Method of Operating a Base Station and Base Station
Field of the Invention
The invention relates to a method of operating a base
station for a cellular communications network. The
invention further relates to a base station for a cellular
communications network.
Background
Conventional base stations for cellular communications
networks comprise antenna systems having one or more
antennas which are mounted and adjusted during an
installation of the base station in the field.
Particularly, a tilt angle between a main beam direction of
the antenna's characteristic beam pattern and a horizontal
plane is manually adjusted by service technicians during
the installation. After the installation, the tilt angle
remains fixed.
There is a need to provide a more sophisticated base
station and method of operating a base station which offer
increased flexibility regarding the operational
characteristics of the base station.
Summary
According to the present invention, regarding the above
mentioned method of operating a base station, this object
is achieved by: adjusting a tilt angle of the antenna
and/or of a beam pattern of said antenna, wherein said step
of adjusting is performed depending on a quality measure
which characterizes the quality of a signal transmission
associated with said antenna. The inventive adjustment of
the tilt angle depending on said quality measure
advantageously provides an additional degree of freedom for
operating the base station. Thus, ongoing data
transmissions with terminals served by the base station may
be optimized in a real-time or at least nearly real-time
fashion, i.e. the tilt angle may be modified during an
ongoing data transmission to improve a quality measure
characterizing the ongoing data transmission.
Particularly, according to an embodiment, the tilt angle
adjustment is performed dynamically, i.e. without
interrupting an ongoing data transmission via the antenna
the tilt angle of which is adjusted.
Preferably, a signal to noise plus interference ratio,
SINR, is used by the base station as a quality measure to
assess the quality of a signal transmission. Of course,
other suitable parameters such as a bit error rate, BBR,
may also be used to characterize the quality of a signal
transmission between the base station and a terminal.
Alternatively or in addition to the aforementioned methods,
an uplink signal transmitted from a terminal to the base
station may be employed by the base station as quality
measure characterizing the quality of signal transmission.
Particularly, if equipped with a plurality of antenna
elements such as e.g. in the case of a phase-controlled
antenna system, the base station may analyze signals
received in the uplink direction regarding their phase
differences, e.g. in the sense of a per se known direction
of arrival (DoA) estimation. I.e., from evaluating received
uplink transmissions regarding the DoA parameter, the base
station may conclude that a tilt angle that has been used
for said uplink transmission is not yet optimal or has e.g.
yielded at least some improvement over a previously set
tilt angle. Thus, by analyzing the DoA parameter, a further
degree of freedom is provided for the base station to
accurately assess whether improvements may be achieved by
further changing the tilt angle.
Generally, the adjustment of the tilt angle may be
performed in different ways. Firstly, if the base station's
antenna is a phase-controlled antenna the beam pattern of
which can be dynamically controlled by altering a phase of
at least one signal supplied to an antenna element of said
antenna (which is usually done by a corresponding antenna
controller) , an adjustment of the tilt angle may possibly
be achieved by correspondingly controlling the beam
pattern. I.e., the antenna may be electrically controlled
so as to alter the tilt angle between an axis of a main
lobe of said beam pattern and a horizontal plane.
Secondly, if the base station's antenna is not a phasecontrolled
antenna but rather a conventional antenna
without the possibility of electrically controlling the
beam pattern, and especially the tilt angle of the main
lobe axis, a tilt angle adjustment in the sense of the
embodiments may be accomplished by mechanical driving means
which rotate the antenna around a predetermined axis such
as e.g. an axis in the horizontal plane which extends
substantially perpendicularly to the direction of
propagation defined by the main lobe of the beam pattern.
Of course, a combination of the aforementioned methods may
also be employed for tilt angle adjustment.
According to a preferred embodiment, the method of
operating a base station comprises the following steps:
- adjusting the tilt angle by increasing or decreasing
it by a predetermined amount,
- determining a value of said quality measure after said
adjustment, and
- evaluating, whether said quality measure has
increased.
