U.S. patent application number 15/115121 was filed with the patent office on 2016-12-01 for method for operating a base station in a wireless radio network.
The applicant listed for this patent is SONY CORPORATION. Invention is credited to Erik BENGTSSON, Bo LARSSON, Zhinong YING.
Application Number | 20160353327 15/115121 |
Document ID | / |
Family ID | 50033364 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160353327 |
Kind Code |
A1 |
LARSSON; Bo ; et
al. |
December 1, 2016 |
METHOD FOR OPERATING A BASE STATION IN A WIRELESS RADIO NETWORK
Abstract
The present invention relates to a method for operating a base
station (11) in a wireless radio network (10). The base station
(11) comprises a plurality of antennas (12) for transmitting radio
frequency signals between the base station (11) and a user
equipment (UE1, UE2, UE3). According to the method, a transmission
slot (47) is provided for receiving at each antenna (12) of a
subset of the plurality of antennas (12) a training signal sent
from the user equipment (UE1, UE2, UE3). For each antenna (12) a
corresponding configuration parameter is determined based on the
training signal received at the corresponding antenna (12) and
payload information blocks (36, 37) to be transmitted between the
base station (11) and the user equipment (UE1, UE2, UE3) are
transmitted using the determined configuration parameters for the
antennas (12). A deterioration parameter indicating a deterioration
of a transmission between the base station (11) and the user
equipment (UE1, UE2, UE3) due to a change in the transmission
requiring adaption of the configuration parameters is determined.
Based on the deterioration parameter, a timing parameter is
determined for controlling when a further transmission slot (47) is
to be provided for receiving at each antenna (12) a next training
signal sent form the user equipment (UE1, UE2, UE3).
Inventors: |
LARSSON; Bo; (Malmo, SE)
; YING; Zhinong; (Lund, SE) ; BENGTSSON; Erik;
(Eslov, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SONY CORPORATION |
Minato-ku, Tokyo |
|
JP |
|
|
Family ID: |
50033364 |
Appl. No.: |
15/115121 |
Filed: |
January 29, 2015 |
PCT Filed: |
January 29, 2015 |
PCT NO: |
PCT/EP2015/051779 |
371 Date: |
July 28, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/0446 20130101;
H04L 25/0204 20130101; H04L 25/0222 20130101; H04W 4/027 20130101;
H04L 25/0226 20130101; H04B 17/318 20150115; H04W 4/029 20180201;
H04W 28/12 20130101; H04B 7/0452 20130101; H04B 7/0456 20130101;
H04W 4/026 20130101; H04B 17/336 20150115; H04B 7/0874
20130101 |
International
Class: |
H04W 28/12 20060101
H04W028/12; H04B 17/318 20060101 H04B017/318; H04W 72/04 20060101
H04W072/04; H04B 17/336 20060101 H04B017/336; H04B 7/04 20060101
H04B007/04; H04W 4/02 20060101 H04W004/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2014 |
EP |
14153322.4 |
Claims
1. A method for operating a base station in a wireless radio
network, the base station comprising a plurality of antennas for
transmitting radio frequency signals between the base station and a
user equipment, the method comprising: providing a transmission
slot for receiving at each antenna of a subset of the plurality of
antennas a training signal sent from the user equipment, wherein
for each antenna of the subset a corresponding configuration
parameter is determined based on the training signal received at
the corresponding antenna, and wherein payload information blocks
to be transmitted between the base station and the user equipment
are transmitted using the determined configuration parameters for
the antennas (12), determining a deterioration parameter indicating
a deterioration of a transmission between the base station and the
user equipment due to a change in the transmission requiring
adaption of the configuration parameters, and determining, based on
the deterioration parameter, a timing parameter for controlling
when a further transmission slot is to be provided for receiving at
each antenna of the subset of the plurality of antennas a next
training signal sent from the user equipment.
2. The method according to claim 1, wherein determining the
deterioration parameter comprises determining a relative movement
between the base station and the user equipment.
3. The method according to claim 1, wherein determining the
deterioration parameter comprises determining a spatial information
of the base station.
4. The method according to claim 3, wherein determining the spatial
information of the base station comprises at least one of a group
consisting of: determining a location of the base station,
determining a speed with which the base station is moving,
determining an acceleration with which the base station is
accelerated, and determining a direction of a movement of the base
station.
5. The method according to claim 4, wherein determining the
location of the base station comprises at least one of a group of:
determining a stationary position defined for the base station, and
determining a current position of the base station.
6. The method according to claim 1, wherein determining the
deterioration parameter comprises determining a spatial information
of the user equipment.
