part3_advance network optimization_solution finding

NSN Internal DocumentAdvance Network Optimization/JP/NNPO/ 1st to 3rd July 2010 @ VF RoB1 © Nokia Siemens Networks

Advance Network OptimizationSolution FindingsNPO Refresher CourseJuly, 1 st to 3 rd 2010Vodafone MS – RoB

Jignesh [email protected] Siemens NetworksNational NPO, Ahmedabad, India


Performance Optimization - Introduction

Uplink Signaling (access) problems

Indoor coverageproblems

Downlink coverage problemsDownlink interference problems

CS / PS Capacityproblems

Typical performance problems which have to be improved


Performance optimization - basic CS/PS flows

PCH GetSDCCH

Establish

SDCCH

connection

GetTCH

Establish

TCH

connection

Callphase

Releasephase

AGCHRACH

Paging Optimization• Accessibility

SDCCH Optimization• Accessibility• Signaling

TCH Optimization• Retainability• Quality• Traffic / TSLs allocation• Data rates

CS – Basic Call Flow

Ready SendRACH

Establish

immediate

assignment

GetPDCH

Requested

TSLs to

Allocate

TBFSession

ReleasephaseState

PS – MO Uplink TBF


Performance optimization

Performance optimization will include here:

PS• MM and SM Signaling

•GPRS Attach

•PDP Context activatios

• RLC/MAC TSL data rate•TBF Failure

• E2E Data Rate•Throughput

• Multislot usage•Territory downgrades/upgrades•PS Blocking

• Mobility•Cell reselection

CS• Accessibility

• Signaling problems

• Retainability• TCH Dropped calls

• Quality• interference

• Traffic• Traffic handling


Performance optimization – AccessibilitySignaling

If problems with RACH, AGCH, PCH capacity

• Check if combined signaling is existing. If it is existing, it should be removed

• Check if TRXSIG is big enough, default value for TRXSIG is 32k.If lots of SMS traffic + HR is used 64k should be used.

• Check if there are any bad interference problems– Bad interference problem can cause lot of repetitions => more blocking

• Check CCCH related parameters

• Check if location areas are optimized– Sizes– Borders

Here is combined sdcch in TSL0Should be TSL0 = BCCH

TSL1= SDCCH

CS


A if failures on old channel during TCH HO.c1088A if fail oldA if failures during call.c1087A if fail callAbis failures on old channel during TCH HO.c1085Abis fail oldAbis failures during call.c1084Abis fail callChannel activation failures during call.c1081Act fail callTransaction failures due to radio networkc1050cnfg actTransaction failures due to BCSU reset.c1049BCSU resetTransaction failures due to user actions.c1048user actTransaction failures due to BTS problems.c1047BTS failTransaction failures due to Lapd problems.c1046Lapd failTransaction failures due to transcoder failure on old channel during HO.c1030TCH tc fail oldTransaction failures due to transcoder failure.c1029TCH tc fail callTransactions ended due to old channel failure in HO.c1014TCH radio fail oldTransactions ended due to radio failure.c1013TCH radio fail call

DescriptionCounterDrop Reason

A if failures on old channel during TCH HO.c1088A if fail oldA if failures during call.c1087A if fail callAbis failures on old channel during TCH HO.c1085Abis fail oldAbis failures during call.c1084Abis fail callChannel activation failures during call.c1081Act fail callTransaction failures due to radio networkc1050cnfg actTransaction failures due to BCSU reset.c1049BCSU resetTransaction failures due to user actions.c1048user actTransaction failures due to BTS problems.c1047BTS failTransaction failures due to Lapd problems.c1046Lapd failTransaction failures due to transcoder failure on old channel during HO.c1030TCH tc fail oldTransaction failures due to transcoder failure.c1029TCH tc fail callTransactions ended due to old channel failure in HO.c1014TCH radio fail oldTransactions ended due to radio failure.c1013TCH radio fail call

DescriptionCounterDrop Reason

Performance optimization – RetainabilityTCH dropMost Common TCH drop reasons can be seen here

CS


Performance optimization – RetainabilityTCH drop

TCH DROP Distribution

ExcersiseWhat can be typical reason for TCH radio drops?

CS


Performance optimization – Quality RX Quality – Level Distribution

Rx Quality x Rx Level

Coverage Problem:

Bad quality and

Low Rx Level

Interference Problem:

Bad quality and

High Rx Level

Good Quality

High Rv Level

HW Problem:

Bad Quality

for all Rx Levels

NWD report 204 model

HW ProblemAll samples below -100dBmCL10 �� <-100dBm

NOTE! Same level – quality distribution for both UL and DL

CS


Like Normal distribution HW Problem, TRX/combiner etc is brokenQ0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7

CL10 10645 8516 6813 5450 4360 3488 2791 2232 CL10 5323 4258 3406 2725 2180 1744 4563 9765CL15 47043 37634 30108 24086 9865 7543 5643 2345 CL15 11761 9409 7527 6022 9383 1886 65432 7675CL20 56204 44963 35971 28776 6574 10324 345 65 CL20 14051 11241 8993 7194 18271 2581 65438 63562CL30 200863 160690 128552 102842 17654 9876 145 28 CL30 33772 27017 21614 17291 75037 2469 18765 14523CL40 12785 10228 8182 6546 456 112 24 23 CL40 3196 2557 2046 1636 4938 28 3659 2648CL63 4583 1123 583 452 261 76 26 2 CL63 1146 281 146 113 3378 19 100 174

HW problem, Q4 amount of samples is strange Interference problemQ0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7

CL10 5323 4258 3406 2725 2180 1744 1395 1116 CL10 5323 4258 3406 2725 2180 1744 1395 1116CL15 23522 18817 15054 12043 18765 3772 2822 1173 CL15 23522 13234 10588 8470 13234 10588 8470 6776CL20 28102 22482 17985 14388 36542 5162 173 33 CL20 28102 2123 1699 1359 2123 1699 1359 1087CL30 67544 54035 43228 34582 150073 4938 73 14 CL30 67544 3634 2908 2326 3634 2908 2326 1861CL40 6393 5114 4091 3273 9876 56 12 12 CL40 6393 4091 3273 2618 4091 3273 2618 4532CL63 2292 562 292 226 6756 38 13 1 CL63 9987 7543 4323 3454 2275 1187 876 654

HW Problem, TRX/combiner etc is brokenQ0 Q1 Q2 Q3 Q4 Q5 Q6 Q7

CL10 200863 160690 128552 102842 17654 9876 7865 6543CL15 16543 13234 10588 8470 6776 2822 1173 234CL20 2654 2123 1699 1359 1087 173 33 65CL30 4543 3634 2908 2326 1861 73 14 28CL40 5114 4091 3273 2618 2095 12 12 23CL63 24 54 8 87 7 0 0 0

1

2

3

1. Lots of Q4 samples. Distribution is not OK � HW problem. Site reset will help

2. Lots of bad signal level samples. TRX/Combiner is broken. If no HW problem �Site is totally in wrong place, site is like transferring traffic to another cell ( cause level HO). Typically a HW problem

3. Lots of Q6 and Q7 samples. Distribution is not OK, no Q5 samples � HW problems. Site reset or broken TRX

4. Typical normal interference problem., lots of q4…q7 samples in good signal level

Here are some RX quality – level distribution examples

4

CSPerformance optimization – RX Quality - Level


Performance optimization – Interference, UL

q0 q1 q2 q3 q4 q5 q6 q7-100dBm 10645 8516 6813 5450 4360 3488 2791 2232-95dBm 47043 37634 30108 24086 9865 7543 5643 2345-90dBm 56204 44963 35971 28776 16574 5676 845 65-80dBm 200863 160690 128552 102842 17654 3653 145 28-70dBm 1234 987 790 632 505 404 323 259-47dBm 24 19 15 12 10 8 6 5

MS power control can be seen here. If Power is reduced → no bad UL problems. BSC border is increasing good level samples


Bad interference problems. By POC parameter interference can be decreased, how power is adjusted etc. Also optimum MS power feature improves UL interference, no full power is sent after HO.


Bad quality sample due to signal level problems. Diversity should be checked, also possibilities to use LNA to improve UL signal level. Antenna place should be also checked if there are some obstacles near the antenna.

CS


Performance optimization – InterferenceUL examples

UL_q0 UL_q1 UL_q2 UL_q3 UL_q4 UL_q5 UL_q6 UL_q7 DL_q0 DL_q1 DL_q2 DL_q3 DL_q4 DL_q5 DL_q6 DL_q7-100dBm 251992 30668 20552 18417 18156 18286 16983 12478 27862 5537 5529 6069 6109 6107 5389 4119-95dBm 123653 1151 403 692 519 351 221 72 89094 4236 3853 3576 2893 2264 1372 584-90dBm 62938 247 144 288 353 129 62 29 142228 2732 2550 2356 1510 1114 774 404-80dBm 27005 51 65 149 177 82 40 16 222462 1523 1355 1552 716 812 1081 343-70dBm 2831 3 9 28 87 10 6 0 44504 91 123 151 81 101 191 88-47dBm 751 0 4 10 25 1 0 0 5994 49 17 17 12 29 65 10

Huge amount of UL bad samples. Cells is not working properly, it is like transferring traffic, UL quality/ UL level HO’s are triggering immediately. These kind of cells must be investigated.

UL_q0 UL_q1 UL_q2 UL_q3 UL_q4 UL_q5 UL_q6 UL_q7-100dBm 490 137 368 605 1014 1378 1830 2586-95dBm 8410 3768 3225 3023 2767 2304 1561 1859-90dBm 38512 5249 3066 2323 1692 1570 1191 1268-80dBm 219137 4600 2453 2311 1470 1724 1864 1221-70dBm 509591 2504 1812 3050 1271 1465 1649 337-47dBm 244302 582 711 1363 1713 873 671 87


Some UL interference in good signal level. UL power control is not working properly. Ul power control is good indicator, if power is adjusted, there are no big problems in UL direction

There is no UL interference, or just a little. MS is adjusting power properly, there are only little samples in good UL signal level.

CS



Performance optimization – Interference, DL

Bad interference problem → signal level good (<-80dBm) and sometimes no better cell available. If better cell available and quality samples are 4 or worse → HO (reason quality or interference, depends on the parameter) Interference is causing drops.

Really bad interference problem → signal level is really good (<-70dBm) and usually no better cell available → no HO → samples can be seen in the table. Interference is causing drops.

