U.S. patent application number 16/071747 was filed with the patent office on 2019-01-31 for a method and a network node for muting antenna elements of an active antenna system.
This patent application is currently assigned to Telefonaktiebolaget LM Ericsson (publ). The applicant listed for this patent is Telefonaktiebolaget LM Ericsson (publ). Invention is credited to Fredrik ATHLEY, Martin JOHANSSON, Andreas NILSSON, Sven PETERSSON.
Application Number | 20190036587 16/071747 |
Document ID | / |
Family ID | 55299437 |
Filed Date | 2019-01-31 |
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United States Patent
Application |
20190036587 |
Kind Code |
A1 |
NILSSON; Andreas ; et
al. |
January 31, 2019 |
A METHOD AND A NETWORK NODE FOR MUTING ANTENNA ELEMENTS OF AN
ACTIVE ANTENNA SYSTEM
Abstract
The disclosure relates to a method (20) performed in a network
node (5, 9, 7) of a communication system (1) for muting antenna
elements of an active antenna system (11). The method (20)
comprises determining (22), based on a priori information relating
to performance of the communication system (1), an antenna element
separation between one or more pairs of active antenna elements of
at least a subset of all active antenna elements of the active
antenna system (11); and muting (24) at least one antenna element
such that the determined antenna element separation is obtained
between each of the one or more pairs of active antenna elements of
at least the subset of all active antenna elements. A corresponding
network node (5, 9, 7), computer programs and computer program
products are also disclosed.
Inventors: |
NILSSON; Andreas; (Goteborg,
SE) ; ATHLEY; Fredrik; (Kullavik, SE) ;
JOHANSSON; Martin; (Molndal, SE) ; PETERSSON;
Sven; (Savedalen, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Telefonaktiebolaget LM Ericsson (publ) |
Stockholm |
|
SE |
|
|
Assignee: |
Telefonaktiebolaget LM Ericsson
(publ)
Stockholm
SE
|
Family ID: |
55299437 |
Appl. No.: |
16/071747 |
Filed: |
January 25, 2016 |
PCT Filed: |
January 25, 2016 |
PCT NO: |
PCT/EP2016/051457 |
371 Date: |
July 20, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 7/0693 20130101;
Y02D 30/70 20200801; H01Q 3/24 20130101; Y02D 70/444 20180101; Y02D
70/122 20180101; H04B 7/0877 20130101; H04W 52/0206 20130101; Y02D
70/1262 20180101 |
International
Class: |
H04B 7/06 20060101
H04B007/06; H04B 7/08 20060101 H04B007/08; H04W 52/02 20060101
H04W052/02; H01Q 3/24 20060101 H01Q003/24 |
Claims
1. A method performed in a network node of a communication system
for muting antenna elements of an active antenna system, the method
comprising: determining, based on a priori information relating to
performance in the communication system, an antenna element
separation between one or more pairs of active antenna elements of
at least a subset of all active antenna elements of the active
antenna system; and muting at least one antenna element such that
the determined antenna element separation is obtained between each
of the one or more pairs of active antenna elements of at least the
subset of all active antenna elements.
2. The method of claim 1, comprising determining a number of active
antenna elements to mute such as to meet a performance requirement
in the communication system and wherein the muting comprises muting
the determined number of active antenna elements.
3. The method of claim 1, wherein the a priori information
comprises a set of predetermined antenna element separations, and
wherein the determining the antenna element separation comprises
selecting, among the set of predetermined antenna element
separations, an antenna element setting best corresponding to a
performance requirement in the communication system.
4. The method of claim 3, wherein the set of predetermined antenna
element separations are based on statistics obtained for different
antenna element separations during antenna element muting.
5. The method of claim 1, wherein the active antenna system
provides coverage in at least a first cell, wherein the a priori
information comprises information on measured interference for one
or more radiation patterns for the active antenna system and
wherein the determining the antenna element separation comprises
determining the antenna element separation giving a radiation
pattern minimizing interference towards communication devices
outside the first cell.
6. The method of claim 1, wherein the active antenna system
provides coverage in at least a first cell, wherein the a priori
information comprises information obtained on grating lobes of the
active antenna system and wherein the determining the antenna
element separation comprises determining the antenna element
separation such that grating lobes of the resulting radiation fall
outside an angular region of communication devices served outside
the first cell.
7. The method of claim 1, comprising, prior to the determining the
antenna element separation, determining a reduction in required
number of active antenna elements of the active antenna system.
8. The method of claim 7, wherein the determining the reduction in
required number of active antenna comprises determining that a
traffic load in the first cell has reduced.
9. The method of claim 1, wherein the muting is performed for
uplink, for downlink and/or separately for each cell of the
communication system.
10-22. (canceled)
23. The method of claim 1, wherein the performance in the
communication system comprises one of: user throughput in uplink,
user throughput in downlink, throughput in uplink for cell-edge
user and throughput in downlink for cell-edge user, network node
utilization and a maximum power consumption threshold.
24. A computer program product comprising a non-transitory computer
readable medium storing a computer program for muting antenna
elements of an active antenna system, the computer program
comprising computer program code, which, when executed on at least
one processor of a network node causes the network node to perform
the method of claim 1.