If the quality measure has already increased substantially
after a first step of adjusting, the process may end. The
increase or decrease of the quality measure may be
determined by comparing the value of said quality measure
obtained after said adjustment with a corresponding value
that has been obtained prior to adjusting.
According to an embodiment, it is proposed that said steps
of adjusting, determining and evaluating are repeated for a
predetermined maximum number of iterations or until a
predetermined increase of said quality measure has been
detected .
According to a further advantageous embodiment, the amount
by which the tilt angle is increased or decreased in said
step of adjusting is determined based on at least one of:
operational parameters of said base station, a current
number of iterations, the maximum number of iterations, a
current value of said quality measure, a value of said
quality measure obtained prior to a previous step of
adjusting, a random event or a pseudo- random event.
Taking into consideration operational parameters of the
base station such as
- a number of terminals/users currently served,
- an average signal to noise plus interference ratio,
SINR, for some or all user connections currently
served,
- a distribution of distances between the terminals
which are currently served by the base station and the
base station
advantageously enables to precisely adapt the adjustment
according to the embodiments to a specific operating
scenario of the base station.
E.g., if a comparatively high number of terminals is served
and if their distance distribution is rather flat, i.e. if
there are many terminals at many different distances to the
base station, it may be concluded that performing the
adjustment of the tilt angle should be started with
comparatively small changes to the tilt angle so as to
avoid a sudden deterioration of SINR values associated with
single terminals that are situated at the borders of the
cell or sector served by the antenna considered for tilt
angle adjustment.
However, if the distance distribution e.g. has a peak at
intermediate distance values, which means that numerous
terminals are located within a moderate distance to the
base station, it may be concluded that performing the
adjustment of the tilt angle may be started with
comparatively large changes to the tilt angle since only a
substantial alteration of the tilt angle will affect those
numerous terminals.
Advantageously, it is also possible to alter the amount by
which the tilt angle is changed during the step of
adjusting from iteration to iteration so as to account for
the quality measure converging to a desired value. I.e.,
the amount by which the tilt angle is changed may be
reduced from a first iteration to a next iteration.
As a further example, the amount by which the tilt angle is
changed during the step of adjusting may also be chosen
depending on a difference of the SINR as obtained prior to
the last step of adjusting and the SINR as obtained after
the last step of adjusting.
Random events or pseudo-random events may also form a basis
on which the amount by which the tilt angle is changed may
be determined. For instance, true random events as
detectable by the base station are the time of arrival of a
new terminal or a duration of a data connection with a
terminal, whereas pseudo- random events may be generated by
processing means of the base station in a per se known
manner. The consideration of random events or pseudo-random
events may e.g. be useful for performing statistical
optimization algorithms, which, according to a further
embodiment, may also be employed to determine an optimum
tilt angle according to a predetermined target function or
fitness function, such as e.g. an average SINR of all
terminals served by the considered antenna of the base
station.
According to a further advantageous embodiment, said
quality measure, e.g. the SINR, on which the adjustment of
the tilt angle according to the embodiments depends, is
determined based on feedback information received from at
least one terminal which is served by the base station via
said antenna. For instance, a terminal served by the base
station may directly forward an SINR value it has
determined for a downlink data transmission from the base
station.
According to a further advantageous embodiment, the base
station comprises a plurality of antennas, each of which
serves a specific spatial sector, such as e.g. a sector of
about 120 ° , and said step of adjusting is only performed
for one antenna or an associated sector, respectively, at a
time thus avoiding a simultaneous tuning of tilt angles for
neighboring sectors.
According to a further advantageous embodiment, said step
of adjusting is repeated according to at least one of: a
predetermined schedule, operational parameters of said base
station or of a neighboring base station, a random event.
I.e., the adjustment process according to the embodiments,
which itself may comprise various iterations, can be
performed periodically, such as twice an hour or the like.
