HO_MARGIN_INNER

– HO_MARGIN_XX (0,n) = HO_MARGIN_QUAL (0,n)for cause 2,4– HO_MARGIN_XX (0,n) = HO_MARGIN_LEV (0,n) for cause 3,5– HO_MARGIN_XX (0,n) = HO_MARGIN_DIST (0,n) for cause 6– OFFSET_HO_MARGIN_INNER is only applied when the MS is in the inner

zone of a concentric or multi band cell– The averaging window is A_PBGT_HO



> ORDER cell evaluation processCell "n" is ranked among other accordingly:

If EN_LOAD_ORDER = ENABLE and cell n is internal to the BSCORDER (n) = PBGT(n) + LINK_FACTOR(0,n) + FREEfactor(n)- FREEfactor(0)- HO_MARGIN_XX(0,n)

• Link_factor (0,n) is an operator parameter to give a bonus/penalty to a cell

ex: avoid external HO, decrease incoming flow of HO to a cell from another

• FREEfactor is TCH traffic based bonus/penalty to rank cellsIf EN_LOAD_ORDER = DISABLE or cell n is external to the BSC

ORDER (n) = PBGT(n) + LINK_FACTOR(0,n) - HO_MARGIN_XX(0,n)

Cell "n" is kept if:• AV_RXLEV_NCELL (n) > RXLEVmin (n)

+ max [0;(MS_TXPWR_MAX(n)-P)] [dBm]

2.6 Handover Candidate Cell EvaluationORDER evaluation



> GRADE cell evaluation processCell "n" is ranked among other accordingly:

If EN_LOAD_ORDER = ENABLE and cell n is internal to the BSCGRADE (n) = PBGT(n) + LINK_FACTOR(0,n) + LOADfactor(n)

• Link_factor (0,n) is an operator parameter to give a bonus/penalty to a cell

• LOADfactor(n) is a weighting factor that takes into account the relative load of traffic channels in a cell

If EN_LOAD_ORDER = DISABLE or cell n is external to the BSC

GRADE (n) = PBGT(n) + LINK_FACTOR(0,n)> Cell "n" is kept if:

• AV_RXLEV_NCELL (n) > RXLEVmin(n)+ max [0;(MS_TXPWR_MAX(n)-P)]

2.6 Handover Candidate Cell EvaluationGRADE Evaluation

Annex 4



2.6 Handover Candidate Cell EvaluationTraining exercise (1/2)> Emergency HO detected

• With the “Candidate evaluation.xls” excel sheet...» Filtering simulation for a list of candidate cells» Ranking simulation for a list ofcandidate cells

Candidate Cell Evaluation

Serving cell Cell 1 Cell 2 Cell 3 Cell 4 Cell 5 Cell 6RxLev_cell1Mk RxLev_DL Cell_Nb1 BSIC_cell1 Cell_Nb2 BSIC_cell2RxLev_cell2 Cell_Nb3 BSIC_cell3RxLev_cell3 Cell_Nb4 BSIC_cell4RxLev_cell4 Cell_Nb5 BSIC_cell5RxLev_cell5 Cell_Nb6 BSIC_cell6RxLev_cell6

-102** 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110-99** 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110-99** 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110-98AssCmd 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110

-110AssCmp 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110-76** 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110-96** 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110-95** 14 3 -91 0 0 -110 0 0 -110 0 0 -110 0 0 -110-93** 14 3 -92 0 0 -110 0 0 -110 0 0 -110 0 0 -110-93** 1 0 -89 14 3 -91 0 0 -110 0 0 -110 0 0 -110-93** 1 0 -90 14 3 -94 0 0 -110 0 0 -110 0 0 -110-93** 1 -0 -88 14 3 -94 3 1 -101 0 0 -110 0 0 -110-94** 8 7 -93 1 0 -93 14 3 -96 3 1 -103 0 0 -110-96** 1 0 -93 8 7 -95 14 3 -99 3 1 -106 0 0 -110-96** -1 0 -91 8 7 -95 14 3 -99 3 1 -104 0 0 -110-98** 1 0 -92 14 3 -98 8 7 -99 3 1 -107 0 0 -110

-101** 8 7 -97 1 0 -97 14 3 -102 3 1 -107 0 0 -110-101HOCMD 8 7 -96 1 0 -99 14 3 -103 3 1 -108 0 0 -110

0 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -1100 0 -110

HO CauseA_PBGT_HOGRADE EVALUATIONPriority(0,n)HO_MARGIN_LEV(0,n)RX_LEV_MIN(n)LINK_FACTOR(0,n)LoadFactor(n)

DL Level6

0 for all neighbor cell0-1000 for all neighbor cell0




2.6 Handover Candidate Cell EvaluationTraining exercise (2/2)> Emergency HO detected

1 Book-keeping list

Book-keeping list(14;3) (1;0) (8;7) (3;1)

2 Averaging measurement

Averaged measurements and PBGT(n)AV_RXLEV_PBGT_HO

AV_RXLEV_PBGT_HO(14;3)(1;0)(8;7)(3;1)

-100-95-96

-106

PBGT(n)-232-8

3 PBGT Filtering

PBGT(n)(1;0)(8;7)

32

PBGT Filtering

4 GRADE evaluation process

GRADE(n)(1;0)(8;7)

32

GRADE evaluation process

5 Target Cell

(1;0)

? ?

?

?

?



2.7 Exercise



2.8 Exercise

> List all the parameters involved in the detection of cause 23

> List all the causes impacted by the parameter DELTA_INC_HO_MARGIN

> List all the causes impacted by the parameter L_RXQUAL_UL_H

> List all the causes impacted by the parameter BS_TXPWR_MAX

> List all the causes impacted by the parameter BS_P_CON_ACK



3 OTHER ALGORITHMS



3 OTHER ALGORITHMSSession presentation

> Objective: to be able to describe LCS, SDCCH Dynamic allocation, TCH resource allocation, MS reselection algorithms and list the associated parameters

> Program:3.1 Dynamic SDCCH allocation3.2 TCH resource allocation algorithm3.3 MS Reselection algorithms3.4 3G to 2G HO filtering algorithm


3 OTHER ALGORITHMS

3.1 Dynamic SDCCH allocation



3.1 Dynamic SDCCH allocationPurpose

> SDCCH/8 time slots can be dynamically allocated on demand on a cell-by-cell basis.

– “Dynamic SDCCH/8 time slots”. – “Static SDCCH time slots”

Min

Max

Static SDCCHtimeslots

AllocatedDynamic SDCCH/8

timeslots

0

TCH Capacity



3.1 Dynamic SDCCH allocationPrinciple (1/2)

> Principles– Too few SDCCH time slots could result in high blocking rate on

SDCCH (Configuration 1)– Too many SDCCH time slots could lead to a lack of TCH

resources (Configuration 2)

SDCCHtime slots

TCH CAPACITY

SDCCHtime slots

TCH CapacityTCH Capacity

Configuration 1 Configuration 2

Low signaling capacity

More TCH capacity

High signaling capacity

Less TCH capacity



3.1 Dynamic SDCCH allocationPrinciple (2/2)> Allocation and de-allocation of Dynamic SDCCH/8 time slots

• An additional dynamic SDCCH/8 timeslot is allocated by the BSC if there is no SDCCH sub-channel free in the cell.

• A dynamic SDCCH/8 timeslot is de-allocated by the BSC after T_DYN_SDCCH_HOLD (10s) delay if all of its SDCCH sub-channels become free

BCC SDC TCH TCH

TCH TCH TCH TCH

TCH TCH TCH TCH

TCH TCH TCH TCH

TCH TCH TCH TCH TCH TCH TCH TCHCell

Allocation ofDynamic SDCCH/8

times slots

BCC SDC

SDD TCH

TCH TCH

BCC SDC

SDD TCH

SDD TCH

BCCSDCSDD

: BCCH: Static SDCCH: Dynamic SDCCH



3.1 Dynamic SDCCH allocationTIMESLOT types

> NEW TIMESLOT TYPES :

– SDCCH Pure SDCCH or “ static SDCCH “

– TCH Pure TCH

– TCH/SDCCH “ dynamic SDCCH”

– TCH/SPDCH

– MPDCH



3.1 Dynamic SDCCH allocationAllocation algorithm

SDCCH Request

SDCCH mapped on "TCU very high load state" removal

Are they any free SDCCH sub-channelamong Static SDCCH timeslots?

