METHOD AND DEVICE FOR FEEDING BACK DOWNLINK CHANNEL
FEEDBACK INFORMATION, AND METHOD AND DEVICE FOR USER
MATCHING
5 FIELD OF THE INVENTION
[0001] The disclosure generally relates to a communication field, in particular to feeding
back downlink channel feedback information of a user in a Multiple Input Multiple Output,
MIMO, communication system and user pairing of a base station.
10 BACKGROUND OF THE INVENTION
[0002] In MIMO system, multi-antenna transmission is divided into single user MIMO
(SU-MIMO) transmission mode and multi-user MIMO (MU-MIMO) transmission mode.
[0003] As shown in Figure 1, in the SU-MIMO transmission, a base station (BS) sends a
plurality of data streams on the same time-frequency resource to the same user. In contrast, in
15 the MU-MIMO transmission, a base station (BS) sends a plurality of data streams on the same
time-frequency resource to different users, and improves the system capacity by transmitting
data simultaneously to a plurality of users.
[0004] Pre-coding technology is a signal processing technology which pre-processes the
transmitted symbols at the transmitting side by using channel state in order to eliminate
20 interference, improve system capacity and the like. The pre-coding needs the base station to
know transmission channel information and determine a pre-coding matrix based on the
transmission channel information. For example, pre-coding technology may be a pre-coding
technology based on codebook, in which the codebook is the same with respect to user
equipment (UE) and base station (BS). A user notifies a base station of the pre-coding matrix
25 used by the user by feeding back a pre-coding matrix indication (PMI) to the base station.
[0005] In MIMO transmission technology using the pre-coding technology, the PMI may be
included in downlink channel feedback information which a user needs to feed back to a base
station. The downlink channel feedback information is information for reflecting the
downlink channel state which the user feeds back to the base station through uplink channel.
30 [0006] In MIMO systems of LTE, for example, in downlink channel feedback of SU-MIMO,
-1 -
^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
W Sony Ref.: SP314891IN00
Our Ref.: OP1211-06-0773
the downlink channel feedback information which a user feeds back to a base station may
includes: the PMI for indicating a pre-coding matrix; and a feedback channel quality
indication (CQI) for selecting a modulation coding mode of transmission data by the base
station. In LTE standards, in the situation of MU-MIMO transmission, the PMI and CQI in
5 the downlink channel feedback information which a user feeds back to a base station is
obtained by optimizing the PMI and CQI in the situation of SU-MIMO transmission.
However, using the PMI obtained in the situation of SU-MIMO transmission in MU-MIMO
transmission may induce influence to the selection of paired user in MU-MIMO transmission
and thus influence to the communication performance.
10 [0007] In addition, from the perspective of base station side, after the user feeding back the
downlink channel feedback information, the base station determines whether the MU-MIMO
transmission or the SU-MIMO transmission is used according to the downlink channel
feedback information. As for SU-MIMO transmission, the base station obtains the pre-coding
matrix according to the PMI in the downlink channel feedback information, and selects a
15 suitable modulation coding mode for the user according to the CQI in the downlink channel
feedback information. As for MU-MIMO transmission, the base station needs to first select
paired user(s) for the user according to the downlink channel feedback information fed back
by the user, and then obtain a pre-coding matrix for the user and select a suitable modulation
coding mode for the user according to the PMI and CQI included in the downlink channel
20 feedback information fed back by individual paired users selected for this user.
SUMMARY OF THE INVENTION
[0008] A brief summary about the present disclosure is provided hereinafter to provide
basic understandings related to some aspects of the present disclosure. It shall be understood
25 that this summary is not an exhaustive summary related to the present disclosure. The
summary is not intended to determine a key part or an important part of the present disclosure,
nor does it intend to limit the scope of the present disclosure. The purpose of the summary is
only to provide some concepts in simplified forms to prelude more detailed descriptions
discussed later
30 [0009] One object of the disclosure is to provide feeding back of downlink channel
feedback information, which may further increase information for representing the quality
- 2 -
> English translation of PCT publication Sony China Ref.: CNPA10058IN00
Sony Ref.: SP314891IN00
Our Ref.: OP 1211-06-0773
indication error caused by the user parameter errors (such as the signal to noise ratio (SNR),
synchronization difference, location difference and the like) in the MU-MIMO transmission in
the downlink channel feedback information, in the downlink channel feedback of the
MU-MIMO transmission, thereby to achieve feeding more accurate downlink channel
5 feedback information back to the base station. Moreover, the base station may obtain CQI and
modulation coding mode more suitable for the user in a more accurate manner. Therefore, the
demodulation error code rate may be reduced and the system performance may be improved.
[0010] Correspondingly, the other object of the disclosure is to provide user pairing at base
station side, which uses information for representing the quality indication error caused by the
10 parameter errors (such as the signal to noise ratio, synchronization difference, location
difference and the like) of the user in the MU-MIMO transmission, thereby to achieve more
accurate modulation coding and pairing. Therefore, the demodulation error code rate of the
user may be reduced and the system performance may be improved.
[0011] Therefore, one embodiment of the disclosure provides a method for feeding back
15 downlink channel feedback information of a MIMO communication system, comprising:
calculating a multi-user channel quality indication error of a user in the system by the user,
the multi-user channel quality indication error is used to reflect the difference in channel
quality indication between the situation of multi-user multiple input multiple output
transmission and the situation of single user multiple input multiple output transmission; and
20 adding the multi-user channel quality indication error to the downlink channel feedback
information including a pre-coding matrix indication and a channel quality indication, and
feeding the same back to a base station for scheduling of the user.
[0012] Another embodiment of the disclosure provides a method for user pairing of MIMO,
comprising: a downlink channel feedback information receiving step of receiving downlink
25 channel feedback information from a user, the downlink channel feedback information
includes a pre-coding matrix indication, a channel quality indication, and a multi-user channel
quality indication error, wherein the multi-user channel quality indication error is used to
reflect the difference in channel quality indication between the situation of MU-MIMO
transmission and the situation of SU-MIMO transmission of the user; an initial paired user
- 3 -
^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
•** Sony Ref. :SP314891IN00
Our Ref.: OP 1211-06-0773
selecting step of selecting the user with the minimum multi-user channel quality indication
error from transmitting users as an initial paired user, the transmitting users include all the
current transmitting users which are allowed to enter a multi-user multiple input multiple
output transmission mode; a correlation calculating step of calculating the correlation of each
5 paired user to each of other transmitting users, and selecting one or more users from the other
transmitting users as candidate paired user(s) according to the correlation; a paired user
selecting step of selecting paired user(s) from the candidate paired user(s) according to the
multi-user channel quality indication error; and repeating the correlation calculating step and
the paired user selecting step until a predetermined number of paired users have been selected.
10 [0013] Another embodiment of the disclosure provides a method for communication in a
Multiple Input Multiple Output system, comprising: feeding downlink channel feedback
information back to a base station by a user; deciding by the base station whether a single user
multiple input multiple output transmission mode or a multi-user multiple input multiple
output transmission mode is used; obtaining a pre-coding matrix of the user by using a
15 pre-coding matrix indication in the fed back downlink channel feedback information, and
selecting a modulation coding mode for the user by using a channel quality indication in the
fed back downlink channel feedback information, by the base station, in case of using the
single user multiple input multiple output transmission mode; and executing pairing for the
user, obtaining a pre-coding matrix for the multi-user multiple input multiple output
20 transmission mode based on the pre-coding matrix indication in the downlink channel
feedback information fed back by the user and the paired user(s) thereof, and selecting
modulation coding mode corresponding to each user based on the channel quality indication
and the multi-user channel quality indication error in the downlink channel feedback
information fed back by the user and paired user(s) thereof, by the base station, in case of
25 using the multi-user multiple input multiple output transmission mode; wherein the user uses
the method for feeding back as described above to feed the downlink channel feedback
information back to the base station, and the base station uses the method for user pairing as
described above to execute user pairing.