25. A network node of a communication system for muting antenna
elements of an active antenna system, the network node being
configured to: determine, based on a priori information relating to
performance in the communication system, an antenna element
separation between one or more pairs of active antenna elements of
at least a subset of all active antenna elements of the active
antenna system; and mute at least one antenna element such that the
determined antenna element separation is obtained between each of
the one or more pairs of active antenna elements of at least the
subset of all active antenna elements.
26. The network node of claim 25, configured to determine a number
of active antenna elements to mute such as to meet a performance
requirement in the communication system and configured to mute by
muting the determined number of active antenna elements.
27. The network node of claim 25, wherein the a priori information
comprises a set of predetermined antenna element separations, and
wherein the network node is configured to determine the antenna
element separation by selecting, among the set of predetermined
antenna element separations, an antenna element setting best
corresponding to a performance requirement in the communication
system.
28. The network node of claim 27, wherein the set of predetermined
antenna element separations are based on statistics obtained for
different antenna element separations during antenna element
muting.
29. The network node of claim 25, wherein the active antenna system
provides coverage in at least a first cell, wherein the a priori
information comprises information on measured interference for one
or more radiation patterns for the active antenna system and
wherein the network node is configured to determine the antenna
element separation by determining the antenna element separation
giving a radiation pattern minimizing interference towards
communication devices outside the first cell.
30. The network node of claim 25, wherein the active antenna system
provides coverage in at least a first cell, wherein the a priori
information comprises information obtained on grating lobes of the
active antenna system and wherein the network node is configured to
determine the antenna element separation by determining the antenna
element separation such that grating lobes of the resulting
radiation fall outside an angular region of communication devices
served outside the first cell.
31. The network node of claim 25, configured to, prior to the
determining the antenna element separation, determine a reduction
in required number of active antenna elements of the active antenna
system.
32. The network node of claim 31, configured to determine the
reduction in required number of active antenna by determining that
a traffic load in the first cell has reduced.
33. The network node of claim 25, wherein the performance in the
communication system comprises one of: user throughput in uplink,
user throughput in downlink, throughput in uplink for cell-edge
user and throughput in downlink for cell-edge user, network node
utilization and a maximum power consumption threshold.
Description
TECHNICAL FIELD
[0001] The technology disclosed herein relates generally to the
field of wireless communications systems, and in particular to a
method, a network node, computer program and computer program
products for muting antenna elements of an active antenna
system.
BACKGROUND
[0002] The use of communication devices and wireless broadband has
increased rapidly during the last decade, and is expected to grow
even faster coming years. To meet these demands network capacity
has to be increased, and this demand should be met while
considering the energy consumption, since energy efficiency is an
important criterion for future networks.
[0003] One efficient way to increase the capacity in the network is
to deploy active antennas for user-specific beamforming (BF). The
more antenna elements in the array the higher order of beamforming
can be applied. The beamforming permits multiple data streams to
use same frequencies at the same time, giving a way to increase the
capacity. Simulations have shown that the capacity can be increase
with 30% for each doubling of number of elements in the active
antenna array. Another way to increase the capacity in the network
is to increase the number of radio access nodes (e.g. base
stations) and use smaller cells, whereby a more efficient spatial
reuse can be obtained and the capacity hence be increased. However,
with many cells and denser deployment of base stations the energy
consumption would increase in the network, being both costly and
having a negative effect on the environment.
[0004] The capacity need in networks varies and during non-busy
hours the base station utilization in the network typically is very
low. The base stations consume much power even though there is no
data transmitted. Studies have shown that at zero base station
utilization the base station still consumes more than half of the
power consumption at 100% base station utilization. Large part of
the zero load power consumption is due to the radio chains
consuming much power even though no data is transmitted. Studies
have also shown promising results when muting, i.e. turning off,
one or several antenna ports/antenna elements and their
corresponding radio in order to save energy.
[0005] From the above it is clear that an increased network
capacity and reduced energy consumption are important for future
networks and ways for meeting these requirements are therefore
desirable.
SUMMARY
[0006] An objective of the present teachings is to enable reduced
energy consumption in a network. Another objective is to provide an
improved way of muting antenna elements, whereby a total energy
consumption in a network may be reduced. Another objective is to
enable the energy saving by the muting of antenna elements without
increasing interference.
[0007] The objective is according to an aspect achieved by a method
performed in a network node of a communication system for muting
antenna elements of an active antenna system. The method comprises
determining, based on a priori information relating to performance
in the communication system, an antenna element separation between
one or more pairs of active antenna elements of at least a subset
of all active antenna elements of the active antenna system, and
muting at least one antenna element such that the determined
antenna element separation is obtained between each of the one or
more pairs of active antenna elements of at least the subset of all
active antenna elements.
[0008] An advantage of the method is that system performance, e.g.
in terms of energy savings and system throughput, is improved
compared to known methods for antenna element muting. For a given
performance requirement, a higher number of antenna elements can be
muted compared to the known methods, and hence a higher reduction
in energy consumption is achieved.
