Investigation intra spreading factor interference in LoRa networks: A real-world experiments

In the era of Internet of Things (IoT), Low Power Wide Area Network (LoRaWAN) has presented itself as an efficient technology in this aspect due to its long-range, low-power communication capabilities. However, as the end users increased, the optimal deployment and configuration of LoRa become complex problem to solve where many factors governed its performance. One of the significant factors is the modulation of LoRa manifested by Spread Spectrum Frequency (SF). To give the network the property of scalability, the issue of interference between end users that using the same SF must be addressed and evaluated. In this research, intra SF interference is investigated through real world experiments considering different situation and factors that affect this type of interference. The experiments are conducted using three LoRa nodes, two transmitters (one as the victim r and the other acts like interferer) and one receiver node. The effect of interferer power, the frequency deviation and the transmitting time delay are varied to qualify intra SF interference. The network performance is evaluated in terms of Signal to Interference Ratio (SIR), Packet Delivery Ratio (PDR) and dropped packets. The significant findings from the three scenarios test bed analyses are; the SIR threshold should be sufficient to immune the packet from losses, when the interferer exceed the victim power 10 times, it gains 50% dropped packets and 87% correct PDR from the received packets. Scenario 2 shows that, keeping a sufficient transmitting time delay always contributes in reducing collision materialized by the dropped packets percentage. Finally, the third scenario results verify that, conserving orthogonality between the same SF can increase the network scalability.