Network selection techniques:SAW and TOPSIS

Network Selection in Heterogeneous Wireless Networks

ByYashwant110603

EC-7

CONTENT

• Hetrogeneous Wireless Network• Handover• Network Selection• Multi-criteria Decision Making• TOPSIS• SAW• Comparison• conclusion

Heterogeneous Wireless Networks

• Co-existing radio access technologies• WWANs, WPANs, WLANs, WMANs • coverage overlapping one another• always best connected(ABC)• Different network architectures and protocols for

transport, routing and mobility management.• Reliability, spectrum efficiency, increased coverage.• Multi-homing & multimode interfaces

4

Heterogeneous Wireless Networks

HANDOVER

• Service continuity• Select best network with minimum processing

delay• Vertical Handover• Horizontal Handover

Network Selection

• Based on various criteria– Traffic demand– Quality of service– Bandwidth and round-trip-time estimations– Application requirements– Registration cost– Security of data

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Multi-criteria Decision Making

• Selection of the best, from a set of alternatives, each of which is evaluated against multiple criteria.

• Some problem solving techniques are :• SAW (Simple Additive Weighting)• TOPSIS (Technique for Order Preference by Similarity to

the Ideal Solution)• ELECTRE (Elimination et Choice Translating Reality)• AHP (The Analytical Hierarchy Process)• SMART (The Simple Multi Attribute Rating Technique )• ANP (Analytic network process)

Important terms…• Alternatives – These are the options which are to be evaluated for

selection of the best.• Example: (for Network problem)net1,net2,net3,net4 etc.

• Criteria or Attributes – These will impact the selection of alternatives Example: (for Network problem) Bandwidth, QoS, Cost, security level etc.

Completeness: It is important to ensure that all of the important criteria are included.

Redundancy: In principle, criteria that have been judged relatively unimportant or to be duplicates should be removed at a very early stage.

Operationality: It is important that each alternative can be judged against each criterion.

Important terms…• Weights – These estimates relative importance of

criteria. Each attribute is given certain points on 0-10 or 0-100 rating

scale by a team of experts or decision makers. Example:

criteria weight rating scale Bandwidth - 4 10 very good -1 none QoS - 2 10 very good -1 none Security - 6 1 low-10 very high Cost - 8 1 low-10 very high

Important terms…

There can be ‘n’ number of decision makers. Example:

criteria rating scaleBandwidth - 10 very good -1 noneQoS - 10 very good -1 noneSecurity - 10 low-1 very highcost - 10 low-1 very high

Decision makers – These are experts who are assigned with the task of weighting each attribute.

Criteria Decision makers Attributes weights

Harry Ron Hermoine

bandwidth 4 2 6 =4

Qos 2 3 1 =2

Security 6 4 8 =6

Cost 8 9 7 =8

Important terms…Decision matrix – A table that is used to objectively make

decision about making selection from a range of options.

Criteria Network 1 Network 2 Network 3

Bandwidth 9 8 7

Qos 7 7 8

Security 6 9 6

COST 7 6 6

TOPSIS

In this method two artificial alternatives are hypothesized:

Ideal alternative: One which has the best attributes values (i.e. max. benefit attributes and min. cost attributes)

• Negative ideal alternative: One which has the worst attribute values. (i.e. min. benefit attributes and max. cost attributes)

TOPSIS selects the alternative that is the closest to the ideal solution and farthest from negative ideal solution.

Technique for Order Preference by Similarity to Ideal Solution

Steps involved in TOPSIS…• Step 1 – standardize the decision matrix.– This step transforms various attribute dimensions

into non-dimensional attributes, which allows comparisons across criteria.

– For standardizing, each column of decision matrix, is divided by root of sum of square of respective columns.

