U.S. patent application number 16/875752 was filed with the patent office on 2020-09-03 for operation method of station in wireless local area network.
The applicant listed for this patent is Newracom, Inc.. Invention is credited to Minho CHEONG, Jeehoon KIM, Hyoungjin KWON.
Application Number | 20200280351 16/875752 |
Document ID | / |
Family ID | 1000004830153 |
Filed Date | 2020-09-03 |
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United States Patent
Application |
20200280351 |
Kind Code |
A1 |
KWON; Hyoungjin ; et
al. |
September 3, 2020 |
OPERATION METHOD OF STATION IN WIRELESS LOCAL AREA NETWORK
Abstract
An operation method of a station in a wireless local area
network (WLAN) is disclosed. An operation method of a first station
comprises generating a high efficiency (HE) preamble including
scheduling information of a plurality of reception stations; and
generating a physical layer convergence procedure (PLCP) protocol
data unit (PPDU) including a legacy preamble, the HE preamble, and
a payload having data units to be transmitted to the plurality of
reception stations. Therefore, a performance of WLAN may be
enhanced.
Inventors: |
KWON; Hyoungjin; (Daejeon,
KR) ; KIM; Jeehoon; (Daejeon, KR) ; CHEONG;
Minho; (Lake Forest, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Newracom, Inc. |
Lake Forest |
CA |
US |
|
|
Family ID: |
1000004830153 |
Appl. No.: |
16/875752 |
Filed: |
May 15, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14843956 |
Sep 2, 2015 |
10693532 |
|
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16875752 |
|
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62045446 |
Sep 3, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/0041 20130101;
H04L 5/0023 20130101; H04L 5/0091 20130101; H04B 7/0413 20130101;
H04L 5/0048 20130101; H04L 5/0007 20130101; H04L 5/0087 20130101;
H04W 72/1278 20130101; H04B 7/0452 20130101 |
International
Class: |
H04B 7/0452 20060101
H04B007/0452; H04L 5/00 20060101 H04L005/00; H04W 72/12 20060101
H04W072/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 2, 2015 |
KR |
10-2015-0124136 |
Claims
1. A method performed by a station operating in a wireless network,
the method comprising: generating a high efficiency preamble,
including a first high efficiency signaling field and a second high
efficiency signaling field, wherein the second high efficiency
signaling field includes first scheduling information corresponding
to a first plurality of reception stations and second scheduling
information corresponding to a second plurality of reception
stations different from the first plurality of reception stations,
wherein (1) the first scheduling information includes a first part,
which includes first resource allocation information including a
first allocation pattern for a first set of frequency bands, and a
second part, which includes a first list of station identifiers,
including identifiers for the first plurality of reception stations
and (2) the second scheduling information includes a first part,
which includes second resource allocation information including a
second allocation pattern for a second set of frequency bands, and
a second part, which includes a second list of station identifiers,
including identifiers for the second plurality of reception
stations; generating a physical layer protocol data unit (PPDU)
including a legacy preamble, the high efficiency preamble, and a
payload, wherein the high efficiency preamble is after the legacy
preamble in the PPDU and the payload is after the high efficiency
preamble in the PPDU, wherein the payload is composed of a
plurality of resource units; and transmitting the PPDU using the
first set of frequency bands and the second set of frequency bands
to the first plurality of stations and the second plurality of
stations.
2. The method of claim 1, wherein the legacy preamble includes a
legacy short training field, a legacy long training field, and a
legacy signaling field, and wherein the first high efficiency
signaling field, the second high efficiency signaling field, and
the legacy preamble have a subcarrier spacing of 312.5 kHz.
3. The method of claim 2, wherein the PPDU includes a high
efficiency short training field and one or more high efficiency
long training fields, wherein the high efficiency short training
field, the one or more high efficiency long training fields, and
the payload have a subcarrier spacing of 78.125 kHz.
4. The method of claim 3, wherein a number of high efficiency long
training fields is set based on a number of spatial streams used
for the PPDU.
5. The method of claim 1, wherein the first high efficiency
signaling field includes a first subfield and a second subfield,
and the first high efficiency signaling field is duplicated in 20
MHz sub-channels of the PPDU.
6. The method of claim 1, wherein the high efficiency preamble
includes an indication of a combined size of the first scheduling
information and the second scheduling information included in the
second high efficiency signaling field.
7. The method of claim 1, wherein the first high efficiency
signaling field includes an indication of whether multi-user
multiple-input and multiple-output is used to transmit the
PPDU.
