## 3 IoT Standards and Protocols for Precision Agriculture
### IoT Protocols in Precision Agriculture (RQ2)
#### 3.2.2 Non-IP Protocols  
An Internet connection that requires minimal resource expenditure is a critical issue for low-power embedded devices used within sensors. Conventional wireless communication technologies are inadequate when considering coverage, energy consumption, and cost. Low Power Wide Area Networks (LPWANs) aim to address these issues, making them scalable and adaptable for large-scale deployments of low-power devices [67]. LPWANs are expected to operate at low data transmission rates to cover distances of several kilometres in both densely populated urban areas and suburban regions. Technologies such as LoRaWAN and SigFox, as examples of sub-GHz communication technologies, successfully provide these functionalities. LPWANs have several common characteristics that distinguish them from traditional communication networks: (i) low power consumption, as the network of end nodes should consume minimal energy; (ii) reduced communication costs; (iii) integration of geolocation capabilities; and (iv) robust modulation to prevent radio networks from becoming congested in high-density urban areas [68].  
SigFox  
SigFox is a proprietary communication protocol designed for IoT wireless networks, requiring a paid license managed nationally. It belongs to the LPWAN family of technologies [69] and is used for low-volume data transmission (from a few bytes to hundreds of kilobytes), with excellent range (tens of kilometres) and low current consumption (in the mA range per transmission). SigFox uses D-BPSK (Differential Binary Phase-Shift Keying) modulation, with a fixed bandwidth of 100 Hz and transmission rates of 100 bps in Europe or 600 bps in the USA, within an unlicensed spectrum below 1 GHz (868 MHz for Europe, 915 MHz for the USA) [70]. The benefits of D-BPSK include efficient spectrum usage and simple implementation, along with the ability to use low-cost components due to the low bit rate. The gateway receiver is highly sensitive, able to demodulate signals close to the noise threshold without any coding layer.  
LoRaWAN  
LoRa (long range) is a low-power Wide Area Network (WAN) technology owned by the \"LoRa Alliance\". It operates in the unlicensed spectrum across multiple bands ranging from 169 to 430 MHz, with 868 MHz (Europe) and 915 MHz (North America) being the most common. Its range extends up to 10 km in open areas and closer to 1 km in densely populated spaces like cities [71]. The bandwidth can reach up to 50 Kbps, depending on the distance and transmission power [15; 72]. The network is effectively half-duplex, meaning it supports bidirectional communication, but only in one direction at a time. Consequently, senders and receivers must coordinate to switch directions. The LoRa specification consists of PHY and MAC layers that can support applications with raw data. It defines three types of nodes: class A (Bidirectional End Devices), class B (Bidirectional End Devices with Scheduled Reception Slots), and class C (Bidirectional End Devices with Maximum Reception Slots). Finally, LoRa employs spread spectrum modulation and an Adaptive Data Rate (ADR) algorithm, enabling the data rates on each link to adjust according to signal strength and radio power [10]. The data rate can vary between 0.3 and 27 Kbps.  
Table 6 compares WiFi and Bluetooth with the most widely used LPWAN technologies in the modern market. In the field of precision agriculture, the most prevalent technologies are LoRaWAN and SigFox, two proprietary protocols designed for IoT devices that manage to reconcile coverage over distances on the order of kilometers with low energy consumption.