1. Opportunistic Fair Scheduling for the Downlink of 802.16Wireless Metropolitan Area Networks Mehri Mehrjoo, Mehrdad Dianati, Xuemin (Sherman) Shen, and Kshirasagar Naik Department of Electrical and Computer Engineering University of Waterloo, Ontario, Canada The Third International Conference on Quality of Service in Heterogeneous Wired/Wireless Networks(QShine’06)

2. Outlines  Introduction  Opportunistic Fair Scheduling Scheme  Simulation  Conclusion

3. Introduction_ 802.16(1)  Defines two transmission mode Point-to-MultiPoint (PMP) mode Mesh mode  PMP mode is designed for high rate transmission service with support of various QoS Require all SSs to be with clear LOS

4. Introduction_ 802.16(2)  Four service flows have been defined ： Unsolicited Grant Service (UGS) Real-time Polling Service (rtPS) Non-real-time Polling Service (nrtPS) Best Effort (BE) service

5. Opportunistic Fair Scheduling Scheme_ motive  an optimal scheduling policy is to transmit to SSs with the best channel quality at the maximum achievable rates in each scheduling interval and cause unfairness  a fairness mechanism is deployed to assign bandwidth to each SS according to its history of transmission and average channel quality

6. Opportunistic Fair Scheduling Scheme_ (1) Assume that can achieve a transmission rate of Shannon ’ s upper bound and there are N nodes average power gain of the channel allocated power to SS j R j is the allocated rate to SS j The total power budget of the BS

7. Opportunistic Fair Scheduling Scheme_ (2)nonlinear optimization

8. Opportunistic Fair Scheduling Scheme_ (3)utility function is the weighted minimum average rate is the weighted maximum average rate is the weighted rate is the rate allocation vector R j is the allocated rate to SS j

9. = Opportunistic Fair Scheduling Scheme_ (3)utility function ++

11. Opportunistic Fair Scheduling Scheme_ (4)the fair of scheduling Fair share weight, denoted by ( ) as follows: Approximately utility fair allocation :

12. Simulation_ (1)

13. Simulation_ (2)

14. Simulation_ (3)

15. Simulation_ (4)Gini fairness index If I=0,mean perfect fairness and are the long term average transmission rate and the fair share weight of SS k

16. Simulation_ (4)

17. Simulation_ (5)

18. Conclusion  A fairness enforcement mechanism can maintain long term fairness and smooth service delivery  It takes advantage of the temporary variations of a fading channel to improve the overall throughput