1. Bandwidth Allocation and Recovery for Uplink Access in IEEE 802.16 Broadband Wireless Networks Zi-Tsan Chou & Yu-Hsiang Lin Networks and Multimedia Institute Institute for Information Industry, Taipei, Taiwan VTC 2007 © Chan-Ying Lien

2. 2 Outline Introduction The UBAR protocol Simulations Conclusion

3. 3 Introduction The PMP defined in IEEE 802.16  Consist of BS and SSs  All connections need to go through the BS Uplink Downlink TDD mode

4. 4 Introduction Fig. 1

5. 5 Introduction Fig. 1 In Fig. 1(a), the UL-MAP specifies (SS 1, t 1, x 1 ), (SS 2, t 2, x 2 ), (SS 3, t 3, x 3 ), (EoM,t 4, 0) EoM = End of MAP t i+1 = t i + x i, 1 < i < 3

6. 6 Introduction A. Challenges on Uplink Access At the MAC layer, each connection  a single service flow type  a set of QoS parameters 802.16 defines four service flows types:  UGS (unsolicited grant service)  rtPS (real-time polling service)  nrtPS (nonreal-time polling service)  BE (best effort).

7. 7 Introduction A. Challenges on Uplink Access SSBS DSA-REQ DSA-RSP DSA-ACK QoS requirements Resource enough Allocate UL-burst -bandwidth demand -QoS requirements

8. 8 Introduction A. Challenges on Uplink Access Noise is unavoidable in wireless networks The noise source is close to the BS  Idling UL-subframe problem The noise sources are close to some SSs  uplink hole problem

9. 9 Introduction A. Challenges on Uplink Access Fig. 1

10. 10 Introduction A. Challenges on Uplink Access The granted transmission duration x i for SS i is much larger than its current demand d i  padding waste problem maximum padding MPDU: 2041 bytes

11. 11 Introduction B. Our Contributions The bandwidth waste problems do not take into consideration before uplink bandwidth allocation and recovery (UBAR) protocol

12. 12 Introduction B. Our Contributions UBAR protocol  Differentiated admission control scheme  Dynamic bandwidth allocation scheme  Timeout-based UL-MAP retransmission scheme  Bandwidth recovery scheme

13. 13 The UBAR protocol The UBAR protocol :  Admission control procedure  Bandwidth allocation procedure  Bandwidth recovery procedure

14. 14 The UBAR protocol A. Admission Control and Bandwidth Allocation DSA-REQ  and, SF : service flow type  Note: = = 0  =, = 0,  set > >, =

15. 15 The UBAR protocol A. Admission Control and Bandwidth Allocation

16. 16 The UBAR protocol A. Admission Control and Bandwidth Allocation The admission control scheme of UBAR guarantees that the SS i with the service flow type SF can reserve at least the channel time δ i △ = T prm + STTG

17. 17 The UBAR protocol A. Admission Control and Bandwidth Allocation Let U max : maximum length of UL-burst period L = {SS 1, SS 2, · · ·, SS k } When SS j sends the DSA-REQ to the BS  δ j + δ i ≤ U max

18. 18 The UBAR protocol A. Admission Control and Bandwidth Allocation Bandwidth allocation procedure  A1. Let σ i = Δ + ( HR + BR +β i ) / C and x i := min{σ i, δ i } for all 1 ≤ i ≤ k  A2.  A3.

19. 19 The UBAR protocol A. Admission Control and Bandwidth Allocation Bandwidth allocation procedure  A2. Let RCT := U max − x i and y i = x i − △ − ( HR + BR ) / C for all 1 ≤ i ≤ k  If the remaining channel time RCT is greater than zero, then

20. 20 The UBAR protocol A. Admission Control and Bandwidth Allocation Bandwidth allocation procedure  A3. Let RCT := U max − x i  If the remaining channel time RCT is still greater than zero, then

21. 21 The UBAR protocol B. Bandwidth Recovery After performing the bandwidth allocation procedure, the BS will broadcast the UL-MAP message:  [(SS 1, t 1, x 1 ), · · ·, (SS k, t k, x k ), (EoM,t k+1, 0)] Once the idle channel time exceeds the timeout threshold h 1  UL-MAP is injured  SS 1 cannot correctly decode the UL-MAP The new UL-MAP may or may not include SS 1

22. 22 The UBAR protocol B. Bandwidth Recovery

23. 23 The UBAR protocol B. Bandwidth Recovery Two bandwidth recovery schemes  R 1 : The unused channel time of SS 1 is shared with other residual SSs on the polling list  R 2

24. 24 The UBAR protocol B. Bandwidth Recovery R 1  BS calculates the sharable channel time S = x 1 − h 1 − h 2, h 1 = τ h 2 = T proc + T UM + STTG + τ  Resend UL-MAP

25. 25 The UBAR protocol B. Bandwidth Recovery B 1 : Denote the remaining polling list B 2 : If S = X i – h 1 – h 2 >0

26. 26 The UBAR protocol B. Bandwidth Recovery B 3 : IF S>0 K: number of BE SSs in the L

27. 27 The UBAR protocol B. Bandwidth Recovery B 4 : IF S<0 BS removes that SS j form the remaining polling list

28. 28 The UBAR protocol B. Bandwidth Recovery

29. 29 The UBAR protocol B. Bandwidth Recovery R 2  C 1 : If SS i does not respond to the UL-MAP, And S = x i − h 1 − h 2 < Δ + BR / C, BS gives up resending the UL-MAP Otherwise, goto C 2  C 2 : BS allocates that unused sharable channel time S to the most over-demanded SS on the remaining polling list L

30. 30 The UBAR protocol B. Bandwidth Recovery

31. 31 The UBAR protocol B. Bandwidth Recovery padding waste problem

32. 32 Simulations

33. 33 Simulations

34. 34 Simulations

35. 35 Simulations

36. 36 Conclusion Three bandwidth-waste problems The UBAR protocol  Differentiated admission control scheme  Dynamic bandwidth allocation scheme  Timeout-based UL-MAP retransmission scheme  Bandwidth recovery scheme Simulation results

37. 37 T hank you