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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

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
Outline
  • Introduction
  • Network Model
  • Adaptive Hierarchical Polling Approach
    • Hierarchical polling mechanism
    • Cost-based call admission control
  • Numerical Result and Conclusion
introduction
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
802 16 frame structure
802.16 Frame Structure

a shorter contention period brings longer length for data transmission but causes higher collision probability

research goal
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
unicast polling delay
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
fractional reward loss
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

adaptive hierarchical polling approach
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
the adaptive hierarchical polling scheduling
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

cost based cac 1 3
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.

cost based cac 2 3
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.

cost based cac 3 3
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

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