coverage
many technical rooms have to be covered by RF – a point made by Mariusz Gerlach, strategic marketing manager at SEE Telecom, manufacturer and designer of repeaters and systems for in-building and tunnel coverage for TETRA and other wireless systems. “Tunnels are, in most cases, multi- band systems with TETRA, Tetrapol, UHF, VHF and FM channels represented”, he said. FM broadcast channels are an important way of
communicating with the public in a tunnel or building in case of emergency. Handover while leaving/entering the tunnel should be designed within the coverage plan, which can be simulated for all systems in the tunnel in advance. Distributed antennas are for the most part used for GSM,
because of their improved propagation of higher frequencies inside the tunnel pipe, Gerlach explained. But if an accident occurs, such as a multi-vehicle pile-up or train crash, GSM
signals become attenuated by the physical obstructions. TETRA and other emergency systems cannot, though, afford to be lost at times of emergency. In most cases, TETRA is distributed via radiating cable, which is often protected by a concrete bench beside the tunnel wall to shield the cable from mechanical and fire damage. Redundancy is a very important element of any emergency
communications system. Te repeaters used in a tunnel – best protected in technical rooms inside the tunnels and not mounted directly in the tunnel pipe – are fed from two BTS via two different fibre cables. If one repeater fails, enough power remains in the other repeaters to send TETRA and other signals further into the tunnel. Battery back-up is a must.
A little RF goes a long way Another engineering company specializing in this field is
Enhancing TETRA coverage for a new Formula 1 circuit
tunnels, four buildings used by race team staff and their drivers for preparations and meetings during the races, and some of the stands used by spectators. The stands also include VIP areas as well as first-aid centres. In one stand, repeaters were installed at both ends of the stand using uplink and downlink antennas to carry the TETRA signal all the way through the stand. In addition, coverage systems were
Abu Dhabi’s Yas Marina circuit, one of the newest venues in the Formula One motor racing world A
t the Yas Marina motor racing circuit, in Abu Dhabi, opened in 2009, as many as four TETRA networks may be in use for a Formula One event. One network is used by circuit officials and staff – including security personnel, first aid workers, parking attendants and catering. Others are used during the race are used by the teams and drivers, the police and the FIA, the sport’s governing body.
A single TETRA base station was installed to serve the whole site – but at the opening F1 Abu Dhabi Grand Prix, the organizers discovered many
undesirable gaps in its coverage. Parts of the race circuit and several of the stands and buildings were not adequately served, and in some places the signal was blocked by a large hotel complex located in the middle of the circuit. To improve the coverage to the
required level, the Finnish radio coverage specialist Creowave and its local partner, Waves Middle East, were chosen to supply a series of TETRA coverage enhancement systems for the circuit. They completed the project in February. Repeater systems now extend the TETRA service into two underground
provided for other service buildings used for administration and as storage by race teams during tests.
This uplink antenna on one of the spectator
‘Before’ and ‘after’ signal strength indications on this engineering terminal (note the RSSI figure) demonstrate the substantial coverage improvement delivered by one of the on-site repeaters
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stands feeds a wall-mounted TETRA repeater (right) and downlink antenna serving radio users in the interior of the building
TE TRA TODAY Issue 4 2011
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