In this dissertation we try to analyse simultaneous operation of multiple LoRa things in real electromagnetic environment.
LoRaWAN networks are presumably easy to set up and need be easily upgradable. Main element which enables us to upgrade this kind of network is gateway. Furthermore, communication with LoRa technology should be very reliable due to good interference resistance – receiving messages should be possible even in conditions when SNR is negative.
LoRa technology shows potential to be used for wireless reporting of operating status of solar panels used in solar power stations. Before one starts to design a real world system for commercial use, especially with technology that is not yet widely used and generally known, the theoretical capabilities should be tested.
For testing purposes of LoRa technology and LoRaWAN network we made 19 things. Initially, we focused on testing the simultaneous operation of things using non-orthogonal LoRa signals in the same frequency channel. These signals are, by some standards, unauthorized, but because of irresponsible individuals, they can still occur in the frequency domain and cause major network disruption. We have found that when such signals operate at the same time, there is a serious disruption to the network, which results in an inability to receive messages or a malfunction of received messages. In one case, the disruption was so severe that we received only 6 messages out of 100 messages sent and none of them were error free.
The following tests were aimed at testing the simultaneous operation of orthogonal LoRa signals in the same frequency channel. We were particularly interested in the simultaneous operation of a multiple number of things. In all tests there was communication between two things, and other things were used as disturbances. We tested simultaneous operation of things with a smaller number - 8 things, and a larger number - 19 things. All things emitted LoRa signals. In addition to these two examples, we tested the simultaneous operation of 11 things, of which 8 things emitted LoRa signals and 3 things FSK signals. Even with orthogonal signal combinations, message failures occurred but were drastically lower than with non-orthogonal signal combinations. In the case of orthogonal signals, in some measurements we had a partial or complete failure of all received messages, while the maximum failure of the orthogonal signal messages was 4,34%. When testing the simultaneous operation of orthogonal signals with the addition of FSK signals, the results were comparable to the other two tests.
As part of the master's thesis, we wanted to test the operation of our LoRaWAN network. We would keep increasing the network load until reliability of communication would start failing. We were unable to perform the test as it turned out that the gateway we had could not receive two or more signals at once. We assume that the reason for this is not in the LoRa concentrator, but somewhere in the software.
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