UMTS-Pre-Launch-RF-Optimization-Training-Ivan

PH0+ UMTS Pre-Launch RF Optimization Training 14th May 2008: 

Confidential and Proprietary Information of T-Mobile USA PH0+ UMTS Pre-Launch RF Optimization Training 14th May 2008

Pre-Launch RF Optimization Topics: 

Confidential and Proprietary Information of T-Mobile USA 2 Pre-Launch RF Optimization Topics Pre-launch RF optimization process overview UMTS network integrity validation Drive test validation Swap sector and SC consistency check Single cell coverage analysis Azimuth verification Pilot pollution analysis Neighbor analysis Coverage optimization Access failure and dropped call analysis IRAT handover optimization

Pre-launch RF Optimization Process Overview: 

Confidential and Proprietary Information of T-Mobile USA 3 Pre-launch RF Optimization Process Overview

Pre-launch RF Optimization Process Overview: 

Confidential and Proprietary Information of T-Mobile USA 4 Pre-launch RF Optimization Process Overview Three rounds of RF optimization after spectrum verification and site acceptance completion: Unloaded, Loaded and Market Unloaded cluster optimization focuses on resolving major RF issues Loaded cluster optimization goal is further improving network in terms of quality and capacity in simulated real network conditions Objective is to meet required cluster/market level KPIs

Unloaded/Loaded Cluster Launch KPIs: 

Confidential and Proprietary Information of T-Mobile USA 5 Unloaded/Loaded Cluster Launch KPIs

Market Launch KPIs: 

Confidential and Proprietary Information of T-Mobile USA 6 Market Launch KPIs

Cluster and Late Sites DT Setup: 

Confidential and Proprietary Information of T-Mobile USA 7 Cluster and Late Sites DT Setup

Market DT Setup: 

Confidential and Proprietary Information of T-Mobile USA 8 Market DT Setup

UMTS Network Integrity Validation: 

Confidential and Proprietary Information of T-Mobile USA 9 UMTS Network Integrity Validation UMTS network integrity check includes RNC/RBS alarm, cell availability and T1 errors status inspection UMTS network integrity should be confirmed prior to any drive test activity Post drive integrity check data is valuable input for drive test analysis

Drive Test Preparation Activities: 

Confidential and Proprietary Information of T-Mobile USA 10 Drive Test Preparation Activities Drive test route design and verification UMTS network integrity check Network/route definition data provisioned to drive test teams (Tems cellfile, DT route, DT sequence) IMSI traces (UETR, GPEH) turned on for (selected) test mobiles Correct DT setup and best practices communicated with DT teams

Drive Test Log Files Validation: 

Confidential and Proprietary Information of T-Mobile USA 11 Drive Test Log Files Validation Collected DT log files need to be verified before loaded to Actix for processing DT log files are checked among others for naming, route completion, UE setup and technology mode used, GPS and Scanner integrity, and collected signal levels Use attached TI workspace both for LT1 and LT2 DT setup validation Every DT log file opened in TI and verified Only DT files for completed and verified subcluster drive uploaded to NUSC

Drive Test Log Files Validation 1. Confirm GPS data validity (UMTS/LT1): 

Confidential and Proprietary Information of T-Mobile USA 12 Confirm GPS data validity UMTS categories visible on DT route for valid GPS data Drive Test Log Files Validation 1. Confirm GPS data validity (UMTS/LT1)

Drive Test Log Files Validation 2. Verify UMTS Scanner data validity (UMTS/LT1): 

Confidential and Proprietary Information of T-Mobile USA 13 Verify UMTS Scanner frequency (2037) and signal level; Signal level should be reasonably good next to UMTS site (e.g. -50dBm) and app. 10-15dB higher than the one measured by in-car UEs Drive Test Log Files Validation 2. Verify UMTS Scanner data validity (UMTS/LT1)

Drive Test Log Files Validation 3. Verify GSM Scanner data validity (UMTS/LT1): 

Confidential and Proprietary Information of T-Mobile USA 14 Verify that scanned GSM ARFCNs belong to frequency band used by T-Mobile (593 to 609) Drive Test Log Files Validation 3. Verify GSM Scanner data validity (UMTS/LT1)

Drive Test Log Files Validation 4. Verify CS Short Voice UE (UMTS/LT1): 

Confidential and Proprietary Information of T-Mobile USA 15 Confirm that CS Short UE is connected as MS2; Call duration should be 15s with 10s gap between calls; CS Short UE should not be Idle for a longer period of time; Call setup should be re-attempted after blocked call Drive Test Log Files Validation 4. Verify CS Short Voice UE (UMTS/LT1) Confirm L3 messages and events related to UMTS CS voice mobile Confirm UMTS technology mode and RRC State throughout the call CPICH RSCP data are collected for UE in UMTS mode; Verify MS2 signal level against UMTS scanner