[0009] The objective is according to an aspect achieved by a
computer program for a network node for muting antenna elements of
an active antenna system. The computer program comprises computer
program code, which, when executed on at least one processor on the
network node causes the network node to perform the method as
above.
[0010] The objective is according to an aspect achieved by a
computer program product comprising a computer program as above and
a computer readable means on which the computer program is
stored.
[0011] The objective is according to an aspect achieved by a
network node of a communication system for muting antenna elements
of an active antenna system.
[0012] The network node is configured to determine, based on a
priori information relating to performance in the communication
system, an antenna element separation between one or more pairs of
active antenna elements of at least a subset of all active antenna
elements of the active antenna system, and mute at least one
antenna element such that the determined antenna element separation
is obtained between each of the one or more pairs of active antenna
elements of at least the subset of all active antenna elements.
[0013] Further features and advantages of the present teachings
will become clear upon reading the following description and the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 illustrates schematically an environment in which
embodiments of the present teachings may be implemented.
[0015] FIG. 2 illustrates simulation results on downlink capacity
as function of element separation.
[0016] FIGS. 3a and 3b illustrate a conventional method of muting
antenna elements and a method of muting antenna elements according
to the present teachings, respectively.
[0017] FIG. 4 illustrates simulation results for a conventional
method and a method according to the present teachings.
[0018] FIGS. 5a and 5b illustrate a conventional method of muting
antenna elements and a method of muting antenna elements according
to the present teachings, respectively.
[0019] FIG. 6 illustrates simulation results on user throughput as
function of offered traffic.
[0020] FIGS. 7a and 7b illustrate flow charts over steps of
embodiments of the method in a network node in accordance with the
present teachings.
[0021] FIG. 8 illustrates schematically a network node and means
for implementing embodiments according to the present
teachings.
[0022] FIG. 9 illustrates a network node comprising function
modules/software modules for implementing embodiments according to
the present teachings.
DETAILED DESCRIPTION
[0023] In the following description, for purposes of explanation
and not limitation, specific details are set forth such as
particular architectures, interfaces, techniques, etc. in order to
provide a thorough understanding. In other instances, detailed
descriptions of well-known devices, circuits, and methods are
omitted so as not to obscure the description with unnecessary
detail. Same reference numerals refer to same or similar elements
throughout the description.
[0024] Briefly, according to the present teachings the separation
between antenna elements, in the following also denoted element
separation, is considered when performing antenna muting in order
to save energy. The performance of communication device-specific
beamforming depends on the separation of the antenna elements of an
active antenna. Optimal element separation in turn depends on how
the base station is deployed and how the surroundings are. In view
of these aspects, the present teachings suggest, in various
embodiments, that when performing antenna muting, the antenna
elements are muted such that the remaining (active) elements get an
element separation that maximizes the performance of the system.
Which element separation that is best for a certain base station is
considered and may depend on various circumstances, for example the
orientation of the active antenna array, the placement of the base
station, the surrounding deployment (e.g. placement of neighboring
base stations) etc. The present teachings suggest several ways to
find an appropriate element separation for a base station. For
instance, prior knowledge about the antenna deployment may be used
or the base station may test different element separations and log
the performance for each element separation and after having
gathered enough statistics the element separation that gives best
performance may be selected.
[0025] FIG. 1 illustrates an environment in which embodiments of
the present teachings may be implemented. In particular, a
communication system 1 is illustrated comprising a radio access
network (RAN) 2 and a core network (CN) 3. An external packet data
network (PDN) 4 is also illustrated.
[0026] The RAN 2 comprises one or more radio access nodes 5, which
may be denoted differently, e.g. base station, evolved NodeB, or
eNB to mention a few examples. The radio access node 5 provides
wireless communication for communication devices 6 (in the
following exemplified by user equipment, UE) residing within its
coverage area. In this context it is noted that one such radio
access node 5 may control several geographical areas, e.g. cells or
sectors. Each such radio access node 5 may comprise and/or control
an antenna system 11. The antenna system 11 may comprise an active
antenna system. In an active antenna system each antenna
(radiating) element in a (phased) antenna array is connected to
separate radio frequency (RF) components, such as power amplifiers
and transceivers. This enables individual phase and amplitude
control. Signal processing can be used to shape and steer radiated
beam patterns, e.g. vertically and horizontally (vertical
beamforming and horizontal beamforming). Beams can be created and
steered e.g. within one cell. By such active antenna system 11 UE
specific beam forming may be applied, aperture reused
sectorization, Multi-User multiple-input and multiple-output
(MU-MIMO) technologies and various other features.
[0027] The CN 3 comprises various network nodes, which may also be
denoted differently depending on communication system at hand. In
LTE, for instance, the CN 3 may comprise entities such as a
Mobility Management Entity (MME) 9 and packet data network gateways
(PDN GW) 10 providing connectivity to e.g. the PDN 4.
