26 Dropped Call Analysis-18.ppt

7/30/2019 26 Dropped Call Analysis-18.ppt

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Dropped Call Analysis

ZTE University

CDMA-BSS Team


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Section Description

The dropped Call Rate is a key criteria in the evaluation of a CDMAsystem. IS-95A specifies that the mobile will maintain counters forcertain negative events such as receipt of a frame error. When thecounters reach a threshold, the mobile will disable its transmitterand return to the Initialization State (drop the call). This studentguide refers to these counters and their associated rules as

Dropped Call Mechanisms. Generally, it is not difficult to identify the particular mechanism,

however is only a superficial indication. A careful analysis must beundertaken to determine the underlying cause of the call drop.

The goal of this section is to provide insight into the analysis of

dropped calls. Dropped Call Signature Templates are presentedto aid the student in identification of the specific cause of a droppedcall. Call Drops are analyzed here based on data logged by themobile


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Section Learning Objectives

Overall Section Learning Objective : After Completing this

section, each student will be able to identify the cause of a

dropped call.

Specific Section Learning Objectives : Each student will be

able to :

1.List and describe the standard call drop mechanisms.

2.Discuss the options for proprietary call drop mechanisms.

3.Use dropped call signature templates to determine the

cause of a dropped call.


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A Closed Loop Signaling Path

Closed Loop Signaling is Required


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Bad Frames

Fade Timer

AcknowledgmentFailure

Call Drop Mechanisms in MS side


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Bad Frames

AcknowledgmentFailure

Call Drop Mechanisms on BTS side


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Indicates the general trend

of the parameter and approx.

range

30

0

-15

-100

Indicates the time

of occurrence of

key events.

Scale is log10 with

units of dB or dBm.

Drop Call Signature Templates


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30

0

-15

-100

23

Access/Handoff Contention Drop


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30

0

-15

-100

23

Forward Interference Drop Long Term Interference


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30

0

-15

-100

23

Forward Interference Drop Short Term Interference


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30

0

-15

-100

23

Imbalance Drop


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30

0

-15

-100

23

Coverage Drop Long Term Coverage Outage


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30

0

-15

-100

23

Coverage Drop Short Term Coverage Outage


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30

0

-15

-100

23

Constrained Traffic Channel Power Drop


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1Is new BTS? Is there any new BTSs? ( Macro BTS? Micro-BTS? Or

Repeater?)

2Check the neighbor list configuration. Pay attention to multicarrier area the

configuration for Critical cell or preferred cell

3Check if there are the alarms or notices for the cell itself or the other cells

around. (GPS CHMRF linktransmission ), check the RF transmission

power normal or not especially for dual-frequency?

4Check the master and slave version of BTS;

5Check the cell locate at the edge of BSC coverage area or not;

6Check the RSSI of this cell or around cells;

7Confirm the configuration of radio parameters include the search window,

cell radius, handoff parameters and so on; 8Observe the abnormal release reason from release observation. ( which

CHM? Which CE? Which IMSIWhich VE?) ;

9if above all can not work , recommend to do Drive Test to analyze the

coverage and environment of the call drop area.

Call Drop Analyzing procedure


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Section Review

1. List and describe the standard call drop mechanisms.

2. Discuss the options for proprietary call drop

mechanisms.

3. Use dropped call signature templates to determine the

cause of a dropped call


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Documents

26 Dropped Call Analysis-18.ppt