Drive Test Log Files Validation Typical L3 Call Flow for UMTS CS Voice Call Setup: 

Confidential and Proprietary Information of T-Mobile USA 16 Drive Test Log Files Validation Typical L3 Call Flow for UMTS CS Voice Call Setup Verify UL interference level prior to RRC Connection setup Verify CS voice RRC establishment cause Verify SC UE used to initiate call setup Verify if CS voice was locked to UMTS

Drive Test Log Files Validation 5. Verify CS Long Voice UE (UMTS/LT1): 

Confidential and Proprietary Information of T-Mobile USA 17 Confirm that CS Long UE is connected as MS3; Longer Idle periods shouldn’t exist; Call should be re-established after dropped call Drive Test Log Files Validation 5. Verify CS Long Voice UE (UMTS/LT1) Confirm UMTS technology mode and RRC State throughout the call CPICH RSCP data are collected for UE in UMTS mode; Verify MS3 signal level against UMTS scanner Confirm L3 messages and events related to UMTS CS voice mobile

Drive Test Log Files Validation 6. Verify PS R99 UE (UMTS/LT1): 

Confidential and Proprietary Information of T-Mobile USA 18 Confirm that PS UE is connected as MS4; UE should repeatedly download 2MB file from ftp server; Confirm R99 throughput and data sum received at the end of session (2MB); Drive Test Log Files Validation 6. Verify PS R99 UE (UMTS/LT1) Confirm L3 messages and events related to UMTS PS mobile; Check event log for any Session Errors and PDP Context Failures Confirm UMTS technology mode and RRC State throughout the call CPICH RSCP data are collected for UE in UMTS mode; Verify MS4 signal level against UMTS scanner

Drive Test Log Files Validation Typical L3 Call Flow for PS R99 Call Setup: 

Confidential and Proprietary Information of T-Mobile USA 19 Drive Test Log Files Validation Typical L3 Call Flow for PS R99 Call Setup

Drive Test Log Files Validation 7. Verify CS Short Voice UE (GSM/LT2): 

Confidential and Proprietary Information of T-Mobile USA 20 Confirm that GSM CS Short UE is connected as MS1; CS Short UE should not be Idle for a longer period of time; Call setup should be re-attempted after blocked call Drive Test Log Files Validation 7. Verify CS Short Voice UE (GSM/LT2) Confirm L3 messages and events related to GSM CS voice mobile Confirm GSM technology and channel mode throughout the call

Drive Test Log Files Validation 8. Verify CS Long Voice UE (GSM/LT2): 

Confidential and Proprietary Information of T-Mobile USA 21 Confirm that GSM CS Long UE is connected as MS2; Longer Idle periods shouldn’t exist; Call should be re-established after dropped call Drive Test Log Files Validation 8. Verify CS Long Voice UE (GSM/LT2) Confirm L3 messages and events related to GSM CS voice mobile Confirm GSM technology and channel mode throughout the call

Drive Test Log Files Validation 9. Verify CS Idle UE (GSM/LT2): 

Confidential and Proprietary Information of T-Mobile USA 22 Drive Test Log Files Validation 9. Verify CS Idle UE (GSM/LT2) Confirm L3 messages related to Idle mode Confirm UE is in Idle (either GSM or UMTS) mode throughout the call

Drive Test Log Files Validation 10. Verify DT Log File Name: 

Confidential and Proprietary Information of T-Mobile USA 23 Drive Test Log Files Validation 10. Verify DT Log File Name

DT Route Completion Verification: 

Confidential and Proprietary Information of T-Mobile USA 24 DT Route Completion Verification In order to verify route completion DT log files are exported in MapInfo format and compared against route definition Use attached MapInfo export setup files for LT1 (UMTS) and LT2 (GSM) log files Check DT diary for any comments (e.g. explanation for section of DT route skipped due to road works)

DT Route Completion Verification cont.: 

Confidential and Proprietary Information of T-Mobile USA 25 DT Route Completion Verification cont. Export DT logs in MapInfo format to verify route completion

DT Route Completion Verification cont.: 

Confidential and Proprietary Information of T-Mobile USA 26 DT Route Completion Verification cont.

