Risk Identification and Analysis of Communication Project

Based on Fault Tree: The Case of the Telecom IVR Project BAI Xu

School of information Engineering,

Wuhan University of Technology, Wuhan, 430070, P.R.China

Tel:086-13397162758 Email:wuhantracy@gmail.com

Abstract—Aiming at the characteristics of communication projects such as the circumstance being complex

and affecting factors being numerous, a risk identification method has been put forward based on the fault

tree analysis and has combined work breakdown structure(WBS) with structure of risk analysis. With the

introduction of WBS-FTS, the coupling judgment has been carried out on the work breakdown structure

and risk resource breakdown structure of the telecom IVR project and the corresponding risk factors and

risk events have been stated. Then the logic connection among each factor has been set up according to

fault tree and the upper layer and the lower layer have been connected with logic gate, and thus come to the

main fault tree of IVR communication project. On this basis, the sensitivity analysis on risk factors has

been conducted and corresponding preventive measures have been put forward.

Keywords—communication project; fault tree analysis; risk identification; sensitivity analysis

0 INTRODUCTION

With arrival of the era marked with the integration of

data and information, telecom value-added services are

also entering the real golden age, and "to enter the field of

value-added services" has become a unique landscape.

The IVR (Interactive Voice Response) is a new hotspot

and benefit growth point within the field of telecom

value-added services. IVR communications project is a

complicated system as well as a reciprocal chiasma

interrelated entirety, involving the combination of new

technologies and original business, but also including the

impact of market conditions and other aspects. Therefore,

IVR project is a risk project and it is necessary to identify

and analyze the risk events as well as taking appropriate

preventive measures to avoid accidents.

At present, domestic and international research on the

risk of IVR project is still in its infancy, and the risk

identification methods mainly include case analysis,

factor analysis, SWOT analysis, brainstorming, Delphi

method, etc. However, these methods have their own

advantages and effects for the identification of risk, but

not fixed for the identification of risk. The absolutely

effective method should be chosen flexibly according to

project characteristics and considered comprehensively,

thus risk analysis can be conducted quickly and

efficiently. Therefore, in this thesis, the WBS method will

be used to give system decomposition of the IVR

communication engineering work structure and risk

source, and couple to the relevant risk factors and events.

Then establish the IVR communication engineering fault

tree with the logic gate according to the logic connection,

and on this basis determine the key risk factors and put

forward preventive measures through sensitivity analysis.

I. FAULT TREE ANALYSIS

Fault Tree Analysis (FTA) is a technology suitable for

the reliability and safety analysis of large and complex

system. With the application of mathematical logic

methods, FTA take the most undesired event of the

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system as the top event of the fault tree, and then look for

the trigger event, the direct and indirect causes leading to

the event gradually level by level as well as analyzing the

logical relationships between the causes of each event.

Consequently the various compound modes and the

occurrence probability of the causes leading to the system

failure are determined, and corresponding measures are

taken to improve the system reliability.

The characteristics of fault tree analysis are intuitive,

intelligible, clear and logical, and qualitative analysis can

be made as well as quantitative analysis. Not only the

relationships of failures inside the system are reflected,

but also reflect the influence of the external factors of the

system (environmental factors, human errors, etc.) The

process of fault tree analysis is an in-depth understanding

process of the system, which requires the researchers to

grasp the internal relations of the system and to ascertain

the impact way and degree of the underlying factors

having on the failures, So that the problems can be

analyzed and solved in the analysis process to improve

the system reliability. The analysis steps are listed below:

Table 2-1 The basic steps of FTA

the basic

analysis steps Specific contents

Learn more about the system state and

various parameters, and draw the flow chart

or lay-out diagram.

Collect incident cases, conduct accident

statistics, and envisage the possible accidents

in the given system.

Give comprehensive analysis on the accident

investigated to find out the consequences

which are more likely to occur and may lead

to serious consequence as the top event

According to lessons learned and accident

cases, solve the accident probability

(frequency) as a target value to control the

incident by statistical analysis.

1.Familiar with

the system

↓

2. Investigate

the accident

↓

3.Determine

the top event

↓

4.Determine

the target value

↓

5. Investigate

Investigate all the accident-related cause

events and various factors.

Find out the direct cause accident step by

step from the top event, until get the desired

depth of analysis, and draw the fault tree

according to the logic.

Simplify fault tree in the structure ,and

determine the structure importance degree of

basic events

Determine the occurrence probability of all

incidents, mark on the fault tree, and find the

occurrence probability of the top event

(accident).

Compare and discuss the maintenance

system and non-maintenance system.