Selection of oneSDCCH sub-channel

Yes No

Are they any free SDCCH sub-channelamong Dynamic SDCCH/8 already allocated?

Selection oneSDCCH sub-channel

Yes

Are they any Dynamic SDCCH/8 timeslotsavailable and free in the cell?

No

Allocate one DynamicSDCCH/8 timeslot

Yes No

SDCCH Requestrejected!!!



3.1 Dynamic SDCCH allocationSDCCH sub-channel selection

Pure SDCCH timeslots

TS with Maximum Free SDCCH sub-channels

TS with lowest TCU load

TS on FR TRX

TS with lowest index on TRX with lowest TRX_ID

TCH/SDCCH TS allocated as SDCCH

TCH/SDCCH allocated as TCH

Pure SDCCH timeslots TS with lowest TCU loadPure SDCCH timeslots


Pure SDCCH timeslots

TS with lowest index on TRX with lowest TRX_IDTS with lowest index on TRX with lowest TRX_IDTCH/SDCCH allocated as TCH

TS on FR TRX



TCH/SDCCH allocated as TCH TS with lowest index on TRX with lowest TRX_ID


TS with lowest TCU load

TCH/SDCCH allocated as TCH



3.1 Dynamic SDCCH allocationDe allocation algorithm> CASE 1:> IF all SDCCH sub-channels of a TCH/SDCCH timeslot become back

freeTHEN the T_DYN_SDCCH_HOLD timer (10s, not tunable) is started.

> IF the timeslot is still free of SDCCH sub-channel when the timer expiresTHEN it is de-allocated (it becomes back TCH).

> CASE 2:> IF several TCH/SDCCH timeslots are allocated as SDCCH

AND IF all of them become free of SDCCH sub-channels when the timer runs

> THEN all these timeslots except one are de-allocated (become back TCH) without awaiting the timer expiration.(the last one waiting for the timer expiration)



3.1 Dynamic SDCCH allocationO&M configuration 1/2

> Massive modification by script

• 10 templates • Template

customization• Template launched

through PRC

> Selection of static or dynamic SDCCH

• Timeslot configuration menu

BTS

BTS

BTS

BTS

2

4

7

3

1

10

9

6

12

8

5

11



3.1 Dynamic SDCCH allocationO&M configuration 2/2

> Default configuration for a cell which has only Full rate TRX

Number of TRXin the cell

Number ofStatic SDCCH

Number ofDynamic SDCCH

Total numberof SDCCH

MaximumSDCCH/TRX

ratio

Is BCCH/CCCHcombined with

SDCCH?

1223456789

10111213141516

4488888

16161616161616242424

88

161624242424243232324040404848

1212242432323240404848485656647272

12.0 (note 1)6.0

12.08.08.06.45.35.75.05.34.84.44.74.34.64.84.5

YesYesNoNoNoNoNoNoNoNoNoNoNoNoNoNoNo


3 OTHER ALGORITHMS

3.2 TCH resource allocation algorithm



3.2 TCH resource allocation algorithmRadio Allocation and Management> Radio resource allocation and management (RAM) aims at:

• Managing pools of TCH radio resources by: – defining TCH radio timeslots as a function of the cell radio

configuration from the operator– sorting these TCH TS according to their radio capabilities

(FR or DR, frequency band (G1 or GSM/DCS))• Allocating dedicated TCH radio resources by:

– selecting the TCH pool in which the TCH should be chosen according to:

– the requested channel rate (FR or HR)– the radio capability of the mobile– the TRE DR capability and the TRE band

– selecting the best TCH resource among the available TCH channels of this pool according to several criteria



3.2 TCH resource allocation algorithmRadio Timeslot of a cell : Operator view> On the OMC-R the operator can configure the following Radio TS per

cell:• Main BCCH timeslot (BCC): TS carrying FCCH + SCH + BCCH

+ CCCH• Main combined BCCH timeslot (CBC): TS carrying FCCH + SCH

+ BCCH + CCCH + SDCCH/4 + SACCH/4• Static SDCCH timeslot (SDC): TS carrying SDCCH/8 +

SACCH/8• Dynamic SDCCH/8 timeslot (SDD): TS carrying TCH + SACCH

or SDCCH/8 + SACCH/8• TCH timeslot (TCH): TS carrying TCH + SACCH or used as a PS

timeslot (PDCH)



3.2 TCH resource allocation algorithmRadio Timeslot of a cell : RAM view> In the BSS the RAM software module maps the OMC-R cell radio

configuration to its own types of TS :• Pure BCCH timeslot: BCC TS carrying only common CS

signalling (BCCH+CCCH)• Pure SDCCH timeslot: CBC or SDC TS carrying only dedicated

CS signalling (SDCCH)• Pure TCH timeslot: TCH TS carrying only TCH traffic• TCH/SDCCH timeslot: SDD TS carrying either CS traffic (TCH) or

dedicated CS signalling (SDCCH) • TCH/SPDCH timeslot: TCH TS carrying either CS traffic (TCH) or

PS traffic (SPDCH channels) • MPDCH timeslot: TCH TS carrying common PS signalling

(PBCCH+PCCCH or PCCCH only)



3.2 TCH resource allocation algorithmRadio Timeslot : OMC-R / RAM mapping

> NB_TS_MPCH MPDCH TS are defined on the BCCH TRX :• on the timeslots configured as TCH TS on the OMC-R • having the lowest timeslot index

> TCH/SPDCH TS are defined as being part of an SPDCH group

> Pure TCH timeslots are OMC-R TCH TS neither defined as MPDCH TS nor in an SPDCH group

TCH

Pure BCCH

Pure SDCCH

TCH/SDCCH

TCH/SPDCH

MPDCH

Pure TCH

BCC

CBC

TCHSDC

SDD

TCH

OMC-Rradio TS

RAMradio TS



3.2 TCH resource allocation algorithmDefinition of a TCH/SPDCH TS

> For PS traffic resource allocation, an SPDCH group is defined on a per TRX basis and is made of consecutive timeslots:• mapped on OMC-R TCH TS• located on a PS capable TRX (TRX_PREF_MARK = 0)• not defined as MPDCH TS• having the same radio configuration (MA, MAIO)

> If several SPDCH groups can be defined on a given TRX, the BSS chooses the SPDCH group of timeslots having the highest number of consecutive timeslots.

> A radio timeslot belonging to one of the different SPDCH groups of the cell is identified in RAM as a TCH/SPDCH timeslot.



3.2 TCH resource allocation algorithmExercise 1

> A non hopping cell is configured on the OMC-R

> Find the radio TS configuration in RAM if NB_TS_MPDCH= 2

TRX1

TRX2

TRX3

TRX4

0 1 2 3 4 5 6 7MPDPBCPSDPTCTSDTSP

: MPDCH: Pure BCCH: Pure SDCCH: Pure TCH: TCH/SDCCH: TCH/SPDCH

BCC TCH SDC TCH

SDD TCH SDC TCH

TCH TCH TCH TCH

TCH TCH TCH TCH

TCH TCH TCH TCH TCH TCH TCH TCH


TRX1

TRX2

TRX3

TRX4

TRX_PREF_MARK

0

0

0

1

0 1 2 3 4 5 6 7



3.2 TCH resource allocation algorithmTCH pools

> 3 pools of TCH resources are managed per cell: • G1 pure TCH pool: contains all the free TCH sub-channels (FR or

HR) free on the pure TCH TS of the G1 TRXs• GSM/DCS pure TCH - TCH/SPDCH pool: contains all the free

TCH sub-channels (FR or HR) free on the pure TCH TS and on the TCH/SPDCH TS of the GSM/DCS TRXs

• GSM/DCS TCH/SDCCH pool: contains all the free TCH sub-channels (FR or HR) free on the TCH/SDCCH TS of the GSM/DCS TRXs

> Any pure TCH, TCH/SPDCH, TCH/SDCCH TS can be:• Busy: if it is not free to serve a FR TCH request• Free: if it is free to serve a FR TCH request



3.2 TCH resource allocation algorithmTCH sub-pools

> FR TCH channels can be allocated on both FR and DR TRXs whereas HR TCH channels can only be allocated on DR TRXs

> Each of the three TCH pools is divided in three sub-pools:• FR sub-pool: contains all the free FR TCH sub-channels available

on the FR TRX• DR: sub-pool: contains all the free FR TCH sub-channels available

on the DR TRX• HR sub-pool: contains all the free HR TCH sub-channels whose

mate HR TCH sub-channel is busy(always located on the DR TRX)



3.2 TCH resource allocation algorithmTCH allocation process 1/2

TCH Request

TCH Allocation

- Radio capability of the mobile- Channel type (FR, HR, DR)- Speech version (FR, HR, EFR, AMR FR, AMR HR)- Request type (NA or HO)

- Cell channel type capability- Cell codec type capability- Cell load

TCH selected

TCH free?