DT Analysis Overview: 

Confidential and Proprietary Information of T-Mobile USA 27 DT Analysis Overview

Swap Sector and SC Consistency Check: 

Confidential and Proprietary Information of T-Mobile USA 28 Swap Sector and SC Consistency Check Identify swapped sectors and improper SC data fill using Scanner Best Server SC plot (CPICH_Scan_SC_SortedbyEcIo_0) Use Cell Color property based on SC; Turn on Scanner Best Server SC labels; Always use Scanner plot since UE could be impacted by a poor neighbor List

Swap Sector and SC Consistency Check: 

Confidential and Proprietary Information of T-Mobile USA 29 Swap Sector and SC Consistency Check Swapped sectors example UBQ04388A21 swapped with UBQ04388A31

Swap Sector and SC Consistency Check: 

Confidential and Proprietary Information of T-Mobile USA 30 Swap Sector and SC Consistency Check Scanner ‘Where Seen’ coverage plot used in ambiguous situations

Swap Sector and SC Consistency Check: 

Confidential and Proprietary Information of T-Mobile USA 31 Swap Sector and SC Consistency Check Wrong antenna direction sometimes incorrectly interpreted as swapped sector Observe impact of near field obstructions on cell coverage UBQ06088I11 azimuth confirmed 80 instead of 30; High buildings block coverage north bound

Single Cell Coverage Analysis: 

Confidential and Proprietary Information of T-Mobile USA 32 Single Cell Coverage Analysis Used for isolating overshooting, coverage and wrong antenna direction problems Scanner ‘Where Seen’ coverage plot utilized to determine cell footprint Change Scanner Best Server symbol size to minimum (1) and turn on SC labels to determine best server serving zone against ‘where seen’ plot; Overshooting cell coverage exceeds beyond the 1 st and in some cases even 2 nd and 3 rd tier cells; Any tilt or azimuth change designed to limit pilot spillover should not jeopardize best server coverage.

Single Cell Coverage Analysis: 

Confidential and Proprietary Information of T-Mobile USA 33 Single Cell Coverage Analysis Checking ‘Where Seen’ coverage plot for each and every cluster cell can be time consuming Potential overshooters can be drilled down using number of cell coverage samples in Cell Coverage Tab of the Radio Network Explorer Window Cell coverage is quantified with number of samples instead of bins which sometimes can be misleading

Single Cell Coverage Analysis: 

Confidential and Proprietary Information of T-Mobile USA 34 Single Cell Coverage Analysis Overshooters (boomers) greatly contribute to downlink interference, increase SHO overhead and packet sharing and are susceptible to uplink interference which reduces cell capacity Poor coverage identified relatively close to the site can be caused by wrong antenna azimuth implementation, improper EDT/MTD settings or implementation, near field obstructions, Node B HW issues or feeder/connector issues Co-sector GSM data can be used to validate UMTS cell coverage If reason for poor cell coverage cannot be determined FOPS site verification requested

Azimuth verification: 

Confidential and Proprietary Information of T-Mobile USA 35 Azimuth verification Analysis done in parallel with single cell coverage verification Scanner ‘Where Seen’ coverage plot utilized to assess cell azimuth against RF design Potential antenna direction problems can be drilled down using percentage of coverage samples beyond nominal cell beamwidth Cells should be filtered for minimum number of coverage samples (e.g. 5000) before sorting table per ‘%>Beam’ column; Cell coverage is quantified with number of samples instead of bins which sometimes can be misleading

Azimuth verification: 

Confidential and Proprietary Information of T-Mobile USA 36 Azimuth verification Co-sector GSM data can be used to validate UMTS cell azimuth FOPS site verification requested if wrong antenna direction suspected UBQ04956A31 azimuth confirmed 315 instead of 270

Pilot Pollution Analysis: 

Confidential and Proprietary Information of T-Mobile USA 37 Pilot Pollution Analysis Identify areas with pilot pollution and improve overall Ec/No Area suffer from pilot pollution when more than 3 pilots are measured within 5dB of strongest one in acceptable coverage conditions Spotlight ‘Cell Pilot Pollution’ analysis based on all collected data samples proven to be ineffective to identify pilot pollution problems

Pilot Pollution Analysis: 

Confidential and Proprietary Information of T-Mobile USA 38 Pilot Pollution Analysis Initial Tuning Macro used as an alternative to quantify pilot pollution problems ITM is Excel tool based on binned Scanner data Small bin size (5x5m) recommended for dense urban area while medium bin size (10x10m) is applicable for other Two output sheets generated per ITM Polluter analysis – detailed and condensed one Detailed ITM polluter output sheet have listed data for every polluted bin, including outbound and inbound Cell Id, EcNo, RSCP, neighbor definition falg and distance to bin Condensed ITM polluter output sheet contains information aggregated per outbound polluter cell