- 4 -
| * English translation of PCT publication Sony China Ref.: CNPA10058IN00
~ Sony Ref.: SP314891IN00
OurRef.:OP1211-06-0773
[0014] In addition, one embodiment of the disclosure provides an apparatus for feeding
back downlink channel feedback information of a MIMO communication system, comprising:
a multi-user channel quality indication error calculating unit configured to calculate a
multi-user channel quality indication error of a user, wherein the multi-user channel quality
5 indication error is used to reflect the difference in channel quality indication between the
situation of multi-user multiple input multiple output transmission and the situation of single
user multiple input multiple output transmission of the user; and a downlink channel feedback
information feeding back unit configured to add the multi-user channel quality indication
error to the downlink channel feedback information including a pre-coding matrix indication
10 and a channel quality indication, and feeding the same back to a base station for scheduling.
[0015] One embodiment of the disclosure provides an apparatus for user pairing of a
MIMO communication system, comprising: a downlink channel feedback information
receiving unit configured to receive downlink channel feedback information from a user,
wherein the downlink channel feedback information includes a pre-coding matrix indication,
15 a channel quality indication, and a multi-user channel quality indication error, wherein the
multi-user channel quality indication error is used to reflect the difference in channel quality
indication between the situation of multi-user multiple input multiple output transmission and
the situation of single user multiple input multiple output transmission of the user; an initial
paired user selecting unit configured to select the user with the minimum multi-user channel
20 quality indication error from transmitting users as a paired user, the transmitting users include
all the current transmitting users which are allowed to enter a multi-user multiple input
multiple output transmission mode; a correlation calculating unit configured to calculate the
correlation of each paired user to each of other transmitting users, and selecting one or more
users as candidate paired user(s) according to the correlation; a paired user selecting unit
25 configured to select paired user(s) from the candidate paired user(s) according to the
multi-user channel quality indication error; and the correlation calculating unit and the paired
user selecting unit are configured to repeat their operations until a predetermined number of
paired users have been selected.
- 5 -
^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
• Sony Ref.: SP314891IN00
Our Ref.: OP 1211-06-0773
[0016] In addition, an embodiment of the disclosure further provides a user equipment
comprising the apparatus for feeding back downlink channel feedback information as
described above and a base station comprising the apparatus for user pairing as described
above, and a communication system comprising at least one above user equipment and at
5 least one above base station.
[0017] An embodiment of the disclosure also provides a computer program code when
executed by a computing device to cause the computing device to perform the processes of
any of above methods, a computer readable storage medium on which the computer program
code is stored, and a computer program product.
10 [0018] Those and other advantages of the disclosure will be more apparent by detail
explanations of the best embodiments of disclosure provided by referring to the Figure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The disclosure may be understood better by referring to description provided in
15 conjunction with the drawings, wherein the same or similar reference signs are used to
represent the same or similar components in all of the Figures. The Figures and the following
detailed description are included in the Description and form a part of the Description, and
they are used to further explain preferable embodiments of the disclosure and explain
principle and object of the disclosure by examples. In the Drawings:
20 [0020] Figure 1 is a schematic diagram illustrating the situation of SU-MIMO and the
situation of MU-MIMO;
[0021] Figure 2 is a flowchart illustrating a method for feeding back downlink channel
feedback information according to an embodiment of the disclosure;
[0022] Figure 3 is a flowchart illustrating a process for calculating the multi-user channel
25 quality indication error according to the signal to noise ratio according to an embodiment of
the disclosure;
[0023] Figure 4 is a flowchart illustrating a process for user pairing according to an
embodiment of the disclosure;
[0024] Figure 5 is a flowchart illustrating a communication method in a MIMO system
-6-
^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
-B Sony Ref.: SP314891IN00
OurRef.:OP1211-06-0773
according to an embodiment of the disclosure;
[0025] Figure 6 illustrates an apparatus for feeding back downlink channel feedback
information of a MIMO system according to an embodiment of the disclosure;
[0026] Figure 7 is a schematic diagram illustrating a multi-user channel quality indication
5 error calculating unit according to an embodiment of the disclosure;
[0027] Figure 8 illustrates an apparatus for user pairing in MU-MIMO transmission mode
in a MIMO system according to an embodiment of the disclosure; and
[0028] Figure 9 is a block diagram illustrating an example structure of a universal personal
computer that may implement the methods and/or apparatuses according to embodiments of
10 the disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0029] Example embodiments of the disclosure will be described in conjunction with the
Figures. For the sake of clearness and conciseness, the description does not describe all
15 features of the actual embodiments. However, it shall be understood that decisions specific to
embodiments have to be made in a procedure of developing such an actual embodiment to
achieve the specific object of the developer, for example, complying with limited conditions
relative to system and transaction, and those limited conditions may change in different
embodiments. In addition, it shall be understood that although the developing working may be
20 complex and time consuming, such a developing working is only routine for those skilled in
the art benefit from the disclosure of the disclosure.
[0030] In addition, it shall be noted that, to avoid blurring of the disclosure due to
unnecessary details, only device structures and/or process steps closely related to the solution
of the disclosure are illustrated in the drawings, and other details not closely related to the
25 disclosure are omitted.
[0031] Figure 2 is a flowchart illustrating a method for feeding back downlink channel
feedback information according to an embodiment of the disclosure.
[0032] As shown in Figure 2, at step S202, a user in a MIMO system calculates a multi-user
channel quality indication error of the user.
- 7 -
^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
•9 Sony Ref.: SP314891IN00
Our Ref: OP1211-06-0773
[0033] Herein, the multi-user channel quality indication error may reflect the error in
channel quality indication between the situation of MU-MIMO transmission and the situation
of SU-MIMO transmission of the user. Such error may be caused by the parameters difference
(such as the signal to noise ratio, synchronization difference, location difference and the like)
5 of the user in the MU-MIMO transmission.
[0034] Next, at step S204, the user in the MIMO system feeds the multi-user channel
quality indication error back to a base station along with the downlink channel feedback
information.
[0035] Herein, as specified in LTE, the downlink channel feedback information which the
10 user feeds back to the base station may include: the PMI for indicating a pre-coding matrix;
and CQI for selecting a modulation coding mode of transmission data by the base station.
[0036] Herein, the user may use various known methods to obtain the PMI and CQI in the
downlink channel feedback information.
[0037] For example, the user may find out a pre-coding matrix corresponding to the user
15 based on the measured channel information matrix, and then generate the PMI for
representing the pre-coding matrix. In addition, the user may obtain the value of related CQI
based on the measured signal to noise ratio, for example.
[0038] As can be seen, in the method for feeding back downlink channel feedback
information according to above embodiment, the multi-user channel quality indication error is
20 further fed back to the base station, so that the error in channel quality indication between the
situation of MU-MIMO transmission and the situation of SU-MIMO transmission of the user
may be reflected more accurately.
[0039] In this way, the user feeds more accurate downlink channel feedback information
back to the base station, so that the base station may obtain CQI and modulation coding mode
25 more suitable for the user in a more accurate manner. Therefore, the demodulation error code
rate of the user may be reduced in the communication system and the system performance
may be improved.
[0040] In above method, the multi-user channel quality indication error may be calculated
by considering various parameters and using any suitable method.
30 [0041] For example, in a specific embodiment of the disclosure, the multi-user channel
-8-
A English translation of PCT publication Sony China Ref.: CNPA10058IN00
-* Sony Ref.: SP314891IN00
Our Ref.: OP1211-06-0773
quality indication error may be calculated based on the signal to noise ratio.
[0042] Figure 3 is a flowchart illustrating a process for calculating the multi-user channel
quality indication error according to the signal to noise ratio according to an embodiment of
the disclosure.
5 [0043] As shown in Figure 3, a measuring is executed at step S302.
[0044] Specifically, a user may measure the channel state thereof, thereby to obtain channel
information matrix and the signal to noise ratio of the user.
[0045] The user may obtain the pre-coding matrix of the user based on the measured
channel information matrix.
