Bandwidth Allocation and Recovery for Uplink Access in IEEE 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 Outline Introduction The UBAR protocol Simulations Conclusion
3 Introduction The PMP defined in IEEE Consist of BS and SSs All connections need to go through the BS Uplink Downlink TDD mode
4 Introduction Fig. 1
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 Introduction A. Challenges on Uplink Access At the MAC layer, each connection a single service flow type a set of QoS parameters defines four service flows types: UGS (unsolicited grant service) rtPS (real-time polling service) nrtPS (nonreal-time polling service) BE (best effort).
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 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 Introduction A. Challenges on Uplink Access Fig. 1
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 Introduction B. Our Contributions The bandwidth waste problems do not take into consideration before uplink bandwidth allocation and recovery (UBAR) protocol
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 The UBAR protocol The UBAR protocol : Admission control procedure Bandwidth allocation procedure Bandwidth recovery procedure
14 The UBAR protocol A. Admission Control and Bandwidth Allocation DSA-REQ and, SF : service flow type Note: = = 0 =, = 0, set > >, =
15 The UBAR protocol A. Admission Control and Bandwidth Allocation
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 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 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 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 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 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 The UBAR protocol B. Bandwidth Recovery
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 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 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 The UBAR protocol B. Bandwidth Recovery B 3 : IF S>0 K: number of BE SSs in the L
27 The UBAR protocol B. Bandwidth Recovery B 4 : IF S<0 BS removes that SS j form the remaining polling list
28 The UBAR protocol B. Bandwidth Recovery
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 The UBAR protocol B. Bandwidth Recovery
31 The UBAR protocol B. Bandwidth Recovery padding waste problem
32 Simulations
33 Simulations
34 Simulations
35 Simulations
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 T hank you