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: [Enhancement to IEEE 802.15.4-2006for Industrial Markets] Date Submitted: [11 January, 2008] Source: [K. Pister and C. Kang] Company [Dust Networks] Address [30695 Huntwood Avenue, Hayward, CA 94544, USA] Voice:[+1 510 400 2900], FAX: [+1 510 489 3799], E-Mail:[kpister@dustnetworks.com and ckang@dustnetworks.com] Re: [n/a] Abstract: [This document proposes an enhancement to IEEE 802.15.4-2006 MAC Layer for Industrial Markets] Purpose: [This document is a response to Item a) better support the industrial markets in IEEE P802.15.SG4e Call for Application on 14 November, 2007] 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. K. Pister and C. Kang, Dust Networks

2. Time Synchronized Channel Hopping K. Pister C. Kang Dust Networks 11 January, 2008 K. Pister and C. Kang, Dust Networks

3. GOALS • Increase reliability and robustness required for Industrial Markets • Multi-channel hopping • Provide efficient multi-channel hopping and enable longer operational life for battery powered devices • Time Synchronized Time Division Multiplexing • Simple to co-exist with current 802.15.4 MAC devices • Simultaneous operation in 802.15.4-2006 and Time Synchronized Channel Hopping modes. • Flexible and scale-able K. Pister and C. Kang, Dust Networks

4. Slot length When SO = 0  60 symbols  0.96ms Active superframe duration 16 slots  15.36ms when SO=0 Superframe duration 15.36ms * 2BO ; BO = 0..14 Up to 4 minutes (> 250,000 msec) Semi-active Channel-hopping 802.15.4 Slot and Superframe timing K. Pister and C. Kang, Dust Networks

5. Superframe Unallocated Slot Allocated Slot Timeslots and Superframes • Each mote-to-mote communication happens within a scheduled timeslot • All timeslots are contained within a superframe • Superframes repeat in time • Multiple superframes can operate simultaneously within a network K. Pister and C. Kang, Dust Networks

6. CCA: RX startup, listen, RX->TX Time Synchronization Timing – perfect synchronization A Transmit Packet: Preamble, SS, Headers, Payload, CRC RX startup or TX->RX RX ACK B RX startup RX packet Verify CRC Calculate ACK CRC Transmit ACK RX/TX turnaround K. Pister and C. Kang, Dust Networks

7. Transmit Packet: Preamble, SS, Headers, Payload, CRC Transmit Packet: Preamble, SS, Headers, Payload, CRC Transmit Packet: Preamble, SS, Headers, Payload, CRC Transmit Packet: Preamble, SS, Headers, Payload, CRC Transmit Packet: Preamble, SS, Headers, Payload, CRC Transmit Packet: Preamble, SS, Headers, Payload, CRC Tcrc Tcrc Tcrc Tcrc Tcrc Tcrc TACK TACK TACK TACK TACK TACK TCCA TCCA TCCA TCCA TCCA TCCA Time Synchronization (Cont’d) Tg Tg Tg Tg Early Perfect Late Tcomm = Tpacket+Tcrc+TACK Tslot = 2Tg+Tcomm+TCCA Tcrc includes TgACK and all CRC and radio turnaround times. It’s the time from the last bit of the packet to the first bit of the preamble of the ACK. K. Pister and C. Kang, Dust Networks

8. Time Synchronization • Acknowledgement-based Synchronization • Transmitter node sends a packet, timing at the start symbol. • Receiver timestamps the actual timing of the reception of start symbol • Receiver calculates TimeAdj = Expected Timing – Actual measured Timing • Receiver informs the sender TimeAdj • Transmitter adjusts its clock by TimeAdj K. Pister and C. Kang, Dust Networks

9. Time Synchronization (Cont’d) • Received Packet-based Synchronization • Receiver timestamps the actual timing of the reception of start symbol • Receiver calculates TimeAdj = TimeExpected (expected arrival time) – Actual timing • Receiver adjusts its own clock by TimeAdj K. Pister and C. Kang, Dust Networks

10. D B Link = (Time Slot , Channel Offset) One Slot Time Chan. offset A • The two links from B to A are dedicated • D and C share a link for transmitting to A • The shared link does not collide with the dedicated links BA CA DA C BA BC E F BE BF K. Pister and C. Kang, Dust Networks

11. D B Timeslot and Channel Mapping One Slot Time Chan. 2.405 GHz A • The two links from B to A are dedicated • D and C share a link for transmitting to A • The shared link does not collide with the dedicated links BA 2.470 GHz CA DA C 2.445 GHz BA 2.425 GHz Slot links for devices 2.475 GHz 2.440 GHz … 2.480 GHz K. Pister and C. Kang, Dust Networks

12. Frequency Hopping Time BA • Each link rotates through k available channels over k cycles. • Blacklisting can be defined globally and locally. BA CA DA BA Channel BA BA CA DA CA DA BA Cycle N+1 Cycle N CycleN+2 K. Pister and C. Kang, Dust Networks

13. Channel Hopping • Need to map (slot, offset) into an 802.15.4 channel • For blacklisting, assume • Num_channels • LookUp() defines pseudo-random hop sequence over num_channels • ASN = absolute slot number • Chan = (ASN + offset) % num_channels • 15.4Channel = LookUp(Chan) K. Pister and C. Kang, Dust Networks

14. Non-conflicting Timeslot assignment • Devices can be given one or more offsets. OR • Devices can be given one or more slots in a particular superframe. OR • Devices can be given a block of (slot,offset)s slot Chan. offset K. Pister and C. Kang, Dust Networks

15. Non-conflicting timeslot assignment • Devices can be given one or more offsets. OR • Devices can be given one or more slots in a particular superframe. OR • Devices can be given a block of (slot,offset)s SD=aBaseSuperframeDuration*2SOsymbols BI=aBaseSuperframeDuration*2BOsymbols K. Pister and C. Kang, Dust Networks

16. Non-conflicting timeslot assignment • Multiple superframes with different lengths can operate without conflict as well. • 4 cycles of the 250ms superframe are shown, along with a 1s superframe • There are never collisions if the 1 second frame uses only the empty slots 250ms 1,000ms K. Pister and C. Kang, Dust Networks

17. Example of HART Capability • Data collection • 100 pkt/s per access point channel • 16*100 pkt/s with no spatial reuse of frequency • 105 MPDU bytes per packet assuming 22 bytes of MAC header, MIC, CRC • Throughput • 84kbps MPDU bits per second per access point • 15 * 84k = 1.26Mbps combined payload throughput w/ no spatial reuse of frequency • Latency • 10ms / PDR (Packet Delivery Rate) per hop • Statistical, but well modeled K. Pister and C. Kang, Dust Networks

18. Built-In Flexibility • Trade performance and power • Sample & reporting rate • Latency • High bandwidth connections • Tradeoffs can vary with • Time • Location • Events • Use power intelligently if you’ve got it • Highest performance with powered infrastructure K. Pister and C. Kang, Dust Networks

19. Added MAC PAN Service Primitives K. Pister and C. Kang, Dust Networks

20. Added MAC MIB K. Pister and C. Kang, Dust Networks

21. Added SMIB (Structured MIB) • Link Table: contains all links configured on the device. • Superframe Table: contains all superframes configured on the device. K. Pister and C. Kang, Dust Networks