TETRA REPEATER APPLICATIONS
Various TETRA Repeater Applications
General
This document describes how Avitec TETRA Repeaters can be configured for different
requirements.
Repeater types
Avitec presently has three Repeater models in the product range. The BSR402 is a
distributed gain, band selective repeater, mainly intended for indoor applications. It
provides medium gain and medium output power levels in each signal direction. The
BSF414 is a medium gain repeater for fibre optic fed applications with high output
power capability in the downlink path. The CSR414 is a channel selective repeater with
high gain and high output power for 1 to 4 carriers.
Applications
TETRA Repeaters can be used in open areas or in confined spaces.
Open area applications for Repeaters usually exist in hilly terrain. Confined areas
include tunnels or inside buildings.
Open areas
Repeaters with air interface are normally used in these areas. The most suitable type
of Repeater for this application is the CSR414 channel selective Repeater. The
Repeater is connected to a donor antenna (the antenna pointing towards the base
station site). The donor antenna should be highly directional, so that signals in the
TETRA band appearing from other directions are attenuated. A highly directional
antenna provides additional gain (around 10 dBi), which lowers the output power
requirements of the repeater. The Repeater server antenna (the antenna pointing
towards the area that needs improved coverage by the repeater) must also be highly
directional. The most important parameter in an open area Repeater installation is the
antenna isolation, which must be at least 10 dB higher than the Repeater gain. The
CSR414 provides more than 80 dB of total gain. The antenna isolation must then be
more than 90 dB. This value is difficult to realize at 400 MHz unless directional
antennas are used for both donor and server antennas. The most effective way of
increasing the antenna isolation is to increase the vertical separation between the two
antennas. The use of a building structure as an additional “shield” between the
antennas also helps.
 Avitec AB 2003
Commercially confidential
page 1(8)
TETRA REPEATER APPLICATIONS
If optical fibre cables between the base station site and the selected Repeater site are
available, a fibre fed Repeater for open area coverage can be used. The main
advantage of this configuration is that the need for antenna isolation is eliminated. The
server antenna can be omnidirectional and the Repeater output power can be
increased. The BSF414 Repeater is intended for these applications.
Confined areas
Coverage inside buildings can be provided with the BSR402 using donor and server
antennas. The output power level in DL from the BSR402 into an indoor server antenna
is optimized for these applications. Excessive power levels from an indoor antenna
tend to cause blocking of terminals relatively close to the antenna. The BSR402
distributed gain concept is ideal for indoor coverage solutions where several antennas
are used for large areas. Up to 4 BSR402 DL units can be connected to one single
BSR402 UL unit.
An alternative to the distributed gain concept using the BSR402 is the use of the high
power channel selective Repeater CSR414. The high gain of the CSR414 is an
advantage in cases where the signal levels from the donor base station outside the
building are relatively low. A passive antenna system can be connected to the output of
the CSR414. A channel selective Repeater only amplifies the carriers from a
designated donor base station, which reduces the risk for unplanned hand-overs and
simplifies network planning.
Tunnels can use the same concept as used for in-building coverage. The server
antenna(s) inside the tunnel should, in this case, be directional. The main lobe of the
server antenna should be as narrow as possible. One server antenna can only cover a
limited length of tunnel. In long tunnels, requiring several server antennas, the problem
of transporting the rf signals from the tunnel mouth to the respective Repeaters and
antennas becomes an important issue.
The BSR402 accepts up to 20 dB of coax cable losses between the two distributed
gain units. This allows up to several hundred meters of distance between the unit
placed at the tunnel mouth and the unit(s) inside the tunnel.
Some tunnels have radiating cables installed for other radio services, that can be used
for TETRA. The major difference between antennas and radiating cable is the high
coupling loss of the radiating cable. The output power from a TETRA Repeater
connected to a radiating cable must be relatively high. The rf unit of the BSF414
Repeater uses a feed-forward power amplifier to provide the DL power levels needed
for radiating cable applications. For tunnel applications using radiating cables, a
combination of a BSR402 UL unit and one or several BSF414 rf units is suitable. Very
long tunnels may require fiber optic converters between these units, if the
interconnecting cable losses exceed 20 dB.
 Avitec AB 2003
Commercially confidential
page 2(8)
TETRA REPEATER APPLICATIONS
Repeater supervision
All applications that use an air interface between the Repeater site and the base
station site can have a wireless interface for remote control and supervision of the
equipment. This would ideally use the data capabilities of the TETRA network, similar
to the way GSM Repeaters are supervised today. GSM or TETRA industrial type
modules can be used in the equipment. It is also possible to connect the repeater to a
fixed line modem for remote communication. In the fibre optic Repeater systems,
remote communication uses the transmission path via the fibres.
