Motivated by the active developments on the industrial automated world and the new technologies arising in the area of Internet of Things, the IETF, based on IEEE’s existing standards, and some already accepted protocols, propose a new architecture to satisfy the needs of both fields. 6tisch, the new IETF’s architecture to be studied during our project, aims to give a convergent solution for both fields that have plenty of common points. It aims to satisfy the requirements of the wireless low powered lossy networks. Among them, we can point out: energy management policy, energy efficient design, link reliability, robustness, scalability support, interoperability, self organization, end to end reliability, security and mobility support, as the most noticeable ones. The project proposed aims to obtain a well founded experience on how the newly developed architecture 6tisch performs in the OpenWSN project. The partner enterprise wants to quantify the energy consumed by the motes in a real use case, with special detail on how the different parameterizations of the protocol stack would affect it. Due to the increasing need of networks relying on low energy consumption, our project will analyze from the lowest layers of the protocol stack how 6tish architecture performs energywise and how the different mechanisms like routing table construction, message forwarding function, scheduling of the TSCH slots, and many others will perform.

1. Institut Mines-Télécom
P805 – Energy consumption study
of a Wireless Sensor Network
Cristina LUCACI
Federico SISMONDI
Wi6LABS :
Ludovic CHARPENTIER
Julien SAINT-MARTIN
Tutors :
Géraldine TEXIER
Tanguy KERDONCUFF

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Agenda
 WSN application
 Introduction to 6TiSCH architecture and OpenWSN project
 Measuring methodology
 Tests: presentation, measurements and analysis
 Conclusion
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WSN example
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Source: http://www.cs.iit.edu/~winet/images/projects/greenObs-logo.jpg
Source http://www.libelium.com/wireless_sensor_networks_to_detec_forest_fires/

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WSN application
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Temp
Sensor
Temp
Sensor
S S
S
Lumin.
Sensor
Heating
Automated
blind
Root
Automated
blind
Automated
blind
Lumin.
Sensor
SS
SS SS

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Lower layers problems in WSN
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Source: IETF 6TiSCH, a New Standardization Effort to Combine IPv6 Connectivity with Industrial Performance, Xavier Vilajosana, UC Berkeley
Limiting factors:
 Interference in the wireless medium
 Half-duplex transceivers on the sensor
nodes

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IEEE 802.15.4e TSCH
Time Slotted Channel Hopping
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Source: IETF 6TiSCH, a New Standardization Effort to Combine IPv6 Connectivity with Industrial Performance, Xavier Vilajosana, UC Berkeley
Channel hopping mitigates:
 Multipath fading
 External interference

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6 TiSCH architecture
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Source 2: T.Watteyne, X.Vilajosana : OpenWSN: A standards-Based Low-Power Wireless Devepment Environment
Source1: IETF 6TiSCH, a New Standardization Effort to Combine IPv6 Connectivity with Industrial Performance
Xavier Vilajosana, UC Berkeley

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OpenWSN and hardware used
 Open source project developed by University of Berkeley
 Provides the full stack for the 6TiSCH architecture
 Provides the following tools :
• Firmware for the mote TelosB
• A web interface for monitoring and interacting with the network
 Hardware: Motes TelosB
• Low-power MCU
• Energy capacity around 2500 mAh
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Which tasks and which mechanisms implemented are
the most expensive in terms of energy consumption.
Which parameters of the communications stack will
affect the energy consumption.
Implementation of TESTs: Allows us to test the
framework OPENWSN and 6TiSCH mechanisms
Determine how the 6tisch architecture performs
energy-wise in OPENWSN implementation
Objectives of Project

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Measuring methodology
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Radio ON Radio OFF
MCU
On Tradio (TRx+TTx) TMCU
MCU
Idle
n/a Tsleep

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Measuring methodology
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Tests
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• Default OpenWSN implementation
• Purpose:
• Validate the measurement methodology
• Familiarize with the OpenWSN implementation
• Obtaining an approximate energy consumption
Test 1
• Default OpenWSN implementation + UDP traffic
• Purpose
• Defining an UDP application to have data messages on the network
Test 2
• Tree topology +Specific schedule + UDP application
• Purpose:
• Forcing a specific topology
• Implementing an optimal schedule
Test 3
• Tree topology +Specific schedule + UDP application
• Purpose:
• Implementing a realistic scenario
• Schedule generated with optimizing communication paths tool
• Obtaining a new estimation of the energy consumption
Test 4

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Test
1
Topology
Routing tree Traffic Specifications
• No data messages
• Only RPL messages
• Communications over one
frequency
Schedule
• 11 slots in the frameslot
• 15 ms each slot
• 1 advertisment slot
• 5 shared slots
Measurement Observations
• Battery life of the acquisition
mote < 1 month

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Traffic Specifications
•No data messages
•Only RPL messages
•Communications over one frequency

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Test
1
Topology

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Test
4
Topology
Routing tree Traffic Specifications
UDP Application
• Each mote sends an UDP packet
to the sink, each 10 s.
• Two frequency channels.
Schedule
Observations

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Test
4
Topology

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Time management
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 State of the art.
 Theoretical study of consumption.
 Definition of tests.
 Modification of the code for
• Forcing topology:
─ Poisoning of neighbor tables
─ Forcing Rank of motes
• Hardcoding schedules in motes.
• Implementation of UDP applications.
• A lot of debugging time.
 Measurements.
 Analysis
 Problems faced:
• Study the whole implementation of OPENWSN firmware.
• Rolling release problems.
Total time: 280hs

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Conclusion
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 Project purpose: analyze 6TiSCH architecture energywise, based on OpenWSN’s
implementation.
 Radio activity: main consumer in our scenarios.
 Schedule implementation: significant impact on mote’s battery life.
 Schedule optimization:
• can be adjusted to long and sparsed frameslots
• mote will get to sleep more and have less radio activity.
 Schedule size: trade off between throughput, latency and power consumption.
 No PCE entity: need of managing slots manually, to optimize the schedule for each
application in particular.

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Conclusion and future work
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 In the following stages of this project we intended to experiment
more with the parameters
• Frameslot size
• Slot duration
• Structure of schedules
• Larger scale topology
• Different traffic load
 Guarantee life battery expectancy of one year (in the lower levels of
the RPL DODAG).
 Due to the lack of time, bugs and other problems encountered we
couldn’t achieve this last stage, but we are certain of its feasibility.

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Thank you for your attention !
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The protocol stack
Source: T.Watteyne, X.Vilajosana : OpenWSN: A standards-Based Low-Power Wireless Devepment Environment

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Star topology
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Mesh topology
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First measurements
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-Frame slot -FSM
-Radio on -Energy consumption
5ms

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Theoretical consumption of the mote
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Source: Datasheet: Mote iv Telos (Ultra low power IEEE 802.15.4 compliant wireless sensor module Revision B :
Humidity, Light, and Temperature sensors with USB)
Typical Operating Conditions nom max unit
Current Consumption: MCU on, Radio RX 21,8 23 mA
Current Consumption: MCU on, Radio TX 19,5 21 mA
Current Consumption: MCU on, Radio off 1800 2400 uA
Current Consumption: MCU idle, Radio off 54,5 1200 uA
Current Consumption: MCU standby 5,1 21 uA

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The time chart of a simple Tx/Rx Scenario
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Source: https://openwsn.atlassian.net/wiki/display/OW/IEEE802.15.4e