Yes

Queuing?

Select a TCH sub-pool

Select a TCH in this sub-pool

TCH rejectedTCH queued

Yes No

No



3.2 TCH resource allocation algorithmTCH allocation process 2/2

TCH Allocation

TCH free?

Queuing?

TCH selected

Select a TCH sub-pool

Select a TCH in this sub-pool

TCH rejectedTCH queued

Yes No

Yes No

ALLOC_ANYWAYT11T11_FORCEDT_QHO

NUM_TCH_EGNCY_HO



3.2 TCH resource allocation algorithmTCH sub-pool selection

> The BSS selects the TCH sub-pools in which a TCH channel can be allocated according to:

• The requested channel rate and the cell load situation– favour HR if cell is loaded

• A priority given to generic resources1. G1 pool (E-GSM mobile only)2. GSM/DCS pure TCH - TCH/SPDCH pool3. GSM/DCS TCH/SDCCH pool

• An optimisation of FR/HR resources– favour FR pool over DR pool for a FR TCH request– favour HR pool over DR pool for an HR TCH request

• The availability of a TCH channel in the sub-pool



3.2 TCH resource allocation algorithmTCH selection> Sub-pool of the GSM/DCS pure TCH - TCH/SPDCH pool

• Optimise CS/PS traffic resources1. Favour TCH allocation on pure TCH TS2. Optimise PS traffic on TCH/SPDCH TS

– TCH allocated on TRX of highest TRX rank» and on TS of highest TS index

– SPDCH allocated on TRX of lowest TRX rank» and on TS of lowest TS index

> 2 modes of TCH selection• On pure TCH or TCH/SDCCH timeslots• On TCH/SPDCH timeslots



3.2 TCH resource allocation algorithmTCH selection on pure TCH or TCH/SDCCH TS> The TCH is chosen from the selected sub-pool according to the

following criteria:

Non hopping cellBiggest Mobile AllocationEN_MA_SELECTION = true

TCH selected

Highest TS index

HR 0 TCH sub-channel

TCH candidates of the selectedTCH sub-pool

Highest TRX_PREF_MARK

FR allocation orHR allocation on busy TS

Best Interference Band

Highest TRX identity



3.2 TCH resource allocation algorithmTCH selection on TCH/SPDCH TS> The TCH is chosen from the selected sub-pool according to the

following criteria:

• TRX rank is determined by the TRX Ranking algorithm described in the “GPRS & EGPRS Radio Algorithms Description” training course

TCH selected

Highest TS index

HR 0 TCH sub-channel FR allocation orHR allocation on busy TS

Highest TRX identity

TCH candidates of the selectedTCH sub-pool



3.2 TCH resource allocation algorithmExercise 2 - 1/3

> A cell is configured on the OMC-R and TRE are mapped by BSS


BCC SDC TCH TCH

SDD TCH TCH TCH

TCH TCH TCH TCH

TCH TCH TCH TCH

SDC TCH TCH TCH TCH TCH TCH TCH


TRX1

TRX2

TRX3

TRX4

TRX_PREF_MARK

0

0

1

0

0 1 2 3 4 5 6 7

TCH TCH TCH TCH TCH TCH TCH TCHTRX51

TRE

G4 MP FR

G4 MP DR

G3 DR

G4 MP FR

G3 DR




> Find the radio TS configuration in RAM if NB_TS_MPDCH= 2

MPD MPDCH

PBC Pure BCCH TS

PSD Pure SDCCH TS

PTC Pure TCH TS

TSD TCH/SDDCH TS

TSP TCH/SPDCH TS

TRX1

TRX2

TRX3

TRX4

TRX_PREF_MARK

0

0

1

0

0 1 2 3 4 5 6 7

TRX51

TRE

G4 MP FR

G4 MP DR

G3 DR

G4 MP FR

G3 DR




> Find which TCH sub-channel is allocated:1. For MS1: E-GSM, DR2. For MS2: GSM/DCS, DR3. For MS3: GSM, FR4. For MS4, MS5, …., MSn: E-GSM, DR

n = ?

Pure TCH TS

TCH/SPDCH TS

TCH/SDDCH TSas TCH TS

FHP

Cell load = true

: FR TCH call: HR TCH call: SPDCH TS

TSD P P P

P P P

P F

F F F F F F

P P P P P P P

TRX1

TRX2

TRX3

TRX4

TRX_Rank

2

3

-

1

0 1 2 3 4 5 6 7

F FTRX5-

TRE

GSM/FR

GSM/DR

GSM/DR

GSM/FR

G1/DR

H

H HHHHHH


3 OTHER ALGORITHMS

3.3 MS Reselection algorithms



> At startup (IMSI Attach), the MS is selecting a cell with• best C1• once “camped on” one cell (in idle mode)…

> …the MS can decide to reselect on another one if:• C1 criteria is too low• the MS cannot decode downlink messages • the current cell is becoming forbidden (e.g. barred)• the MS cannot access the cell• there is a better cell, regarding C2 criteria

3.3 MS Reselection algorithmsSelection and reselection principles



> C1• ensure that, if a call was attempted, it would be done with a

sufficient downlink and uplink received level• based on 2 parameters, broadcast on BCCH

– RXLEV_ACCESS_MIN [dBm]– minimum level to access the cell

– MS_TXPWR_MAX_CCH [dBm]– maximum level for MS emitting

3.3 MS Reselection algorithmsC1 criteria (1/2)



> C1• evaluated every 5 sec (minimum)• C1 = A - MAX(0,B) > 0• A = RxLev - RXLEV_ACCESS_MIN

– assess that the MS received level is sufficient• B = MS_TXPWR_MAX_CCH - P

– P maximum power of MS– assess that the BTS received level will be sufficient– if MS_TXPWR_MAX_CCH < P

• If A > 0 & B < 0 OK, if B > 0, it can be compensated by A– A >> 0 means that the MS is closer to the BTS

3.3 MS Reselection algorithmsC1 criteria (2/2)



> C2• CELL_RESELECT_PARAM_IND= not present THEN C2=C1 else

– C2 = C1 + CELL_RESELECT_OFFSET -TEMPORARY_OFFSET (T) (if PENALTY_TIME ≠ 31)

– if T > PENALTY_TIME, TEMPORARY_OFFSET(T) = 0– used to avoid locating on “transient cell”– CELL_RESELECT_OFFSET used to favor cell among

other (e.g. micro-cell vs. umbrella, once T > PENALTY_TIME)

– Or C2 = C1 - CELL_RESELECT_OFFSET (if PENALTY_TIME = 31)

– CELL_RESELECT_OFFSET used to handicap some cells among others

• One reselection criterion is compared to C2s– C2neighbor > C2current if cells belong to same LA– C2neighbor > C2current+Cell_Reselect_Hysteresis if cells

from a different LA

3.3 MS Reselection algorithmsC2 criteria



3.3 MS Reselection algorithmsTraining Exercise (1/2)

> On this network example

• List the parameters involved in the selection / reselection process

Time allowed: 5 minutes Cell

Sectorized cell

CI=6169GSM900

Concentric cell

(8564, 1964)

(8564, 6169)

(8557, 1823)

Cell

CI=6271GSM900

CI=6270, GSM900

CI=1823GSM900

CI=1964GSM900



3.3 MS Reselection algorithmsTraining Exercise (2/2)

Cell 1

Cell 2

CI=6169GSM900

Cell 3

(8564, 1964)

(8564, 6169)

(8557, 1823)

Cell

CI=6271GSM900

CI=6270, GSM900

CI=1823GSM900

CI=1964GSM900

• Find the selected cell by the MS


3 OTHER ALGORITHMS

3.4 3G to 2G HO filtering algorithm

B9



> From B7, the 3G to 2G Handovers are managed as incoming HO in BSS but :

• What was the weakness ?