It is also possible to perform the adjustment process
according to the embodiments randomly or in such cases
where a predetermined number of terminals served by the
base station's antenna is exceeded. A base station may also
consider operational parameters of a neighboring base
station for the conduction of the adjustment process.
A further solution to the object of the present invention
is given by a base station according to claim 9 . The base
station is configured to adjust a tilt angle of the antenna
and/or of a beam pattern of said antenna depending on a
quality measure which characterizes the quality of a signal
transmission associated with said antenna.
Further advantageous embodiments of the invention are given
in the dependent claims.
Brief Description of the Figures
Further features, aspects and advantages of the present
invention are given in the following detailed description
with reference to the drawings in which:
Figure 1 depicts a simplified block diagram of a base
station according to an embodiment,
Figure 2 depicts a simplified flow-chart of a method of
operating a base station according to an
embodiment , and
Figure 3 depicts a simplified flow-chart of a method of
operating a base station according to a further
embodiment .
Description of the Embodiments
Figure 1 depicts a simplified block diagram of a base
station 100 of a cellular communications network. The base
station 100 may serve a number of terminals (not shown)
such as mobile user terminals by maintaining respective
data communication sessions in a per se known manner. For
instance, the base station 100 may operate according to at
least one of the following standards: GSM (Global System
for Mobile Communications) , UMTS (Universal Mobile
Telecommunications System) , LTE (Long Term Evolution) ,
WiMax (Worldwide Interoperability for Microwave Access) ,
WLAN (Wireless Local Area Network) .
The base station 100 comprises an antenna 110, a
characteristic beam pattern of which is symbolized by the
dashed shape 11 . According to an embodiment, the antenna
110 may be electrically controlled to reconfigure its beam
pattern ill or at least a direction of the main lobe of
beam pattern 111 in which the main lobe's axis 112 extends.
I.e., the tilt angle Gof the antenna 110, more precisely
of its main lobe 112, which - as can be gathered from
Figure 1 - is defined as the angle between the main lobe's
axis 112 and a virtual plane P that is parallel to ground,
can be electrically controlled. This is e.g. accomplished
by the processing means 120 which also control the basic
operation of the base station 100. Moreover, the processing
means 120 are also configured to perform the method
according to the embodiments explained below with reference
to Figure 2 and 3 .
According to a further embodiment, the base station 100 may
comprise an antenna 110 a beam pattern of which cannot be
controlled electronically. In this case, the tilt angle 
is influenced by rotating the antenna 110 around an axis
which is e.g. perpendicular to the drawing plane of Figure
1 . For this purpose, an electromechanical actuator can be
provided in the support of the antenna 110, wherein said
actuator is also controlled by the processing means 120 of
the base station 100. A combination of an electrically
controllable antenna 110 (regarding tilt angle ) with a
mechanical drive is also possible.
In contrast to conventional base stations, the antennas of
which are mounted with a predetermined and fixed tilt angle
during an installation of the base station, the base
station 100 according to an embodiment is configured to
adjust the tilt angle of the antenna 110 and/or of its
beam pattern 111, respectively, depending on a quality
measure which characterizes the quality of a signal
transmission associated with said antenna 110.
Particularly, according to an embodiment, the tilt angle
adjustment is performed dynamically, i.e. without
interrupting an ongoing data transmission via the antenna
110 the tilt angle of which is adjusted.
Thus, base station 100 can dynamically adapt a radio
coverage area defined by the beam pattern 111 to ongoing
communications processes with the terminals (not shown)
that are being served by the base station 100. This way, a
quality of data transmission between the base station 100
and its terminals may potentially be improved.
According to a preferred embodiment, a signal to noise plus
interference ratio, SINR, is used by the base station 100
as a quality measure to assess the quality of a signal
transmission. Of course, other suitable parameters such as
a bit error rate, BER, or CQ (channel quality indicator)
reports as known from LTE systems may also be used to
characterize the quality of a signal transmission between
the base station 100 and a terminal.