Macro User Interface: 

Confidential and Proprietary Information of T-Mobile USA 39 Macro User Interface User can set EcNo, EcNo delta and RSCP thresholds used in initial tuning analysis Polluter and Neighbor analysis are run separately Displayed ITM threshold values recommended for unloaded tuning drive

Pilot Pollution Analysis: 

Confidential and Proprietary Information of T-Mobile USA 40 Pilot Pollution Analysis Detailed ITM polluter output sheet Condensed ITM polluter output sheet ITM polluter output displayed on map

Pilot Pollution Analysis: 

Confidential and Proprietary Information of T-Mobile USA 41 Pilot Pollution Analysis Major polluters (cells with highest number of outbound polluted bins) should be thoroughly checked In addition areas with concentrated polluted bins should be examined to improve signal dominance and overall EcNo Affected areas should be checked for UE EcNo to determine severity of pilot pollution Typically 3-5dB interferer signal reduction would resolve pilot pollution issues, while boomer cells may require further reduction if feasible Polluter signal level should be incpected both in interferer and best server zones and compared with levels measured for other cells

Pilot Pollution Analysis: 

Confidential and Proprietary Information of T-Mobile USA 42 Pilot Pollution Analysis Tilt or azimuth changes should be carefully balanced to reduce pollution and maintain acceptable signal level at the same time Outbound polluter best server zone circled with green line – RSCP better than -70dBm in compact best server zone; Polluted bin areas marked with blue circles – note that not all of spillover bins are identified with pilot pollution

Pilot Pollution Analysis: 

Confidential and Proprietary Information of T-Mobile USA 43 Pilot Pollution Analysis Check terrain profile, height difference, distance between Tx antenna and polluted area, antenna type and current tilt implemented to estimate tilt change needed; If needed use Asset to confirm all changes

Pilot Pollution Analysis: 

Confidential and Proprietary Information of T-Mobile USA 44 Pilot Pollution Analysis Check terrain profile, height difference and distance between Tx antenna and polluted area to estimate tilt change needed Inclination angle between Tx antenna and polluted area Effective vertical plane antenna attenuation angle

Pilot Pollution Analysis: 

Confidential and Proprietary Information of T-Mobile USA 45 Pilot Pollution Analysis UBQ04618B31 ‘Best Server’ Scanner plot, drive 01 Although not best server along Grand Central Pkwy in circled area UBQ04006A31 would provide excellent coverage if UBQ04618B31 coverage was reduced UBQ04006A31 ‘Where Seen’ Scanner plot, drive 01 Best server cell is not necessarily preferred/needed in certain area if neighbor signal levels are acceptable

Pilot Pollution Analysis: 

Confidential and Proprietary Information of T-Mobile USA 46 Pilot Pollution Analysis UBQ04618B31 ‘Where Seen’ Scanner plot, drive 01, tilt as per design 0+6 UBQ04618B31 ‘Best Server’ Scanner plot, drive 01, tilt as per design 0+6 UBQ04618B31 ‘Where Seen’ Scanner plot, drive 02 after tilt change from 0+6 to 0+7 UBQ04618B31 ‘Where Seen’ Scanner plot, drive 03 after tilt change from 0+7 to 0+8 In some cases several itterations of tilt changes needed to fully optimize cell footprint; Tilt change execution can be costly when MDT is needed or remote EDT is not feasible – in such cases 2dB considered as a minimum attenuation change that validates tilt alteration

Neighbor Analysis: 

Confidential and Proprietary Information of T-Mobile USA 47 Neighbor Analysis Identify missing UMTS neighbors Missing neighbors one of the major reasons of dropped calls in early network stages due to connection release mechanism designed to avoid excessive UL interference Spotlight ‘3G Missing Neighbors’ analysis based on all collected data samples has shown issues with matching sample SC with Cell Id

Neighbor Analysis: 

Confidential and Proprietary Information of T-Mobile USA 48 Neighbor Analysis Initial Tuning Macro used as an alternative to identify missing neighbors Two output sheets generated per ITM Neighbor analysis – detailed and condensed one Detailed ITM neighbor output sheet have listed data for every missing neighbor bin, including outbound and inbound Cell Id, EcNo, RSCP and distance between cells Condensed ITM neighbor output sheet contains information aggregated per missing neighbor relation

Neighbor Analysis: 

Confidential and Proprietary Information of T-Mobile USA 49 Neighbor Analysis Detailed ITM neighbor output sheet Condensed ITM neighbor output sheet

Neighbor Analysis: 

