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LoRaWare: A service oriented architecture for interconnecting LoRa devices with the Cloud

Tsakos Konstantinos

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Summary

In this work, we show how the advantages of a Low Power Wide Area Network (LPWAN) protocol can be exploited to support greater availability and usability of Internet of Things (IoT) applications. The main idea is to show how LPWAN networks can be interconnected with the Cloud where IoT data can be transferred securely for persistent storage and further processing. To show proof of concept, we experimented with LoRa technology and LoRaWAN, the latest successful representative of LPWAN protocols. The LoRaWAN protocol is characterized by long range, low power and low data rate transmission. We applied a typical experimental setup with LoRa environmental sensors transmitting measurements over long distances using LoRa protocol to gateways and from there to the cloud. Our scenario is application agnostic (as it is independent of sensor types and need not be aware of the actual IoT measurements). The advantage of this scenario is that whole cities can be covered with a small number of gateways where, each gateway is capable of dealing with even thousands of sensors.The LoRa Nodes transmit RF packets with LoRa modulation which are captured by one or more Gateways. The Gateway receives LoRa packets from sensors in range and re-transmits them to the cloud over internet using an IP protocol (e.g. a basic one such as UDP). In this work we opt for MQTT a more elaborate lightweight publish-subscribe IP protocol offering advance security, better routing control and visibility of the communication (i.e. easier handling and control of data packets).The focus of this work is on interconnecting the gateways with the cloud. We develop the Network Server, a solution that runs as a service on the cloud and whose purpose is to (a) receive LoRa packets from gateways (b) decode their payload from ASCII characters to bits (base 64 encoding) (c) dedublicate packets received from more than one gateways (d) decrypt the payload (AES 128 bit encryptions is applied by LoRA) and (e) make data available to the cloud services in NGSI - JSON format. For outgoing packets the same solution is applied in reverse order: packets are encrypted, encoded and transmitted to target gateways (is supported by the LoRaWare with some additional configurations-haven’t been tested). The service is developed for FIWARE cloud, a pan-European cloud infrastructure which is supported by the EU. NGSI is the protocol which is used by every Generic Enabler of Fiware ecosystem as a data exchange model. One of them is the Publish/Subscribe Context Broker which mediates between devices and applications. Our architecture ,referred to as LoRaWare, allows IoT developers to enhance the capabilities of LoRa enabled applications using advanced FIWARE services supporting persistent storage and data analytics, service synthesis using Mashups etc. In our example implementation, humidity and temperature measurements are monitored in real - time on the cloud while historical values are stored in MySQL database.We run an exhaustive set of experiments using real and simulated (but realistic) data in order to study the system response time and system scalability.We report average end-to-end processing times (i.e. from the moment IoT data are received by the network server to the time they are stored in the database) and also average time spent on each service in the processing sequence.To study system scalability we stressed the system with a large synthetic (but realistic) payload simulating up to 2.000 requests (i.e. data packets) received by the Network server and processed on the cloud. Our experimental results demonstrate that our system is still capable of performing real - time or close to real time for many thousands of concurrent requests.In a different experiment, we study the practical range of LoRa transmission in a real urban environment (in the city of Chania) with two gateways placed apart from each other. The experimental results reveal that the rate of packages captured by any of the two gateways decreases drastically with the distance from the sensors in all cases.

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