Web-of-Things gateways offering REST interfaces for communicating with KNX and EnOcean building networks.

1. Institut Mines-Télécom
Offering Web-of-
Things Connectivity to
Building Networks
Gérôme Bovet1, 2 – Jean Hennebert2, 3
1Telecom ParisTech France
2University of Applied Sciences Western Switzerland
3University of Fribourg Switzerland
gerome.bovet@hefr.ch

2. Institut Mines-Télécom
Introduction – General context
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3. Institut Mines-Télécom
Introduction - Problematic
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 Simple encapsulation of telegrams in IP packets
 No standard application protocol !
• Implementation of each network in the BMS
• Huge integration costs
• High maintenance effort

4. Institut Mines-Télécom
Our goals
 Facilitate integration of various network types
into BMS
• Lower integration time
• Lower maintenance costs
• Make it usable for most people
• Special emphasis on existing installations
 Give BMS developers keys for quickly building
proactive and reactive BMS
• Interaction over REST APIs
• Offering a notification mechanism (reactive BMS)
• Offering storage capability (proactive BMS)
• Simple identification of devices
 Work on small and cheap hardware platforms
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5. Institut Mines-Télécom
The Web-of-Things and home automation
 OpenHAB and freedomotic
• More a BMS than a simple gateway
• Heavy integration time for new and existing KNX
installations
• KNX expertise required
• Development skills required
• No EnOcean support yet (under development)
• No notification mechanism (freedomotic)
 sMAP
• No KNX and EnOcean support
 No existing solution satisfying our needs 
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6. Institut Mines-Télécom
IP Gateway
WoT GatewayBMS
DNS
EnOcean USB
The gateway approach - Principle
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1
3
2
4
5
1. Client calls http://motion.kitchen.home/pirs
2. DNS server answers with IP of WoT gateway
3. Client performs the HTTP request
4. WoT gateway maps URL to KNX group or EnOcean profile
5. Command sent to KNX or EnOcean network
5

7. Institut Mines-Télécom
The gateway approach - Benefits
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 Hiding the KNX/EnOcean complexity
 Simple to use
 Open & based on Web standards
 Solving the heterogeneity problem

8. Institut Mines-Télécom
http://<GROUP NAME>.<LOCATION>.<ORGANIZATION DOMAIN>/<DATAPOINT>
http://heating.office005.ground.leso.epfl.ch/dpt_switch
Mapping KNX to REST APIs
 How to map KNX datapoints to RESTful services ?
• Active discovery of devices and datapoints too complex 
• Most installations are configured with ETS 
 Using the knowledge stored in ETS
• Compressed file
• Not protected
• XML representation of
─ Building structure
─ Devices
─ Datapoints
 Mapping rule
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9. Institut Mines-Télécom
Mapping EnOcean to REST APIs
 How to map EnOcean profiles to RESTful services ?
• Active discovery of devices not feasible 
• No software for configuration - no central knowledge 
 Web application for configuration
• Discovering devices configured in learn mode
• Handling location information
 Mapping rule
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http://<GROUP NAME>.<LOCATION>.<ORGANIZATION DOMAIN>/<PROFILE>
http://temperature.05.00.c.eia-fr.ch/tmp

10. Institut Mines-Télécom
Gateway API - Discovery
 Building discovery
• http://<LOCATION>.<ORGANIZATION DOMAIN>
• http://ground.leso.epfl.ch
• {”name”:”office005”,
“isGroup”:false,
“url”:http://office005.ground.leso.epfl.ch}
 Datapoint/profile discovery
• http://<LOCATION>.<ORGANIZATION DOMAIN>/*
• http://office005.ground.leso.epfl.ch/*
• {"datapoint_info":"1-bit”,
"datapoint_type":"DPT_Switch”,
"description":"on/off”,
"bits_size":1,
"datapoint_number":"1.001”,
"url":"http://heating.office005.ground.leso.epfl.ch/dpt_switch"}
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11. Institut Mines-Télécom
Gateway API - Events
 Events (reactive BMS)
• Registration (HTTP POST)
─ http://<GROUP NAME>.<LOCATION>.<ORGANIZATION DOMAIN>/<DATAPOINT>/register
• Unregistration (HTTP POST)
─ http://<GROUP NAME>.<LOCATION>.<ORGANIZATION DOMAIN>/<DATAPOINT>/unregister
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12. Institut Mines-Télécom
Gateway API - Storage
 Storage (proactive BMS)
• Announcement (HTTP PUT)
─ http://<GROUP NAME>.<LOCATION>.<ORGANIZATION DOMAIN>/<DATAPOINT>/storage/add
─ Payload contains the number of days data should be stored
• Suppression (HTTP DELETE)
─ http://<GROUP NAME>.<LOCATION>.<ORGANIZATION DOMAIN>/<DATAPOINT>/storage/remove
─ Gateway shrinks data
• Retrieval (HTTP GET)
─ http://<GROUP NAME>.<LOCATION>.<ORGANIZATION DOMAIN>/<DATAPOINT>/storage?days=X
─ http://<GROUP NAME>.<LOCATION>.<ORGANIZATION DOMAIN>/<DATAPOINT>/storage?from=X&to=Y
─ {
"storage": [
{ "value":"on", "timestamp":"2013-01-10 08:12:34" },
{ "value":"off", "timestamp":"2013-01-10 09:05:57" },
{ "value":"on", "timestamp":"2013-01-10 13:40:03" },
{ "value":"off", "timestamp":"2013-01-10 17:33:11" }
]
}
• Reducing the need for storage
• Only interesting data are stored
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13. Institut Mines-Télécom
Implementation - Technologies
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14. Institut Mines-Télécom
Implementation - Architecture
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15. Institut Mines-Télécom
Evaluation – KNX Performance
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 Realized on the LESO building of the EPFL, CH
• 265 devices - 795 groups
Measure type KNX WoT openHAB freedomotic
Installation and
integration time
25 [min] >230 [min] -
Maximum HTTP
requests per second
45 21 -
Maximum simultaneous
HTTP requests
620 580 -
Average event reaction
time
33 [ms] 51 [ms] -

16. Institut Mines-Télécom
Evaluation – EnOcean Performance
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 Realized at the EIA-FR, CH
• 14 devices – standard office equipment
Measure type EnOcean WoT
Installation and integration time 13 [min]
Maximum HTTP requests per second 82
Maximum simultaneous HTTP
requests
630
Average event reaction time 29 [ms]

17. Institut Mines-Télécom
Evaluation – User experiences
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 Limitation of the DNS approach
• Security issues – write access to main DNS not
allowed
• Need for a dedicated server
 No security
• Authentication
• Encryption
 Positive feedback from developers
• Short integration time
• Open technologies

18. Institut Mines-Télécom
Conclusion and future works
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 Conclusion
• WoT approach is suited for BMS
─ Simplicity
─ Open standards
─ Naturally fits with sensor networks
• Fast integration of the gateway in existing installations
• Raspberry Pi is an alternative to classical PCs
 Future works
• Adding a security layer
• Merging KNX datapoints and EnOcean profiles
• Distribution of rules generated by proactive BMS

19. Institut Mines-Télécom
Questions
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