July 2008 doc IEEE 802 15 08 409

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Project: IEEE P 802. 15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Time Slotted, Channel Hopping MAC] Date Submitted: [6 July, 2008] Source: [Chol Su Kang, Kuor Hsin Chang, Rick Enns] Company [Dust Networks, Freescale] Address [30695 Huntwood Avenue, Hayward, CA 94544; 890 N. Mc. Carthy Blvd, Suite 120, Milpitas, CA 95035] Voice: [+1 510 400 2900, +1 408 904 2705, +1 650 327 9708] E-Mail: [ckang@dustnetworks. com, Kuor-Hsin. Chang@freescale. com, enns@stanfordalumni. org Re: [n/a] Abstract: [This document proposes extensions for IEEE 802. 15. 4 MAC] Purpose: [This document is a response to the Call For Proposal, IEEE P 802. 15 -08 -373 -01 -0043] Notice: This document has been prepared to assist the IEEE P 802. 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 P 802. 15. Time Slotted, Channel Hopping MAC Proposal Slide 1 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Time Slotted, Channel Hopping MAC (TSCH) Chol Su Kang - Dust Networks Kuor Hsin Chang - Freescale Rick Enns - Consultant July, 2008 Time Slotted, Channel Hopping MAC Proposal Slide 2 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Target Applications Includes: • Equipment and process monitoring • Non-critical control • Diagnostics/predictive maintenance • Asset management Time Slotted, Channel Hopping MAC Proposal Slide 3 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Requirements • Reliability and robustness • Long operational life for battery powered devices (> 5 years) • Co-existence • Flexible and scale-able • Coverage • Easy wireless network deployment and maintenance Time Slotted, Channel Hopping MAC Proposal Slide 4 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Time Slot Access Slot Frame Cycle Unallocated Slot Tx CCA: RX startup, listen, RX->TX Rx RX startup Allocated Slot Transmit Packet: Preamble, SFD, Headers, Payload, CRC RX packet RX startup or TX->RX Verify CRC Calculate ACK CRC RX ACK Transmit ACK RX/TX turnaround timeslot • • Each device-to-device communication happens within a scheduled timeslot All timeslots are contained within a slot frame cycle Cycle of timeslots repeats in time CCA before transmit in timeslots Time Slotted, Channel Hopping MAC Proposal Slide 5 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Time Slot Media Access Basics • Schedule link activity • Time synchronization required for devices in the network: – Specification on time difference tolerances – Time synchronization mechanisms • Transmission starts at a specified time after the beginning of a slot: – Allow the source and destination to set their frequency channel – Allow the receiver to begin listening Time Slotted, Channel Hopping MAC Proposal Slide 6 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Channel Hopping 802. 15. 4 Channels Slot n-2 Slot n-1 Slot n+1 Slot n+2 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 • Combined with timeslot access to enhance reliability Time Slotted, Channel Hopping MAC Proposal Slide 7 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Channel Hopping • Frequency Diversity – Reduce the effect of Interference and Multipath Fading • Network Capacity – One timeslot can be used by multiple links at the same time • Within a network, each device has identical channel lists Time Slotted, Channel Hopping MAC Proposal Slide 8 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Link = (Timeslot , Channel Offset) D One Slot Time Chan. offset A B A C D A B B A B C E F B E B F • 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 Time Slotted, Channel Hopping MAC Proposal Slide 9 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Channel Hopping Channel Offset Time B A (ch 15) C A D A B A (ch 25 ) C A D A B A N*4+2 N*4+3 B C B E B F (N+1)*4 Cycle N • B A B C B E B F N*4+1 C A D A B C ASN= N*4 B A (ch 18 ) Cycle N+1 B E B F Cycle N+2 Each link