Confidential and Proprietary Information of T-Mobile USA 50 Neighbor Analysis Missing neighbor relations detected within highest number of bins should be thoroughly checked In cases where neighbor relation is missing between faraway cells containing overshooting cell(s) should be considered as an alternative Check for maximum allowed number of UMTS neighbors should be carried out before neighbor additions are submitted Boomer cells tend to have high number of defined neighbors so keeping optimal neighbor list is essential

Coverage Optimization: 

Confidential and Proprietary Information of T-Mobile USA 51 Coverage Optimization Poor DL coverage identified using Scanner Best Server SC plot (<-105dBm) Scanner DL signal level should be compared with the RSCP prediction from the RF design – wherever inferior to the prediction further analysis is required Scanner’s RSCP Coverage Asset RSCP Prediction Poor coverage measured north of UBQ06088I site inferior to the prediction; UBQ06088I11 azimuth confirmed 80 instead of 30 with high buildings blocking coverage north bound

Coverage Optimization: 

Confidential and Proprietary Information of T-Mobile USA 52 Coverage Optimization Main causes for poor coverage can be terrain, obstructions, azimuth settings, EDT/MDT settings, high feeder loss, CPICH output power or HW issues While improving coverage care should be taken not to increase pilot pollution If reason for poor cell coverage cannot be determined FOPS site verification requested Scanner RSCP Coverage Azimuth 260 Scanner RSCP Coverage Azimuth 290 UBQ04870C31 azimuth changed from 260 to 290 improved signal level within the area but didn’t entirely resolve the problem

Coverage Optimization: 

Confidential and Proprietary Information of T-Mobile USA 53 Coverage Optimization Google Earth and Live Maps used as additional source of mapping information

Coverage Optimization: 

Confidential and Proprietary Information of T-Mobile USA 54 Coverage Optimization Poor UL coverage normally corresponds to high UE Tx Power Main objective of checking the UE Tx Power is to verify the Path Balance in areas with acceptable DL RSCP and high UE Tx Power UL coverage issues can be caused by TMA, feeder, antenna or Node B HW issues, improper UL power control parameters, improper cell (re)selection parameters, improper Node B parameters (ulAttenuation, dlAttenuation, TMA insertion loss, TMA Gain, etc) or external UL interference High RTWP received at Node B could indicate HW issues or UL interference

PowerPoint Presentation: 

Confidential and Proprietary Information of T-Mobile USA 55 Access Failure and Call Drop Analysis Overview

Access Failure Analysis: 

Confidential and Proprietary Information of T-Mobile USA 56 Access Failure Analysis Three essential procedures that need to be completed before call setup is deemed to be successful: RACH Access, RRC Connection Setup and RAB Setup procedures Signalling connection establishment: RRC connection setup monitored based on N300 (5) and T300 (2s) parameters; Reasons for setup failure could be PRACH preambules not detected or detected but negatively acknowledged, ‘RRC Connection Request’ unsuccessfully detected by the Node B or ‘RRC Connection Setup’ unsuccessfully detected by the UE CS call setup considered successful when ‘Alerting/Connect’ message is received, while for PS call when ‘Activate PDP Context Accept’ message is received

Access Failure Analysis: 

Confidential and Proprietary Information of T-Mobile USA 57 Access Failure Analysis If ‘RRC Connection Request’ not sent on optimal serving cell check neighbor definitions and cell reselection parameters Typical reasons for access failures are coverage issues, cell reselection issues, missing neighbors, pilot pollution issues, power balance issues, HW issues, external interference issues, capacity issues, core network issues, synchronization issues, UE issues, logging issues, processing issues..

Access Failure Analysis: 

Confidential and Proprietary Information of T-Mobile USA 58 Access Failure Analysis Poor in-car radio conditions in Astoria park area. UE didn’t didn’t receive respond on several ‘RRC Connection Request’ attempts although transmitting with maximum Tx power Increased RTWP at Node B; If consistently reported, Node B should be checked for UL interference and HW issues Access Failure Example: Poor radio conditions / High UL RTWP

Access Failure Analysis: 

Confidential and Proprietary Information of T-Mobile USA 59 Access Failure Analysis Call setup started on on non-optimal serving cell UBQ04198C21 next to UBQ04947A site due to slow cell reselection. UE couldn't receive ASU due to poor EcNo in downlink. Check signal dominance and cell reselection parameters within the area. Access Failure Example: Cell reselection issues

Access Failure Analysis: 

