1. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Modifying Superframe Intervals and Set up the Scheduling Beacons ]
Date Submitted: [24 June, 2008]
Source: [Ning Gu, Liang Zhang, Zhu Lan] Company [Vinno Technologies Inc. , CESI]
Address [Room 402 Building D, Pioneering Park, No. 2 Shangdi Xinxi Rd, Peking, China]
Voice:[ ], FAX: [ ],
Re: [IEEE e group]
Abstract: [An improved scheduling beacon structure is proposed to effectively decrease the packets collision possibility ]
Purpose: [To promote discussion in IEEE e Study Group]
Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P
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2. <11 January, 2008r>
doc.: IEEE <doc#>
Objectives
An improved scheduling beacon structure is proposed to effectively decrease the packets collision possibility.
Page 2
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3. Existing Problems
Original definition of scheduling beacons in 15.4 is not specific and adaptive.
Original SF(superframe) structure leads to low throughput because at least half of the beacon interval in one network may be used for sleep mode as BO>SO. (Beacon Order. Superframe Order)
Too many nodes working in shared time slots (SF overlap) might cause following problems:
Some nodes might overhear packets that destined to other nodes.
Heavy loaded network (too many nodes) might easily result in a “channel access failure” when performing CSMA/CA procedure.

4. The Definition of Scheduling Beacon
Scheduling beacon is a method to configure superframe features of beaconed coordinator, which include BO, SO and beacon relative time Tx, etc.
Superframe overlapping can be prevented by choosing appropriate SO and beacon start time.

5. Modification for Scheduling Beacons
Suggested modification and improvements:
15.4 regulates that “BO and SO shall be equal for all SF on a PAN”, which might be replaced with “BO shall be equal for all SF on a PAN”.
Might consider inserting scheduling beacon information in the payload of beacon frame, which includes the relative timing Tx and the network information.
Original scheduling beacon starting procedure for coordinator that is not PAN coordinator could be modified and detailed.

6. Modified Scheduling Beacon Structure
All the nodes are routers, node A is the parent of node B, node C and node D.
In upper figure, SFa = SFb = SFc as regulated in 15.4
In lower figure, SF interval of B, C and D are much shorter than the upper ones.
It’s clear that flexible SO results in more SF being inserted into the inactive period.

7. Start a Scheduling Beacon
A potential scheduling beaconed device might take the following steps to start scheduling beacons.
The device shall first perform ED and active scan to find potential parent node.
Perform association if this potential parent node being found.
Obtain the beacon information of parent’s descendant by scanning

8. Start a Scheduling Beacon (continued)
After step 3 in previous slide, the following steps might be taken by the device:
if no other beacons can be scanned, the device may transmit its own scheduling beacons during inactive period. Note: the transmitting start time, i.e., Tx, is decided by “StartTime” in start request primitive.
if other beaconed router are scanned, it shall obtain these routers’ SF information and start its own scheduling SF and inserts it by deciding an appropriate Tx time to make sure there is no SF overlapping.
if this device want to be a beaconed router and it can not find an appropriate Tx time to avoid the overlapping with other beacons from any network depth, it shall perform channel hopping and repeat the above steps.
if none of the above is available, this device shall work as an end device.
Note: PAN coordinator shall choose lower SO and higher BO to provide longer inactive period which allows more scheduling beacons being inserted into.

9. The Benefits from Improved Scheduling Beacons
Network scale is enlarged because more routers can be arranged to work in inactive period.
Network throughput is increased since inactive period is used for communication.
Network latency is reduced because less nodes are occupying the channel at the same time.
Packets confliction possibility is decreased and more power can be saved.

10. doc.: IEEE 802.15-<doc#>
<11 January, 2008r>
doc.: IEEE <doc#>
24 June, 2008
Thank you!
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