doc.: IEEE <doc#>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Time Slotted, Channel Hopping MAC] Date Submitted: [1 Sep, 2008] Source: [Kris Pister, Chol Su Kang, Rick Enns, Kuor Hsin Chang, Clint Powell, José A. Gutierrez, Ludwig Winkel] Companies [Dust Networks, Freescale, Emerson, Siemens AG] Address [30695 Huntwood Avenue, Hayward, CA USA; 890 N. McCarthy Blvd, Suite 120, Milpitas, CA USA; 8000 West Florissant Avenue St. Louis, Missouri USA; Siemensallee 74, Karlsruhe, Germany] Voice:[+1 (510) , +1 (650) , +1 (408) , +1 (480) , +1 (314) , +49 (721) ] Kuor- ] Re: [n/a] Abstract: [This document proposes extensions for IEEE MAC] Purpose: [This document is a response to the Call For Proposal, IEEE P ] 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 Kris Pister et al. Page 1 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Time Slotted, Channel Hopping MAC (TSCH) Kris Pister – UC Berkeley/Dust Networks Chol Su Kang Dust Networks Kuor Hsin Chang - Freescale Rick Enns - Consultant Clinton Powell - Freescale José A. Gutierrez – Emerson Ludwig Winkel – Siemens September, 2008 Kris Pister et al. Page 2 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Target Applications Industrial and commercial applications with a particular focus on: Equipment and process monitoring Non-critical control Diagnostics/predictive maintenance Asset management Kris Pister et al. Page 3 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Requirements Industrial-Grade Reliability and robustness in the presence of multipath, path obstructions and interference Industrial and commercial environments Sustained operation in the presence of non-standards based communications systems Long operational life for battery powered devices (> 5 years) Co-existence Flexible and scale-able Easy wireless network deployment and maintenance Kris Pister et al. Page 4 <author>, <company> <author>, <company>

TSCH- Accepted, Proven & Practical
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 TSCH- Accepted, Proven & Practical Time Slotted, Channel Hopping (TSCH) technology is the basis for the wireless network of two industrial standards HART Foundation ( - over 200 industrial companies worldwide): WirelessHART- published 9/07 ISA ( – over 30,000 members worldwide): ISA100 Committee, ISA100.11a working group- in working group draft TSCH has been implemented by multiple companies on multiple 2.4 GHz IEEE std platforms Kris Pister et al. Page 5 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Timeslot Access Slot Frame Cycle Unallocated Slot Allocated Slot Tx CCA: RX startup, listen, RX->TX Transmit Packet: Preamble, SFD, Headers, Payload, CRC RX startup or TX->RX RX ACK Rx RX startup RX packet Verify MIC Calculate ACK MIC Transmit ACK RX/TX turnaround timeslot TX/RX packet TX/RX ACK Devices are configured with a slot frame and timeslots to communicate with each other. Kris Pister et al. Page 6 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Timeslot Basics All devices in the same network synchronize slot frames All timeslots are contained within a slot frame cycle Timeslots repeat in time: the slot frame period Device-to-device communication within a timeslot includes packet Tx/Rx & ACK Tx/Rx Configurable option for CCA before transmit in timeslots Kris Pister et al. Page 7 <author>, <company> <author>, <company>

Timeslot Operation In Devices
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Timeslot Operation In Devices Devices use timeslots to: Schedule when they wakeup to transmit or listen Keep time synchronized Specification on time difference tolerances Time synchronization mechanisms Time the sequence of operations Allow the source and destination to set their frequency channel Listening for a packet Sending a packet Listening for an ACK Generating an ACK Synchronizes channel hops Kris Pister et al. Page 8 <author>, <company> <author>, <company>

Sample Timeslot Processing
<11 January, 2008r> doc.: IEEE <doc#> September, 2008 Sample Timeslot Processing Kris Pister et al. <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Link Types Dedicated Link – assigned to one device for transmission and to one or more devices for reception A dedicated broadcast link is assigned to all devices for reception Shared Link – assigned to more than one device for transmission ACK failures detect collisions A slot based back-off algorithm resolves collisions Kris Pister et al. Page 10 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> doc.: IEEE <doc#> September, 2008 Sample Shared Link Processing Kris Pister et al. <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Channel Hopping Slot n-2 Slot n-1 Slot n Slot n+1 Slot n+2 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Channels Combined with timeslot access to enhance reliability Kris Pister et al. Page 12 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Channel Hopping Mitigate Channel Impairments Channel hopping adds frequency diversity to mitigate the effects of interference and multipath fading Increase Network Capacity One timeslot can be used by multiple links at the same time Kris Pister et al. Page 13 <author>, <company> <author>, <company>