• How to improve it ?

• What do we have to compute ?

• What is necessary to implement ?

3.4 3G to 2G HO filtering algorithmPurpose

B9



> In case of 2G cell overloaded we had no way to reject the 3G HO, so 2G cells can be congested because 3G network is under lack of coverage.

> We must have the possibility to reject 3G incoming HOs in case of 2G target cell is loaded.

> We have first to compute periodically the load of our 2G cells.

> Then, to compare it with a specific parameter we have to create in order to decide the need of rejection.

3.4 3G to 2G HO filtering algorithmProblem and solution

B9



> The traffic load computation is the long term one, already used for HO causes 12 and 23.

> The result is compared with THR_CELL_LOAD_3G_REJECT in order to evaluate “3G_HOReject_Load State”

• IF the last N_TRAFFIC_LOAD AV_TRAFFIC_LOAD ≥THR_CELL_LOAD_3G_REJECT

– THEN 3G_HOReject_Load State = HIGH• ELSE IF the last N_TRAFFIC_LOAD AV_TRAFFIC_LOAD <

THR_CELL_LOAD_3G_REJECT– THEN 3G_HOReject_Load State = LOW

3.4 3G to 2G HO filtering algorithmalgorithms and parameters involved (Evaluation) 1/3

B9



> IF the 3G to 2G handover is triggered by cause different from an emergency cause

– THEN IF 3G_HOReject_Load State = High– Then the BSC shall enter the Hand over Failure

Signalling procedure– ElSE IF 3G_HOReject_Load State = Low

– Then the BSC shall accept the incoming handover

> IF the 3G to 2G handover is triggered by emergency cause– Then the BSC shall accept the incoming handover

3.4 3G to 2G HO filtering algorithmalgorithms and parameters involved (Decision) 2/3

B9



> In case of rejection, the BSC shall send an HO Failure message with:• Cause indicating “no Radio resource available” • Cell Load Information:

– Cell Capacity Class– Cell Capacity Class = CELL_CAPACITY_CLASS

– Cell Load– Cell Load = AV_TRAFFIC_LOAD * 100

(With the last computed value of AV_TRAFFIC_LOAD)

> These information will be used by the RNC and its own algorithms in order to evaluate the necessity to retry the HO or not on the same cell.

3.4 3G to 2G HO filtering algorithmalgorithms and parameters involved (Rejection) 3/3

B9



3.4 3G to 2G HO filtering algorithmTraining Exercise

> Which Mobiles are rejected ?

> What is the Cell_Capacity_Class for each case ?

• THR_CELL_LOAD_3G_REJECT = 75 %


MS

1

4

3

2

5

HO Cause

COMFORT

EMERG

COMFORT

EMERG

COMFORT

FREE TCH

3

3

2

0

12

N_TRAFFIC_LOAD

AV_TRAFFIC_LOAD

60

80

75

100

85

REJECTEDCell

CapacityClass

B9


4 ALGORITHMS DYNAMIC BEHAVIOR



4 ALGORITHMS DYNAMIC BEHAVIOR Session presentation

> Objective: to be able to Estimate qualitatively the impact of parameters change

> Program:4.1 Theoretical presentation4.2 Examples and exercises



4.1 Theoretical presentationSession objectives> SESSION OBJECTIVES

• Be able to estimate qualitatively the impact of a parameter change

> JUSTIFICATION• Tuning is not an exact science• The optimizer has to control every parameter change and predict

qualitatively what the consequences will be• Note: Each change of parameter and its justification have to be

registered in a database for operation convenience

> DETAILED PROGRAM• Three Example/Exercises



4.1 Examples and Exercises



4.2 Examples and ExercisesOverview> Example 1: Optimization of handover algorithms

• Sliding averaging window

> Example 2: Optimization of power control algorithms• Sliding averaging window

> Example 3: Traffic load sharing• Parameters qualitative influence



> Search for best tuning of HO parameters to decrease call drop

4.2 Examples and ExercisesExample 1: Optimization of Handover Algorithms (1/4)

Call drop

HO/Call



> Main Objective: make the HO algorithm as efficient as possible• Minimize call drop rate

– trigger HO soon enough– toward the “best” neighbor

• while keeping a good speech quality– avoid HO due to quality: “too late”– avoid having HO/call rate too high




> Method• Collect Abis trace chart• Search for HO level to avoid quality

lower than 4 (or even 3)– sufficient number of “bad

quality” samples– low standard deviation– problem when HO already

activated

< R x Q u a l _ D L > = f ( A V _ R x L e v _ D L )

0

1

2

3

4

5

6

7

N b _ s a m p l e s

0

2 0 0

4 0 0

6 0 0

S t a n d a r d D e v i a t i o n

0

0 .5

1

1 .5

2

< R x Q u a l _ U L > = f ( A V _ R x L e v _ U L )

0

1

2

3

4

5

6

7

N b _ s a m p l e s

02 0 04 0 06 0 08 0 0

1 0 0 0

S t a n d a r d D e v i a t i o n

0

1

2

3

> Then tune according to QoS indicators (OMC-R) by repetitive process• A_PBGT_HO/A_LEV_HO/A_QUAL_HO• L_RXLEV_UL_H, L_RXLEV_DL_H, L_RXLEV_UL_P,

L_RXLEV_DL_P • OK as soon as HO success rate stabilized




> Neighboring relationship cleanup• Remove useless relationships (A interface statistics, PM Type

180)• Remove the common BCCH/BSIC couple• Add new relationships when a new site is created

> Finally, check the main QoS indicators• Call drop rate• HO failure rate• HO/call rate• Radio Link Failure rate

(the strong rate of radio link failure can denounce a lack of vicinity relation between cells)




> According to the Abis results and some parametersalready set, tune qualitatively the sliding averaging windows:

– A_QUAL_HO– A_LEV_HO

4.2 Examples and ExercisesExample 1: training exercise


Level at RxQual=3 - 80 dBm - 96 dBm - 90 dBmL_RXLEV_DL_H

A_QUAL_HOA_LEV_HO

- 85 dBm6?

- 90 dBm6?

- 90 dBm?4



> Optimization of Downlink Power Control– Decrease of downlink interference– Risks of delay of HO (without fast power control)

> Optimization of Uplink Power Control– Decrease of Uplink interference– MS battery saving– Risks of delay of HO (without fast power control)

4.2 Examples and ExercisesExample 2: Power Control Algorithms Optimization (1/2)



> The main tuning problem is the interaction with handover, which can slow down HO decision, and debase call drop rate

• Power control threshold must be within HO ones• Dynamic step size must be activated if possible

4.2 Examples and ExercisesExample 2: Power Control Algorithms Optimization (2/2)



> Explain qualitatively the impacts of some parameter changes

– What happens if:»we increase POW_INC_FACTOR?»we increase MAX_POW_INC?»We increase A_LEV_PC?

4.2 Examples and ExercisesExample 2: Training Exercise




> Used to unload cell with too high traffic, without HW extension

> Trade-off between traffic sharing/radio quality

> Different algorithm

– Fast Traffic Handover: Cause 28

– Traffic Handover: Cause 23 and 12 with DELTA_HO_MARGIN(0,n)

– Static (couple of cells): HO_MARGIN, LINK_FACTOR

– On a local traffic basis: – Load_Factor/Free_Factor – Forced Directed Retry

4.2 Examples and ExercisesExample 3: Traffic Load Sharing (1/12)



4.2 Examples and ExercisesExample 3: Traffic Load Sharing (2/12)> Fast Traffic HO

• Useful in case of sudden traffic peaks as the process response is instantaneous (no averaging window)

• The principle is to force handover towards neighbor cells which have lower traffic when a request is queued in the serving cell.

