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Adaptive Hierarchical Polling and Cost-based Call Admission Control in IEEE 802.16 WiMAX Networks

Adaptive Hierarchical Polling and Cost-based Call Admission Control in IEEE 802.16 WiMAX Networks. Ben-Jye Chang, Yan-Ling Chen and Chien-Ming Chou IEEE Wireless Communications & Networking Conference (WCNC) 2007. 報告者：李宗穎. Outline. Introduction Network Model

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Adaptive Hierarchical Polling and Cost-based Call Admission Control in IEEE 802.16 WiMAX Networks

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  1. Adaptive Hierarchical Polling and Cost-based Call Admission Control in IEEE 802.16 WiMAX Networks Ben-Jye Chang, Yan-Ling Chen and Chien-Ming Chou IEEE Wireless Communications & Networking Conference (WCNC) 2007 報告者：李宗穎

  2. Outline • Introduction • Network Model • Adaptive Hierarchical Polling Approach • Hierarchical polling mechanism • Cost-based call admission control • Numerical Result and Conclusion

  3. Introduction • For minimizing collisions due access contention, IEEE 802.16 thus adopted a polling access mechanism for BS to polling all SSs in turn • long polling delay • inefficient channel allocation

  4. 802.16 Frame Structure a shorter contention period brings longer length for data transmission but causes higher collision probability

  5. Research Goal • The proposed two-level polling mechanism includes the Node Priority (NP) level and the service flow level scheduling mechanism • To overcome the access collisions among all SSs • To guarantee the higher priority SS obtaining shorter delay and more bandwidth allocation

  6. The unicast and multicast polling in a WiMAX network

  7. Unicast Polling Delay • the unicast polling delay Tpu increases while the number of SSs increasing and may cause not to meet the delay bound of real-time services • Tpu = |Vss|Tf where Tfis a frame duration

  8. Fractional Reward Loss • Fractional Reward Loss can be viewed as weighted blocking probability in which a call is given a weight based on its reward RWr,k : The reward of node class r with service class k λr,k : The arrival rate of node class r with rtPS services Br,k : The blocking of node class r with service class k

  9. Adaptive Hierarchical Polling Approach • Hierarchical Polling mechanism • guarantees high-priority nodes can be polled prior to low-priority nodes • Cost-based Call Admission Control (CAC) • maximize network reward

  10. The adaptive hierarchical polling scheduling Weight Round Robin Such a quality of service (QoS) mechanism only brings the service reward rather than the node reward from high priority nodes

  11. Hierarchical polling mechanism High Priority

  12. Cost-based CAC (1/3) • The characteristic of the Competitive On-Line (COL) [7][8] cost function is increased exponentially as the residual bandwidth decreases i : occupancy bandwidth with node l δ : denotes a chosen constant parameter C l : represents the capacity of the link [7] R. H. Hwang, W. C. Hsiao and B. J. Chang, “Multiple Classes of QoS guarantee in distributed Multicast routing,” The 6th International Conference on Advanced Communication Technology, vol. 2, pp.949–954, Feb. 2004. [8] Ben-Jye Chang and Ying-Hsin Liang, “Analysis of OVSF Code Tree for Code Assignment in WCDMA Cellular Communications,” IEEE/ACM MASCOTS 2004, Oct. 2004.

  13. Cost-based CAC (2/3) • Allan and El-Yaniv [10] suggested setting ρ to δ . Meanwhile, Zhang et al. [11] indicated that if δ =ρ , this is equivalent to setting the admission threshold to one and the cost of a node with occupancy i to Admissible ρ Since 0 ≤ i ≤ Cl, we have 0 ≤Wl(i)≤1 [10] Borodin Allan and Ran El-Yaniv, “Online computation and competitive analysis,” Cambridge University Press, 1998. [11] L. Zhang, M. Andrews, W. Aielo, S. Bhatt, and K. R. Krishnan, “A Performance Comparison of Competitive On-line Routing and State-Dependent Routing,” GLOBECOM’97, pp. 1813-1819, Nov. 1997.

  14. Cost-based CAC (3/3) • the cost function for analyzing dynamic update schemes to adapt to dynamic traffic loads in a QoS-based hierarchical networks. The node cost for class k call, plk(i) , are defined herein by where bkis the required bandwidth of class k priority r will be accepted when the reward of it, RWr,k , is larger than the COL cost

  15. FRL of different number of node priorities under various arrival rates

  16. Average polling delay of different approaches under various number of nodes

  17. Conclusion • Paper propose an adaptive hierarchical polling with a COL cost-based CAC mechanism. • increases the network reward from high-priority nodes and thusminimizes FRL • reduces the average polling delay of rtPS and nrtPS service flows

  18. Comments • Theoretical proof is not enough • Admission threshold adaptive • Classify group • Reward value for each priority node/class • Adaptive contention window range value

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