Situation is “network is working properly” If there are quality 4 or worse samples → quality HO. Most of the samples are q4 samples. If lots of q5..q7 samples → interference problem and interference must be analyzed / removed. If quality HOs but no q5..q7 samples → better cell is available → no interference problems. In these signal levels overlapping exists and if handover reason is no PBGT, it will be quality HO. By parameter amount of quality HOs can be adjusted




Bad quality samples due to signal level problems. If PBGT overlapping is not existing → lots of quality HOs + level HOs (margin are lower than in PBGT).Not interference problem, more coverage problem.

Check how much samples vs. HOs → are better cells available or not.

CS


Performance optimization – InterferenceDL, examples

DL_q0 DL_q1 DL_q2 DL_q3 DL_q4 DL_q5 DL_q6 DL_q7-100dBm 12057 2827 3108 3952 4783 6200 7013 8156-95dBm 44818 4811 5041 5866 6587 7223 7259 6781-90dBm 98587 7107 7400 8334 8470 8781 7825 6162-80dBm 225919 7450 7731 8445 7726 7441 5695 3369-70dBm 88708 1014 971 998 751 688 689 367-47dBm 15881 84 109 122 104 167 199 184


There are almost as much samples Q5 and Q7 samples as Q 4 samples → even interference is really bad or there is no better cell available ( no ho’s after bad quality samples). These kind of interference cells should be optimized, otherwise there are lots of drops etc

There are no as much Q5…Q7 samples as Q4 samples →after interference samples Quality HO is done or the interference situation is not so bad, for example sampling is Q0,Q2,Q4,Q2,Q5,Q0,Q2,Q3,Q4,Q2 → quality HO is not triggering


There are bad quality samples only due to signal level problems.

CS


Performance optimization, Interference (internal / external)

•Internal Interference– Interference can be seen from stats or can be measured by scanner.– Neighbor cells (DL) or mobiles (UL) are causing interference.– By frequency / network planning interference can be decreased.

•External Interference– Interference can be seen from stats or can be measured by scanner.– External radio frequencies are causing interference

� Military use

� In the border area, interference is coming from other country.

� Some external wireless system (for example some wireless industry system) is causing interference

� Increased I level can be also due to external interference

CS


Performance optimization – TrafficTraffic handling

How to balance traffic between other cells in same site?•HO parameters

– PBGT– Quality /interference margins

– Level margins

•HO Features– Umbrella

– Traffic reason HO

– DR

•Traffic layers– 1800 (dual band)– CBCCH

Blocking in cellA

Traffic will be pushed to neighbor cells

cellA

cellB

cellC

CS


Performance optimization – TrafficTraffic handling

Some blocking in cellA

Traffic will be pushedTo neighbor cells

cellA

cellB

cellC

How to balance traffic between other sites?• HO parameters

– PBGT– Quality /interference margins– Level margins

• HO Features– Umbrella– Traffic reason HO– DR

CS


Performance optimization – PS

1. As high signal level as possible• It means that even the indoor signal level should be high enough to

have MCS9 for getting the highest data rate on RLC/MAC layer.

2. As low interference as possible • The aim of having high C/I is to avoid throughput reduction based

on interference.

3. Enough capacity• Enough BSS hardware capacity (interface and connectivity) is

needed to provide the required capacity for PSW services in time. Both CSW and PSW traffic management should be harmonized with the layer structure and long term plans.

Before PS Optimization basic GSM optimization should be done


Performance optimization – GPRS Attach

Typical failures outside BSS• User subscription

– non-GPRS users and users from other operators with no roaming agreement

• Protocol error – Mainly caused by MS not responding during attach, some possible

reasons:� Radio contact lost� MS out of coverage

– Collision of signaling message – MS sends Attach Request or Detach Request when the previous Attach Request is still in process

Typical recommendations:• PS Core settings• Further RF optimization• GPRS detach feature

PS


Performance optimization – PDP Context Activation

Typical failures:• PS Core • Subscribers use incorrect APN during PDP Context Activation

Request– Subscribers/MS keep reattempt with the incorrect APN can badly affect

overall PDP Activation Success Rate– APN of other operators often seen, could because of subscribers using

the same MS with different SIM

PS


Performance optimization – TBF Failure

Typical reasons for TBF failures• Radio reasons

– Bad coverage– Interference problems

– Blocking

• Parameter discrepancies– MCA parameters

– POC– GPRS_POC

� IFP, TFP

• SGSN problems– Gb, Gn traces will be needed

PS

TBF

Attempts

Establishment

Failures

No

ResponseFlush CSW

TrafficSuspend

Normally

EndedTBFs

TBF

Attempts

Establishment

Failures

No

ResponseFlush CSW

TrafficSuspend

Normally

EndedTBFs

TBF Failures


Performance optimization – Throughput

• Radio reasons, throughput / timeslot is bad– Bad coverage– Interference problems

⇒Decreased coding scheme => less throughput even many timeslots used

• TSL allocation problems, total throughput is bad– Check territory usage

• Check downgrades due to CSW traffic and PSW rejects• Add more dedicated timeslots for data if possible

– Check TBF sharing• If lots of TBF/ TSL => check that CDED parameter <>0• Too much sharing => territory not big enough. If possible, add more dedicated timeslots

• Transmission problems– EDAP congestion

– Gg congestion

PS


Performance optimization – Multislot Usage

Territory downgrade and upgrade• Territory downgrade due to CSW traffic rise (c1179)

– CS traffic handling

• Territory downgrade due to less PSW traffic(c1181)– Territory optimization, territory is perhaps not big enough

– CS Traffic handling

• Territory upgrade request rejection beyond default territory– Upgrade request beyond Default territory for additional resources

(c1174), which can be rejected because of:1. No (E)GPRS capable resource left (No (E)GPRS enable TRX or the maximum (E)GPRS

capacity reached)2. PCU and EDAP capacity limitation (256 Abis TSL per PCU)3. High CSW load

PS

0 1 2 3 4 5 6 7

Default territory

1174

1181

1180

1179

0 1 2 3 4 5 6 7

Default territory

1174

1181

1180

1179


Performance optimization – PS Blocking

• Hard blocking – no resources available– More TSLs for data must be available

� Check unavailability in the cell

� More dedicated timeslots for data

� Amount of CS traffic must be reduced (traffic handling with features)

– RF optimization => better throughput => less blocking

• Sof blocking – TSL allocation problems– Check parameters

� Territory parameters, CDED, CDEF

� Check also also (E)GPRS parameters� Check also timers

• Too much delays => more blocking

PS


Performance optimization – Cell Reselection

Typical main causes:• Bad overshooting

– Dominance areas are not clear

– Too much cell reselections

• Link balance problems– UL / DL

• Cell reselection parameters are not properly planned– Check C1,C2, NCCR parameters

– Check IFP, TFP parameters

• BSC / PCU area optimization is not properly done– Delays will be increased if areas are not properly planned

PS


Traffic and Capacity Optimization


• Ater, Transcoder (TC), A-interface• BSC level• Site level• TRX level• Timeslot level• Signaling

Traffic and Capacity Optimization

BSC 2G

SGSN

TC

Abis Gb

BSC BSC 2G

SGSN

2G

SGSN

TC

BC SU

BTS

Airinterface

GSM ArchitectureTraffic and Capacity Optimization levels

MSC

Ater

A


Traffic and Capacity Optimization Introduction

• Ater, TC, A– Capacity and pools

• BSC– BSC Type, BSC load, Gb links– BCSU, capacity– EDAP/PCU Type, Load

• Site– Antennas, BTS HW/SW BTS configuration, Dual band, CBCCH, SDCCH

traffic etc

• TRX– Where capacity will be needed

• Timeslot– FR/HR, AMR FR/HR, territory, CMAX, SDCCH traffic

• Signaling– CCCH, TRXSIG, SS7 links


Ater Interface

•All traffic from BSC must be transferred to transcoders. Number of E1’s in Ater / Asubinterface is depending on:

• TCH Traffic from all abis IF’s• CCS7 traffics• O&M links• Utilization rate

•1 PCM timeslot in Ater/Asub interface:

• 64Kbit/s

•1 PCM timeslot in Abis interface :• FR= 16 kbit/s

• HR = 8 kbit/s

=> 4 or 8 PCM timeslots in abis = 1 PCM timeslot in Ater

Abisinterfaces

Traffic and Capacity Optimization Ater, TC, A



• Total number of required Ater Channels.• Number of Ater channels is based on total

Erlangs in BSC and blocking in A-interface• Configuration options for TCSM3i for

standalone installations can be seen below

Required transcoding (TC) capacity is derived from

ET 16 ET 16 (16 E1

PCMs)-1 BSC

(16 E1 PCMs) several BSCs

1 960 760 3 3 82 1920 1520 5 6 163 2880 2280 8 9 244 3840 3040 10 12 325 4800 3800 13 15 406 5760 4560 15 18 487 6720 5320 18 21 568 7680 6080 20 24 649 8640 6840 23 27 7210 9600 7600 25 30 8011 10560 8360 28 33 8812 11520 9120 30 36 96

TCSM3i units (capacity step) ETSI channels ANSI channels TR3E

Note. In some solution Transcoder can be implemented to Media Gateway MGW



A InterfaceNumber of required A- Interface PCMs is derived from total number of required Ater Channels. 4:1 multiplexing

For Example• Total Erlangs in BSC = 3920 Erl• Blocking in A-interface =0.1%

→ ErlangB table(3920,0.1QoS )

→ 4042 Ater Channels

→ Ater Interface PCMs = 4042(ETSI) / 120 = 34→ A interface PCMs(1:4) = 34*4 = 136

ETSI Channels Ater interface PCMs A interface PCMs (4 :1)960 8 32

1920 16 64

2880 24 96

3840 32 128

4800 40 160

5760 48 192

6720 56 224

7680 64 256

8640 72 288

9600 80 320

10560 88 352

11520 96 384

1 : 120 4:1


Traffic and Capacity Optimization BSC• Example of BSC capacity evolution

Mean holding time 120sMobile originated calls (MO) 70%Mobile terminated calls (MT) 30%Handovers per call 1.5Location updated per call 2IMSI detach per call 0.1Paging response 63%SMS (req(subs/1 hour) 1Terminated SMS 80% 80%QoS 2%

Traffic Profile exampleHow Erlangs are calculated?• This depends on used traffic profile• Different traffic profile => different

results

Example, How to calculate BH call attempts= (Total_Erl x 3600s) / mean_holding_time(s)