rotates through k available channels over k cycles. – Ch # = Chan Hopping Seq. Table ( ( ASN + Channel Offset) % Number_of_Channels ) • Blacklisting can be defined globally and locally. Time Slotted, Channel Hopping MAC Proposal Slide 10 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Timeslot Timing Offsets T 1 Transmitter T 2 T 4 T 3 CCA TX Packet Ts. Rx. Ack. Delay Ts. CCAOffset RX ACK prepare to receive AWT Ts. Tx. Offset Receiver prepare to receive RX Packet Ts. Rx. Offset PWT R 1 Start of timeslot process packet, prepare to ack TX ACK Ts. Tx. Ack. Delay R 2 = transmitting packet = receiver on = receiving packet R 3 End of timeslot Timeslot with Acknowledged Transmission PWT = Ts. Packet. Wait. Time AWT = Ts. Ack. Wait. Time Slotted, Channel Hopping MAC Proposal Slide 11 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Timeslot Timing Offsets (Cont’d) T 1 Transmitter T 2 T 4 T 3 CCA TX Packet prepare to receive Idle receive Ts. Rx. Ack. Delay Ts. CCAOffset AWT Ts. Tx. Offset Receiver prepare to receive RX Packet Ts. Rx. Offset PWT R 1 Start of timeslot process packet, decide not to ack R 2 = transmitting packet = receiver on = receiving packet End of timeslot Timeslot with Unacknowledged Transmission PWT = Ts. Packet. Wait. Time AWT = Ts. Ack. Wait. Time Slotted, Channel Hopping MAC Proposal Slide 12 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Timeslot Timing Offsets (Cont’d) T 1 Transmitter T 2 CCA TX Packet no ack expected Ts. CCAOffset Ts. Tx. Offset Receiver prepare to receive RX Packet Ts. Rx. Offset PWT R 1 Start of timeslot process packet, decide not to ack R 2 = transmitting packet = receiver on = receiving packet End of timeslot Timeslot with Unacknowledged Broadcast PWT = Ts. Packet. Wait. Time AWT = Ts. Ack. Wait. Time Slotted, Channel Hopping MAC Proposal Slide 13 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Timeslot Timing Offsets (Cont’d) Transmitter Receiver idle prepare to receive idle Idle rx Ts. Rx. Offset PWT R 1 R 2 End of timeslot Start of timeslot Timeslot with Idle Receive = receiver on PWT = Ts. Packet. Wait. Time Slotted, Channel Hopping MAC Proposal Slide 14 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Time Synchronization Tg Early TC CA Perfect Late Tg Tg Transmit Packet: Preamble, SFD, Headers, Payload, FCS TC CA TProcessing Transmit Packet: Preamble, SFD, Headers, Payload, FCS TC CA TACK TProcessing TACK TC CA Transmit Packet: Preamble, SFD, Headers, Payload, FCS Tg TProcessing Transmit Packet: Preamble, SFD, Headers, Payload, FCS TACK Tcomm = TTXPacket+TProcessing+TACK Timeslot Period TProcessing includes the processing of FCS and MIC validation as well as FCS and MIC generation for ACK. It’s the time from the last bit of the packet to the first bit of the preamble of the ACK. Time Slotted, Channel Hopping MAC Proposal Slide 15 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Time Synchronization (Cont’d) Time Slotted, Channel Hopping MAC Proposal Slide 16 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Time Synchronization • Acknowledgement-based Synchronization 1. Transmitter node sends a packet, timing at the start symbol. 2. Receiver timestamps the actual timing of the reception of start symbol 3. Receiver calculates Time. Adj = Expected Timing – Actual measured Timing 4. Receiver informs the sender Time. Adj 5. Transmitter adjusts its clock by Time. Adj Time Slotted, Channel Hopping MAC Proposal Slide 17 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Time Synchronization (Cont’d) • Received Packet-based Synchronization 1. Receiver timestamps the actual timing of the reception of start symbol 2. Receiver calculates Time. Adj = Time. Expected (expected arrival time) – Actual timing 3. Receiver adjusts its own clock by Time. Adj • A node can be synchronized to more than one parent (i. e. timing reference nodes) Time Slotted, Channel Hopping MAC Proposal Slide 18 Chol Su Kang et al.

