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May 2013. Page Scheduling. Authors:. Date: 2013-05-10. Introduction. We propose to add ‘ Page Period ’ indication in Segment Count IE to support more flexible page scheduling. Background: TIM Segmentation.
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May 2013 Page Scheduling Authors: Date: 2013-05-10 Y. Zhou, I2R
Introduction We propose to add ‘Page Period’ indication in Segment Count IE to support more flexible page scheduling. Y. Zhou, I2R
Background: TIM Segmentation Y. Zhou, I2R • TIM and page segmentation has been accepted in 802.11ah SFD [1] for STAs supporting TIM segmentation • Fragment the TIM element into equal sized TIM segments. • Multiple such TIM segments may be assigned within a DTIM beacon interval. • Each TIM segment shall use a fixed length Page segment within one DTIM beacon interval. • Each ordered page segment is assigned sequentially to TIM segments, where the first Page segment may be assigned to the DTIM segment. • For a STA not supporting TIM segmentation, its corresponding bit in the TIM shall be included in all the Beacons irrespective of segmentation
Background: Segment Count IE (SC-IE) • The Segment Count element indicates the sequence of Page segments. • Page Index: the Page whose segments are served during TIM intervals within a DTIM interval. • Page Segment Count: number of TIM segments scheduled in one DTIM interval • Maximum of 32 TIM segments in a DTIM interval • Page Offset field: offset of the block in the first Page segment from the first block in the Page assigned within the DTIM interval. • Page Bitmap field: indication of presence of buffered data for each of the one or more blocks in all the assigned page segments within a DTIM interval. Y. Zhou, I2R
Problem (1) • DTIM period is usually determined based on application’s latency requirement for broadcast / multicast data. • With current TIM segmentation, DTIM period also has to cater for TIM segments. • TIM segments of a page are transmitted within one DTIM period. • DTIM period may not match TIM segmentation. • E.g. DTIM period = 4 BI, but TIM segmentation requires 16 segments. Y. Zhou, I2R
Problem (2) Page 1Segment Count = 32 P1 S2 P1 S1 P1 S2 P1 S1 P2 S2 P2 S3 P2 S4 P2 S32 P2 S1 P2 S2 P2 S1 … DTIM DTIM Page 2 Segment Count = 32 • Hierarchical TIM structure defines multiple pages. Each page may have different traffic features and require different TIM segmentation. • Current TIM segmentation scheme cannot efficiently support different pages with different number of TIM segments. E.g.: • Page 1: 64 STAs with 2 segments • Page 2: 2000 STAs with 32 segments Y. Zhou, I2R
Proposal • Add ‘Page Period’indication in Segment Count IE. • Page Period indicates the number of beacon intervals between successive beacons that carry the Segment Count IE for the associated page. Element ID Length Page Index Page Period (1 byte) Page Segment Count Page Offset Reserved Page Bitmap • Segment Count IE for each page may not be transmitted on every DTIM. • Transmission of TIM segments of a page may span over multiple DTIM periods. • Same as current TIM segmentation when Page Period = DTIM Period. Y. Zhou, I2R
Examples of Page Period • The definition of Page Period decouples TIM segmentation from DTIM period and supports more flexible page scheduling. Page 1 period = 4 BI DTIM Page 1 SC-IE Page 2 SC-IE DTIM Page 1 SC-IE DTIM Page 1 SC-IE Page 2 SC-IE DTIM Page 1SC-IE Page 2 period = 8 BI Page 1 TIM segments, scheduled every DTIM Page 2 TIM segments, scheduled every 2 DTIMs Y. Zhou, I2R
Straw Poll • Do you support to include SFD a ‘Page Period’ indication in Segment Count IE to indicate the number of beacon intervals between successive beacons that carry the Segment Count IE for the associated page? • Y • N • A Y. Zhou, I2R
Reference [1] 11-12-1084-04-00ah-tim-and-page-segmentation. Y. Zhou, I2R