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Dropped Calls&Call Quality

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Agenda

Review dedicated channel operations SHO, BLER

Outline factors that can cause dropped calls

Illustrate the modes of failure and outline themethods of resolving dropped calls usingexamples

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W-CDMA Dropped Call Performance

Objectives Maximize call retention

Balance resource utilization with retainability

Inputs Mobile Drive Test Data long calls

System Statistics (mature network)

Tasks Characterize failures

Identify Performance impacting parameters andactions to resolve drops

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Dedicated

ChannelOperations

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Downlink BLER

Quality Target set for Signaling Radio Bearer

Each of the 3 AMR 12.2 Transport Channels

BLER Reports from UE Signaling Radio Bearer

First (A-bits) of the 3 speech Transport Channels

0.1*QualityTarget = LOG10(DesiredBLER)

If 2% is desired, Configure -1710(-1.7) = 0.02

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Z

Soft Handover Behavior

UE

A

D

Active Set

Monitoring Set

B C

E

F

Detected Set

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Soft Handover AlgorithmExample

Time

MeasurementQuantity P CPICH 1

P CPICH 2

P CPICH 3

T

H1a

Event 1A

= add cell 2

H1c

T

Event 1C

= replace cell1with cell3

H1b

T

Event 1B

= removecell3

H: Hysteresis

T: Time-to-trigger

ReportingRange

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Soft Handover AlgorithmExample (continued)

Time

MeasurementQuantity P CPICH 1

P CPICH 2

P CPICH 3

T

H1a

Event 1A

= add cell 2

H1c

T

Event 1C

= replace cell1with cell3

H1b

T

Event 1B

= removecell3

H: Hysteresis

T: Time-to-trigger

ReportingRange

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Active Set Management

RNCNode B

CN PSTN

UE

Iub IuUu

Measurement Report

Active Set Update

Active Set Update Complete

Setup and Add Radio Link

UTRAN informs UE of radiolinks added and/or deletedfrom the active set. Mayinclude reconfiguration ofRadio Bearer

Measurement Control

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ParameterSummary

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Parameter OverviewParameter Notes

e1a reporting range Triggered when a monitored CPICH Ec/No is measured withinX db of the strongest pilot in the active set

e1b reporting rangeTriggered when a monitored CPICH Ec/No is measured more

than X db less than the strongest pilot in the active set

e1c hysteresisTriggered when a monitored CPICH Ec/No is measured within

X db of any pilot in the active set

e1d reporting range

Triggered when the strongest pilot in the active set changes

new strongest pilot must be X db stronger prior to triggering

event 1d

Time to TriggerValue, typically in milliseconds, for which a condition must exist

prior to an event being triggered and sent to the UTRANNeighbor list List of cells to monitor

Periodic interval For periodic measurements, reporting interval

BLER TargetsUsed for outer loop power control, set for each transport

channel

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Summary

Courses of action BLER

Power allocation

Init power (for access) Relax sho

Coverage/NL

Tying it All Together Discussion: zeroing in on problem areas

Drive testing (scanner + calls)

Network Performance Stats (per cell failures)