U.S. patent application number 14/179976 was filed with the patent office on 2014-06-12 for scheduler and scheduling method for transmitting data in mimo based wireless lan system.
This patent application is currently assigned to PANTECH CO., LTD.. The applicant listed for this patent is PANTECH CO., LTD.. Invention is credited to Jin Hu, Ho Young Hwang, Bang Chul Jung, Dan Keun SUNG.
Application Number | 20140161109 14/179976 |
Document ID | / |
Family ID | 45556781 |
Filed Date | 2014-06-12 |
United States Patent
Application |
20140161109 |
Kind Code |
A1 |
SUNG; Dan Keun ; et
al. |
June 12, 2014 |
SCHEDULER AND SCHEDULING METHOD FOR TRANSMITTING DATA IN MIMO BASED
WIRELESS LAN SYSTEM
Abstract
A scheduler and scheduling method that may select a data
transmission time interval and a data transmitting station are
included in a multi-user Multiple Input Multiple Output (MIMO)
communication system. An access point may include a receiver to
receive channel measurement signals from stations using a plurality
of receive antennas; a channel estimation unit to generate channel
state matrices with respect to wireless channels formed from the
stations to the receive antennas using the channel measurement
signals; and a scheduler to select at least one transmitting
station from the stations by considering the channel state matrices
and a number of the receive antennas. The receiver may receive a
data stream from the selected transmitting stations. Stations
receive identifiers corresponding to transmitting stations and/or
transmitting antennas to identify stations or antennas for
transmitting data streams to the access point.
Inventors: |
SUNG; Dan Keun; (Daejeon,
KR) ; Jung; Bang Chul; (Seoul, KR) ; Hu;
Jin; (Yuseong-gu, KR) ; Hwang; Ho Young;
(Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PANTECH CO., LTD. |
Seoul |
|
KR |
|
|
Assignee: |
PANTECH CO., LTD.
Seoul
KR
|
Family ID: |
45556781 |
Appl. No.: |
14/179976 |
Filed: |
February 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12852164 |
Aug 6, 2010 |
|
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14179976 |
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Current U.S.
Class: |
370/336 ;
370/329 |
Current CPC
Class: |
G10L 13/047 20130101;
G10L 13/027 20130101; G10L 13/00 20130101; H04W 72/0413 20130101;
H04B 7/0404 20130101; G10L 13/06 20130101; G10L 25/63 20130101;
H04B 7/0697 20130101 |
Class at
Publication: |
370/336 ;
370/329 |
International
Class: |
H04W 72/04 20060101
H04W072/04; H04B 7/04 20060101 H04B007/04; H04B 7/06 20060101
H04B007/06 |
Claims
1. An access point, comprising: a plurality of receive antennas; a
receiver to receive a channel measurement signal from at least one
station, the channel measurement signal including an orthogonal
code or a pseudo-noise (PN) code having an offset; a channel
estimation unit to generate a channel state matrix with respect to
one or more wireless channels formed from the at least one station
to the plurality of receive antennas using the received channel
measurement signal; and a scheduler to select at least one station
of the at least one station to transmit one or more data streams
according to the channel state matrix and a number of the receive
antennas, wherein the receiver receives the one or more data
streams transmitted from the at least one selected station and
identifies the channel measurement signal using the orthogonal code
or the offset of the PN code.
2. The access point of claim 1, wherein: the at least one selected
station comprises a plurality of transmit antennas, and the
scheduler selects the at least one selected station according to a
number of the transmit antennas.
3. The access point of claim 1, wherein the scheduler determines a
number of the one or more data streams to be simultaneously
received by the receive antennas.
4. The access point of claim 3, wherein the number of the one or
more data streams is equal to or less than a number of the receive
antennas.
5. The access point of claim 3, wherein the number of the one or
more data streams is equal to or less than a number of the transmit
antennas.
6. The access point of claim 1, wherein the scheduler determines at
least one data reception time interval for receiving the one or
more data streams from the at least one selected station.
7. The access point of claim 1, further comprising: a
signal-to-interference and noise ratio (SINR) measurement unit to
measure an SINR with respect to the one or more wireless channels
based on the channel measurement signal.
8. The access point of claim 1, further comprising: a transmitter
to transmit an identifier of the at least one selected station to
the other of the at least one station.
9. A station, comprising: a transmitter to transmit, using at least
one transmit antenna, a channel measurement signal to an access
point having a plurality of receive antennas, the channel
measurement signal including an orthogonal code or a pseudo-noise
(PN) code having an offset; and a receiver to receive an identifier
of a station selected by the access point based on the channel
measurement signal and a number of the receive antennas, wherein,
if the received identifier corresponds to an identifier of the
selected station, the transmitter transmits one or more data
streams to the access point based on the identifier.
10. The station of claim 9, wherein the received identifier is
included in a data frame.
11. The station of claim 10, wherein the receiver receives an
indicator to indicate whether an identifier of a station other than
the selected station is included in the data frame.
