World record in mobile network in a tunnel

The mobile operators Telia and Telenor with Bane NOR set world record. With 560 megabits per second the future train passengers can enjoy a high speed mobile network on their journey, also on routes with many travellers.

Illustrasjonsfoto: Øystein GrueThe mobile network in old rail tunnels does not manage to meet the modern train passengers' needs for mobile data. On trains with many passengers, it is today difficult to get good network coverage. Therefore, the Norwegian Ministry of Transport and Communications has allocated funds to improve capacity and increase the transmission rate of mobile telephony in tunnels.

- Telia, in cooperation with Bane NOR the Follo Line project, has developed a pilot to show how this can be solved by technology that provides high speed and can be used in all rail tunnels, says Dag Wigum, Technical Director of Telia Norway.

The need for speed
Together, Telia, Telenor and Bane NOR have built 4G + which in this case equals 1800MHz and 2600 MHz.

- It provides capacity and speed in the network that will meet the passengers need in order to e.g. working, downloading movies, listening to music or reading up on news, explains Wigum.

Building a high-speed mobile network was a central discussion in the development of the Follo Line. The Follo Line, which opens in 2021, contains a 20 km. railway tunnel with two separate tubes, between Oslo Central Station and Ski Station. The double track will cover the need for increased capacity for train passengers traveling south east from Oslo. Project Director in the Follo Line, Per David Borenstein, is very pleased with what Telia, Telenor and Bane NOR have achieved.

 - This is impressive work and Bane NOR are looking forward to offer a high-speed mobile network to our future train passengers. Now we are building a mobile facility with a capacity that will provide good, stable and satisfactory mobile coverage for the many train passengers inside the long tunnel on the Follo Line, says the Project Director.

A world record in a tunnel
The world record was carried out in an old road tunnel in Holmestrand, Norway, where a test facility was installed. The test installation was built in collaboration by Bane NOR the Follo Line Project, Telia, Telenor and RFS. The measurements during the technical test came in at a total of 580 megabits per second, which is a world record in high–speed network in a tunnel. Inside the tunnel, four radiating cables was installed and connected to a radio transmitter with 4G 4x4 MIMO setup, instead of traditional one radiating cable. As far as we know, this has never been done before in a full-scale tunnel. In addition, modern trains in Norway today, will be equipped with 4G repeaters, which makes the signal reception on the train much better and thus improve the user experience.

About the test – for the technical mind

  • Test was done with a 4x4 MIMO Huawei-radios with two band of  20 MHz LTE1800 and 20 MHz LTE2600.
  • Four RFS radiating cables were used: One cable on each side with vertical polarization and one on each side with horizontal polarization.
  • The tests were taken both stagnant at fixed points and at different speeds.
  • The phones used were Sony XZ Premium with 64 QAM and Sony XZ1 with 256 QAM.
  • The results show that it was achieved approximately 95 percent of theoretical maximum speeds of 4x4 MIMO in the tunnel.
  • The results also show that we have approximately 100% increase in rates from base station to phone when we go from SISO to 2x2 MIMO and from 2x2 MIMO to 4x4 MIMO.
  • Telia plans to test further with other phones to achieve even higher speeds.