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VHF marine radio VHF is the internationally used technology for marine radio in the frequency range 156—163 MHz. Typical range of VHF is reported to be up to 70 nautical miles from a land-based station [56], while ship-to-ship signal range is below 40 km [57]. However, VHF is limited in supported data rate, which is below 30 kbps. While VHF may be sufficient to transmit sensory readings from ships to shore-deployed fog nodes [4] for aggregation and forwarding, the low data rate is unsuitable for agile transfer of larger data (e.g. video streams or VM images).

Satellite systems offer higher speeds compared to VHF and provide the greatest signal coverage, which is an important factor considering the distances involved in the marine domain. Yet, due to their high cost, these are a viable option only for larger vessels [57, 58].

Low-power wide-area networks (LPWANs) long range (LoRa) has been receiving attention lately as an energy-efficient, long-range wireless technology. In the mF2C project [29], the physical layer-LoRa, accompanied with LoRaWAN at the data link layer is used for ship-to-ship communication, while [59] use it for ship-to-shore communication in harbors. LoRa with LoRaWAN can cover up to 15 km in rural areas with a data rate up to 37.5 Kbps [60], making it a lower-energy alternative to VHF.

Sigfox and NB-IoT can be considered as competitors to LoRaWAN. While LoRaWAN and Sigfox operate in unlicensed bands, NB-IoT operates in licensed frequency bands.

Dedicated short-range communications (DSRC) is another technology defined especially for VANET, which are one-way or two-way short-range to medium-range wireless communications designed for allowing V2V and V2I communications. It is characterized by its frequency of 75 MHz licensed spectrum in 5.9 GHz band, which is provided by Federal Communications Commission (FCC) in the United States [20, 26].