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: 8680.266667emMHz and 4340.266667emMHz. 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∈[7,10,12], within a bandwidth of BW=1250.266667emkHz and Coding Rate CR=4/6. The experiments showed that LoRa links are fully feasible over seawater at distances at least 220.266667emkm 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 280.266667emkm obstructed LOS oversea path in ISM 4340.266667emMHz band, but using costly, higher gain antennas. Furthermore, the laboratory experiments revealed that RSSI is linear in a wide range, up to −500.266667emdBm, whereas the SNR measurement chain goes into saturation for Received Signal Strength (RSS) values higher than −1000.266667emdBm. These findings enabled accurate interpretation of the results obtained in field experiments.

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Telecommunication network nodes located at very hostile environments require, among other rigorous demands, highly reliable backup power supplies. Current solutions, which are mostly based on diesel generators, have several drawbacks such as unreliable start of a diesel generator at low temperatures, maintenance of the generator due to rotary parts, and the pollution of the environment which is caused by exhaustive fumes from a diesel engine. This paper proposes the implementation of backup power supply based on proton exchange membrane (PEM) fuel cell and solar panel. In addition, it is also depicted the implementation of high-efficiency boost converter which provides adequate supply voltage for telecommunication devices. The benefits of the proposed solution are improved energy utilization, decreased need for maintenance and zero emission.

The paper presents the implementation of protocol agnostic optical transponder and media converter unit for speeds up to 2.5 Gbps. Detailed depiction of the implementation is given, including hardware design issues, as well as the signal integrity solutions. In addition, the design implemented in field-programmable gate array (FPGA) chip is discussed. On the other hand, embedded software implementation is explained, as well as the interface to the network management software that executes on PC. Finally, strategy for the verification of the unit functionalities at the end of the development stage is given, and results are presented.