Static limits BSC2i BSC3i 660 BSC3i 30001 cab 2 cab

# TRX 512 660 1000 2000 3000#BTS 512 660 1000 2000 3000#BCF 248 504 1000 2000 3000#BSCU 6 6 5 10 6#SS7L 16 16 16 16 16#LAPD 992 1236 2240 4480 5760# (logical) PCU 16 24 50 100 30# abis 16k channels 4096 6144 12800 25600 30720#E1/T1 lines 144 256 384 800 800Erlangs 3040 3920 5940 11880 17820

BSC3i 1000/2000


Traffic and Capacity Optimization BSC - Example of Utilization

Actual TRX utilizationActual TRX utilization

Actual TCH UtilizationActual TCH Utilization

BSC Utilization• TRX Usage• TCH Usage

Utilization analysis can be used for long term BSC optimizationCapacity management vs. configuration optimization

If utilization values If utilization values are too high are too high

=> BCS Capacity => BCS Capacity optimization will be optimization will be neededneeded


Traffic and Capacity OptimizationBSC - EDAP / PCU / Gb

• EDAP capacity can be optimized based on KPI values– DL / UL MCS selection limited by EDAP (dap_7a, dap_8c) – DL / UL MCS selection limited by PCU (dap_9, dap_10)– Peak DL EDAP usage (c76004)– Peak UL EDAP usage (c76005)– Territory upgrade rejection due to lack of PCU capacity (blck_32)– Not too much capacity nor too less capacity

• EDAP / PCU performance can be decreased due to Gb link size

– UL/ DL Gb load: frl_7a/ frl_8a– This should be checked always with EDAP / PCU optimization


Traffic and Capacity OptimizationBSC - EDAP / PCU

• EDAP blocking– If EDAP utilization is below 100 => increasing EDAP does not

provide any help => PCU optimization needed– As a rule of thumb the following estimation may be used to

calculate number of E1’s.

Note!Can be used also T1s

E1:32 channelT1:24 channel

Nbr of TRX Amount of E1s12 TRX GSM / GPRS

9 TRX GSM / EGPRS

6 TRX GSM / Heavy EGPRS

18 TRX GSM / GPRS

15 TRX GSM / EGPRS

12 TRX GSM / Heavy EGPRS

24 TRX GSM / GPRS

21 TRX GSM / EGPRS

18 TRX GSM / Heavy EGPRS2 E1

1 E1

1.5 E1


Traffic and Capacity OptimizationBSC - Gb

• Gb utilization– If values near thresholds, it is recommended to increase Gb link size

OR Implement Gb over IP

901024

85896

75768

70640

68512

68384

61256

25128

Restricting Gb link utilisation

[%]

Gb bandwidth [kbps]

Maximum received load % ( DL)


Traffic and Capacity OptimizationSite - Indoor solution

Indoor solutions

4 TRX, 20Erl

2 TRX, 5Erl Indoor Site4TRX, 15Erl

Before

After

Note! Indoor solution is collecting traffic inside (heavy traffic) office

=> Less frequencies is needed outside the building


Traffic and Capacity Optimization Site - Dual Band Network

GSM 900 layer (4TRX:24Erl (Bad blocking),

GSM 900 layer (2TRX:2Erl)

GSM 900 layer (2TRX:7Erl (no blocking)GSM 1800 layer (4TRX:21Erl)

GSM 900 layer (1TRX:1,5Erl

Actions:• 1800 layer was added• From 900 layer traffic to 1800 layer• 3 TRX was removed from 900 layers• Total traffic was increased

Before

After

Note! Dual band layers can be also GSM 900 and WCDMA


Traffic and Capacity OptimizationSite – Traffic layers

Traffic layers

• 900 Macro• 1800 Macro• 900/1800 Micro• 900/1800 Indoor

2G Layers

3G Layers• 2100 Macro• 2100 Micro• 2100 Indoor

Note! Traffic between layers can be handled by parameters


Traffic and Capacity Optimization TRX – capacity where it is needed

Site configuration 2+2+2 in all sites

9Erl

5Erl

5Erl

6Erl

4Erl

5Erl

3Erl

4Erl

8Erl

1Erl

3Erl

4Erl

1Erl

1Erl

2Erl

Bad Blocking area• More capacity is needed

Extra capacity• 2 trx / cell is too much•=> TRX can be transferred to the cells where these are more needed


Traffic and Capacity Optimization Timeslot – AMR FR/HR

Half rate (HR) is recommended to use when:• More capacity will be needed but additional TRXs can not be

added– Interference problems, Frequency reuse – HW limitations

• Temporary needs for additional capacity– Special events– Due to daily traffic profile, additional capacity will be needed just for

short time• Big cruise is passing by, tens of calls during short time



• Channel Mode Adaptation is an HO algorithm that aims at select the correct channel rate (FR or HR).

• The selection of the channel rate depends on 2 main factors: load and quality

loadload GoodGoodQualityQuality

CodecCodec

AMR FRAMR FR AMR HRAMR HR

AMR HRAMR HRAMR FRAMR FRBadBad

QualityQuality

packingpacking

unpackingunpacking


Traffic and Capacity Optimization Timeslot – FR/HR & PS territoryStrategy – which timeslots for data and which for speech?

• BFG –parameter• Whether the BCCH TRX or other TRXs are preferred in GPRS channel allocation .

• FRL –parameter• With this parameter the percentage of full rate TCH resources that must be available for

traffic channel allocation is defined.

• FRU –parameter• With this parameter the percentage of full rate TCH resources that must be available for

traffic channel allocation is defined.

•Note! Territory and dual rate in same TRX(HR just after territory) => not good, should be changed

tsl0 tsl1 tsl2 tsl3 tsl4 tsl5 tsl6 tsl7

TRX1 bcch sdcch

tsl0 tsl1 tsl2 tsl3 tsl4 tsl5 tsl6 tsl7

TRX2

How to allocate CS and PS channels?


Traffic and Capacity Optimization –AMR and PS interworking, CS TCH Allocation Calculat ion

5 CS calls

6 CS calls

downgradedTCHDTCHDTCHDTCHDTCHDTCHDMBCCHC

EGPRS downgraded

xxxxxx

CDEFTCHDTCHDTCHDTCHDTCHDTCHDMBCCHCEGPRS used/default

xxxxx

CTC 0 CTC1 CTC2

Free FR TCH resources 1 1 2

Working FR TCH resources 6 7 7

% of free FR resources 16.7% 14.3% 28.6%

HR Preferred? N Y N

Free FR TCH resources 1 1 1

Working FR TCH resources 7 7 7

% of free FR resources 14.3% 14.3% 14.3%

HR Preferred? Y Y Y

Territory downgrade due to CS traffic

FRL = relative amounts of free FR TCH resources in proportion to working FR TCH resources

FRL = 15% in this example

CS TCH allocation calculation (CTC)• Defines how the GPRS territory is seen when calculating FR resources.

CTC Value0 = Only CSW used RTSLs are used to calculate resources

1 = CSW and PSW used RTSLs are used. PSW used RTSLs are seen as occupied resource when calculating PSW RTSLs

2 = CSW used and PSW used RTSLs are used. PSW used RTSLs are seen as idle resource when calculating resources



Free FR TCHs

Time

Upper limit for free FR TCHs

Lower limit for free FR TCHs

No packing of

FR callsPacking of

FR calls

No packing of

FR calls

Free FR TCHs

Time

Upper limit for free FR TCHs

Lower limit for free FR TCHs

No packing of

FR callsPacking of

FR calls

No packing of

FR calls

HR will be allocated when there are few free FR TCH s available. • The purpose is to avoid congestion / blocking• HR => FR when there are again enough free FR TCHs• Thresholds are set by parameters (FRL, FRU)


Traffic and Capacity Optimization signaling -paging

TRXSIG Comments

16k Can be used if 32k is not possible to use

32k Default value . Must be used if HR is used or high SMS traffic64 k Must be used if HR is used and high SMS traffic

PagingTRXSIG can be dimensioning based on following table: • After implementation paging capacity KPIs and occurrence of

LAPD overload must be checked

Note! If the cell is part of the large location area, high paging load is expected. Thus small signaling links (16kbps) shall be avoided.


Traffic and Capacity Optimization signaling -sdcch

• Capacity of SDCCH in the cell is depending on the amount of TRX’s in the cell

• Capacity of SDCCH in the cell is also depending heavily on Traffic profile, for example amount of SMS’s

• SDCCH blocking KPIs should be monitored & avoided– And reason for blocking, SMS, LU, paging etc should be known.

• Note! Exceptions are cells that cover ports of entry, such as airports, where a large number of subscriber location updates are expected

Erl mErl/subs subs 1 sms/subs/hour 5 sms/subs/hour 10 sms/subs/hour 1 sms/subs/hour 5 sms/subs/hour 10 sms/subs/hour1 2.2 25 88 0.4 0.8 1.3 1 1 12 8.2 25 328 1.6 3.1 4.9 1 2 23 14.9 25 596 3.0 5.6 8.9 1 2 34 21 25 840 4.2 7.9 12.6 2 2 35 27 25 1080 5.4 10.2 16.2 2 3 4

SDCCH Traffic (Erl)Number of TRX in the cell

Number of SDCCH in the cell


Traffic and Capacity Optimization signaling - sdcch

Increased Dynamic SDCCH• SDCCH resources are used for call

establishment, location updates and short messages (SMS)

• Dynamic SDCCH allocation feature configures additional SDCCH resources according to the traffic situation in a cell

• When a BTS needs temporarily larger SDCCH capacity, then idle TCH resources are configured for the SDCCH use

• When the congestion situation is over extra SDCCH resources are configured immediately back to TCH resources

• By using Increased Dynamic SDCCHCapacity, you can use up to 32 SDCCHs per non-BCCH TRX and 24 per BCCH TRX

BCCH SDCCH/8 TCHTCHTCHTCHTCHTCH

BCCH SDCCH/8 TCHTCHTCHTCHTCHSDCCH/8

• In case of SDC C H congestion, one

free traffic channel can be

changed dynamically to SDC C H/8

• When SDC C H/8 is no longer

needed it is changed dynamically

back to TC H


Coverage Optimization


SiteA

Solution finding – coverage optimization

20 km away from site

• Signal level -95dBm?• Are both cases critical ones?• Are both cases coverage problem

cases?

20km

20km

Bad coverage – what does it mean?