10 [0046] For example, the pre-coding matrix may be obtained with the measured channel
information matrix based on the following equation (1).
[00471 b= M% rmx\H*wt\/\\H\\ (1)
i=\,...,B
[0048] In equation (1), H represents the measured channel information matrix of the user,
Wj represents the pre-coding matrix, i represents the location of the pre-coding matrix in
15 codebook, by which the pre-coding matrix can be obtained from the codebook, and the size of
the codebook is B.
[0049] Next, at step S3 04, quantization error may be calculated.
[0050] Herein, the quantization error is a parameter reflecting the error between the
measured channel information matrix and the obtained pre-coding matrix.
20 [0051] The quantization error may be represented according to the channel information
matrix and the pre-coding matrix.
[0052] For example, the quantization error may be calculated according to the following
equation (2).
\H"wi[0053] e _ | | / / | | x | | w , . | | <2>
25 [0054] In equation (2), the meaning of H and Wj are the same to that in equation (1), and e
-9-
| | | English translation of PCT publication Sony China Ref.: CNPA10058IN00
*** Sony Ref.: SP314891IN00
OurRef.:OP1211-06-0773
represents the quantization error.
[0055] Next, as shown in Figure 3, at step S3 06, the minimum interference level to the user
is calculated.
[0056] Specifically, out of all the potential paired users to which the user may pair, the user
5 with the minimum interference level to the user is found out, and the minimum interference
level is calculated.
[0057] Herein, the potential paired users may be users meeting an orthogonal condition, for
example, and the orthogonal condition may be that the pre-coding matrix corresponding to a
potential paired user is orthogonal to the pre-coding matrix of the user, for example.
10 [0058] For example, the minimum interference level may be calculated according to the
following equation (3).
[0059, °=™pJ\H"w,\) (3)
[0060] In equation (3), Wj represents the pre-coding matrix of any potential paired user, the
meaning of H and w; are the same to that in equation (1), and a represents the minimum
15 interference level. In equation (3), Wj*w;H=0 represents the orthogonal condition.
[0061] Next, as shown in Figure 3, at step S308, the signal to noise ratio of the user in the
situation of multi-user is calculated.
[0062] Specifically, the above quantization error, the measured minimum interference level
and the signal to noise ratio may be used to calculate the signal to noise ratio of the user in the
20 situation of multi-user.
[0063] For example, the signal to noise ratio in the situation of multi-user may be calculated
based on the following equation (4).
SNR/2x(ef
,oo«4] ^ K « " - » ' ^ - s m / 2 x a 2 + l (4)
[0065] In equation (4), SNR represents the signal to noise ratio measured by the user,
25 SNRMU-MIMO represents the evaluated signal to noise ratio of the user in the situation of
multi-user, e represents the quantization error, and a represents the minimum interference
level.
-10-
j l English translation of PCT publication Sony China Ref.: CNPA10058IN00
^ Sony Ref.: SP314891IN00
Our Ref: OP1211-06-0773
[0066] Next, with reference to Figure 3, at step S310, multi-user channel quality indication
error of the user in the situation of multi-user MIMO transmission may be calculated.
[0067] Specifically, the multi-user channel quality indication error may be calculated based
on the signal to noise ratio measured by the user and the above calculated signal to noise ratio
5 in MU-MIMO mode.
[0068] For example, the multi-user channel quality indication error may be calculated based
on the following equation (5).
100691 y = CQI(SNR) - CQJ(SNRMU_UIU0) (5)
[0070] In equation (5), SNR represents the signal to noise ratio measured by the user,
10 SNRMU-MIMO represents the calculated signal to noise ratio of the user in the situation of
MU-MIMO transmission; CQI( ) represents channel quality indication function related to the
signal to noise ratio; and V represents the multi-user channel quality indication error of the
user.
[0071] In this way, the multi-user channel quality indication error of the user in the situation
15 of MU-MIMO transmission may be calculated based on the signal to noise ratio.
[0072] In the above description, the calculation of the multi-user channel quality indication
error is explained by only taking the signal to noise ratio as an example, however, the above
description is only an example, and the disclosure is not limited to this. For example, the
calculation of the multi-user channel quality indication error may be executed by considering
20 the influence of the other parameters (for example, time parameters (such as time
synchronization difference), location parameters, and the like). For example, the calculation
of the multi-user channel quality indication error may also be implemented based on time
parameters, or based on a combination of time parameters and the signal to noise ratio.
[0073] Correspondingly, an embodiment of the disclosure also provides a method of user
25 pairing in MU-MIMO transmission mode of a MIMO system which is implemented at base
station side.
[0074] Figure 4 is a flowchart illustrating a method for user pairing in MU-MIMO
transmission mode in a MIMO system according to an embodiment of the disclosure.
[0075] As shown in Figure 4, at step S402, a base station receives downlink channel
-11-
•
English translation of PCT publication Sony China Ref.: CNPA10058IN00
SonyRef.:SP314891IN00
OurRef.:OP1211-06-0773
feedback information from a user.
[0076] In embodiments of the disclosure, the downlink channel feedback information may
include pre-coding matrix indication, channel quality indication, and multi-user channel
quality indication error, wherein the multi-user channel quality indication error is used to
5 reflect the difference in channel quality indication between the situation of multi-user multiple
input multiple output transmission and the situation of single user multiple input multiple
output transmission of the user.
[0077] As a preferable example, the multi-user channel quality indication error may be
calculated with the method according to the above embodiments of the disclosure.
10 [0078] Next, at step S404, the base station selects an initial paired user from transmitting
users.
[0079] Preferably, the base station may select the user with the minimum multi-user channel
quality indication error from the transmitting users as an initial paired user, for example.
[0080] In this specification, the transmitting users may be defined as one or more users
15 which are allowed to enter a multi-user multiple input multiple output transmission mode out
of the users being transmitting data currently.
[0081] The base station may decide whether a certain user may enter the MU-MIMO
transmission mode (that is, decide the transmitting user) by using an existing decision strategy,
for example, based on channel condition, rate requirement, current resource allocation, and
20 the like of the user.
[0082] Next, at step S406, the base station calculates the correlation of each paired user to
each of other transmitting users, and selects one or more users from the other transmitting
users as candidate paired user(s) according to the correlation.
[0083] The correlation between two users may be calculated by using any known method.
25 [0084] For example, the correlation of each paired user to each of other transmitting users
may be calculated by using the following equation (6).
_\M\w[j_
[0085] P ~ M n 7, [7 (6)
II w, || x || w21|
- 12-
^Jk English translation of PCT publication Sony China Ref.: CNPA10058IN00
* Sony Ref.: SP314891IN00
Our Ref.: OP 1211-06-0773
[0086] In the equation (6), wl represents the pre-coding matrix of a paired user, and w2
represents the pre-coding matrix of a transmitting user, the pre-coding matrix of each user
may be obtained according to PMI in the downlink channel feedback information fed back by
the each user.
5 [0087] After calculating the correlation, the base station may select one or more users from
the other transmitting users as the candidate paired user(s) according to the calculated
correlation.
[0088] In an example, the base station may select one or more users with the correlation
below a predetermined threshold as the candidate paired user(s).
10 [0089] In another example, the base station may also select one or more users with the
minimum correlation as the candidate paired user(s).
[0090] Next, at step S408, the base station select a paired user from the candidate paired
user(s).
[0091] Specifically, the base station may select according to the multi-user channel quality
15 indication error of individual candidate paired user(s).
[0092] For example, the base station select a candidate paired user with the minimum
multi-user channel quality indication error in the fed back downlink channel feedback
information from the candidate paired user(s) as the paired user.
[0093] Next, at step S410, the base station decides whether a predetermined number of
20 paired users have been selected.
[0094] If the number of the paired user selected by the base station has not reached the
predetermined number, the steps S406 and S408 are repeated in order to select other paired
users from the transmitting users, until the required number of paired users has been selected.
[0095] If the number of the paired user selected by the base station has reached the
25 predetermined number, the pairing process ends.