Conclusion
This document has described various concepts to solve TETRA coverage problems in
open and confined areas with Repeaters. There is no ”general solution”, but most
coverage problems can be solved by at least one of the suggested configurations.
Each case must be evaluated separately before a suitable solution is suggested.
Attachements
5 examples of Repeater configurations, described in this document, are attached on
the following pages.
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Commercially confidential
page 3(8)
TETRA REPEATER APPLICATIONS
EXAMPLE 1
Donor Antenna
Server Antenna
CSR414
Coverage with air interface and CSR414
The antenna isolation in this example must be more than 10 dB higher than the antenna isolation.
Using directional antennas for both server and donor on the same mast, the vertical separation
needs to be around 20 meters if this isolation is be be realized. This concept can also be applied
for in-building coverage The antenna isolation in this case is easier to realize, since the building
walls and structure can be used as a “shield” between the in-door and the out-door antennas. The
CSR414 is ideal in applications requiring high gain.
EXAMPLE 2
 Avitec AB 2003
Commercially confidential
page 4(8)
TETRA REPEATER APPLICATIONS
BTS TX Antenna
Server Antenna
BTS RX Antenna
TETRA
BTS
BSF414
HUB4XX
Monomode fiber
Open Area coverage with fiber optic fed Repeater BSF414
The base station is connected via couplers to the HUB unit, which transforms the rf signals to
modulated light. Two fibres are used, one for UL signals and one for DL signals. With DWM
technology using 1550 nm and 1310 nm lasers, one fibre could be used for both signal directions.
Antenna isolation is not a concern with this configuration. Omnidirectional or directional server
antennas can be used. Several Repeaters can be connected to one HUB unit.
EXAMPLE 3
 Avitec AB 2003
Commercially confidential
page 5(8)
TETRA REPEATER APPLICATIONS
BTS TX Antenna
Server Antenna
Server Antenna
BTS RX Antenna
TETRA
BTS
BSF414
BSF414
HUB4XX
Monomode fiber
Confined area coverage (Tunnel) using two fiber fed BSF414 Repeaters
In this example, two BSF414 Repeaters are used to provide the required coverage in a
relatively long tunnel using directional server antennas. The fibre length can be up to 20
km between the base station site and the repeater site(s).
EXAMPLE 4
 Avitec AB 2003
Commercially confidential
page 6(8)
TETRA REPEATER APPLICATIONS
BTS TX Antenna
Radiating Cable
BTS RX Antenna
Splitter
TETRA
BTS
BSF414
Splitter
BSF414
HUB4XX
Monomode fiber
Confined area coverage (Tunnel) using two BSF414 Repeaters and Radiating Cable
The optical fibre fed BSF414 Repeaters provides sufficient downlink output power to give good rf
coverage in a tunnel with a radiating cable. For very long tunnels, this configuration is the only
acceptable solution. Several BSF414 Repeaters can be connected to the same base station HUB.
Coverage distances per Repeater depend on type of cable, but up to 2 km is normal. Other radio
services can use the same radiating cable.
EXAMPLE 5
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Commercially confidential
page 7(8)
TETRA REPEATER APPLICATIONS
PICKUP
ANTENNA
SERVER
ANTENNA
BSR402 UL
BSR402 DL
SERVER
ANTENNA
SERVER
ANTENNA
BSR402 DL
BSR402 DL
BSR402 DL
In-building Coverage using the BSR402 Distributed Gain Repeater combination
Good In-building Coverage requires a uniform signal level distribution over the coverage area.
Several radiation points and the use of relatively low RF power levels limits the risk of receiver
blocking inside the building. The BSR402 Distributed Gain Repeater is ideal for this application if
the gain requirements are moderate (60 dB). The BSR402 Repeater gain is distributed over two
units, which are placed near the respective antennas. The coax cable connecting the two units can
have up to 20 dB of loss without impairing the Repeater performance. Several BSR402 DL units
can also be connected, via splitters, to a common BSR402 UL unit. Even large buildings can be
given good TETRA coverage at low cost with this alternative. Very thin coax cables can be used
for interconnecting the repeater units, resulting in lower installation costs.
 Avitec AB 2003
Commercially confidential
page 8(8)