For instance, the base station 100 may, preferably
periodically, receive feedback information from a connected
mobile terminal, said feedback information representing an
SINR value as determined by the terminal for a process of
receiving data from said base station 100. Based on this
feedback information, the processing means 120 of the base
station 100 may assess the quality of signal transmission
in a downlink direction to the terminal (s) .
The flow-chart of figure 2 depicts a preferred embodiment
of a method of operating the base station 100. In a first
step 200, the tilt angle is adjusted by a predetermined
amount starting from an initial tilt angle value that may
e.g. be defined by the processing means 120 upon
initialization of the base station 100.
After adjusting the tilt angle in step 200, base station
100, more precisely the processing means 120, in step 210
determine a S value as a quality measure characterizing
downlink transmission quality at least for a downlink
channel with a specific terminal. It is also possible to
determine the SINR or another suitable quality measure
representing downlink transmission quality to a plurality
of terminals or to determine an average quality measure
such as an average SINR for a plurality of terminals
currently served by the base station 100.
n step 220, the processing means 120 of the base station
100 evaluate whether said quality measure, which has been
obtained in preceding step 210, has increased. The increase
or a decrease of the quality measure may be determined by
comparing the value of said quality measure obtained after
said adjustment 200, i.e. during step 210, with a
corresponding quality measure value that has been obtained
prior to adjusting 200.
This way, the base station 100 may precisely assess whether
the adjustment of the tilt angle performed in step 200
yielded an improvement regarding signal transmission
quality.
If not, i.e. if the SINR obtained after adjusting 200 has
not increased with respect to the old tilt angle that was
set prior to adjusting 200, the steps 200, 210, 220 may be
repeated for a predetermined number of iterations. n the
course of these iterations, it is also possible to modify
the amount by which the tilt angle is adjusted within
step 200, as well as the direction of adjustment, i.e.
whether the current tilt angle is increased or whether it
is decreased by said amount within step 200.
According to an embodiment, starting from its initial
value, the tilt angle may e.g. be altered by 2 % of its
overall setting range per step of adjusting. Any other
adjustment steps that can be implemented by the given
adjustment mechanism (electrical beam forming or
mechanically driving the antenna 110) may also be applied.
Preferably, the iterative execution of steps 200, 210, 220
is terminated if a predetermined maximum number of
iterations is reached. Alternatively, the iterations may
also be terminated if, by means of the evaluation in step
220, it is concluded that a significant improvement
regarding SINR has been achieved.
Of course, according to a further particularly preferred
embodiment, the steps 200, 210, 220 may be repeated
continuously, i.e. without terminating after a specific
number of iterations. This variant advantageously accounts
for the usually highly dynamic structure of a cellular
communications network with many terminals roaming around.
By continuously repeating the method according to the
embodiments, it is ensured that the base station always
tries to set an optimum tilt angle for the terminals
currently served, i.e. a continuous improvement and
adaptation of tilt angle is enabled.
Figure 3 depicts a flow-chart of a further embodiment of a
method of operating the base station 100 (Figure 1 ) .
In a first step 300, a current value of the SINR as
determined for a downlink connection to a specific terminal
is obtained by processing means 120 which evaluate
corresponding feedback information received at the base
station 100 from its terminals. Alternatively or in
addition, an average SINR value may also be considered
which e.g. represents a downlink transmission quality
averaged over a plurality of terminals.
n step 310, the processing means 120 determine, by which
amount the current tilt angle of the antenna 110 is to
be adjusted. Additionally, in step 310, the direction of
adjustment of the current tilt angle may also be
determined, i.e. whether to increase or decrease the
current tilt angle by the amount .
According to a further advantageous embodiment ,the amount
by which the tilt angle is increased or decreased in the
following step of adjusting 320 is determined based on at
least one of: operational parameters of said base station
100, a current number of iterations, the maximum number of
iterations, a current value of said quality measure, a
value of said quality measure obtained prior to a previous
step of adjusting, a random event or a pseudo-random event.
