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Solving State Explosion Problem in Analytical Modeling of Next Generation Wireless Systems (NGWS): A Layered Approach
H. Birkan Yılmaz
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OUTLINE
• INTRODUCTION• NGWS DESIGN GOALS
• NGWS DEFINITIONS & NOTATIONS• AREA DEFINITION
• NEXT GENERATION CALL ADMISSION CONTROL (NGCAC)
• WHAT WE DID• WHAT WE ARE DOING• NUMERICAL RESULTS• FUTURE WORK
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INTRODUCTION
• NGWS incorporate multiple subsystems• PCS, WLAN, WiMAX, Satellite, ...• High bandwidth• Nomadic access
• Concept of integrating two or more communication systems is already in use
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LITERATURE SURVEY
• Akyildiz et. al.• AdapNet: An Adaptive Protocol Suite• Boundary Location Register
• Priscoli• Interworking of a Satellite System With the Terrestrial Networks
• Signaling Issues• Functional organization of the described interface
• Buddhikot et. al.• WLAN/CDMA2000 Interworking
• Ghaheri-Niri and Tafazolli• Cordless Cellular Network Integration for the 3rd Generation Personal
Communication Systems
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NGWS DESIGN GOALS
• Support for the “best” network selection
• Mechanism to ensure high-quality and security
• Seamless inter-system mobility
• Scalable architecture (any # of wireless systems)
• QoS provisioning
IP is recognized to become the core part of NGWS to support ubiquitous communication
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EXAMPLE INTERCONNECTION
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NGWS DEFINITIONS & NOTATIONS
• NGWS = (, HR) is the set of subsystems• HR is the global home register
• The ith access node of subsystems s is denoted by
• The set of all access nodes is denoted by
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SELECTION OF SUBSYSTEMS
• a
• a
• a
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AREA DEFINITION
• Classical wireless systems• Service area is split into cells
• NGWS• Multiple subsystems serving service area• Differentiate service area wrt accessible subsystems• Areas
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AREA EXAMPLE
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AREA PARAMETERS
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NEXT GENERATION CALL ADMISSION CONTROL (NGCAC)
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WHAT WE DID
• We derived transition probabilities in the first analytical model of NGWS
• State space explodes (Simple Topology)• 65 944 160 601 201 states• 8 962 362 486 784 effective states
• We assumed “The system operates in last three ‘layers’”
• Results can be found in• Tuna Tugcu, H. Birkan Yilmaz, and Feodor Vainstein, “Analytical
Modeling of CAC in Next Generation Wireless Systems”, Computer Networks, vol. 50, no. 17, pp. 3466 - 3484, December 2006.
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WHAT WE ARE DOING
• AVERAGE LAYER FLOW APPROXIMATION (ALFA)• Idea
• Introduce “layer” concept and represent states in a layer with one state
• Consider markov chain• Approximate “flow” between layers
• Not necessary to create all states (infeasible)• Randomly create states from a layer and approximate layer out flow
(feasible)• Solve by power method (Iteration)
• More complex scenarios are possible
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NUMERICAL RESULTS
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NUMERICAL RESULTS cont’d
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NUMERICAL RESULTS cont’d
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FUTURE WORK
• Confidence Intervals for ALFA Approximation
• Differentiating “homogeneous states” in layers (ALFA2) and adding new metric for quality of the network
• New NGCAC scheme (load balancing)
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QUESTIONS