Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Frequency Hopping for TG4g] Date Submitted: [March 13, 2010] Source:[Kuor Hsin Chang, Bob Mason] Company: [Elster Solutions] Address: [] Voice: [] E-Mail:[kuor-hsin.chang@us.elster.com, robert.t.mason@us.elster.com] Re: [] Abstract: Initiate the discussion on frequency hopping requirements for TG4g Purpose: Presented to the 802.15.4g SUN Task Group for discussion and consideration 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.

2. Outline • Abstract of the TSCH Proposal in 4e that is related to frequency hopping • Hooks in 802.11 that supports frequency hopping • Discussion

3. Network Setup (how an end device joins the network) for TSCH (time synchronization channel hopping) • Initial Communication: • Joining Device issues MLME_LISTEN.request to activate the radio to receive the Advertisement command • Listen starts on Channel[0], then Channel[1], until last channel then goes back to Channel[0] if no Advertisement is received • The Advertisement command tells the end device what timeslot (ASN) it is now, and in what timeslot the advertising device will be listening for joins/sending replies in the future

4. Network Setup for TSCH (cont’d.) • Establish Communication: • After receiving an Advertisment command, an end device may issue MLME_JOIN.request to join the network through the advertiser • The Activate command allows the advertiser to respond a join attempt back to the joining device • The Activate command can include the description of slotframe and links for the joining device to communicate with the TSCH network Slide 4

5. TSCH Time Synchronization • Node to node time synchronization can be achieved through the exchange of data and acknowledgement frames • Acknowledgement based synchronization • Transmitter node sends a frame, timing the start symbol to be sent at TsTxOffset. • Receiver records the timestamp TsRxActual of receiving the start symbol of the packet. • Receiver calculates TimeAdj = TsTxOffset – TsRxActual. • Receiver send back TimeAdj as part of acknowledgement packet. • Transmitter receives the acknowledgement. If the receiver node is a clock source node, the transmitter adjusts its network clock by TimeAdj. Slide 5

6. TSCH Time Synchronization (cont’d.) • Data frame based synchronization • A node synchronizes its own clock when receives a frame from a clock source neighbor • Synchronization algorithm • Receiver records the timestamp TsRxActual of receiving the start symbol of the packet. • Receiver calculates TimeAdj = TsTxOffset – TsRxActual. • Receiver adjusts its own network time by –TimeAdj. Slide 6

7. TSCH (cont’d.) • Timeslot Template Example Slide 7

8. TSCH Time Synchronization (cont’d.) • The TSCH MAC commands (Advertisement, Join and Activate) may not be sufficient for SUN (frequency hopping networks) • Options – • Define a new mechanism • Define the MAC PIB attributes that can be used for frequency hopping (joining would then have to be defined by a upper layer protocol) Slide 8

9. Parameters Defined in 802.11 to Facilitate Frequency Hopping • Hopping Sequence Related Parameters • Hop Set • Hop Pattern • Hop Index • HopTime • The time allocated for the PHY to change to a new frequency • MaxDwellTime • The maximum time to dwell on a channel

10. Attributes Desired to Support 802.15.4g Frequency Hopping Modes • Hopping Sequence • Define the absolute time of the frequency hopping sequence (start time and dwell time on each channel) • Dwell time (time of occupancy) • Need a parameter to define the start time for the channel sequence. Must either be absolute time or relative to a time point known by communicating devices

11. Recommended Additions to TG4e to Support Frequency Hopping • Add MAC PIB attribute macHopSequence: • An array of 512 elements to support up to 512 hopping channels • Each element is a channel number with 2 bytes length so that it can support a channel number ranging from 0 – 511. • Can be jointly defined with 4e • macHopSequence in TSCH • DCHDescriptor in DSME

12. Recommend Addition to TG4e to Support Frequency Hopping (cont’d.) • Add MAC PIB attributes to facilitate time synchronization: • macFreqHoppingStartTime: • Specify the start time of the hopping sequence • The time from midnight with resolution of 1 ms • 4 bytes in length • macFreqHoppingDwellTime: • Specify the dwell time on each channel • With unit of a symbol time of a 50 kbps system (20 μs) • 2 bytes in length (range = 0 – 1.31 seconds)

13. Questions & Discussion!