METHOD OF ASSIGNING RADIO RESOURCES TO MOBILE TERMINALS
BASED ON THE RELATIVE DISTANCE BETWEEN SAID MOBILE
TERMINALS AND A BASE STATION
Specification
Field o f the Invention
The invention relates to a method o f operating a base
station for a cellular communications network. The
invention further relates to a base station for a cellular
communications network.
Background
n o . st xon s fo C o v t io
networks comprise antenna systems having one o r more
antennas which are mounted and adjusted during an
installation o f the base station in the field.
Particularly, a tilt angle between a main beam direction o f
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, o r it is adjusted electronically in a longterm
scale, e.g. adapting to the traffic load during a day.
However, this conventional installation generally applies
the same tilt angle to all terminals in the cell.
There is a need to provide a more sophisticated base
station and method o f operating a base station which offer
increased flexibility regarding the operational
characteristics o f the base station.
Summary-
According to the present invention, regarding the above
mentioned method of operating a base station, this object
is achieved by: the base station determining at least two
terminals which are served by the base station and which
are scheduled for the same primary radio resource, the base
station assigning individual portions of a secondary radio
resource, which is different from said primary radio
resource, to said at least two terminals depending on a
parameter which characterizes a vertical angle between a
virtual horizontal plane associated with said base station
and a specific one of said terminals.
The vertical angle can be interpreted as an optimum
downtilt or tilt angle which, when implemented by the base
station, leads to optimum transmission conditions with
respect to a specific terminal because a main lobe of a
beam pattern of the base station's antenna would then be
directed at said specific terminal. By assigning the second
radio resource to said at least two terminals depending on
a parameter which characterizes said vertical angle, a
particularly efficient reduction of interference between
neighboring cells may be achieved.
According to an embodiment, the vertical angle may e.g.
correspond with a direction of the most distinctive
propagation path (i.e., the path which offers a maximum
received signal power) between the base station and the
terminal. It is to be noted that, especially due to the
effect of multipath propagation, a direction between the
base station and the terminal as characterized by the
vertical angle may differ from an angle that corresponds
with a "direct line of sight" - type direction, because,
due to reflections and other effects associated with
multipath propagation, the "direct line of sight" - type
direction may not necessarily be associated with the most
distinctive propagation path (i.e., the path which offers a
maximum received signal power) .
Advantageously, the method according to the embodiments
does not require assessing feedback information or
transmission quality information . Further, the method
according to the embodiments does not require any interbase
station communication, e.g. between neighbouring base
stations .
According to a preferred embodiment, said base station
comprises an antenna a tilt angle of which can be
controlled, wherein said base station uses individual tilt
angles for single terminals and/or groups of terminals
depending on said parameter which characterizes said
vertical angle. Thus, individual terminals may optimally be
served by the base station by adapting its antenna beam
pattern to the respective terminals. However, if the
antenna system is capable of implementing only
comparatively few different values of the tilt angle, the
terminals under consideration by the base station (i.e.
tho S t . S h 3 . S du d o t S3 €
radio resource) are grouped into various terminal groups
according to their respective vertical angles. I.e.,
several terminals having similar vertical angles may be put
into one terminal group which is associated with one of the
discrete tilt angles that may be used by the base station.
According to a particularly preferred embodiment, said
primary radio resource is time, preferably transmission
time slots, and said secondary radio resource is frequency,
preferably frequency subchannels. For instance, cellular
communications networks according to the LTE standard
provide using transmission time slots and frequency
subchannels as primary and secondary radio resources.
However, the present embodiments are not limited to this
pa tic lar co b xn a ion of radi O resources * For instance
besides allocating frequency resources (such as e.g.
frequency subchannels) to users/ terminals that are served
during the same time slot as described above, the principle
according to the embodiments can generally also be applied
by allocating different time resources (i.e., time slots)
to users/terminals that are served on the same frequency
resource (i.e., in this case, frequency is considered as
the ri ry radi o reS O U ) .
Apart from time and frequency, preferably orthogonal, codes
may also considered as radi o resource in the sense of
the present invention. Thus, a first radio resource may be
frequency, and a second radio resource may be a specific
code, and the like. In this case, the radio resource "code"
is assigned to the various terminals served on the same
frequency resources depending on the vertical angle.
