Base
stations enable radio communication between the radio
exchange and cordless phones. A base station communicates
with the radio exchange via two 2B+D interfaces, requiring
a two twisted pair cable. The two 2B channels provide
eight 32kbit/s speech path between a base station and
the radio exchange, enabling a base station to handle
eight simultaneous calls. Except for data communication
these two twisted pairs can also be used to distribute
power to the base stations.
Base stations can be powered either via
a local power supply or via the modular cabinet. With
the first method, an AC-adapter or another power source
that is not routed via the cabinet powers base stations.
The maximum cable length between base station and radio
exchange is only data limited and may reach up to 3500
metres. With the second method, power is distributed via
the cabinet and base station cabling. The cable length
between base station and cabinet now depends on the number
of twisted pairs used for power, the type of cable and
environmental noise.
The number of base stations used in a
system depends on the area to be covered and the traffic
density. Typical in-house coverage is a 20-metre radius.
In practice the cell size may vary between 10 metres indoors
in worst case situations, up to 300 metres outdoors in
free space.
The Ericsson BS3xx range of base stations
offers a variety of coverage patterns to suit different
situations. By choosing the right mix of base stations
and the appropriate antennae quality coverage and sufficient
traffic capacity exactly where needed can be ensured. |
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The
BS330 base station is the standard solution for most business
premises. Typical indoor coverage is 30 metres, actual
coverage depending on factors such as the spacing of walls
and the building materials used. The BS330 supports up
to 8 simultaneous speech calls per base station. Whilst
the BS330 is primarily designed for indoor coverage, an
outdoor housing is available for outdoor applications.
Outdoor coverage is up to 300 metres. |
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The
BS340 shares the basic characteristics of the BS330, but
comes with two external antennas. These default antennae
provide a spherical coverage pattern. A number of directional
antennas are also available, which radiate more in certain
directions than in others. The advantage is to direct
coverage exactly where you need it, reducing overall cost
in cases where the ideal coverage shape is not a sphere.
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·Omni-directional single antenna.
Coverage mainly in the horizontal plane. Effectively
squashes the basic sphere of the BS340 into a shape
closer to a discus. This doubles the range to a maximum
of 600 metres in alle directions outdoors, with a reduced
coverage in the vertical plane.
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Directional single antenna
Coverage mainly in one direction. The coverage 'envelope'
is flattened slightly, increasing the maximum range
to 1000 metres. Most suitable for linear coverage,for
example to cover walkways between buildings, tunnels,
or to provide a radio link between a remote BS370 and
a host base station.
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Directional
dual antenna
Coverage mainly in one direction. Compared to the directional
single antenna, the maximum range is not as big but the
height of the coverage 'envelope' is greater. |
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| BS370
wireless relay station |
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The
BS370 wireless relay station is suitable for low to medium
traffic capacity areas where cabling is a problem. The
BS370 is connected to the cordless PBX via a radio link
to a BS330 or BS340 'host' base station. It extends the
coverage area of the host base station without the need
to lay a new cable, saving man-hours and avoiding disruption.
It only needs a local power adapter, so can for instance
be mounted on a lamppost and use the same power supply. |
The
BS370 has a maximum capacity of up to 5 simultaneous speech
calls with handover in its coverage area. The host base
station can support up to 8 simultaneous speech calls
in its own coverage area, minus the number of calls made
over the BS370 wireless relay station. The BS370 is usually
positioned so that its coverage sphere overlaps with that
of the host base station. However, it also has an input
for a 3rd antenna, usually the directional single antenna.
This means it can be placed up to 1000 metres away. |
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