Compare the former and calculate top event

probability of the latter.

the cause

accident

↓

6. Draw the

fault tree

↓

7.Analyze

↓

8.Accident

probability

↓

9.Compare

↓

10.Analyze In the analysis, keep flexible according to

the particular issue. If the fault tree is large,

we can make use of computer.

As a logical causality diagram, the fault tree diagram

displays the system status (top event) in accordance with

the component unit status (basic events). The systematic

fault tree logic model formed by Boolean logic gates

(such as "and", "or") describes how the combination of

the equipment failure and human error lead to the top

event.

II. THE RISK IDENTIFICATION AND ANALYSIS OF IVR

COMMUNICATION PROJECT

A. The risk factor identification of IVR communication

project

The risk identification of telecom has made use of the

existing achievements such as the telecom IVR project

flow chart (Figure1), the project requirements

specification and the project development plan. Based on

the Work Breakdown Structure (WBS) table and the

schedule plan of the project development plan, the project

team members can consider the risk factors in accordance

with the different stages and each unit in the project work

breakdown structure diagram, thus forming the project

risk identification list.

According to the project risk identification feature of

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all-the-people-involvement and in reference to the Delphi

method, the risk identification is conducted based on the

preliminary risk classification standard and risk lists by

the experienced employees from the telecom subsidiary

design institute, the project center director of the IVR, the

network infrastructure department, the information

transfer department, the system software control

department , the international liaison department and

other related sectors, and in this basis a formal risk list

document is formed (table 3-1). Through the staff's view

of risk identification, calculate the average, and "average"

means the average number of days delayed. In addition,

the optimistic value, pessimistic value and the most

probable value of the risk occurring probability from the

staff are converted into a risk occurrence "probability"

with the three point method.

Project approval risk

B. construct the WBS-FTA diagram of telecom IVR

project

From the development process of telecom IVR project,

the main factors that have led to the failure of the project

exist in almost every phase and the number of factors is

pretty large, so the work breakdown structure (WBS) of

the IVR project and the FTA analysis combined to

evaluate the risk of the telecom IVR project. Firstly,

adjust Table 3-1 by classifying the delayed days of

several stages caused by a risk to the first place where the

risk appears, and the adjusted table is shown as Table 3-2.

Secondly, the fault tree diagram of the telecom IVR

project constructed in accordance with the basic principle

of fault tree and the work breakdown and development

risk factors of the telecom IVR project development is

shown as Figure 2.

Combine table 2 (data derives from survey) and the

characteristics of telecom IVR project with the fault tree,

and give collation and calculation to the data, then it

comes to the probability and weight of the risk source

of telecom IVR project (the basic events on fault tree),

shown in table 3-2. Weight is calculated as:

FIGURE 1 THE TELECOM IVR PROJECT PROCEDURES AND RISK

IDENTIFICATION

TABLE 3-1 THE TELECOM IVR PROJECT RISK LIST AND RISK

IDENTIFICATION

Risk factor’s impact on project

schedule（unit：day） R

is

k

Risk factor Pha

se 1

Pha

se 2

Pha

se 3

Pha

se 4

ave

rag

e

pro

babi

lity

%

1Overall solution

design

1.

1

Network

arrangement 3 2 2 2 2.25 20

Market forecasting Phase 1：Overall

solution design Design risk

Phase2：Network

arrangement

Phase 3:

Equipment

Network adjustment

Equipment introduction

Material supply risk

Base station location

Base station negotiation

Phase4:The

installation and

debugging of

Personnel risk

Management risk

Project phase flow Risk factors of the project

The total process of the project

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1.

2

Excessive

design of

equipment

subscriptions

2 — — — 0.50 20

1.

3

Low level of the

clients’

technicians

1 — — 3 1.00 30

1.

4

The frequent

extra demands

made by clients

1 2 1 1 1.25 40

1.

5

The strategic

objective of the

clients being

unclear.

1 — — — 0.25 10

2 Network

arrangement

2.

1

Central

apparatus room

dissatisfies the

design

requirements

— 2 — — 0.50 30

2.

2

The poor quality

of

communications

circuits

— 3 2 1 1.50 30

2.

3

Network

adjustment

affects the users’

use.

— 2 — — 0.50 50

2.

4

The adjustment

of network

coverage area

— 2 1 — 0.75 40

3 Equipment

installation

3.

1

Inappropriate

Device picking

for its

unfamiliarity to

the manufacture

— — 3 1 1.00 40

3.

2

The negotiation

risk of

base-station

installation

brought by

market

competition

— — 3 — 0.75 30

3.

3

the delay of the

equipment

materials supply

— — 2 1 0.75 50

4

The installation

and debugging

of software

system

4.

1

Cross-departme

nt coordination 1 1 1 1 1.00 20

4.

