Enhancing TETRA coverage at Oulu Airport

Finavia Corporation turned to Creowave to enhance TETRA coverage at Finland’s Oulu Airport with the aim of ensuring safe and secure communications across the whole of its airfield

Enhancing TETRA coverage at Oulu Airport

Creowave Oy was chosen to deliver a turnkey TETRA network coverage enhancement solution at Oulu Airport to secure communications and the safety of both travellers and authorities working at the airport.

Oulu Airport is located in the northern part of Finland, in Oulunsalo, about 15 kilometres from Oulu city centre. The airport is run by the Finavia Corporation, which maintains the network of 25 airports in Finland. Finavia Corporation serves its customers in five different business areas: airport operations, air navigation, commercial operations, real estate and airport services.

Finavia is responsible for the infrastructure and development at all 25 airports. It also controls the use of Finnish airspace, provides air navigation services at the airports and employs approximately 2,500 people.

Several different authorities have to work and communicate fluently at Oulu Airport to secure its operations, as well as ensuring the safety of travellers and staff. The border authority, police, customs, security and check-in personnel all use the TETRA network on a daily basis.

The attractiveness of the Oulu area to tourists and business travellers has grown over the last few years. This has led to a drastic increase in the number of aircraft passengers traveling to Oulu, which in turn has meant the airport has had to expand in size by 50%.

The new extension of Oulu Airport became operational at the end of September 2011. All operations beyond the security check area were transferred to the new terminal. Naturally, since the building size was now much larger, the security regime for passengers and employees needed to be re-examined and the communications requirements re-evaluated.

In June 2011, Finavia chose Creowave to make a site survey and coverage plan of the TETRA coverage at the airport. In Finland the TETRA network is called the VIRVE network and it is used by the Finnish authorities all over the country. VIRVE is controlled and maintained by State Security Networks, which also inspects and approves all VIRVE network sites.

TETRA coverage at the site

The site survey conducted by Creowave Oy in July 2011 revealed that the signal was weak in both the new and old parts of the airport. The TETRA coverage did not reach all the new premises –  cellars, customs areas and the border guard, and, most importantly, the basement of the air traffic control tower.

In addition, it was discovered that areas located in the older part of the airport, such as check-in areas, baggage hall and the air shelter, lacked an adequate TETRA signal. The new security check area had not been finished at the time of the site survey, but it was already lacking a TETRA signal even though all the walls had not yet been built.

These gaps in TETRA coverage could cause life-threatening situations, so clearly the TETRA network coverage had to be enhanced. The authorities working at the airport were told during the site survey that problems in the TETRA coverage had been discovered in many locations.

To ensure reliable connections and safety, the field strength target for the TETRA signal was set at -85dBm. The goal was to have the TETRA signal greater than this at 95% of the covered area. This led to the end target of having an average field strength better than -75dB.

Coverage plan

Creowave used iBwave Design Software to provide a thorough and up-to-date coverage plan for the end customer. To ensure the target signal levels were achieved, two TETRA channel selective high power repeaters (CWR 380 HP2) were chosen to enhance the TETRA network signal in areas with weak coverage.

The use of TETRA channel selective high power repeaters in this case not only assures reliable communications within the whole airport, but also provides an opportunity for possible enlargements of the building in the future. The repeaters were installed in the airport’s equipment premises in order to have easy access to the antennas on the airport roof. For the basement of the air traffic control tower, one TETRA channel selective repeater (CWR 380 TH 2) proved to be an adequate and cost-effective solution.

For the older part of the airport, including the check-in area, baggage hall and air shelter, a TETRA channel selective high power repeater (CWR 380 HP2) was chosen. Its maximum RF output power for downlink is +36dBm, with a maximum gain of 85dB. The ground level indoor coverage was achieved by using a leaky feeder and two antennas, while the first and second floor coverage were both realised using two indoor antennas.

In the aisle and tunnel areas, the TETRA indoor coverage was enhanced by connecting the repeater signal into leaky feeders placed on the cable shelves. Open areas are covered with indoor antennas. The same solution was used in all areas of the airport.

A TETRA channel selective high power repeater (CWR 380 HP2) was also required to provide the necessary coverage for the new parts of the airport. In these areas, the ground floor coverage was ensured by deploying two indoor antennas and leaky feeders, while the first floor indoor coverage was achieved with two indoor antennas.

For the air traffic control tower, a repeater with lower power was sufficient to ensure the set signal levels and coverage were met. The maximum output power of Creowave TETRA channel selective (CWR 380 TH2) is +17dBm, with a maximum gain of 85dB. The ground floor coverage of the air traffic control tower was ensured by installing an indoor antenna and leaky feeders.

Installation and acceptance measurements

According to the coverage plan, Finavia required Creowave to begin delivery of the TETRA indoor coverage to Oulu airport in October 2011. The agreement included two TETRA channel selective high power repeaters and one TETRA channel selective and all the antennas, cables, leaky feeders, switches, etc. needed for the installation.

The repeaters were delivered and installed at the airport according to the plan and the end measurements were taken in early March this year. The end measurements were tested using the Cassidian THR9i terminal and portable spectrum analyser. The whole airport was walked through and measured and no signal levels in the buildings was found to be lower than -75dB.

In the orginal site survey, the weakest signal strengths were measured in the air traffic control tower basement. Following the new TETRA installations, the signal level was found to be as good as -65dBm. Overall, the average field strength at the airport is now -70dBm, which is 5dBm better than the original target.

’The target was achieved as planned. The thorough site survey and coverage planning were keys to success. Now both the employees and travellers can feel safe in Oulu Airport. The TETRA network for authority use is working excellently in every corner,’ says Taisto Soikkeli, technical director at Creowave.

Written by Wireless magazine
Wireless magazine

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