12. The station of claim 9, wherein: the receiver receives channel
measurement signal allocation information from the access point,
and the transmitter generates the channel measurement signal based
on the channel measurement signal allocation information.
13. The station of claim 9, wherein: the identifier identifies a
data transmit antenna, and if the identifier corresponds to one
antenna of the at least one transmit antenna, the transmitter
transmits the one or more data streams by considering the
identifier of the data transmit antenna.
14. The station of claim 9, wherein: the receiver receives, from
the access point, data transmission time interval information for
the selected station, and the transmitter transmits the one or more
data streams based on the data transmission time interval
information.
15. A method for receiving data, comprising: receiving, using at
least one receive antenna, a channel measurement signal from at
least one station, the channel measurement signal including an
orthogonal code or a pseudo-noise (PN) code having an offset;
generating, using the received channel measurement signal, a
channel state matrix with respect to one or more wireless channels
formed from at least one of the stations to the plurality of
receive antennas; selecting at least one station of the at least
one station to transmit one or more data streams according to the
channel state matrix and a number of the receive antennas; and
receiving the one or more data streams from the at least one
selected station, wherein the channel measurement signal is
identified by the orthogonal code or the offset of the PN code.
16. The method of claim 15, wherein: the at least one selected
station comprise a plurality of transmit antennas, and the at least
one selected station is selected according to a number of the
transmit antennas.
17. The method of claim 15, further comprising: determining a
number of the one or more data streams to be simultaneously
received by the at least one receive antenna.
18. The method of claim 17, wherein the number of the one or more
data streams is equal to or less than a number of the at least one
receive antenna.
19. The method of claim 16, wherein the number of the one or more
data streams is equal to or less than a number of the transmit
antennas.
20. The method of claim 15, further comprising: determining a data
reception time interval for receiving data streams from the at
least one selected station.
21. A method for transmitting data by a station, comprising:
transmitting, using at least one transmit antenna of the station, a
channel measurement signal to an access point having a plurality of
receive antennas, the channel measurement signal including an
orthogonal code or a pseudo-noise (PN) code having an offset;
receiving an identifier of a station selected by the access point
based on the channel measurement signal and a number of the receive
antennas; determining a data transmission rate by considering a
number of the transmit antennas and a number of the receive
antennas; and if the received identifier corresponds to an
identifier of the selected station, transmitting one or more data
streams to receive antennas of the access point based on the data
transmission rate.
22. The method of claim 21, wherein the received identifier is
included in a data frame.
23. The method of claim 22, wherein the data frame comprises an
indicator indicating whether an identifier of a station other than
the selected station is included in the data frame.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/582,164, filed on Oct. 20, 2009, and claims
priority from and the benefit of Korean Patent Application No.
10-2008-0104313, filed on Oct. 23, 2008, all of which are hereby
incorporated by reference for all purposes as if fully set forth
herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a mobile communication
system, and more particularly, to a scheduler and a scheduling
method that may select a data transmission time interval and a data
transmitting station and/or data transmitting antenna in a
multi-user Multiple Input Multiple Output (MIMO) communication
system.
[0004] 2. Discussion of the Background
[0005] A wireless local area network (WLAN) is a local area network
where at least some nodes of the network are connected without
using a cable. The WLAN may avoid the cost of setting up a
cable-based network, and may also provide users with the
convenience of a network access environment, while maintaining the
simple implementation and expandability of a wired LAN.
[0006] Various types of portable devices, such as a portable
digital assistant (PDA), a portable media player (PMP), a tablet
PC, and the like, are currently being used. Also, many users desire
an ability to connect to a network with the portable devices.
Therefore, there is an increasing interest regarding the WLAN.
[0007] A representative standard associated with the WLAN may
include an Institute of Electrical and Electronics Engineers (IEEE)
802.11 Wireless-Fidelity (Wi-Fi) standard. Since the IEEE 802.11
standard was released in 1997, revisions including 11a, 11b, and
11g have been implemented. The IEEE 802.11n version is currently in
development.
[0008] The IEEE 802.11n version, which is still in the
standardization process, may adopt a system configuration based on
a MIMO communication scheme to support a higher data transmission
rate in a physical layer. The MIMO communication scheme is a scheme
where a transmission end may transmit data via multiple paths using
multiple transmit antennas, and a reception end may receive data
via multiple paths using multiple receive antennas. Through this,
the MIMO communication scheme may enhance a data transmission rate
and may reduce interference in a multi-path environment.
[0009] Accordingly, in the IEEE 802.11n WLAN, a station and an
access point each may include multiple antennas. Through this
configuration, the IEEE 802.11n WLAN may support an enhanced data
transmission rate in a physical layer in comparison to existing
versions. However, even if performance is enhanced in the physical
layer, there may be some constraints on improving the data
transmission throughput due to a limit of a protocol of a Media
Access Control (MAC) layer.