7. The method according to claim 6, wherein determining the spatial
information of the user equipment comprises at least one of a group
consisting of: determining a location of the user equipment,
determining a speed with which the user equipment is moving,
determining an acceleration with which the user equipment is
accelerated, and determining a direction of a movement of the user
equipment.
8. The method according to claim 7, wherein determining the
location of the user equipment comprises at least one of a group
of: determining a stationary position defined for the user
equipment, and determining a current position of the user
equipment.
9. The method according to claim 1, wherein determining the
deterioration parameter comprises at least one of a group
consisting of: determining a bit error rate of a transmission
between the base station and the user equipment using the
determined configuration parameters for the antennas, determining a
noise figure a transmission between the base station and the user
equipment using the determined configuration parameters for the
antennas, determining a signal level of a transmission between the
base station and the user equipment using the determined
configuration parameters for the antennas, and determining a change
in a footprint matrix of the user equipment in the determined
configuration parameters for the antennas.
10. The method according to claim 1, wherein determining the timing
parameter comprises determining, based on the deterioration
parameter, a next point in time at which the further transmission
slot for receiving the next training signal is to be provided.
11. The method according to claim 1, wherein determining the timing
parameter comprises determining, based on the deterioration
parameter, a training sequence rate value controlling a rate at
which further transmission slots are to be provided for receiving
at each antenna of the subset of the plurality of antennas next
training signals sent from the user equipment.
12. The method according to claim 1, wherein the configuration
parameter comprises at least one of a group consisting of: an
amplitude information, a phase information, a parameter pair
comprising an amplitude information and an associated phase
information, a plurality of the parameter pairs, and a signal
intensity.
13. The method according to claim 1, wherein the plurality of
antennas of the base station is configured for transmitting radio
frequency signals between the base station and a plurality of user
equipments, the method comprising: providing for each user
equipment of the plurality of user equipments a corresponding
transmission slot for receiving at each antenna of a subset of the
plurality of antennas a training signal sent from the corresponding
user equipment, wherein for each antenna of the subset a
corresponding configuration parameter is determined based on the
training signal received at the corresponding antenna, and wherein
payload information blocks to be transmitted between the base
station and the corresponding user equipment are transmitted using
the determined corresponding configuration parameters for the
antennas, determining for each user equipment a corresponding
deterioration parameter indicating a deterioration of a
transmission between the base station and the corresponding user
equipment due to a change in the transmission requiring adaption of
the configuration parameters, and determining for each user
equipment, based on the corresponding deterioration parameter, a
corresponding timing parameter for controlling when a further
transmission slot is to be provided for receiving at each antenna
of the subset of the plurality of antennas a next training signal
sent from the corresponding user equipment.
14. A base station for a wireless radio network, comprising: a
plurality of antennas for transmitting radio frequency signals
between the base station and a user equipment, and a processing
device configured to provide a transmission slot for receiving at
each antenna of a subset of the plurality of antennas a training
signal sent from the user equipment, wherein for each antenna of
the subset a corresponding configuration parameter is determined
based on the training signal received at the corresponding antenna,
and wherein payload information blocks to be transmitted between
the base station and the user equipment are transmitted using the
determined configuration parameters for the antennas, determine a
deterioration parameter indicating a deterioration of a
transmission between the base station and the user equipment due to
a change in the transmission requiring adaption of the
configuration parameters, and determine, based on the deterioration
parameter, a timing parameter for controlling when a further
transmission slot is to be provided for receiving at each antenna
of the subset of the plurality of antennas a next training signal
sent from the user equipment.
15. (canceled)
16. A user equipment for a wireless radio network, wherein the user
equipment is configured for transmission of radio frequency signals
between the user equipment and the base station according to claim
14.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for operating a
base station in a wireless radio network. Especially, the present
invention relates to a method for operating a base station
comprising a plurality of antennas for transmitting radio frequency
signals according to a so-called multiple-input and multiple-output
(MIMO) technology. The present invention relates furthermore to a
base station which implements the method, and a user equipment
which is configured to be used in connection with the base
station.
BACKGROUND OF THE INVENTION
[0002] For increasing data transmission performance and
reliability, the so-called multiple input and multiple-output
technology (MIMO) may be used in wireless radio frequency
telecommunications for transmitting information between a base
station and a user equipment. The MIMO technology relates to the
use of multiple send and receive antennas for a wireless
communication at for example a base station or a user equipment.
The MIMO technology forms the basis for coding methods which use
the temporal as well as the spatial dimension for transmitting
information and enables therefore a space and time coding. Thus, a
quality and data rate of the wireless communication may be
increased.