2

The rework

modification of

the project

— — — 6 1.50 20

4.

3

Slow market

reaction of the

project

1 — — — 0.25 30

TABLE 3-2 THE TELECOM IVR PROJECT RISK ADJUSTMENT TABLE

Risk factor’s impact on

project schedule（unit：day）

ris

k

nu

mb

er

Risk factor

P

h

a

se

1

Ph

ase

2

Ph

ase

3

Ph

ase

4

av

er

ag

e

p

r

o

b

a

bi

li

ty

%

1 Overall

solution design

M1

1.1 Inaccurate

network

capacity survey

X0

9 — — — 2.

25

2

0

1.2 Excessive

design of

equipment

subscriptions

X1

2 — — — 0.

50

2

0

1.3 Low level of

the clients’

technicians X2

4 — — — 1.

00

3

0

1.4 The frequent

extra demands

made by clients

X3

5 — — — 1.

25

4

0

1.5 The strategic

objective of the

clients being

unclear. X4

1 — — — 0.

25

1

0

1.6 Cross-departm

ent

coordination

X5

4 — — — 1.

00

2

0

1.7 Slow market

reaction of the

project X6

1 — — — 0.

25

3

0

2 Network

arrangement

M2

2.1 Central

Apparatus

Room

dissatisfies the

design

requirements.

X7

— 2 — — 0.

50

3

0

2.2 The poor

quality of

communication

s circuits X8

— 6 — — 1.

50

3

0

2.3 Network

adjustment

affects the

users’ use. X9

— 2 — — 0.

50

5

0

2.4 The adjustment

of network

coverage area

X10

— 3 — — 0.

75

4

0

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3 Equipment

installation

M3

3.1 Inappropriate

Device picking

for its

unfamiliarity to

the

manufacture

X11

— — 4 — 1.

00

4

0

3.2 The

negotiation risk

of base-station

installation

brought by

market

competition

X12

— — 3 — 0.

75

3

0

3.3 the delay of the

equipment

materials

supply X13

— — 3 — 0.

75

5

0

4 The installation

and debugging

of software

system M4

4.1 The rework

modification of

the project

X14

— — — 6 1.

50

2

0

FIGURE 2 THE TELECOM IVR PROJECT FAULT TREE

：the delayed days caused by risk factor i of the

project

： the delayed days caused by all the risk factors

of the project

TABLE 3-3 THE PROBABILITY AND WEIGHT OF THE BASIC EVENT IN THE

TELECOM IVR PROJECT PROCEDURES AND RISK

Basic event Probability q Weight w

X0 0.20 0.163636

X1 0.20 0.036364

X2 0.30 0.072727

X3 0.40 0.090909

X4 0.10 0.018182

X5 0.20 0.072727

X6 0.30 0.018182

X7 0.30 0.036364

X8 0.30 0.109091

X9 0.50 0.036364

X10 0.40 0.054545

X11 0.40 0.072727

X12 0.30 0.054545

X13 0.50 0.054545

X14 0.20 0.109091

C. The risk analysis on the telecom IVR project based

on Fault tree

According to the analysis on the telecom IVR project

fault tree, the minimal cut set of the telecom IVR project

can be obtained, and then through the analysis of

probability and weight M1, M2, M3, M4, T are

calculated(shown in Table 3-4.

TABLE 3-4 THE QUANTITATIVE ANALYSIS ON THE TELECOM IVR

PROJECT

Basic

event

Probability

q

Weight w M T

X0 0.20 0.163636

X1 0.20 0.036364

X2 0.30 0.072727

X3 0.40 0.090909

X4 0.10 0.018182

X5 0.20 0.072727

X6 0.30 0.018182

M1=0.12

X7 0.30 0.036364

X8 0.30 0.109091

X9 0.50 0.036364

X10 0.40 0.054545

M2=0.08

X11 0.40 0.072727

X12 0.30 0.054545

X13 0.50 0.054545

M3=0.07

T=1.344×10-5

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X14 0.20 0.109091 M4=0.02

(4) The analysis of probability importance degree and

criticality importance degree

To get to know how much impact the change of basic

event’s(Xi) probability has brought on the top event(T)

further, it is expected to analyze the probability

importance degree of the basic events, the formula is as:

ig q

TiI

)(

Calculating Ig（0）：

Ig（0）= w0*M1*M2*M3= 0.00001833 Calculating Ig（1）、Ig（2）、Ig（3）、Ig（4）、Ig

（5）、Ig（6）、Ig（7）、Ig（8）、Ig（9）、Ig（10）、Ig（11）、Ig（12）、Ig（13）、Ig（14）in sequence, shown as table 5-7。