DL_q0 DL_q1 DL_q2 DL_q3 DL_q4 DL_q5 DL_q6 DL_q727862 5537 5529 6069 6109 6107 5389 411989094 4236 3853 3576 2893 2264 1372 584142228 2732 2550 2356 1510 1114 774 404222462 1523 1355 1552 716 812 1081 34344504 91 123 151 81 101 191 885994 49 17 17 12 29 65 10

-100dBm-95dBm-90dBm-80dBm-70dBm-47dBm




UL

DL

QUALITY

SIG

NA

L LE

VE

LSignal level – quality distribution

251992 samples• signal level < -100dBm• Quality 0=> UL coverage problem?

12478 samples• signal level < -100dBm• Quality 7=> UL coverage problem?

ExerciseHow we should here optimize coverage?• Any problems?



Signal level <-90…-95dBm is many times level threshold• Typical values for ul/dl level HO (UL, -95dBm, DL, -90dBm)• UL / DL coverage should be always analyzed separately• Here, lots of bad UL signal level samples => UL coverage should be

improved







UL

DL

QUALITY

SIG

NA

L LE

VE

L



Solutions to improve coverage• Antenna changes

� Tilting

� Adding antenna with bigger gain

• New cell / site� Costly

• DL /UL amplifiers� DL, boosters� UL, Mast head amplifier (MHA)

• Diversity� UL

• Reducing losses� Combiner types

� Feeder types

• Better site / antenna place

900MHz900MHz


Solution finding – coverage optimization indoor coverage

•Many networks have insufficient indoor coverage due to high building penetration loss. This includes subways, under ground facilities and tunnels.

•Outdoor coverage is normally ok in urban and city area. Interference is more an issue for outdoor users.

•Micro cell and Indoor cell are good solution to improve indoor coverage and network quality.

– Antenna location is main factor for successful indoor coverage planning

Indoor PanelAntenna

Indoor BTS

Remote Unit

Master Unit

Optical Fiber RF Cable


Solution finding – coverage optimization indoor coverage

Other features can be also used for coverage optimization

• Extended cell• Smart radio concept • Antenna hopping


Examples of wrong parameter set impact on network operation/performance – call setup , qual, bands

1. No calls happening in a cell• Cell Barred

• Non existent (LAC, Cell ID) in MSC

• DMAX = 0

2. Very few calls happening in a cell• RxLevAccesMin

• Wrong MNC, MCC, LAC declaration

3. Very low traffic in a cell• msTxPwrMax = 0, bsTxPwrMax = 30

4. Bad quality in UL after rehoming5. Few traffic in 1800 layer of a dual band 900/1800 network


Example 1a

�

�

Handover

C all Setup

SYS INFO 3 (BCCH)

(CellBarrAccess =

yes)

No calls happening in a cell: • The cell has been barred


Example 1b

MSC does not find (LAC, CI) in its database

No calls happening in a cell: • CI different between MSC and BSC or non existent (LAC, Cell

ID) in MSC


Example 1c

No calls happening in a cell:• MsMaxDistanceInCallSetup (DMAX) = 0

DMAX = 0

RxLevel = -70 dBm

�

Call Setup

Despite the coverageof the cell, no callswill be established!


Example 2a

Very few calls happening in a cell: • RxLevAccesMin

Cell coverage

RxLevAccessMin = -47 dBm

......

-109 dBm1

-47 dBm63Highest range

-48 dBm62

-110 dBm0Lowest range

BSS MML

OSS database

Mapping Be careful when setting parameter through xml or datfile! OSS database unit should be used to specify parameter value!


Example 2b

Very few calls happening in a cell: • Wrong MNC, MCC, LAC declaration in network - MNC: 01 ≠

1 !!! (In OSS correct value)

Note! Be careful when setting parameter through xml or dat file! OSS database unit should be used to specify parameter value!


Example 3

bsTxPwrMax 0 … 30 dB 0 dBbsTxPwrMin 0 … 30 dB 30 dBminMsTxPower 0 … 36 dBm 0 dBmsTxPwrMax 0 … 36 dBm

Parameter Value_______ Defau lt value

BTS Max Power = BTS Power – (bsTxPwrMax = 0 dB)

BTS Min Power = BTS Power – (bsTxPwrMin = 30 dB)

Attenuation Values (dB)

Power Values (dBm)

MS Max Power = (msTxPwrMax = 33 dB)

MS Min Power = (minMsTxPower = 13 dB)

Absolute

∆Delta

Very low traffic in a cell: •msTxPwrMax = 0, bsTxPwrMax = 30


Example 4

Bad quality in UL after rehoming: • DiversityUsed parameter not set to yes anymore

RDIV = Y

Uplink Diversityimproves quality of signal received.

After rehomingRDIV parameter was set to default value (No) and UL quality was affected.


Example 5

Few traffic in 1800 layer of a dual band 900/1800 network:• Idle Mode: C2 parameters not set properly (temporaryOffset,

penaltyTime)• Idle / dedicated mode parameters should be according to

strategy

BCCHBCCH

fast moving mobileslow moving mobile1800: micro-Layer 900: macro-layer


Frequency Optimization


Solution finding – frequency optimization

GSM network is based on good frequency planningBad frequency planning is causing high interference levels• Lots of drop calls• CS/PS quality is bad• Features are not working properly• Maybe new sites are built due to bad interference problems• Lots of customer complaints• Finally less customers

=> Frequency plan should be properly done


Solution finding – frequency optimizationBasic Theory

How to analyze my frequency plan• Frequency reuse distance• Frequency allocation reuse• Frequency load• Effective frequency load


Solution finding – frequency optimization Theory, Effective reuse• Since the frequency band is always limited, the frequencies have to be

reused in the network. • As the reuse distance becomes smaller, there are more frequencies

available for each cell, so more capacity can be provided. • The effective reuse is essentially the same as the conventional

frequency reuse distance.

where:

Reff = effective reuseNfreqsTOT = total number of used frequencies

NTRXave = average number of TRXs in a cell

Note! The smaller the effective reuse, the higher the capacity in terms of the number of TCHs provided by one frequency in the network.

RN

NefffreqsTOT

TRXave

=


Solution finding – frequency optimizationTheory, Frequency Allocation Reuse RF Hopping only

• Frequency allocation reuse indicates how closely th e frequenciesare actually reused in a network.

where:FAR = frequency allocation reuse

NfreqsTOT = total number of used frequencies

Nfreqs/MA = average number of frequencies in MA-lists

• It indicates the severity of a worst case C/I in the cell border.• If the network doesn’t utilize fractional loading, the frequency allocation

reuse is the same as the effective reuse.

FARN

NfreqsTOT

freqs MA

=/


Solution finding – frequency optimization Theory, Frequency load• The C/I is low when frequency collisions occur.

– In order to guarantee an adequate quality, the collision probability has to be made low. – The collision probability depends on the load of the hopping frequencies called a

frequency load.

• The frequency load describes the probability that a frequency channel is used for transmission at one cell at one time.

• The frequency load is a product of two other loads: – hard blocking load (the average busy hour TCH occupancy in most of the cases)– fractional load

where:Lfreq = frequency loadLHW = the busy hour average hard blocking load (see next slides)Lfrac = fractional load (see next slides)

L L Lfreq HW frac= ⋅


LT

NHWhopTCH

hopTCH

=

Solution finding – frequency optimization Theory, Hard blocking load• The hard blocking load is calculated as

where:LHW = hard blocking load

ThopTCH = average number of used TCHs in the busy hour

NhopTCH = total number of TCHs in the hopping TRXs


Solution finding – frequency optimization Theory, Fractional load• Fractional load means that the cell has been allocated more frequencies

than TRXs. This is only possible for RF hopping TRXs. • The fractional load is very useful when the number of TRXs is low. By

utilizing fractional load, it is possible to provide enough frequencies to hop over (to get FH gain) to even a cell with just one hopping TRX.

where:

Lfrac = fractional load

NTRX = number of TRXs in a cellNfreqs/cell = number of frequencies allocated to a cell (MA-list length)

LN

NfracTRX

freqs cell

=/


Solution finding – frequency optimization Theory, Frequency Load,HW and fractional load

BCCH 1 2 3 764

0 1 2 3 764

0 1 2 3 764

0 1 2 3 764

TRX-1

TRX-2

TRX-3

TRX-4

f1

f2, f3, f4, f5, f6

f3, f4, f5, f6, f2

f4, f5, f6, f2, f3

5

5

5

5

Active slotsActive slots Empty slotsEmpty slots

•“HW load” is 75%•Fractional load FL is3 TRX / 5 F = 0.6 = 60%•“Frequency load” is HWL * FL = 45%

•“HW load” is 75%•Fractional load FL is3 TRX / 5 F = 0.6 = 60%•“Frequency load” is HWL * FL = 45%

75 % 25 %

(E)GPRS is on the BCCH layer in this case


Solution finding – frequency optimization Theory, Effective Frequency Load

• Coverage limited network has low EFL• Interference limited network has high EFL

• It is calculated by the equation mentioned below:


Solution finding – frequency optimization Visual BCCH Plan Inspection

Heavy re-use of 582

584 re-used close together

584 re-used close together


Solution finding – frequency optimization BCCH Carrier Utilisation

0

10

20

30

40

50

60

51

3

51

4

51

5

51

6

51

7

51

8

51

9

52

0

52

1

52

2

57

0

57

1

57

2

57

3

57

4

57

5

57

6

57

7

57

8

57

9

58

0

58

1

58

2

58

3

58

4

Occ

urr

en

ces

C arriers also used in MA List

Channel distribution


Solution finding – frequency optimization BSIC Utilization

• As can be seen from the figure, amount of BSIC combinations are not spread smoothly

• BSIC planning is not properly done => risks to double BCCH+BSIC combinations is increased

BSIC allocation distribution

Note! Good radio network is based on properly done BSIC + BCCH Planning


Solution finding – frequency optimization

Same color = same frequency

Signal level is good, but quality is bad=> Frequency plan is not properly done


Solution finding – frequency optimization Different frequency planning methods

ExerciseHow these planning methods differs from each other?

• Based on Prediction tools– Planning Tools with propagation models

• Based on Interference matrix – Optimizer

• Mapinfo– Visualization

Any other methods?


