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Drive-Test
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DrivetestDrivetest
Tools
• Mobile TEMS Pocket W600i• GPS• Compass• Inverter – input 12V, Output 220 V ac, 400 W• TEMS Software 7.1.1 Data Collection• TEMS Software 7.1.1 Route Analisys• Map Info
Work Process
CollectOMC Parameter
DatabaseRF Network Design
Cell File (TEMS)And
Dot Tab Site (mapinfo)
Drive Test Measurements
Analysis Programs
Coverage
Dropped Calls
Call Setup Success
Handover Perf.
Speech Quality
General Check
Verification of RF Network Design
Site Check
Test Mobile Measurements
• Collect RxLev measurements together with GPS co-ordinates• Analyse on planning tool• Reasons for poor coverage:
– serving cell not best server• handover problems
– best server signal low• check site / network design
• Analyse in terms of relevant
thresholds:– indoor level– in-car level– outdoor level
Test Types
• Continuous drive test– setup a test call and drive over an area for detecting lack of
coverage, missing handovers, interferences etc.• Spot test
– detail measurement to be taken at dedicated problem spots for detail analyzing of specific problem
Collect / Analyse Drive Test Measurements
• Test measurement (TEMS etc. together with a GPS)
– Signal Strength
– Co-channel and adjacent interference
– Handover relations
• Test types
– Continuos drive test (Trace mode)
– Spot test
– Network performance test (Statistical mode)
• Test Measurement
– Collect MS measurement report data (Downlink only!!)
Coverage: Analysis for Fulfilment of Coverage Requirements (Urban, rural ... areas, outdoor, in-car, indoor)
Dropped Call: Analysis for Dropped Calls due to Interference, SW/HW failures, Transmission Network Failures
Call Setup: Analysis for Blocking and CapacityLimitations, Analysis for Resource Allocation Procedures
Handover: Analysis for Efficient HandoverPerformance
Speech Quality: Analysis for Interference
Analysis Programs
Dropped Call Analysis
• How to measure – drive tests
• repeated call setups (preferred)• continuous calls
– OMC measurements• Reasons for dropped calls
– lack of coverage– interference problems– handover problems– lack of synchronisation in network– problems with other parts of the network
Call Setup Analysis
• Reasons for failed call setups– lack of coverage– database problems
• database inconsistencies• parameter settings, e.g.
– RXLEV_ACCESS_MIN, RACHBT, RACH_MAX_RETRANS
– cell reselection related parameters– network congestion
Handover Parameters
• Fine-tuning of handover parameters– Moving cell boundaries in order to
• Enhance success rate for critical handovers• Minimise local interference at the cell edge• Traffic load sharing between cells
– Compared to other opimisation measures improvement potential is limited
– Affected by• Measurement averaging• Power control parameters
PS! Neighbours should in generalbe mutual
Speech Quality Analysis
• Parameters– RxQual– Frame Erasure Rate (FER)– Speech Quality Index (SQI)
• Measurements– Drive test
• preferably continuous call
– OMC statistics• Cause for poor quality
– low signal strength (coverage related
– interference– low signal strength and
interference
• Causes of interference
– co-channel interference
– adjacent channel interference
– intermodulation
• mainly on one link only
– multipath interference
Location Area Codes
• Purpose– identify location area– in incoming call is paged to all BTS’s within LA
• Large location area– advantage: less location updates (reduced SDCCH load)– disadvantage: more paging traffic
• Boundaries should not cross high traffic areas• Cell reselection across LA boundaries
– Parameter Cell_Reselect_Hysteresis (typ. 4 dB) used to avoid unnecessary signalling due to ping-pong cell reselections
No serviceNo coverageNo System Availability
Network Element FailuresTransmission Network Failures
Low call setup success rateRF Network
No coverageInterferenceBlocking
Fixed Network BSS, SSSBlockingOverloadOther
High call drop rateRF Network
No coverageInterferenceHandover failure
Fixed Network BSS, SSSNetwork Element FailureTransmission FailuresOther networks
Mobile terminal
Poor speech qualityRF Network
No coverageInterferencePoor handover performance
Fixed Network BSS, SSSNetwork element failureTransmission network failureOther networks
Mobile Phone
Problem Symptoms
Reporting (example)
Advantages over test drives
– Less labor intensive and time consuming– More comprehensive, based on large number of users– not limited to time of test drive– Uplink and Downlink analysis possible– Subscriber behavior mix of outdoor, indoor, incar use
FINE TUNINGFINE TUNING
• Digital Tilt Meter• GPS• Compass• Spanner• Screw Driver Set• Safety Belt• Adjustable Wrench• Cutting Pliers• Mesuring Tape• Safety Shoe• Map Info• Map Source• Google Earth
Tools
Antenna Configuration
• General points to check– antenna type, e.g.
• omni• directional 60, 90 or 120 degrees• electrical downtilt• cross-polarised
– antenna azimuth angle (for directional antennae)• coverage targets
– antenna tilt angle• electrical + mechanical
– diversity & isolation• e.g. space diversity, • polarisation diversity
Site Check
• Verify that site is implemented according to plan• Check installation e.g.
– antenna spacing (diversity, isolation)– antennae in one sector are installed in the same plane– antennae alignment– omni antenna installation– cable installation
k
a
Vertical spacing
d
Horisontal spacing
Rx
Tx
Rx Tx
max 15 °
Antennas mounted in different planes
a
a=
d d d
Alignment of antennas
Rx Tx Rxd
k1
Rx
Tx
Rxd
k2 k2
Omni
Antenna Fine Tuning
• Horizontal Plane:– Possible coverage weakness between sectors– Interference reduction– Traffic load distribution
• Vertical Plane:– Interference reduction– Possible coverage weakness in the short to medium distance
range– Traffic load distribution
Omni vs. Sectorised
• OMNI cells - more difficult to optimise– Electrical downtilt possible, however
• same for entire cell– Parameters same for entire cell
• Directional antennae– narrower beam easier to control interference– tilting less efficient with wider beams
Sectorised cell site with different downtilt angles
Tilting
• Antenna downtilt often used to minimise interference– Minimum: Vertical mail lobe pointing at cell edge
BSh
– Maximum: First null angle pointing at cell edge
0 ° 0 °
Electrical Mechanical
– Advantages:• Better back lobe characteristics• Better lower side lobe characteristics
– Disadvantages:• Antennas are more expensive
Tilting
• Electrical vs. Mechanical downtilt
A combination ofmechanical / electricaldowntilt may be used
Reporting (example)
thanksthanks