In the middle of the tourist season in Martinique, a mysterious jamming disrupted Orange Caraïbe’s telephone and mobile Internet services in Fort-de-France, pushing the National Frequency Agency (ANFR) to intervene.
A few days ago, the ANFR detailed one of its recent significant interventions, started with the report from the operator Orange Caraibe, on March 3, 2023, with major interference in the frequency band 1 920 – 1 930 MHz, around a Martinique cruise terminal. The ANFR investigation revealed that the jamming was linked to the movements of a foreign vessel. A look back at a case which, without any intention to cause harm, could have had significant consequences.
The ship disrupted Orange’s 3G, because it used the same frequencies as in North America
Informed of the jamming, the National Frequency Agency spoke to the prosecutor and began its investigation. Orange Caraïbe’s observations indicate a disturbance linked to ship movements. The operator notices that as soon as a ship enters the cruise terminal, the 3G network experiences disruptions. As soon as it returns to sea, the network returns to normal.
During its inspection, the ANFR waits for the ship firmly, to carry out a port state control (PSC), a procedure for controlling the radio equipment of a foreign boat. The agency immediately perceives the disturbing signal, and discovers a DECT wireless network (digital enhanced cordless telecommunication) on board the ship. This network is used so that crew members can communicate with each other outside the ship.
Problem, therefore, DECT transmits in the band 1920 MHz – 1930 MHz, following the frequency plan for North America. The ship simply ignores local specificities. Although DECT systems can adapt via GPS, the boat had not programmed the European frequencies (1880 – 1900 MHz).
The authorities are lenient with the ship, but this is not always the case
The occupants of the ship had not thought that Martinique, although located more on the side of the Americas, is a French department. And that the latter therefore always uses a European frequency plan, which also allows travelers to use the same devices between France and the Antilles.
The frequency band used by the incriminated vessel is allocated to the Orange subsidiary in Martinique, which operates it for its 3G service. The ship’s use of the tape could have created some chaos, and prevented calls for help.
If the fault is indisputable, the ANFR and the authorities showed clemency towards the crew, who were unaware of the subtlety that we mentioned. Still, although a DECT system can automatically adapt its frequency plan, it could not be reprogrammed on the boat concerned, which led to its shutdown, in favor of the use of good old walkie talkies .
According to the ANFR, this unintentional interference is common. Sometimes, however, the authorities can be less lenient, in that the maritime prefecture can completely suspend the passage of a ship, and the public prosecutor can initiate legal proceedings.
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