OMH-LoRa: An on-the-go Multi-hop Connectivity Enhancement for LoRa Nodes’ Access and Range
19 February 2020
Student name: Alnoman Abdulhudhur
Supervisor: Professor Ihsan Lami
On Friday 14 February, Alnoman presented his research project at the School of Computing Seminar Series, introducing OMH-LoRa, an on-the-go multi hop connectivity enhancement for LoRa nodes’ access and range, used for Internet of Things devices networking.
The increase of IoT equipment has caused a sharp increase in data and a loss of wireless traffic. This has caused signal interference and so a lot of these IoT devices are unable to reach the gateway. This project aims to enhance the connectivity of any node in the IoT network if it happens to be out of range of the gateway or an obstacle is present that prevents the node from reaching the gateway.
LoRa-WAN is a wireless connectivity gateway with STAR topology, this offers three different classes of operation.
An example of actual pest-trap LoRa deployment containing 100 nodes in around 3km² of built up area, shown that only 70% of nodes reaching the gateway. With interference, obstacles, range or hardware limitations playing a role with reducing the connectivity success rate.
A proposed solution to increase node efficiency would be to increase the number of small gateways, which will increases deployment costs. An alternative solution would be to have a node on listening mode, syncing with the gateway to signal its range and location, and will provide a 99-100% success rate with nodes relaying data between itself and the gateway more frequently, but reducing the battery life of the node dramatically.
This solution is created by merging class A and class C; switching between the classes for short time windows will allow for no wait time for gateway approval and the node can control itself, with the middle node focusing on class A and the end node switching to class C if no data is detected within range, listening to other nodes in range that might be able to bridge the connectivity to the gateway. When detected, the end node will send the message within the middle node’s second listening window, and so enabling the middle node to convey the message to the gateway and the acknowledgment back to the end node, before both nodes switching back to Class-A and going to sleep. With two nodes present to act as middle nodes, wait time for the end-node to send the message was reduced from 1.75 minutes to 1 minute but with the inclusion of a third/further nodes, the wait time stabilises and only reduces it to 0.48 minutes.
In conclusion, further study of the receive window and second application layer level is required to pinpoint the active time of the nodes. 100% success rate can also be achieved using this method by bypassing obstacles, interference and range issues.
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