[0003] When a large number of user equipments is arranged within a
cell served by a base station having a plurality of antennas and
transmitting information according to the above-described MIMO
technology, such an arrangement is called a massive MIMO system. In
the massive MIMO system, a configuration of individual antenna
transceivers of the base station may vary depending on a location
of each of the user equipments and transmission conditions in an
environment of the base station and the user equipment.
[0004] The massive MIMO system may be used in connection with a
time division duplex (TDD) system in which a transmission of an
information stream between the base station and a user equipment is
split up in time slots. Different time slots for uplink (UL) data
communications and downlink (DL) data communications may be
provided for communicating information from the user equipment up
to the base station and for communicating information from the base
station down to the user equipment. In the massive MIMO system,
there is a need for an additional time slot which may be called
"header" for transmitting a training signal or a training sequence
from the user equipment to the base station. Based on the received
training signal, the base station may configure the transceivers of
its antenna array according to spatial and environmental
conditions. Thus, high antenna gain for the payload transmitted in
the following time slots can be achieved. The payload may be
transmitted in a number of uplink and downlink time slots. However,
when the user equipment is moving, the channel quality may degrade
due to a change of the spatial arrangement of the base station and
the user equipment.
[0005] Typically, massive MIMO systems are expected in buildings
such as offices, shopping malls and so on. In this environment a
large number of user equipments is expected. The mobility of the
user equipment or a changing spatial arrangement of the base
station and the user equipment may demand that channel training
sequences are sent frequently in order to keep up with the aging or
erosion of the antenna configurations of the MIMO system. The
faster a user equipment is moving, the more frequent a training
sequence needs to be transmitted from the user equipment to the
base station. Typically, the base stations in such a massive MIMO
system are configured in a way to allow a maximum speed or spatial
arrangement change of the user equipments. However, this may have
an impact on the system throughput as the frequently sent training
sequences may occupy a valuable and significant part of the data
communication channel. Furthermore, in a typical MIMO system, the
training sequences are transmitted from all user equipments within
the cell and possibly also neighboring cells in a dedicated time
slot. The training sequences need to be orthogonal in order for the
base station to identify the configuration parameters for the
plurality of antennas for each of the individual user equipments.
Orthogonality may be achieved by using time division multiple
access (TDMA), code division multiple access (CDMA) or frequency
division multiple access (FDMA) technologies or a combination
thereof. In a large cell including a large number of user
equipments, the header for transmitting the training sequences will
be very large.
[0006] Therefore, there is a need to improve the above-described
MIMO technology, especially to enhance the ratio between payload
information and header information to increase data throughput.
SUMMARY OF THE INVENTION
[0007] According to the present invention, this object is achieved
by a method for operating a base station in a wireless network as
defined in claim 1, a base station for a wireless radio network as
defined in claim 14, and a user equipment for a wireless radio
network as defined in claim 16. The dependent claims define
preferred and advantageous embodiments of the invention.
[0008] According to an aspect of the present invention, a method
for operating a base station in a wireless radio network is
provided. The base station comprises a plurality of antennas for
transmitting radio frequency signals between the base station and a
user equipment. The terms "transmit", "transmitting" etc. as used
in the present description may relate to receiving information from
the user equipment at the base station as well as sending
information from the base station to the user equipment. According
to the method, a transmission slot is provided, in which a training
signal sent from the user equipment is received at each antenna of
a subset of the plurality of antennas. In case a plurality of user
equipments are present, for each user equipment a corresponding
transmission slot may be provided, and within each corresponding
transmission slot, at each antenna of the subset of the plurality
of antennas the corresponding training signal sent from the
corresponding user equipment may be received. Therefore, the
training signal may be received simultaneously at each antenna of
the subset of the plurality of antennas during the provided
transmission slot. The training signals need to be orthogonal in
order for the base station to identify the configuration parameters
for the plurality of antennas for each of the individual user
equipments. Orthogonality may be achieved by using time division
multiple access (TDMA), code division multiple access (CDMA) or
frequency division multiple access (FDMA) technologies or a
combination thereof. When using time division multiple access
(TDMA) for transmitting trainings signals, each training signal may
be transmitted in a separate time slot. Therefore, in a TDMA
system, the transmission slot corresponds to a time slot. For each
antenna of the subset, a corresponding configuration parameter is
determined based on the training signal received at the
corresponding antenna, and payload information blocks to be
transmitted between the base station and the user equipment are
transmitted using the determined configuration parameters for the
antennas. The subset of the plurality of antennas may comprise
those antennas of the plurality of antennas which are arranged to
receive the training signal from the user equipment. For example,
if the antennas of the base station are arranged cylindrically,
only a subset of the antennas may receive the training signal sent
from the user equipment, whereas some other antennas may not
receive the training signal. Furthermore, if a very large antenna
array is used, only a part or a subset of the array of antennas may
be used for a specific user equipment. However, the subset may also
comprise all antennas of the plurality of antennas provided at the
base station. As an example, the base station may comprise for
example an antenna array of thirty to one hundred or even more
antennas arranged for example in a matrix or cylindrically.
