1. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [MAC Proposal for Low-Energy Wide Area Monitoring] Date Submitted: [Sep 15, 2011] Source: [Seong-Soon Joo, Jong-Arm Jun, Cheol-Sig Pyo] Company: [ETRI] Address: [161 Gajeong-dong, Yuseong-gu, Daejeon, KOREA] Voice: [+82-42-860-6333], FAX: [+82-42-860-4197], E-Mail: [ssjoo@etri.re.kr] Re: [IEEE 802 TG4k issues a call for proposal] Abstract: [A MAC for low-energy wide area monitoring is proposed.] Purpose:[To contribute the initial process of preparing draft for TG4k] 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. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 2 MAC Proposal for Low-Energy Wide Area Monitoring Seong-Soon Joo*, Jong-Arm Jun, Cheol-Sig Pyo ETRI

3. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 3 Requirements on LECIM MAC Design goals of wide area monitoring –long lived infra more than 10 years life like network carrier’s infra –ease maintained monitoring network high degree of freedom to start the monitoring/maintenance business Design requirements on LECIM MAC –guaranteed link access on low duty cycle with low energy –minimize contention on a link –support to fair access between near and far nodes –time-stamping –support to ease installation –support to ease maintenance –support to make network structure simple –optimized to network configuration near node far node hidden node contention node coordinator

4. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 4 Major Contribution Provide a tool for time-stamping –global time synchronization –adjust clock drift with light overhead Contention-free low energy link access –distribute access loads on slotted link –three grades of link access Extend reaches of link –echo back a frame –two modes of link repeater Low-energy link management –management frame from coordinator for optimized configuration and ease maintenance –link power management

5. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 5 Contention-free Low Energy Link Access (11-0599-00-00k)

6. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 6 LECIM MAC Design Major design goals for LECIM MAC –long lived infra  low energy consumption –ease maintained infra  carrier grade network management Design considerations –low energy consumption find a balance between data transmission throughput and duration of sleep –carrier grade network management light and a certain level of reliable & real-time downward link upward link for supporting alarming events

7. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 7 MAC Design Criteria Measuring the energy efficiency of MAC –energy consumption on LECIM network sum of active working duration of nodes in network –LECIM network throughput sum of the frame length of successfully transmitted frames in network –efficiency = energy consumption/network throughput Measuring the availability of upward and downward link –delay time to obtain the access right to a link –energy consumption for getting an access right –link availability = delay time * energy consumption

8. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 8 Energy Consumption on a Device (I) Device power states –MCU active mode standby mode –RF PHY low power mode active mode –wait for sync –receiving –transmitting Active working duration in RF PHY –sleep to active time to activate regulator, stabilize the XOSC –wait for signal (synch) varying on the MAC algorithm –receiving length in bit from preamble to FCS * symbol/bit –transition from receiving to transmitting or vice versa turnaround time –transmitting length in bit from preamble to FCS * symbol/bit –active to sleep

9. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 9 Energy Consumption on a Device (II) energy consumption on RF PHY –consumed energy (J) for 1hr duration in a device = (∑ duration * current for sleep + ∑ duration * current for transition + ∑ duration * current for waiting+ ∑ duration * current for receiving + ∑ duration * current for transmitting) * voltage Ref.: power consumption MCU and RF PHY –MSP430x5xx Family typical current consumption Active Mode : –Flash program execution : 230uA/MHz at 8MHz –RAM program execution : 110uA/MHz at 8MHz –165uA/MIPS Standby mode, LPM3 (CPU, MCLK, SMCLK, FLL off) : 2.1uA RTC with Crystal –CC2520 typical current consumption T A =25°C, VDD=3.0V, fc=2440MHz Low Power Mode Current –LPM1 (XOSC off, digital regulator on): 175uA –LPM2 (XOSC off, digital regulator off): 30nA Receive current –wait for frame : 22.3mA –receiving frame (-50dBm input) : 18.5mA Transmit current –0 dBm TX : 25.8mA –5 dBm TX : 33.6mA

10. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 10 Energy Consumption on a Device (III) energy consumption on a device energy consumption on LECIM network –sum of active working duration of nodes in network –reduce waiting time as possible as can for transmitting 128byte PPDU on 40kbps link, 25.6ms –reduce retrials on RX and TX as possible as can do not make a situation that RX or TX is interrupted 22.3mA 175uA 18.5mA 25.8mA sleepwaitingRXTX 25.8mA TX 22.3mA waiting

11. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 11 Link Access for LECIM reduce waiting time –devices aware when wake up to receive or transmit –link access for RX waiting until event happened request to send frame, and wait for limited time wake up for receiving reduce retrials on RX and TX –preemptive RX or TX time slot based link resource allocation –need time synchronization processing –need prior time slot allocation processing how to minimize overhead ?

12. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 12 Slot Based Access for LECIM (I) slots for LECIM network –to assign a preemptive slot for a device, need over 1,000 time slots –for ease manageable network, require ease to increase time slots Multi-frame Order in DSME of TG4e –repeat the superframe in beacon interval –max number of slot in beacon interval with CAP reduction mode, 16*2 14 = 262,144 slots base slot duration = 60 symbols base slot length (sec) = 60symbols/symbol rate beacon BI = 2 BO *aBaseSuperframeDuration SD=2 SO *aBaseSuperframeDuration TS 0x10TS 0x11TS 0x1f TS 0x0f TS 0x01 TS 0x00 beacon 2 BO-SO th superframe 16*2 BO-SO -1

13. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 13 Slot Based Access for LECIM (II) slot length –minimum length for RX/TX a frame with max PPDU 128byte PPDU on 40kbps link, 25.6ms –need longer slot length for receiving ACK within the same slot multiple frames RX/TX in a slot Superframe Order –superframe order determines the length of time slot –BPSK, data rate 20kbps base slot length = 3ms SO > 5 for RX/TX a frame with 128byte PPDU 8, 192 slots available, when BO is 14 –enough slots for assigning to each LECIM devices But, how to minimize the allocation overhead –in DSME, exchange DSME-GTS request and response commands –prior to request the time slot allocation, need association completed.

14. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 14 Slot Based Access for LECIM (III) implicit slot allocation –need no command frames exchange –slot number can assigned off-line, or calculated on-line –based upon the device identifier manufacture's product sequential # IEEE OUI, 64bit address –if available time slot is larger than the number of devices device identifier modulo number of time slots –else, provides prioritized multiple slots hashing function 1 (device identifier) % number of time slot hashing function 2 (device identifier) % number of time slot … assigned slot number –superframe ID + time slot ID

15. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 15 Slot Based Link Access (I) slots for devices –BPSK, data rate 20kbps BO = 14, SO = 5, MO = 9 –512 superframes, 8,192 slots slot length = 96ms, BI = 786,432ms length of superframe = 1,536ms number of master beacons in 24hour = 457 total number of beacons in 24hour = 2,343 a device has 457 chances to access a slot every 1,536ms per a day BBBBBBBB 512 superframes, 8,192 slots 2,343 beacons in 24 hours assigned to device i

16. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 16 Slot Based Link Access (II) upward link access –three grades of up-link access –grade 0: real-time transmission (emergent access) –grade 1: reliable transmission –grade 2: loss tolerant transmission grade 2 –MCU on, find the coming nearest master beacon –wake up at the start of assigned slot of superframe –transmit a frame without CCA, and sleep beacon TS 0x10TS 0x11TS 0x1f TS 0x0f TS 0x01 TS 0x00 beacon 16*2 BO-SO -1 coordinator TS 0x10TS 0x11TS 0x1f TS 0x0f TS 0x01 TS 0x00 16*2 BO-SO -1 device gr2 access data wakeup sleep

17. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 17 Slot Based Link Access (III) grade 1 –step1: MCU on, find the coming nearest master beacon –step2: wake up at the start of assigned slot of superframe –step3: transmit a frame with CCA, and sleep to next beacon or device management slot –step4: wake up at beacon slot or management slot, check ACK/NACK –step5: if failed, retry transmission with CCA on next candidate slot –repeat steps 2~5 until retrial counter is over beacon TS 0x10TS 0x11 TS 0x1f TS 0x0fTS 0x00 beacon 16*2 BO-SO -1 coordinator device gr1 link data wakeup sleep beacon TS 0x01 beacon TS 0x10TS 0x11 TS 0x1f TS 0x0f TS 0x00 beacon 16*2 BO-SO -1 TS 0x01 data wakeup sleep beacon wakeup sleep

18. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 18 Slot Based Link Access (IV) grade 0 –step1: wake up, transmit a frame without CCA, wait ACK –step2: if failed, sleep to the nearest slot of all the assigned slots –step3: wake up at the start of assigned slot, transmit a frame without CCA, and wait ACK –repeat steps 2~3 until retrial counter is over beacon TS 0x10TS 0x11 TS 0x1f TS 0x0f TS 0x00 beacon 16*2 BO-SO -1 coordinator device gr1 link data wakeup sleep beacon TS 0x01 beacon TS 0x10TS 0x11 TS 0x1f TS 0x0f TS 0x00 16*2 BO-SO -1 TS 0x01 dACK data wakeup sleep dACK

19. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 19 Slot Based Link Access (V) downward link access –broadcast down-link –unicast down-link broadcast down-link –beacon slot –management slot bidirectional link number of slots are predefined unicast down-link –assigned slot to a device –periodic open or device/coordinator request based open beacon TS 0x10TS 0x11 TS 0x1f TS 0x0f TS 0x00 beacon 16*2 BO-SO -1 coordinator beacon TS 0x01 beacon BSMS1MS2 BS

20. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 20 Amendment to TG4e MAC PIB –add macUplinkGrade MAC primitive & command –add MCPS-LECIM-DATA MAC frame format –short frame header –consecutive multiple frames

21. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 21 Provide a Tool for Time-Stamping (11-0598-00-00k)

22. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 22 Time and Low Energy Wide Area Monitoring (I) synchronized measuring –the times of occurrence of physical events often crucial for the observer to associate event reports with the originating physical events need accurate time-stamping of measured quantities –acoustic leak detection mechanisms that can pinpoint the location of a leak given a known speed-of-sound through a pipe. –synchro-phasor measurements relative phase relationship between current and voltage at various locations can be measured if an absolute time basis is communicated to multiple end-points. –determining location of sensor nodes based on the measurement of time of flight or difference of arrival time of certain signals also require finely synchronized time. –distributed observations into a coherent estimate of the original phenomenon requires accurate time-stamping. source: Mark Wilbur, IEEE 15-11-0397-00-004k, “Time Synchronization in Wireless Sensor Networks”

23. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 23 Time and Low Energy Wide Area Monitoring (II) global time synchronization for time-stamping –need global master time clock for synchronizing distributed devices’ local time clock periodical time synchronization for compensating local clock drift over-the-air time synchronization –coordinator is power-free may have high precision clock afford to transmit clock information periodically in any time scale –adjust clock drift of a local device based upon coordinator master clock beacon frame as a global clock tick –need a message to broadcast global clock time –beacon interval can be clock leap second –use sequence number of beacon frame for clock sampling

24. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 24 time expression in LECIM network –multi-superframe of TG4e DSME MAC sequence # of master beacon superframe ID slot ID –precision of clock tick length of slot BPSK, data rate 20kbps (BO = 14, SO = 5, MO = 9) –96ms Time and Low Energy Wide Area Monitoring (III) BBBBBBBB 512 superframes, 8,192 slots 2,343 beacons in 24 hours assigned to device i

25. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 25 time synchronization –initiate time synchronization –in phase with the global time clock –recover from the loss of time synchronization how to achieve low energy time synchronization? –advantage of power-free coordinator –balancing the energy consumption with precision of clock –virtue of multi-superframe structure Time and Low Energy Wide Area Monitoring (IV)

26. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 26 Level 0 Time Synchronization initiate time synchronization –two options find beacon request global time –dependent on PHY power consumption on RX and TX symbol rate request global time –device requests synchronized global time use grade 0 link LECIM MAC management command frame: SyncReq –coordinator responds with current global time ACK frame (seq. # of master beacon, superframe ID, slot ID) device coordinator SyncReq ACK wake up sleep

27. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 27 Level 1 Time Synchronization (I) clock drift compensation –two options periodical wake up request global time –dependent on usage of links need operation and maintenance command and control for LECIM frequency of measuring events device coordinator SyncReq ACK wake up sleep

28. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 28 Level 1 Time Synchronization (II) BI BI*2 Wo coordinator device adjust clock

29. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 29 Level 1 Time Synchronization (III) device adjust clock

30. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 30 Level 2 Time Synchronization implicit exchange of time information –frame from the coordinator receive management frame transmitted on management slot compensate clock drift with estimated time of management slot –device : (estimated current seq. # of master beacon, superframe ID, slot ID) –received: (seq. # of master beacon, superframe ID, slot ID) –frame from a device receive data frame, command frame transmitted on device slot save the time of slot at which frame is received device coordinator data management

31. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 31 Amendment to TG4e MAC PIB –extend macBSN –add macWakeupOrder MAC management primitive & command –add MLME-TIME-SYNC –add Time synchronization request command MAC frame format –short frame header –beacon format

32. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 32 Low-energy Link Management (11-0600-00-00k)

33. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 33 LECIM Network Reference Model Components of LECIM network –coordinator, device –repeater Topology of LECIM network –near node, far node –linear, group, distributed –range coordinator repeater device near node far node linear group distributed

34. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 34 LECIM Network Data Model (I) Traffic in a device –upward sensing data device status report device join device alarming –downward data ACK time synchronization device management command Traffic in LECIM network –attributes number of devices feature of device: data size, frequency interference model, contention probability –traffic in busy hour –traffic in off hour

35. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 35 LECIM Network Data Model (II) Data in LECIM network –sensing/measuring data contents –device/location ID : 2 ~ 4 bytes –time stamp : 2 ~ 4 bytes, (NTP : 8~ 16 bytes) –monitoring data vector data : 1 ~ 100 bytes stream data : 4 Kbyte x n frame/s frequency in appearance –periodic data : 1 ~ 1,440 event/day –occasional data : –operation & management data device maintenance data –device installation –device fault diagnosis & maintenance network operation data –global clock time synchronization –device status check

36. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 36 Possible Infra Structures Star topology –power free collector –multi-channel transceivers in a collector –synchronized/asynchronous resource allocation –power management on end point –identify operators at PHY or MAC layer Multi-hop topology with repeater –synchronized resource allocation for each hop –upward/downward forwarding at the MAC layer operator 1 operator n

37. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 37 Link Repeater Extend reaches of link –varying RF environment from/to coordinator –devices are located sparsely –extend reaches of link from/to coordinator Link repeater –echo back a frame after receiving a frame from the coordinator or devices –link repeater is power-free or located at ease maintainable place –two modes of link repeater according to the limitation on power resource device repeater coordinator

38. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 38 Power Management Link power management –reduce interference range –adaptable to radio environmental variance –extend life of near end device Power control procedure –measure the distance to coordinator detect radio energy from coordinator adjust TX power level reply back to coordinator –feedback from coordinator adjust TX power level coordinatordevice DeviceStausRepReq measure RSSI, LQI adjust TX power level DeviceStausRep DeviceStausRepReq (RSSI, LQI) adjust TX power level DeviceStausRep near node far node hidden node contention node coordinator

39. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 39 Link for Management management links –broadcast down-link –bidirectional management slot link –bidirectional device owned slot link broadcast down-link –management data on beacon bidirectional management slot link bidirectional link number of slots are predefined bidirectional device owned slot link –assigned slot to a device –periodic open or device/coordinator request based open beacon TS 0x10TS 0x11 TS 0x1f TS 0x0f TS 0x00 beacon 16*2 BO-SO -1 coordinator beacon TS 0x01 beacon BSMS1MS2 BS

40. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 40 LECIM MAC Procedure coordinatordevice Beacon get BO, SO, MO, set WO estimate next beacon arrival time Beacon adjust clock drift sleep Beacon wakeup at BI*2 WO wait beacon adjust clock drift DeviceStatusRepReq/ DeivceLinkControl manage device link infor DeviceStausRep sleep Data wakeup at device time slot tx data with grade0 link wait ACK ACK Data wakeup at device time slot tx data with grade2 link sleep i) join to LECIM network ii) link management iii) data transmission

41. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 41 Amendment to TG4e MAC PIB –add macLECIMlinkInfor MAC management primitive & command –add MLME-LECIM-STATUS –add MLME-LECIM-LINK –add device status report command MAC frame format –beacon format

42. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 42 Next Steps Agree to move forward (include in baseline) Explore and validate –light overhead frame format –optimal wake up order based upon the TG4k PHY –link repeater –power management Begin drafting

43. doc.: IEEE 802.15-11-0597-01-004k Submission ETRI Sep 2011 Slide 43 Thanks for your Attention! ssjoo@etri.re.kr