[0010] Stations accessing a particular access point may transmit
data to the particular access point in the same time slot. If the
particular access point includes only a single receive antenna, the
access point may not successfully receive all data transmitted from
the stations. Specifically, if two stations simultaneously transmit
data streams, the access point having a single receive antenna may
not successfully receive the data streams. Instead, the
simultaneously transmitted data streams may collide with each other
and an error may occur in the data streams.
[0011] In this case, each station may not receive an
acknowledgement (ACK) from the access point and thus may retransmit
the data.
[0012] If a single access point covers a small number of stations,
a collision probability may be lower so that performance
deterioration according to frame retransmission may be
insignificant. However, as a number of stations increases, the
collision probability may also increase and thus a data
transmission throughput may deteriorate.
[0013] Accordingly, there is a need for a new technology that may
reduce the risk of data collision by applying a MIMO technology to
a scheduler of a MAC layer.
SUMMARY OF THE INVENTION
[0014] Exemplary embodiments of the present invention provide a
scheduler and a scheduling method that may transmit data using a
characteristic of a Multiple Input Multiple Output (MIMO)
channel.
[0015] Exemplary embodiments of the present invention also provide
a scheduler and a scheduling method that may simultaneously receive
data at an access point having multiple receive antennas from a
plurality of stations.
[0016] Additional aspects of the invention will be set forth in the
description which follows, and in part will be apparent from the
description, or may be learned by practice of the invention.
[0017] An exemplary embodiment of the present invention discloses
an access point including a plurality of receiving antennas, a
receiver to receive channel measurement signals from a first
station and a second station; a channel estimation unit to generate
channel state matrices with respect to wireless channels formed
from the first station and the second station to the plurality of
receive antennas using the received channel measurement signals;
and a scheduler to select the first station as a first transmitting
station according to the channel state matrices and a number of the
receive antennas. The receiver receives a first data stream
transmitted from the first transmitting station.
[0018] An exemplary embodiment of the present invention discloses a
station including a transmitter to transmit a first channel
measurement signal to an access point using a first transmit
antennas; a receiver to receive an identifier of a first
transmitting station that is selected by the access point based on
a received channel measurement signal; and a control unit to
determine a data transmission rate by considering a number of
transmit antennas of the station and a number of receive antennas
of the access point. If the identifier corresponds to the station,
the transmitter transmits a data stream to the access point based
on the identifier and the data transmission rate.
[0019] An exemplary embodiment of the present invention discloses a
method for receiving data, including receiving channel measurement
signals from a first station and a second station using a plurality
of receive antennas; generating channel state matrices with respect
to wireless channels formed from the first station and the second
station to the plurality of receive antennas using the received
channel measurement signals; selecting the first station as a first
transmitting station to transmit data according to the channel
state matrices and a number of the receive antennas; and receiving
a data stream from the first transmitting station.
[0020] An exemplary embodiment of the present invention discloses a
method for transmitting data, including transmitting a first
channel measurement signal to an access point using a first
transmit antennas; receiving an identifier of a first transmitting
station that is selected by the access point based on a received
channel measurement signal; determining a data transmission rate by
considering a number of transmit antennas of the station and a
number of receive antennas of the access point; and if the
identifier corresponds to the station, transmitting a data stream
to the access point based on the identifier and the data
transmission rate.
[0021] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate exemplary
embodiments of the invention, and together with the description
serve to explain the aspects of the invention.
[0023] FIG. 1 is a diagram illustrating a concept of a Multiple
Input Multiple Output (MIMO) system according to an exemplary
embodiment of the present invention.
[0024] FIG. 2 is a block diagram illustrating a structure of an
access point according to an exemplary embodiment of the present
invention.
[0025] FIG. 3 is a diagram illustrating an example of transmitting,
by a plurality of stations, data in corresponding data transmission
time intervals according to an exemplary embodiment of the present
invention.
[0026] FIG. 4 is a block diagram illustrating a structure of a
station according to an exemplary embodiment of the present
invention.
[0027] FIG. 5 is a diagram illustrating a structure of a data frame
that includes identifiers of transmitting stations according to an
exemplary embodiment of the present invention.
[0028] FIG. 6 is a diagram for describing an operation of an access
point to transmit an identifier of a transmitting station and an
indicator according to an exemplary embodiment of the present
invention.
[0029] FIG. 7 is a flowchart illustrating a method for receiving
data according to an exemplary embodiment of the present
invention.
[0030] FIG. 8 is a flowchart illustrating a method for transmitting
data according to an exemplary embodiment of the present
invention.
[0031] FIG. 9 is a flowchart illustrating an operation for
receiving identifiers of transmitting stations shown in FIG. 8.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0032] The invention is described more fully hereinafter with
reference to the accompanying drawings, in which exemplary
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the exemplary embodiments set forth herein.
Rather, these exemplary embodiments are provided so that this
disclosure is thorough, and will fully convey the scope of the
invention to those skilled in the art. In the drawings, the size
and relative sizes of layers and regions may be exaggerated for
clarity. Like reference numerals in the drawings denote like
elements.
