## 4 LoRa Traffic Generator Development and Validation  
In this section, an experimental analysis has been made using SDR technologies, measurements being realized in a semi-anechoic chamber (in an interference-free environment). while considering the previously presented results. The first step has been the development, implementation and testing of a LoRa packet generator capable of generating packets that are compatible with the LoRaWAN specifications which have been defined by LoRa Alliance. For the implementation of the generator, the SDR technology is integrated by means of a LimeSDR [31] hardware equipment. Figure 8 depicts the developed communication mechanism. This advantage can be achieved by integrating two or more SDR platforms, each equipped with two transceivers in a topology that is of a MIMO (Multiple Input Multiple Output) type. Thus, there is a possibility of generating a large LoRa traffic volume with an increase in performance level. The advantages of this implementation are represent ted by the fact that the user does have access to the mechanism tasked with generating the packet, such as payload or elements that are tied to the ways of coding and creating packets. These features represent the novelty of this work. To validate the developed LoRa traffic generator, some test scenarios created by means of using a TDK RF Solution [32] manufactured semi-anechoic chamber has been implemented. This is because an isolated environment is required with no in-band interferences, especially when analyzing an unlicensed frequency band where the transmitted signal level is very low (below RF noise level). The used GW is implemented by using a Raspberry PI 3B+ and the iC880A concentrator board running a Linux-based operating system and integrating a forward-packet mechanism type towards the TTN data aggregation platform, connected to the Internet inside a semi-anechoic chamber. The designing and testing of the GW module are depicted in previous work published by the authors [33]. The GW structure used in the conducted experiments is presented in Figure 9.  
Figure 10 depicts the test setup implemented in the evaluation of the performance level of the LoRa traffic generator module so that the resistance to interferences that originate from the use of different SFs can be evaluated. The test makes use of a TDK HLP-3003C periodic log antenna. Figure 8: LoRa traffic generator by integrating Software Defined Radio (SDR) technology. The integrated communication mechanism can generate a high volume of data with the help of LoRa packet transmissions. Figure 10: Performance evaluation test setup. (**a**) presents the test setup configuration. (**b**) depicts the traffic generator that has been realized by using two SDRs of a LimeSDR type and the host PC, which runs the application. (**c**) presents the measurement equipment. Figure 9: LoRaWAN gateway. The gateway integrates a Raspberry PI 3B+ and the iC880A concentrator that allows the simultaneous communication on eight channels (as stated in the LoRaWAN specifications). In the experiments carried out, the LoRa sensors that have been used feature an Atmega328 micro-controller and an RFM95 [34] radio module from HopeRF. These sensors communicate with the GW module by means of different SFs, and as a communication channel, 868.3 MHz is used. For the conducted tests, the payload has been set to 12 bytes, due to considering this the average dimension of a LoRa packet [35]. In these experiments, a handful of test scenarios has been performed for the validation of the developed traffic generator. The main advantages are that the user has access in modifying parameters such as: Spreading factor, a packet payload, coding rate, the communication channel bandwidth and the communication channel central frequency.