Meshnetwork of wireless IoT sensors

University essay from Umeå universitet/Institutionen för fysik

Abstract: The Internet of things is a scenario where devices such as lighting, household appliances, sensors etc. are connected and communicate with each other via Internet. This puts a demand for a good infrastructure around these devices. One way to handle this is to use radio as a means of communication and let the devices forward each other's traffic in what is known as a mesh network. This thesis explores different radio standards that can be used to create a mesh network for sensors. Two different approaches to mesh networking using Bluetooth Low Energy was implemented and evaluated. One approach works by letting all devices broadcast every message they receive, a rather brute force approach. The other approach worked by letting the network find routes between all the nodes in the network and then establishes a connection between the nodes that want to communicate via intermediate nodes. It was found that the rebroadcast approach in idle mode used 3.36 mAh while the connection approach used 0.47 mAh for the same configuration. Another test was performed where the percentage of successfully delivered messages was measured. For the rebroadcast approach it was 75 % and for connection it was 58 %. Tweaking the connection network to not be able to adapt to changes increased the throughput to 77 %. During the testing numerous ways for improving performance were thought of but not implemented. The need for synchronizing the devices clocks and establishing protocol for when to send and receive became apparent when working with the rebroadcast network. In the connection network there were problems with that the routing maintenance led to unavailable units and reduced performance.

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