Discussion about robustness of the Nødnett TETRA network
Lærdalsøyri in the mountains of Sogn og Fjordane, Norway, known for its unique concentration of historic wooden buildings, was evacuated and cordoned off recently after an inferno that swept through the town during the night led to danger for explosions.
In Lærdalsøyri eleven of Telenor's base stations went down and where burned to the ground. Because of this catastrophe, immediately questions where raised about how Nødnett would have managed if it had been built in the area. The conclusion is that Nødnett probably would withstood the fire inferno, and that it is not necessary to make changes in the architecture of the Nødnett network.
The Norwegian Directorate for Emergency Communication is committed to learn from incidents and states that it would not always have been equally good in all critical events. Also Nødnett is dependent on functioning systems for power, backup power and lines for telephone and data transmission.
Nødnett has a higher degree of embedded robustness compared to than the commercial telecommunications networks. There are two phone lines from different locations to each base station. If the connection of one of the lines drops, the other will still be operational. About 80 % of the lines between the base stations in Nødnett are owned by Nødnett and the remaining 20 % of the lines are leased lines. All Nødnett base stations and radio separate lines have at least eight hours of backup power.
It is inevitable that Nødnett will be affected by the vulnerability of the network to the commercial telecom operators, both in terms of technical problems or failure of telecommunication line and power from energy suppliers. DNK clearly states that it strives to establish their own radio links to the greatest extent possible in order to enhance the robustness. However, there are cases where this is not feasible. Nevertheless, all leased lines that are used in Nødnett have the highest guaranteed availability, with an uptime of at least 99.9 percent.
Although high availability is guaranteed, Nødnett states that they know that there are large variations in the amount of backup power in the leased lines that are provided.
In the aftermath of the "Dagmar" storm during Christmas 2011, the beginnings of a good debate about how good and reliable telecommunications networks in Norway are, was started.
Tor Helge Lyngstøl - Director DNK- states that he agrees with Aftenposten as in an editorial on 22 January stating that mobile network is not something you can rely on in crisis situations. Nødnett was developed in recognition of this fact.