Likewise, the user equipment may comprise one or more antennas, for
example one to four antennas. Due to the configuration parameters
determined for each antenna of the subset of the plurality of
antennas, the base station may be enabled to communicate with the
user equipment according to the above-described MIMO technology.
According to the method, a deterioration parameter is determined
which indicates a deterioration or degradation of a transmission
between the base station and the user equipment due to a change in
the transmission which would require an adaption of the
configuration parameters. A deterioration of a transmission due to
a change in the transmission requiring adaption of the
configuration parameters may comprise for example a deterioration
due to a change of a spatial arrangement of the base station and
the user equipment, or due to a change in an environment of the
base station or the user equipment resulting in a change of a
propagation path of the transmission between the base station and
the user equipment. Based on the deterioration parameter, a timing
parameter is determined for controlling when a further next or
following transmission slot is to be provided for receiving at each
antenna of the subset of the plurality of antennas a next training
signal sent from the user equipment.
[0009] For example, in a typical massive MIMO system a lot of user
equipments may be arranged within a cell served by the base
station. However, especially in the scenario of a massive MIMO
system in buildings such as offices or shopping malls, a lot of the
user equipments may be stationary, for example desktop computers,
cash registers, supervision cameras and so on. Such stationary user
equipments may have the same or even a higher need for bandwidth as
mobile user equipments like mobile phones, especially smart phones,
tablet PCs and so on. However, adaption of the configuration
parameters for transmitting data between the base station and the
stationary user equipments is required less frequently than an
update of configuration parameters used for data transmissions
between the base station and user equipments which are changing
their position with the respect to the base station. Therefore,
according to the above-described method, a timing for controlling
when a further transmission slot is to be provided for receiving a
next training signal from each user equipment is determined
individually for each user equipment based on a deterioration
parameter indicating a deterioration of a transmission between the
base station and the corresponding user equipment. For example, a
fast moving user equipment may transmit training signals more
frequently than slow moving user equipments or stationary user
equipments. A fast moving user equipment may transmit a training
signal each frame, while stationary or slow moving user equipments
may transmit training signals less often, for example every other
frame or every third frame. Further, also user equipments in idle
mode having no active payload communication may transmit training
signals less often, for example every other frame or even less
often, in order to verify that they are still in the coverage of
the base station. The determined timing or allocation scheme may
need to provide synchronization between the user equipments and the
base station. For example, the base station may allocate an
appropriate timing for each user equipment taking into account the
individual mobility of each of the user equipments. This may enable
to set up a system with a smaller header in each frame, or it may
allow more user equipments to be connected to the same base
station. This implies that the cells payload capacity may be
improved compared to a system in which a transmission slot is
allocated for each user equipment in each frame independent of the
mobility. Furthermore, due to adapting the timing for providing the
transmission slots for receiving training signals, the header size
of each frame may be allocated dynamically to reflect the
collective mobility of the user equipments attached to the base
station. This may increase system performance, since the header may
dynamically become smaller when the number of stationary user
equipments grows. Therefore, the relative size of the header may
decrease versus the payload. Vice versa, the header may dynamically
become larger when the number of moving user equipments is growing.
This information may be communicated and synchronized with
neighboring cells.
[0010] According to an embodiment, the deterioration parameter
comprises determining a movement of the base station and/or a
movement of the user equipment. A change of a special arrangement
of the user equipment with respect to the base station may require
an update of the configuration parameters of the antennas for
ensuring a high performance data communication. For example, the
deterioration parameter may be determined by determining a relative
movement between the base station and the user equipment. In case
the base station as well as the user equipment are moving, there
may be no relative movement between them, for example when the base
station is arranged in a train and the user equipment is a mobile
phone or a mobile computer located stationary within the same
train. In this case, although both, the base station and the user
equipment, are moving, a deterioration of the communication between
them is not expected and therefore the configuration parameters are
not needed to be updated very frequently and therefore a
transmission slot for receiving training signals from the user
equipment may be provided less frequently. However, when there is a
fast relative movement determined between the base station and the
user equipment, for example when the base station is arranged
stationary and the user equipment is moving along in a vehicle, a
significant deterioration is expected when the user equipment is
moving out of the focus of the antennas of the base station defined
by the configuration parameters. Therefore, transmission slots for
receiving training signals from the user equipment have to be
provided more frequently for updating the configuration
parameters.