[0033] FIG. 1 is a diagram illustrating a concept of a Multiple
Input Multiple Output (MIMO) system according to an exemplary
embodiment of the present invention. Hereinafter, an operation of
the MIMO system will be described in more detail with reference to
FIG. 1.
[0034] Referring to FIG. 1, an access point 110 may include receive
antennas 141, 142, and 143. Although only three receive antennas
141, 142, and 143 are shown in FIG. 1 for better comprehension and
ease of description, the access point 110 could include four or
more receive antennas. The access point 110 may receive multiple
data streams using the receive antennas 141, 142, and 143 according
to a beamforming reception scheme, a spatial multiplexing reception
scheme, and the like.
[0035] The access point 110 includes receive antennas 141, 142, and
143 and may receive multiple data streams. Specifically, even if
stations 120 and 130 simultaneously transmit data streams, the
access point 110 may classify the data streams and thereby receive
the data streams. Also, an error in receiving the data streams may
be reduced by the access point 110.
[0036] A number of data streams that the access point 110 may
simultaneously receive may depend upon the number of receive
antennas included in the access point 110. Specifically, if N
receive antennas are included in the access point 110, the access
point 110 may simultaneously receive a maximum of N data streams.
Therefore, the access point 110 may simultaneously receive the data
streams from a maximum of N stations. Further, the access point 110
may select, as transmitting stations, N stations from among a
plurality of stations, and receive the data streams from the
selected transmitting stations.
[0037] Additionally, station 120 may include transmit antennas 151
and 152, and station 130 may include transmit antennas 161 and 162.
The stations 120 and 130 may transmit a data stream to the access
point 110 using each transmit antenna 151 and 152, and 161 and 162,
respectively. The data streams may be transmitted using a spatial
multiplexing transmission scheme and the like.
[0038] Even if the stations 120 and 130 transmit the data streams
to the access point 110, a total number of data streams to be
transmitted by the stations 120 and 130 may be the same as or less
than a number of receive antennas included in the access point 110
so that the access point 110 may simultaneously receive the data
streams from a maximum of N stations.
[0039] FIG. 2 is a block diagram illustrating a structure of an
access point according to an exemplary embodiment of the present
invention. Hereinafter, an operation of the access point 200 will
be described in more detail with reference to FIG. 2.
[0040] The access point 200 may include receive antennas 210, a
receiver 220, a channel estimation unit 230, a
signal-to-interference and noise ratio (SINR) measurement unit 240,
a scheduler 250, and a transmitter 260.
[0041] The receiver 220 may receive a channel measurement signal
using the receive antennas 210. Stations 270 and 280 may each
transmit a channel measurement signal to the access point 200.
Specifically, the stations 270 and 280 may each transmit the
channel measurement signal using transmit antennas 271 and 272, and
281 and 282, respectively.
[0042] Each of the stations 270 and 280 may transmit a pseudo-noise
(PN) code having a different phase offset. The receiver 220 may
identify the stations 270 and 280 using the different phase
offsets.
[0043] Each of the stations 270 and 280 may transmit an orthogonal
code. The receiver 220 may identify a channel measurement signal
transmitted from each of the stations 270 and 280 using an
orthogonality of the orthogonal codes.
[0044] Additionally, each of the stations 270 and 280 may transmit
a pseudo-noise code having a different phase offset for each
transmit antenna 271, 272, 281, and 282. Also, each of the stations
270 and 280 may transmit a different pseudo code for each transmit
antenna 271, 272, 281, and 282. The receiver 220 may identify the
channel measurement signal transmitted from each of the transmit
antennas 271, 272, 281, and 282 using the phase offset or the
orthogonality of the pseudo-noise code.
[0045] The channel estimation unit 230 may generate channel state
matrices with respect to wireless channels formed from each of the
stations 270 and 280 to the receive antennas 210 using the received
channel measurement signals. If each of the stations 270 and 280
includes only a single transmit antenna, a channel state matrix may
be in a form of a vector.
[0046] The scheduler 250 may select at least one transmitting
station from the stations 270 and 280 by considering a number of
the receive antennas 210 and the channel state matrices. The
scheduler 250 may select, as transmitting stations, a number of
stations equal to a number of receive antennas 210, or may select,
as transmit antennas, a number of stations that is less than the
number of receive antennas 210.
[0047] The receiver 220 may receive a data stream from each
selected transmitting station. The receiver 220 may receive more
than one data stream from a particular transmitting station, such
as if the particular transmitting station has more than one
transmit antenna.
[0048] Further, the scheduler 250 may determine a number of data
streams to be transmitted by each transmitting station. The
scheduler 250 may determine a number of data streams simultaneously
transmitted to be the same as or less than a number of receive
antennas 210 of the access point 200.
[0049] Further, the scheduler 250 may determine, individually with
respect to each transmitting station 270 and 280, a data reception
time interval when the receiver 220 may receive data from the
stations 270 and 280 selected as the transmitting stations.
