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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
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2 Outline Introduction The UBAR protocol Simulations Conclusion
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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
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4 Introduction Fig. 1
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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
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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).
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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
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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
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9 Introduction A. Challenges on Uplink Access Fig. 1
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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
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11 Introduction B. Our Contributions The bandwidth waste problems do not take into consideration before uplink bandwidth allocation and recovery (UBAR) protocol
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12 Introduction B. Our Contributions UBAR protocol Differentiated admission control scheme Dynamic bandwidth allocation scheme Timeout-based UL-MAP retransmission scheme Bandwidth recovery scheme
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13 The UBAR protocol The UBAR protocol : Admission control procedure Bandwidth allocation procedure Bandwidth recovery procedure
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14 The UBAR protocol A. Admission Control and Bandwidth Allocation DSA-REQ and, SF : service flow type Note: = = 0 =, = 0, set > >, =
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15 The UBAR protocol A. Admission Control and Bandwidth Allocation
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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
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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
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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.
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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
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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
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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
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22 The UBAR protocol B. Bandwidth Recovery
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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
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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
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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
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26 The UBAR protocol B. Bandwidth Recovery B 3 : IF S>0 K: number of BE SSs in the L
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27 The UBAR protocol B. Bandwidth Recovery B 4 : IF S<0 BS removes that SS j form the remaining polling list
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28 The UBAR protocol B. Bandwidth Recovery
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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
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30 The UBAR protocol B. Bandwidth Recovery
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31 The UBAR protocol B. Bandwidth Recovery padding waste problem
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32 Simulations
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33 Simulations
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34 Simulations
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35 Simulations
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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
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37 T hank you
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