[0011] For example, the deterioration parameter may be determined
by determining a spatial information of at least one of the base
station and the user equipment. The spatial information of the base
station may be determined by determining a speed with which the
base station is moving, an acceleration with which the base station
is accelerated or a direction of movement of the base station, or
by determining a location of the base station. The location of the
base station may be a predefined stationary position of the base
station or may be determined for example based on a global
positioning system like GPS. The spatial information of the user
equipment may be determined by determining a speed with which the
user equipment is moving, an acceleration with which the user
equipment is currently accelerated, a direction in which the user
equipment is currently moved or by determining a current location
of the user equipment. The current location of the user equipment
may be determined from a predefined stationary position defined for
the user equipment or based on a current global position,
determined e.g. by a global positioning system like GPS. For
determining the current position of the user equipment, sensors of
the user equipment like an accelerometer and/or a gyrometer may be
used.
[0012] According to another embodiment, the deterioration parameter
may be determined by a bit error rate of a transmission between the
base station and the user equipment while data is communicated
between the base station and the user equipment using the
determined configuration parameters for the antennas. Determining
the bit error rate may be advantageous for example in case there is
essentially no relative movement between the base station and the
user equipment, but there is a change in the environment
influencing the transmission between the base station and the user
equipment. For example, when the base station and the user
equipment are arranged stationary and have a direct line of sight
at the beginning of a communication, the configuration parameters
may be determined and configured correspondingly. However, an
object, for example a vehicle, may be moving such that it obstructs
at least partially the direct line of sight between the base
station and the user equipment. In this case, the bit error rate
may increase and based on this information, the timing for
providing transmission slots for receiving further training signals
may be adapted accordingly to maintain a high quality data
communication between the base station and the user equipment.
Therefore, especially considering the spatial information
concerning the base station and the user equipment in combination
with the bit error rate enables determining and estimating a
deterioration of the transmission between the base station and the
user equipment very efficiently such that the timing parameter for
controlling when a further transmission slot is to be provided for
receiving a next training signal may be determined appropriately.
Additionally or as an alternative, the deterioration parameter may
be determined by a noise figure and/or a signal level of the
transmission between the base station and the user equipment.
Furthermore, additionally or as an alternative, the deterioration
parameter may be determined by detecting a change in a so-called
footprint matrix of the user equipment. The footprint matrix
relates for example to a characteristic pattern in the antenna
configuration parameters formed by the training signal from user
equipment, when the configuration parameters are for example
arranged in a matrix corresponding to a matrix arrangement of the
antennas. When the user equipment is moving, the configuration
parameter pattern may also be moving from frame to frame. This
change or movement may be used to determine the deterioration
parameter.
[0013] According to another embodiment, based on the deterioration
parameter, a next point in time, at which the further transmission
slot for receiving the next training signal is to be provided, is
determined as the timing parameter. For example, based on the
deterioration parameter, for a certain user equipment it may be
determined that it is sufficient to provide a transmission slot for
receiving the next training signal in a few hundred milliseconds,
for example in 700 milliseconds. Thus, an appropriate frame may be
selected and in this frame a corresponding transmission slot for
receiving the next training signal may be provided. Thus, the
transmission slots for receiving the training signals may be used
very efficiently.
[0014] According to another embodiment, based on the deterioration
parameter, a training sequence rate value may be determined which
controls a rate at which further transmission slots are to be
provided for receiving at each antenna of the subset of the
plurality of antennas next training signals from the user
equipment. For example, when a very slow relative movement between
a user equipment and a base station is determined, the training
sequence rate value may be determined such that transmission slots
for receiving training signals from this certain user equipment are
provided in every other frame or in every fifth frame. However,
when a fast relative movement between the user equipment and the
base station is determined or the bit error rate of the
transmission between the base station and the user equipment is
varying significantly, the training sequence rate value may be
determined such that a corresponding transmission slot for
receiving the training signals from this user equipment is provided
in every frame. Therefore, an efficient usage of the transmission
slots for the training signals may be ensured and thus the amount
of overhead for receiving training signals can be reduced and the
payload performance may be increased.