According to a further preferred embodiment, said base
station assigns a first number of, preferably adjacent,
frequency subchannels to a first one of said at least two
terminals, and said base station assigns a second number
of, preferably adjacent, frequency subchannels to a second
one of said at least two terminals. Within LTE systems, for
example, resource blocks (RB ) may be used to represent said
frequency subchannels according to the present embodiment.
The first and/or second number of frequency subchannels,
are not necessarily adjacent to each other. Other types of
assignment, i.e. comprising non-adjacent subchannels, are
also possible.
According to a further preferred embodiment, said base
station sorts said at least two terminals depending on said
parameter which characterizes said vertical angle
associated with said terminals to obtain a sorted list of
terminals, and said base station assigns said portions of
said secondary radio resource depending on said sorted list
of terminals, which represents a particularly efficient
assignment technique.
Generally, said parameter which characterizes said vertical
angle may e.g. be estimated and/or approximated, e.g. by
determining a relative distance between the base station
and the specific terminal (using signal strength
measurements, delay measurements, and the like) .
Destination of arrival estimation techniques may also be
employed.
According to a further preferred embodiment, said step of
3.S S S Z O C i .O XT SOU. i S Caccording
to a predetermined scheme, particularly
independent of feedback information that characterizes an
actual quality of transmission between the base station and
individual terminals. Thus, the embodiments represent a
very simple, decentralized measure to distribute secondary
radio resources to different terminals in the sense of
decreasing an overall interference between neighbouring
cells. It is particularly advantageous, if neighboring base
stations employ different variants of the scheme according
to the embodiments so as e.g. not to assign the same
secondary radio resources (e.g., frequency bands) to those
of their terminals which are in a cell border region, i.e.
close to the neighboring base station. This may e.g. be
ensured when deploying the base stations by providing
different "start values" to the inventive radio resource
assignment scheme such that neighboring base stations do
not employ identical variants of the scheme.
According to a further preferred embodiment, said
predetermined scheme associates values and/or value ranges
of said parameter which characterizes a vertical angle with
respective portions of said secondary radio resources.
Generally, an 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 S tO ell IT t ¾ t 3 . 3 X S O f TTl
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.
Third, antennas with a limited number of adjustable
downtilts, realized by different feeder networks within the
antenna for the antenna elements, and selection of the
appropriate one by mechanically or electronically switching
available feeder networks, may also be employed
for tilt angle adjustment according to an embodiment.
Of course, a combination of the aforementioned methods may
also be employed for tilt angle adjustment.
A further solution to the object of the present invention
is given by a base station according to claim 9 . 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
communications scenario according to an
embodiment,
Figure 2 depicts a simplified block diagram of a base
station according to an embodiment,
Figure 3 schematically depicts frequency subchannels as
employed by a method according to the
embodiment s,
Figure 4 depicts a simplified flow chart of a method
according to the embodiments, and
Figure 5a,
5b, 5c depict different resource assignment schemes
according to an embodiment.
Description of the Embodiments
Figure 1 depicts a simplified block diagram of a
communications scenario according to an embodiment.
A base station 100 o f a cellular communications network is
depicted. The base station 100 may serve a number o f
terminals 10, 11, 12 b y providing radio coverage in form o f
a radio cell 110 in a per se known manner. For instance,
the base station 100 may operate according to a t least one
o f the following standards: GSM (Global System for Mobile
Communications) , UMTS (Universal Mobile Telecommunications
System) , LTE (Long Term Evolution) , iM ax (Worldwide
Interoperability for Microwave Access) , WLAN (Wireless
Local Area Network) . For the further exemplary
OXp . . O t S 3 t -t O .S O t t O 100 .
LTE-compatible base station.
Further neighbouring radio cells 12 0 , 13 0 o f the
communications network are also depicted by Fig. 1 which
may correspondingly b e served b y further base stations that
are not depicted in Fig. 1 for the sake o f clarity.
However, the further base stations which provide the
f i x x x i o 1 0 130 b c o ~ lo tod
with the first base station 100.
