1. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Slot Based Link Access for Low-Energy Wide Area Monitoring]
Date Submitted: [Sep 15, 2011]
Source: [Seong-Soon Joo, Tae-Wook Heo, Jong-Arm Jun]
Company: [ETRI]
Address: [161 Gajeong-dong, Yuseong-gu, Daejeon, KOREA]
Voice: [ ], FAX: [ ],
Re: [IEEE 802 TG4k issues a call for proposal]
Abstract: [Global time synchronization 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 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
<author>, <company>

2. Slot Based Link Access for Low-Energy Wide Area Monitoring
<month year>
doc.: IEEE <doc#>
Slot Based Link Access for Low-Energy Wide Area Monitoring
Seong-Soon Joo*,
Tae-Wook Heo, Jong-Arm Jun
ETRI
<author>, <company>

3. 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

4. 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

5. Energy Consumption on a Device (I)
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
active to sleep
Device power states
MCU
active mode
standby mode
RF PHY
low power mode
wait for sync
receiving
transmitting

6. 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

7. Energy Consumption on a Device (III)
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
25.8mA
25.8mA
22.3mA
22.3mA
18.5mA
175uA
sleep
waiting RX TX TX
waiting

8. Link Access for LECIM reduce waiting time reduce retrials on RX and TX
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 ?

9. 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
BI = 2BO *aBaseSuperframeDuration
SD=2SO *aBaseSuperframeDuration
2BO-SO th superframe
beacon
beacon
beacon
beacon
TS 0x00
TS 0x01
TS 0x0f
TS 0x10
TS 0x11
TS 0x1f
16*2BO-SO-1

10. 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.

11. 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

12. 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
2,343 beacons in 24 hours
512 superframes, 8,192 slots B B
assigned to device i
assigned to device i
assigned to device i

13. 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
coordinator
beacon
beacon
beacon
beacon
TS 0x00
TS 0x01
TS 0x0f
TS 0x10
TS 0x11
TS 0x1f
16*2BO-SO-1
wakeup
device
gr2 access
data
TS 0x00
TS 0x01
TS 0x0f
TS 0x10
TS 0x11
TS 0x1f
16*2BO-SO-1
sleep

14. 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 0x01
beacon
coordinator
beacon
beacon
TS 0x00
TS 0x0f
TS 0x10
TS 0x11
TS 0x1f
16*2BO-SO-1
TS 0x01
data
wakeup
sleep
wakeup
data
wakeup
sleep
device
gr1 link
beacon
beacon
sleep
TS 0x00
TS 0x0f
TS 0x10
TS 0x11
TS 0x1f
16*2BO-SO-1

15. 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 0x01
beacon
coordinator
beacon
beacon
TS 0x00
TS 0x0f
TS 0x10
TS 0x11
TS 0x1f
16*2BO-SO-1
TS 0x01
data
wakeup
sleep
data
wakeup
sleep
device
gr1 link
dACK
dACK
TS 0x00
TS 0x0f
TS 0x10
TS 0x11
TS 0x1f
16*2BO-SO-1

16. Slot Based Link Access (V)
downward link access
broadcast down-link
unicast down-link
beacon slot
management slot
bidirectional link
number of slots are predefined
assigned slot to a device
periodic open or device/coordinator request based open
beacon
TS 0x01 BS
MS1
MS2 BS BS
beacon
coordinator
beacon
beacon
TS 0x00
TS 0x0f
TS 0x10
TS 0x11
TS 0x1f
16*2BO-SO-1

17. Amendment to TG4e MAC PIB MAC primitive & command MAC frame format
add macUplinkGrade
MAC primitive & command
add MCPS-LECIM-DATA
MAC frame format
short frame header
consecutive multiple frames

18. Thanks for your Attention! ssjoo@etri.re.kr