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Dynamic Bandwidth Allocation for 802.16E-2005 MAC

Dynamic Bandwidth Allocation for 802.16E-2005 MAC. Speaker ：黃筱婷 Date ： 2010/10/22. Two-Phase Proportionating. Bandwidth Allocation scheme. Conclusion. Simulation. Overview of the MAC Protocol. Introduction. Outline. IEEE 802.16 Deployment. GPC and GPSS. Grand Per Connection(GPC)

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Dynamic Bandwidth Allocation for 802.16E-2005 MAC

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  1. Dynamic Bandwidth Allocation for 802.16E-2005 MAC Speaker：黃筱婷 Date：2010/10/22

  2. Two-Phase Proportionating Bandwidth Allocation scheme Conclusion Simulation Overview of the MAC Protocol Introduction Outline

  3. IEEE 802.16 Deployment

  4. GPC and GPSS • Grand Per Connection(GPC) • Not flexible for SSs to be adaptive to connections of real-time applications. • Not supported by the standard. • Grand Per Subscriber Station(GPSS) • BS grants requested bandwidth to each SS. • SS can flexibly respond to different QoS requirements of the connections.

  5. Receiving entity(ex: BS) Sending entity(ex: SS) SDU SDU PDU PDU Wireless channel IEEE 802.16 Protocol Model

  6. TDD V.S. FDD • Time-Division Duplex(TDD) • Frequency-Division Duplex(FDD)

  7. Two-Phase Proportionating Bandwidth Allocation scheme Conclusion Overview of the MAC Protocol Simulation Introduction Outline

  8. QoS Architecture for IEEE 802.16 MAC Protocol

  9. Frame Structure for TDD System

  10. OFDMA • Orthogonal Frequency-Division Multiple Access (OFDMA) • Multi-user version of the popular Orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. • Advantage: highly suitable for broadband wireless networks, scalability, MIMO-friendliness, and ability to take advantage of channel frequency selectivity.

  11. OFDMA Mapping • Subchannel allocation in the DL may be performed in the following ways: • FUSC(Full Usage of Subchannels) • PUSC(Partial Usage of Subchannels) • For DL/UL FUSC, one slot is one subchannel by one OFDMA symbol. • For DL PUSC, one slot is one subchannel by two OFDMA symbols. • For UL PUSC, one slot is one subchannel by three OFDMA symbols.

  12. priority 高 低 QoS Classes

  13. Two-Phase Proportionating Bandwidth Allocation scheme Conclusion Simulation Overview of the MAC Protocol Introduction Outline

  14. Deficit Round Robin(DRR) • 每個data flow會有一初始值為零的deficit counter • 依序檢視並嘗試傳送封包前，先檢查該data flow最前面的封包大小是否小於等於deficit counter內的值 • 是:傳送出去，並將deficit counter扣掉此封包的大小，重覆執行此步驟直到該data flow最前面的封包大小已超過欠額計數器內的值再換下一個data flow被服務 • 否:不傳送，把該deficit counter累加上一個固定數值(quantum)，等待下一輪再被服務

  15. Deficit Fair Priority Queue(DFPQ) • 結合Deficit Round Robin(DRR) and priority，限制某類資料流在一個frame中能夠傳送的資料量，與不同類資料流之間以priority方式進行頻寬配置。 • 在使用DFPQ前須對連線種類及方向做優先權分類，其區分規則為rtPS>nrtPS>BE，Downlink>Uplink。 • Quantum size：rmax(i,j)為the Maximum Sustained traffic rate of the jth connection in the ith class of service flow

  16. DFPQ(cont.)

  17. Strict Priority(SP) • Packets in higher priority queues always transmit before packets in lower priority queues. • A lower priority queue has a chance to transmit packets only when there are no packets waiting in a higher priority queue.

  18. Two-Phase Proportionating Bandwidth Allocation scheme Conclusion Introduction Overview of the MAC Protocol Simulation Outline

  19. MAC Protocol

  20. Overview of the Algorithm • IEEE802.16 頻寬配置的目標是確實填滿整個TDD time frame，但是uplink跟downlink subframe的比例是可以動態調整的。 • 此演算法分為兩個階段。第一個階段根據SS之DL與UL的要求來決定subframe sizes的大小 • 第二個階段是根據的QoS參數(ex: weight, 反映實際需求的調節因子 A-factor)來分配頻寬給每個不同連線的queue。 • Finally the TPP adheres to the GPSS by granting SSs the allocated bandwidth of each queue.

