# IoT Services for Monitoring Food Supply Chains
## 3 Methodology and Implementation
### Data Collection  
As we previously discussed, wireless sensors can be tailored to transmit data at specified intervals, enabling real-time monitoring that aligns perfectly with the unique requirements of the cold chain. This flexibility in data transmission frequency ensures precise and continuous oversight, enhancing the efficiency of the monitoring process. One of the defining features of these wireless sensors is their ability to transmit data only when necessary. Once the gateway in Figure 4 captures the data from the sensors, it employs high-bandwidth communication channels, such as Wi-Fi or cellular networks, to transfer the collected sensor data over the Internet Protocol (IP) to a cloud-based platform for further processing and analysis. Once the data is captured by the sensors, it is transmitted to a gateway device that serves as the intermediate communication hub between the field layer and the cloud infrastructure. In this implementation, we employed the GP Outdoor LoRa Gateway, an industrial-grade solution specifically designed for reliable long-range LoRaWAN communication in outdoor environments (Figure 4). The gateway is enclosed in an IP66-rated weatherproof casing and supports multiple backhaul options, including Ethernet, Wi-Fi, and cellular networks (GPRS/3G/4G), ensuring connectivity in diverse deployment scenarios. It features an ARM Cortex-A53 processor, 1 GB of RAM, and 32 GB of local SD storage, while operating at a total power consumption of 12 W.  
From a communication perspective, the gateway is equipped with one multi-SF LoRa channel, one single-SF LoRa channel, and one GFSK channel, supporting transmission power up to 20 dBm and reception sensitivity as low as \(-139\) dBm (SF12, BW = 125 kHz). These specifications enable long-distance and energy-efficient data transfer from the end nodes. Additionally, the gateway supports LoRaWAN Classes A, B, and C in half-duplex mode, and can accommodate up to 4000 nodes depending on the configured payload and data rate. This makes it highly suitable for dense sensor deployments and cold chain applications requiring stable, large-scale data acquisition. In the context of visualising the collected data, the REST API technique was used, which is a standardised and simple interface designed to facilitate interaction and data exchange over the web. This type of API allows developers to access a wide variety of digital resources, including datasets, content, algorithms, multimedia files, and other forms of information, all of which can be accessed through specific web URLs. Through the Bearer token required for authentication, it is possible to display all available sensors on the map, where a wealth of information is shown, including live temperature and humidity, the time the sensor is in operation, and the location of the specific sensor. However, the data provided by each sensor is extensive and can be used, depending on the application. In addition, when displayed in the following picture, data such as temperature can be visualised in a way that makes it as understandable as possible to any user. From an implementation perspective, an HTTP API is vital for efficiently collecting sensor data and facilitates remote control operations. By utilising this interface, users can easily gather and transmit data from various sensors, allowing for real-time monitoring and analysis. Additionally, the API enables remote control functionalities, empowering users to easily and precisely manage devices and systems from a distance. This capability is beneficial in various applications, ranging from home automation to industrial monitoring, where seamless communication and control are essential. The selected sensor locations, as shown in Figure 5, serve as representative nodes within the broader cold supply chain ecosystem. These points simulate critical stages of the food supply chain, including storage facilities, distribution endpoints, and fields. The real-time environmental data (temperature, humidity, battery status, etc.)