[0096] In the above user pairing process, the base station uses the multi-user channel
quality indication error fed back by the user. In this way, in the MU-MIMO transmission
mode, the base station may implement more accurate pairing. Therefore, the system
performance may be improved.
- 13-
<£ English translation of PCT publication Sony China Ref.: CNPA10058IN00
™ Sony Ref.: SP314891IN00
Our Ref.: OP 1211-06-0773
[0097] In addition, an embodiment of the disclosure provides a communication method in a
MIMO system with the method for feeding back downlink channel feedback information
according to the above embodiments of the disclosure and the method for user pairing
according to the above embodiments of the disclosure.
5 [0098] Figure 5 is a flowchart illustrating a communication method in a MIMO system
according to an embodiment of the disclosure.
[0099] As shown in Figure 5, at step S502, a user feeds downlink channel feedback
information back to a base station.
[00100] For example, the user may feed the downlink channel feedback information back to
10 the base station according to the method for feeding back downlink channel feedback
information according to the above embodiments of the disclosure.
[00101] In this case, the downlink channel feedback information fed back by the user may
include PMI, CQI, and multi-user channel quality indication error, wherein the multi-user
channel quality indication error may reflect the difference in channel quality indication
15 between the situation of MU-MIMO transmission and the situation of SU-MIMO
transmission of the user.
[00102] Specifically, the user may calculate the multi-user channel quality indication error
according to equations (l)-(5).
[00103] Next, at step S504, the base station decides whether a SU-MIMO transmission mode
20 or a MU-MIMO transmission mode is used.
[00104] The base station may decide whether the SU-MIMO transmission mode or the
MU-MIMO transmission mode is used according to an existing decision strategy.
[00105] For example, the base station may decide whether the SU-MIMO transmission mode
or the MU-MIMO transmission mode is used according to one or more factors of channel
25 condition, rate requirement, current resource allocation of the user, and the like.
[00106] With reference to Figure 5, in case that the base station decides to use the SU-MIMO
transmission mode, the base station may obtain a pre-coding matrix based on pre-coding
matrix indication in the downlink channel feedback information fed back by the user, and
select a modulation coding mode for the user based on the CQI in the downlink channel
30 feedback information, and the base station does not use the multi-user channel quality
- 14-
M| English translation of PCT publication Sony China Ref.: CNPA10058IN00
-* Sony Ref. :SP314891IN00
Our Ref: OP1211-06-0773
indication error for the MU-MIMO transmission mode in the downlink channel feedback
information fed back by the user.
[00107] With reference to Figure 5, in case that the base station decides to use the
MU-MIMO transmission mode, at step S508, the base station may select a paired user for the
5 user.
[00108] For example, the base station may select the paired user for the user according to the
method for user pairing according to the above embodiments of the disclosure. As for the
detailed specific of the process for selecting the paired user, the above description with
respect to Figure 4 may be referred to, and thus will not be repeated for simplicity of the
10 specification.
[00109] Next, at step S510, the base station calculates the pre-coding matrix in the
MU-MIMO transmission mode and selects the suitable modulation coding mode for
individual paired users.
[00110] For example, the base station may obtain the pre-coding matrix in the MU-MIMO
15 transmission mode based on the pre-coding matrixes of individual paired users (which can be
obtained with the PMI fed back by individual paired users), and select the modulation coding
mode for individual paired users based on the CQI and multi-user channel quality indication
error of individual paired users.
[00111] For example, the base station may obtain the pre-coding matrix corresponding to
20 each paired user according to the PMI of the each paired user, and then the base station may
further obtain the pre-coding matrix in the MU-MIMO transmission mode based on these
pre-coding matrixes.
[00112] For example, the pre-coding matrix in the MU-MIMO transmission mode may be
obtained based on the following equation (7)
25 [00113] G =[wl,w2]([wl,w2]H[wl,w2]Y1 (7)
[00114] In equation (7), G represents the pre-coding matrix in the MU-MIMO transmission
mode, wl represents the pre-coding matrix corresponding to the user, and w2 represents the
pre-coding matrix corresponding to the paired user.
[00115] In addition, the base station may calculate the CQI of a paired user in the
- 1 5 -
te English translation of PCT publication Sony China Ref: CNPA10058IN00
-m Sony Ref. :SP314891IN00
Our Ref.: OP1211-06-0773
MU-MIMO mode based on the CQI and the multi-user channel quality indication error in the
downlink channel feedback information of the paired user, and accordingly select a
modulation coding mode for the user.
[00116] For example, the CQI of the user in the MU-MIMO mode may be calculated
5 according to the CQI and the multi-user channel quality indication error according to the
following equation (8).
[001171 *J MU-MIMO = *"££•* ~* (g[00118] In equation (8), CQIMU-MIMO represents the channel quality indication of the paired
user in the MU-MIMO transmission mode, CQI represents the value of the CQI included in
10 the downlink channel feedback information of the paired user, and V represents the multi-user
channel quality indication error in the downlink channel feedback information of the paired
user.
[00119] In this way, in the MIMO system using the communication method according to the
above embodiments of the disclosure, since the difference in channel quality indication
15 between the situation of MU-MIMO transmission and the situation of SU-MIMO
transmission of the user has been considered, the demodulation bit error rate of the user in the
MIMO transmission mode can be reduced and the system performance can be improved.
[00120] In addition, according to the embodiments of the disclosure, apparatuses
corresponding to the methods are also provided.
20 [00121] Figure 6 illustrates an apparatus for feeding back downlink channel feedback
information of a MIMO system according to an embodiment of the disclosure.
[00122] As shown in Figure 6, the apparatus for feeding back downlink channel feedback
information 600 according to an embodiment of the disclosure comprises a multi-user channel
quality indication error calculating unit 602 and a downlink channel feedback information
25 feeding back unit 604.
[00123] The multi-user channel quality indication error calculating unit 602 may calculate
multi-user channel quality indication error of a user.
[00124] Herein, the multi-user channel quality indication error may reflect the error in
channel quality indication between the situation of MU-MIMO transmission and the situation
-16-
^ English translation of PCT publication Sony China Ref: CNPA10058IN00
- * Sony Ref.: SP314891IN00
Our Ref.: OP 1211-06-0773
of SU-MIMO transmission of the user. Such error may be caused by the parameters difference
(such as the signal to noise ratio, synchronization difference, location difference and the like)
of the user in the MU-MIMO transmission.
[00125] The downlink channel feedback information feeding back unit 604 may add the
5 multi-user channel quality indication error to downlink channel feedback information
including PMI and CQI, and feeding the same back to a base station for scheduling.
[00126] As can be seen, in the apparatus for feeding back downlink channel feedback
information according to above embodiment, the multi-user channel quality indication error is
further fed back to the base station, so that the error in channel quality indication between the
10 situation of MU-MIMO transmission and the situation of SU-MIMO transmission of the user
may be reflected more accurately.
[00127] In this way, with this apparatus for feeding back downlink channel feedback
information, the user may feed more accurate downlink channel feedback information back to
the base station, so that the base station may obtain CQI and modulation coding mode more
15 suitable for the user in a more accurate manner. Therefore, the demodulation error code rate of
the user may be reduced in the communication system and the system performance may be
improved.
[00128] In the apparatus for feeding back downlink channel feedback information of Figure
6, the multi-user channel quality indication error calculating unit 602 may calculate the
20 multi-user channel quality indication error based on various suitable parameters.
[00129] For example, in an embodiment of the disclosure, the multi-user channel quality
indication error calculating unit may calculate the multi-user channel quality indication error
based on the signal to noise ratio.
[00130] Figure 7 is a schematic diagram illustrating a multi-user channel quality indication
25 error calculating unit according to an embodiment of the disclosure.
[00131] As shown in Figure 7, the multi-user channel quality indication error calculating unit
700 comprises: a measuring unit 702, a quantization error calculating unit 704, a minimum
interference level calculating unit 706, a multi-user mode signal to noise ratio calculating unit
708, and an error calculating unit 710.
