## 3 Methodology
### Hardware  
The developed system is based on two computers that are responsible for controlling and managing each module. One controls the SDR for the analysis of RF signals. At the same time, the other is responsible for the computer vision block from the images of the various cameras. A router is needed to connect the system components via Ethernet for communication. This allows communication between the computers through sockets and between cameras through IP addresses, ensuring all devices are on the same local network.  
Figure 1 shows all the devices that make up the system. On the left side is the detection module that uses the RF signals, consisting of the SDR and a PC inside an IP67 protection box located next to the cameras, and, on the right side of the figure, is the computer vision module. The router is the central element through which all devices are interconnected via IP addressing or being physically connected via Ethernet. Likewise, the router also has Internet access to communicate with the alarm-receiving center (ARC), which is located in the security company's facilities.  
Figure 1: Physical architecture of the system, where the colour of each arrow indicates the type of physical connection between the devices.  
The four fixed cameras are the Hikvision DS-2 CD2743G0-IZS model (Hikvision Digital Technology Co., Ltd., Hangzhou, China). In contrast, the PTZ camera is the Dahua PTZ1A225-HNR-XA (Zhejiang Dahua Technology Co., Ltd., Hangzhou, China), which is a camera with a 2 MP CMOS sensor capable of 360\({}^{\circ}\) horizontal rotation and 180\({}^{\circ}\) vertical tilt, featuring a 25\(\times\) optical zoom. Both camera models have a minimum IP66 rating, making them suitable for outdoor installation, and they support PoE+.  
The SDR used for receiving the RF signals is the bladeRF 2.0 micro xA4 (Nuand LLC, Rochester, NY, USA), which offers a frequency range from 47 MHz to 6 GHz and a sampling rate of 61.44 MHz, expandable up to 122.88 MHz, with 2 \(\times\) 2 MIMO. It has an integrated Analog Devices AD9361 transceiver (Analog Devices, Inc., Wilmington, MA, USA) and an Altera Cyclone V FPGA (Altera Corporation, ahora parte de Intel Corporation, San Jose, CA, USA), enabling real-time transmission and reception for advanced applications. It is physically connected to the computer via USB 3.0.  
The two computers used are from the NVIDIA Jetson family and are both powerful platforms specialized in AI development. The NVIDIA device responsible for the SDR module is the Jetson Nano Developer Kit (NVIDIA Corporation, Santa Clara, CA, USA), while the one for the cameras is the Jetson Orin Nano Developer Kit (NVIDIA Corporation, Santa Clara, CA, USA). The latter is considerably more powerful than the former, as the computational cost in computer vision applications is high, requiring a device capable of managing five cameras using YOLOv10.  
Finally, to perform IP addressing for the various components, a RG-EG105G-V2 (Ruijie Networks Co., Ltd., Fuzhou, China) router is used, connecting both computers and the network cable that provides Internet to communicate with the ARC over the network. Additionally, the PFS3218-16 GT-135 PoE (Zhejiang Dahua Technology Co., Ltd., Hangzhou, China) switch is used to connect all the cameras as they are all PoE.