## 4 Wireless Communication Technologies for IoT-Enabled Data Transmission
### Low Power Wide Area Networks  
An emerging communication technology for use in an IoT context are low power wide area networks (LPWAN). LPWAN technologies provide low cost, low power, low data rate, large coverage and long distance data transmission connections [81; 91]. Technologies that are often used are for example LoRa and narrowband (NB)-IoT. A detailed comparison study is provided by [PERSON] et al. [80]. An important aspect is that LoRa uses an unlicensed frequency band, and NB-IoT uses a licensed one. This results in a guaranteed Quality of Service for NB-IoT because no duty cycle limits hinder the data throughput [80; 90]. Key advantages of LoRa are its lower costs for connecting end devices and no operating costs for data transmission [80; 91]. Additional smaller differences in for example the maximum number of end devices, payload length and latency might be important to consider when choosing the right technology for a certain application. For real-time parameter monitoring in fresh fruit and vegetable supply chains, the coverage in suburban and rural areas can be a critical factor. Although LoRa and NB-IoT are expected to further expand their coverage, this aspect is important especially for internationally operating supply chains. All communication technologies presented in this section have their specific strengths and weaknesses. Generally, the biggest differences are in the range of data transmission, the data rate, the power consumption, the standardization, the costs and the availability of guaranteed Quality of Service. It is important to distinguish between technologies that use licensed and unlicensed frequency bands for data transmission, because this has direct influence on the costs and possible interference problems. Wireless communication is a crucial part of IoT applications and therefore technologies will further develop (e.g., transformation to 6G) and new technologies will emerge. Unfortunately, interoperability is limited and establishing corresponding standards remains a challenge [83; 91]. Additionally, various privacy concerns hinder actors from adopting these technologies on a large scale [3; 92; 78; 93]. Regarding IoT-based ambient parameter monitoring in fresh fruit and vegetable supply chains, there are many approaches to overcome disadvantages of certain communication technologies by combining two or more of them. Only some of the studies proposing an IoT-based monitoring system also apply it in practice. [PERSON] et al. [12] proposed a temperature and RH tracking system that combines RFID, Zigbee and cellular communication technologies, but did not test it in a real supply chain. [PERSON] and [PERSON] [93] described a similar approach using RFID and cellular networks for transmission of temperature, RH, carbon dioxide concentration and light intensity data in a blackberry supply chain. However, no validation was carried out in a real environment. [PERSON] et al. [94] developed a system using NFC connection to a smartphone for monitoring temperature and RH during transport, but also no testing scenario was described. An example of an application in a real supply chain provided by [PERSON] et al. [13] used RFID tags and a wireless sensor network based on Zigbee to monitor temperature and RH in commercial fruit storage warehouses. Data transmission was possible even across isolating doors [13]. More than 98% of the data packages were transmitted successfully, but they concluded that the large amount of RFID tags used was only practical in a testing scenario [13]. A study by [PERSON] et al. [95] investigated the application of a Zigbee-based monitoring system inside a truck. It was observed that some sensor motes were not able to transmit any data due to absorption of the signal, depending on their position inside the truck. Regarding temperature measurements, they found that, on average, the temperature was outside the recommended level for 98% of the time [95]. Another application can be found in [PERSON] et al.