[0028] The communication system 1 may comprise or be connectable to
a PDN 4, which in turn may comprise a server 7 or cluster of
servers, e.g. a server of the Internet ("web-server") or any
application server. Such server 7 may run applications 8. It is
noted that some embodiments according to the present teachings may
be implemented in a distributed manner, wherein different steps are
performed by different entities, and may be implemented locally
and/or in a centralized component (e.g. in a so called cloud
environment). The network node in which a method according to the
teachings may be implemented may comprise a server or other entity
on the Internet e.g. according to a cloud computing model.
[0029] FIG. 2 illustrates simulation results on downlink capacity
as function of element separation. The simulations were performed
for a realistic urban Asian scenario in which UE-specific
beamforming was applied. It is noted that in all simulations,
regardless of number of used elements, the total output power is
the same (40W). Therefore, if a certain output power is assumed per
power amplifier (PA), the performance should not be compared for
different numbers of antenna elements in the array. For instance,
the performance of the 1.times.8 array cannot be compared with the
performance of the 1.times.2 array, because they have different
output power per PA. However, different antenna separations with
the same number of antenna elements in the array are comparable.
For instance, different points on the curve for the 1.times.2 array
can be compared to all the other points of this curve. From the
denotation "a.times.b array" the number and placement of the
antenna elements can be deduced. For instance, 2.times.1 array is a
vertical array with 2 elements (the array comprises one column and
two rows, i.e. two elements one above the other in the vertical
direction) while a 1.times.2 array is a horizontal array with two
elements (the array comprises two columns and one row, i.e. the
array comprises two elements side by side in the horizontal
direction).
[0030] The simulation results of FIG. 2 show that the element
separation has a large effect on the system performance. As can be
seen in the graphs, the downlink capacity in the simulated urban
Asian scenario changes with element separation for vertical arrays
(upper graph of FIG. 2) as well as for horizontal arrays (lower
graph of FIG. 2). In particular, for this specific scenario the
dependence between capacity and element separation for the vertical
array is especially strong. What can also be seen is that the
typical half a wavelength separation between the elements gives
significantly lower capacity than around one wavelength between the
elements. In the simulations cell specific reference signals
(CRSs), used by UEs for cell selection, are transmitted on element
patterns.
[0031] FIGS. 3a and 3b illustrate a conventional method of muting
antenna elements (FIG. 3a) and a method of muting antenna elements
according to the present teachings (FIG. 3b). Regarding muting of
antenna elements according to prior art, it is conventionally
simply assumed that the best performance is obtained when keeping
the antenna elements close to each other, and the conventionally
used antenna element separation is hence typically around
0.5.lamda..
[0032] An active antenna system 11 with a vertical array comprising
eight antenna elements with antenna element separation of
0.5.lamda. is used as an example in the following. The antenna
elements are numbered from top down, i.e. the uppermost antenna
element is denoted first antenna element, the next antenna element
from the top is denoted second etc. until the bottommost antenna
element, which is denoted eight antenna element. This numbering is
also indicated at the leftmost part of FIG. 3a. When the traffic
goes down from "high traffic" to "low traffic" it may be possible
to mute a number of the antenna elements in order to save energy,
while still maintaining sufficient performance in the network. The
performance may be measured according to some key performance
indicator (KPI) defined by the operator of the network. As an
example for comparing the known, conventional method to the herein
proposed method it is assumed that the traffic load is reduced from
a maximum traffic load and that this in turn means that it is
possible to turn off four of the eight antenna elements while still
maintaining good enough performance in the network.
[0033] The conventional method, illustrated in FIG. 3a, hence
comprises just turning off the four antenna elements from the top,
i.e. elements numbered 1 to 4 (or from the bottom, elements
numbered 8 to 5) to keep an antenna element distance of 0.5.lamda..
That is, when going from the high-traffic scenario to the
low-traffic scenario, the first through fourth antenna elements are
turned off. In contrast, the method according to the present
teachings for muting antenna elements, illustrated in FIG. 3b,
comprises determining an antenna element separation that maximizes
the performance. In the illustrated case, the antenna element
separation that maximizes the performance is, in this case,
determined to be 1.lamda., and the second, fourth, sixth and eighth
antenna elements may therefore be turned off, giving the determined
antenna element separation.
[0034] How to determine the antenna element separation that
maximizes the performance is described and exemplified next.
Finding the appropriate antenna element separations for each cell
may be done in a number of different ways. In common for the
embodiments is that the determination is based on a priori
information, i.e. information gathered beforehand, which
information relates to the performance in the communication system
1 or part thereof (e.g. performance in a cell C1, C2 or in two
cells of the communication system 1).
[0035] A first way is to use prior knowledge of the network
deployment to find the appropriate antenna element separation, e.g.
how and where the active antenna system 11 is placed and located.
As has been shown, a vertical array may not give the same
performance in the communication system 1 as a horizontal array
(see e.g. FIG. 2 and related description). Further, placing the
active antenna system 11 at a high location (e.g. roof top) may
give different performance than placing it on a wall. Such network
deployment issues may hence be used. For instance, it may be
assured that the grating lobes of the desired main beam fall
outside the angular region of UEs served by other cells. This
ensures that the interference is kept at a minimum. In terms of
performance (or performance requirement) in the communication
system 1 this may correspond to maximum interference that can be
tolerated while still meeting e.g. a certain user data rate. By
selecting another antenna element separation, even although
involving a higher number of active antennas, the interference may
instead increase as a neighboring base station might need to
increase its transmission power for these interfered UEs. The total
energy consumption in the communication system 1 might then
increase, despite the antenna muting of another base station and/or
cell. The approximate locations of UEs may be determined in known
manner, e.g. using triangulation based on signal strength or timing
advance. This deployment dependent selection is exemplified and
explained later in relation to FIG. 6.