Specifically, the scheduler 250 may individually determine the data
transmission time interval for each of the stations 270 and 280.
The scheduler 250 may determine a data transmission time interval
for each of transmitting stations so that a number of data streams
to be simultaneously transmitted by the transmitting stations is
the same as or less than a number of receive antennas 210 of the
access point.
[0050] The scheduler 250 may select a transmitting station by
further considering a number of transmit antennas included in each
of the potential transmitting stations. For example, a station with
more transmit antennas may be selected as the transmitting
station.
[0051] For example, stations 270 and 280 include transmit antennas
271 and 272, and 281 and 282, respectively. Thus, a total number of
data streams to be transmitted by the stations 270 and 280 may be
the same as or less than a number of transmit antennas 271, 272,
281, and 282.
[0052] The scheduler 250 may select a transmitting station so that
stations with multiple transmit antennas may transmit multiple data
streams. If the stations transmit the multiple data streams to the
access point 200, a data transmission throughput may be enhanced in
comparison to a case where only a single data stream is
transmitted.
[0053] The scheduler 250 may also select a particular transmit
antenna to transmit a data stream to the access point 200. An
antenna selected for transmitting a data stream to the access point
200 will be referred to as a "data transmit antenna." Additionally,
fewer than all of the transmit antennas of a single transmitting
station may be selected as the data transmit antenna. Specifically,
if a transmitting station includes four transmit antennas, only two
transmit antennas could be selected as the data transmit
antennas.
[0054] The SINR measurement unit 240 may measure an SINR with
respect to wireless channels formed from transmitting stations to
the access point 200, based on the channel measurement signals. The
scheduler 250 may select, from the plurality of stations, a
transmitting station that corresponds to a wireless channel with an
excellent SINR.
[0055] Each transmit antenna of each station may transmit a
different channel measurement signal. For example, the SINR
measurement unit 240 may measure an SINR of each wireless channel
formed from the transmit antennas 271, 272, 281, and 282 to the
receive antennas 210. The scheduler 250 may determine, individually
with respect to the stations 270 and 280 selected as transmitting
stations, one or more data transmit antennas to transmit data to
the access point 200 by considering the SINR of each wireless
channel.
[0056] Additionally, all of a first station and a second station
may be selected as transmitting stations. Also, a single transmit
antenna of the first station may be selected as a data transmit
antenna. Two transmit antennas of the second station may be
selected as data transmit antennas. In this case, the first station
may transmit data to an access point using the single transmit
antenna. The second station may transmit data to the access point
using the two transmit antennas. The access point may successfully
receive, using at least three receive antennas, a single data
stream transmitted from the first station, and two data streams
transmitted from the second station.
[0057] The transmitter 260 may transmit identifiers of transmitting
stations, selected by the scheduler 250, to the stations. Each
station may receive the identifiers and compare the received
identifiers with its own identifier to determine whether the
corresponding station is selected as a transmitting station.
[0058] The transmitter 260 may transmit identifiers of data
transmit antennas to each station. Each station may receive the
identifiers and compare the received identifiers with its own
transmit antenna identifiers to determine whether the corresponding
transmit antennas are selected as data transmit antennas to
transmit data to the access point 200.
[0059] FIG. 3 is a diagram illustrating an example of transmitting,
by a plurality of stations, data in corresponding data transmission
time intervals according to an exemplary embodiment of the present
invention. Hereinafter, transmission of data, by a plurality of
stations, in corresponding data transmission time intervals will be
described in more detail with reference to FIG. 3.
[0060] As described above, the access point may simultaneously
receive a number of data streams corresponding to a number of
receive antennas of the access point. However, if a number of the
data streams is greater than the number of receive antennas, the
access point may control a data stream transmission time so that
the number of data streams simultaneously transmitted by the
transmitting stations may be equal to or less than the number of
receive antennas.
[0061] Referring to FIG. 3, a first station 310, a second station
330, a third station 350, and a fourth station 370 are selected as
transmitting stations. In a first time interval, the first time
station 310 and the second station 330 may transmit a data stream,
respectively. In the first time interval, the third station 350 may
not transmit a data stream. Thus, the number of data streams
transmitted by the first station 310 and the second station 330 in
the first time interval may be the same as or less than the number
of receive antennas of the access point.
[0062] A state of a wireless channel may vary over time. Therefore,
a state of a wireless channel from the third station 350 to the
access point that is poor in the first time interval may improve in
a second time interval. Accordingly, in the second time interval,
the third station 350 may be selected as a transmitting station to
transmit a data stream. The first station 310 and the second
station 330 may not be selected as transmitting stations in the
second time interval and therefore may not transmit data streams in
the second time interval. Specifically, the third station 350
selected as the transmitting station may transmit the data stream
in the second time interval.
[0063] In a third time interval, the first station 310 and the
third station 350 may be selected as the transmitting stations.
Therefore, the first station 310 and the third station 350 may
transmit data streams, whereas the second station 330 may not
transmit a data stream in the third time interval.
