## 5 Discussion
Most important characteristics include the data transmission range, the use of licensed or unlicensed spectrum, the power consumption, the costs and the standardization. Selecting the right combination of technologies is crucial for achieving added value with an IoT-based monitoring system. It is disadvantageous that there are currently no guidelines for supply chain actors who want to implement such a system on how to decide on appropriate technologies for their specific use. Additionally, other factors besides product-related ones influence the choices of whether and which sensor and communication technology should be used. Particularly supply chain- and process-related aspects are important: the mode of transport affects the type and number of process steps involved and consequently the ambient conditions the product is exposed to. Land transport is most used for fruit and vegetables with distances up to thousands of kilometers [39]. Maintaining optimal conditions, especially temperature, is difficult during such long transportation. Studies show that the temperature conditions can vary significantly within a truck and even within a pallet, depending, among others, on the age and design of the transport/storage unit or the packaging of the products [117; 118; 119; 3]. Same applies for air transport, which involves numerous handling steps that make the cold chain vulnerable to interruptions [39]. For products being exported to remote markets, sea transport in reef containers is a standard part of the supply chain [120]. Interruption of the cold chain can occur frequently during container handling at the port terminals [120]. Additionally, real-time parameter monitoring during sea transport can be difficult because overseas connectivity is often based on expensive satellite communication [6]. These aspects lead to the problem that process-related requirements of implementing IoT sensor technology need to be established newly for every specific supply chain. This includes, for example, requirements regarding the placement of sensors, the minimum number of sensors and the measurement frequency. The complexity of international, multi-actor supply chains of fresh fruit and vegetables poses further challenges. For highest benefits regarding quality retention and reduction of product losses, a monitoring system should not only cover part of the supply chain but should be implemented cross-chain. Until now, operators in the supply chain are often reluctant to share corresponding data along the chain due to various privacy concerns [3; 79; 92; 93]. However, information exchange is a basic requirement to successfully implement new quality-oriented concepts. Increased awareness among the actors regarding the (also monetary) advantages of a cross-chain monitoring system could improve this [39], as well as further information about the use of modern sensor and communication technology. It is important to understand which requirements different supply chain actors pose on an IoT-based monitoring system and the corresponding data platform, e.g., regarding data exchange, data storage, applications and interfaces. Even if actors are willing to share the information, simple data exchange along the chain is not always possible. Standards regarding data formats, data exchange and technical equipment are missing or mismatching [78; 91; 120; 121]. Providers have generally been more interested in selling their proprietary solution than in investing in open standards [91; 117]. Compatibility and integration of the multiple heterogenic devices and communication technologies are a big challenge for IoT-based systems [10]. This hinders efficient information exchange and data processing for quality and shelf life-related applications. The rise of blockchain-based solutions integrated into agri-food supply chains has potential to mitigate those aspects. Increased supply chain vulnerability and resulting security concerns of actors can be addressed by the possibility of immutable data exchange and privacy preservation [122; 123; 124].