[0036] Another way is to perform measurements in order to find
directions of served and interfered UEs and use this knowledge to
find appropriate element separations. Patterns of user behavior
can, for instance, be determined by logging data corresponding to
user positions, traffic demands etc., which could be calculated in
the network.
[0037] Still another way to find appropriate antenna element
separations, and hence a priori information on performance in the
communication system 1, is to test different element separations
per cell during antenna muting, gather performance statistics and
when enough statistics have been gathered choose the antenna
element separation that gave the best performance. If changes to
the environment occur, for instance if high buildings are built in
the environment, then the statistic gathering may need to be
performed again.
[0038] FIG. 4 illustrates the throughput for downlink and uplink as
a function of traffic load for the conventional method and the
method according to the present teachings, respectively, for a
4.times.1 antenna array. That is, this corresponds to the situation
of FIG. 3 when the reduced traffic load can still be met although
muting four of eight antenna elements. The arrows denoted "c"
indicate the results when using the conventional method, for 5%-ile
and 50%-ile with antenna element separation of 0.5.lamda.. The
arrows denoted "p" indicate the results when using the herein
proposed method, also for 5%-ile and 50%-ile with antenna element
separation .lamda.. As can be seen the throughput is higher at
basically all traffic loads for the method according to the present
teachings compared to the conventional method.
[0039] Assuming next that the traffic load reduces even further and
that it is now possible to have six of the eight antenna elements
turned off, while still maintaining high enough performance in the
network.
[0040] FIGS. 5a and 5b illustrate the above scenario, and in
particular how the muting of antenna elements is done for the
conventional method (FIG. 5a) and the method according to the
present teachings (FIG. 5b), respectively. The respective low
traffic antenna settings of FIGS. 3a and 3b are the starting points
here. The conventional method, FIG. 5a, simply turns off two
additional antenna elements by turning off the uppermost of the
currently active antenna elements, i.e. fifth and sixth antenna
elements, thus keeping the antenna element separation of
0.5.lamda.. In contrast to this, the current method determines that
an antenna element separation of 2.lamda. would now be the most
appropriate selection for the current scenario, and hence turns off
the third and seventh antenna elements, leaving only the first and
the fifth antenna elements active and having the determined antenna
element separation of 2.lamda..
[0041] FIG. 6 illustrates the throughput for the respective case,
now for a 2.times.1 antenna array, since only two antenna elements
are now active. As in FIG. 4, the arrows denoted "c" indicate the
results when using the conventional method, for 5%-ile and 50%-ile
with antenna element separation of 0.5.lamda.. The arrows denoted
"p" indicate the results when using the herein proposed method,
also for 5%-ile and 50%-ile with antenna element separation of
2.lamda.. As can be seen, the proposed method again gives higher
throughput than the conventional method for basically all traffic
loads. Since the performance for the proposed method is higher
compared to the conventional method it might be possible to turn
off a higher number of elements with the proposed method while
still maintaining a given performance requirement for the network.
For example, assuming that the operator wants to have a certain
throughput for the cell edge users (5%-ile user throughput); For
the conventional method it might require five antenna elements to
fulfill the required cell edge throughput at the current traffic
load, while for the proposed method the requirement might be
fulfilled with only four elements. In this case the proposed method
may be used to save more energy compared to the conventional
method. Hence, the proposed method could either be used to save the
same amount of energy as the conventional method but increase the
performance compared to conventional method or maintain similar
performance but save more energy.
[0042] In the simulations (FIGS. 4 and 6) the antenna element
separation was the same for all cells in the network. This might be
sub-optimal, since each cell has most likely its own optimal
antenna element separation, depending on for example how the base
station is deployed, how the surroundings looks etc. Knowing in
which angular span the serving UEs and the interfering UEs (i.e.
UEs served by a neighboring base station and/or cell) are with
respect to the serving base station can be used to decide
appropriate element separation.
[0043] For instance, from the simulations it was evident that for
macro base stations placed on top of buildings with vertical arrays
the element separation should be large. The reason for this is that
the angular span of the served UEs and interfering UEs were similar
and rather narrow (i.e. the UEs were located rather densely). So in
this case, with this antenna placement, it is better to use large
element separation to generate a narrow UE-specific beam towards
the served UEs since this results in less interference towards the
interfering UEs. Further, since the angular span of the UEs was
rather narrow the grating lobes that were created by the large
element separation did not cause any further interference.
Specifically, owing to the antenna placement on top of a building,
the grating lobes were directed towards the sky, and did not cause
interference towards the interfering UEs. Different base stations
have different angular spans to the served and interfering UEs and
hence, in some embodiments, individual element separations are used
per base station when applying antenna muting, giving an additional
advantage.