  21. TWO-PHASE PROPORTIONATING

  22. Bandwidth Translation and Slot Dispatching • 在BS從backbone network收到data traffic或收到uplink bandwidth request後，TPP就會先把所要求的頻寬(bytes)轉換成OFDMA的slots，因為slot是PHY傳輸的基本單位。 • 這些slot被分配給相對應的service queue，包括了五種uplink classes with/o latency guarantee。 • 每個queue使用三個變數： • the bandwidth request slots (BRQ)，用來計算request slots的個數 • Rmax，計算Maximum sustained traffic rate (MSTR) • Rmin，計算minimum reserved traffic rate (MRTR)

  23. First Phase • Goal : Dividing a Frame into Downlink and Uplink Subframes • UR and DR : the BRQ of the uplink and downlink. • S : # of symbols in a frame.

  24. Second Phase • Goal : Allocating Subframes to Queues. • Rminof all queues are firstly satisfied for minimum slots guarantee, followed by the proportionating of the remaining slots to queues except the UGS and ertPS whose requested slots are already served. • In order to avoid bandwidth waste and starvation, we use an adjustment factor(A-factor)= • The remaining slots are therefore allocated according to the following proportion

  25. Example • For Phase 1： • UR = 60, DR = 40, S=26   x = 3, indicating 6x/3 = 6 slot columns for uplink while (26-6x)/2 = 4 slot columns for downlink. If we use direct proportion, however, the number of symbols for uplink is 26×[60 /(60 + 40)] ≅ 16, in which only 15 symbols are effective. • For Phase 2：

  26. Two-Phase Proportionating Bandwidth Allocation scheme Conclusion Simulation Overview of the MAC Protocol Introduction Outline

  27. Simulation Setup • One BS serving 20SSs, and 2 remote stations including an FTP server and voice end point. • 5 service classes are supported and each class involves 4 SSs. • UL and DL channel capacity is 10.24 Mbps and the frame duration is 5ms. • Rmax of rtPS, nrtPS and BE are 8,6, and 4, respectively, while Rmin are 4,2, and 1, respectively.

  28. Subframe Allocation: Static vs. Dynamic • The FTP traffic load of the downlink is 3 times of the link. • By stealing the unused uplink slot columns for the downlink, TPP improves the overall link utilization from 75% to 96%.

  29. Effectiveness of the A-Factor • Grant Ratio =  If Grant Ratio >1, resulting bandwidth waste. • In BE, is not feasible because it tends to favor classes with a small Rmin which oftentimes is BE, and therefore violates the spirit of service differentiation.

  30. Service Differentiation

  31. Bandwidth Utilization • From the figure we can learn that the bandwidth utilizations of the three algorithms increase linearly but start to decrease when hitting a certain level: 85.5% for TPP, 80.6% for DFPQ and 68.4% for SP.

  32. Bandwidth Utilization(cont.) • Each class has an unused portion, which occurs during the translation from requested bytes to slots. Since the calculation, namely dividing the requested bytes by slot size, always rounds up, the resulted assignment is often larger than expected.

  33. Bandwidth Utilization(cont.) • Assuming that a slot contains 64 bytes, the # of requested slots is thus 4, causing 256 – 213 = 43 bytes waste. • TPP : breadth-firstly ; DFPQ :depth-firstly

  34. Two-Phase Proportionating Bandwidth Allocation scheme Conclusion Overview of the MAC Protocol Introduction Simulation Outline

  35. Conclusion • 這個方法考慮了IEEE 802.16中會出現的頻寬配置問題，所提出的TPP頻寬配置演算法能更好的利用頻寬資源並且支援service differentiation。 • 同時考慮了uplink和downlink的頻寬配置所以能夠動態的調整頻寬配置的內容。 • 模擬的結果證明了此演算法在第一階段能夠增加20%的頻寬利用率；並且在第二階段能夠適當的達到service differentiation。

  36. Future Work • 對各種排程方法做更深入的研究 • 在考量802.16網路有QoS效能並具有較佳的頻寬分配之下，找出合適的演算法。 • 利用Self-Similar的特性，找出最合乎現實狀況的的Traffic Model來做演算法的模擬及驗證。

  37. Reference [1] IEEE Std 802.16-2009 [2] Y. N. Lin, S. H. Chien, Y. D. Lin, Y. C. Lai, and M. Liu, "Dynamic Bandwidth Allocation for 802.16e-2005 MAC," in Current Technology Developments of WiMax Systems, edited by Maode Ma, Springer Netherlands, 2009, pp. 17-29. [3] A. Ganz, Z.Ganz and K.Wongthavarawat ,Multimedia Wireless Networks: Technologies, Standards, and QoS, Prentice Hall PTR, 2003, ch.7 [4] L. Nuaymi, WiMAX: Technology for Broadband Wireless Access, Wiley, 2007, ch.11 [5] K. Etemad, Overview of Mobile WiMAX Technology and Evolution, IEEE Communications Magazine, pp. 31-40, October 2008  [6] 林衣修. “一種基於 QoS 與 Overhead 考量之二維 OFDMA 配置方法 ”, 中央大學通訊所, July 2007

  38. Thank You ! Q&A

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