[0015] According to another embodiment, the configuration parameter
determined for each antenna of the subset of the plurality of
antennas of the base station may comprise for example an amplitude
information, a phase information, a parameter pair comprising an
amplitude information and an associated phase information, a
plurality of these parameters, or a signal intensity information of
a signal intensity received at the corresponding antenna during
receiving the training signal. However, the above-listed types of
configuration parameters are only examples and the configuration
parameters may comprise other or additional information for
configuring the antennas of the base station to enable a data
transmission according to the above-described MIMO transmission
scheme. Furthermore, the phase and the amplitude information may be
used directly to determine the configuration parameter for
receiving uplink payload information from the user equipment, as
the training sequence has been sent in the same uplink direction.
However, the configuration parameter for sending downlink payload
information blocks to the user equipment may be determined based on
a Hermitian transpose of the configuration parameter for receiving
uplink payload information blocks. For example, if two uplink
signal beams from the user equipment are received at the base
station with different delay (phase), for sending downlink beams
the phases need to be reversed as the beam with the shorter path
comes in first and both beams need to be aligned at the user
equipment in the downlink direction.
[0016] According to another embodiment, the plurality of antennas
of the base station is configured for transmitting radio frequency
signals between the base station and a plurality of user
equipments. For each user equipment of the plurality of user
equipments a corresponding transmission slot is provided for
receiving at each antenna of a subset of the plurality of antennas
a training signal sent from the corresponding user equipment. The
training signals need to be orthogonal in order for the base
station to identify the configuration parameters for the plurality
of antennas for each of the individual user equipments.
Orthogonality may be achieved by using time division multiple
access (TDMA), code division multiple access (CDMA) or frequency
division multiple access (FDMA) technologies or a combination
thereof. For each antenna of the subset a corresponding
configuration parameter is determined based on the training signal
received at the corresponding antenna. Payload information blocks
to be transmitted between the base station and the corresponding
user equipment are transmitted using the determined corresponding
configuration parameters for the antennas. Furthermore, for each
user equipment a corresponding deterioration parameter indicating a
deterioration of a transmission between the base station and the
corresponding user equipment due to a change in the transmission
and requiring adaption of the configuration parameters is
determined. Based on the corresponding deterioration parameter, for
each user equipment a corresponding timing parameter is determined
for controlling when a further transmission slot is to be provided
for receiving at each antenna of the subset of the plurality of
antennas a next training signal sent from the corresponding user
equipment. By adapting the timing for providing the training signal
transmission slots for each user equipment individually, the header
space in each frame containing the transmission slots for the
training signals and the payload information blocks may be used
efficiently. Furthermore, the header size may be adapted
accordingly and therefore the available bandwidth may be used more
efficiently.
[0017] According to another aspect of the present invention, a base
station for a wireless radio network is provided which comprises a
plurality of antennas for transmitting radio frequency signals
between the base station and a user equipment, and a processing
device. The processing device is configured to provide a
transmission slot for receiving at each antenna of a subset of the
plurality of antennas a training signal sent from the user
equipment. The training signals need to be orthogonal in order for
the base station to identify the configuration parameters for the
plurality of antennas for each of the individual user equipments.
Orthogonality may be achieved by using time division multiple
access (TDMA), code division multiple access (CDMA) or frequency
division multiple access (FDMA) technologies or a combination
thereof. For each antenna of the subset a corresponding
configuration parameter is determined based on the training signal
received at the corresponding antenna. Then, payload information
blocks to be transmitted between the base station and the user
equipment may be transmitted using the determined configuration
parameters for the antennas. The configuration parameters for the
antennas may be different for receiving payload information blocks
and for sending information blocks. However, the configuration
parameter for an antenna for sending as well as a configuration
parameter for the antenna for receiving may be determined based on
the training signal. The processing device is furthermore
configured to determine a deterioration parameter indicating a
deterioration of a transmission between the base station and the
user equipment due to a change in the transmission. Especially, the
processing device is configured to determine a deterioration which
requires an adaption of the configuration parameters to remedy the
deterioration. Based on the deterioration parameter, the processing
device determines a timing parameter for controlling when a further
transmission slot is to be provided for receiving at each antenna
of the subset of the plurality of antennas a next training signal
from the user equipment. In other words, the processing device is
configured to determine if a more frequent transmission of training
signals is needed to maintain the configuration parameters of the
antennas in the above-described MIMO system updated, or if a less
frequent transmission of training parameters and update of the
configuration parameters is sufficient. Therefore, an amount of
overhead data to be transmitted may be reduced and thus the
provided bandwidth may be used more efficiently for payload
information.