[0044] The proposed method may, for instance, be used for LTE, LTE
evolution and NX.
[0045] Even though, in the examples above, both transmit and
receive radio chains have been turned off in order to save energy,
it is possible to, for instance, only turn off the transmit radio
chain and keep the receive radio chain on. One reason for this
could be that most of the energy will be saved by turning off the
transmit radio chain due to their power amplifiers.
[0046] It is also possible to mute different elements in DL and UL
if, for instance, the optimal element separation differs between DL
and UL.
[0047] The antenna muting (turning off elements when traffic load
allows) can be done both in a quick or slow time scale, from
seconds up to hours.
[0048] The features and various embodiments that have been
described can be combined in different ways, examples of which are
given in the following.
[0049] FIG. 7a illustrates a flow chart over steps of an embodiment
of a method 20 in a server device in accordance with the present
teachings.
[0050] A method 20 is provided which may be performed in a network
node 5, 9, 7 of a communication system 1 for muting antenna
elements of an active antenna system 11. The method 20 comprises
determining 22, based on a priori information relating to
performance in the communication system 1, an antenna element
separation between one or more pairs of active antenna elements of
at least a subset of all active antenna elements of the active
antenna system 11.
[0051] The method 20 further comprises muting 24 at least one
antenna element such that the determined antenna element separation
is obtained between each of the one or more pairs of active antenna
elements of at least the subset of all active antenna elements.
[0052] In some embodiments the determined antenna element
separation is to be obtained for all active antenna elements, while
in other embodiments the determined element separation is to be
obtained between two adjacent active antenna elements of a subset
of all active antenna elements.
[0053] The method brings about several advantages. For instance, an
advantage of the method is that system performance, e.g. in terms
of energy savings and interference level, is improved compared to
known methods for antenna element muting. For a given performance
requirement (any KPI of a particular operator), a higher number of
antenna elements can be muted compared to the known methods, and
hence a higher reduction in energy consumption is achieved.
Alternatively, a higher performance can be provided by the method
with the same energy consumption when compared to the known method
of muting antennas.
[0054] In this regards it is noted that the "a priori information"
means information obtained beforehand about the performance in the
communication system 1. The a priori known information, or simply a
priori information, may for instance comprise fixed antenna
separations corresponding to a certain load in the network node 5,
9, 7 in turn indicating how many active antenna elements would be
needed, wherein the fixed antenna separations have been determined
in dependence on deployment of the network nodes and active antenna
system 11. The a priori known information may comprise amount of
traffic that can be handled in the system for different number of
active antenna elements. As still another example, the priori known
information may comprise information about which antenna element
separation has shown to be best for two or more different base
stations.
[0055] In an embodiment, the method 20 comprises determining 23 a
number of active antenna elements to mute such as to meet a
performance requirement in the communication system 1 and wherein
the muting 24 comprises muting the determined number of active
antenna elements. That is, the number of currently active antenna
elements to mute may be based on some performance requirement.
[0056] In some embodiments, the a priori information comprises a
set of predetermined antenna element separations, and wherein the
determining 22 the antenna element separation comprises selecting,
among the set of predetermined antenna element separations, an
antenna element setting best corresponding to a performance
requirement in the communication system 1. The performance
requirement may, for instance, comprise a certain user data rate to
be provided, or channel quality.
[0057] In a variation of the above embodiment, the set of
predetermined antenna element separations are based on statistics
obtained for different antenna element separations during antenna
element muting. As an example, statistics of an average user
throughput may be gathered, or cell-edge user throughput or base
station utilization.
[0058] In some embodiments, the active antenna system 11 provides
coverage in at least a first cell C1, wherein the a priori
information comprises information on measured interference for one
or more radiation patterns for the active antenna system 11 and
wherein the determining 22 the antenna element separation comprises
determining the antenna element separation giving a radiation
pattern minimizing interference towards communication devices
outside the first cell C1.
[0059] In some embodiments, the active antenna system 11 provides
coverage in at least a first cell C1, wherein the a priori
information comprises information obtained on grating lobes of the
active antenna system 11 and wherein the determining 22 the antenna
element separation comprises determining the antenna element
separation such that grating lobes of the resulting radiation fall
outside an angular region of communication devices served outside
the first cell C1. The a prior information relating to performance
in the communication system may, in such embodiments, comprise
information on grating lobes of resulting radiation for different
antenna element separations.
[0060] In an embodiment, the method 20 comprises, prior to the
determining 22 the antenna element separation, determining 21 a
reduction in required number of active antenna elements of the
active antenna system 11. The method 20 may thus be triggered by
some indication that a reduction of the currently number of active
antenna elements is possible. Such determining 21 may be performed
in different ways. In one embodiment, the determining 21 the
reduction in required number of active antenna comprises
determining that a traffic load in the first cell C1 has reduced.
This is an example of a clear indication that some antenna elements
could be turned off while still serving the communication devices
within the cell with a required performance.
[0061] In different embodiments, the muting 24 is performed for
uplink, for downlink and/or separately for each cell C1, C2 of the
communication system 1.
