Drive Testing Methodology For Planning, Q.A Troubleshooting & Optimizati Optimization on
Typical Engineering Groups and Activities Marketing
Customer Care
Engineering
RF Design & Planning
OMC/NMC
O&M
Optimization
Quality Assurance
Switching Operations
Site Planning
Faults Management
BTS Maintenance
Statistics Analysi An alysis
Performance Verification Verification
Maintenance
Core Design
Statitics Generation
Air Interface Troubleshooting
RF Tests
Benchmarking
Planning
RF Planning
Databse Management
Implementing Changes
RF and Parametric P arametric Tuning
Transmission
Value Added Services
Typical Engineering Groups and Activities Marketing
Customer Care
Engineering
RF Design & Planning
OMC/NMC
O&M
Optimization
Quality Assurance
Switching Operations
Site Planning
Faults Management
BTS Maintenance
Statistics Analysi An alysis
Performance Verification Verification
Maintenance
Core Design
Statitics Generation
Air Interface Troubleshooting
RF Tests
Benchmarking
Planning
RF Planning
Databse Management
Implementing Changes
RF and Parametric P arametric Tuning
Transmission
Value Added Services
RF Planning and Design Switching
Optimization
Marketing Financial Controller Project Management
RF Planning Switch Planning
& Design RF Coverage Requirements Capacity Coverage Requirements RF Penentration Penentration Requirements
RF Planning and Design O&M
Optimization
Marketing
RF Planning & Design
Site Planning
Cell Planning
Frequency Planning
RF Planning and Design – Site Planning
Reject Acquire Action Steps
Test Transmission
Search Area Selection
Site Planning
Band Clearance
Site Physical Qualification
Coverage Prediction
RF Design and Planning – Cell Planning Antenna Parameters -Height, Tilts, Omni/Sector, Azimuth, Gain, Polarization etc.
Cell Parameters -Power Settings -Neighbor Planning* -Handover Parameters*
*These are required to balance traffic loading and maintain a good QoS on cell edges
Test Transmission
-Test Transmitter -High Sensitivity CW Receiver -Time and Distance based Averaging -Lee’s Criteria – AT LEAST 50 samples of RF with a Running Average over a distance of 40 Wavelengths (12 meters for GSM 900)
RF Planning and Design – Frequency Planning
GSM uses concept of cells One cell covers small part of network Network has many cells Frequency used in one cell can be used in another cells Clusters This is known as Frequency Re-use
F= 1,2,3,4,5,6,7,8,9,10
F=2 F=3
F=7 F4
F2
F2
F3
F1
F1
F4
F2 F3
F=1 F=4,8
F=6,10
F2
F=5,9
F=2
F1
F=3
F=7 F=1 F=5,9
F=3
F=7 F=4,8
F=6,10
Co-Channel ( Re-use ) Cells
F=2 F=1 F=4,8
F=6,10 F=5,9
Interference
Interference in GSM systems are classified into three major categories .
Co-Channel Interference Adjacent Channel Interference External Interference
Co - Channel interference
Interference on a channel caused by another cell/mobile using the same frequency. C/Ic is the measure of co-channel interference GSM specifies the C/Ic threshold of 9dB for a service quality of 0.4% BER on Type II bits. 9db also includes 2db implementation margin 9db is decided considering the implementation of SFH Without SFH, the preferred threshold is 12 dB.
Ic
C
C / Ic 9 db
Co-Channel Interference Noise
C
ARFCN " N"
Ic
ARFCN " N"
Causes
Distant Cells due to tight frequency re-use patterns. Distant Cells due to errors in frequency planning. Mulitpath from Distant cells( strong reflector, Water). C/Ic will degrade the Ec/No, so if Noise floor itself is high, then even a high value of C/Ic can deteriorate quality.
Adjacent Channel Interference Interference caused when wanted and unwanted GSM RF channels co-exist.