30 [00132] Herein, the measuring unit 702 may measure channel state of the user, thereby to
- 17-
» English translation of PCT publication Sony China Ref: CNPA10058IN00
Sony Ref.:SP314891IN00
Our Ref.: OP1211-06-0773
obtain channel information matrix and the signal to noise ratio of the user.
[00133] The quantization error calculating unit 704 may calculate quantization error, wherein
the quantization error is a parameter reflecting the error between the measured channel
information matrix and the obtained pre-coding matrix.
5 [00134] For example, the quantization error may be calculated according to equation (2) as
mentioned above.
[00135] The minimum interference level calculating unit 706 may find out a user with the
minimum interference level to the user out of all the potential paired users to which the user
may pair, and calculate the minimum interference level.
10 [00136] For example, the minimum interference level may be calculated according to
equation (3) as mentioned above.
[00137] The multi-user mode signal to noise ratio calculating unit 708 may calculate the
signal to noise ratio of the user in the situation of multi-user.
[00138] Specifically, the signal to noise ratio of the user in the situation of multi-user may be
15 calculated by using the quantization error, the minimum interference level, and the measured
signal to noise ratio.
[00139] For example, the signal to noise ratio in the situation of multi-user may be calculated
according to equation (4) as mentioned above.
[00140] The error calculating unit 710 may calculate the multi-user channel quality
20 indication error in the multi-user MIMO transmission of the user.
[00141] Specifically, the error calculating unit 710 may calculate the multi-user channel
quality indication error based on the signal to noise ratio measured by the user and the above
calculated signal to noise ratio of the user in the multi-user MIMO transmission.
[00142] For example, the multi-user channel quality indication error may be calculated
25 according to equation (5) as mentioned above.
[00143] In this way, the multi-user channel quality indication error calculating unit according
to the embodiments of the disclosure may calculate the multi-user channel quality indication
error in the situation of multi-user MIMO transmission of the user based on the signal to noise
ratio.
- 18-
^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
^ Sony Ref.: SP314891INOO
Our Ref.: OP 1211-06-0773
[00144] In above description, the multi-user channel quality indication error calculating unit
calculates the multi-user channel quality indication error based on the signal to noise ratio,
however, the above description is only an example, and the disclosure is not limited to this.
For example, the calculation of the multi-user channel quality indication error calculating unit
5 may also be based on the other parameters (for example, time parameters, location parameters,
and the like). For example, the calculation of the multi-user channel quality indication error
calculating unit may be based on time parameters, or based on a combination of time
parameters and the signal to noise ratio.
[00145] Correspondingly, an embodiment of the disclosure also provides an apparatus for
10 user pairing in MU-MIMO transmission mode in a MIMO system.
[00146] Figure 8 illustrates an apparatus for user pairing in MU-MIMO transmission mode
in a MIMO system according to an embodiment of the disclosure.
[00147] As shown in Figure 8, the apparatus for user pairing 800 according to an
embodiment of the disclosure comprises: a downlink channel feedback information receiving
15 unit 802, initial paired user selecting unit 804, a correlation calculating unit 806, and a paired
user selecting unit 808.
[00148] Herein, the downlink channel feedback information receiving unit 802 may receive
downlink channel feedback information from a user.
[00149] In the embodiments of the disclosure, the downlink channel feedback information
20 received by the base station from the user may include PMI, CQI, and multi-user channel
quality indication error, wherein the multi-user channel quality indication error is used to
reflect the difference in channel quality indication between the situation of multi-user multiple
input multiple output transmission and the situation of single user multiple input multiple
output transmission of the user.
25 [00150] As a preferable example, the multi-user channel quality indication error may be
calculated with the method according to the above embodiments of the disclosure.
[00151] The initial paired user selecting unit 804 may select an initial paired user from
transmitting users.
[00152] Preferably, the initial paired user selecting unit 804 may select the user with the
30 minimum multi-user channel quality indication error from the transmitting users as an initial
-19-
w English translation of PCT publication Sony China Ref.: CNPA10058IN00
^ Sony Ref.: SP314891IN00
Our Ref: OP 1211-06-0773
paired user, for example.
[00153] In this specification, the transmitting users may be defined as one or more users
which are allowed to enter a MU-MIMO transmission mode out of the users being
transmitting data currently.
5 [00154] The base station may decide whether a certain user may enter the MU-MIMO
transmission mode by using an existing decision strategy, for example, based on channel
condition, rate requirement, current resource allocation, and the like of the user.
[00155] The correlation calculating unit 806 may calculate the correlation of each paired user
to each of other transmitting users, and select one or more users as candidate paired user(s)
10 according to the correlation.
[00156] The correlation between two users may be calculated by using any known method.
[00157] For example, the correlation of each paired user to each of other transmitting users
may be calculated by using equation (6) as mentioned above.
[00158] After calculating the correlation, the correlation calculating unit 806 may select one
15 or more users from the other transmitting users as the candidate paired user(s) according to
the calculated correlation.
[00159] In an example, the correlation calculating unit 806 may select one or more users
with the correlation below a predetermined threshold as the candidate paired user(s).
[00160] In another example, the correlation calculating unit 806 may also select one or more
20 users with the minimum correlation as the candidate paired user(s).
[00161] Next, with reference to Figure 8, the paired user selecting unit 808 may select a
paired user from the candidate paired user(s).
[00162] Specifically, the base station may select according to the multi-user channel quality
indication error of individual candidate paired user(s).
25 [00163] For example, the base station may select a candidate paired user with the minimum
multi-user channel quality indication error in the fed back downlink channel feedback
information as the paired user.
[00164] As shown in Figure 8, the correlation calculating unit 806 and the paired user
selecting unit 808 may repeat their operations until a predetermined number of paired users
-20-
jb English translation of PCT publication Sony China Ref.: CNPA10058IN00
** Sony Ref.: SP314891IN00
OurRef.:OP1211-06-0773
have been selected.
[00165] In the above user pairing process, the base station uses the multi-user channel
quality indication error fed back by the user. In this way, in the MU-MIMO transmission
mode, the base station may implement more accurate pairing. Therefore, the system
5 performance may be improved.
[00166] The above embodiments are provided to facilitate understanding of the conception
of the disclosure. However, the above description is only an example, and the disclosure is not
limited to this. Various modifications may be made without departing from the conception of
the disclosure.
10 [00167] For example, in above description, the downlink channel feedback information fed
by the user back to the base station only includes one PMI indication (for example,
corresponding to the feedback scheme of single codebook). However, the disclosure is not
limited to this, and the method (apparatus) for feeding back downlink channel feedback
information and the method (apparatus) for user pairing according to the embodiments of the
15 disclosure may also be applied to other feedback schemes.
[00168] APPLICATION EXAMPLE OF DUAL CODEBOOK FEEDBACK
[00169] According to the specifications of LTE-A, in 2-antenna or 4-antenna base station
configurations, a user feeds one PMI back to a base station (that is, single codebook feedback
20 scheme), and the PMI corresponds to one pre-coding matrix. In an 8-antenna base station
configuration, a user feeds two PMI back to a base station (that is, dual codebook feedback
scheme), wherein one PMI corresponds to transmission bandwidth information of the
downlink channel and the other PMI corresponds to sub-band information in the transmission
bandwidth of the downlink channel; the pre-coding matrix is decided by both matrixes to
25 which these two PMI correspond.
[00170] The method (apparatus) for feeding back downlink channel feedback information
according to the embodiments of the disclosure and the method (apparatus) for user pairing
according to the embodiments of the disclosure may also be applied to the above dual
codebook feedback scheme.
30 [00171] In case of using the dual codebook feedback scheme, the process of calculating
-21-
± English translation of PCT publication Sony China Ref.: CNPA10058IN00
~ Sony Ref.: SP314891IN00
Our Ref.: OP 1211-06-0773
multi-user channel quality indication error by the user is the same to the process of single
codebook feedback scheme as described above in connection with Figure 3 using equations
(l)-(5).
