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

1. Adaptive Hierarchical Polling and Cost-Based Call Admission Control in IEEE 802.16 WiMAX Networks Ben-Jye Chang, Yan-Ling Chen, Chien-Ming Chou WCNC 2007

2. Outline • Introduction • Network Model • Adaptive Dynamic Polling Approach • Numerical Result • Conclusion

3. Introduction • Unicast polling in IEEE 802.16 • Advantages • Guaranteeing the required bandwidth • Overcoming the access collisions among all SSs • Disadvantages • Long polling delay • Bandwidth waste • IEEE 802.16 does not consider the delay and resource waste

4. Introduction • Goal • Increase the utilization of access channel • Reduce polling delay • Overcome the access collisions among all SSs • Guarantee the higher priority SS • Shorter delay • More bandwidth allocation

5. W=(V,E)  V: a set of mobile STA with the same transmission range E: a set of wireless link VBS = 2 = 5 System Model Cap(2)= 10 Mbps Node ID Group Index Cap(1)= 5 Mbps Cap(3)= 15 Mbps Subscriber station Node Priority G={A, B} Group A Group B

6. System Model • K classes of traffic • Class 1 represents the lowest class traffic • Class K represents the highest class traffic

7. System Model • Contention-based bandwidth request • Multicast and broadcast polling • The ranges of contention window of different node priority are various • Higher-class traffic  Smaller contention window and prior to be allocated bandwidth • Lower-class traffic  Bigger contention window Contention Window of higher priority Contention Window of lower priority Contention-based bandwidth request Interval

8. System Model • Worst CaseSuppose BS polled each SS at DL subframe time for SS to require bandwidth • Polling Delay VBS Tf : frame duration Number of Node increase Polling delay increase No QoS requirement

9. : The reward of node class r with service class k : The arrival rate of node class r with rtPS services : The blocking of node classr with service class k System Model • Three performance metrics • Average polling delay • Bandwidth utilization • Fractional Reward Loss (FRL) • Weighted blocking probability • The reward of a high class required call should be higher than the reward of a low class required call Minimize Fractional Reward Loss !!

10. Adaptive Dynamic Polling Approach • Two primary functionalities • Hierarchical Polling mechanism • Guarantee high-priority nodes can be polled prior to low-priority nodes • Cost-based Call Admission Control (CAC) • Maximize network reward

11. Hierarchical Polling mechanism-Level 1 • Nodes are classified as several priorities • Access cost • Customer class • Distance of BS • Polling scheduling • Per Node • Among different node priority • Weighted round robin SSs Priority The weight of Priority 1 node

12. Hierarchical Polling mechanism-Level 2 • Polling scheduling • Per connection • Priority • UGS>rtPS>nrtPS>BE

13. Hierarchical Polling mechanism-Level 1 & Level 2

14. Cost-based Call Admission Control • Purpose • Make finite wireless resource be utilized more efficient • Allocate high-priority node and high-class service flow first • How • Cost function design

15. Cost-based Call Admission Control • COL (Competitive On-Line) • The cost of carrying a call on a node l with occupancy Capacity of the link Wi(i) < ρ  A path is admissible Constant parameter

16. Cost-based Call Admission Control • Let = ρ

17. Cost-based Call Admission Control • The node cost for class k call The required bandwidth of class k

18. Numerical Results

19. Numerical Results

20. Numerical Results

21. Conclusion • Adaptive hierarchical polling with a COL cost-based CAC mechanism has been proposed • Increase the network reward from high priority nodes • Reduces the average polling delay of rtPS and nrtPS service flow