July, 2008 A Network Build Up Sequence Example ASN Advertise C In this example, A is PAN Coordinator. B and D are FFD. C is RFD. A Initializes Search for Network B This example uses six Channels 8 slots in slot-frame. D Advertise Join Req C Slot Frame Channel Offset 1 D B Initializes slot-frame as configured in DB 0 doc. : IEEE 802. 15 -08 -409 -00 -004 e A ALL ASN=0 Time Slotted, Channel Hopping MAC Proposal Slide 19 A RX 1 2 3 4 5 6 Chol Su Kang et al. 7

July, 2008 Network Build Up Seq. Example Cont’d Initializes slot-frames as configured in DB ASN 0 1 8 16 24 D B Advertise C A Initializes Search for Network B Advertise Join Req Join Rsp Set-Link(ts=4, ch. O=2, B A) Set-Link(ts=2, ch. O=0, Adv; Rx=3, 1) Click to Continue Time Slotted, Channel Hopping MAC Proposal D C Slot Frame Channel Offset A doc. : IEEE 802. 15 -08 -409 -00 -004 e A ALL B ALL A RX B A ASN=8 9 ASN=16 17 ASN=24 25 Slide 20 B RX 11 12 13 18 19 20 21 22 23 26 27 28 29 30 31 10 14 Chol Su Kang et al. 15

July, 2008 Network Build Up Seq. Example Cont’d Initializes slot-frames as configured in DB ASN 0 1 8 16 24 32 33 40 48 56 D B C Initializes Search for Network Advertise A B Advertise Join Req Join Rsp Set-Link(ts=4, ch. O=2, B A) Set-Link(ts=2, ch. O=0, Adv; Rx=3, 1) Advertise Search for Network Slot Frame Advertise Join Req Join Rsp Set-Link(ts=1, ch. O=1, D A) Set-Link(ts=6, ch. O=2, Adv; Rx=7, 1) Click to Continue A ALL ASN=32 ASN=40 ASN=48 ASN=56 Time Slotted, Channel Hopping MAC Proposal D C Initializes Channel Offset A doc. : IEEE 802. 15 -08 -409 -00 -004 e Slide 21 D ALL B ALL D A B RX A RX D RX B A 33 41 49 57 34 42 50 58 35 43 51 59 36 44 52 60 37 45 53 61 38 46 54 62 Chol Su Kang et al. 39 47 55 63

July, 2008 Network Build Up Seq. Example Cont’d Initializes slot-frames as configured in DB ASN 0 1 8 16 24 32 33 40 48 56 66 67 68 72 74 80 82 D B C Initializes Search for Network Advertise A B Advertise Join Req Join Rsp Set-Link(ts=4, ch. O=2, B A) Set-Link(ts=2, ch. O=0, Adv; Rx=3, 1) Advertise Initializes Search for Network Slot Frame Advertise Join Req Join Rsp Set-Link(ts=5, ch. O=1, D A) Set-Link(ts=6, ch. O=2, Adv; Rx=7, 1) Advertise Join Req Join Rsp Set-Link(ts=5, ch. O=3, C B) Set-Link(ts=5, ch. O=2, C B) Click to Continue Time Slotted, Channel Hopping MAC Proposal D C Channel Offset A doc. : IEEE 802. 15 -08 -409 -00 -004 e B C B ALL A RX D ALL D RX D A B RX B A C B ASN=64 65 66 67 68 69 70 71 ASN=72 ASN=80 73 81 74 82 75 83 76 84 77 85 78 86 79 87 Slide 22 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Network Build Up Seq. Example Cont’d A ASN 8 16 24 32 66 67 68 72 74 80 82 86 87 93 96 102 104 110 Initializes Search for Network Advertise B Advertise Join Req Join Rsp Set-Link(ts=4, ch. O=2, B A) Set-Link(ts=2, ch. O=0, Adv; Rx=3, 1) Advertise Search for Network C Advertise Slot Frame Set-Link(ts=5, ch. O=1, D A) Set-Link(ts=6, ch. O=2, Adv; Rx=7, 1) Advertise Join Req Join Rsp Set-Link(ts=5, ch. O=3, C B) Set-Link(ts=5, ch. O=2, C B) Advertise D Initializes Join Req Join Rsp 33 40 48 56 Initializes Advertise Join Req Join Rsp Set-Link(ts=4, ch. O=0, C D) Advertise Join Req Channel Offset 1 C A Initializes slot-frames as configured in DB 0 D B B C B ALL ASN=104 A RX 105 C D 107 D RX D A B RX 106 D ALL B A C B 108 109 110 Join Rsp Set-Link(ts=4, ch. O=0, C D) Click Hopping to Continue Time Slotted, Channel MAC Proposal Slide 23 Chol Su Kang et al. 111

