doc.: ieee 802.15-11-0597-01-004k submission etri sep 2011 slide 1 project: ieee p802.15 working...
TRANSCRIPT
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)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: [[email protected]]
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.
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
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
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
doc.: IEEE 802.15-11-0597-01-004k
Submission
ETRI
Sep 2011
Slide 5
Contention-free
Low Energy Link Access
(11-0599-00-00k)
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
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
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
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• TA =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
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
175uA18.5mA
25.8mA
sleep waiting RX TX
25.8mA
TX
22.3mA
waiting
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 ?
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*214 = 262,144 slots• base slot duration = 60 symbols• base slot length (sec) = 60symbols/symbol rate
beacon beacon
BI = 2BO *aBaseSuperframeDuration
SD=2SO *aBaseSuperframeDuration
TS 0x10TS 0x11 TS 0x1fTS 0x0fTS 0x01TS 0x00
beacon beacon
2BO-SO th superframe
16*2BO-SO-1
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.
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
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
B B B B B B B B
512 superframes, 8,192 slots
2,343 beacons in 24 hours
assigned to device
i
assigned to device
i
assigned to device
i
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 beacon
TS 0x10 TS 0x11 TS 0x1fTS 0x0fTS 0x01TS 0x00
beacon beacon
16*2BO-SO-1
coordinator
TS 0x10 TS 0x11 TS 0x1fTS 0x0fTS 0x01TS 0x0016*2BO-SO-1
devicegr2 access
data
wakeup
sleep
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 0x10 TS 0x11 TS 0x1fTS 0x0fTS 0x00
beacon
16*2BO-SO-1
coordinator
devicegr1 link
data
wakeup
sleep
beacon
TS 0x01
beacon
TS 0x10 TS 0x11 TS 0x1fTS 0x0fTS 0x00
beacon
16*2BO-SO-1 TS 0x01
data
wakeup
sleep
beacon
wakeup
sleep
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 0x10 TS 0x11 TS 0x1fTS 0x0fTS 0x00
beacon
16*2BO-SO-1
coordinator
devicegr1 link
data
wakeup
sleep
beacon
TS 0x01
beacon
TS 0x10 TS 0x11 TS 0x1fTS 0x0fTS 0x0016*2BO-SO-1
TS 0x01
dACK data
wakeup
sleep
dACK
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 0x10 TS 0x11 TS 0x1fTS 0x0fTS 0x00
beacon
16*2BO-SO-1
coordinator
beacon
TS 0x01
beacon
BS MS1 MS2 BS BS
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
doc.: IEEE 802.15-11-0597-01-004k
Submission
ETRI
Sep 2011
Slide 21
Provide a Tool
for Time-Stamping
(11-0598-00-00k)
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”
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
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)
B B B B B B B B
512 superframes, 8,192 slots
2,343 beacons in 24 hours
assigned to device
i
assigned to device
i
assigned to device
i
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)
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 ACKwake up
sleep
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 ACKwake up
sleep
doc.: IEEE 802.15-11-0597-01-004k
Submission
ETRI
Sep 2011
Slide 28
Level 1 Time Synchronization (II)
BI BI*2Wo
coordinator
device
adjust clock
adjust clock
doc.: IEEE 802.15-11-0597-01-004k
Submission
ETRI
Sep 2011
Slide 29
Level 1 Time Synchronization (III)
device
device
adjust clock
adjust clock adjust clock
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
datamanagement
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
doc.: IEEE 802.15-11-0597-01-004k
Submission
ETRI
Sep 2011
Slide 32
Low-energy
Link Management
(11-0600-00-00k)
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
coordinatorrepeater
device
near node
far node
linear
group
distributed
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
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
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
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
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
coordinator
device
DeviceStausRepReq
measure RSSI, LQIadjust TX power level
DeviceStausRep
DeviceStausRepReq (RSSI, LQI)adjust TX power level
DeviceStausRep
near node
far node
hidden node
contention node
coordinator
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 0x10 TS 0x11 TS 0x1fTS 0x0fTS 0x00
beacon
16*2BO-SO-1
coordinator
beacon
TS 0x01
beacon
BS MS1 MS2 BS BS
doc.: IEEE 802.15-11-0597-01-004k
Submission
ETRI
Sep 2011
Slide 40
LECIM MAC Procedure
coordinator
device
Beaconget BO, SO, MO, set WO
estimate next beacon arrival timeBeacon
adjust clock driftsleep
Beacon
Beaconwakeup at BI*2WO
wait beaconadjust clock driftDeviceStatusRepReq/
DeivceLinkControlmanage device link infor
DeviceStausRep sleep
Datawakeup at device time slot
tx data with grade0 linkwait ACK
ACK
Data wakeup at device time slottx data with grade2 link
sleep
i) join to LECIM network
ii) link management
iii) data transmission
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
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
doc.: IEEE 802.15-11-0597-01-004k
Submission
ETRI
Sep 2011
Slide 43
Thanks for your Attention!