[0064] Throughout the entire time interval, the fourth station 370
may have a relatively poor wireless channel state and may not be
selected as a transmitting station.
[0065] Referring to FIG. 3, each of the first station 310, the
second station 330, the third station 350, and the fourth station
370 may be selected as the transmitting station depending on its
wireless channel state. Further, in reference to the description of
FIG. 3 above, each of the first station 310, the second station
330, the third station 350, when selected as a transmitting
station, may transmit data streams in the selected time intervals
using one or more data transmit antennas according to the wireless
channel states and identifiers sent from the access point.
[0066] FIG. 4 is a block diagram illustrating a structure of a
station according to an exemplary embodiment of the present
invention. Hereinafter, an operation of the station will be
described in more detail with reference to FIG. 4.
[0067] Referring to FIG. 4, the station 400 may include transmit
antennas 410, a transmitter 420, a control unit 430, and a receiver
440. The transmitter 410 may transmit a channel measurement signal
to an access point 450 using at least one of the transmit antennas
410. The access point 450 may generate a channel state matrix with
respect to wireless channels formed from transmit antennas to the
access point 450. The access point 450 may select, from stations
accessing the access point 450 based on the channel state matrix, a
transmitting station to transmit a data stream to the access point
450.
[0068] The receiver 440 may receive an identifier of at least one
transmitting station that is determined based on the channel
measurement signal and selected by the access point 450. The
receiver 440 may receive a predetermined length of a data frame
that includes an identifier of at least one transmitting
station.
[0069] After receiving an identifier of a transmitting station, the
receiver 440 may receive an indicator indicating whether an
identifier of a second transmitting station is transmitted. The
receiver 440 may determine whether to receive the identifier of the
second transmitting station based on the indicator. If a number of
transmitting stations is large, the receiver 440 may consecutively
receive identifiers of transmitting stations.
[0070] The control unit 430 may determine a data transmission rate
of a data stream based on a number of the transmit antennas 410 and
a number of receive antennas 460 of the access point 450. The
control unit 430 may determine a number of data streams to be in
proportion to the number of transmit antennas 410 and the number of
receive antennas 460.
[0071] If the transmitter 420 transmits multiple data streams to
the access point 450, the control unit 430 may determine a data
transmission rate with respect to the individual data streams.
[0072] The transmitter 420 may transmit a data stream to the access
point 450 based on the identifiers of transmitting stations and the
data transmission rate. The transmitter 420 may compare identifiers
of transmitting stations received by the receiver 440 with an
identifier of the station 400. If the identifier of the station 400
is included in the identifiers of the transmitting stations, the
transmitter 420 may transmit a data stream to the access point
450.
[0073] The receiver 440 may receive channel measurement signal
allocation information from the access point 450. The transmitter
420 may generate a channel measurement signal based on the channel
measurement signal allocation information, and transmit the
generated channel measurement signal to the access point 450.
Specifically, the access point 450 may be aware of the channel
measurement signal to be transmitted by the transmitter 420. The
access point 450 may receive the channel measurement signal to
determine the station from which the channel measurement signal is
received.
[0074] The station 400 may include multiple transmit antennas 410.
The receiver 440 may receive different channel measurement signal
allocation information for each of the transmit antennas 410. For
example, the transmitter 420 may generate different channel
measurement signals for each of the transmit antennas 410, and
transmit the generated channel measurement signals to the access
point 450 using each of the transmit antennas 410.
[0075] The access point 450 may receive the channel measurement
signals and determine the transmit antennas 410 from which the
channel measurement signals are received. The access point 450 may
generate a channel state matrix with respect to wireless channels
formed from each of the transmit antennas 410 to the access point
450 using the channel measurement signals.
[0076] The access point 450 may select a data transmit antenna of a
transmitting station based on the channel state matrix. Also, the
access point 450 may select, as a data transmit antenna from the
transmit antennas 410 of stations 400, a transmit antenna with a
relatively good wireless channel state. The access point 450 may
select, as data transmit antennas, a number of transmit antennas
that is equal to or less than the number of receive antennas 460 of
the access point 450.
[0077] The receiver 420 may receive, from the access point 450, an
identifier of a data transmit antenna that is selected from among
transmit antennas of a transmitting station. The transmitter 420
may transmit at least one data stream to the access point 450 by
considering the identifier of the data transmit antenna.
[0078] The receiver 420 may receive, from the access point 450,
data transmission time interval information associated with each
transmitting station.
[0079] The access point 450 may determine a data transmission time
interval where each transmitting station transmits a data stream,
by considering the number of receive antennas 460 of the access
point 450. The access point 450 may determine the data transmission
time interval with respect to each transmitting station, so that
only a transmitting station with a number of transmit antennas that
is the same as or less than the number of receive antennas 460 is
transmitting is a given time interval.
[0080] The transmitter 420 may transmit a data stream to the access
point 450 based on data transmission time interval information.
