1 / 22

Hemant Kumar Rath, Abhijeet Bhorkar, Vishal Sharma Dept. of Electrical Engg., IIT-Bombay

An Opportunistic Uplink Scheduling Scheme to Achieve Bandwidth Fairness and Delay for Multiclass Traffic in Wi-Max (IEEE 802.16) Broadband Wireless Networks. Hemant Kumar Rath, Abhijeet Bhorkar, Vishal Sharma Dept. of Electrical Engg., IIT-Bombay {hemantr,bhorkar,vsharma@ee.iitb.ac.in}

alissa
Download Presentation

Hemant Kumar Rath, Abhijeet Bhorkar, Vishal Sharma Dept. of Electrical Engg., IIT-Bombay

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. An Opportunistic Uplink Scheduling Scheme to Achieve Bandwidth Fairness and Delay forMulticlass Traffic in Wi-Max (IEEE 802.16)Broadband Wireless Networks Hemant Kumar Rath, Abhijeet Bhorkar, Vishal Sharma Dept. of Electrical Engg., IIT-Bombay {hemantr,bhorkar,vsharma@ee.iitb.ac.in} IEEE Globecom – 2006 San Francisco, CA

  2. Motivation • Request-grant mechanisms, service types defined in std. • Request is either in Contention mode or Contention free (Polling) mode • Service types need QoS in terms of delay guarantees • Scheduling mechanisms are not defined • Scheduling in both uplink and downlink is open • Providers/vendors can have their own scheduling algos. • Scheduling mechanism must balance.... • Fairness in bandwidth alloc. with delay guarantees

  3. Motivation (cont’d) • Polling mode • Poll each SS in every frame or in every k frames • Polling interval k is a function of • Delay tolerance Td • UGS: 10ms, rtPS: 50ms, nrtPS: 200ms, BE: 500ms • Fairness measure • System efficiency • Provider selects k to balance efficiency & fairness • k may depend upon class of traffic

  4. SS1 BS SS3 SS4 SS2 Uplink Scheduling Scheme Requests Requests Grants Grants Requests Requests Grants Grants

  5. Optimum Polling Interval k • Polling mode • BS polls each SS every k frames • Worst case fairness is better if polled in every frame • Normalized delay is better if polled in some k frames • Design problem is to find an optimum k • Approach: Minimize weighted sum of • Normalized delay • Worst case fairness in bandwidth allocation

  6. SINR1 d1(t) SINR2 d2(t) SINRk BS dk(t) Opportunistic Scheduling q1(t) SS1 q2(t) SS2 Scheduler qk(t) SSk BS takes into account • Channel characteristics • Queue lengths • Delay counters at scheduling instant, based on COS

  7. Opportunistic Deficit Round Robin(O-DRR) • Channel is static in a frame interval • Slot assignment is opportunistic • Assign slots only if channel is good and flow is active • DRR variant for slot assignment • Use queue state, delay requirements and lag/lead info. • Works for single- and multi-class traffic • SS with large Td relinquishes resources to SS with small Td

  8. O-DRR Uplink Scheduling SS1 SS6 SS2 SS5 SS3 Scheduling Instant Scheduling Instant Scheduling Instant SS4 Tf kTf Scheduling Epoch Scheduling Epoch Scheduling Epoch

  9. Scheduling Multiclass Traffic • Number of slots assigned to an SS depends upon • Delay counter • How close a HOL packet is to its delay bound • Weight is more if it closer to the delay limit • Deficit counter • Weight is more if the deficit counter is high • Weights w •  1/delay counter •  deficit counter

  10. SS1 SS2 SS6 SS5 SS5 SS3 SS4 Tf SS3 kTf O-DRR Uplink Scheduling d1=10, d2=30, d3=25, d4=20 SS1 SS1=28, SS2=6, SS4=15, SS6=11 Schedule: weights (wi) and lag/lead counter Schedulable Set {SS1,SS2 ,SS4, SS6} Scheduling Epoch Eligible Set {SS1, SS2, SS4, SS6} SINRi > SINRth & Backlogged

  11. SS1 SS2 SS6 SS6 d1=10, d2=30, d3=25, d4=20 SS1=23, SS2=5, SS4=13, SS6=9 SS5 SS5 Sch Set {SS1,SS2, SS4,SS6} SS3 SS4 Tf SS3 kTf Scheduling Epoch Eligible Set {SS1, SS2, SS4, SS6} SINRi > SINRth & Backlogged O-DRR Uplink Scheduling SS1 d1=5, d2=25 SS1=46, SS2=14 Sch Set {SS1,SS2} SS4

  12. SS1 SS1 SS2 SS6 Sch Set {SS1,SS2, SS4, SS6} SS5 SS5 Sch Set {SS1,SS2} SS3 SS4 Tf SS3 kTf Scheduling Epoch Eligible Set {SS1, SS2, SS4 , SS6} SINRi > SINRth & Backlogged O-DRR Uplink Scheduling Sch Set {SS2,SS6} SS4

  13. SS1 SS1 SS2 SS6 SS5 SS5 SS3 SS4 Tf kTf Scheduling Epoch Eligible Set {SS1, SS2, SS4, SS6} SINRi > SINRth & Backlogged O-DRR Uplink Scheduling Scheduling Epoch Eligible Set {SS2, SS3, SS4, SS6}

  14. Simulation Setup • No. of users = 100 • No. of classes = 2 • k = 75, 100 • All flows backlogged (heavy traffic assumption) • Delay requirements • Class1 = 200ms • Class2 = 500ms • Total no. of frames scheduled = 2000 • Uplink slots per frame = 100 • Drop packets only if delay is violated

  15. Fairness and Throughput • O-DRR is fair • Fair among users • Max. difference in allocated bandwidth < 10 % of average • Fair among traffic classes • Both class1 and class2 traffic get almost equal number of slots • As k increases, fairness decreases (intuitively expected)

  16. Delay Performance • Meets delay guarantees of different classes of traffic • Packets are dropped only if delay is violated • Packet drop is less than 8.5% for both classes of traffic • For larger k, the dropping percentage is higher • For worst case k=100, 91.5% of traffic meets its delay

  17. Choosing Polling Interval k • Jain’s fairness index is more than 95% • A series of k are tested for fairness • Possible to trade off fairness for delay • Appropriate k to satisfy • Fairness & bandwidth requirements

  18. Discussion • Low complexity scheduling algorithm • The scheduling is done in the MAC layer • It is a cross layer scheduling scheme involving PHY and MAC layer • Jain's fairness index remains above 90% • It is possible to tradeoff fairness for delay • O-DRR ensures delay requirements of users

  19. Future Work • Multi-rate users (SSs) based on channel condition • Adaptive to channel condition where SS can select a particular modulation scheme and data rate • Effect of location-dependent channel variations • Stability analysis of the individual queues

  20. Thank You

  21. Example of O-DRR Scheme • Assumptions • Total no of slots = 60 • Number of users = 6 • Per user (quantum) = 10 • Tf= 5, K = 3 Scheduling Epoch1, Scheduling Instant1

  22. Example of O-DRR Scheme Scheduling Epoch1, Scheduling Instant2

More Related