doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 1 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, Kuor Hsin Chang, Rick Enns, 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 (408) , +1 (650) , +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

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 2 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

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 3 Target Applications Industrial and commercial applications with a particular focus on: Equipment and process monitoring Non-critical control Diagnostics/predictive maintenance Asset management

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 4 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

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 5 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 companies worldwide): WirelessHART- published 9/07www.hartcomm2.org –ISA ( – over 30,000 members worldwide): ISA100 Committee, ISA100.11a working group- in working group draftwww.isa.org TSCH has been implemented by multiple companies on multiple 2.4 GHz IEEE std platforms

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 6 Timeslot Access Slot Frame Cycle Unallocated SlotAllocated Slot Tx Rx RX startup Transmit Packet: Preamble, SFD, Headers, Payload, CRC RX packetVerify MIC Calculate ACK MIC Transmit ACK RX startup or TX->RX RX ACK RX/TX turnaround CCA: RX startup, listen, RX->TX timeslot Devices are configured with a slotframe and timeslots to communicate with each other. TX/RX packet TX/RX ACK

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 7 Timeslot Basics All devices in the same network synchronize slotframes All timeslots are contained within a slotframe cycle Timeslots repeat in time: the slotframe period Device-to-device communication within a timeslot includes packet Tx/Rx & ACK Tx/Rx Configurable option for CCA before transmit in timeslots

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 8 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 Provide time to higher layers

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 9 Sample Timeslot Processing

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 10 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

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 11 Sample Shared Link Processing

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 12 Channel Hopping Combined with timeslot access to enhance reliability Channels Slot n Slot n-1 Slot n-2 Slot n+1 Slot n+2

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 13 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

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 14 BABA BCBC BABA CADACADA BEBFBEBF B C Link = (Timeslot, Channel Offset) A Time Chan. offset One Slot D 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 FE

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 15 B  A (ch 15) BEBFBEBF BCBC BABA CADACADA B  A (ch25) BCBC BABA BEBFBEBF CADACADA B  A (ch18) BCBC BABA CADACADA BEBFBEBF Channel Hopping 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 Channel Offset N*4 Cycle N Cycle N+1 Cycle N+2 N*4+1(N+1)*4N*4+2N*4+3 ASN=

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 16 Timeslot Timing Offsets End of timeslot Start of timeslot TsCCAOffset CCA TsTxOffset RX Packet TX Packet TX ACK TsRxOffset PWT prepare to receive TsTxAckDelay TsRxAckDelay AWT RX ACK prepare to receive process packet, prepare to ack Timeslot with Acknowledged Transmission T1 T2 T4 T3 R1 R2R3 Transmitter Receiver = transmitting packet = receiver on PWT = TsPacketWaitTime AWT = TsAckWaitTime = receiving packet

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

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

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 19 Timeslot Timing Offsets (Cont’d) End of timeslot Start of timeslot TsRxOffset PWT prepare to receive idle Idle rx Timeslot with Idle Receive R1 R2 Transmitter Receiver idle = receiver on PWT = TsPacketWaitTime

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 20 Time Synchronization Tg Transmit Packet: Preamble, SFD, Headers, Payload, FCS T ACK T C CA T Processing Early Late Perfect Tg Timeslot Period T comm = T TXPacket +T Processing +T ACK T Processing 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. Transmit Packet: Preamble, SFD, Headers, Payload, FCS T ACK T Processing T C CA Transmit Packet: Preamble, SFD, Headers, Payload, FCS T ACK T Processing T C CA Transmit Packet: Preamble, SFD, Headers, Payload, FCS T C CA

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 21 Time Synchronization (Cont’d)

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 22 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 TimeAdj = Expected Timing – Actual measured Timing 4.Receiver informs the sender TimeAdj 5.Transmitter adjusts its clock by TimeAdj

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 23 Time Synchronization (Cont’d) Received Packet-based Synchronization 1.Receiver timestamps the actual timing of the reception of start symbol 2.Receiver calculates TimeAdj = TimeExpected (expected arrival time) – Actual timing 3.Receiver adjusts its own clock by TimeAdj A node can be synchronized to more than one parent (i.e. timing reference nodes)

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 24 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 slotframe. Devices with management ability can be given a block of (slot,offset)s Chan. offset slot

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 25 Non-conflicting timeslot assignment 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 1,000ms 250ms

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 26 Added MAC PAN Service Primitives PrimitiveDescriptionRe- quest Con- firm Res- ponse Indica -tion SET-SLOTFRAME Add, delete, or modify a superframe XX SET-LINK Add, delete, or modify a link XX TSCH-MODE Operate in Time Slot Channel Hopping mode XX LISTEN Start listening for an advertisement XXX

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 27 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

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 28 SET-LINK Request (Device Management  TSCH MAC) –Add, change, or delete a link –Parameters1: operation type=ADD or CHANGE, link handle, frame Id, timeslot, channel offset, link options, link type, node addresses –Parameters2: operation type=DELETE, link handle Confirm (TSCH MAC  Device Management) –Indicates the result of add, change or delete link command –Parameters: status, link handle

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 29 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

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 30 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)

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 31 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.

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 32 Examples 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 Radio duty cycle (power consumption) –Near theoretical limit for networks with moderate to high traffic –~0.02% for very low traffic networks 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

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 33 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

doc.: IEEE e Submission September, 2008 Kris Pister et al.Slide 34 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