Link = (Timeslot , Channel Offset)
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Link = (Timeslot , Channel Offset) One Slot Time D Chan. offset A BA C CA 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 Kris Pister et al. Page 14 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Channel Hopping Time BA (ch 15) BA (ch25) BA (ch18) CA DA CA DA CA DA Channel Offset BA BA BA BC BC BC BE BF BE BF BE BF ASN= N*4 N*4+1 N*4+2 N*4+3 (N+1)*4 Cycle N+2 Cycle N Cycle N+1 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. Kris Pister et al. Page 15 <author>, <company> <author>, <company>

Timeslot Timing Offsets
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Timeslot Timing Offsets T1 T2 T3 T4 Transmitter CCA TX Packet prepare to receive RX ACK TsCCAOffset TsRxAckDelay AWT TsTxOffset Receiver RX Packet process packet, prepare to ack prepare to receive TX ACK TsRxOffset PWT TsTxAckDelay R1 R2 R3 End of timeslot Start of timeslot = transmitting packet = receiver on Timeslot with Acknowledged Transmission = receiving packet PWT = TsPacketWaitTime AWT = TsAckWaitTime Kris Pister et al. Page 16 <author>, <company> <author>, <company>

Timeslot Timing Offsets (Cont’d)
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Timeslot Timing Offsets (Cont’d) T1 T2 T3 T4 Transmitter CCA TX Packet prepare to receive Idle receive TsCCAOffset TsRxAckDelay AWT TsTxOffset Receiver RX Packet prepare to receive process packet, decide not to ack TsRxOffset PWT R1 R2 End of timeslot Start of timeslot = transmitting packet = receiver on Timeslot with Unacknowledged Transmission = receiving packet PWT = TsPacketWaitTime AWT = TsAckWaitTime Kris Pister et al. Page 17 <author>, <company> <author>, <company>

<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Timeslot Timing Offsets (Cont’d) T1 T2 Transmitter CCA TX Packet no ack expected TsCCAOffset TsTxOffset Receiver RX Packet prepare to receive process packet, decide not to ack TsRxOffset PWT R1 R2 End of timeslot Start of timeslot = transmitting packet = receiver on Timeslot with Unacknowledged Broadcast = receiving packet PWT = TsPacketWaitTime AWT = TsAckWaitTime Kris Pister et al. Page 18 <author>, <company> <author>, <company>

<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Timeslot Timing Offsets (Cont’d) Transmitter idle Receiver prepare to receive Idle rx idle TsRxOffset PWT Receiver idles only for a brief time and decides to turn off receiver quickly. The short Idle listen and the a low duty cycle of a device’s assigned timeslots to the slot frame period produces low energy consumption and long battery life. R1 R2 End of timeslot Start of timeslot Timeslot with Idle Receive = receiver on PWT = TsPacketWaitTime Kris Pister et al. Page 19 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> Time Synchronization September, 2008 Tg Tg Tg Tg Transmit Packet: Preamble, SFD, Headers, Payload, FCS TACK TCCA TProcessing Early Transmit Packet: Preamble, SFD, Headers, Payload, FCS TACK TProcessing TCCA TCCA Transmit Packet: Preamble, SFD, Headers, Payload, FCS Perfect Late Transmit Packet: Preamble, SFD, Headers, Payload, FCS TACK TProcessing TCCA 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. Kris Pister et al. Page 20 <author>, <company> <author>, <company>

Time Synchronization (Cont’d)
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Time Synchronization (Cont’d) Kris Pister et al. Page 21 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 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 Kris Pister et al. Page 22 <author>, <company> <author>, <company>

Time Synchronization (Cont’d)
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 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 A node can be synchronized to more than one parent (i.e. timing reference nodes) Kris Pister et al. Page 23 <author>, <company> <author>, <company>

Non-conflicting Timeslot assignment
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> Non-conflicting Timeslot assignment September, 2008 Devices with multiple radios can be given one or more offsets. Devices can be given one or more slots in a particular slotframe. Devices with multiple radios can be given a block of (slot,offset)s slot Chan. offset Kris Pister et al. Page 24 <author>, <company> <author>, <company>

Non-conflicting timeslot assignment
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> Non-conflicting timeslot assignment September, 2008 Multiple slotframes with different lengths can operate at the same time. 4 cycles of the 250ms slotframe are shown, along with a 1000ms slot frame There are never collisions if the 1000ms slot frame uses only the empty slots of the 250 ms slot frame 250ms 250ms 250ms 250ms 1,000ms Kris Pister et al. Page 25 <author>, <company> <author>, <company>

