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Improving Mobile Station Energy Efficiency in IEEE 802.16e WMAN by Burst Scheduling

Improving Mobile Station Energy Efficiency in IEEE 802.16e WMAN by Burst Scheduling. Jinglin Shi, Gengfa Fang, Yi Sun, Jihua Zhou, Zhongcheng Li, and Eryk Dutkiewicz. IEEE GLOBECOM 2006. Outline. Introduction System model Longest virtual burst first scheduling Simulation Conclusion.

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Improving Mobile Station Energy Efficiency in IEEE 802.16e WMAN by Burst Scheduling

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  1. Improving Mobile Station Energy Efficiency in IEEE 802.16e WMAN by Burst Scheduling Jinglin Shi, Gengfa Fang, Yi Sun, Jihua Zhou, Zhongcheng Li, and Eryk Dutkiewicz IEEE GLOBECOM 2006

  2. Outline • Introduction • System model • Longest virtual burst first scheduling • Simulation • Conclusion

  3. Introduction • Wireless Network Interface (WNI) • MS has two states • Awake mode and sleep mode • Save power by turning off the WNI • Each sleep cycle is divided into multiple sleep intervals • Each interval is made up of a sleep window and a listening window

  4. Energy saving factors • IEEE 802.16e QoS requirements • Minimum data rate • Inter-state transition takes extra time and energy

  5. System model • TDMA is used where bandwidth is calculated in time slots • The uplink and downlink traffic is separated in the TDD mode • We only consider downlink scenario from BS to MSs • Data rate is fixed for all MSs • Minimum data rate as the only QoS requirement of each MS

  6. Notations • M: the number of MSs included in one cell system • i: index of users in the cell, (i=1,2,…,M) • n: the index of time slot, (n=1,2,…) • rni: date rate that MS i allocated by time slot n • Rmini: minimum data rate which is the QoS of user i • sni: the state of MS i in time slot n, (1: awake; 0: sleep) • Paw: average energy consumed in each time slot by each MS in awake state • Ptn: average energy consumed of state switch

  7. Formulate energy conserving scheduling problem

  8. Energy consumption analysis • When MS awake, scheduler must allocate as many time slots as possible • Scheduler must choose relatively better channel quality MS for each time slot • When MS is sleeping, it shouldn’t be awaked unless it will violate QoS requirement

  9. Longest virtual burst first scheduling (LVBF) • Virtual burst: a period of time where there are one primary MS and multiple secondary MSs sharing the time slots • Primary MS: chosen from awake MSs and occupies almost all the bandwidth during the period • Secondary MS : all the other awake state MSs except the primary MS and they have enough resource for their minimum data rate

  10. Example of virtual burst scheduling MS i starts sleep request when rni > Rmaxi

  11. Definition analysis • Choose primary MS • Idle Rateξ : rate of idle time slots to the total time slots for the primary MS (degree of primary MS occupies the bandwidth) A set of secondary MSs Total channel capacity

  12. Definition analysis (cont.) • Ending each virtual burst when: • Sleep duration ε is a System parameter, which trades off average delay and energy efficiency. The size of the sliding window

  13. Definition analysis (cont.) • Invoke the sleep-state MS i when • The scheduling result (non-empty)

  14. LVBD scheduling policy

  15. Example of LVBD scheduling - Step 1 • Start a burst and choosing the primary MS and the remaining awake-state MSs are secondary MS primary MSi = 3 secondary MSi= {1,2} min

  16. Example of LVBD scheduling - Step 2 • Scheduling for the current time slot among the primary and secondary MSs (non-empty) (i* : Primary MS) Swk = { i: 1 and 5 < 2 2 and 7 < 4 } empty Secondary MS 1 SecondaryMS 2 Primary MS 3

  17. Example of LVBD scheduling - Step 3 • Update MSs’ perceived data rate base on the scheduling result in Step 2 (non-empty) (i* : Primary MS) Swk = { i: 1 and 1 < 2 2 and 3 < 4 } non-empty Secondary MS 1 SecondaryMS 2 min Primary MS 3

  18. Example of LVBD scheduling - Step 4 • If current primary MS goes into sleep state, start a new virtual burst and go to Step 1, otherwise go to Step 5 rni > Rmaxi starts sleep request 15 > 14 Calculate the sleep duration If Lsw = 3 (1- (dni* / 3) 15 = 2 dni* = 3 (1- 2/15) = 2.6 go to Step 1 and MS 3 sleeps for 2.6 time slot

  19. Example of LVBD scheduling - Step 5 • If the event (ξ > ε) happens, start a new virtual burst and go to Step 1, otherwise, go to Step 2 for the next scheduling cycle Calculate the idle rate If C = 30, ε=0.5 ξ=(2+4)/30=0.2 ξ = 0.2 < 0.5 = ε go to Step 2

  20. Example of LVBD scheduling (cont.) ξ > ε Secondary MS 1 Primary MS 1 SecondaryMS 2 Primary MS 2 SecondaryMS 3 Primary MS 3 Sleep MS 3 rni > Rmaxi

  21. Simulation • Compare to Round Robin algorithm • Fading channel is represented by nine-state Markov chain • Generated traffic in BS as a Poisson process • Each packet is fixed size • Average energy efficiency as • Each state transition cost 100 time slots unit of energy

  22. Average energy efficiency vs system payload

  23. Minimum data rates guarantee for users

  24. Conclusion • Proposed a Longest Virtual Burst First scheduling algorithm • LVBF prolongs MSs’ lifetime by reducing the average time when MSs stay in awake state and state transition times

  25. Thank you

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