[0081] FIG. 5 is a diagram illustrating a structure of a data frame
that includes identifiers of transmitting stations according to an
embodiment of the present invention. Hereinafter, an embodiment of
the present invention to transmit identifiers using a data frame
will be described in more detail with reference to FIG. 5.
[0082] As described above, an access point may select, from a
plurality of stations, a transmitting station to transmit a data
stream to the access point. The access point may transmit an
identifier of the selected transmitting station to each station to
identify the station selected as the transmitting station.
[0083] Thus, an access point may transmit, to each station, a data
frame that includes identifiers of the selected transmitting
stations. Referring to FIG. 5, an identifier 510 of a first
transmitting station, an identifier 520 of a second transmitting
station, and an identifier 530 of a third transmitting station may
be included in a data frame 500. Although only the single data
frame 500 is illustrated in FIG. 5, the access point may transmit
the identifiers of the transmitting stations using multiple data
frames. In FIG. 5, a region 540 that does not include an identifier
of a transmitting station may be included in the data frame 500
according to the number of transmitting stations. Also, the region
540 may include a control signal or a data stream to be transmitted
to each station.
[0084] As shown in FIG. 5, the access point may transmit an
identifier of a transmitting station to each station using an
existing data transmission frame or a control signal transmission
frame. Specifically, the access point may transmit the identifier
of the transmitting station to each station while minimizing a
change in an existing data transmission mechanism.
[0085] FIG. 6 is a diagram for describing an operation of an access
point to transmit an identifier of a transmitting station and an
indicator according to an exemplary embodiment of the present
invention. Hereinafter, transmission of identifiers of a plurality
of transmitting stations using each of the transmitting stations
and an indicator will be described in more detail with reference to
FIG. 6.
[0086] The access point may transmit an identifier 610 of a first
transmitting station and transmit a first indicator 620. The first
indicator 620 may include information regarding whether the access
point will transmit an identifier 640 of a second transmitting
station after transmitting the identifier 620 of the first
transmitting station. Specifically, each station may receive the
first indicator 620 to be aware of whether the identifier 640 of
the second transmitting station is to be transmitted.
[0087] Although the access point transmits the identifier 610 of
the first transmitting station and then transmits the first
indicator 620 without any time gap there between as shown in FIG.
6, the access point may transmit the first indicator 620 at a
predetermined time interval after the identifier 610 of the first
transmitting station is transmitted.
[0088] The access point may transmit the identifier 640 of the
second transmitting station after a predetermined idle time 630 is
elapsed after transmitting the first indicator 620. The access
point may transmit a second indicator 650 after transmitting the
identifier 640 of the second transmitting station. In FIG. 6, only
two transmitting stations, that is, the first transmitting station
and the second transmitting station are selected. Therefore, the
second indicator 650 may include information indicating that an
identifier of a third transmitting station is not transmitted after
transmitting the identifier 640 of the second transmitting station.
Alternatively, although not shown in FIG. 6, the access point may
transmit an identifier and indicator for additionally selected
transmitting stations after transmitting the second indicator
650.
[0089] If, however, a station receives the second indicator 650
including information indicating that an identifier of a third
transmitting station is not to be transmitted, the second indicator
650 may terminate an operation of receiving an identifier of a
transmitting station.
[0090] FIG. 7 is a flowchart illustrating a method for receiving
data according to an exemplary embodiment of the present invention.
Hereinafter, the method for receiving data will be described in
more detail with reference to FIG. 7.
[0091] Referring to FIG. 7, the method may be performed by an
access point in a MIMO-based WLAN. In operation S710, the access
point may receive a channel measurement signal from multiple
stations using multiple receive antennas. Here, the channel
measurement signal may include a pseudo noise code or a
predetermined length of an orthogonal code. The access point may
classify channel measurement signals based on a phase offset
difference between the channel measurement signals transmitted by
stations in operation S710. Also, in operation S710, the access
point may classify the channel measurement signals based on an
orthogonality of the channel measurement signals.
[0092] In operation S720, the access point may generate channel
state matrices with respect to wireless channels formed from each
of the station antennas to the multiple receive antennas using the
channel measurement signals. Each station may transmit a channel
measurement signal to an access point using multiple transmit
antennas. In this case, the number of rows in the channel state
matrix may be based on the number of receive antennas, and the
number of columns in the channel state matrix may be based on the
number of transmit antennas.
[0093] Each station may transmit a channel measurement signal to an
access point using only a single transmit antenna. In this case, a
channel state matrix may be in a vector form having elements
corresponding to the number of receive antennas.
[0094] In operation S730, the access point may determine at least
one transmitting station to transmit data by considering the
channel state matrices and the number of receive antennas. The
access point may determine a state of a wireless channel between a
transmitting antenna and a receiving antenna based on a channel
state matrix in operation S730. Also, the access point may measure
an SINR with respect to the wireless channel based on the state of
the wireless channel, and may determine that the wireless channel
is relatively good if the SINR has a large value.
