## 2 Methodology
### Experimental Approach  
According to Figure 1, the units TxU and RxU are linked through a wireless channel. On both sides, a computer is connected to a microcontroller (Arduino Uno), which in turn interfaces with an RF module (NRF24L01). These RF modules operate at 2.4 GHz and are equipped with both a low-noise amplifier and a power amplifier to enhance their transmission and reception capabilities. This RF module employs the SPI (Serial Peripheral Interface) for communication between the module and the microcontroller. Thus, the NRF24L01 implements its proprietary wireless communication protocol, operating in the 2.4 GHz ISM band. The latter includes features such as addressing, error control, and the  
Figure 1: Proposed experimental setup used to evaluate the IoT communication system’s performance by using custom-designed antennas.  
Figure 2: Antennas under test. (**a**) Modified shape-optimized Landstorfer Yagi-Uda antenna (LaYUA). (**b**) Printed turnstile antenna (TuSA) with 90\({}^{\circ}\)-phase-shift feeding between U\({}_{1}\) and U\({}_{2}\) sources, realized with a coaxial line.  
capability to handle multiple channels and addresses, enabling, in this way, robust wireless data transmission and reception [14].  
In order to ensure the relevance of the measurements and minimize interference, the TxU and RxU were strategically placed at distances varying from 10 m to 100 m in an open-field environment, specifically chosen to reduce obstructions and minimize external interference from buildings, vegetation, or other sources of signal reflection and attenuation. The tests were conducted under clear weather conditions, with environmental factors of a 18.7 \({}^{\circ}\)C temperature and 65.8% humidity. Additionally, a key feature taken into account in this experiment is the tilt angle of the linear polarized antennas (LaYUA and commercial dipole) to achieve polarization matching. This adjustment is essential for accurately evaluating the system's performance metrics. The system is tested under a transmit power level of 0 dBm and a data rate of 2 Mbps to evaluate the bit error rate (BER) characteristic across different scenarios, including urban fading profiles, which will be discussed in the following sections. A low BER implies high-quality communication, which is essential for reliability in IoT applications. Furthermore, it is critical for assessing system efficiency, as a high error rate requires retransmissions, thereby increasing latency and energy consumption in battery-dependent IoT devices.  
A key component of this setup is the use of different antenna structures for the evaluation. Four different scenarios are examined to analyze the impact of these configurations on wireless communication performance:  
\begin{tabular}{l l} Scenario 1 & Commercial dipole antennas: This is the baseline scenario. Both the TxU and RxU are attached with standard commercial dipole antennas. \\ Scenario 2 & LaYUA and commercial dipole: This scenario includes the LaYUA, attached to the TxU, and the commercial dipole antenna, attached to the RxU. \\ Scenario 3 & Commercial dipole and TuSA: This scenario utilizes the commercial dipole antenna, attached to the TxU, and the TuSA, attached to the RxU. \\ Scenario 4 & LaYUA and TuSA: This scenario uses the LaYUA, attached to the TxU, and the TuSA, attached to the RxU. \\ \end{tabular}