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Network Build Up Seq. Example Cont’d A B . . . ASN Advertise 66 67 68 72 74 80 82 86 87 93 96 102 104 110 114 115 116 120 122 130 132 A Advertise B D Join Req Join Rsp 33 40 48 56 C Set-Link(ts=5, ch. O=1, D A) Set-Link(ts=6, ch. O=2, Adv; Rx=7, 1) Advertise Join Req Join Rsp Set-Link(ts=5, ch. O=3, C B) Set-Link(ts=5, ch. O=2, C B) Advertise Join Req Join Rsp Set-Link(ts=4, ch. O=0, C D) Advertise C Slot Frame Time Slot Channel Offset 32 . . . D B C B ALL A RX C D D ALL D RX D A B RX B A C B 132 133 D B Advertise Join Req Join Rsp Set-Link(ts=1, ch. O=3, D B) Time Slotted, Channel Hopping MAC Proposal ASN=128 Slide 24 129 130 131 134 Chol Su Kang et al. 135

July, 2008 • • • doc. : IEEE 802. 15 -08 -409 -00 -004 e Non-conflicting Timeslot assignment Devices with multiple radios can be given one or more offsets. Devices can be given one or more slots in a particular slot-frame. Devices with multiple radios can be given a block of (slot, offset)s Chan. offset slot Time Slotted, Channel Hopping MAC Proposal Slide 25 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Non-conflicting timeslot assignment • Multiple slot-frames with different lengths can operate at the same time. • 4 cycles of the 250 ms slot-frame are shown, along with a 1000 ms slot frame • There are never collisions if the 1000 ms slot frame uses only the empty slots of the 250 ms slot frame 250 ms 1, 000 ms Time Slotted, Channel Hopping MAC Proposal Slide 26 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Example of TSCH Capability • Data collection – 100 pkt/s per access point channel using 10 ms slots – 1600 pkt/s (16*100) network capacity with no spatial reuse of frequency – 105 MPDU bytes per packet assuming 22 bytes of MAC header, MIC-32, FCS (worst case header size) • Throughput – 84 kbps MPDU per access point – 16 * 84 k = 1. 344 Mbps combined payload throughput w/ no spatial reuse of frequency • Latency – 10 ms / PDR (Packet Delivery Rate) per hop: best case – Statistical, but well modeled Time Slotted, Channel Hopping MAC Proposal Slide 27 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Built-In Flexibility • Trade performance and power – – – Sample & reporting rate Latency Reliability Throughput High bandwidth connections • Tradeoffs can vary with – Time – Location – Events • Use power intelligently if you’ve got it – Highest performance with powered infrastructure Time Slotted, Channel Hopping MAC Proposal Slide 28 Chol Su Kang et al.

July, 2008 doc. : IEEE 802. 15 -08 -409 -00 -004 e Added MAC PAN Service Primitives Primitive Description SET-SUPERFRAME Add, delete, or modify a superframe X X SET-LINK Add, delete, or modify a link X X TSCH-MODE Operate in Time Slot Channel Hopping mode X X ADVERTISEMENT Start the advertisement X X Time Slotted, Channel Hopping MAC Proposal Request Slide 29 Confirm Response Indication Chol Su Kang et al.