Taking into consideration operational parameters of the
base station 100 such as
- a number of terminals/users currently served,
- an average signal to noise plus interference ratio,
SINR, for some or all user connections / terminals
currently served,
- a distribution of distances between the terminals
which are currently served by the base station and the
base station
advantageously enables to precisely adapt the adjustment
320 to a specific operating scenario of the base station
100.
E.g., if a comparatively high number of terminals is served
and if the their distance distribution is rather flat, i.e.
if there are many terminals at many different distances to
the base station 100, it may be concluded that performing
the adjustment of the tilt angle should be started with
comparatively small changes to the tilt angle so as to
avoid a sudden deterioration of SINR values associated with
single terminals that are situated at the borders of the
cell or sector served by the antenna 110 considered for
tilt angle adjustment.
However, if the distance distribution e.g. has a peak at
intermediate distance values, which means that numerous
terminals are located within a moderate distance to the
base station 100, it may be concluded that performing the
adjustment of the tilt angle may be started with
comparatively large changes to the tilt angle since
only a substantial alteration of the tilt angle might
affect those numerous terminals, i.e. lead to SINR
improvement .
Advantageously, it is also possible to alter the amount 
by which the tilt angle is changed during the step of
adjusting 320 from iteration to iteration so as to account
for the quality measure converging to a desired value.
I.e., the amount by which the tilt angle is changed
may be reduced from a first iteration to a next iteration.
As a further example, the amount by which the tilt angle
is changed during the step of adjusting 320 may also be
chosen depending on a difference of the S R as obtained
prior to the last step of adjusting 320 and the SINR as
obtained after the last step of adjusting 320.
Random events or pseudo-random events may also form a basis
on which the amount by which the tilt angle is changed
may be determined. For instance, true random events as
detectable by the base station 100 are the time of arrival
of a new terminal or a duration of a data connection with a
terminal, whereas pseudo- random events may be generated by
its processing means 120 in a per se known manner. The
consideration of random events or pseudo- random events may
e.g. be useful for performing statistical optimization
algorithms, which, according to a further embodiment, may
also be employed to determine an optimum tilt angle
according to a predetermined target function or fitness
function, such as e.g. an average SINR of all terminals
served by the considered antenna 110 of the base station
100.
After the step 310 of determining the amount by which
the tilt angle is to be adjusted, this adjustment is
applied in subsequent step 320 by the processing means 120
effecting a respective control of the antenna's beam
pattern or a mechanical drive, respectively.
In step 330, the current SINR, i.e. as obtained as a result
of the adjustment of step 320, is determined and compared
with the old SINR value as obtained in step 300 prior to
the adjustment, cf . step 340. If the evaluation of step 340
yields that the current SINR exceeds the old SINR, the
process branches to step 320 for a further adjustment of
the tilt angle in the same direction. Alternatively, if
it is desired to alter the specific amount by which the
tilt angle is to be adjusted in future, the process may
also branch to step 310 instead of step 320, whereby a new
determination of the adjustment parameter is enabled,
cf . the dashed arrow from block 340 to block 310.
However, if the evaluation of step 340 yields that the
current SINR is less or equal than the old SINR, the
process branches to step 350, wherein the adjustment
strategy is reviewed. For instance, in step 350, the
direction of adjustment, i.e. the sign of the adjustment
parameter may be changed. After that, the process may
continue with step 310 to determine an absolute value of
the adjustment parameter . After that, in step 320, a
further adjustment of the tilt angle is effected.
Depending on the specific optimization strategy for the
tilt angle , of course, it is possible to perform further
changes to the adjustment parameter within step 350. It
is also possible to dynamically change the optimization
strategy within step 350, e.g. to account for a change in
the operating conditions of base station 100 or the like.