8. The method of claim 7, wherein the indication indicates that
full-bandwidth multi-user multiple-input and multiple-output is
used to transmit the PPDU.
9. The method of claim 1, wherein the first part of the first
scheduling information represents common information for all
stations in the first plurality of reception stations and the
second part of the first scheduling information represents
station-specific information for the first plurality of reception
stations to interpret the PPDU, and wherein the first part of the
second scheduling information represents common information for all
stations in the second plurality of reception stations and the
second part of the second scheduling information represents
station-specific information for the second plurality of reception
stations to interpret the PPDU.
10. A method performed by a station operating in a wireless
network, the method comprising: receiving a physical layer protocol
data unit (PPDU) using a first set of frequency bands and a second
set of frequency bands, the PPDU including a legacy preamble, a
high efficiency preamble, and a payload, wherein the high
efficiency preamble is after the legacy preamble in the PPDU and
the payload is after the high efficiency preamble in the PPDU, and
wherein the payload is composed of a plurality of resource units;
decoding the high efficiency preamble, including: decoding a first
high efficiency signaling field, and decoding a second high
efficiency signaling field, including: determining first scheduling
information corresponding to a first plurality of reception
stations, the first scheduling information including a first part
that includes first resource allocation information including a
first allocation pattern for the first set of frequency bands, and
a second part that includes a first list of station identifiers,
including identifiers for a first plurality of reception stations,
and determining second scheduling information corresponding to a
second plurality of reception stations different from the first
plurality of reception stations, the second scheduling information
including a first part, that includes second resource allocation
information including a second allocation pattern for the second
set of frequency bands, and a second part that includes a second
list of station identifiers, including identifiers for a second
plurality of reception stations; in response to the first list of
station identifiers including a station identifier corresponding to
the station, receiving the payload using the first resource
allocation information; and in response to the second list of
station identifiers including a station identifier corresponding to
the station, receiving the payload using the second resource
allocation information.
11. The method of claim 10, wherein the legacy preamble includes a
legacy short training field, a legacy long training field, and a
legacy signaling field, and wherein the first high efficiency
signaling field, the second high efficiency signaling field, and
the legacy preamble have a subcarrier spacing of 312.5 kHz.
12. The method of claim 11, wherein the PPDU includes a high
efficiency short training field and one or more high efficiency
long training fields, wherein the high efficiency short training
field, the one or more high efficiency long training fields, and
the payload have a subcarrier spacing of 78.125 kHz.
13. The method of claim 12, wherein a number of high efficiency
long training fields included in the PPDU is set based on a number
of spatial streams used for the PPDU.
14. The method of claim 10, wherein the first high efficiency
signaling field includes a first subfield and a second subfield,
and the first high efficiency signaling field is duplicated in 20
MHz sub-channels of the PPDU.
15. The method of claim 10, wherein the high efficiency preamble
includes an indication of a combined size of the first scheduling
information and the second scheduling information included in the
second high efficiency signaling field.
16. The method of claim 10, wherein the first high efficiency
signaling field includes an indication of whether multi-user
multiple-input and multiple-output is used to transmit the
PPDU.
17. The method of claim 16, wherein the indication indicates that
full-bandwidth multi-user multiple-input and multiple-output is
used to transmit the PPDU.
18. The method of claim 10, wherein the first part of the first
scheduling information represents common information for all
stations in the first plurality of reception stations and the
second part of the first scheduling information represents
station-specific information for the first plurality of reception
stations to interpret the PPDU, and wherein the first part of the
second scheduling information represents common information for all
stations in the second plurality of reception stations and the
second part of the second scheduling information represents
station-specific information for the second plurality of reception
stations to interpret the PPDU.
19. A wireless device for operating in a wireless network, the
wireless device comprising: a transmitter, wherein the wireless
device is configured to: generate a high efficiency preamble,
including a first high efficiency signaling field and a second high
efficiency signaling field, wherein the second high efficiency
signaling field includes first scheduling information corresponding
to a first plurality of reception stations and second scheduling
information corresponding to a second plurality of reception
stations different from the first plurality of reception stations,
wherein (1) the first scheduling information includes a first part,
which includes first resource allocation information including a
first allocation pattern for a first set of frequency bands, and a
second part, which includes a first list of station identifiers,
including identifiers for the first plurality of reception stations
and (2) the second scheduling information includes a first part,
which includes second resource allocation information including a
second allocation pattern for a second set of frequency bands, and
a second part, which includes a second list of station identifiers,
including identifiers for the second plurality of reception
stations; generate a physical layer protocol data unit (PPDU)
including a legacy preamble, the high efficiency preamble, and a
payload, wherein the high efficiency preamble is after the legacy
preamble in the PPDU and the payload is after the high efficiency
preamble in the PPDU, wherein the payload is composed of a
plurality of resource units; and transmit, using the transmitter,
the PPDU using the first set of frequency bands and the second set
of frequency bands to the first plurality of stations and the
second plurality of stations.
