Note: Descriptions are shown in the official language in which they were submitted.
. CA 0221~788 1997-09-18
Description
Fixed station of a mobile radio system
The invention relates to a fixed station accord-
ing to the precharacterizing clause of patent claim 1.
The range of a mobile radio system, for example
a cordless telephone, which comprises a fixed station and
one or more mobile stations, is essentially governed by
its transmitted power and its receiver sensitivity. In
this case, the transmitted power is emitted uniformly in
all directions, that is to say at least approximately
omnidirectionally in order, on the one hand, to be
useable universally in any environment and, on the other
hand, to achieve the same range in every direction. If
however, a single point in time is considered, then, from
the point of view of the fixed station, that is to say in
the example the base station of a cordless telephone,
only a fraction of the transmitted energy is emitted in
the direction of the mobile station which is in use at
this instant, that is to say, in the example, the mobile
section of the cordless telephone. By far the majority of
the transmitted energy is, in contrast, not used and may
even interfere with other devices. The range o~ the
radiation is limited by the transmitted power, the path
attenuation and the received power. The path attenuation
is a constant factor in this case, and cannot be reduced.
The transmitted power cannot be increased indefinitely.
In principle, the received power, and thus the range, can
be increased by directional transmission, that is to say
by the use of a focused directional antenna which emits
the available energy concentrated in a specific direc-
tion. The use of directional antennas in radio systems
for this purpose is generally known.
The object of the invention is, by refining the
fixed station, to provide an advantageous capability for
improving the
CA 0221~788 1997-09-18
transmission behavior between the fixed station and the
mobile stations of a mobile radio system, in particular
of a cordless telephone.
This object is achieved in the case of a fixed
station according to the precharacterizing clause of
patent claim 1 by the features specified in the charac-
terizing part of this patent claim.
Expedient developments and refinements of the
fixed station specified in patent claim 1 are specified
in claims 2 to 6.
The following text uses a block diagram, which is
shown in a figure, to describe a fixed station according
to the invention.
This fixed station of a mobile radio system may
be, for example, the base station of a cordless telephone
operating to the DECT Standard.
The illustrated fixed station has an antenna
device 1 which is connected via an antenna diplexer 2
either to a transmitter 3 or a receiver 4. The antenna
device 1 is formed as an antenna array which has a
plurality of individual radiating elements and whose
radiation characteristic can be shaped to produce a
directional beam characteristic. Individual radiating
elements in this antenna array can be connected and
disconnected and/or specific phase relationships can be
selected between these individual radiating elements to
allow a suitable directional beam characteristic to be
produced, which can then be aimed in different direc-
tions.
The fixed station illustrated in the figure
includes a control mechanism 5 for adjusting the radia-
tion characteristic of the antenna device 1. The radia-
tion characteristic, which has the form of a focused
directional beam, of this
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r CA 0221~788 1997-09-18
antenna device 1 is always matched to the instantaneous
location o~ that mobile station which is being trans-
mitted to at the relevant time by connection of the
transmitter 3, or is being received from at the relevant
time by connection of the receiver 4. The drive data for
adjusting the respective radiation characteristic of the
antenna device 1 is derived, using an algorithm, from the
received field strength measured in the control mechanism
in a measuring device 6 and/or directly from the
received digital data, using a device 7 in which
bit/burs~ faults are identified. The actual computational
evaluation in order to define the drive data is carried
out in a central section 8 o~ the control mechanism 5,
which executes the algorithm. A memory device 9 in the
control mechanism 5 is used to buffer-store the asso-
ciated radiation characteristics ~or 1 to n mobile
stations, in the form of drive data for the antenna
device 1.
The memory device 9 in the control mechanism 1
can advantageously be used to store two radiation charac-
teristics, whose difference corresponds only to a minor
change in the characteristic. This makes it possible to
avoid interruptions in reception from fading holes in the
case of a non-moving mobile station.