Generally, even further base stations and their associated
cells may also b e provided within the network. Those
further devices and cells are only indicated b y dashed
lines within Fig. 1 and form a generally hexagonal cell
pattern for the communications network together with the
cells 110, 120, 130.
A s can b e gathered from Fig. 2 , the base station 100
comprises an antenna 102, a characteristic beam pattern o f
which is symbolized b y the elliptical shape presently
directed to the terminal 12. I.e., the main lobe o f the
beam pattern is currently aligned with the direction losi 2
o f the most distinctive propagation path (i.e., the path
which offers a maximum received signal power) between the
base station 100 and the terminal 12. An associated
vertical angle 2 between a virtual horizontal plane P
associated with said base station 100 and said terminal 12,
is obtained. Obviously, the vertical angle 2 depends,
inter alia, on a distance between base station 100 and
terminal 12. Moreover, a vertical position of the terminal
12, of course, may also influence the vertical angle 2 .
Generally, the direction I0S 12 associated with the vertical
angle 12 does not necessarily represent a direction of a
"line of sight" between the devices 100, 12, because due to
effects such as multipath propagation, the most distinctive
propagation path (i.e., the path which offers a maximum
received signal power) between the base station 100 and the
terminal 12 may require a vertical angle different from
a direction of the "line of sight" between the devices 100,
12. Presently, for illustration and simplification
purposes, however, Figure 2 depicts a situation where the
vertical angle 2 and a direction of the "line of sight"
between base station 100 and terminal 12 are roughly equal
to each other.
For instance, the further terminal 10, which is presently
further away from the base station 100 (also cf. Fig. 1),
correspondingly has another associated vertical angle 0 <
Generally, the vertical angle Q 12 associated with a
terminal 12 corresponds with an optimum downtilt angle for
the antenna 102 . I.e., if the base station 100 controls its
antenna pattern to assume the respective vertical angle 2
as downtilt angle, optimum communications conditions for
communications with the specific terminal 12 are ensured .
According to a preferred embodiment, the base station 100
is configured to determine 200 (cf . the flow chart of Fig.
4 ) at least two terminals 10, 11, 12 which are served by
the base station 100 and which are scheduled for the same
primary radio resource, and to assign 210 (Fig. 4 )
individual portions of a secondary radio resource, which is
different from said primary radio resource, to said at
least two terminals 10, 11, 12 depending on a parameter
which characterizes said vertical angle 2,.. of the
respective terminal 10, 11, 12.
In the exemplary context of an LTE system, the primary
radio resource is time, preferably transmission time slots
according to LTE standard, and said secondary radio
resource is frequency, preferably frequency subchannels
according to LTE standard.
I.e., in the first step 200 (Fig. 4), the base station
determines, which terminals 10, 11, 12 (Fig. 1 ) are
scheduled for e.g. the same transmission time slot
(= "primary radio resource"). Then, in the second step 210
(Fig. 4 ) , the base station assigns individual portions of a
secondary radio resource, i.e. frequency subchannels, to
said terminals 10, 11, 12 depending on a specific vertical
angle 2 , .. of the terminals.
For instance, in step 200, the base station 100 determines
that the two terminals 10, 11 are scheduled for a same
transmission time slot. Thus, the assignment of the
secondary radio resource, i.e. frequency subchannels, is
performed as follows:
The base station 100 determines, which of the terminals 10,
11 has the smallest vertical angle. Presently, terminal 10
has the smallest vertical angle 0, since it is at a
border of the radio cell 110 (Fig. 1 ) . Thus, the further
terminal 11 is determined to have a larger vertical angle.
Depending on this sequence of the terminals 10, 11
regarding their vertical angles, the base station 100
assigns frequency subchannels to the terminals for a future
data communications which is performed on the same primary
radio resource, i.e., transmission time slot. For instance,
a first group Ci of frequency subchannels, cf. Fig. 3 , is
assigned to the terminal 10, and a second group C j of
frequency subchannels , cf . F . 3 , s assigned to the
terminal 11. Of course, the number of frequency subchannels
within the respective group Ci, C j is not necessarily the
same as in the other groups assigned to other terminals. A s
per se known, the number of assigned frequency subchannels
may actually depend on a desired data rate and the like.
