## 4 Communication Technologies for Seamless Connectivity in Smart Farming
### Network Functionality and Connectivity Requirements  
For large farms, high bandwidth is necessary because of large amount of data processing, such as large amount of precision farming data and telemetric data to be collected in the farm servers and download/update operations of the geographic maps. In case of greenhouses and horticulture lands, a totally different scenario must be analysed. Greenhouses are connected to the electrical grid [9], which has the requirement of using gateways. These gateways are very power consuming, hence batteries cannot be used as the power source. Therefore, cellular technologies such as LTE, 4G and 5G connections can substitute fixed lines, whereas WiFi can be considered for Internet connection. Similarly, a gateway between the WSN and the infrastructure can be available, so that small agricultural nodes can exchange data. On contrary, Livestock farming may have two different scenarios: one of for shaded animals and another is for free animals pasture in the fields. The former one is very similar to greenhouse, where wireless sensors are worn by the animals. Whereas, the latter one is an expensive option, where the data from animal sensors needs to be collected since the animals are scattered around the field. These information sometime rely on UAVs, drones or agricultural machines. Ensuring a safe travel of agricultural machines in public roads is another issue that needs to be addressed. The solution is to provide a Machine to Machine (M2M) communication notifying the presence of slow machines, where Intelligent Transportation Systems (ITS) standards [55] need to be included. The protocols for both Internet infrastructured connectivity and long range communications are cellular technologies such as 3G, 4G, 5G and LPWAN air interfaces which enable IoT data management paradigms.  
For agricultural UAVs, the Micro Air Vehicle Link (MAVLink) is a common communication protocol allowing UAVs to communicate with Ground Control Station (GCS). It communicates between computing platform (such as Raspberry Pi, Arduino, and UDOO), control platform (such as Pixhawk and Ardupilot) of UAV and application (such as mission planner and Qground control) of GCS [56]. MAVLink transmits directions, position of global navigation satellite system (GNSS) and speeds of the UAV. The communication distance between the UAV and the GCS depends on specifications of the UAV, However, it can communicate up to 2 km when the UAV is within LOS [6]. Currently, UAVs are programmed to operate at return-to-launch mode, which means the UAVs will automatically return to its first position when communication is interrupted. This mode is activated to prevent unwanted accidents or lost of UAVs [6; 57; 58]. Few other types of communication systems are also available for communicating between GCS and UAVs such as ZigBee, radio-frequency modules, and other transmitting medias. The communication distance can be increased with the addition of technologies, including phone apps. Moreover, the emergence of 5G cellular technology promises to greatly improve communications and data-processing speeds, which will be useful for high-definition mapping [59; 60].