[00172] In feeding back the downlink channel feedback information, the difference between
5 the dual codebook feedback scheme and the single codebook feedback scheme is only that the
feedback formats are different, that is, the downlink channel feedback information fed by the
user back to the base station includes two PMI, CQI, and the multi-user channel quality
indication error in the dual codebook feedback scheme.
[00173] On the other hand, in case of using the dual codebook feedback scheme, the process
10 of user pairing in the MU-MIMO transmission mode by the base station is the same to the
process as described above in connection with Figure 4.
[00174] In addition, the method (apparatus) for feeding back downlink channel feedback
information and the method (apparatus) for user pairing according to the embodiments of the
disclosure are not limited to the above single codebook feedback scheme and dual codebook
15 feedback scheme, and may also be extended to be applied to more other feedback schemes.
[00175] APPLICATION EXAMPLE OF OTHER FEEDBACK SCHEMES
[00176] For example, in another known feedback scheme, the transmission bandwidth is
further divided into at least one sub-band. In this case, the PMI portion of downlink channel
20 feedback information fed by a user back to a base station may include PMI corresponding to
the transmission bandwidth information, and at least one sub-band PMI individually
corresponding to the at least one sub-band in the transmission bandwidth.
[00177] The method (apparatus) for feeding back downlink channel feedback information
according to the embodiments of the disclosure and the method (apparatus) for user pairing
25 according to the embodiments of the disclosure may also be applied to the above feedback
scheme.
[00178] In the above feedback scheme (the PMI portion includes at least one sub-band PMI
corresponding to the at least one sub-band in the transmission bandwidth), the user may use
the process according to the above embodiments of the disclosure (for example, with
30 reference to Figure 3 and equations (l)-(5)) to calculate corresponding multi-user channel
- 2 2 -
^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
*™ Sony Ref.: SP314891IN00
Our Ref: OP 1211-06-0773
quality indication error for each sub-band.
[00179] Therefore, in the above feedback scheme, the downlink channel feedback
information fed by the user back to the base station includes: PMI portion, which includes the
PMI corresponding to the transmission bandwidth information of the downlink channel, and
5 at least one sub-band PMI corresponding to the at least one sub-band in the transmission
bandwidth of the downlink channel; at least one multi-user channel quality indication error
individually corresponding to the at least one sub-band; and at least one CQI individually
corresponding to the at least one sub-band.
[00180] Herein, the PMI and CQI corresponding to each sub-band may be obtained based on
10 the SNR and channel information matrix measured by the user for each sub-band.
[00181] On the other hand, in the above feedback scheme, the process of user pairing in the
MU-MIMO transmission mode by the base station is the same to the process as described
above in connection with Figure 4.
[00182] Obviously, in addition to the two feedback schemes proposed above as examples,
15 the method (apparatus) for feeding back downlink channel feedback information according to
the embodiments of the disclosure and the method (apparatus) for user pairing according to
the embodiments of the disclosure may also be applied to other feedback schemes or the
feedback schemes which may occur in future, and the description thereof will be omitted for
simplicity of the specification.
20 [00183] In addition, an embodiment of the disclosure provides a communication terminal
comprising the apparatus for feeding back downlink channel feedback information according
to the embodiments of the disclosure. In this way, the terminal according to the embodiments
of the disclosure may feed the multi-user channel quality indication error back to the base
station, so that the error in channel quality indication between the situation of MU-MIMO
25 transmission and the situation of SU-MIMO transmission of the user may be reflected more
accurately. Therefore, the system performance may be improved.
[00184] An embodiment of the disclosure also provides a base station comprising the
apparatus for user pairing in MU-MIMO transmission mode in a MIMO system according to
the embodiments of the disclosure. In this way, the base station according to the embodiments
30 of the disclosure may implement more accurate pairing in the MU-MIMO transmission mode.
- 2 3 -
± English translation of PCT publication Sony China Ref.: CNPA10058IN00
" • Sony Ref. :SP314891IN00
Our Ref: OP 1211-06-0773
Therefore, the system performance may be improved.
[00185] Further, an embodiment of the disclosure provides a MIMO communication system
comprising at least one communication terminal according to the above embodiments of the
disclosure and at least one base station according to the above embodiments of the disclosure.
5 In this way, the MIMO system according to the embodiments of the disclosure may
implement more accurate pairing in the MU-MIMO transmission mode. Therefore, the system
performance may be improved.
[00186] In addition, it shall be understood that various examples and embodiments described
herein are exemplary, and the disclosure is not limited to this. In the specification, terms
10 "first", "second", etc. are only for distinguishing the features described by them literally in
order to illustrate the disclosure in a manner of clarity. Therefore, it shall not deem them to
have any limited meaning.
[00187] Various component modules and units of the above apparatuses may be configured
by software, firmware, hardware or their combination thereof. Specific means and manners
15 that may be used by the configuration are well known to those skilled in the art, and details
are omitted here. In case of implementing the base station by software or firmware, program
constituting the software may be mounted to a computer having a dedicated hardware
structure from a storage medium or network (for example, the universal computer 900 as
illustrated in Fig. 9), when the computer is mounted with various program, the computer may
20 execute various functions.
[00188] In Fig. 9, a central processing unit (CPU) 901 perform various processes according
to the program stored in the Read-Only Memory (ROM) 902 or programs load from the
storage unit 908 to the Random Access Memory (RAM) 903. In the RAM 903, store also data
required when the CPU 901 performs various processes. CPU 901, ROM 902 and RAM 903
25 are connected from one to another via bus 904. Input/output interface 905 is also connected to
the bus 904.
[00189] The following components are connected to the input/output interface 905: input
unit 906 (including keyboard, mouse, etc.); output unit 907 (including display, such as
cathode ray tube (CRT), liquid crystal display (LCD), etc., and speakers and so on); storage
30 unit 908 (including hard disc, etc.); and communication part 909 (including network interface
cards such as LAN cards, modems and so on). The communication unit 909 performs
-24-
j ^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
^ Sony Ref.: SP314891IN00
Our Ref: OP 1211-06-0773
communication process via network like the internet. According to requirements, drive 910 is
also connected to the input/output interface 905. Detachable medium 911 such as disc, CD,
magneto-optical disc, semiconductor memory, and so on is installed on the drive 910 based on
requirements, such that the computer program read out therefrom is installed in the storage
5 unit 908 based on requirements.
[00190] In case of implementing the above processes by software, programs constituting the
software are installed from a network like the Internet or from a storage medium like the
detachable medium 911.
[00191] Those skilled in the art should be understood that such storage medium is not limited
10 to the detachable medium 911 which is stored with programs and distributes separate from the
method to provide a user with program as illustrated in Fig. 9. The example of the detachable
medium 911 includes disc (including floppy disc (registered marks)), CD (including CD read
only memory (CD-ROM) and digital versatile disc (DVD)), magneto-optical disc (including
mini-disc (MD) (registered marks)) and semiconductor memory. Alternatively, the storage
15 medium may be ROM 902, or hard disc included in the storage unit 908 in which a program
is stored and the program is distributed to a user with the method including the same.
[00192] The disclosure also provides a program product storing machine readable instruction
code. When read and executed by a machine, the instruction code may implement the method
according to the embodiment of the disclosure.
20 [00193] Correspondingly, a storage medium for carrying the program code storing the
machine readable instruction code is also included in the disclosure. The storage medium
includes, but not limited to, Floppy disk, CD-ROMs, magneto-optical disk, memory card,
memory stick, etc.
[00194] At last, it needs to be explained that the technical terms "comprise/include" or other
25 variants intend to cover non-exclusion inclusion, such that process, method, article of a series
of elements are comprised, or the device includes not only those elements, but also other
elements that are not listed evidently or further comprises the process, method, article or
elements inherent in the device. In addition, in case of no more limitations, the elements
defined by the sentence "comprising a..." do not exclude a case that there are other the
30 same elements in the process, method, article or device including the elements.
