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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
6
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
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
Criteria Network 1 Network 2 Network 3
Bandwidth 9 / 13.93
Qos
Security
COST
Criteria Network 1 Network 2 Network 3
Bandwidth 0.65
Qos
Security
COST
Standardized decision matrix….
Criteria Network 1 Network 2 Network 3
Bandwidth 9 / 13.93 8 / 13.93
Qos
Security
COST
Criteria Network 1 Network 2 Network 3
Bandwidth 0.65 0.57
Qos
Security
COST
Standardized decision matrix….
Criteria Network 1 Network 2 Network 3
Bandwidth 9 / 13.93 8 / 13.93 7 / 13.93
Qos
Security
COST
Criteria Network 1 Network 2 Network 3
Bandwidth 0.65 0.57 0.50
Qos
Security
COST
Standardized decision matrix….
Criteria Network 1 Network 2 Network 3
bandwidth 0.65 0.57 0.50
QoS
SECURITY
COST
Criteria Network 1 Network 2 Network 3
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
Standardized decision matrix….
Similarly….
Steps involved in TOPSIS…• Step 2 - Construct weighted standardized decision matrix
by multiplying attributes weight to each rating.
Criteria Network 1 Network 2 Network 3
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
Criteria Network 1 Network 2 Network 3
Bandwidth 2.6Qos
Security
COST
Attributes weights
Weighted Standardized decision matrix
X
Standardized decision matrix
Steps involved in TOPSIS…
Criteria Network 1 Network 2 Network 3
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
Criteria Network 1 Network 2 Network 3
Bandwidth 2.6 2.28Qos
Security
Cost
Attributes weights Standardized decision matrix
X
Weighted Standardized decision matrix
• 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
by multiplying attributes weight to each rating.
Criteria Network 1 Network 2 Network 3
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
Criteria Network 1 Network 2 Network 3
bandwidth 2.6 2.28Qos 1.1Securit
Cost
Attributes weights Standardized decision matrix
X
Weighted Standardized decision matrix
Criteria Network 1 Network 2 Network 3
bandwidth 2.6 2.28QoS 1.1SECURITY
COST
Steps involved in TOPSIS…• Step 2 - construct weighted standardized decision matrix
by multiplying attributes weight to each rating.
Criteria Network 1 Network 2 Network 3
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….
Weighted Standardized decision matrix
Criteria Network 1 Network 2 Network 3
bandwidth 2.6 2.28QoS 1.1SECURITY
COST
Steps involved in TOPSIS…• Step 2 - construct weighted standardized decision matrix
by multiplying attributes weight to each rating.
Criteria Network 1 Network 2 Network 3
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….
Weighted Standardized decision matrix
Steps involved in TOPSIS…• Step 3 – Determine ideal solution and negative ideal solution.
Criteria Network 1 Network 2 Network 3
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.
Criteria Network 1 Network 2 Network 3
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
Criteria Network 1 Network 2 Network 3
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.
Criteria Network 1 Network 2 Network 3
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
Criteria Network 1 Network 2 Network 3
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.
Criteria Network 1 Network 2 Network 3
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
Criteria Network 1 Network 2 Network 3
Bandwidth 1 .88 .77
Qos .875 .875 1
Security .66 1 .66
COST 1 .857 .857
Steps involved in SAW…
Criteria Network 1 Network 2 Network 3
bandwidth 1 0.88 0.77
QoS 0.875 0.875 1
Security 0.66 1 0.66
Cost 1 0.857 0.857
Criteria Network 1 Network 2 Network 3
Bandwidth 4 3.52Qos
Security
Cost
Attributes weights Standardized decision matrix
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….
Criteria Network 1 Network 2 Network 3
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.
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