The above explained resource assignment depending on the
vertical angle of the terminals 10, 11 is particularly
efficient and requires no coordination of the base station
100 with neighbour base stations in order decrease
X .X-Lt f C -
Moreover, according to the present embodiment, the base
station 100 is not required to alter its tilt angle at all.
It may rather "only" perform the inventive assignment of
the secondary radio resource depending on the vertical
angle that results from the relative position between base
station and the terminals, i.e. without providing
individual tilt angles for the respective terminals.
However, according to a further advantageous embodiment,
the base station 100 may also adapt its tilt angle,
preferably on a per- terminal basis. With this embodiment,
in addition to the above explained assignment of
subchannels according to Fig. 3 the base station 100
additionally provides specific tilt angles for the
transmissions with the terminals 10, 11, wherein the tilt
angles are chosen to be identical or close to the actual
vertical angles resulting from the positions of the
terminals.
According to an embodiment, said base station 100 is
configured to use individual tilt angles for single
terminals 10, 11, 12. This can e.g. be done, if the base
station comprises an electric tilt angle control which
allows to control the tilt angle within a wide range of
tilt angle values.
However, if the base station 100 can only provide for
comparatively few different tilt angles, groups of
terminals which have similar vertical angles may be served
with the same tilt angle.
According to an embodiment, said base station 100 is
configured to sort said at least two terminals 10, 11, 12
depending on said parameter which characterizes said
vertical angle 12 , .. associated with said terminals 10,
11, 12 to obtain a sorted list of terminals 10, 11, 12, and
to assign said portions of said secondary radio resource
depending on said sorted list of terminals 10, 11, 12.
I.e., each terminal 10, 11, 12 is sorted according to its
associated vertical angle 0, •., .
Generally, said parameter which characterizes said vertical
angle may e.g. be estimated and/or approximated, e.g. by
determining a relative distance between the base station
100 and the specific terminal 10 (using signal strength
measurements, delay measurements, and the like) .
Destination of arrival estimation techniques may also be
employed .
After the sorting step, the assignment of the secondary
radio resource is performed.
According to a further preferred embodiment, said step 210
of assigning said secondary radio resource is performed
according to a predetermined scheme, particularly
independent of feedback information that characterizes an
actual quality of transmission between the base station 100
and individual terminals 10, 11, 12. Thus, the embodiments
represent a very simple, decentralized measure to
distribute secondary radio resources to different terminals
10, 11, 12 in the sense of decreasing an overall
interference between neighbouring cells.
It is p i ¾Q - f f
stations employ different variants of the scheme according
to the embodiments so as e.g. not to assign the same
secondary radio resources (e.g., frequency bands) to those
of their terminals which are in a cell border region, i.e.
close to the neighboring base station. This may e.g. be
ensured when deploying the base stations by providing
different "start values" to the inventive radio resource
assignment scheme such that neighboring base stations do
not employ identical variants of the scheme.
For example, considering that the base station 100 (Fig. 1 )
is co-located with two further base stations (not shown) ,
each one of the three neighboring radio cells 110, 12 0 , 13 0
is served by one of said base stations. If all three base
stations adhere to the method according to the embodiments,
they can assign secondary radio resources to their
terminals according to respective vertical angles associate
with the terminals. Generally, this assigning step will be
performed individually by each base station, i.e.
separately and independently for each cell. However, to
further reduce interference, according to an embodiment,
each of the three considered base stations applies a
slightly different variant of the inventive assigning
scheme.
For instance, the first base station 100 employs the table
depicted by Fig. 5a to assign specific resource blocks
(i.e., frequency subchannels of the LTE system) as a
secondary resource to its terminals 10, 11, 12. From the
table of Fig. 5a it can be gathered that terminals with a
vertical angle ranging from a value 0 to a value are
assigned the resource blocks RB0 to RB16 (assuming a 10 MHz
bandwidth LTE system which thus comprises a an overall
range of resource blocks from RB0 to RB50) . Terminals with
a vertical angle ranging from a value to a value 2 are
assigned the resource blocks RB17 to RB32 . Terminals with a
vertical angle ranging from a value 2 to a value 3 are
assigned the resource blocks RB33 to RB50.
