March 2004 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Synchronized Beacon Propagation for Spanning Tree Networks] Date Submitted: [18 March 2004] Source: [Phil Beecher] Company [CompXs Ltd] Address [] Voice:[], FAX: [], E-Mail:[pbeecher@compxs.com] Re: [] Abstract: [The current 802.15.4 specification does not provide support for synchronizing beacons in beacon-enabled spanning tree networks. This document points out the limitations and suggests possible solutions.] Purpose: [This document is submitted for consideration for revisions to the 802.15.4 specification.] Notice: This document has been prepared to assist the IEEE P802.15. 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 P802.15. Phil Beecher, CompXs Ltd

Synchronized Beacon Propagation in 802.15.4 March 2004 Synchronized Beacon Propagation in 802.15.4 Phil Beecher, CompXs Ltd Phil Beecher, CompXs Ltd

March 2004 Problem: Superframes are not synchronized in a beacon-enabled spanning tree PAN The network layer of a secondary coordinator has no way to control the timing of its beacons relative to the PAN coordinator. This may cause the following effects: Clock drift will lead to collision between beacons. Possible violation of CFP of the PAN coordinator Phil Beecher, CompXs Ltd

March 2004 Solutions Explicitly prohibit Spanning tree networks in beacon-enabled PANs Provide method to allow synchronization. Phil Beecher, CompXs Ltd

March 2004 Proposal 1 Add a new parameter, BeaconTxTime, to MLME-START.request primitive BeaconTxTime parameter will be defined as the time, in symbols, to delay from receipt of its parent beacon until the beacon transmission occurs. Parameter will be ignored if PANCoordinator parameter is TRUE. Reference point will be the same as macBeaconTxTime. Phil Beecher, CompXs Ltd

Is this a complete solution? March 2004 Is this a complete solution? In a word, no! It provides the means for the network layer to synchronize beacon distribution and hence avoid beacon collision. It does not solves the problem of CSMA-CA messages trampling beacons of other coordinators Phil Beecher, CompXs Ltd