-25-
*L. English translation of PCT publication Sony China Ref.: CNPA10058IN00
^ Sony Ref.: SP314891IN00
Our Ref.: OP 1211-06-0773
[00195] Although embodiments of the disclosure have been described in detail by combining
with the Figure, it shall be understood that the embodiments described above are only used to
illustrate the disclosure, and do not limit the disclosure. For those skilled in the art, the
embodiments may be changed in various manners without departing from the substance and
5 scope of the disclosure. Therefore, the scope of the disclosure is only defined by the attached
claims and its equivalent meanings.

CLAIMS
1. A method for feeding back downlink channel feedback information of a Multiple Input
Multiple Output, MIMO, communication system, comprising:
calculating a multi-user channel quality indication error of a user in the system by the
5 user, wherein the multi-user channel quality indication error is used to reflect the difference in
channel quality indication between the situation of multi-user multiple input multiple output
transmission and the situation of single user multiple input multiple output transmission of the
user; and
adding the multi-user channel quality indication error to the downlink channel feedback
10 information including a pre-coding matrix indication and a channel quality indication, and
feeding the same back to a base station for scheduling.
2. The method according to claim 1, wherein the calculating the multi-user channel
quality indication error comprises calculating the multi-user channel quality indication error
based on signal to noise ratio of the user.
15 3. The method according to claim 2, wherein the calculating the multi-user channel
quality indication error comprises:
measuring a channel state of the user to obtain a channel information matrix and the
signal to noise ratio;
calculating a quantization error according to the channel information matrix and a
20 pre-coding matrix obtained based on the channel information matrix;
finding out channel with the minimum interference level from channels orthogonal to the
channel of the user;
calculating the signal to noise ratio of the user in the situation of multi-user multiple
input multiple output transmission; and
25 calculating the multi-user channel quality indication error according to the measured
signal to noise ratio and the calculated signal to noise ratio of the user in the situation of
multi-user multiple input multiple output transmission.
4. The method according to claim 3, wherein the calculating the signal to noise ratio of
the user in the situation of multi-user multiple input multiple output transmission comprises:
- 2 7 -
^ English translation of PCT publication Sony China Ref.: CNPAIOOSSINOO
^ Sony Ref.: SP314891IN00
Our Ref :0P1211-06-0773
calculating the signal to noise ratio of the user in the situation of multi-user multiple
input multiple output transmission by using the quantization error, the minimum interference
level, and the measured signal to noise ratio.
5. The method according to claim 1, wherein the pre-coding matrix indication
5 corresponds to one pre-coding matrix in 2-antenna and 4-antenna base station configurations;
and the pre-coding matrix indication comprises a first pre-coding matrix indication
corresponding to feedback bandwidth information of the downlink channel and a second
pre-coding matrix indication corresponding to sub-band information in the feedback
bandwidth of the downlink channel in an 8-antenna base station configuration.
10 6. The method according to claim 5, wherein the second pre-coding matrix indication
comprises at least one sub-band pre-coding matrix indication individually corresponding to at
least one sub-band, the multi-user channel quality indication error comprises at least one
sub-band multi-user channel quality indication error individually corresponding to the at least
one sub-band, and the channel quality indication comprises at least one sub-band channel
15 quality indication individually corresponding to the at least one sub-band.7. A method for user
pairing in a Multiple Input Multiple Output, MIMO, communication system, comprising:
a downlink channel feedback information receiving step of receiving downlink channel
feedback information from a user of the communication system, wherein the downlink
channel feedback information includes a pre-coding matrix indication, a channel quality
20 indication, and a multi-user channel quality indication error, and wherein the multi-user
channel quality indication error is used to reflect the difference in channel quality indication
between the situation of multi-user multiple input multiple output transmission and the
situation of single user multiple input multiple output transmission of the user;
an initial paired user selecting step of selecting the user with the minimum multi-user
25 channel quality indication error from transmitting users as an initial paired user, wherein the
transmitting users include all the current transmitting users which are allowed to enter
multi-user multiple input multiple output transmission mode;
a correlation calculating step of calculating the correlation of each paired user to each of
other transmitting users, and selecting one or more users from the other transmitting users as
30 candidate paired user(s) according to the correlation;
- 2 8 -
jjj^ English translation of PCX publication Sony China Ref.: CNPA10058IN00
^ Sony Ref.: SP314891IN00
Our Ref: OP 1211-06-0773
a paired user selecting step of selecting paired user(s) from the candidate paired user(s)
according to the multi-user channel quality indication error; and
repeating the correlation calculating step and the paired user selecting step until a
predetermined number of paired users have been selected.
5 8. The method according to claim 7, wherein the pre-coding matrix indication
corresponds to one pre-coding matrix in 2-antenna and 4-antenna base station configurations;
and the pre-coding matrix indication comprises a first pre-coding matrix indication
corresponding to feedback bandwidth information of the downlink channel and a second
pre-coding matrix indication corresponding to sub-band information in the feedback
10 bandwidth of the downlink channel in an 8-antenna base station configuration.
9. The method according to claim 8, wherein the second pre-coding matrix indication
comprises at least one sub-band pre-coding matrix indication individually corresponding to at
least one sub-band, the multi-user channel quality indication error comprises at least one
sub-band multi-user channel quality indication error individually corresponding to the at least
15 one sub-band, and the channel quality indication comprises at least one sub-band channel
quality indication individually corresponding to the at least one sub-band.
10. A method for communication in a Multiple Input Multiple Output, MIMO, system,
comprising:
feeding downlink channel feedback information back to a base station by a user;
20 deciding by the base station whether a single user multiple input multiple output
transmission mode or a multi-user multiple input multiple output transmission mode is used,;
obtaining a pre-coding matrix of the user by using a pre-coding matrix indication in the
fed back downlink channel feedback information, and selecting a modulation coding mode for
the user by using a channel quality indication in the fed back downlink channel feedback
25 information, by the base station, in case of using the single user multiple input multiple output
transmission mode; and
executing pairing for the user, obtaining a pre-coding matrix for the multi-user multiple
input multiple output transmission mode based on the pre-coding matrix indication in the
downlink channel feedback information fed back by the paired user(s), and selecting a
30 modulation coding mode corresponding to each user based on the channel quality indication
-29-
^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
• Sony Ref.: SP31489IINOO
Our Ref :0P1211-06-0773
and the multi-user channel quality indication error in the downlink channel feedback
information fed back by the each user, by the base station, in case of using the multi-user
multiple input multiple output transmission mode;
wherein, the user feeds the downlink channel feedback information back to the base
5 station through a method comprising:
calculating multi-user channel quality indication error of a user in the system by the
user, wherein the multi-user channel quality indication error is used to reflect the difference in
channel quality indication between the situation of multi-user multiple input multiple output
transmission and the situation of single user multiple input multiple output transmission of the
10 user; and
adding the multi-user channel quality indication error to the downlink channel
feedback information including the pre-coding matrix indication and the channel quality
indication, and feeding the same back to a base station for scheduling,
the base station executes pairing for the user through a method comprising:
15 a downlink channel feedback information receiving step of receiving the downlink
channel feedback information from a user of the system, wherein the downlink channel
feedback information includes the pre-coding matrix indication, the channel quality indication,
and the multi-user channel quality indication error;
an initial paired user selecting step of selecting the user with the minimum
20 multi-user channel quality indication error from transmitting users as an initial paired user,
wherein the transmitting users include all the current transmitting users which are allowed to
enter a multi-user multiple input multiple output transmission mode;
a correlation calculating step of calculating the correlation of each paired user to
each of other transmitting users, and selecting one or more users from the other transmitting
25 users as candidate paired user(s) according to the correlation;
a paired user selecting step of selecting paired user(s) from the candidate paired
user(s) according to the multi-user channel quality indication error; and
repeating the correlation calculating step and the paired user selecting step until a
predetermined number of paired users have been selected.
