Communication links are an important part of remotely operated or autonomous vessels, as control signals or telemetry data need to be transmitted to the ground stations.

For this reason, we need to assess the range of the most common wireless technologies used in such cases as WiFi and LoRa. To overcome the challenges of conducting a long-range experiment at sea we emulated the conditions using land to land communications that happen over sea. To emulate transmission of over sea environment, we chose specific locations within a gulf so the links could travel over water. This eliminated the need to use boats for these experiments and minimised the restrictions and equipment needed.

Our goal was to measure the link performance capabilities of WiFi and LoRa radio links as a factor of range from 1.5Km-10Km. We allocated a fixed location which we called ‘base’ location and part of the team stayed at the base station during the experiment. The rest of the team was the mobile station that had the task to sail,  set up the equipment and perform the measurements at each location.

Figure 1: Locations of Longest Range Tested

Each station had the following basic blocks: A Power Management board to power the Access Points and the Raspberry Pi, used for controlling the test fixture. Two Access Points, one for each band 2.4GHz and 5GHz MIMO (2 antennas). A battery to provide power, a Raspberry Pi4 to provide LoRa connections and control the WiFi and finally a laptop to connect to the setup in order to initiate the test and acquire the measurements using Python scripts. The difference between the mobile and base station was that the base station had an omnidirectional antenna while the mobile station used a dish (directional) antenna.

Figure 2: Block Diagram of Base and Mobile Stations

In summary, the experiment indicated that we were able to have a reliable LoRa link up to 4.6Km with omnidirectional antennas, while with the WiFi and using a directional antenna at one endpoint, we reached almost 10Km range with no packet loss at small and medium length packets and about 60% loss on large packets using ping (RSSI -74dBm). The direction of the antenna was critical to achieve a link. Once properly aligned the link was relative good.

For more information on this topic, you can contact MDigi.C@cmmi.blue