Criteria Network 1 Network 2 Network 3 Root of sum of square

Bandwidth 9 8 7 = = 13.93

QoS 7 7 8 = =12.73

Security 6 9 6 = =12.37

Cost 7 6 6 = = 11.00

DECISION MATRIX

Steps involved in TOPSIS…• Step 1 – standardize the decision matrix.– This step transforms various attribute dimensions

into non-dimensional attributes, which allows comparisons across criteria.

– For standardizing, each column of decision matrix, is divided by root of sum of square of respective columns.

Criteria Network 1 Network 2 Network 3 RSS

Bandwidth 9 8 7 = = 13.93

Qos 7 7 8 = =12.73

Security 6 9 6 = =12.37

COST 7 6 6 = = 11.00


Bandwidth 9 / 13.93

Qos

Security

COST


Bandwidth 0.65

Qos

Security

COST

Standardized decision matrix….


Bandwidth 9 / 13.93 8 / 13.93

Qos

Security

COST


Bandwidth 0.65 0.57

Qos

Security

COST



Bandwidth 9 / 13.93 8 / 13.93 7 / 13.93

Qos

Security

COST


Bandwidth 0.65 0.57 0.50

Qos

Security

COST



bandwidth 0.65 0.57 0.50

QoS

SECURITY

COST


Bandwidth 0.65 0.57 0.50

Qos 0.55 0.55 0.63

Security 0.49 0.73 0.49

COST 0.64 0.55 0.55


Similarly….

Steps involved in TOPSIS…• Step 2 - Construct weighted standardized decision matrix

by multiplying attributes weight to each rating.


bandwidth 0.65 0.57 0.50

Qos 0.55 0.55 0.63

Security 0.49 0.73 0.49

COST 0.64 0.55 0.55


Bandwidth 2.6Qos

Security

COST

Attributes weights

Weighted Standardized decision matrix

X

Standardized decision matrix

Steps involved in TOPSIS…


bandwidth 0.65 0.57 0.50

QoS 0.55 0.55 0.63

Security 0.49 0.73 0.49

Cost 0.64 0.55 0.55


Bandwidth 2.6 2.28Qos

Security

Cost

Attributes weights Standardized decision matrix

X


• Step 2 - Construct weighted standardized decision matrix by multiplying attributes weight to each rating.

Steps involved in TOPSIS…• Step 2 - construct weighted standardized decision matrix



bandwidth 0.65 0.57 0.50

QoS 0.55 0.55 0.63

Security 0.49 0.73 0.49

Cost 0.64 0.55 0.55


bandwidth 2.6 2.28Qos 1.1Securit

Cost


X



bandwidth 2.6 2.28QoS 1.1SECURITY

COST

Steps involved in TOPSIS…• Step 2 - construct weighted standardized decision matrix



Bandwidth 2.6 2.28 2Qos 1.1 1.1 1.26Security 2.94 4.38 2.94Cost 5.12 4.4 4.4

Similarly….


Steps involved in TOPSIS…• Step 3 – Determine ideal solution and negative ideal solution.


Bandwidth 2.6 2.28 2

Qos 1.1 1.1 1.26

Security 2.94 4.38 2.94

Cost 5.12 4.4 4.4

Ideal solution = {2.6, 1.26, 4.38, 5.12}

2.61.264.385.12

A set of maximum values for each criteria is Ideal solution.

Max.

Max.

Max.

Max.


Bandwidth 2.6 2.28 2

Qos 1.1 1.1 1.26

SECURITY 2.94 4.38 2.94

COST 5.12 4.4 4.4

Steps involved in TOPSIS…• Step 3 – Determine ideal solution and negative ideal solution.

Negative Ideal solution = {2.6, 1.26, 2.94, 4.4}

2.01.12.944.4

A set of minimum values for each criteria is Negative Ideal solution.

Min.

Min.

Min.

Min.