Ia C
GSM receivers are designed for an Adjacent Channel Suppression of minimum 18db at an offset of 200 Khz, 50db at 400 Khz and 58db at 600 Khz.
Adjacent Channel Interference
ACS = 18db & C/c = 9db This means if Ia is 9db above C, then with 18db ACS, it equals C/Ic.
Thresholds
C/ Ia1 = - 9 db C/ Ia2 = - 41 db C/ Ia3 = - 49 db 49 db 41 db 9db
N-3
N-2
N-1
N
N+1
N+2
N-3
Adjacent Channel Interference Causes
Adjacent ARFCN's in same cells Adjacent ARFCN's in adjacent cells Distant Cells due to tight frequency re-use patterns. Distant Cells due to errors in frequency planning. Mulitpath from Distant cells( strong reflector, Water). Improper Receiver filters ( low ACS ) C/Ia will degrade the Ec/No, so if Noise floor itself is high, then even a low value of C/Ia can deteriorate quality.
External Interference
Interference coming on a GSM signal from an undesired source, i.e neither a co/adj channel cell or MS.
Sources
Malfunctioning or Maladjusted Transmitters
Paging, broadcast, etc. Intermodulation Products
Base station malfunction, rogue mobile
Strong signals in adjacent channels
Harmonics from Other Bands
CDMA
GSM Interference UL
UL 824 MHz
880 890 MHz
849 MHz 869 MHz
915 MHz
894 MHz
925 935 MHz
DL
960 MHz
UL
•CDMA Downlink interfering with GSM Uplink Minimal loss
CDMA
60 dbc
GSM
•OMC Stats indicates High Cell Access, Failed Cell Acess,Phantom RACH’s •Drive Test indicates Blocked calls with return to idle after Channel Request •Digital Receiver can go upto –122 dbm noise floor level for this application •Agilent Receiver becomes a Hero in China for detecting this problems in live networks
Quality Assurance Field Tests (Drive Tests)
Customer Care
OMC/NMC
Quality Assurance
Optimization
•Quality Assurance takes data from several sources •Primary sources of Data are OMC/NMC and Field Tests
Quality Assurance •Consistent Network Health Monitoring •Authentic Data Points to measure against KPI thresholds •Quality Trends by Regions and by Vendors •Integration of Data from prominent sources like OMC, Customer Care, Field Tests etc to generate Service Availability and Performance Index figures •KPI Parameters could be split collected from different data sources •Most KPI Parameters need customer perception ,hence field measurements are essential •Competitive Networks Benchmarking •Provide Results to Marketing, Business Analysts and Optimization
Network Performance Data Sources Customer Calls
•Customer perception •Repeatability •Non-Technical Info •Phsyco Factor
OMC/NMC
•Massive Data •More Statistical Data •Cell level analysis •Non Real Time update •Non Geographical info •Specific Mobile Tracing •Performance for All users
Drive Test
•Specific to problem route •Limited users (1..4..8) tests •Air interface only •Drill Down to Causes •Spot Analysis •Coercive Testing •Optimization Tests
Quality Assurance - Period Routine 30% 25% 20% 15% 10% 5%
Spurious
0% D aily
We ekly
M onthly
Quarte rly
Half ye arly
Annual
100% 80% 60% 40% 20% 0% Major Technical Changes
Market Events
Quality Assurance Methodology Step A : Deciding the monitoring geography
Network(Market) Region/Circles/States City’s
Town’s
Villages
Connecting Hws/Rds
Zones
Zones
Groups
Highways
Hot Spots Routes(Rds). Routes(Strs)
Bye-Lanes
Roads/Streets
Performance Monitoring Measurements Voice Statistical Call Success Rate Call Drop Rate Handover Success Rate No Service Percentage Quality Percentage Coverage Percentage Interference Geographical(Maps) Speech Quality(MOS) Um Quality(Rxqual) Coverage(Rxlev) Cell Footprint(Cellid) Drop Calls Blocked Calls