20. The wireless device of claim 19, wherein the first part of the
first scheduling information represents common information for all
stations in the first plurality of reception stations and the
second part of the first scheduling information represents
station-specific information for the first plurality of reception
stations to interpret the PPDU, and wherein the first part of the
second scheduling information represents common information for all
stations in the second plurality of reception stations and the
second part of the second scheduling information represents
station-specific information for the second plurality of reception
stations to interpret the PPDU.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
U.S. patent application Ser. No. 14/843,956, filed Sep. 2, 2015,
which claims priority to U.S. Patent Application No. 62/045,446,
filed on Sep. 3, 2014, and Korean Patent Application No.
10-2015-0124136 filed on Sep. 2, 2015, the entire contents of which
are hereby incorporated by reference.
BACKGROUND
1. Technical Field
[0002] The present disclosure relates to a wireless local area
network (WLAN) technology, and more particularly to a technology
for multi-user transmission and reception in the WLAN.
2. Related Art
[0003] With the development of information communication
technologies, a variety of wireless communication technologies have
been developed. Among these technologies, wireless local area
network (WLAN) is a technology that Internet access is possible in
a wireless way in homes, business or specific service providing
areas, using portable terminal such as personal digital assistant
(PDA), a laptop computer, a portable multimedia player (PMP), or
the like, based on wireless frequency technologies.
[0004] WLAN technologies are created and standardized by the IEEE
802.11 Working Group under IEEE 802 Standard Committee. As such
WLAN technology becomes more prevalent and its applications become
more diverse, there is increasing demand for new WLAN technology
that can support a higher throughput than existing WLAN
technologies. Very high throughput (VHT) WLAN technology is
proposed to support a data rate of 1 Gbps and higher. A WLAN
technology according to IEEE 802.11ac standard is a technology
providing VHT in sub 6 GHz band, and A WLAN technology according to
IEEE 802. 11 ad standard is a technology providing VHT in 60 GHz
band.
[0005] In addition to the above-described standards, various
standards on WLAN technologies have been developed, and are being
developed. As representative recent technologies, a WLAN technology
according to IEEE 802.11af standard is a technology which has been
developed for WLAN operation in TV white space bands, and a WLAN
technology according to IEEE 802.11ah standard is a technology
which has been developed for supporting a great number of stations
operating with low power in sub 1 GHz band, and a WLAN technology
according to IEEE 802.11ai standard is a technology which has been
developed for supporting fast initial link setup (FILS) in WLAN
systems. Also, IEEE 802.11ax standard is being developed for
enhancing frequency efficiency of dense environments in which
numerous access points and stations exist.
[0006] In the system based on such the WLAN technologies, in a case
that data units for multiple users are transmitted through a
physical layer convergence procedure (PLCP) protocol data unit
(PPDU), methods for informing which users receive the data units
and which resources are used for transmitting the data units are
needed.
SUMMARY
[0007] Accordingly, exemplary embodiments of the present disclosure
are provided to substantially obviate one or more problems due to
limitations and disadvantages of the related art. Exemplary
embodiments of the present disclosure provide scheduling methods
and apparatuses for multi-user transmission.
[0008] In order to achieve the objectives of the present
disclosure, an operation method performed in a first station
according to an exemplary embodiment, the method may comprise:
generating a high efficiency (HE) preamble including scheduling
information of a plurality of reception stations; and generating a
physical layer convergence procedure (PLCP) protocol data unit
(PPDU) including a legacy preamble, the HE preamble, and a payload
having data units to be transmitted to the plurality of reception
stations.
[0009] Here, the HE preamble further includes information
indicating a transmission manner of the PPDU.
[0010] Here, the PPDU is transmitted based on at least one of a
multi user-multiple input multiple output (MU-MIMO) and an
orthogonal frequency division multiple access (OFDMA).
[0011] Here, the scheduling information is included in a HE signal
(HE-SIG) field of the HE preamble.