According to a further embodiment, the adjustment processes
as exemplar ily explained above with respect to Figure 2 and
3 above may also be repeated according to a predetermined
schedule stored to the processing means 120 or defined by a
central office of the network the base station 100 belongs
to.
The application of the adjustment processes as exemplar ly
explained above with respect to Figure 2 and 3 above may
also be triggered by operating parameters of the base
station 100. I.e., whenever a number of concurrently served
terminals exceeds or falls below a predetermined threshold,
the base station 100 may perform steps 200 to 220 or steps
300 to 350 or a combination thereof.
It is also possible for the base station 100 to perform the
adjustment processes as exemplar ily explained above with
respect to Figure 2 and 3 depending on operational
parameters of a neighbouring base station, i.e. a load of
said neighbouring base station and the like.
According to a particularly preferred embodiment, wherein
an average S of a plurality of terminals is used as a
quality measure for steps 220, 340, the adjustment
processes as exemplarily explained above with respect to
Figure 2 and 3 are only conducted if base station 100 has
collected a significant amount of SINR data from the
considered terminals so as to be able to precisely judge
whether an adjustment of the tilt angle results in an
improvement of transmission quality.
The inventive principle of tilt angle adjustment can also
be extended to base stations 100 that comprise more than
one antenna 110, wherein each of the plurality of antennas
serves a different spatial sector with its radio coverage.
In these embodiments, said step of adjusting 200 and the
following steps 210, 220 are preferably only performed for
one antenna 110 or an associated sector, respectively, at a
time.
The embodiments explained above are not limited to base
stations 100 of cellular communications networks. The
inventive principle of tilt angle adjustment may rather be
applied to any base station having at least one antenna a
tilt angle of which (or a tilt angle of a main lobe ill of
a corresponding beam pattern) may be controlled, e.g.
electrically or on an electromechanical basis. Typically,
the principle may be applied with GSM-, UMTS- , LTE-, and
WiMAX- base stations.
Advantageously, the application of the inventive principle
reduces an effort required for network planning and
increases network robustness. Moreover, since the base
station 100 or its processing means 120 can apply the
inventive principle, a decentralized adaptation of the
radio access network to changing environments and operating
conditions is enabled.
The description and drawings merely illustrate the
principles of the invention. It will thus be appreciated
that those skilled in the art will be able to devise
various arrangements that, although not explicitly
described or shown herein, embody the principles of the
invention and are included within its spirit and scope.
Furthermore, all examples recited herein are principally
intended expressly to be only for pedagogical purposes to
aid the reader in understanding the principles of the
invention and the concepts contributed by the inventor (s)
to furthering the art, and are to be construed as being
without limitation to such specifically recited examples
and conditions. Moreover, all statements herein reciting
principles, aspects, and embodiments of the invention, as
well as specific examples thereof, are intended to
encompass equivalents thereof.
The functions of the various elements shown in the Figures,
including any functional blocks labelled as 'processors',
may be provided through the use of dedicated hardware as
well as hardware capable of executing software in
association with appropriate software. When provided by a
processor, the functions may be provided by a single
dedicated processor, by a single shared processor, or by a
plurality of individual processors, some of which may be
shared. Moreover, explicit use of the term 'processor' or
'controller' should not be construed to refer exclusively
to hardware capable of executing software, and may
implicitly include, without limitation, digital signal
processor (DSP) hardware, network processor, application
specific integrated circuit (ASIC) , field programmable gate
array (FPGA) , read only memory (ROM) for storing software,
random access memory (RAM), and non volatile storage. Other
hardware, conventional and/or custom, may also be included.
Similarly, any switches shown in the FIGS, are conceptual
only. Their function may be carried out through the
operation of program logic, through dedicated logic,
through the interaction of program control and dedicated
logic, or even manually, the particular technique being
selectable by the implementer as more specifically
understood from the context.