Q.A Drive Process Suggestion -Routes should be predefined -Test plans should be preset -Drive Duration and Time of Day should be preplanned - Peak Traffic Hours should be used for QA tests -Markers and Notes should be used -Data should be preferably binned -Use Analysis Reporter to get quick shot QA performance Report -Thresholds should be standardized
QA Drive Test Call Setup Short Calls -Reliable CSR -Non-Reliable Drop Long Calls - Non-Reliable CSR - Reliable Drop •Average User Call time should be taken ( 2mins : 15 secs off) •CSR is more reliable on cumulative traffic basis, hence focus should be more on Drop calls. •Recommended to do Quality Drive separately or use two phones and then use combined statistics generation
QA Drive Basic Setup Single Phone Call Duration : 120 secs Idle Time : 15 secs Immediate Dial : ON
Digital Receiver Cochannel Adjacent Chan A Link to BCH
* Do NOT dial a number , which does NOT issue Alerting Alarms and Markers Blocked Call Drop Call RLTC < 5 Rxlev < - 100 for 3 secs RxQual > 4 for 3 secs Handover Failure Assignment Failure BCH Change Cochannel C/I < 9 & Power > -90 Adjacent C/I > -9 & Power > - 90
-Alarm Count provides severity points -Helps the Post QA Action team
QA Drive Basic Setup Two Phone Phone 1
Phone 2
Digital Receiver
Call Duration : 60 secs Idle Time : 15 secs Immediate Dial : ON
Call Duration : Continous Idle Time : 15 secs Immediate Dial ON
Cochannel Adjacent Chan A Link to BCH of Phone 2
* Do NOT dial a number , which does NOT issue Alerting Alarms and Markers (P1) - Blocked Call (P2) - Drop Call (P2) - RLTC < 5 (P2) - Rxlev < - 100 for 3 secs (P2) - RxQual > 4 for 3 secs (P2) - Handover Failure (P1)- Assignment Failure (P1 & P2) - BCH Change Cochannel C/I < 9 & Power > -90 Adjacent C/I > -9 & Power > - 90
-Alarm Count provides severity points -Helps the Post QA Action team
QA Drive Basic Setup Three Phone Phone 1
Phone 2
Phone 3
Digital Receiver
Call Duration : 60 secs Idle Time : 15 secs Immediate Dial : ON
Call Duration : Continous Idle Time : 15 secs Immediate Dial ON
No call Idle
Cochannel Adjacent Chan A Link to BCH of Idle
* Do NOT dial a number , which does NOT issue Alerting Alarms and Markers (P1) - Blocked Call (P2) - Drop Call (P1 & P2) - RLTC < 5 (P2) - Rxlev < - 100 for 3 secs (P2) - RxQual > 4 for 3 secs (P2) - Handover Failure (P1)- Assignment Failure (P1 & P2 & P3) - BCH Change Cochannel C/I < 9 & Power > -90 Adjacent C/I > -9 & Power > - 90
-Alarm Count provides severity points -Helps the Post QA Action team
QA Test Setup Matrix QA Test
Phone 1
Phone 2 Phone 3
Full Quality Verification Short Call Long Call Dedicated Mode Full QA Short Call Long Call Reliability only QA Long Call Accessibility only QA Short Call Idle Mode only QA
Idle
Idle
Receiver Int --> Phone 3 BCH- Top Ch Int --> Phone 2 Int --> Phone 2 Int --> Phone 1 Int --> Phone 3 BCH-Top Ch
KPI – QA - TEST Call Performance Blocked call Rate Dropped Call Rate Handover Failures Coverage RF Idle Mode Coverage (Rxlev_Full) RF Receiver Based Coverage (Top N Power) Service Coverage (C/I In Idle Mode, DSC ) Quality RxQual Sub Rxlevel Sub Timing Advance RLTC Est Interference C/I and C/A
Call Stats Statistical DT data cannot be directly correlated with OMC data. For significant statistical DT reports, number of calls and drive hours should be high Recommended to combine multiple drives together and then generate Stats only module