For instance, the first terminal 10 is assigned the
secondary resources RB0..RB16, the second terminal 11 is
assigned the secondary resources RB17..RB32, and the third
terminal 12 is assigned the secondary resources RB33..RB50
within the radio cell 110 of the first base station 100.
The second base station (not shown) , which provides the
neighboring radio cell 120 for the terminals 20, 21, 22,
however, uses a slightly different variant of the
assignment scheme, namely the table according to Fig. 5b
instead of Fig. 5a. As can be seen, the second table of
Fig. 5b is a shifted variant of the table of Fig. 5a, with
respect to the resource blocks , since it starts with RBI 7
to RB32 for the smallest vertical angle.
Thus, in the second radio cell 120, the first terminal 20
is assigned the secondary resources RB17..RB32, the second
terminal 21 is assigned the secondary resources RB33..RB50,
and the third terminal 22 is assigned the secondary
resources RB0..RB16 by its base station (not shown).
Likewise, the third base station (not shown) , which is also
co-located with the first base station 100, will assign
frequency resources according to the table depicted by Fig.
5c to its terminals 30, 31, 32. Thus, it is advantageously
ensured that inter-cell interference is reduced.
n effect, because the vertical angle usually correlates
with a distance of a terminal to its base station, the
above explained assignment schemes ensure that a distancedependent
distribution / assignment of secondary radio
resources is performed within a cell. By employing
permutations of said assignment schemes as exemplified by
Fig. 5a to 5c between neighboring base stations, it is
possible to reduce interference without requiring
communication of said base stations related to resource
assignment .
The resource assignment according to the embodiments may
rather be performed individually by each base station 100,
independent of other base station. To ensure that
neighboring base stations each start with different
secondary resources values for the assignment, e.g. an
offset within a respective table (Fig. 5a) may be employed
which depends on an identifier of the specific base station
100 .
According to a particularly preferred embodiment, said
primary radio resource is time, preferably transmission
time slots, and said secondary radio resource is frequency,
preferably frequency subchannels, as already explained
above. For instance, cellular communications networks
according to the LTE standard provide using transmission
time slots and frequency subchannels as primary and
secondary radio resources. However, the present embodiments
are not limited to this particular combination of radio
resources. For instance, besides allocating frequency
resources (such as e.g. frequency subchannels) to
users/terminals that are served during the same time slot
as described above, the principle according to the
embodiments can generally also be applied by allocating
different t
users/terminals that are served on the same frequency
resource (i.e., in this case, frequency is considered as
the primary radio resource) .
Apart from time and frequency, preferably orthogonal, codes
may also be considered as radio resource in the sense of
the present invention. Thus, a first radio resource may be
frequency, and a second radio resource may be a specific
code, and the like. In this case, the radio resource "code"
is assigned to the various terminals served on the same
frequency resources depending on the vertical angle.
The above described examples comprise a particularly simple
assignment rule for assignment of secondary radio resources
to the terminals. However, more complex assignment schemes
may also be applied.
The embodiments explained above are not limited to base
stations 100 of cellular communications networks. The
inventive principle may rather be applied to any base
station serving a plurality of terminals and employing
primary and secondary radio resources. Typically, the
principle may be applied with GSM- , UMTS -, LTE- , and WiMAXbase
stations.
5 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
10 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)
L t £ J 3. t - t- L C t g C C «O X-L t - s l C - x
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
20 encompass equivalents thereof.
The functions of the various elements shown in the Figures,
L L f J L t . .1 Jb 1 k .s 13 . G 1 S 5 s
may be provided through the use of dedicated hardware as
well as hardware capable of executing software in
25 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
30 '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
35 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
implementer as more specifically
understood from the context.