Confidential and Proprietary Information of T-Mobile USA 60 Access Failure Analysis Lack of dominant server and fast changes of radio conditions in Broadway St area. EcNo deteriorated severely after UBQ06078B21 SC 321 remained the only cell in the AS. Check signal dominance, pilot pollution and spillovers within the area. Add missing neighbor between UBQ06078B21 SC 321 and UBQ06079A11 SC 337. Access Failure Example: Lack of signal dominance / Sudden drop

Access Failure Analysis: 

Confidential and Proprietary Information of T-Mobile USA 61 Access Failure Analysis Call Release received by CS Core network within excellent radio conditions. Escalate observed issues if repeatedly reported. Access Failure Example: Core issues (MSC)

Access Failure Analysis: 

Confidential and Proprietary Information of T-Mobile USA 62 Access Failure Analysis Several consecutive PDP Context Rejects logged due to insufficient resources. Escalate observed issues if repeatedly reported. Access Failure Example: Core issues (SGSN)

Access Failure Analysis: 

Confidential and Proprietary Information of T-Mobile USA 63 Access Failure Analysis Normal call setup falsely pegged by Actix due to delayed Radio Bearer Setup Complete response from the UE (10s comparing to normal response time of 20-30ms). Uu_wait_timer_Complete should be set to 0 to disable monitoring of radio bearer setup completion in Actix. Access Failure Example: UE issues / Actix processing issues

Access Failure Analysis: 

Confidential and Proprietary Information of T-Mobile USA 64 Access Failure Analysis Setup failure falsely pegged by Actix due to missing Alerting message. Access Failure Example: Tems logging issues (non-genuine failure)

Access Failure Analysis: 

Confidential and Proprietary Information of T-Mobile USA 65 Access Failure Analysis Call normally cleared before call setup was completed at log file swapping. Access Failure Example: Drive test logging issues (non-genuine failure)

Call Drop Analysis: 

Confidential and Proprietary Information of T-Mobile USA 66 Call Drop Analysis Similar to access failures, typical reasons for dropped calls are coverage issues, cell reselection issues, missing neighbors, pilot pollution issues, power balance issues, inter RNC handover issues, HW issues, external interference issues, capacity issues, core network issues, synchronization issues, UE issues, logging issues, processing issues..

Call Drop Analysis: 

Confidential and Proprietary Information of T-Mobile USA 67 Call Drop Analysis Call released after conn releaseConnOffset criterion was met due to missing neighbor UBQ04199A11-UBQ04008C31. Add missing neighbors. Call Drop Example: Missing neighbor

Call Drop Analysis: 

Confidential and Proprietary Information of T-Mobile USA 68 Call Drop Analysis Poor coverage area north of I-495 and west of 5th St. UBQ04022B31 cannot get through due to terrain. Check possibilities to improve coverage within the area. Call Drop Example: Poor coverage

Call Drop Analysis: 

Confidential and Proprietary Information of T-Mobile USA 69 Call Drop Analysis Call Drop Example: Pilot spillover / Missing neighbor UBQ06087B21 SC 374 overshooting and missing neighbors in in large area between UBQ04003B and UBQ04006A. Reduce pilot spillover and add missing neighbors.

Call Drop Analysis: 

Confidential and Proprietary Information of T-Mobile USA 70 Call Drop Analysis Call Drop Example: Fast change of radio conditions / Sudden drop UBQ04848B21 signal level suddenly dropped due to shadowing; UE couldn't update ASU due to bad quality in downlink.

Call Drop Analysis: 

Confidential and Proprietary Information of T-Mobile USA 71 Call Drop Analysis UE received Release in downlink with 'Abnormal network' cause within excellent radio conditions next to UBQ04198C site. Serving cell was reported with alarms and outages. Call Drop Example: HW issues

Call Drop Analysis: 

Confidential and Proprietary Information of T-Mobile USA 72 Call Drop Analysis Faulty UE lost synchronization with UTRAN several time in a row while all other UEs were reporting steady good EcNo Call Drop Example: UE issues

Call Drop Analysis: 

Confidential and Proprietary Information of T-Mobile USA 73 Call Drop Analysis RNC4 cell couldn’t add RNC1 neighbor cell UNY01184B21 to the AS in RNC4 serving area because of wrong external cell definition (UNY01184B21 external SC definition in RNC4 was set to 125 instead of 133. Call Drop Example: Data fill issues

IRAT Handover Optimization Preparation: 

