Low Power Wide Area Networks (LPWANs) are gaining attention in both academia and industry by offering the possibility of connecting a large number of nodes over extended distances. LoRa is one of the technologies used as a physical layer in such networks. This paper investigates the LoRa links over seawater in two typical scenarios: clear Line-of-Sight (LOS) and obstructed path in two different Industrial, Scientific and Medical (ISM) radio bands: $868$ MHz and $434$ MHz. We used three different LoRa devices in the experiments: the Own Developed LoRa Transceiver (ODT) and two commercial transceivers. Firstly we investigated transceivers’ Receive Signal Strength Indicator (RSSI) and Signal-to-Noise (SNR) measurement chain linearity and provided correction factors for RSSI to correlate it with actual signal levels received at transceivers’ inputs. Next, we carried out field experiments for three different LoRa Spreading Factors, $SF\in \left[7,10,12\right]$ , within a bandwidth of $BW=125$ kHz and Coding Rate $CR=4/6$ . The experiments showed that LoRa links are fully feasible over seawater at distances at least $22$ km long, using only low-cost off-the-shelf rubber duck antennas in LOS path condition in both ISM bands. In addition, we showed that LoRa links can be established over $28$ km obstructed LOS oversea path in ISM $434$ MHz band, but using costly, higher gain antennas. Furthermore, the laboratory experiments revealed that RSSI is linear in a wide range, up to $-50$ dBm, whereas the SNR measurement chain goes into saturation for Received Signal Strength (RSS) values higher than $-100$ dBm. These findings enabled accurate interpretation of the results obtained in field experiments.

We present a novel design and implementation of a LoRa transceiver with enhanced characteristics which operates in two industrial, scientific, and medical (ISM) bands of 868 MHz and 434 MHz. Comparative tests with two widely utilized commercial transceivers were carried out to demonstrate the superior performances of the proposed transceiver, namely improved sensitivity by 15-25 dB and better immunity to interference. Field tests were performed by establishing a very long line-of-sight over land link of 112 km. The main achievements of this letter are: 1) the design of a novel high-sensitivity low-cost miniaturized LoRa transceiver; 2) demonstrating a very long LoRa link with low-cost commercial-off-the-shelf omni-directional rubber duck antennas with standard-compliant output power in the 868 MHz ISM band; and 3) temporal analysis of the link variability for different spreading factors (7, 10, 12) within a fixed LoRa bandwidth of 125 kHz.

An embedded system for gamma and neutron discrimination in mixed radiation environments is proposed, validated with an off-the-shelf detector consisting of a Cs2LiYCl6:Ce (CLYC) crystal coupled to a silicon photomultiplier (SiPM) cell array. This solution employs a machine learning classification model based on a multilayer perceptron (MLP) running on a commercial Field-Programmable Gate Array (FPGA), providing online single-event identification with 98.2% overall accuracy at rates higher than 200 kilocounts per second. Thermal neutrons and fast neutrons up to 5 MeV can be detected and discriminated from gamma events, even under pile-up scenarios with a dead-time lower than 2.5 μs. The system exhibits excellent size, weight, and power consumption (SWaP) characteristics, packed in a volume smaller than 0.6 liters and weighing less than 0.5 kilograms, while ensuring continuous operation with only 1.5 Watt. These features render our proposal suitable for embedded applications where low SWaP is critical and radiation levels manifest large count rate variability, such as space exploration, portable dosimeters, radiation surveillance on uncrewed aerial vehicles (UAV), and soil moisture monitoring.