## 4 Integration of Biosensors
### Node Configuration
#### 4.2.4 Gateway Node Configuration  
* Data aggregation: Data aggregation in IoT networks involves gateway nodes strategically collecting and consolidating data from multiple sensor nodes to optimize network efficiency and resource utilization [88]. This process minimizes the amount of data transmitted, improving resource utilization and reducing congestion in scenarios with many sensor nodes [89]. Data aggregation contributes to energy efficiency by minimizing the need for frequent and energy-intensive transmissions directly from sensor nodes [90]. It also optimizes bandwidth usage by transmitting aggregated data sets, which is particularly beneficial in bandwidth-limited scenarios [91]. Aggregating data at gateway nodes allows for better control and validation, improving data integrity and minimizing errors during transmission [90]. In summary, data aggregation is crucial for efficiency, congestion reduction, energy optimization, bandwidth conservation, and data integrity in IoT networks, highlighting the strategic importance of gateway nodes in facilitating the seamless functioning of the IoT ecosystem.
* Connectivity: In IoT networks, gateways play a crucial role in ensuring robust connections to back-end servers or cloud platforms. Gateways utilize reliable protocols such as MQTT, CoAP, or HTTP/HTTPS and adapt to application-specific requirements [46]. It establishes connectivity using wired solutions such as Ethernet for stability and high bandwidth, or wireless technologies such as 4G/5G and Wi-Fi when wired connections are inconvenient [92]. Gateways may incorporate load balancing to efficiently distribute traffic and ensure optimal system performance. In the event of hardware failure or network disruption, redundancy measures such as dual interfaces or fail-over mechanisms increase reliability. With encrypted communication channels such as TLS and SSL, security is prioritized to protect data from unauthorized access [93]. The connectivity configuration is designed to be scalable to support the growing number of devices and increasing data loads, which is crucial for adapting to evolving requirements and expanding the IoT ecosystem [94]. In summary, the connectivity configuration of gateways includes protocol selection, wired or wireless solutions, load balancing, redundancy measures, security implementation, and scalability, all of which contribute to reliable and efficient connections between the IoT network and the back-end infrastructure.
* Data processing: In multi-hop IoT systems, gateway nodes play a very significant role beyond data collection, performing complex data processing tasks to improve system efficiency and responsiveness. The gateway acts as an intelligent hub where data are carefully pre-processed, starting with filtering to remove irrelevant information and optimize the payload for transmission [95]. In addition, gateway nodes employ compression techniques to minimize the size of data packets, addressing bandwidth constraints and reducing network congestion, thereby improving the speed of data transmission [84]. Gateway nodes also perform basic analytics tasks, extracting initial insights from collected data and providing valuable information for immediate decision making at the network edge [96]. By performing data processing at gateway nodes, the processing load on centralized servers is reduced, latency is reduced, response times are improved, and resource utilization is optimized. This approach is particularly beneficial for real-time decision-making scenarios, as local processing capabilities contribute to faster action without overloading central servers [97]. In summary, data processing at gateway nodes ensures streamlined data transmission, reduces network congestion, and improves responsiveness in dynamic, multi-hop IoT environments.