1. Channel Access Delay Analysis of IEEE 802-16 Best Effort Services Hossein Ghaffarian, Mahmood Fathy, Mohsen Soryani Dept. of Computer Engineering Iran University of Science and Technology, Tehran-Iran IEEE Infocom 2008

2. Outline Introduction IEEE 802.16 Best Effort Service Mechanism Analytical Model of Best Effort Service Simulation Results Conclusions 2

3. Introduction Four types of service Unsolicited Grant Service (UGS) Real-time Polling Service (rtPS) Non-real-time Polling Service (nrtPS) Best Effort service (BE) 3

4. Introduction -Motivation Implementations of four types in IEEE 802.16 networks are very costly Wibro only supports Best Efforts services Related work Performance analysis via simulations results IEEE 802.16 PMP mode IEEE 802.16 Mesh mode IEEE 802.11 4

5. Introduction -Goal Channel access delay of IEEE 802.16 BE services Analytical model for delay in BE service 5

6. IEEE 802.16 Best Effort Service Mechanism Two types of request mechanism Stand alone bandwidth request mechanism Incremental request Aggregate request Piggybacking bandwidth request mechanism Incremental request 6

7. IEEE 802.16 Best Effort Service Mechanism Bandwidth contention period 7 Ranging Request Opportunities Bandwidth Request Opportunities Uplink Data Bandwidth Request Opportunity 01 Bandwidth Request Opportunity N …….. Uplink Subframe

8. IEEE 802.16 Best Effort Service Mechanism Collision avoidance Contention resolution process Request backoff start vs. Request backoff start The SS shall randomly select a value from (0, 2 Requestbackstart ) The number of contention transmission opportunities that the SS shall defer before an eligible transmission 8 Ex: Request backoff start = 4  The range of backoff = (0,15) Value = 2  Differ 2 transmission opportunities BR Opportunity 1 BR Opportunity 2 BR Opportunity 3 BR Opportunity N ……..

9. Analytical Model of Best Effort Service -Basic Measurements 9 Current value of backoff window of node i Backoff stage  Retry count The minimum value of backoff window of node i Retry limit

10. Analytical Model of Best Effort Service -Basic Measurements The probability of TXOP 1 selected by one SS is 1/5 C i : The number of connections in node i P s,i :The probability of a successful request in node i 10 BR TXOP 1 BR TXOP 2 BR TXOP 3 BR TXOP 4 BR TXOP 5

11. Analytical Model of Best Effort Service -Basic Measurements 11

12. Analytical Model of Best Effort Service -Transmission Saturation Delay 12 Backoff stage  Retry count Failure Conditions Successful Condition

13. Analytical Model of Best Effort Service -Transmission Saturation Delay 13

14. Analytical Model of Best Effort Service -Transmission Saturation Delay 14

15. Analytical Model of Best Effort Service -Transmission Saturation Delay 15

16. Analytical Model of Best Effort Service -Transmission Saturation Delay

17. 17

18. Analytical Model of Best Effort Service -Transmission Saturation Delay 18

19. Simulation Results 19

20. Simulation Results 20

21. Simulation Results 21

22. Simulation Results 22

23. Simulation Results 23

24. Simulation Results 24

25. Simulation Results 25

26. Simulation Results 26

27. Simulation Results 27

28. Conclusions This paper proposes an a nalytical model for delay in BE service Transmission Markov model Analytical results The best condition: BW min = FrameOpp 28