## 4 Hardware Design  
The coverage of LPWAN technologies used in the tracking application mainly depends on the wireless channel characteristics (e.g., path loss, shadowing, and multipath propagation) and the hardware capabilities of VTUs that connect agricultural vehicles to the network. Before analyzing the coverage of LoRa and NB-IoT technologies for agricultural vehicle tracking, two different hardware designs were introduced to be used as a reference for concrete comparison. As can be seen from Figure 4, both of the VTU designs have been created on the same platform, but they were equipped with different RF transceivers depending on the wireless technology used for IoV connectivity.  
The designed VTU boards have been equipped with an STM32F407 VGT6 microcontroller, L70-R GPS module, and additional components to provide desired functionality. A Li-Po battery of 2000 mAh 3.7 V was also used to supply a stable voltage when external power was lost. STM32F407 VGT6 microcontroller is manufactured by STMicroelectronics, and it has a 32-bit ARM Cortex-M4 with an FPU core with 168 MHz frequency [39]. Qucetel L70-R GPS module has a compact design, low cost, and high precision with ultra-low  
Figure 3: LPWAN-based agricultural vehicle tracking with NB-IoT connectivity.  
power consumption in tracking mode. It has 66 acquisition channels, 22 tracking channels, and assisted GPS (A-GPS) support for indoor localization. L70-R communicates with the microcontroller using the UART interface [40].  
In the LoRa version of the VTU design, the Microchip RN2483 transceiver module was used to provide wireless networking capability. The RN2483 module contains a PIC18 LF46K22 microcontroller with Semtech's SX1276 transceiver. It can be operated in the 433 MHz and 868 MHz license-free frequency bands. LoRaWAN Class A protocol stack is embedded on the RN2483 module to run as an end device in the LoRa networks. The receiver sensitivity can be down to 146 dBm, and the transmitter produces output power adjustable up to +20 dBm. The manufacturer gives a 5 to 15-km transmission range in urban and suburban areas [41]. The maximum allowable transmission range varies depending on the specifications of the GW, which is used to complete the signal path from vehicles to the cloud server. Due to the complexity of both hardware design and embedded firmware development procedures, the usage of a ready-made LoRa GW is considered under the scope of this study. In coverage analysis, the Raspberry Pi single-board computer with RAK831 concentrator has been taken as reference, powered by Semtech's SX1301 baseband processor [42].  
On the other hand, the NB-IoT version of the VTU design has been equipped with a Quectel BC95-G module. BC95-G is a high-performance NB-IoT module that supports multiple frequency bands (B1:2100 MHz/B3:1800 MHz/B5:850 MHz/B8:900 MHz/B20:800 MHz/B28:700 MHz) and it can communicate with mobile network infrastructure through 3 GPP Release 14. Since it has handover capability, vehicle/machine tracking can be done uninterruptedly in large-scale agricultural areas covered by more than one LTE BS. BC95-G module operates between 3.1 V to 4.2 V and communicates with the microcontroller using the UART interface. The maximum output power and receiver sensitivity values are +23 dBm and 129 dBm, respectively [43]. The signal path from vehicles to the cloud server was completed through a typical LTE BS, as described in [44].