Solution finding – frequency optimization Frequency HoppingNetwork capacity and performance is typically limited by co-channel interference, multipath fading, delay spread and noise

Frequency Hopping benefits are based on:Interference Diversity• where interference is averaged over

multiple frequenciesFrequency Diversity• which reduces the needed fading

margins

Interference averaging and reduced immunity to signal fading gives the possibility to reduce the C/I margins and tighten the frequency reuse schemes

Interference

F1

F2 F3

MS_1 MS_2 MS_3

F1

F2

F3 F1

F2 F3

average

Interference Diversity

Frequency Diversity

DistanceMS Location

F3

F2

F1

Bursts sent on frequency F2 may be degraded or lost, but the initial signal is still be reconstructed from the bursts on frequencies F1 and F3.

SignalLevel


Solution finding – frequency optimization Frequency Hopping

Baseband Hopping

TRX 1

TRX 2

TRX 3

0 1 72 Timeslot

TRX 4

BCCH

f 1

f 2

f 3

f 4

HSN1Timeslot 0 hops over TRXs 2-4 onlyBCCH does not hop

HSN2Timeslots 1-7 hop over all TRXs

TRX 1

TRX 2

TRX 3

0 1 72 Timeslot

TRX 4

BCCH f1 – no hopping

f2,f3..fn – hopping accordingmobile allocation list One hopping sequencenumber only

RF Hopping


• Loose interference control

• Relies on random spreading of the interference

• Loose interference control

• Relies on random spreading of the interference

BCCH

Random FH

Random FHover a fixed frequencylist

TRX 1

TRX 2

TRX 3

TRX 4

DFCA

TRX 1

TRX 2

TRX 3

TRX 4

BCCHCyclic FHover individually selectedfrequency lists and MAIOsfor each connection

C/I > C/I target

• Accurate interference control (C/I estimations)

• Each connection is assigned with the most suitableradio channel (MA list, MAIO, TSL)

• Accurate interference control (C/I estimations)

• Each connection is assigned with the most suitableradio channel (MA list, MAIO, TSL)

Solution finding – frequency optimization DFCA – (Dynamic frequency & channel allocation)


Cell A Cell B

Frequency optimization – Consistency check Cells with co-channel and adj-channel frequencies

FREQ=10 FREQ=9,10,11

• Co-channel frequencies: HO is not possible in case of co-BCCH

• Adj-channel frequencies: Ho is possible but might fail due to interference.

• If Co / Adj-channel frequencies are existing, these must be removed

A

B

-6dB -9dB


Small distances may be dangerous!

Reuse 4/12

FREQ = 234

BSIC = 42

FREQ = 234

BSIC = 42

FREQ = 234

Frequency optimization – Consistency check Check BCCH -BSIC and BCCH reuse distance


• Neighbors with co-channel frequencies• Neighbors with adj-channel frequencies• Neighbors of a same cell with co-BSIC, co-BCCH• Neighbors from other Vendor• Frequencies / co-BSICs near the country border ( if available)

Frequency optimization – Consistency checkOther Checks


Examples of wrong parameter setimpact on network operation/performance – frequencie s

1. Drop call rate increase after new frequency planimplementation

• Double BA List activated

2. Impossibility to unlock some BTS after a RF-frequency hopping implementation

3. Impossibility to unlock some BTS after a frequency retune• NON-EDGE TRX, with GTRX = Y• TRX, with GTRX = Y, not attached to any EDAP pool


Example 1

Drop call rate increase after new frequency plan implementation:• In the meantime, measurementBcchAllocation has been changed to

idle and MA list defined with old BCCH frequency band

BCCH TCH OLD FREQUENCY PLAN

BCCH TCH NEW FREQUENCY PLANTCH

OLD MA List

These BCCH frequencies will not be measured by old MA List

These TCH frequencies will be wrongly measured


Example 2

• After frequency hopping retune, some BCCH frequency equal to TRX frequency of non-BCCH TRXs

• After changing TRX frequency, verify BSIC and TSC (Training Sequence Code) is changed accordingly.

Not possible to unlock some BTS after a RF-frequency hopping implementation:


Example 3a

Impossibility to unlock some BTS after a frequency retune:• NON-EDGE TRX, with GTRX = Y, in a cell with EGENA set

to yes

B

BTS

NON-EDGE TRX(s)

(E)GPRS territory

EGENA = Y

SEG

GTRX = Y

EDGE TRX(s)

BTS

NON-EDGE TRX(s)

EGENA = Y

SEG

GTRX = N

EDGE TRX(s)B(E)GPRS territory

GTRX = Y GTRX = Y


Example 3b

Impossibility to unlock some BTS after a frequency retune:• TRX, with GTRX = Y, not attached to any EDAP pool in a cell

with EGENA set to yes

BTS

NON-EDGE TRX(s)

EGENA = Y

SEG

GTRX = N

EDGE TRX(s)B(E)GPRS territory

GTRX = Y

EDAP pool

1

2

Add TRX-1 to EDAP pool


Neighbor Optimization


Solution finding – neighbor optimization

• Keep the neighbor list in order.– Note! If lots of overshooting => dominance areas are not clear => neighbor

list are getting bigger. – Bad overshooting should be avoided– Missing neighbors – the worst situation

• Use the Handover Adjacency Statistics to identify and remove neighbors

– Bad overshooting cells can cause problems

• ISHO optimization

Avoid:• neighbor definitions that are co-BCCH and co-BSIC or Adj-BCCH and

co-BSIC that can lead to wrong neighbor reporting• One-way neighbors



GREEN = sourceRED =neighbor cellBLUE = no neighbor

As can be seen, neighbors are not fully optimized. There are missing neighbors and on the other hand, some far away cells are neighbors



GREEN = sourceRED =neighbor cellBLUE = no neighbor

Overshooting cells => added to neighbor list.Neighbor planning is more difficult to do, if lots of overshooting cells

In this area there might be big problems due to unoptimizedneighbors



SEA

Challenges• Sites by the sea

• Dominance areas are reaching far away => neighbor cells can be far away

• Indoor solutions• Signal levels from outdoor cells

near windows can be high

• High buildings• Lots of cells can be heart near

the window

• 3G cells• Limited amount of neighbors

Only few neighbor cells => in the sea there will be problems



Neighbor optimization based on statistics• HO attempts, blocking and fails can be analyzed as source or

target cells• Neighbor removing can be done based on stats

In case Number of HO Attempts is very low to a certain cell, consider removing this cell from Adjacency list.


Cell A Cell B

Neighbor Planning – Consistency check Non symmetrical adjacencies

Find all non symmetrical adjacencies :• cell B is neighbour of Cell A• cell A is not neighbour of Cell B

• If there are non symmetrical adjacencies, these must be changed to symmetrical adjacencies


Neighbor Planning – Consistency checkNeighbours with co-channel and adj-channel frequenci es or co-BSIC, co-BCCH

Cell A

f=24

Cell B

f=10, BSIC=2,2

f=24f=9,10,11

f=10

Neighbours with co-BSIC, co-BCCH:

• Might generate ghost-access and HO drop calls.

• High sdcch abis failure and high handover failure could be indicators for this case.

Neighbours with co-channel or adjacent channel frequencies:

•Will cause interference between neighbour cells

Cell C

f=10, BSIC=2,2


Solution finding – neighbor optimization Different methods

ExerciseHow these planning methods differs from each other?1.Add maximum nbr of neighbors and after 2 weeks remove

extra neighbors based on HO statistic2.First only nearest (dominance area) and if problems, add

more neighbors

In neighbor optimization following selection methods can be used

• Based on Optimizer• Based on Map• Based on OSS Statistics


• Check cells in MSC vs cells in BSC• Check external adjacencies in MSC• Non symmetrical adjacencies • Neighbors of a same cell with co-BSIC, co-BCCH• 3G neighbors

Neighbor planning – Consistency checkOther Checks


Handover Optimization


Solution finding – HO optimization

HO Strategies – Traffic handling (900-1800 layers)

900layer

1800layer

PBGT, quality, level

UmbrellaTraffic ReasonIUO

PBGT, quality, level



Optimizing HOs, Reduce unnecessary HOs• DL Level HO typically (-94dB)• Quality HO 3dB

• HO Level margin 2dB

=> if Cell1 -98dBm => Cell2 >-96dBm => HO

=> might be HO fail if for example some imbalance

⇒HO level margin => 24dBm (=disabled in this case)

⇒Quality HO 3dB (HO is done only if quality problems)⇒No HO, AMR is used => no drops and quality is OK

⇒ PBGT is still working. Value can be decreased if problems)

Cell1 Cell2route

Unnecessary HO is prevented in this area

old

new

-100dBm

-100dBm



Optimizing HOs, HO parameters

• Umbrella ( AUCL parameter)• AMR FR/HR

– Packing, unpacking parameters

• Interference / quality HO– If interference level -75dB => interference problems in good signal level

– Rest are quality HOs => bad quality can be also due decreased signal level.

– This difference is good to know

• Level / PBGT– If margin is same as PBGT, the only difference is level, See example in

previous slide where Level HO disabled.

– It is useful to know if overlapping in good signal level and bad signal level� Can be noticed if overshooting

� If no Level HOs => real coverage problems without overlapping


UURF

LURF

No action

Quality(BER)

RxLevel

-110dBm -47dBm

3

0

UU

R (

PO

C)

-70

LUR

(P

OC

) -9

5

(PxNx: 2/3)

(PxNx:6/16)

(PxN

x:1/

1)

(PxN

x:1/

1)

(PxN

x: 1

/1)

LUR

(H

OC

) -9

5

Solution finding – HO optimizationAMR + Power Control & HO control co-ordination in U L

IHRF(PxNx:4/6)

(AMR) Qual HOHYS -6dB

(PxNx: 4/6)4IHRH

5QURF

Power down quality Packing of the call

Unpacking the call

Pow

er d

own

leve

l

Pow

er u

p le

vel

Power up quality

Han

dove

r tr

igge

r1

Handover trigger


HO Optimization – Consistency check Synchronized handover

Site BSite A

Non-synchronized Handover– MS sends access bursts (HO_ACCESS) (with varying TA)

until it receives PHYSICAL_INFOSynchronized Handover

– MS sends a few access bursts (HO_ACCESS) and then starts transmission with previous TA

Non-synchronised handover leads to a longer communication interruption than synchronised handover (200ms vs. 100ms)

Synchronized HO should be activated between sectors of the same site. If activated on inter-site adjacencies the handover can fail

Synchronized HONon- Synchronized HO


Solution finding – HO optimization Different methods

Exercise 1In which case the network is working better? (theoretical)

• All handovers are quality handovers• All handovers are level handovers

Exercise 2How these differs from each other?