The probability importance degree tells us materiality

level of the basic events on the top event, but it failed to

reflect on how to reduce the probability of the basic

events with a large probability. Hence it is expected to

calculate the criticality importance coefficient, which

measures the important standard of each basic event from

is the point of view of probability and sensitivity. The

formula is:

Lnq

LnTiCI g

)(

TABLE 3-5 THE PROBABILITY AND CRITICALITY IMPORTANCE DEGREE

OF THE TELECOM IVR PROJECT BASIC EVENTS

Basic event probability

importance degree

criticality importance

degree

X0 1.833×10-5 0.2727

X1 0.407×10-5 0.0606

X2 0.815×10-5 0.1818

X3 1.018×10-5 0.3030

X4 0.204×10-5 0.0151

X5 0.815×10-5 0.1212

X6 0.204×10-5 0.0455

X7 0.611×10-5 0.1363

X8 1.833×10-5 0.4090

X9 0.611×10-5 0.2273

X10 0.916×10-5 0.2727

X11 1.396×10-5 0.4156

X12 1.047×10-5 0.2338

X13 1.047×10-5 0.3896

X14 7.331×10-5 1.0909

D. The risk analysis result of telecom IVR project

(1)According to the fault tree of telecom IVR project,

there are a total of 84 minimal cut sets in IVR project,

which indicates that there are 84 ways leading to the

occurrence of the top event in the telecom IVR project.

The more the minimal cut sets are, the more dangerous

the system is, that is to say that the minimum cut set

reflects the risk level of the system.

(2)From the minimum path set of the telecom IVR

project fault tree, IVR project has a total of 4 minimal

path sets, which are the sufficient and necessary

conditions to ensure the top event not to occur. There are

84 minimal cut sets and 4 minimal path sets in the IVR

project fault tree, so it is more convenient to analyze the

minimal path set. For example, P4 = (X14) means X14

does not occur, and then the top event does not occur.

And during the analysis that P4 does not occur, the other

can be ignored. That is, if the rework succeeds after the

project ends, the telecom IVR project development can be

considered successful even if the Phase 1, Phase 2 and

Phase 3 are not going well.

(3) The probability importance degree of telecom IVR

project is the most effective approach to prevent the

failure of the system development. According to the

probability importance degree, the sorting of the telecom

IVR basic event’s probability is as follows:

X14> X0 = X8> X11> X12 = X13> X3> X10> X2 =

X5> X7 = X9> X1> X4 = X6

This indicates that the event that rework modification

can not be completed affects the telecom IVR project

risks most, followed successively by the following events:

inaccurate network capacity survey, the poor quality of

communication circuits, inappropriate Device picking for

its unfamiliarity to the manufacture, the negotiation risk

of base-station installation brought by market competition,

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the delay of the equipment materials supply, the frequent

extra demands made by clients, the adjustment of network

coverage area, low level of the clients’ technicians,

cross-department coordination, central apparatus room

dissatisfies the design requirements, network adjustment

affects the users’ use, excessive design of equipment

subscriptions, the strategic objective of the clients being

unclear, slow market reaction of the project.

(4) The criticality importance degree of the telecom

IVR project reflects each basic event’s sensitivity to the

project risk, and the sorting is as follows:

X14> X11> X8> X13> X3> X0> X10> X9> X12> X2>

X7> X5> X1> X6> X4

According to the sorting, the project rework

modification is the most important for the IVR project.

Meanwhile, through the comparation of the criticality

importance degree and the probability importance degree,

it is concluded that the risk of the IVR project can be

greatly reduced by improving the following problems

substantially: if the IVR projects, Inappropriate Device

picking for its unfamiliarity to the manufacturer, poor

quality of communication circuits, the delay of the

equipment materials supply, the frequent extra demands

made by clients, the adjustment of network coverage area,

network adjustment affects the users’ use.

III. CONCLUSIONS

The implementation process of the IVR project is a

complex, one-off, open and complex system involving

many relations and variables, and the risk factors

affecting the system are numerous and anfractuous. At the

same time, the severity of consequence caused by

different risk factors is quite different, and there is great

uncertainty whether the project will achieve the desired

result. In this thesis, correlation analysis has been

conducted on the telecom IVR project with the fault tree

method, and the results indicate that: the core of the IVR

project management is risk management, the rework

modification of the project, equipment selection when

manufacturers do not thoroughly understand; the poor

quality of communication circuits, the delay of the

equipment materials supply, the frequent extra demands

made by clients, the adjustment of network coverage area,

network adjustment affects the users’ use, are the key risk

factors in the telecom IVR project that call for great

attention. Therefore system thinking of the risk

management in these areas needs to be strengthened and

corresponding preventive measures should be taken to

avoid the occurrence of the risks.

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