[0012] Here, the scheduling information includes resource
allocation information indicating a resource allocated to the
plurality of reception stations and identification information for
each of the plurality of reception stations.
[0013] Here, the scheduling information further includes
identification information of a sub-group to which the plurality of
reception stations belong.
[0014] Here, the resource allocation information is an allocation
pattern of spatial streams or an allocation pattern of frequency
bands.
[0015] Here, the HE preamble further includes scheduling
information of a plurality of groups to which the plurality of
reception stations respectively belong.
[0016] Here, the scheduling information includes resource
allocation information indicating a resource allocated to the
plurality of groups and identification information for each of the
plurality of groups.
[0017] Here, when the payload included in the PPDU is divided into
a plurality of time domains and at least one time domain among the
plurality of time domains has a different allocation pattern of
frequency bands, the HE preamble includes scheduling information
for each of the plurality of time domains.
[0018] Here, when the payload included in the PPDU is divided into
a plurality of time domains, the HE preamble further includes
information indicating that the payload is divided into the
plurality of time domains.
[0019] Here, when the payload included in the PPDU is divided into
a plurality of time domains, the HE preamble further includes
information indicating lengths of data units included in each of
the plurality of time domains.
[0020] Here, when the PPDU includes data units belonging to
different access categories, the HE preamble further includes
information indicating that the PPDU includes data units belonging
to different access categories.
[0021] Here, when the PPDU includes data units belonging to
different access categories, the HE preamble further includes
traffic identifiers (TIDs) for access categories to which the data
units respectively belong.
[0022] Here, the PPDU includes data units belonging to different
access categories and information indicating an end of data units
belonging to a first access category, and the information
indicating the end of data units is located between data units
belonging to the different access categories.
[0023] In order to achieve the objectives of the present
disclosure, an operation method performed in a first station
according to another exemplary embodiment, the method may comprise:
obtaining a legacy preamble of a physical layer convergence
procedure (PLCP) protocol data unit (PPDU); obtaining a high
efficiency (HE) preamble of the PPDU; and obtaining at least one
data unit included in a payload of the PPDU through a resource
indicated by scheduling information for a plurality of reception
stations included in the HE preamble.
[0024] Here, the HE preamble further includes information
indicating a transmission manner of the PPDU.
[0025] Here, the scheduling information includes resource
allocation information indicating a resource allocated to the
plurality of reception stations and identification information for
each of the plurality of reception stations.
[0026] Here, the scheduling information further includes
identification information of a sub-group to which the plurality of
reception stations belong.
[0027] Here, the resource allocation information is an allocation
pattern of spatial streams or an allocation pattern of frequency
bands.
[0028] Here, when the payload included in the PPDU is divided into
a plurality of time domains and at least one time domain among the
plurality of time domains has a different allocation pattern of
frequency bands, the HE preamble includes scheduling information
for each of the plurality of time domains.
[0029] Here, when the payload included in the PPDU is divided into
a plurality of time domains, the HE preamble further includes
information indicating lengths of data units included in each of
the plurality of time domains.
[0030] According to exemplary embodiments of the present
disclosure, scheduling methods for multi-user transmission (e.g.,
orthogonal frequency division multiple access (OFDMA), multi
user-multiple input multiple output (MU-MIMO), etc.) may be
provided. According to the scheduling methods for multi-user
transmission, each of spatial streams may be used for transmitting
data units of different users, and each of frequency bands included
in a single spatial stream may be used for transmitting data units
of different users. Also, respective data units of multiple users
may be multiplexed and transmitted in a time domain of a single
frequency band.
[0031] Also, according to the scheduling methods for multi-user
transmission, space, frequency, and time resources can be
efficiently utilized. Also, the scheduling methods can be performed
with minimum scheduling information exchanges. Thus, the
performance of WLAN can be enhanced, and Quality of Service (QoS)
and Quality of Experience (QoE) for users may also be enhanced.
[0032] Also, an aggregate-MPDU (A-MPDU) including a plurality of
medium access control (MAC) protocol data units (MPDUs) belonging
to different access categories (e.g., AC_VO, AC_VI, AC_BE, and
AC_BK) may be generated, and an A-MPDU including MPDUs having
different frame formats (e.g., data frame, management frame, and
control frame) may also be generated. Therefore, since an A-MPDU
can be formed in various ways, the performance of WLAN systems may
be enhanced.
