## 3 Multi-Hop IoT Systems for Patient Monitoring
### The Role of Microcontrollers  
Microcontrollers in multi-hop IoT systems are pivotal, serving as the backbone that orchestrates communication and coordination among devices within the network. In the context of multi-hop communication, microcontrollers act as intelligent nodes that facilitate the seamless exchange of information between devices, contributing to the efficiency and reliability of the overall system [37].  
At the heart of multi-hop IoT systems, microcontrollers manage the flow of data by coordinating communication between devices on different hops. These devices, equipped with microcontrollers, not only receive and process data locally but also make informed decisions on forwarding data to subsequent nodes in the network. This intelligence allows for dynamic and adaptive routing, optimizing the transmission path based on factors such as network conditions and energy efficiency.  
Microcontrollers play a crucial role in addressing the specific needs of health monitoring applications within multi-hop IoT systems. They enable the integration of various sensors and actuators, allowing collection of diverse health-related data and the execution of responsive actions. For instance, in a health monitoring scenario, a microcontroller on each hop can aggregate data from wearable sensors, process them locally to extract relevant information, and then transmit condensed and meaningful insights to the next node in the network [38].  
Furthermore, microcontrollers contribute to the energy efficiency of multi-hop IoT systems by implementing power management strategies. They can control the sleep-wake cycles of devices, optimizing energy consumption and extending the overall network's lifespan, which is particularly crucial in healthcare applications where continuous monitoring is essential [39].  
Several microcontrollers are commonly used in multi-hop IoT networks due to their features, power efficiency, and connectivity options. Some popular microcontrollers for working with multi-hop IoT networks include the following:  
* ESP8266: Known for its low cost and built-in wireless fidelity (Wi-Fi) capabilities, the ESP8266 is widely used for IoT systems.
* ESP32: An advanced version of the ESP8266, the ESP32 includes both Wi-Fi and Bluetooth connectivity, making it suitable for a broader range of applications.
* Arduino: While not specifically a microcontroller, the Arduino platform, especially boards like Arduino Uno and Arduino Nano, is frequently used for IoT prototyping due to its ease of use and extensive community support.
* Raspberry Pi: Although more of a single-board computer than a microcontroller, Raspberry Pi is often used in IoT projects for its processing power, connectivity options, and versatility.
* Nordic nRF52 series: These microcontrollers are known for their low power consumption and are commonly used in IoT devices like wearables and Bluetooth-enabled gadgets.  
In essence, the role of microcontrollers in multi-hop IoT systems is multifaceted, encompassing data management, intelligent routing, sensor integration, and energy optimization. Their capabilities are instrumental in creating resilient, adaptive, and energy-efficientnetworks, making them indispensable for the success of health monitoring applications and beyond.