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H. Birkan Yılmaz yilmhuse@boun.tr

Solving State Explosion Problem in Analytical Modeling of Next Ge neration Wireless Systems (NGWS) : A Layered Approach. H. Birkan Yılmaz yilmhuse@boun.edu.tr. OUTLINE. INTRODUCTION NGWS DESIGN GOALS NGWS DEFINITIONS & NOTATIONS AREA DEFINITION

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H. Birkan Yılmaz yilmhuse@boun.tr

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  1. Solving State Explosion Problem in Analytical Modeling of Next GenerationWireless Systems (NGWS): A Layered Approach H. Birkan Yılmaz yilmhuse@boun.edu.tr

  2. 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

  3. 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

  4. 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

  5. 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

  6. EXAMPLE INTERCONNECTION

  7. 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

  8. SELECTION OF SUBSYSTEMS • a • a • a

  9. AREA DEFINITION • Classical wireless systems • Service area is split into cells • NGWS • Multiple subsystems serving service area • Differentiate service area wrt accessible subsystems • Areas

  10. AREA EXAMPLE

  11. AREA PARAMETERS

  12. NEXT GENERATION CALL ADMISSION CONTROL (NGCAC)

  13. WHAT WE DID • We derived transition probabilities in the firstanalytical 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.

  14. 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

  15. NUMERICAL RESULTS

  16. NUMERICAL RESULTS cont’d

  17. NUMERICAL RESULTS cont’d

  18. 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)

  19. QUESTIONS

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