[0062] In different embodiments, the performance in the
communication system 1 comprises one or more of: user throughput in
uplink, user throughput in downlink, throughput in uplink for
cell-edge user and throughput in downlink for cell-edge user,
network node 5, 9, 7 utilization and a maximum power consumption
threshold.
[0063] FIG. 7b illustrates another embodiment of the method 20, and
gives an example on how to combine the different features and
embodiments that have been described. In particular, in this
embodiment the method 20 comprises determining 21 a reduction in
required number of active antenna elements of the active antenna
system 11. The determination may be performed in any manner that
has been described, e.g. by detecting that the load in the
communication system 1, or the load in a certain network node 5
thereof, has reduced and that the required number of active antenna
elements may therefore be reduced, without affecting the providing
of requested services in the communication system 1 or in a cell C1
provided by the network node 5.
[0064] The method 20 further comprises, in this embodiment,
determining 22, based on a priori information relating to
performance in the communication system 1, an antenna element
separation between one or more pairs of active antenna elements of
at least a subset of all active antenna elements of the active
antenna system 11.
[0065] The method 20 further comprises, in this embodiment,
determining 23 a number of active antenna elements to mute such as
to meet a performance requirement in the communication system 1 and
wherein the muting 24 comprises muting the determined number of
active antenna elements.
[0066] The method 20 further comprises, in this embodiment, muting
24 at least one antenna element such that the determined antenna
element separation is obtained between each of the one or more
pairs of active antenna elements of at least the subset of all
active antenna elements.
[0067] The method 20 may comprise determining an antenna element
separation between two active antenna elements, such that the
antenna element separation results in a radiation meeting a
performance requirement, and then muting at least one antenna
element such that the determined antenna element separation is
obtained between each of one or more pairs of active antenna
elements of at least a subset of all active antenna elements.
[0068] FIG. 8 illustrates schematically a network node and means
for implementing embodiments according to the present
teachings.
[0069] The network node 5, 9, 7 comprises a processor 40 comprising
any combination of one or more of a central processing unit (CPU),
multiprocessor, microcontroller, digital signal processor (DSP),
application specific integrated circuit etc. capable of executing
software instructions stored in a memory 41 which can thus be a
computer program product 41. The processor 40 can be configured to
execute any of the various embodiments of the method 20 for
instance as described in relation to FIG. 7a or FIG. 7b.
[0070] The memory 41 can be any combination of read and write
memory (RAM) and read only memory (ROM), Flash memory, magnetic
tape, Compact Disc (CD)-ROM, digital versatile disc (DVD), Blu-ray
disc etc. The memory 41 may also comprise persistent storage,
which, for example, can be any single one or combination of
magnetic memory, optical memory, solid state memory or even
remotely mounted memory.
[0071] The network node 5, 9, 7 comprises an interface 43 for
communication with other network node and/or with communication
devices. The interface 43 may, for instance, comprise an interface
e.g. protocol stacks etc., for communication with wireless
communication devices, e.g. an UE, and also an interface, e.g.
protocol stacks etc. for communication with other network
nodes.
[0072] The network node 5, 9, 7 may comprise an antenna control
device 44 for, for instance, controlling antenna elements of an
active antenna system 11. The antenna control device 44 may
comprise control circuitry for controlling the active antenna
system 11, to which is may be connected e.g. in a wired fashion.
Such control circuitry may be adapted to mute and activate specific
antenna elements of the active antenna system 11, to determine how
many and which antenna elements to mute or activate etc.
[0073] The network node 5, 9, 7 may comprise additional processing
circuitry, schematically indicated at reference numerals 45 for
implementing the various embodiments according to the present
teachings.
[0074] A network node 5, 9, 7 of a communication system 1 is
provided for muting antenna elements of an active antenna system
11. The network node 5, 9, 7 is configured to: [0075] determine,
based on a priori information relating to performance in the
communication system 1, an antenna element separation between one
or more pairs of active antenna elements of at least a subset of
all active antenna elements of the active antenna system 11, and
[0076] mute at least one antenna element such that the determined
antenna element separation is obtained between each of the one or
more pairs of active antenna elements of at least the subset of all
active antenna elements.
[0077] The network node 5, 9, 7 may be configured to perform the
above steps e.g. by comprising one or more processors 40 and memory
41, the memory 41 containing instructions executable by the
processor 40, whereby the network node 5, 9, 7 is operative to
perform the steps.
[0078] In an embodiment, the network node 5, 9, 7 is configured to
determine a number of active antenna elements to mute such as to
meet a performance requirement in the communication system 1 and
configured to mute by muting the hence determined number of active
antenna elements.
[0079] In an embodiment, the a priori information comprises a set
of predetermined antenna element separations, and the network node
5, 9, 7 is configured to determine the antenna element separation
by selecting, among the set of predetermined antenna element
separations, an antenna element setting best corresponding to a
performance requirement in the communication system 1.
[0080] In an embodiment, the set of predetermined antenna element
separations are based on statistics obtained for different antenna
element separations during antenna element muting.