• Interaction with Forced DR due to the use of same thresholds• Optimization method (repetitive process)

– Tunes L_RXLEV_NCELL_DR(n), FREElevel_DR(n)– Applies new values, checks traffic peaks, QoS indicators




> The Pros and cons of Fast Traffic HO• Efficiency depends on

– Traffic location in the loaded cell– Capacity of neighbor cells

Increase of the number of HO/callIncrease of incoming HOs fail rate (risk of ping-pong effect)

– In case of internal HO: use PING_PONG_HCP with T_HCPor/and enable HO CAUSE 23

Heavy to tune (has to be done for each couple of cells)

Adapted to instantaneous traffic modificationCan be used to send traffic towards a cell external to the serving BSCAdapted to hierarchical network, but also to standard ones



> DELTA_HO_MARGIN (0,n)

> CHANGE DYNAMICALLY TRAFFIC DISTRIBUTION WITH HO:• Traffic HO Cause 23

– Ease outgoing better condition HO on a traffic point of view• Slow down outgoing better cell HO (to be tuned for a given couple

of cells)– When the better cell in radio condition is the worst cell in

traffic terms• Optimization method (repetitive process)

– Tune DELTA_DEC_HO_MARGIN and DELTA_INC_HO_MARGIN

– Apply new values, check traffic, QoS indicators and possibly speech quality





> The Pros and cons of DELTA_HO_MARGIN (0,n) method• Efficiency depends on

– Traffic location in the loaded cell– Cells overlap– Capacity of neighbor cells

Increase the number of HO/callCannot be used to send traffic toward a cell external to the serving BSCThe call has to be first established on a loaded cell, before being “exported”

– It can be rejected

Easy to tune (dynamic process)Adaptability to instantaneous and long term traffic modifications



> HO_MARGIN / LINK_FACTOR

> CHANGE STATICALLY TRAFFIC DISTRIBUTION WITH HO:• Ease outgoing better cell HO (to be tuned for a given couple of

cells)– Decrease HO_MARGIN (can make a cell “candidate”)– Increase LINK_FACTOR (used to rank candidate cells)

• Optimization method (repetitive process)– Look for neighbor cells able to carry extra traffic– Use Abis trace to check if these cells are candidate

– if yes, use LINK_FACTOR to favor them– if not, use HO_MARGIN and LINK_FACTOR

– Apply new values, check traffic, QoS indicators and possibly speech quality




4.2 Examples and ExercisesExample 3: Traffic Load Sharing (7/12)> The Pros and cons of LINK_FACTOR/HO_MARGIN

• Can be efficient (up to 20% increase of capacity) in some cases– Cell overlap– Capacity of neighbor cells

Increase the number of HO/callThe call has to be first established on a loaded cell, before being “exported”

– It can be rejectedHeavy to tune (has to be done for each couple of cells)No adaptability to instantaneous and long term traffic modifications

Can be used to send traffic toward a cell external to the serving BSC



> FREE_FACTOR/LOAD_FACTOR

> Taking into account the current load of cells, send the MS toward the less loaded cell with HO

• Ease outgoing better cell HO, according to– Load_Factor (% of TCH occupancy) of serving and “target”

cells– Free_Factor (number of free TCHs) of serving and target

cells (order only)– cannot make a “candidate” cell, only change ranking

• Tuning method (repetitive)– to be activated locally for each cell with default parameter

setting– look for QoS indicators (esp. traffic intensity and blocking

rate)– tune tables accordingly




4.2 Examples and ExercisesExample 3: Traffic Load Sharing (9/12)> The Pros and cons of load/free factors method

Lower efficiency compared to LINK_FACTOR/HO_MARGINCalls have to be established on a loaded cell before being “exported”Tuning is performed on a cell-per-cell basisCannot be used to send traffic toward an external cell

Adapted to dynamic change of traffic and capacity (for Load_Factor)No increase of HO/call rate



> Forced directed retry method• Mechanisms

– The MS is connected on an SDCCH of cell1– It must switch on TCH– No TCH is free on cell1– There is at least 1 neighbor cell which has

– sufficient DL level seen by the MS– enough free TCHs

– The MS is handed over to TCH towards this cell– if there are several cells, the one with the best PBGT is

selected




> Method: trade-off between traffic and radio quality

• Mainly L_RXLEV_NCELL_DR(n)parameter to tune

– the lower, the better the traffic sharing

– the lower, the higher the interference risks

• QoS indicators and field tests (speech quality) are necessary for tuning


Cell 2: 45Cell 3: 23

Cel

l 1:

2

4



4.2 Examples and ExercisesExample 3: Traffic Load Sharing (12/12)> The Pros and cons of Forced directed retry

Highest efficiency (up to 30%)No increase of HO/call rateCan be used to send traffic toward an external cellAdapted to dynamic change of traffic Adapted to hierarchical networks, but also to standard ones

Tuning is performed on a cell-per-cell basis



> Draw qualitatively the new serving areas on the pseudo map when enabling traffic HO with:

– DELTA_DEC_HO_MARGIN=6dB– DELTA_INC_HO_MARGIN=4dB

4.2 Examples and ExercisesExample 3: training exercise (1/3)


PBGT(0) = 5

05 5PBGT(0) PBGT(n)

PBGT(n) = 5

Traffic_load

Loaded cell 0 Unloaded cell n

EN_TRAFFIC_HO = 0

Cause 12Cause 12



4.2 Examples and ExercisesExample 3: training exercise (2/3)> What happens when EN_FAST_TRAFFIC_HO = ENABLE and

EN_TRAFFIC_HO(0,n) = DISABLE


QueuedAssignment

Request

PBGT(0) = 5

05 5PBGT(0) PBGT(n)

PBGT(n) = 5

Traffic_load


Av_Rxlev_Ncell(n) = -82 dBm Av_Rxlev_Ncell(0) = -74 dBmAv_Rxlev_PBGT_HO = -82 dBm

L_RLEV_NCELL_DR(n) = -85 dBm



4.2 Examples and ExercisesExample 3: training exercise (3/3)> What happens when EN_FAST_TRAFFIC_HO = ENABLE and

EN_TRAFFIC_HO(0,n) = ENABLE

QueuedAssignment

Request

PBGT(0) = 9

09 -1PBGT(0) PBGT(n)

PBGT(n) = -1

Traffic_load


Av_Rxlev_Ncell(n) = -82 dBm Av_Rxlev_Ncell(0) = -74 dBmAv_Rxlev_PBGT_HO = -82 dBm

5 5



5 CASE STUDIES



5 CASE STUDIES Session presentation

> Objective: to be able to propose a set of parameters to solve typical radio problems

> Program:5.1 Theoretical presentation5.2 TUNNEL Case5.3 RADAR Case5.4 TOWER Case5.5 RESURGENCE Case5.6 FOREST Case5.7 HIGHWAY Case5.8 TCH/SDCCH CONGESTION Case5.9 INDOOR CELL CONGESTION Case


5 CASE STUDIES




> SESSION OBJECTIVES

– Be able to propose an appropriate set of parameters

to solve typical field problems

> JUSTIFICATION

– Some typical problems due to particular field

configuration always occur in a GSM network

> DETAILED PROGRAM

– Eight typical case studies

5.1 Theoretical presentationSession objectives


5 CASE STUDIES

5.2 Tunnel Case



5.2 Tunnel Case

> Radiating cable in a tunnel

Question: Risks of such a configurationTune the right parameters for the tunnel cell

Catch quickly ‘car traffic’ Avoid the pedestrian traffic

Indoor BTS

Outdoor BTS

Pedestrianmobile


5 CASE STUDIES

5.3 Radar Case



5.3 Radar Case

> Radar situation• A “radar” cell situated on top of

a hill provides a wide coverage area.

• An industrial zone in the valley is covered by small cells but also by the “radar” cell. The serving areas in the IZ are not clearly defined.

> Objective• Give a parameter set to prevent

the radar cell from catching any traffic in the industrial zone by HO assignment


5 CASE STUDIES

5.4 Tower Case



5.4 Tower Case

> Tower situation• The indoor mobile selects in idle mode the outdoor

cell (same LA)

> Objective• Define a set of parameters

to avoid that effect

Outdoor cell

Indoorantenna

Indoormobile


5 CASE STUDIES

5.5 Resurgence Case



5.5 Resurgence Case

> Resurgence situation• In rural network,

especially in hilly landscape, many resurgences occur from very far cells.