• Quality HO vs. Interference HO• PBGT vs. Level HO• Traffic handling : decreased power 2 dB vs. decreased HO

margin 2dB


• Check cells in MSC vs cells in BSC• Check external adjacencies in MSC• Neighbors with co-channel frequencies• Neighbors with adj-channel frequencies• Neighbors of a same cell with co-BSIC, co-BCCH• Check site with same MA List in different sectors and different

HSN• Check site with same MA List in different sectors and MAIO

collision

HO planning – Consistency checkOther Checks


1. No handover from a cell towards all its neighbours• PLMN permitted = No

2. High Handover failures after implementation of new adjacency plan• SYNC = YES

3. No handover happening from an interfered cell• hoMarginQual set to 0

4. 100% of handover failures in an adjacency relation• Co-BSIC co-BCCH declarati

5. High number of handovers• hoThresholdsLevUL = hoThresholdsLevDL

6. Handover not happening when DL signal level of neighbour much greater than serving cell• POC DL activated

Examples of wrong parameter setimpact on network operation/performance – Handover


Example 1

No handover from a cell towards all its neighbours:• PLMN permitted not set properly. MML Default value is the NCC of the

BTS. So HOs will not happen towards neighbours with different NCC.

Cell ANCC 3

Cell BNCC 4

Plmn permitted 0 = No

….

Plmn permitted 3 = Yes


…


Set Plmn permitted 4 = Yes

PLMN permitted parameter consists actually of 8 parameters (0 …7) related to the NCC part of the BSICs of neighbour cells. MS only reports measurements of cells with NCC permitted (plmn permitted = YES).

No Measurement reports of Cell B are sent to BSC. So no HOs occur from Cell A to Cell B


Example 2

High Handover failures after implementation of new adjacency plan• All adjacencies have been implemented with synchronised

parameter set to yes. HOs between cells of different sites will probably fail.

SYNC = YES

SYNC = NONew Channel, New Cell

ACTIVE CALLHANDO CMD

HANDO ACC

HANDO COMACTIVE CALL

MS NETWORK

Old Channel, Old Cell

PHYS INFOx

Synchronized Handover Set SYNC = YES only between sectors of the same site.

Recommendation is to have Sync HO within BTSs in the same BCF and Non Sync HO between BTSs in different BCFs.


Example 3

No handover happening from an interfered cell• hoMarginQual set to 0

In an interfered cell, despite high signal strength, quality is not good. So HO Margin Qual should permit HO to a cell that despite it’s lower signal strength, may have a better quality.

A

B

PBGT margin = 6dBHo Margin Qual = -4

Ho Margin Qual = 0

(MML Default)


Example 4

100% of handover failures in an adjacency relation• Co-BCCH declaration (Co-BSIC)

Cell A Cell B

FREQ=10

BS IC = 33

FREQ=10

BS IC = 33

�


Example 5

0

1

2

3

4

5

6

7

-110

-108

-106

-104

-102

-100 -9

8

-96

-94

-92

-90

-88

-86

-84

-82

-80

-78

-76

-74

-72

-70

-68

-66

-64

-62

-60

-58

-56

-54

-52

-50 dBmdBm

QualityQuality

HoThresholdLevUL/DL

HoThresholdInterferenceUL/DL

Interference HoInterference Ho

No Action NeededNo Action Needed

Quality HoQuality Ho

Level HoLevel Ho

HoThresholdLevDLHoThresholdLevUL

High number of handovers. hoThresholdsLevUL = hoThresholdsLevDL

hoThresholdsLevUL

, high thresholds will

anticipate HOs:

-95 -> -100

hoThresholdsLevDL

:

-95 -> -90


Example 6

Handover not happening when DL signal level of neighbourmuch greater than serving cell• Power control DL activated

A

B

-6dB

-3dB

Power Control

-9dB


(E)GPRS Optimization


Objectives

After PS optimization module learning • You know the impact of GSM performance on (E)GPRS

performance• You know the main assessment activities• You know how the signaling, throughput and mobility can be

optimized


GSM Network as the physical layer of (E)GPRS

The optimal GSM network from PSW services point of view has: 1. As high signal level as possible

� It means that even the indoor signal level should be high enough to have MCS9 for getting the highest data rate on RLC/MAC layer.

2. As low interference as possible � The aim of having high C/I is to avoid throughput reduction based on interference.

3. Enough capacity� Enough BSS hardware capacity (interface and connectivity) is needed to provide the

required capacity for PSW services in time. Both CSW and PSW traffic management should be harmonized with the layer structure and long term plans.

4. As few cell re-selection as possible� The dominant cell coverage is important to avoid unnecessary cell-reselections in

mobility. The prudent PCU allocation can help to reduce the inter PCU cell reselections.

� Dominant cell structure can help to maximize the signal level and reduce the interference, too.

5. Features� All the features should be used which can improve the PSW service coverage,

capacity and quality in general.

6. The GSM network is the physical layer of (E)GPRS, so the optimization of GSM network can improve the performance of (E)GPRS, too.


(E)GPRS Optimization – TSL data rate optimization

Timeslot optimization is based on basic optimization– Interference optimization– Coverage optimization

RLC/MAC Data Rate (FTP Download on 2 TSLs)

0

20

40

60

80

100

120

-65 -70 -75 -80 -85 -90 -95 -100 -105

Signal level (dBm)

kbps

No Interference

C/I 25 dB

C/I 20 dB

C/I 15 dB

Data rate is heavily depending on network quality• Better quality

⇒ Better throughput

⇒ Less blocking


(E)GPRS Optimization –Network Element and Configuration Assessment

BSC GGSN

IP/MPLS/IPoATM -

Application Servers

(co-located

2GSGSN

BTS

HLR/AC/EIR

TCSM

TC

MSC/VLR

Abis GbBSC BSC

GGSNGGSN

-backbone

Application Servers

2GSGSN

2GSGSN

BTS

HLR/AC/EIR

HLR/AC/EIR

TCSM

TC

MSC/VLR

GnGi

Gs

RF interface

• Coverage

•C/I

• Capacity

• Traffic volume

• Mobility

MS/Client parameters

• GPRS/EDGE capability and release

•Multislot support

Abis interface

• EDAP size / dimensioning

• # of E1/T1s

• GPRS/EDGE traffic

Gb interface

• Bearer size

• IP v.s. FR

• Dimensioning

BTS

• GPRS territory

• BTS HW considerations (TRX & BB-card)

• BTS SW (EPCR)

BSS

• PCU variant & dimensioning

• PCU strategy in mixed configuration

• BSS SW and features

SGSN

• Unit capacity (PAPU etc.)

• BSS Gb Flow control

RF

Server

• load

• settings (Linux/Win)

HLR

• QoS profile

• GPRS settings


(E)GPRS Optimization - Introduction

(E)GPRS Network Optimization

•Signaling capacity & resource allocation improvement

•Data Rate– Connectivity Capacity (MS-SGSN)– Multiplexing and multislot usage maximization

•Mobility improvement


(E)GPRS Optimization - Signaling Capacity & Resource Allocation improvement

• Signaling– PCH, AGCH, RACH and SDCCH (NMOII)

• Resource Allocation– Cell (re)-selection– BTS selection– Scheduling


(E)GPRS Optimization - RF Signaling Paging Measurements (NMO I)Traffic Volume• cs_paging_msg_sent (c3058) (CS pagings from Gb)• ps_paging_msg_sent (c3057) (PS pagings from Gb)

Congestion (CS + PS)• max_paging_gb_buf (003050)

Paging success ratio on CS • PAC_PAG_REQ_FOR_CS_PAG (c72083) / (cs_paging_msg_sent) (c3000)

Success ratio of Paging on Gs interface (2G SGSN)

sum(DL_MESSAGES_DISCARDED_IN_GS(11000)) Sgsn_961a = ----------------------------------------------------------------------- * 100

sum(CS_PAGING_MSGS + DL_TOM_MSGS)

Solution for reducing PCH rejection and load• Usage of combined structure, modifying MFR and PER parameters• LA/RA re-planning • Cell splitting


(E)GPRS Optimization - RF Signaling AGCH MeasurementsImmediate AssignmentTraffic Volume (with Rejection)• imm_assgn_sent (c3001) - Imm Assign)

• imm_assgn_rej (c3002) - Imm Assign Rejected

• packet_immed_ass_msg (c72084) - P-Imm Assign

• packet_immed_ass_rej_msg (c72087) - P-Imm Assign

Congestionpacket_immed_ass_nack_msg

blck_21b = -------------------------------------------------------------------------packet_immed_ass_nack_msg + packet_immed_ass_ack_msg

Solution for reducing AGCH rejection and load• Usage of combined structure, modifying AG and CALC parameters• Immediate Assignment messages are shared between PCH and AGCH

• PBCCH implementation (in case of high (E)GPRS signaling traffic)


(E)GPRS Optimization - RF Signaling RACH Measurements

Traffic VolumePACKET_CH_REQ (c072082) (PSW)CH_REQ_MSG_REC (c003004) (CSW)

LoadRACH_4 = 100 * avg(ave_rach_busy(C3014)/res_acc_denom3(c3015))

avg(ave_rach_slot(c3006)/res_acc_denom1(c3007))

Repetitions of PS channel requests (load and quality)RACH_9 = UL_TBF_WITH_RETRY_BIT_SET (c072020) / PACKET_CH_REQ (c072082)

Solution for reducing RACH rejection and load• Usage of non combined structure, modifying RET parameter

• PBCCH implementation (in case of high (E)GPRS signaling traffic)

• Reducing high UL interference (and DL interference if the repetition is too high)


(E)GPRS Optimization - RF Signaling SDCCH Measurements (NMO II with LA Update)

Traffic Volume– SDCCH seizure attempts (c1000)– Average available SDCCH (ava_45a)

Congestion– Blocking on SDCCH, before FCS (blck_5)– Time congestion on SDCCH (cngt_2)

Solution for reducing SDCCH load– Increase of Periodic RA update timer (PRAU) / MS Reachable timer (MSRT)

� Drawback: more PAPU capacity is needed and more paging will be generated, if the MS is out of service

– More SDCCH TSL allocation and/or Dynamic SDCCH feature usage– Combined RAU (NMO-I with Gs for (E)GPRS)– (Resume feature decreases the amount of RAUs)– LA and border re-planning


(E)GPRS Optimization - Resource Allocation IntroductionBasic Allocation related Topics• PSW Activation• Territory settings• Channel pref.