[0095] The access point may select a number of stations as
transmitting stations that is equal to or less than the number of
receive antennas.
[0096] In operation S740, the access point may determine a number
of data streams to be simultaneously transmitted by each
transmitting station. Specifically, the access point may determine
a number of data streams that is equal to or less than the number
of receive antennas of the access point.
[0097] In operation S750, the access point may transmit one or more
identifiers corresponding to the selected transmitting stations to
each station. Each station may compare its own identifier with the
identifiers of the selected transmitting stations to determine
whether it is selected as a transmitting station.
[0098] In operation S760, the access point may receive a data
stream from the one or more selected transmitting stations.
[0099] Further, each station may include multiple transmit
antennas. In operation S730, a transmitting station may be
determined by further considering a number of transmit antennas
included in each station. For example, a station including multiple
transmit antennas may be selected as a transmitting station, and
each transmit antenna may be identified to transmit a data stream
to the access point in operation S760.
[0100] The access point may individually determine a data
transmission time interval when each transmitting station may
transmit data in operation S730. If a number of selected
transmitting stations is greater than a number of receive antennas
of the access point, each transmitting station may receive a
different data transmission time interval to transmit data.
Therefore, a total number of data streams that are simultaneously
transmitted from the data transmit antennas to the access point may
be equal to or less than the number of receive antennas of the
access point.
[0101] FIG. 8 is a flowchart illustrating a method for transmitting
data according to an exemplary embodiment of the present invention.
Hereinafter, the method for transmitting data will be described in
more detail with reference to FIG. 8.
[0102] Referring to FIG. 8, the method for transmitting data may be
performed by a station. In operation S810, the station may transmit
a channel measurement signal to an access point using at least one
transmit antenna. Here, the channel measurement signal may include
a pseudo noise code or a predetermined length of an orthogonal
code. The access point may determine that a particular channel
measurement signal is transmitted from a particular station using a
phase offset of a pseudo noise code or an orthogonality of the
orthogonal code, or may determine that the particular channel
measurement signal is transmitted from a particular transmit
antenna of the particular station.
[0103] In operation S820, the station may receive an identifier of
a transmitting station that is determined based on the channel
measurement signal. The station may receive a data frame that
includes an identifier of a transmitting station. Also, in
operation S820, the station may receive an identifier of a first
transmitting station and then receive an indicator indicating
whether an identifier of a second transmitting station is also
transmitted. A station may determine whether to perform or
terminate an identifier reception process based on the indicator.
The station may also compare its own identifier with identifiers of
transmitting stations received in operation S820. If the identifier
of the station is include in the identifiers of the transmitting
stations, the station may determine that the station is selected as
a transmitting station.
[0104] In operation S830, the station may determine a data
transmission rate based on a number of transmit antennas and a
number of receive antennas of the access point. The data
transmission rate may be determined to be in proportion to the
number of transmit antennas and the number of receive antennas.
[0105] In operation S840, the station selected as the transmitting
station according to the identifiers received in operation 5820 may
transmit a data stream to the access point according to the data
transmission rate.
[0106] FIG. 9 is a flowchart illustrating an operation for
receiving identifiers of transmitting stations shown in FIG. 8.
Hereinafter, an operation for receiving identifiers of transmitting
stations will be described in more detail with reference to FIG.
9.
[0107] FIG. 9 illustrates a process of receiving the identifier of
the transmitting station using an indicator.
[0108] In operation S910, the station may receive the identifier of
a first transmitting station.
[0109] In operation S920, the station may receive an indicator
regarding whether an identifier of a second transmitting station is
transmitted.
[0110] In operation S930, the station may determine whether to
continuously receive an identifier of another transmitting station
based on the indicator. If the indicator indicates that an
identifier transmission is terminated, the station may terminate
the identifier reception process and determine the data
transmission rate in operation S830.
[0111] However, if the indicator indicates that the identifier
transmission continues after the transmission of the indicator, the
station may return to operation S910 and receive an identifier of
another transmitting station.
[0112] The data transmission and reception method according to the
above-described exemplary embodiments of the present invention may
be recorded in computer-readable media including program
instructions to implement various operations when executed by a
computer. The media may also include, alone or in combination with
the program instructions, data files, data structures, and the
like. Examples of computer-readable media include magnetic media
such as hard disks, floppy disks, and magnetic tape; optical media
such as CD-ROM disks and DVDs; magneto-optical media such as
floptical disks; and hardware devices that are specially configured
to store and perform program instructions, such as read-only memory
(ROM), random access memory (RAM), flash memory, and the like.
Examples of program instructions include both machine code, such as
produced by a compiler, and files containing higher level code that
may be executed by the computer using an interpreter. The described
hardware devices may be configured to act as one or more software
modules in order to perform the operations of the above-described
exemplary embodiments of the present invention, or vice versa.
[0113] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
without departing from the spirit or scope of the invention. Thus,
it is intended that the present invention covers the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
* * * * *