Confidential and Proprietary Information of T-Mobile USA 74 IRAT Handover Optimization Preparation Missing IRAT neighbors are one of the major causes of 3G-2G handover failures so thorough check of IRAT neighbor definitions is recommended Consistency of IRAT related UTRAN parameters (IRAT handover support parameters, thresholds, hystereses, timers) should be checked UMTS network need to be well tuned otherwise poor Ec/No would lead to frequent 3G-2G handovers, long time spent in Compressed mode, and/or 3G-2G handovers prevented by sudden drops on UMTS

IRAT Handover Optimization Common Problems: Missing Neighbors: 

Confidential and Proprietary Information of T-Mobile USA 75 IRAT Handover Optimization Common Problems: Missing Neighbors Missing IRAT neighbors problem particularily affects areas lacking UMTS signal dominance so UMTS pilot spillover should be minimized GSM cells located at the end of UMTS network coverage usually require 2nd tier UMTS cells defined as neighbors Balanced approach needed since long IRAT neighbor lists reduce Compressed mode measurement accuracy and increase probability for targeting non-optimal neighbor cell Prioritization of IRAT neighbors based on STS data and drive tests is highly recommended to avoid neighbor truncation

IRAT Handover Optimization Common Problems: Missing Neighbors: 

Confidential and Proprietary Information of T-Mobile USA 76 IRAT Handover Optimization Common Problems: Missing Neighbors In example shown non-optimal GSM cell IL02503 instead IL02453 was targeted due to missing IRAT neighbors – handover attempt failed due to inability to synchronize to GSM.

IRAT Handover Optimization Common Problems: IRAT Neighbor List Truncation: 

Confidential and Proprietary Information of T-Mobile USA 77 IRAT Handover Optimization Common Problems: IRAT Neighbor List Truncation IRAT neighbors get truncated if combined number of unique neighbors for cells included in Active set exceeds 32 Same as for missing neighbor problem, IRAT neighbor list truncation mainly affects areas lacking UMTS signal dominance Handover attempt will fail even if IRAT neighbor gets truncated after e3a is sent – UTRAN doesn’t have the mechanism to keep targeted GSM cell from being truncated Prioritization of IRAT neighbors based on STS data and drive tests is essential for overcoming the problem

IRAT Handover Optimization Common Problems: IRAT Neighbor List Truncation: 

Confidential and Proprietary Information of T-Mobile USA 78 IRAT Handover Optimization Common Problems: IRAT Neighbor List Truncation In example shown handover attempt failed due to truncation – e3a reported handover target cell IL15428 (129/20) got truncated from Measurement Control list and replaced with 129/22 after active set was updated with two additional cells.

IRAT Handover Optimization Common Problems: Wrong IRAT Parameter Settings: 

Confidential and Proprietary Information of T-Mobile USA 79 IRAT Handover Optimization Common Problems: Wrong IRAT Parameter Settings Compressed mode thresholds highly affect IRAT handover performance – set to high could lead to frequent 3G-2G handovers, decreased 3G traffic level and weaken HSDPA performance, while set to low could increase 3G DCR and make IRAT neighbor list hard to maintain Separate sets of e2d thresholds introduced for ‘core’ and ‘fringe’ cells with increased levels for the latter should provide balanced approach however fine tuning of thresholds in certain cases is necessary All other IRAT related parameters should be set consistently to facilitate smooth 3G-2G transition where is needed

IRAT Handover Optimization Common Problems: Wrong IRAT Parameter Settings: 

Confidential and Proprietary Information of T-Mobile USA 80 IRAT Handover Optimization Common Problems: Wrong IRAT Parameter Settings hoType parameter need to be set carefully in IF network border areas – set to IFHO_PREFERRED even for one of the cells included in Active set it prevents IRAT handovers which is a problem if no suitable IF handover target exists within the area

IRAT Handover Optimization Common Problems: BSIC Decoding Issues: 

Confidential and Proprietary Information of T-Mobile USA 81 IRAT Handover Optimization Common Problems: BSIC Decoding Issues Non-optimal GSM cell may be targeted if UE failed to decode BSIC of all measured cells. BSIC decoding issues can be caused by too long IRAT neighbor list, poor GSM radio conditions or insufficient time UE spent in Compressed mode (as in example shown). Keeping IRAT neighbor lists at optimal length and prioritized should minimize BSIC decoding issues.

IRAT Handover Optimization Common Problems: SI Decoding Issues: 

Confidential and Proprietary Information of T-Mobile USA 82 IRAT Handover Optimization Common Problems: SI Decoding Issues PS mobile is obliged to decode set of GSM System Information messages before sending LA Updating Request. Time available for completing handover procedure is limited by T309 (8s by default). SI decoding issues can be caused by poor GSM radio conditions or UE issues.