Steps involved in TOPSIS…• Step 4 – Determine separation from ideal solution. Si*

Criteria Network1 Network 2 Network 3

Bandwidth (2.6-2.6)2 (2.28-2.6) 2 (2.0-2.6) 2

Qos (1.1-1.26) 2 (1.1-1.26) 2 (1.26-1.26) 2

SECURITY (2.94-2.94) 2 (4.38-2.94) 2 (2.94-2.94) 2

COST (5.12-4.4) 2 (4.4-4.4) 2 (4.4-4.4) 2


Bandwidth 0.0 0.10 0.36

Qos 0.02 0.02 0.0

SECURITY 0.0 2.07 0.0

COST 0.51 0.0 0.0

0.74 1.48 0.6Si* = (0.+0.02+0+0.51)1/2 (.1+.02+2.07+0)1/2 (0.36+.0+0+0)1/2

= = =

Steps involved in TOPSIS…• Step 5 – Determine separation from negative ideal solution.


Bandwidth (2.6-2.0)2 (2.28-2.0) 2 (2.0-2.0) 2

Qos (1.1-1.1) 2 (1.1-1.1) 2 (1.26-1.1) 2

SECURITY (2.94-4.38) 2 (4.38-4.38) 2 (2.94-4.38) 2

COST (5.12-5.12) 2 (4.4-5.12) 2 (4.4-5.12) 2


Bandwidth 0.36 0.07 0.0

Qos 0.0 0.0 0.02

SECURITY 2.07 0.0 2.07

COST 0.0 0.51 0.51

(0.36+0+2+0)1/2 (.07+0+0+.51)1/2 (0+.02+2+.51)1/2

1.56 0.773 1.618Si’ =

= = =

Steps involved in TOPSIS…• Step 6 – Determine relative closeness to ideal solution.


Si* 0.74 1.48 0.6

Si’ 1.56 0.773 1.618

Si*+Si’ 2.3 2.253 2.218

Si’ /(Si*+Si’ )1.56/2.3 0.77/2.25 1.62/2.21

0.68 0.343 0.729

BEST

Max.

OVERALL ALGORITHM

Simple Additive Weighting(SAW) Method

• Simple Additive Weighting – Weighted Average – Weighted Sum

• A global (total) score in the SAW is obtained by adding contributions from each attribute.

• A common numerical scaling system such as normalization (instead of single dimensional value functions) is required to permit addition among attribute values.

• Value (global score) of an alternative can be expressed as:

V(ai) = Vi =

n

jijj rw

1

Steps in SAW…..• Step 1-Normalization of decision matrix

decision….. matrix…..

Criteria Network 1 Network 2 Network 3Bandwidth 9 8 7Qos 7 7 8Security 6 9 6COST 7 6 6


Bandwidth 1 .88 .77

Qos .875 .875 1

Security .66 1 .66

COST 1 .857 .857

Steps involved in SAW…


bandwidth 1 0.88 0.77

QoS 0.875 0.875 1

Security 0.66 1 0.66

Cost 1 0.857 0.857


Bandwidth 4 3.52Qos

Security

Cost


Weighted normalized decision matrix

• Step 2 Evaluation of score for each alternative V(ai) = Vi =.

n

jijj rw

1

Steps involved in SAW…

• Evaluation of score for each alternative….


Bandwidth 4 3.52 3.08Qos 1.75 1.75 2Security 3.96 6 3.96Cost 8 7 7

sscore 17.71 18.27 16.04

BEST

COMPARISION

• Criteria1. The Packet Jitter (J)2. The Packet delay (D)3. Utilization (U)4. The Packet Loss (L)5. The Cost (CB)

COMPARISON

• Comparision of ranking order

COMPARISION

• Difference between ranking values..

COMPARISION……

Ranking abnormality..

Simulation results

• Ranking abnormalities• Precision• Ranking identifications

CONCLUSION

Although TOPSIS surfers from the ranking abnormality problem, it provides a more precision in alternative rankings compared to SAW.

THANK YOU

Network selection techniques:SAW and TOPSIS

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