[0081] In an embodiment, the active antenna system 11 provides
coverage in at least a first cell C1, and the a priori information
comprises information on measured interference for one or more
radiation patterns for the active antenna system 11 and wherein the
network node 5, 9, 7 is configured to determine the antenna element
separation by determining the antenna element separation giving a
radiation pattern minimizing interference towards communication
devices outside the first cell C1.
[0082] In an embodiment, the active antenna system 11 provides
coverage in at least a first cell C1, and the a priori information
comprises information obtained on grating lobes of the active
antenna system 11 and wherein the network node 5, 9, 7 is
configured to determine the antenna element separation by
determining the antenna element separation such that grating lobes
of the resulting radiation fall outside an angular region of
communication devices served outside the first cell C1.
[0083] In an embodiment, the network node 5, 9, 7 is configured to,
prior to the determining the antenna element separation, determine
a reduction in required number of active antenna elements of the
active antenna system 11.
[0084] In an embodiment, the network node 5, 9, 7 is configured to
determine the reduction in required number of active antenna by
determining that a traffic load in the first cell C1 has
reduced.
[0085] In an embodiment, the network node 5, 9, 7 is configured to
mute for uplink, for downlink and/or separately for each cell C1,
C2 of the communication system 1.
[0086] In various embodiments, the performance requirement
comprises one of: user throughput in uplink, user throughput in
downlink, throughput in uplink for cell-edge user and throughput in
downlink for cell-edge user, network node 5, 9, 7 utilization and a
maximum power consumption threshold.
[0087] In an embodiment, a network node of a communication system
is provided for muting antenna elements of an active antenna
system. The network node comprises one or more processors and
memory, the memory containing instructions executable by the
processor, whereby the network node is operative to: [0088]
determine, based on a priori information relating to performance in
the communication system, an antenna element separation between one
or more pairs of active antenna elements of at least a subset of
all active antenna elements of the active antenna system, and
[0089] mute at least one antenna element such that the determined
antenna element separation is obtained between each of the one or
more pairs of active antenna elements of at least the subset of all
active antenna elements.
[0090] The present teachings also encompass a computer program 42
for a network node 5, 9, 7 for muting antenna elements of an active
antenna system. The computer program 42 comprises computer program
code, which, when executed on at least one processor on the network
node 5, 9, 7 causes the network node 5, 9, 7 to perform the method
20 according to any of the described embodiments.
[0091] The present teachings also encompasses computer program
products 41 comprising a computer program 42 for implementing the
embodiments of the method as described, and a computer readable
means on which the computer program 42 is stored. The computer
program product, or the memory, thus comprises instructions
executable by the processor 40. Such instructions may be comprised
in a computer program, or in one or more software modules or
function modules. The computer program product 41 may be any
combination of random access memory (RAM) or read only memory
(ROM), Flash memory, magnetic tape, Compact Disc (CD)-ROM, digital
versatile disc (DVD), Blu-ray disc etc.
[0092] FIG. 9 illustrates a network node comprising function
modules/software modules for implementing embodiments according to
the present teachings. The function modules can be implemented
using software instructions such as computer program executing in a
processor and/or using hardware, such as application specific
integrated circuits (ASICs), field programmable gate arrays,
discrete logical components etc., and any combination thereof.
Processing circuitry may be provided, which may be adaptable and in
particular adapted to perform any of the steps of the method 20
that has been described.
[0093] A network node is provided for muting antenna elements of an
active antenna system. The network node comprises a first module 52
determining, based on a priori information relating to performance
of the communication system 1, an antenna element separation
between one or more pairs of active antenna elements of at least a
subset of all active antenna elements of the active antenna system
11. Such first module 52 may, for instance, comprise processing
circuitry adapted to determine an antenna element separation based
on a priori known information.
[0094] The network node comprises a second module 54 for muting at
least one antenna element such that the determined antenna element
separation is obtained between each of the one or more pairs of
active antenna elements of at least the subset of all active
antenna elements. Such second module 54 may, for instance, comprise
processing circuitry adapted to inhibit signals from being sent
from the antenna element to be muted. The second module 54, may as
another example, comprise processing circuitry adapted to send a
control signal for turning the radio chain on or off.
[0095] The network node may comprise additional function modules
for implementing the embodiments according to the present
teachings. The network node may, for instance, comprise a third
function module 51 for determining 21 a reduction in required
number of active antenna elements of the active antenna system 11.
Such third function module 51 may, for instance, comprise
processing circuitry adapted to determine the reduction in required
number of active antenna elements. The processing circuitry may for
instance be adapted to detect current network load and use network
load thresholds corresponding to a required number of active
antenna elements for the determination.
[0096] As another example, the network node may comprise a fourth
function module 93 for determining 23 a number of active antenna
elements to mute such as to meet a performance requirement in the
communication system 1. Such fourth function module 93 may, for
instance, comprise processing circuitry adapted for such
determination.
[0097] It is noted that one or more of the modules 52, 54, 51, 53
may be replaced by units.
[0098] The invention has mainly been described herein with
reference to a few embodiments. However, as is appreciated by a
person skilled in the art, other embodiments than the particular
ones disclosed herein are equally possible within the scope of the
invention, as defined by the appended patent claims.
* * * * *