-30-
lg| English translation of PCT publication Sony China Ref.: CNPA10058IN00
^ Sony Ref. :SP31489IINOO
Our Ref: OP 1211-06-0773
11. An apparatus for feeding back downlink channel feedback information of a Multiple
Input Multiple Output, MIMO, communication system, comprising:
a multi-user channel quality indication error calculating unit configured to calculate a
multi-user channel quality indication error of a user, wherein the multi-user channel quality
5 indication error is used to reflect the difference in channel quality indication between the
situation of multi-user multiple input multiple output transmission and the situation of single
user multiple input multiple output transmission of the user; and
a downlink channel feedback information feeding back unit configured to add the
multi-user channel quality indication error to the downlink channel feedback information
10 including a pre-coding matrix indication and a channel quality indication, and feeding the
same back to a base station for scheduling.
12. The apparatus according to claim 11, wherein the multi-user channel quality
indication error calculating unit is further configured to calculate the multi-user channel
quality indication error based on the signal to noise ratio of the user.
15 13. The apparatus according to claim 12, wherein the multi-user channel quality
indication error calculating unit comprises:
a measuring unit configured to measure a channel state of the user to obtain a channel
information matrix and the signal to noise ratio;
a quantization error calculating unit configured to calculate a quantization error
20 according to the channel information matrix and a pre-coding matrix obtained based on the
channel information matrix;
a minimum interference level calculating unit configured to find out channel with the
minimum interference level from channels orthogonal to the channel of the user;
a multi-user mode signal to noise ratio calculating unit configured to calculate the signal
25 to noise ratio of the user in the situation of multi-user multiple input multiple output
transmission; and
an error calculating unit configured to calculate the multi-user channel quality indication
error according to the measured signal to noise ratio and the calculated signal to noise ratio of
the user in the situation of multi-user multiple input multiple output transmission.
-31 -
ii^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
^ Sony Ref: SP314891IN00
OurRef:OP1211-06-0773
14. The apparatus according to claim 13, wherein the multi-user mode signal to noise
ratio calculating unit is further configured to calculate the signal to noise ratio of the user in
the situation of multi-user multiple input multiple output transmission by using the
quantization error, the minimum interference level, and the measured signal to noise ratio
5 obtained.
15. An apparatus for user pairing of a Multiple Input Multiple Output, MIMO,
communication system, comprising:
a downlink channel feedback information receiving unit configured to receive downlink
channel feedback information from a user, wherein the downlink channel feedback
10 information includes a pre-coding matrix indication, a channel quality indication, and a
multi-user channel quality indication error, and wherein the multi-user channel quality
indication error is used to reflect the difference in channel quality indication between the
situation of multi-user multiple input multiple output transmission and the situation of single
user multiple input multiple output transmission of the user;
15 an initial paired user selecting unit configured to select the user with the minimum
multi-user channel quality indication error from transmitting users as a paired user, wherein
the transmitting users include all the current transmitting users which are allowed to enter a
multi-user multiple input multiple output transmission mode;
a correlation calculating unit configured to calculate the correlation of each paired user to
20 each of other transmitting users, and selecting one or more users as candidate paired user(s)
according to the correlation;
a paired user selecting unit configured to select paired user(s) from the candidate paired
user(s) according to the multi-user channel quality indication error; and
wherein the correlation calculating unit and the paired user selecting unit are configured
25 to repeat their operations until a predetermined number of paired users have been selected.
16. The apparatus according to claim 15, wherein the pre-coding matrix indication
corresponds to one pre-coding matrix in 2-antenna and 4-antenna base station configurations;
and the pre-coding matrix indication comprises a first pre-coding matrix indication
corresponding to transmission bandwidth information of the downlink channel and a second
30 pre-coding matrix indication corresponding to sub-band information in the transmission
-32-
ij^ English translation of PCT publication Sony China Ref.: CNPA10058INOO
T Sony Ref.:SP31489IINOO
Our Ref: OP 1211-06-0773
bandwidth of the downhnk channel in an 8-antenna base station configuration.
17. The apparatus according to claim 16, wherein the second pre-coding matrix
indication comprises at least one sub-band pre-coding matrix indication individually
corresponding to at least one sub-band, the multi-user channel quality indication error
5 comprises at least one sub-band multi-user channel quality indication error individually
corresponding to the at least one sub-band, and the channel quality indication comprises at
least one sub-band channel quality indication individually corresponding to the at least one
sub-band.
18. A user equipment comprising an apparatus for feeding back downlink channel
10 feedback information, the apparatus for feeding back downlink channel feedback information
comprising:
a multi-user channel quality indication error calculating unit configured to calculate a
multi-user channel quality indication error of a user, wherein the multi-user channel quality
indication error is used to reflect the difference in channel quality indication between the
15 situation of multi-user multiple input multiple output transmission and the situation of single
user multiple input multiple output transmission of the user;
a downlink channel feedback information feeding back unit configured to add the
multi-user channel quality indication error to the downlink channel feedback information
including a pre-coding matrix indication and a channel quality indication, and feeding the
20 same back to a base station for scheduling.
19. A base station comprising an apparatus for user pairing, the apparatus for user pairing
comprising:
a downlink channel feedback information receiving unit configured to receive downlink
channel feedback information from a user, wherein the downlink channel feedback
25 information includes a pre-coding matrix indication, a channel quality indication, and a
multi-user channel quality indication error, and wherein the multi-user channel quality
indication error is used to reflect the difference in channel quality indication between the
situation of multi-user multiple input multiple output transmission and the situation of single
user multiple input multiple output transmission of the user;
30 an initial paired user selecting unit configured to select the user with the minimum
-33-
^ English translation of PCT publication Sony China Ref.: CNPA10058IN00
^ Sony Ref.:SP31489IINOO
OurRef:OP1211-06-0773
multi-user channel quality indication error from transmitting users as a paired user, wherein
the transmitting users include all the current transmitting users which are allowed to enter a
multi-user multiple input multiple output transmission mode;
a correlation calculating unit configured to calculate the correlation of each paired user to
5 each of other transmitting users, and selecting one or more users as candidate paired user(s)
according to the correlation;
a paired user selecting unit configured to select paired user(s) from the candidate paired
user(s) according to the multi-user channel quality indication error; and
wherein the correlation calculating unit and the paired user selecting unit are configured
10 to repeat their operations until a predetermined number of paired users have been selected.
20. A communication system comprising at least one user equipment and at least one
base station, wherein the user equipment comprises an apparatus for feeding back downlink
channel feedback information, the apparatus for feeding back downlink channel feedback
information comprising:
15 a multi-user channel quality indication error calculating unit configured to calculate
a multi-user channel quality indication error of a user, wherein the multi-user channel quality
indication error is used to reflect the difference in channel quality indication between the
situation of multi-user multiple input multiple output transmission and the situation of single
user multiple input multiple output transmission of the user;
20 a downlink channel feedback information feeding back unit configured to add the
multi-user channel quality indication error to the downlink channel feedback information
including a pre-coding matrix indication and a channel quality indication, and feeding the
same back to a base station for scheduling;
the base station comprises an apparatus for user pairing, the apparatus for user pairing
25 comprising:
a downlink channel feedback information receiving unit configured to receive
downlink channel feedback information from a user, wherein the downlink channel feedback
information includes a pre-coding matrix indication, a channel quality indication, and a
multi-user channel quality indication error;
30 an initial paired user selecting unit configured to select the user with the minimum
-34-
** English translation of PCT publication Sony China Ref.: CNPA1005 8IN00
Sony Ref.: SP31489IINOO
Our Ref.: 0P1211-06-0773
multi-user channel quality indication error from transmitting users as an paired user, wherein
the transmitting users include all the current transmitting users which are allowed to enter a
multi-user multiple input multiple output transmission mode;
a correlation calculating unit configured to calculate the correlation of each paired
5 user to each of other transmitting users, and selecting one or more users as candidate paired
user(s) according to the correlation;
a paired user selecting unit configured to select paired user(s) from the candidate
paired user(s) according to the multi-user channel quality indication error; and
wherein the correlation calculating unit and the paired user selecting unit are
10 configured to repeat their operations until a predetermined number of paired users have been
selected.