## 3 LoRa Modulation Evaluation  
In this section, we focus our attention onto the RF (Radio Frequency) and MAC (Medium Access Control) layer particular to the LoRa technology. Current studies are mostly based on the results obtained through simulations [13; 14], and imply that the use of multiple transmission channels and spreading factors lead to a system that can be deemed as a superposition of independent sub-systems (featuring one channel, with one single SF) [15]. This is only a powerful simplification, especially when the SFs adopted by LoRa are quasi-orthogonal [16]; and as a consequence, in certain conditions, the collisions can prevent the correct reception of overlapped transmissions by using different SFs. In Reference [17] the power reception thresholds are quantified for various SF and the signal to interface ratio (SIR). Despite all these, there is a justification of the obtained results in the work mentioned before. Thus, the purpose of this work is to provide the readers with a series of clarifications and sets out to analyze the influence of collisions onto the performance level of a LoRa network and the orthogonality of LoRa communication [18]. In this work, the empirical results are justified by the obtained experimental results. The influence of collisions over performance is difficult to analyze in a classical setup, due to the fact that the integration of a large number of sensors demands a high cost. This is the reason we focus on the development, implementation and testing of a LoRa traffic generator that allows us to generate a large volume of data packets with the use of SDR technologies. This LoRa traffic generator must be easy to re-configure and flexible enough to allow for the customization of LoRa packets enabling testing in various configurations and structures. Because of these reasons, an SDR solution has been selected, meeting the requirements of flexibility, while being low cost at the same time. The traffic generator tests are performed within a semi-anechoic chamber in order to avoid any outside interference and obtain accurate results. The performance testing of the LoRa technology cannot be overlooked. The developers and those who implement networks which use the LoRa modulation need new solutions that can contribute to the direct increase in performance level meaning a detailed analysis of the influence the collision of packets, which can occur in LoRa communication architectures. These aspects can be considered the novelty of this work. In Reference [17], it is shown that the SIR threshold for the reception of a correct packet is almost independent of SF, with a channel rejection average of \(-16\)dB. The goal of introducing these separation systems (e.g., spreading factor and communication channel bandwidth) is within their possibility to integrate several nodes that are as high as possible capable of co-existing within the same cell provided by a gateway (GW) module. On these grounds, LoRa offers various possibilities for orthogonal transmissions, such as central channel frequency (f\({}_{c}\)) Spreading Factor (SF), communication channel bandwidth (BW) and Coding Rate (CR). Notwithstanding all this, despite the ruggedness of the LoRa technology, its scalability is still undergoing research with a collective effort aimed at achieving this goal [19]. This paper comes to fill this gap in scientific literature, contributing to the opening of new research directions in the field of LoRa network scalability. In a system that uses LoRa modulation, a collision is described as a moment in which two or more sensors simultaneously send data to each other by using the same spreading factor on the same channel. These collisions could lead to the loss of network packets through its action. Despite all this, thanks to its capture effect, the receiver can sometimes successfully decode one of the packets even when a collision may happen [20].