Claims
1 . Method of operating a base station (100) for a
cellular communications network, wherein said base
station (100) comprises at least one antenna (110) ,
said method comprising a step of adjusting (200) a
tilt angle () of the antenna (110) and/or of a beam
pattern of said antenna, wherein said step of
adjusting (200) is performed depending on a quality
measure which characterizes the quality of a signal
transmission associated with said antenna (110) .
2 . Method according to claim 1 , comprising the following
steps :
- adjusting (200) the tilt angle () by increasing
or decreasing it by a predetermined amount (),
determining (210) a value of said quality measure
after said adjustment (200) ,
- evaluating (220) , whether said quality measure
has increased.
3 . Method according to claim 2 , wherein said steps of
adjusting (200) , determining (210) and evaluating
(220) are repeated for a predetermined maximum number
of iterations or until a predetermined increase of
said quality measure has been detected.
4 . Method according to claim 3 , wherein the amount ()
by which the tilt angle () is increased or decreased
in said step of adjusting (200) is determined (310)
based on at least one of: operational parameters of
said base station (100) , a current number of
iterations, the maximum number of iterations, a
current value of said quality measure, a value of said
quality measure obtained prior to a previous step of
adjusting, a random event or a pseudo- random event.
ethod according to one of the preceding claims,
wherein said quality measure is determined based on
feedback information received from at least one
terminal which is served by said base station (100)
via said antenna (110) .
ethod according to one of the preceding claims,
wherein said base station (100) comprises a plurality
of antennas (110) , each of which serves a specific
sector, and wherein said step o f adjusting (200) is
only performed for one antenna (110) or an associated
sector, respectively, at a time.
ethod according to one of the preceding claims,
wherein said step of adjusting (200) is repeated
according to at least one of: a predetermined
schedule, operational parameters of said base station
(100) or of a neighbouring base station, a random
event.
ethod according to one of the preceding claims,
wherein said step of adjusting (200) is performed
dynamically, particularly without interrupting an
ongoing data transmission via said antenna (110) .
a se station (100) for a cellular communications
network, wherein said base station (100) comprises at
least one antenna (110) , and wherein the base station
(100) is configured to adjust (200) a tilt angle ()
of the antenna (110) and/or of a beam pattern of said
antenna depending on a quality measure which
characterizes the quality of a signal transmission
associated with said antenna (110) .
a se station (100) according to claim 9 , wherein said
base station (100) is configured to
- adjust (200) the tilt angle () by increasing or
decreasing it by a predetermined amount (),
- determine (210) a value of said quality measure
after said adjustment (200) ,
- evaluate (220) , whether said quality measure has
increased.
a se station (100) according to claim 10, wherein said
base station (100) is configured to repeat said steps
of adjusting (200) , determining (210) and evaluating
(220) for a predetermined maximum number of iterations
or until a predetermined increase of said quality
measure has been detected.
a se station (100) according to one of the claims 10
to 11, wherein said base station (100) is configured
to determine the amount () by which the tilt angle
() is increased or decreased in said step of
adjusting (200) based on at least one of: operational
parameters of said base station (100) , a current
number of iterations, the maximum number of
iterations, a current value of said quality measure, a
value of said quality measure obtained prior to a
previous step of adjusting, a random event or a
pseudo- random event.
a se station (100) according to one of the claims 9 to
12, wherein said base station (100) is configured to
determine said quality measure based on feedback
information received from at least one terminal which
is served by said base station (100) via said antenna
(110) .
a se station (100) according to one of the claims 9 to
13, wherein said base station (100) comprises a
plurality of antennas (110) , each of which serves a
specific sector, wherein said base station (100) is
configured to perform said step of adjusting (200)
only for one antenna (110) or an associated sector,
respectively, at a time.
a se station (100) according to one of the claims 9 to
13, wherein said base station (100) is configured to
perform said step of adjusting (200) dynamically,
particularly without interrupting an ongoing data
transmission via said antenna (110) .