Cell-(re)selection• C1, C2• C31/C32• NCCR

BTS Selection• MultiBCF and CBCCH• PCU algorithm

Channel Scheduling• Priority based QoS

Provide enough capacity to PSW traffic in general (find balance between CSW and PSW)

Allocate the traffic to the most appropriate resource

Separate GPRS and EGPRS and share the resources

Service and user prioritization

RLC/MAC

User


BCCHTRX 1

TRX 2

TS

Circuit Switched Territory

Circuit / Packet Switched Territory

Dedicated GPRS

Capacity (%)

TS TS TS TS TS TS

TS TS TS TS TS TS TSTS

Territory downgrade forced by the Circuit Switched traffic

Territory upgrade in interval of Territory Upgrade Guard Time

Default GPRS capacity thresholdExtra GPRS capacity

Free time slots in Circuit Switched territory

Default GPRS Capacity (%)

(E)GPRS Optimization –GPRS Territory• Circuit Switched traffic has priority outside dedicated territory

• GPRS dedicated time slots (% of total cell capacity) can be defined. Only (E)GPRS can use, no CSW

• Dedicated TSL is subset of Default TSL• Territories consists of consecutive timeslots

• GPRS can be set to favour the BCCH Transceiver -> minimum interference


Cell (re) - selection(E)GPRS Optimization –Cell (re) - Selection


(E)GPRS Optimization –BTS Selection and TSL AllocationBTS selection and TSL allocation is

Segment

Initial BTS SelectionReallocation of TBFs among the BTS

1. BTS Load reallocation2. Uplink Rx level reallocation3. Downlink Rx level

reallocation 4. Downlink RX level received

first time reallocation


7

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

7 8 9 10 11 12 12 13 14 15 16 17

12 12 12 12 12 12 13 18 18 18 18 18

(time)

52 TDMA frames = 240 ms= 12 blocks

i t it

The scheduling is done based on latest service time, one TBF at a time is served by the RTSL

Latest service time

TBF1 with SSS=6

TBF2 with SSS=1Latest Service Time = Current Time + Scheduling Step Size

(E)GPRS Optimization –Resource Allocation - Priority based QoS


(E)GPRS - Throughput optimization

• Connectivity Capacity (MS-SGSN)• TSL data rate improvement and multislot usage maximization

(BSS)• E2E data rate (applications)


(E)GPRS OptimizationConnectivity Planning – Maximized Capacity

• The connectivity optimization for maximum capacity is based on the proper set of CDEF and DAP size.

• To provide enough capacity for territory upgrade the 75 % utilization in the connectivity limits is recommended by NSN

• PCU Connectivity capacity limits can be seen below

Outputs Max limit* Utilization Limit unitAbis channles (radio TSLs) 256 75% 192 TSLsEDAP pools 16 75% 12 pcsBTS (cell, segment) 64 75% 48 pcsTRXs 128 75% 96 pcs*PCU & PCU-S handle 128 radio TSLs only with S11.5

*PBCCH is not implemented


(E)GPRS Optimization Connectivity in different PCUs

PCU variant BSC Type BSS11BSS11.5

ownwards

BTS 64 64

TRX 128 128Radio TSLs 256 128Abis 16 kbps channels 256 256

Gb 64 kbps channels 31 31BTS 64 64

TRX 128 128Radio TSLs 256 128

Abis 16 kbps channels 256 256Gb 64 kbps channels 31 31

BTS 64 64TRX 128 128Radio TSLs 256 256

Abis 16 kbps channels 256 256Gb 64 kbps channels 31 31

BTS N/A 128TRX N/A 256Radio TSLs N/A 256

Abis 16 kbps channels N/A 256Gb 64 kbps channels N/A 31

BTS 2 x 64 2 x 64TRX 2 x 128 2 x 128

Radio TSLs 2 x 256 2 x 256Abis 16 kbps channels 2 x 256 2 x 256Gb 64 kbps channels 2 x 31 2 x 31BTS N/A 2 x 128TRX N/A 2 x 256Radio TSLs N/A 2 x 256Abis 16 kbps channels N/A 2 x 256Gb 64 kbps channels N/A 2 x 31

PCU2-D BSC3i

PCU2-U

PCU-T BSCE, BSC2, BSCi, BSC2i

BSCE, BSC2, BSCi, BSC2i

PCU-B BSC3i

PCU BSCE, BSC2, BSCi, BSC2i

PCU-S BSCE, BSC2, BSCi, BSC2i


(E)GPRS Optimization Connectivity Planning – Cells / PCU

EGPRS BSS Configuration Portfolio (ETSI)

extra small (XS)

small (S)

medium (M)

large (L)

extra large (XL)

data monster (DM)

Use case

lowest cost per EGPRS cell: maximize EGPRS cells per PCU

low cost: high EGPRS cells per PCU ratio Basic EGPRS site

High data volume EGPRS site

Extra high data volume site Data hot spot site

ParametersCDEF 1 2 4 4 4 4DAP 3 4 6 8 11 16

# of cells / PCU with utilizationcells per DAP 2 2 2 2 2 2

#DAPs per PCU 16 11 7 5 4 3#EGPRS cells per PCU 32 22 14 10 8 6PCU Abis ch utilization 88% 86% 88% 78% 81% 84%

average cells per DAP 2.5 2.5 2.5 2.5 2.5 2.5#DAPs per PCU 15 10 6 5 4 3#EGPRS cells per PCU 37 25 15 12 10 7PCU Abis ch utilization 85% 82% 80% 81% 84% 86%

cells per DAP 3 3 3 3 3 3#DAPs per PCU 15 10 6 5 4 3#EGPRS cells per PCU 45 30 18 15 12 9PCU Abis ch utilization 88% 86% 84% 86% 88% 89%

Performance figures (kbps) (n+n+n)single user peak RLC/MAC (#RTSL in DL) 186 237 237 237 237 237cell peak RLC/MAC (gross) 354 325 373 597 748 829

notes fo applying

area for low EGPRS traffic, no performance commitments

areas for low+ EGPRS traffic, support 4 RTSL MS FTP max throughput

areas for medium EGPRS traffic, supports 4 & 5 RTSL MS FTP/HTTP max throughput

areas for high EGPRS traffic

areas for extra high EGPRS traffic

hot spot site for EGPRS

The following table shows the number of EGPRS cell / PCU calculations for the different configuration types.

The following configuration types were defined:Extra small (CDEF →1 RTSL, DAP → 3 TSL)Small (CDEF → 2 RTSL, DAP → 4 TSL)Medium (CDEF → 4 RTSL, DAP → 6 TSL)Large (CDEF → 4 RTSL, DAP → 8 TSL)Extra large (CDEF → 4 RTSL, DAP → 11 TSL)Data monster (CDEF → 4 RTSL, DAP → 16 TSL)

Data monster(DM)

Data hot spot site)

Hot spot siteFor EGPRS


(E)GPRS Optimization - KPIs

• DL MCS selection limited by EDAP (dap_7a)– Similar formula for DL (dap_8c)

– DL_TBFS_WITH_INADEQ_EDAP_RES (c076008)� c76008 includes lack of PCU resources (c76020

DL_MCS_LIMITED_BY_PCU ) as one reason.

� If c76008 is updated but peak EDAP usage is less than 100%, reason is that c76008 has been updated because of lacking PCU resources,

Target values:Good: < 75 min/GByteBad: > 150 min/GByte


(E)GPRS Optimization - KPIs

• DL MCS selection limited by PCU (dap_9)– Similar formula for UL ( dap_10)

Target values:Good: < 15 min/GByteBad: > 30 min/GByte


(E)GPRS Optimization - Multiplexing

Channel Allocation Algorithm tends to separate EDGE TBFs and GPRS TBFs on different RTSL to avoid multiplexing, if only one PS Territory exists in the cell or there is high load.• UL GPRS USF on DL EGPRS TBF• TSL sharing - GPRS/EGPRS TBFs’ multiplexing on a TSLThe algorithm checks the need for re-allocation every TBF_LOAD_GUARD_THRSHLD, in order to separate sessions.The max amount of TBFs per TSL can be limited:

1..7, default:7maximum number of TBFs that a radio time slot can have in average, in a GPRS territory, in the uplink

direction.

MNULMaximum Number of UL TBF

1..9, default:9maximum number of TBFs that a radio time slot can have in average, in a GPRS territory, in the downlink

direction.

MNDLMaximum Number of DL TBF

Range and DefaultDescriptionAbbreviationParameter Name

1..7, default:7maximum number of TBFs that a radio time slot can have in average, in a GPRS territory, in the uplink

direction.

MNULMaximum Number of UL TBF

1..9, default:9maximum number of TBFs that a radio time slot can have in average, in a GPRS territory, in the downlink

direction.

MNDLMaximum Number of DL TBF

Range and DefaultDescriptionAbbreviationParameter Name


(E)GPRS Optimization –Multiplexing – Measurements (KPIs) Amount of TBFs / TSLUplink TBFs pr timeslot tbf_37dDownlink TBFs pr timeslot tbf_38d

GPRS TBF multiplexed with EGPRS TBF8PSK coding scheme downgrade due to GPRS multiplexing rlc_61

DL EDGE TBFs in GPRS territory tbf_60UL EDGE TBFs in GPRS territory tbf_59Ratio of DL GPRS TBFs in EDGE territory tbf_58a

Ratio of UL GPRS TBFs in EDGE territory tbf_57a


(E)GPRS Optimization - Multislot usage Territory Downgrade and Upgrade

The territory downgrade heavily depends on the size of dedicated and default territory.• Territory downgrade due to CSW traffic rise

• Downgrade request below Default territory because of rising CSW (c1179)

• Territory downgrade due to less PSW traffic• Downgrade request back to the Default territory when there is no need for

additional channels anymore (c1181)

• Territory upgrade request rejection beyond default territory• Upgrade request beyond Default territory for additional resources (c1174),

which can be rejected because of:1. No (E)GPRS capable resource left (No (E)GPRS enable TRX or the maximum (E)GPRS capacity reached)

2. PCU and EDAP capacity limitation (256 Abis TSL per PCU)

3. High CSW load

0 1 2 3 4 5 6 7

Default territory

1174

1181

1180

1179

0 1 2 3 4 5 6 7

Default territory

1174

1181

1180

1179


(E)GPRS Optimization Free TSL Size (after CS Upgrade and Downgrade)

When a downgrade or upgrade procedure is requested following parameters can reduce or increase the border between CSW and PSW territories:

TSL number after CS downgrade

TRX number 1 2 3 4 5

70 0 0 0 1 1

95 1 1 1 2 2

99 1 1 2 2 3

TSL number after CS upgradeTRX number 1 2 3 4 5

1 0 1 1 1 2

4 1 2 2 3 4

7 1 2 3 4 5

10 2 3 4 5 6

free TSL for CS downgrade (%) (CSD)

free TSL for CS upgrade (sec) (CSU)


(E)GPRS Optimization Multislot Usage – Measurements (KPIs)Actual Territory• ava_44 • Peak PS territory (c2063)

Recommendation: Ava_44 and c2063 can be compared with the CDEF settings. If too big difference, then CDEF should perhaps be changed, or more capacity should be added to the cell.

