The Internet-of-Things (IoT) vision states that sensors and actuators should be integrated into the internet to facilitate interactions with the physical environment. Novel Low Power Wide Area Network (LPWAN) technologies have arisen to facilitate the interconnection of many sensors at large scale providing low cost implementation and wide coverage. This paper analyzes and highlights from different perspectives the diverse LPWAN solutions available as open standards (3GPP's LTE-M, NB-IoT and EC-GSM-IOT) or as proprietary systems (LoRa, Sigfox and Ingenu). The paper also focuses on technologies that are involved at application level investigating their capabilities and their suitability in different portion of a large scale IoT system. We analyze CoAP, MQTT, AMQP, XMPP, DDS and OPC-UA among others. Finally, we briefly introduce some of the biggest testbeds in Europe (Santander and Padova) used to perform environmental monitoring within Smartcity projects. This paper is realized as a starting point for practitioners and researchers that are interested in understanding at 360 degrees how an IoT application can be deployed at a large scale.

1. Enabling Internet-of-Things
application on a large scale
Gabriele Di Bernardo
Vrije Universiteit Amsterdam
July 20, 2017

2. Internet-of-Things
• “If we had computers that knew everything there was to know
about things – using data they gathered without any help from us
– we would be able to track and count everything, and greatly
reduce waste, loss and cost. We would know when things needed
replacing, repairing or recalling, and whether they were fresh or
past their best.” - Kevin Ashton
• In 2008 the number of things connected to the internet was
greater than people living on planet Earth.
• 8 billion connected things will be in use worldwide in 2017 and will
reach 20.4 billion by 2020 according to Gartner Inc.
• The Boston Consulting Group predicts that by 2020, $267B
(€250B) will be spent on IoT technologies, products and services.
2

3. Research questions
• Which wireless technologies can be used to deploy
wide-area IoT applications and how they can be
categorised?
• Which application-layer protocols can be used in a
large-scale IoT system and how can they be used
within the system?
• What is the state-of-the-art of environmental
monitoring testbeds in Europe?
3

4. Wide-area IoT applications
common attributes
• Extended coverage
• Low energy consumption
• Low data rate
• Scalability
• Low deployment costs
4

5. LPWAN
5

6. LPWAN
• 3GPP
eMTC (LTE-M)
NB-IoT
EC-GSM-IoT
• Non-3GPP
LoRa
Sigfox
Ingenu
6

7. 3GPP standards for the Internet-of-Things

8. eMTC (LTE-M)
• Evolution of the LTE technology
• Low device cost (comparable to that of GPRS/GSM devices)
• Lower data rates DL/UL (up to 1Mbps)
• Reduced transmit power (multi-year battery life)
• 15 km coverage
• 20k+ devices per cell
• Deployment
• eMTC can be deployed in any LTE spectrum
• Coexists with other LTE services within the same bandwidth
• It reuses existing LTE base stations with software update
8

9. NB-IoT
• Designed for ultra-low-end IoT applications
• 180kHz of spectrum
• Lower device cost than eMTC
• Long battery life (10 years with 5 Watt Hour battery)
• Better coverage than eMTC (up to 35 km)
• Reduced data rate (~50Kbps DL/UL)
• Support for massive number of devices (50k+ devices per
cell)
9

10. Non-3GPP protocols for the Internet-of-Things

11. LoRa
• LoRa is a LPWAN physical layer patented by Semtech Corporation
• Chirp Spread Spectrum designed by Semtech in order to minimise power
consumption
• DL/UL data rate from 300bps up to 50kbps
• Battery life > 10 years
• Devices per Gateway
• UL 1M
• DL < 100k
• Coverage
• 2-5 km (Urban area)
• Up to 15 km (Rural area)
11

12. Sigfox
• Sigfox physical layer UNB with channel’s bandwidth lower than
1kHz
• UL 100bps
• DL 600bps
• Up to 1M connected objects per Basestation
• Limited number of messages transmitted per day according to the
subscribed plan
• Coverage area
• 30-50 km (Rural area)
• 3-10 km (Urban area)
12

13. 13

14. Application layer protocols for IoT
14
Inter Device communication
Device to cloud communication
Inter Data Center communication

15. CoAP
• CoAP allows constrained end-nodes to communicate in a
REST fashion over UDP
• Request/response paradigm; nodes in network are
abstracted as resources reachable through an URI
• Publish/subscribe paradigm possible through observe
option
• Different levels of QoS can be specified in the CoAP
header
• Good integration with HTTP
15

16. MQTT
• Publish/subscribe protocol on top of the TCP stack
• Nodes can register to the broker for specific topics
• Broker performs store-and-forward to route
messages from publisher to subscriber
• Different broker implementations are possible.
• No automatic discovery for topics/brokers
• QoS is an attribute of each individual message (i.e. fire
and forget, delivered at least once, delivered exactly
once)
• MQTT-SN for constrained devices
16

17. XMPP
• Open standard initially designed for chatting and message
exchanging on top of TCP stack
• Extensible through XMPP Extension Protocol (XEP)
• Support for discovery services mechanisms
• Support for publish-subscribe and request-response paradigm
• IoT adoption
• Direct deployment on resource-constrained devices
• Integrating smart objects with XMPP-enabled gateways
17

18. DDS
• Data-centric publish/subscribe communication
protocol on top of UDP standardised by OMG
• Decentralized broker-less architecture based on the
concept of global data space: no single point of failure
• Support for automatic topics discovery
• Very rich QoS (20+ different policies)
• DDS-XRCE for extremely resource constrained devices
18

19. 19

20. Environmental monitoring

21. Padova Smart City &
SmartSantander
• Network of wireless sensors (photometer, temperature
and humidity, benzene)
• Three-tier architecture
• CoAP over 802.15.4
• HTTP-CoAP Gateway
• ActiveMQ event broker
21

22. Conclusion
• Different LPWAN technologies in both the licensed and
unlicensed spectrum
• Each solution has pros/cons according to the IoT
application requirements
• LPWAN technology still in an early stage of adoption
• Different application layer protocols that can operate in
different scenarios (i.e. Inter and Intra Device
communication, Device to Cloud communication, Inter
Data Center communication)
• Different wide-area IoT application stacks are possible
22

23. Questions?