> Objective• Define a set of

parameters to avoid radio link establishment to those cells and TCH traffic on those cells

Cell A

Resurgencefrom cell A

Cell B

25 Km


5 CASE STUDIES

5.6 Forest Case



5.6 Forest Case

> Forest situation: a highway crosses a forest• High call drop rate (radio cause) on the cell and drive

tests: strong level attenuation at the entrance of the forest

> Objective• Define a set of

parameters to avoid radio link failure

-75 dBm

-90 dBm

Forest(ATT = 10 dB every 100 m)

Hig

hway

BTS


5 CASE STUDIES

5.7 Highway Case



5.7 Highway Case

> Highway situation:• A highway is slightly covered

(best coverage on 200m) by an ‘orthogonal’ cell (cell C on the map)

> Objective• Define a set of parameters to

avoid traffic in the ‘orthogonal cell’

Cell A

Cell BCell C


5 CASE STUDIES

5.8 TCH/SDCCH congestion case



5.8 TCH/SDCCH Congestion Case

> SDCCH congestion situation• A railway station is located at the frontier of two LAs. Every

train stopping in this station comes from LA 1 and then return to LA 1 after the stop.

> Objective• Define a set of parameters to avoid

SDCCH congestion on cell B (LA 2)

LA frontier

LA 1

LA 2

Cell A

Cell B


5 CASE STUDIES

5.9 Indoor cell congestion case



5.9 Indoor cell congestion

> An indoor microcell has been introduced within a multi-layer network (macro + micro)

> When the indoor microcell is congested, FDR may not be working as some the MSs can be covered only by this cell

• Define parameter settings to find a good solution in case of indoor cell congestion

City center

Micro-cells

Macro-Cell

Macro-CellMacro-Cell



END SESSION


ANNEXES


ANNEXES

Annex.1 Erlang B law



Annex.1 Erlang B law Erlang definition

> ERLANG: unit used to quantify traffic

• Example: – 1 TCH is observed during 1 hour– one can observe 1 call of 80 sec and 1 call of 100 sec– the observed traffic is T = (80+100)/3600 = 0.05 ERLANG

Erlang definition

T = total observation durationresource usage duration

(Erlang)



> ERLANG <-> CALL MIX

• CALL MIX EXAMPLE– 350 call/hour– 3 LU/call– TCH duration: 85 sec– SDCCH duration: 4.5 sec

• ERLANG COMPUTATION– TCH = (350 * 85)/3600 = 8.26 ERLANG– SDCCH = [ (350 + 350*3) * 4.5 ] / 3600 = 1.75 ERLANG

Annex.1 Erlang B law Call mix definition



Annex.1 Erlang B law Erlang B (1/5)

> ERLANG B LAW• Relationship between

– offered traffic– number of resources– blocking rate

> In a telecom system, call arrival frequency is ruled by the POISSON LAW

1 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 970

1

2

3

45

6

7

8

9

10Call

Second




> Call request arrival rate (and leaving) is not stable• Number of resources = average number of requests * mean

duration • Is sometime not sufficient => probability of blocking

> => Erlang B law• Pblock: blocking probability• N: number of resources• E: offered traffic [Erlang]• Good approximation when

the blocking rate is low (< 5%)

Pblock = ΣN

k=0 Ek

k !

EN

N !

Erlang B law



> There is two different ways to use this law

• Using Abacus

• Using SW (here Excel)– Pblock = f (T, Nc)– Offered = f (Nc, Pblock)– Channels = f (T, Pblock)





> Example:

We have a BTS of 8 TRXs (about 60 channels (Nc))We do not want more than 2% of blocking (Pblock)=> The traffic is not to be greater than 50 Erlangs (T)

• 83% of resources used to reach 2% of blocking




> But be careful, the law is not linear:

• In B4, we use for example a combined BCCH with a micro BTS.4 SDCCHs, Pblock = 2% => T = 1.1 E25% of resources used to reach 2% of blocking

• In B5, if we decide to provide SMSCB (Cell Broadcast information)1 subchannel SDCCH is therefore used.3 SDCCHs, Pblock = 2% => T = 0.6 E25% of resources less => 50% of Traffic less !!



> CELL DIMENSIONING

• Given an Offered traffic, compute the number of TRXs (and SDCCHs) needed to carry it

• Default blocking rate– RTCH: 2%– SDCCH: 0.5%– (TTCH: 0.1%)

Annex.1 Erlang B law Cell dimensioning (1/5)



> CELL DIMENSIONING

• To handle an offered traffic of 12 Erlangs (TCH), compute the number of channels, then the number of TRXs

• Channels (12;2%) = 19

• Example: 3 TRXs , 21 TCHs, 1 BCCH, 2 SDCCH8




> CELL DIMENSIONING, based on field measurement

• One is measuring a traffic of 15 Erlangs, with a blocking rate of 10%

• How to dimension the cell?

• Offered traffic = 15 / (1-10%) = 16.7 Erlangs !!!!• Channels (16.7;2%) -> 25 TCHs -> 4 TRXs needed




> FORECASTING TRAFFIC/CRITICAL TRAFFIC

• Traffic forecasting must be calculated according to offered trafficnot directly on measured traffic

• In order to plan necessary actions soon enough, one must calculate regularly the date when the traffic of a cell will become critical

• Critical traffic: when offered traffic will induce 2% of blocking





> WARNING: in case of too high blocking rate

• First check that there is no outage on the BTS

• Before starting a dimensioning/tuning action



Annex.1 Erlang B law Training exercise

> Training exercise Complete this form in order to get less than 2% of blocking in all

cases.

Back

Erlang TCHoffered traffic

450 call/hourMean TCH call duration: 80 sec

Blocking rate TCH: 0.8%12,743 10.08 Erlang TCH 30% offered traffic

increase13.1 Erlang TCH -> 20 TCH

3 TRX

Call mix infoCell Traffic forecast Proposed configuration

12,675

12,865


Blocking rate TCH: 4%


Blocking rate TCH: 8%

30% offered trafficincrease

30% offered trafficincrease


ANNEXES

Annex.2 Frequency Hopping influence on PCHO process



Annex.2 Frequency Hopping influence on PCHO process(1/4)> Signal decoding process

• In a GSM system, the number of frames that are not erased are sent as an input to the voice decoder

Inside the mobile station

Decoder

Encoder

DeinterleaveError Correction

Frame ErasureDecision

RXQUAL Frame Erasure Rate

Demod. VoiceDecoder

Air



> Quality impact of frequency hopping on the reception chain

• In non-hopping networks, the RXQUAL and voice quality are correlated

• In hopping networks, the voice quality is sooner correlated to the FER. This is due to interferer averaging and due to the non-linear mapping of BER to RXQUAL values.

Annex.2 Frequency Hopping influence on PCHO process(2/4)



> Quality impact of frequency hopping on the reception chain• FER is improved when frequency hopping is activated (cyclic or

random)• RxQual is not impacted whereas the speech quality is better

Annex.2 Frequency Hopping influence on PCHO process(3/4)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

RxQ Average

0.00%

0.50%

1.00%

1.50%

2.00%

2.50%

FER Average

Ref Cyclic RandomRxQ AverageFER Average



> Conclusion

• When frequency hopping is activated• We can accept in Power Control and Handover processes, a

threshold increase:– OFFSET_HOPPING_PC and– OFFSET_HOPPING_HO

Annex.2 Frequency Hopping influence on PCHO processConclusion (4/4)

Back


ANNEXES

Annex.3 Load & Traffic evaluation



Annex.3 Load & Traffic evaluationCell TCH radio resource evaluation usage

Back - Cause 12

Back - Cause 26

FREEfactorLOADfactor

Loadevaluation

Speed discrimination for hierarchical networkFull Rate/Half Rate channel allocation

Power budget HandoverTraffic Handover

Multiband capture HandoverGeneral capture Handover

N_TRAFFIC_LOAD x A_TRAFFIC_LOAD x TCH_INFO_PERIOD

Shortterm

Mediumterm

Longterm

LOAD_EV_PERIOD x TCH_INFO_PERIOD

TCH_INFO_PERIOD

Period Usage



Annex.3 Load & Traffic evaluationLoad evaluation (1/5)

Nb of free TCHsLOADfactorsFREEfactors

Load evaluation

TCH_INFO_PERIOD sec

LOAD_EV_PERIOD

Non-sliding average

> Medium term measurement of the load of a cell• Corresponds to function AV_LOAD(cell)• A new sample of the “Nb free TCH” in the cell is available every

TCH_INFO_PERIOD seconds• AV_LOAD() is a non-sliding window load average from Nb free

TCH samples updated every LOAD_EV_PERIOD x TCH_INFO_PERIOD sec




> AV_LOAD(cell n) calculated from N Nb free TCH samples available during LOAD_EV_PERIOD x TCH_INFO_PERIOD sec