Claims
Method of operating a base station (100) for a
cellular communications network, said method
comprising:
the base station (100) determining (200) at least
two terminals (10, 11, 12) which are served by
the base station (100) and which are scheduled
for the same primary radio resource,
the base station (100) assigning (210) individual
portions of a secondary radio resource, which is
different from said primary radio resource, to
said at least two terminals (10, 11, 12)
depending on a parameter which characterizes a
vertical angle ( 12 ) between a virtual horizontal
plane (P) associated with said base station (100)
and a specific one of said terminals (10, 11,
12) .
Method according to claim 1 , wherein said base station
comprises an antenna (102) a tilt angle of which can
be controlled, and wherein said base station (100)
uses individual tilt angles for single terminals (10,
11, 12) and/or groups of terminals depending on said
parameter which characterizes said vertical angle
Method according to one of the preceding claims,
wherein said primary radio resource is time,
preferably transmission time slots, and wherein said
secondary radio resource is frequency, preferably
frequency subchannels.
Method according to claim 3 , wherein said base station
(100) assigns a first number of, preferably adjacent,
frequency subchannels (Ci) to a first one of said at
least two terminals (10, 11, 12) , and wherein said
base station (100) assigns a second number of,
preferably adjacent, frequency subchannels (Cj) to a
second one of said at least two terminals (10, 11,
12) .
Method according to one of the preceding claims,
wherein said base station (100) sorts said at least
two terminals (10, 11, 12) depending on said parameter
which characterizes said vertical angle ()
associated with said terminals (10, 11, 12) to obtain
a sorted list of terminals (10, 11, 12) , and wherein
said base station (100) assigns said portions of said
secondary radio resource depending on said sorted list
of terminals (10, 11, 12) .
Method according to one of the preceding claims,
wherein said step of assigning (210) said secondary
radio resource is performed according to a
predetermined scheme, particularly independent of
feedback information that characterizes an actual
quality of transmission between the base station (100)
and individual terminals (10, 11, 12) .
Method according to claim 6 , wherein said
predetermined scheme associates values and/or value
ranges of said parameter which characterizes a
vertical angle (2) with respective portions of said
secondary radio resources .
Base station (100) for a cellular communications
network, said base station (100) being configured to:
- determine (200) at least two terminals (10, 11,
12) which are served by the base station (100)
and which are scheduled for the same primary
radio resource, and to
assign (210) individual portions of a secondary
radio resource, which is different from said
primary radio resource, to said at least two
terminals (10, 11, 12) depending on a parameter
i h Ct Z6S 3. t C3. ()
between a virtual horizontal plane (P) associated
with said base station (100) and a specific one
of said terminals (10, 11, 12) .
Base station (100) according to claim 8 , wherein said
base station comprises an antenna (102) a tilt angle
of which can be controlled, and wherein said base
station (100) is configured to use individual tilt
angles for single terminals (10, 11, 12) and/or groups
of terminals depending on said parameter which
characterizes said vertical angle (2) .
Base station (100) according to one of the claims 8 to
9 , wherein said primary radio resource is time,
preferably transmission time slots, and wherein said
secondary radio resource is frequency, preferably
frequency subchannels.
Base station (100) according to one of the claims 8 to
10, wherein said base station (100) is configured to
assign a first number of, preferably adjacent,
frequency subchannels (Ci) to a first one of said at
least two terminals (10, 11, 12) , and to assign a
second number of, preferably adjacent, frequency
subchannels (Cj) to a second one o f said at least two
Base station (100) according to one o f the claims 8 to
11, wherein said base station (100) is configured to
sort said a t least two terminals (10, 11, 12)
depending on said parameter which characterizes said
vertical angle () associated with said terminals
(10, 11, 12) to obtain a sorted list o f terminals (10,
11, 12), and to assign said portions o f said secondary
c c x o sou. c d d c oil xd so t Xxst o f
terminals (10, 11, 12) .
Base station (100) according to one o f the claims 8 to
12, wherein said base station (100) is configured to
perform said step o f assigning (210) said secondary
- rrnrH - l - m
particularly independent o f feedback information that
characterizes an actual quality o f transmission
between the base station (100) and individual
terminals (10, 11, 12) .
Base station (100) according to one o f the claims 8 to
13, wherein said predetermined scheme associates
values and/or value ranges o f said parameter which
characterizes a vertical angle () with respective
portions o f said secondary radio resources.