Added MAC PAN Service Primitives
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 Added MAC PAN Service Primitives Primitive Description Re-quest Con-firm Res-ponse Indica-tion SET-SLOTFRAME Add, delete, or modify a superframe X SET-LINK Add, delete, or modify a link TSCH-MODE Operate in Time Slot Channel Hopping mode LISTEN Start listening for an advertisement This is a list of some of the service primites needed to support the TSCH MAC extentions. Kris Pister et al. Page 26 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> doc.: IEEE <doc#> September, 2008 SET-SLOTFRAME Request (Device Management  TSCH MAC) Add, delete, or change a slotframe Parameters: slotframe Id, operation, slotframe size, channel page, channel map, active flag Confirm (TSCH MAC  Device Management) Reports the results of SET-SLOTFRAME request command Parameters: slotframe Id, status Kris Pister et al. <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> doc.: IEEE <doc#> September, 2008 SET-LINK Request (Network Manager  TSCH MAC) Change, or delete a link Parameters1: operation type=CHANGE, link handle, frame Id, timeslot, channel offset, link options, link type, node addresses Parameters2: operation type=DELETE, link handle Confirm (TSCH MAC  Network Manager) Indicates the result of add, change or delete link command Parameters: status, link handle Kris Pister et al. <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> doc.: IEEE <doc#> September, 2008 TSCH-MODE Request (Device Management  TSCH MAC) Puts the MAC to TSCH mode of operation Parameters: none Confirm (TSCH MAC  Device Management) Reports the result of the TSCH-MODE request Parameters: status Kris Pister et al. <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> doc.: IEEE <doc#> September, 2008 LISTEN Request (Device Management  TSCH MAC) Request the MAC to search for a network Parameters: channel page, channel, duration Confirm (TSCH MAC  Device Management) Reports when the MAC completes the listen operation Parameters: status Indication (TSCH MAC  Device Management) Indicates that the MAC received an ADVERTISEMENT packet while listening Parameters: link quality, PAN ID, channel map, join priority, slotframes, links in each slotframe (these parameters, except link quality, are received in ADVERTISEMENT packet) Kris Pister et al. <author>, <company>

New TX Option in Existing Primitive
<11 January, 2008r> doc.: IEEE <doc#> September, 2008 New TX Option in Existing Primitive MCPS.DATA.request Primitive In TSCH Mode, the Next Higher Layer (NHL) may provide TSCH MAC a list of links. The NHL may choose the links the MSPDU may be transmitted on. The TSCH MAC selects the next available link from the list. Kris Pister et al. <author>, <company>

Example of TSCH Capability
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 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 84kbps MPDU per access point 16 * 84k = Mbps combined payload throughput w/ no spatial reuse of frequency Latency 10ms / PDR (Packet Delivery Rate) per hop: best case Statistical, but well modeled * 10 ms slots are an example – the standard can define a range of slot sizes that can be selected for use Other examples can be constructed that use a different timeslot period. The focus is on the 2.4 GHz band and the OQPSK radio. One reason to not fix the timeslot size is to accomodate other radios. Channel blacklisting reduces the number of channels available the the network throughput. Spacial reuse allows link assignments to be reused when devices are sufficiently separated so as not to interfer when the transmit on the same channel at the same time. The combined payload throughput calculated here does not take into accound any spacial reuse. Channel availablity can be modeled to determin the latency distribution over various RF environments. Kris Pister et al. Page 32 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 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 -Sample and reporting rate: Pick a slot frame that best meets the needs of the applications. The reporting rate can be adjusted by assigning more then one slot per slot frame for transmission. -Low latency can be accomodated in several ways: Low slot frame periods More transmission slots per slot frame Cascaded timeslot assignments: for each hop the transmit timeslot closely follows the receive timeslot -Reliability is enhanced by providing additional retransmission timeslots beyond those needed to meet the application‘s bandwidth requirements. Additional transmission timeslots can also be used to provide path redundancy when a neighbor has failed or is blocked. -The number of transmission timeslots per sedond assigned to a device determins the maximum throughput. The practical throughput depends on the retransmission rate of the device accross the channels used by the network. -Highbandwidth devices can use sort period slot frames or multiple timeslot assignments per slot frame to achieve high bandwidth. Multiple radios can also be used to transmit on more than one channel at a time. -Dynamic allocation of resources is achieved by configuring new slot frames and timeslot assignments on an scheduled basis or an event driven basis. Example the periodic uploading of a large vibration monitoring file can be scheduled by turning on a highbandwidth slot frame. -When a line powered device is available, it can be assigned a large number of timeslots for reception and transmission.reducing the packet latencies. Kris Pister et al. Page 33 <author>, <company> <author>, <company>

doc.: IEEE 802.15-<doc#>
<11 January, 2008r> <11 January, 2008r> doc.: IEEE <doc#> doc.: IEEE <doc#> September, 2008 TSCH Summary Proven technology- aligns with several industrial wireless standards Meets the requirement for commercial and industrial monitor and process control applications Extends the capabilities of the existing IEEE MAC Kris Pister et al. Page 34 <author>, <company> <author>, <company>

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