• LOADfactors and FREEfactors also determined from Nb free TCH samples every TCH_INFO_PERIOD seconds (short term evaluation)

• LOADlevels are boundaries of load intervals associating a LOADfactor (db) to a Nb of free TCH samples

• FREElevels are boundaries of Nb of free TCH intervals associating a FREEfactor (db) to a Nb of free TCH samples

AV_LOADdefinition

AV_LOAD = Nsamples1 Σ

Nsamples

i = 1

(1 - Nb total TCH (n)Nb free TCH (n)

) x 100




> LOADfactor determination:

• LOADlevel in %• LOADfactor in dB

LOADfactor

LOADfactor_1

LOADfactor_2

LOADfactor_3

LOADfactor_4

LOADfactor_5

t = (1 - Nb free TCH/Total Nb TCH) x 100

t <= LOADlevel_1

LOADlevel_1 < t <= LOADlevel_2



LOADlevel_4 < t




> FREEfactor determination:

• FREElevel in absolute number of TCH• FREEfactor in dB

FREEfactor

FREEfactor_1

FREEfactor_2

FREEfactor_3

FREEfactor_4

FREEfactor_5

Nb free TCH

t <= FREElevel_1

FREElevel_1 < t <= FREElevel_2



FREElevel_4 < t




> Example: cells with 4 TRXs (28 TCHs)

In cell evaluation of cell n for outgoing HO from cell 0:• In GRADE(n): + LOADfactor(n) = +0 = 0 dB• In ORDER(n): + FREEfactor(n) – FREEfacfor(0) = +7 – (-8) = +15

dB

LOADfactor+10 dB+5 dB0 dB

-10 dB-15 dB

Load = (1 - Nb free TCH/Total Nb TCH) x 100t <= 10%10% < t <= 25%25% < t <= 50%50% < t <= 80%80% < t

FREEfactor-16 dB-8 dB0 dB

+7 dB+10 dB

Nb free TCHt <= 33 < t <= 88 < t <= 1515 < t <= 2121 < t

Cell nCell 0

HO ?Nb free TCHs = 4Load = 85.7%

LOADfactor(0) = -15 dBmFREEfactor(0) = -8 dBm

Nb free TCHs = 20Load = 28.6%

LOADfactor(n) = 0 dBmFREEfactor(n) = +7 dBm



Annex.3 Load & Traffic evaluationTraffic evaluation (1/4)

> Long term measurement of the load of a cell• Corresponds to function Traffic_load(cell)• Traffic_load() value is determined from a number

N_TRAFFIC_LOAD of consecutive non-sliding window load averages AV_TRAFFIC_LOAD calculated from Nb of free TCH samples updated every A_TRAFFIC_LOAD x TCH_INFO_PERIOD sec

Nb of free TCHsLOADfactorsFREEfactors

Traffic evaluation

TCH_INFO_PERIOD sec

A_TRAFFIC_LOAD(N_TRAFFIC_LOAD non-sliding average)

TRAFFIC_EV_PERIOD




• 3 possible values for Traffic_load(): high, low, indefinite• Initialization: Traffic_load() = indefinite• Traffic_load() becomes:

– High if the last N_TRAFFIC_LOAD consecutiveAV_TRAFFIC_LOAD load averages are all greater than HIGH_TRAFFIC_LOAD threshold

– Low if the last N_TRAFFIC_LOAD consecutiveAV_TRAFFIC_LOAD load averages are all lower than LOW_TRAFFIC_LOAD threshold

Traffic loadThresolds comparisonwith N_TRAFFIC_LOAD

averages

AV_TRAFFIC_LOADAveraging onA_TRAFFIC_LOAD

load samples

Load samples

HIGH_TRAFFIC_LOAD

LOW_TRAFFIC_LOAD

IND_TRAFFIC_LOAD



• Traffic_load() becomes indefinite if:– Traffic_load() was high and the last AV_TRAFFIC_LOAD

load average is lower than LOW_TRAFFIC_LOAD (or IND_TRAFFIC_LOAD if not 0%)

– Traffic_load() was low and the last AV_TRAFFIC_LOADload average is greater than HIGH_TRAFFIC_LOAD (or IND_TRAFFIC_LOAD if not 0%)

• Traffic_load(n) is always equal to indefinite if cell n is external to BSC

• HIGH_TRAFFIC_LOAD ≥ IND_TRAFFIC_LOAD ≥LOW_TRAFFIC_LOAD





HIGH_TRAFFIC_LOAD

Variation ofAV_TRAFFIC_LOAD

IND_TRAFFIC_LOAD

LOW_TRAFFIC_LOAD

Traffic_load = high

Traffic_load =indefinite


Traffic_load = low Traffic_load = lowTraffic_load =

indefinite


Traffic_load = high

IND_TRAFFIC_LOAD = 0IND_TRAFFIC_LOAD <> 0

> Example with N_TRAFFIC_LOAD = 3

Back - Cause 12 Back - Cause 26


ANNEXES

Annex.4 Handover Management



> Handover Management made up of: • Cell Filtering Process (according to call history)• Handover Decision (according to the best cell in the list)

> Handover Management followed by: • Handover Protocol

Annex.4 Handover Management Principles



Annex.4 Handover Management Global Handover Process

Handover preparation

Handoverdetection

Handover management

Cellfilteringprocess

Handoverprotocol

Externalor internalchannelchange

Candidate cell

evaluationHandoverdecision

Rawcell list

Orderedtarget

cell list

Filteredtarget

cell list

Executiontarget

cell list



> Three cell lists:

• Ordered target Cell list

– target cells provided by Candidate Cell Evaluation

• REJ_CELL_LIST

– cells internally rejected by the MSC or BSC

• MS_CELL_REJ_LIST

– cells to which the MS failed to hand over

Annex.4 Handover Management Cell Lists usage



> T_FILTER: controls the global handover procedure• started: when a cell list is to be sent by Candidate Cell Evaluation• expiry ⇒ empty target cell list sent to the Handover Management

> T7: controls the clean-up of REJ_CELL_LIST• started: when a target cell list is to be sent to Handover Protocol• expiry ⇒ empty REJ_CELL_LIST

> T_MS_CELL_REJ: clean-up of MS_CELL_REJ_LIST• started: when an MS reports a failure to seize the target channel• expiry ⇒ empty MS_CELL_REJ_LIST

> T_HO_REQ_LOST: to supervise answer of MSC (no HANDOVER REQUIRED REJECT message sent)

• Started: HO REQUIRED sent• Stopped: HO COMMAND received • Expiry ⇒ external channel change procedure is terminated.

Annex.4 Handover Management Timers usage



Annex.4 Handover Management Handover Execution Process

Handover preparation

Cell filtering process

remove cells previously rejectedfrom MSC or BSCremove cells previously rejectedfor MS failure reasonremove cells not suitable due toO&M reason

Filteredtarget

cell list

Cell 4Cell 2Cell 8

Filteredtarget

cell list

Cell 2

InternalHandover

InternalHandover

Handoverprotocol

Handover decision

Relevant handover protocol ischosen according to the type ofGSM procedure ongoing and thefirst target cell of the list

T7 is started

List of cellspreviously rejected

for MS failure

Cell 8MS_CELL_REJ_LIST listcleared atT_MS_CELL_REJ expiry

List of cellspreviously rejectedfrom MSC or BSC

Cell 4REJ_CELL_LIST listcleared at T7 expiry



Annex.4 Handover Management HO execution example

Handover management

Orderedtarget cell list

Cell 1Cell 2Cell 3

Rejected lists

MS emptyBSC/MSC empty


Cell 1Cell 2Cell 3

Update

Cell 1 -> MSrejected list

Handover management


Cell 1Cell 2Cell 3

Rejected lists

MS cell 1BSC/MSC empty


Cell 1Cell 2Cell 3

Handoverprotocol

HO failson cell 2

ROC

Update

T_MS_CELL_REJexpires

MS rejected listempty

Update

Cell 2 -> MSrejected list

Cell 1 -> BSCrejected list

Handover management


Cell 1Cell 2Cell 3

Rejected lists

MS cell 2BSC/MSC cell 1


Cell 1Cell 2Cell 3

Handoverprotocol

HO tocell 3

Handoverprotocol

HO failson cell 1

ROC



> End of Handover procedure = T_FILTER timer expiry

• T_FILTER restarted each time a target cell list is to be sent by

Candidate Cell Evaluation to the Handover Management (same

list than the one previously sent or not)

• The target cell list is sent to the Handover Management if

different from the last target cell list previously sent

• T_FILTER expiry means no handover is needed anymore

Annex.4 Handover Management T_FILTER controls HO procedure (1/2)



Annex.4 Handover Management T_FILTER controls HO procedure (2/2)

Back

Is T_FILTER running?

