Energy-Saving Scheduling in IEEE e Networks Chia-Yen Lin, and Hsi-Lu Chao Department of Computer Science National Chiao Tung University

Outline Introduction Related work –AS and Period algorithms Least-Awake-Frames Scheduling (LAFS) –System model –Phase 1 for UGS connections –Phase 2 for rtPS and nrtPS connections –Phase 3 for MSS to determine sleep and awake frames Performance Evaluation Conclusion

Introduction The IEEE e standard defines three types of power saving classes. Sleep Mode Type 1 … Type 2 … Type 3 … Normal OperationSleep periodListen period

Introduction It is not efficient that MSS can only enters sleep mode when all connections have common sleep period. Connection 1 Connection 2 Connection 3 MSS Sleep period Listen period

Related work Some papers were proposed to enhance the power saving mechanism in IEEE e standard. –Energy-Efficient Sleep-Mode Operation for Broadband Wireless Access Systems. 【 AS 】 IEEE VTC 2006 You-Lin Chen, and Shiao-Li Tsao –A Maximal Power-Conserving Scheduling Algorithm for IEEE e Broadband Wireless Networks. 【 Period 】 IEEE WCNC 2008 Hsin-Lung Tseng, Yu-Pin Hsu, Chung-Hsien Hsu, Po-Hsuan Tseng, and Kai-Ten Feng

Related work - AS The main concept is that choosing the connection with the minimum delay requirement to be the base, and adjusting other connections’ transmissions to reduce total power consumption, but still satisfy connections’ QoS demands. Listen periodSleep periodListen periodSleep period Packet Arrivals Packets Scheduling maximum delay : 3 frames

Related work - Period This algorithm maximizes the duration of the sleep interval based on the pre-defined QoS requirements by discovering a periodic pattern of sleep and awake intervals. TSTS TLTL Frame Duration Bandwidth constraint Delay constraint

Related work The major drawback of AS and Period –they do not consider non-real time connections. Motivation and objectives –Design a power saving protocol which is suitable for UGS, rtPS, nrtPS and BE service classes, guaranteeing QoS demands, and lengthening sleep interval.

Least-Awake-Frames Scheduling (LAFS) Phase 1 –determining awake-frame candidate sets for UGS connections Phase 2 –determining sleep/awake intervals for connections of the remaining service classes, such as rtPS, nrtPS, and BE connections Phase 3 –determining sleep and awake frames of an MSS

System model in LAFS QoS parameters : –p : grant period (frame) –d : maximum grant delay (frame) –r : allocated bandwidth per frame (bits/frame) –μ min : minimum service rate per frame –μ max : maximum service rate per frame –d’ : maximum delay UGS : ( p, d, r ) rtPS : (μ min, μ max, d’ ) nrtPS : (μ min, μ max ) BE : (μ max )

System model in LAFS LAFS operates in TDD mode. A connection admission control (CAC) mechanism is implemented in WiMAX system. –whether QoS requirement can be satisfied or not –whether the rescheduled per-frame bandwidth allocation does not exceed the frame capacity or not MSS ID connection ID Link capacity frame duration a constant within (0,1]

Phase 1 in LAFS Determination of awake-frame candidate set for UGS –those frames the MSS can delay its transmissions to. r 1 = 7 M / frame, r 2 = 6 M / frame, r 3 = 4 M / frame, C = 10 Mbps,  t = 1 sec [3,4] or [4,5]

Phase 2 in LAFS Calculation of sleep/awake interval for other service types. –This paper assumes that an MSS will report the queue sizes of rtPS, nrtPS, and BE connections to its BS at the end of an awake-interval through polling and piggyback. packets arrived in current sleep and awake intervals (e.g., S i and W i ) will be transmitted in the following awake interval (W i+1 )

Phase 2 in LAFS L i : the cumulated queue size of an MSS within S i and W i. the maximum required number of frames for the (i+1) th awake interval W i+1 is

Phase 2 in LAFS An MSS has six connections (data rate, maximum delay) –(256 Kbps, 4 frames) –(512 Kbps, 5 frames) –( 2 Mbps, 6 frames) –S 1 = W 1 = 1 frame –1 frame = 1 sec –C = 20 Mbps ( 256K * K * 2 + 2M * 2 ) * 2 = Mbits S 2 ≤ 4 – 1 – 1 – = 1S 2 ≤ 4 – 1 – = 2

Phase 3 in LAFS Only UGS connections –BS informs the MSS of its awake frames being last N UGS frames within the awake-frame candidate set. Only rtPS and nrtPS connections –The sleep and awake intervals of the MSS is obtained from phase 2.

Phase 3 in LAFS All connections –awake-frame candidate set and sleep/awake interval have overlap.

Performance Evaluation 8Mbps Bandwidth Frame duration : 5 ms Time slot : 0.1 ms DL/UL-MAP occupies 2 slots One BS-MSS, MSS with multiple connections Data rate : [ 25Kbps, 56Kbps ] Packet arrivals occur at the beginning of a frame Simulation time : 25 secs

Performance Evaluation UGS connections per-connection-basis

Performance Evaluation UGS connections

Performance Evaluation UGS connections

Performance Evaluation UGS connections

Performance Evaluation ALL connections

Performance Evaluation ALL connections

Performance Evaluation ALL connections

Conclusion The Least-Awake Frames Scheduling (LAFS) for IEEE e networks improves power saving efficiency. The major contribution of this paper is LAFS supports all service classes. The LAFS algorithm outperforms the power-saving mechanism defined in IEEE e and other existing power saving protocols.

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