Multislot Blocking• UL / DL multislot allocation blocking – hard (tbf_15a, tbf_16a)• DL multislot blocking – soft (blck_33a)Recommendation: Too much multislot blocking shows that the territory is perhaps not enough.

And it is also interesting to see how many timeslots which are requested (helpful in determining the size of the default territories)• Requested timeslots for GPRS TBFs c72039-c72149, c72040-c72150, c72041-

c72151, c72042-c72152• Requested timeslots for EDGE TBFs c72149, c72150, c72151, c72152


(E)GPRS Optimization - Mobility Optimization

The aim of mobility optimization is to reduce the cell outage time during cell re-selection.Cell outage can be reduced by• Providing enough signaling capacity for cell re-selection (the RACH, PCH,

AGCH and SDCCH channel are not limiting the signaling flow)• Rebalancing BCFs among PCUs properly (the important neighbors are

allocated to the same PCU)• Reallocating LA/RA borders properly • Enabling Network Assisted Cell Change (NACC) feature


(E)GPRS Optimization –Outage Definition Used in Measurements

Three delays can be calculated from logs:

Cell outage:• In one-phase access: the time

between the last EGPRS Packet Downlink Ack/Nack message and the first Packet Uplink Ack/Nack.

• In two-phase access: the time between the last EGPRS Packet Downlink Ack/Nack message and the first Packet Uplink Assignment.

Data outage:the time between the last and the first EGPRS Packet Downlink Ack/Nack message.

Application outage:the time between the last and the first successfully received FTP-packet.

EGPRS Packet Downlink Ack/Nack

MS GERAN

Routing Area Update Accept

Routing Area Update C omplete

F irst IP packets

Last IP packets

DataOutage

Application Outage

CellOutage

Routing Area Update Request

EG PRS Packet Downlink Ack/Nack

Packet Uplink Assignment


(E)GPRS Optimization Network Assisted Cell Change (NACC)NACC is in Rel 4 of 3GPP GERAN , mandatory for R4 mobiles. Nokia’s S11.5 implementation is based on Rel4.Both, autonomous and network controlled cell reselections are supported.Support is for intra-BSC cell changes (Support of inter-BSC NACC specification is available in Rel 5) NACC support is for MSs in RR Packet Transfer Mode only

�NACC shortens the cell reselection in two ways:

• Sending neighbour cell system information on PACCH to MS in packet transfer mode while it is camped on the serving cell

• By supporting PACKET SI STATUS procedure in a target cell


(E)GPRS Optimization –CS Traffic vs. PS Traffic CS and PS peak values at the

same time (BSC level data) ⇒ Bad for PS timeslot allocation ⇒ Lots of downgrading

ExerciseHow to optimize PS performance on area level?


Alarms


Alarms - Introduction

Alarm analysis is the 1st thing to be done in worst cell Alarm analysis is the 1st thing to be done in worst cell troubleshooting! No use optimizing parameters if you have a troubleshooting! No use optimizing parameters if you have a HW problem!HW problem!

Bad performance of a cell may be caused by faulty equipment. • Check that there are no performance-affecting alarms in the cell monitored and

also in neighbour cells!• Alarms are usually transferred to the NetAct database.• Monitoring can be done through MML Commands, Nokia NetAct Top Level User

Interface

Note! Constant monitoring is needed in order to avoid critical alarms in any network element.


Alarms – Groups

Alarm number in: Notices (NOT ICE)

Disturbance printouts (DISTUR)

Failure printouts

(ALARMS)

Diagnosis reports

(DIAGN)

Base station alarms

T ransmission equipment

alarms

Numbers reserved for

possible external alarms

switching equipment 0–799 1000–17992000–2799 3000–3799 4000–4799

O&M equipment 800 - 899 1800–18992800–2899 3800–3899

4800–4899

transmission equipment

900 - 999 1900–1999 2900–2999 3900–3999

4900–4999

diagnosis report number 3700–3999

base station/ transmission equipment alarms

7000–7999 8000–8999

power equipment 5000–5499

external equipment 5500–5999


Alarms – Printout Fields

• Alarm Number

• BCF number, BTS number, TRX number, Alarm Object, Unit, Date, Time, Alarm Number

• Urgency level

• Printout typeALARM fault situation CANCEL fault terminated DISTUR disturbance NOTICE notice

• Event type

COMM communication failure

QUAL quality of service PROCES processing failure EQUIPM equipment failure ENVIR environmental failure

Note:

The urgency level is output in all alarm printouts except notices (NOTICE).

The urgency levels of terminated alarms are indicated by dots (.) instead of asterisks (*).

* Low Priority

** Med Priority

*** High Priority


Alarms - Alarms in MML

Alarms in BSC Level:– ZAHO: PRINT ALARMS CURRENTLY ON– ZAHP: PRINT ALARM HISTORY

Alarms in BTS Level: – ZEOL: LIST ALARMS CURRENTLY ON– ZEOH: LIST ALARM HISTORY

BCF, SEG or BTS configuration and status– ZEEI: OUTPUT RADIO NETWORK CONFIGURATION

TRX and RTSL configuration and status– ZERO: OUTPUT TRANSCEIVER PARAMETERS

Verify if BCF, SEG, BTS, TRX and RTSL are LOCKED or UNLOCKED; WO (working), BL- USR (blocked by user) or Restarting.


Alarms - Alarms in MML

HW Tests:• ZUBK: HANDLE ABIS LOOP TEST

(Parameters: BTS, TRX, RTSL, Fixed or Dynamic Abis connection and Abis TSL and Sub-TSL, looping time)

• ZUBS: START TRANSCEIVER TEST(Parameters: BTS, TRX, RTSL, test mode, RTSL,test selection, diversity path selection,test connection, RF test signal attenuation,BTS RX level,STM antenna attenuation,BS TX power attenuation, loop duration)


Alarms - Examples

• 2993: BTS AND TC UNSYNCHRONIZATION CLEAR CALLS ON ABIS INTERFACE

– Transcoder and transmission alarm. Abis test is needed.

• 7045: TRX/FU DATA TRANSFER ERROR BETWEEN FU AND CU16– Base Station alarm. Observed when TCH failure rate is very high. A possible

solution can be to change the TRX.

• Example of a BTS alarm printout:


Alarms - Top Level User interface

• The Top-level User Interface contains graphical views of the network, inwhich network elements are represented hierarchically with symbols

• One of the main functions of the Top-level User Interface in network monitoring is to show the alarm situation in all managed objects


Implementation / Documentation


Implementation / Documentation

• Optimization process is an iterative process, so there is no need to create troublesome final report after every circle. Main items must be still written down after every circle.

• All the activities/ findings should be listed– What should be done and when

– “recommendation for the changes to be done" and "working orders".

• All improvements should be shown– Implementation time should be shown

with improvementsNetwork Report

Tasks AndResults


Solution Verification


Solution Verification

EGPRS RLC Throughput kbit/s/TSLBSC KRASNODAR

0

10

20

30

40

50

60

19.10

.21

.10.23

.10.

25.10.

27.10

.29

.10.31

.10.2.1

1.4.1

1.6.11

.8.1

1.10.1

1.12

.11.14.1

1.16

.11.18

.11.

20.11.

22.11

.24

.11.26

.11.

28.11.

30.11.2.1

2.4.1

2.

kbit/

s

DL

UL


0

10

20

30

40

50

60

19.10

.21

.10.23

.10.

25.10.

27.10

.29

.10.31

.10.2.1

1.4.1

1.6.11

.8.1

1.10.1

1.12

.11.14.1

1.16

.11.18

.11.

20.11.

22.11

.24

.11.26

.11.

28.11.

30.11.2.1

2.4.1

2.

kbit/

s

DL

UL


0

10

20

30

40

50

60

19.10

.21

.10.23

.10.

25.10.

27.10

.29

.10.31

.10.2.1

1.4.1

1.6.11

.8.1

1.10.1

1.12

.11.14.1

1.16

.11.18

.11.

20.11.

22.11

.24

.11.26

.11.

28.11.

30.11.2.1

2.4.1

2.

kbit/

s

DL

UL


0

10

20

30

40

50

60

19.10

.21

.10.23

.10.

25.10.

27.10

.29

.10.31

.10.2.1

1.4.1

1.6.11

.8.1

1.10.1

1.12

.11.14.1

1.16

.11.18

.11.

20.11.

22.11

.24

.11.26

.11.

28.11.

30.11.2.1

2.4.1

2.

kbit/

s

DL

UL

• The purpose is to check was solution succeed– Is the trend positive or negative after aimplementations– Check that collected data is valid

• Parameter changes were done 20.11

• Throughput after changes was improved


Monitoring


Monitoring – Introduction

The basic idea to monitor network is to see how the optimization project is ongoing and how the network is performing

• KPI monitoring• Testing & post processing

• Alarm monitoring

• Schedule monitoring

• Investments checking

• Resource monitoring


Monitoring – Reporting Suite

• Before Reporting Suite can be started, connection to NetActmust be done

• Reporting Suite can be used for KPI monitoring


• Different KPI group can be seen here

• Example of final KPI report

Monitoring – Reporting Suite


Tools to be used


Tools to be used

Example of tools to be used in Solution findingStatistics

(Reporting Suite, Metrica etc.)

Planning tools (NetAct Planner,

Asset etc)

Configuration tools (Plan Editor, RAC tools,

etc)Optimizer

Drive test tools (Nemo Outdoor. TEMS, Actix

etc)

Performance optimization x x xTraffic and Capacity optimization x x xCoverage Optimization x x x xFrequency Optimization x x x x xNeighbor Optimization x x x x xHO Optimization x x x x(E)GPRS Optimization x x x x x

part3_advance network optimization_solution finding

Documents

oldtransaction failures

calltransaction failures

oldabis failures

callabis failures

old channel failure

problems retainability

bts problems

lapd problems