[0018] According to an embodiment, the base station is configured
to perform the embodiments of the above-described method and
comprises therefore the advantages describes above.
[0019] According to another aspect of the present invention, a user
equipment for a wireless radio network is provided. The user
equipment is configured for transmission of radio frequency signals
between the user equipment and the base station described above.
Therefore, the user equipment supports the MIMO technology
described above and comprises therefore the above-described
advantages.
[0020] Although specific features described in the above summary
and the following detailed description are described in connection
with specific embodiments and aspects of the present invention, it
should be understood that the features of the exemplary embodiments
and aspects may be combined with each other unless specifically
noted otherwise.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present invention will be described in more detail with
reference to the accompanying drawings.
[0022] FIG. 1 shows schematically a base station and user
equipments according to embodiments of the present invention.
[0023] FIG. 2 shows a flow chart comprising method steps for
adapting a timing for controlling training signal time slots
according to an embodiment of the present invention.
[0024] FIG. 3 shows an assignment of time slots for transmitting
training signals according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0025] In the following, exemplary embodiments of the present
invention will be described in more detail. It is to be understood
that the features of the various exemplary embodiments described
herein may be combined with each other unless specifically noted
otherwise. Same reference signs in various drawings refer to
similar of identical components. Any coupling between components or
devices shown in the figures may be a direct or an indirect
coupling unless specifically noted otherwise.
[0026] FIG. 1 shows three user equipments UE1, UE2 and UE3 arranged
in an environment 10 of a base station 11. The base station 11
comprises a plurality of antennas 12 and associated transceivers
13. In FIG. 1 only six antennas 12 and six transceivers 13 are
shown for clarity reasons. However, these are only exemplary
numbers and the base station 11 may comprise for example an array
of 30 to 100 or even more antennas and associated transceivers
arranged for example in a matrix or cylindrically. Likewise, the
user equipments UE1, UE2 and UE3 may comprise each one or more
antennas, for example, each user equipment may comprise one to four
antennas or three antennas as shown in FIG. 1. The base station 11
comprises furthermore a processing device (PD) 14 coupled to the
transceivers 13 and adapted to configure the transceivers 13 for
transmitting radio frequency signals between the base station 11
and the user equipments UE1, UE2 and UE3.
[0027] The multiple antennas 12 and transceivers 13 of the base
station 11 may be used and configured such that the above-described
multiple-input and multiple-output (MIMO) technology may be
utilized for transmissions between the base station 11 and the user
equipments UE1, UE2 and UE3. The signal processing according the
MIMO technology may be performed in the analog or digital domain or
a combination thereof. Therefore, for example, a part of the
transceiver functionality may be implemented digitally, for example
in a signal processor or in the processing device, and the antennas
12 and the remaining parts of the transceivers 13 may be passive
components.
[0028] For determining configuration parameter sets for the
transceivers 13 of the base station 11 which provide a high quality
transmission taking into account spatial information of the user
equipments UE1, UE2 and UE3 with respect to the base station, a
training signal or a training sequence of radio frequency signals
may be transmitted from each corresponding user equipment UE1, UE2
or UE3 to the base station. Based on the received training signal,
corresponding configuration parameters for the transceivers 13 may
be determined in the base station 11. However, when one of the user
equipments is moving, for example the user equipment UE2 as
indicated by arrow 15 in FIG. 1, the transmission quality will
degrade unless the corresponding configuration parameters are
updated for the new position. Furthermore, even when the user
equipment is not moving, as for example the user equipments UE1 and
UE3 in FIG. 1, due to changes in the environment, as for example
indicated in FIG. 1 by a vehicle 17 moving in the direction
indicated by arrow 16, the transmission quality may degrade unless
the corresponding configuration parameters are updated for the new
environment. An update may be performed by transmitting a further
training signal and determining updated configuration parameters
based on the training signals received at the base station 11.
However, this limits the speed with which the user equipments are
allowed to move or with which environmental changes are allowed to
take place without degrading transmission performance. Reducing the
interval between emitting the training signals from the user
equipments UE1, UE2 and UE3 to the base station 11 may reduce
overall system performance due to an increasing amount of data for
the training signals. Therefore, less time slots, so-called "pilot
channels", are provided for each transmission block or frame than
user equipments are arranged within a cell served by the base
station. Then, fast moving user equipments or user equipments in a
changing environment, may use a time slot in each frame, while
stationary or slow moving user equipments may use time slots less
often. The allocation scheme needs to provide synchronization
between the user equipments and the base station. For example, the
base station allocates an appropriate frequency for the time slots
to each user equipment. By taking the mobility of the user
equipments and the environment into account, when allocating the
time slots, the amount of header information may be reduced per
frame. Therefore, the header size may be reduced and the cell's
payload capacity may be improved compared to a system where a
training signal time slot is allocated for each user equipment in
each frame.
