## 3 Materials and Methods
### Blackbox Devices' Concept and Development
Figure 5: Multi-sensor data acquisition, synchronization, and structured transmission workflow in the Monit4 Healthy system. Communication Protocols and Optimization Strategies  
Efficient data exchange is crucial for real-time health monitoring systems. Wi-Fi and Bluetooth serve as the primary communication protocols for data transmission in IoT-enabled medical devices. Wi-Fi provides high-speed, long-range connectivity, enabling continuous data synchronization with cloud storage. The Bluetooth module ensures real-time data transmission by establishing a seamless wireless connection, which is vital for telemetry and remote monitoring applications. * _Bluetooth Module for Real-Time Data Transmission:_ The Bluetooth module facilitates real-time data transmission, ensuring reliable connectivity. This feature is essential for applications requiring continuous data flow, such as telemetry and remote patient monitoring. Advanced BLE technology ensures low power consumption and reduced latency, making it suitable for wearable health applications. It employs adaptive frequency hopping (AFH) to minimize interference and optimize bandwidth utilization. BLE and Wi-Fi are widely adopted wireless communication technologies for data transmission, each optimized for different application scenarios. BLE is designed for low-power, short-range communication, making it ideal for battery-operated devices such as wearable sensors and IoT nodes. In contrast, Wi-Fi provides higher data throughput and extended coverage, supporting applications that require continuous, high-bandwidth connectivity. Compared to other protocols such as Zigbee and LoRaWan, BLE offers higher data rates but at the cost of a reduced range, while Wi-Fi consumes significantly more power but ensures robust data transmission over greater distances. Although this work does not explicitly analyze the trade-offs in terms of power efficiency, range, and data throughput, it focuses on leveraging both BLE and Wi-Fi to optimize data transmission for specific use cases. BLE has significantly advanced from BLE4 to BLE5, delivering notable enhancements in communication reliability, the data transfer rate, and network scalability--essential elements for contemporary IoT and sensor network applications. Both BLE4 and BLE5 are designed primarily for low-power use--an important feature for battery-powered IoT devices and sensor networks. BLE4, launched with Bluetooth 4.0, utilizes a frequency-hopping spread spectrum technique within the 2.4 GHz ISM band to reach data rates of up to 1 Mbps, featuring a design tailored for energy efficiency and low-power functionality via simplified connection and advertising protocols. Conversely, BLE5 brings substantial improvements, including the adoption of a coded physical layer that boosts range and reliability in environments with high interference, along with a doubling of the nominal data rate to 2 Mbps. BLE5 increases the advertising capability by allowing larger payloads, which enhances detailed device discovery and connectionless communications. These technological advancements not only boost overall network efficiency but also allow for the incorporation of diverse sensors--like GPS units, EMG devices, and environmental sensors such as the DS18B20 and MAX30100--into more intricate and resilient monitoring frameworks. Both BLE and Wi-Fi are prone to interference in high-density environments. This is due to the shared spectrum in the 2.4 GHz ISM band, as well as due to the overlapping channels. To avoid congested channels, BLE utilizes adaptive frequency hopping (AFH). However, AFH's effectiveness may diminish in dense environments, therefore leading to packet loss and reduced reliability. Wi-Fi networks experience co-channel interference when multiple access points operate on the same or adjacent channels, leading to slower data rates and increased latency, particularly in areas with many overlapping access points [59].