YesNo

Restart T_FILTER

New candidate cell list from thecandidate cell evaluation function

Start T_FILTER:an HO alarm containing thecandidate cell is sent to the

HO management entity

YesNo

Is the candidate cell listdifferent from the previous one?

Restart T_FILTER:an HO alarm containing thecandidate cell is sent to the

HO management entity

No Handover is on-going A Handover is on-going

A Handover is now on-going

T_FILTER is restartedeach time the alarm is still on


ANNEXES

Annex.5 LCS



Annex.5 LCS Definitions> New end-user services which provide the geographical location of an

MS:– On MS request to know its own location – On network request (especially during Emergency calls)– On external request (LCS Client)

> Several positioning methods:– Cell-ID or Cell-ID + TA (Timing Advance)– Conventional (standalone) GPS– Assisted GPS (with A-GPS server help to compute

location)– MS-based (MB): the MS is able to perform a pre-

computation– MS-assisted (MA): the MS sends info, Network

computes



Annex.5 LCS LCS architecture> LCS function: Architecture MS Request1

Network Request2External Request3

A-GPSGMLCLCSSMLC

: Assisted GPS: Gateway Mobile Location Center: Location Services: Serving Mobile Location Center

BTS

Abis

MFS

BTS

OSP

SMLC

A-GPSserver

GPS receiversreference network

GMLC ExternalLCS client

MSCBSC

HLR

Abis

A Lg Le

Lh

Lb

Emergency call

2 3

SAGI

Where isthe accident?

Where ismy son?

Where am I?

1

SMLC function integrated in MFS:- receives the location request from the GMLC through the MSC/BSC- schedules all the necessary actions to get MS location- computes MS location- provides the result back to the GMLC



Annex.5 LCS LCS Positionning procedure

BTS

MFS

BTS

OSP

SMLC

GMLCMSC

BSC

HLR

Locationrequest

1

Routinginformation

2

Providesubscriber

location3

Paging,authentication,

ciphering,notification

4

Providesubscriber location

5

Individualpositioning

6 Location report7 7Locationresponse

8



Annex.5 LCS LCS protocol (1/2)

BSC SMLC(MFS)

Um Lb

L1-GSL

L2-GSL

BSSLAP

L2-GSL

BSSAP-LE

L1-GSLL1

L2(LAPDm)

RR

Relay

RRLP(04.31)

BSSLAP(08.71)

BSSAP-LE(09.31)

Target MS

L1

RR(04.18)

L2(LAPDm)

RRLP(04.31)

Signaling Protocols between the MS (CS domain) and the SMLC



Annex.5 LCS LCS protocol (2/2)

> Example: Mobile terminated location request success (External request)MS BTS BSC SMLC MSC GMLC HLR

Adequate positioning methodchosen by SMLC with

optional additional scenario

StartsT_Location

StopT_Location

LCS Service Request

Send_Routing_Info request

Send_Routing_Info response

Provide_Subscriber_Location

Authentication + Ciphering

BSSMAP Perform_Location_Request

BSSAP-LE Perform_Location_Request

BSSAP-LE Perform_Location_Response

BSSMAP Perform_Location_Response

Provide_Subscriber_Location Result

LCS Service Response

MSSMAP Clear Command and Release

LCS client

Paging



Annex.5 LCS Positioning methods : CI+TA positioning

> Principles of CI + TA Positioning Method

LCS_LONGITUDE

LCS_LATITUDE

LCS_AZIMUTH(Main Beam Directiongiven by the azimuth)

HALFPWR_BEAM_WIDTH

Serving cell (CI)

TA

3dB pointgiven by the azimuth

and the HPBW

3dB pointgiven by the azimuth

and the HPBW

553 m

MSestimated location



Annex.5 LCS Positioning methods : Conventional GPS

> Conventional GPS location procedure• This optional location procedure is chosen by the SMLC (if

the MS support it) upon reception of a Perform Location Request message from the BSC

PerformLocationRequest

MS BTS BSC SMLC

Measurement Position Request

Measurement Position Response (X,Y)

PerformLocation

Response (X,Y)(X,Y):

computed position

(X,Y)

LocationRequest

LocationResponse



Annex.5 LCS Positioning method : Assisted GPS Positioning 1/3

> Assisted GPS Positioning Method (A-GPS)• Assistance GPS Positioning Method is split into:

– MS Based A-GPS method– MS Assisted A-GPS method

- GPS acquisition assistance- Navigation model (almanac, ephemeris)- Ionospheric model- Time integrity

GPS MS A-GPSserver

GPS receiversreference network

Assistance data on request




> A-GPS location procedure / MS Based A-GPS


MS BTS BSC SMLC

LocationRequest

A-GPSServer

GPS infoRequest

GPS infoResponse


Assistance Data

Assistance Data Acknowledge

Measurement Position Response (X,Y)

PerformLocation

Response (X,Y)

LocationResponse

PositionRequest

PositionResponse

AssistanceData

(X,Y)

(X,Y):computed position

Positioning calculation:latitude, longitude

and altitude




> A-GPS location procedure / MS Assisted A-GPS

(X,Y):computed position

Pseudo-rangemeasurements (M)

PositionResponse


MS BTS BSC SMLC

LocationRequest

A-GPSServer

GPS infoRequest

GPS infoResponse


Assistance Data

Assistance Data Acknowledge

PerformLocation

Response (X,Y)

LocationResponse

PositionRequest

AssistanceData

(X,Y)

Measurement Position Response (M)

GPS LocationRequest (M)

GPS LocationResponse (X,Y)



Annex.5 LCS LCS impact on HO 1/3

> HO preparation• Inhibition of “better cell handovers”• Other HO

MS BTS BSC SMLC MSC GMLC HLR

StartsT_Location

EmergencyHO

detection

LCS Service Request

Send_Routing_Info request

Send_Routing_Info response

Provide_Subscriber_Location

Authentication + Ciphering


BSSAP-LE Perform_Location_Request

LCS client

Paging

BSSLAP - Reset




> HO management• Internal HO

MS BTS BSC SMLC MSC GMLC HLR

HOcomplete



LCS client

BSSLAP - Reset

Intra BSCHO

on going

BSSMAP perform location response (cause = "Intra-BSC Handover Complete)




> HO management• External HO

MS BTS Serving BSC SMLC MSC GMLC HLR

ExternalBSC HO

BSSAP-LE Perform_Location_Abort

LCS client


BSSMAP HO required




Annex.5 LCS BSS Parameters

Timers

T_LocationT_Location_longerT_Loc_AbortT_LCS_delay_tolerantT_LCS_LowDelayT_RRLP_low_delayT_RRLP_delay_tolerant

FLAGS

EN_LCSEN_SAGI

OPTIMIZATION DATA

ARC_SIZE_FACTORMIN_RADIUS_FACTORMAX_RADIUS_FACTOR



Annex.5 LCS Cell Parameters

SITE DATA

LCS_LATITUDELCS_LONGITUDELCS_SIGNIFICANT_GCLCS_AZIMUTHHALF_POWER_BANDWIDTH

EN_CONV_GPSEN_MS_ASSISTED_AGPSEN_MS_BASED_AGPS

FLAGS



Annex.5 LCS Exercise

> Where is implemented the SMLC function?> What are the LCS impacts on cell dimensioning?




Annex.5 LCSPositioning methods : CI+TA positioning

> Ellipsoid arc definition:

• Point (O)= serving BTS site coordinate

• θ= serving cell antenna azimuth - β /2• β =A*width of serving cell sector in [°],

calculated from bisector anglesof co-sited antenna azimuths

• r1= inner radius ofTA ring-(B-0.5)*554 in [m]

• R2=(B+C)*554 in [m]– A: ARC_SIZE_FACTOR– B: MIN_RADIUS_FACTOR– C: MAX_RADIUS_FACTOR

Back

Serving cell (CI)

E

North

S

W β

θ

r1

r2

Point (O)

b9 radio fine tuning

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