[0029] FIG. 2 shows the above-summarized method in more detail. The
method 20 shown in FIG. 2 comprises method steps 21 to 26. In step
21 a time slot is provided for receiving at each antenna 12 of the
base station 11 a training signal sent from each of the user
equipments UE1, UE2 and UE3 (step 22). In step 23 for each antenna
a corresponding configuration parameter is determined based on the
training signal received at the corresponding antenna 12. In step
24 payload information blocks are transmitted between the base
station and the user equipment using the determined configuration
parameters for the antennas 12. In step 25 a deterioration
parameter of a transmission between the base station and each of
the user equipments UE1, UE2 and UE3 is determined. The
deterioration parameter may be determined based on spatial
information of the base station and each of the user equipments.
For example, a relative movement between the base station and each
of the user equipments may be determined. The spatial information
may be derived from inherent configuration parameters indicating
for example a stationary position of the base station or the user
equipment, or may be determined based on for example geographic
information of a global positioning system. The spatial information
may comprise furthermore a location, a speed, an acceleration and a
moving direction. The corresponding spatial information of the user
equipments UE1, UE2 and UE3 may be transmitted to the base station
in corresponding information protocol data units. Based on the
spatial information of the base station and each of the user
equipments UE1, UE2 and UE3, the base station may determine if a
deterioration of the transmission between the base station and the
corresponding user equipment may occur due to a position change and
an adaption of the configuration parameters of the antennas 12 is
required to compensate this. Furthermore, for taking into account
environmental changes like the moving vehicle 17 in FIG. 1, the
base station may additionally monitor a bit error rate of each
transmission to determine if an adaption of the configuration
parameters of the antennas 12 is required to maintain a high
quality data transmission. Furthermore, the deterioration parameter
may be determined by a noise figure or a signal level of the
transmission between the base station and the user equipment.
Additionally or as an alternative, the deterioration parameter may
be determined by detecting a change from frame to frame in a
footprint matrix of the user equipment, which is a characteristic
pattern in the antenna configuration parameters formed by the
training signal from user equipment. Based on this deterioration
parameters determined or estimated by the base station 11, for each
user equipment UE1, UE2 and UE3 a timing for a further time slot or
a time slot rate for receiving a next training signal is determined
in step 26. Therefore, for slow moving or stationary user
equipments less time slots for receiving training signals are
provided than for user equipments having a high mobility or user
equipments arranged with respect to the base station in a rapidly
changing environment.
[0030] FIG. 3 shows providing or allocating the time slots for
receiving the training signals in more detail. FIG. 3 shows a
plurality of transmission frames 31 to 34. Each transmission frame
comprises a header 35, 38, 41 and 44, respectively, and a payload
information block comprising an uplink UL payload information block
36, 39, 42 and 45, respectively, and a downlink DL payload
information block 37, 40, 43 and 46, respectively. As shown in more
detail with respect to the header 35, each header comprises a
plurality of time slots 47 for receiving training signals from the
user equipments. In the example shown in FIG. 3, the header
comprises eight time slots 47. In the example shown in FIG. 3, the
user equipments UE1 and UE3 are stationary, whereas the user
equipment UE2 is moving. Therefore, the moving user equipment UE2
transmits the training sequence in every frame as indicated by the
arrows, whereas the stationary user equipments UE1 and UE3 transmit
their training sequences in every other frame only. In detail, user
equipment UE1 transmits its training sequences in transmission
frames 31 and 33, and user equipment UE3 transmits its training
sequences in transmission frames 32 and 34. Therefore, the header
size may be reduced and more payload information may be
transmitted. Furthermore, the adaption of the configuration
parameters within the base station 11 may be performed for the user
equipments UE1 and UE3 less frequently which may reduce also the
calculation intensity within the base station 11.
[0031] As described above, the training signals need to be
orthogonal in order for the base station to identify the
configuration parameters for the plurality of antennas for each of
the individual user equipments. In the above described exemplary
embodiments, the training signals are separated by using different
time slots, in a time division multiple access (TDMA) technology.
However, orthogonality may be achieved by other orthogonal access
technologies like code division multiple access (CDMA) or frequency
division multiple access (FDMA) technologies or a combination
thereof.
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