IRAT Handover Optimization Common Problems: Poor UMTS Radio Conditions: 

Confidential and Proprietary Information of T-Mobile USA 83 IRAT Handover Optimization Common Problems: Poor UMTS Radio Conditions Poor UMTS radio conditions may prevent UE to enter Compressed mode or start measuring GSM frequencies due to inability to decode Physical Channel Reconfiguration or IRAT Measurement Control messages. In cases when UMTS radio signal drops suddenly (e.g. tunnels) connection may be dropped even before UE reported e2d which requires fine tuning of IRAT thresholds and/or channel switching parameters as an interim solution. Long term solution is improving UMTS coverage within the area.

IRAT Handover Optimization Common Problems: Physical Channel Failure: 

Confidential and Proprietary Information of T-Mobile USA 84 IRAT Handover Optimization Common Problems: Physical Channel Failure Handover attempts failed due to Physical Channel Failure and not caused by any of previously described problems are caused by UE inability to access GSM target cell due to poor GSM signal coverage/quality, wrong BCCH/BSIC definition in UMTS or any other reason. Physical channel failure may happen in quite few cases with no plausable explanation, when subsequent handover command succeeds on the very same target cell within couple of seconds (see example below).

IRAT Handover Optimization Flowchart: 

Confidential and Proprietary Information of T-Mobile USA 85 IRAT Handover Optimization Flowchart 1 5 6

IRAT Troubleshooting Flowchart: 

Confidential and Proprietary Information of T-Mobile USA 86 IRAT Troubleshooting Flowchart 7 8 9 10

IRAT Handover Optimization Steps: 

Confidential and Proprietary Information of T-Mobile USA 87 IRAT Handover Optimization Steps Check if UE sent e2d measurement report 1 In case of missing e2d measurement report check UMTS radio conditions and determine if Compressed mode thresholds have been set correctly

IRAT Troubleshooting Flowchart Details: 

Confidential and Proprietary Information of T-Mobile USA 88 Search for IRAT Measurement Control messages backwards to resolve BCCH and BSIC of cells included in cellToReportList IRAT Troubleshooting Flowchart Details 7 Latest definition of reported Measurement Control list position should be located. In example shown cellToReportList cell IL15428 (129/20) was defined at position 17 in IRAT Measurement Control list. Actix search function used

IRAT Troubleshooting Flowchart Details: 

Confidential and Proprietary Information of T-Mobile USA 89 Search for IRAT Measurement Control messages forward to determine any change of ‘interRAT CellId’ due to truncation or UMTS neighbor removal IRAT Troubleshooting Flowchart Details 8 Actix search function used In example shown cellToReportList cell IL15428 (129/20) got truncated from Measurement Control list and replaced with 129/22 after active set was updated with two additional cells. Handover attempted on wrong target cell failed due to Physical Channel Failure.

IRAT Troubleshooting Flowchart Details: 

Confidential and Proprietary Information of T-Mobile USA 90 Search for IRAT Measurement Control messages forward to determine any change of ‘interRAT CellId’ due to truncation or UMTS neighbor removal IRAT Troubleshooting Flowchart Details 8 Another possible reason for targeted ‘interRAT CellId’ change is removal of UMTS neighbor from the Active set. In example shown targeted ‘interRAT CellId’ 1 (169/16) was replaced with (568/05) after UMTS neighbor counterpart ILU01767 (SC 30) was removed from the Active set. Handover attempted on wrong target cell failed due to Physical Channel Failure.

IRAT Troubleshooting Flowchart Details: 

Confidential and Proprietary Information of T-Mobile USA 91 Confirm BCCH/BSIC of targeted GSM cell from Handover command; Check targeted GSM cell location and identify any missing neighbors IRAT Troubleshooting Flowchart Details 9 BCCH/BSIC of targeted GSM cell should match cell reported in e3a, otherwise targeted ‘interRAT CellId’ has been changed either due to truncation or removed UMTS neighbor. In example shown 3G-2G handover was attempted at optimal 2G handover target cell IL01232 (146/67).

IRAT Troubleshooting Flowchart Details: 

Confidential and Proprietary Information of T-Mobile USA 92 In case of PS handover attempt check if all System Information messages are decoded IRAT Troubleshooting Flowchart Details 10 PS mobile is obliged to decode set of GSM System Information messages (Type 1, Type 2, Type 2ter, Type 3, Type 4 and Type 13) before initiate LA Update. SI decoding issues can be caused by poor GSM radio conditions or UE issues. In example shown UE failed to decode SI Type 13 before T309 expiry.

PowerPoint Presentation: 

Confidential and Proprietary Information of T-Mobile USA 93