BRIEF DESCRIPTION OF DRAWINGS
[0033] Exemplary embodiments of the present disclosure will become
more apparent by describing in detail exemplary embodiments of the
present disclosure with reference to the accompanying drawings, in
which:
[0034] FIG. 1 is a block diagram illustrating a structure of a WLAN
device according to an embodiment;
[0035] FIG. 2 is a schematic block diagram illustrating a
transmitting signal processing unit 100 according to an embodiment
suitable for use in a WLAN;
[0036] FIG. 3 is a schematic block diagram of a receiving signal
processing unit according to an embodiment suitable for use in the
WLAN;
[0037] FIG. 4 illustrates interframe space (IFS) relationships;
[0038] FIG. 5 is a timing diagram illustrating a frame transmission
procedure based on a CSMA (carrier sense multiple access)/CA
(collision avoidance) manner for avoiding collision between frames
in a channel;
[0039] FIG. 6 is a flow chart illustrating a method of multi-user
transmission according to an exemplary embodiment;
[0040] FIG. 7 is a block diagram illustrating an exemplary
embodiment of PPDU;
[0041] FIG. 8 is a block diagram illustrating scheduling
information included in HE preamble;
[0042] FIG. 9 is a conceptual diagram illustrating an exemplary
embodiment of an allocation pattern of spatial streams;
[0043] FIG. 10 is a conceptual diagram illustrating an exemplary
embodiment of an allocation pattern of frequency bands;
[0044] FIG. 11 is a block diagram illustrating an exemplary
embodiment of a payload included in a PPDU; and
[0045] FIG. 12 is a block diagram illustrating another exemplary
embodiment of a payload included in a PPDU.
DETAILED DESCRIPTION
[0046] In the following detailed description, only certain
embodiments of the present disclosure have been shown and
described, simply by way of illustration. As those skilled in the
art would realize, the described embodiments may be modified in
various different ways, all without departing from the spirit or
scope of the present disclosure. Accordingly, the drawings and
description are to be regarded as illustrative in nature and not
restrictive. Like reference numerals designate like elements
throughout the specification.
[0047] In a wireless local area network (WLAN), a basic service set
(BSS) includes a plurality of WLAN devices. The WLAN device may
include a medium access control (MAC) layer and a physical (PHY)
layer according to IEEE (Institute of Electrical and Electronics
Engineers) 802.11 standard. In the plurality of WLAN devices, at
least one WLAN device may be an access point and the other WLAN
devices may be non-AP stations (non-AP STAs). Alternatively, all of
the plurality of WLAN devices may be non-AP STAs in Ad-hoc
networking. In general, the AP STA and the non-AP STAs may be
collectively called the STA. However, for ease of description
herein, only the non-AP STAs are referred to as the STAs.
[0048] FIG. 1 is a block diagram illustrating a structure of a WLAN
device according to an embodiment.
[0049] Referring to FIG. 1, the WLAN device 1 may include a
baseband processor 10, a radio frequency (RF) transceiver 20, an
antenna unit 30, a memory 40, an input interface unit 50, an output
interface unit 60, and a bus 70. The baseband processor 10 may
perform baseband signal processing, and may include a MAC processor
11 and a PHY processor 15.
[0050] In one embodiment, the MAC processor 11 may include a MAC
software processing unit 12 and a MAC hardware processing unit 13.
The memory 40 may store software (hereinafter referred to as "MAC
software") including at least some functions of the MAC layer. The
MAC software processing unit 12 executes the MAC software to
implement the some functions of the MAC layer, and the MAC hardware
processing unit 13 may implement remaining functions of the MAC
layer as hardware (hereinafter referred to "MAC hardware").
However, embodiments of the MAC processor 11 are not limited to
this. The PHY processor 15 may include a transmitting (Tx) signal
processing unit 100 and a receiving (Rx) signal processing unit
200.
[0051] The baseband processor 10, the memory 40, the input
interface unit 50, and the output interface unit 60 may communicate
with each other via the bus 70. The RF transceiver 20 may include
an RF transmitter 21 and an RF receiver 22. The memory may further
store an operating system and applications. The input interface
unit 50 receives information from a user, and the output interface
unit 60 outputs information to the user.
[0052] The antenna unit 30 includes one or more antennas. When
multiple-input multiple-output (MIMO) or multi-user MIMO (MU-MIMO)
is used, the antenna unit 30 may include a plurality of
antennas.
[0053] FIG. 2 is a schematic block diagram illustrating a
transmitting signal processing unit 100 according to an embodiment
suitable for use in a WLAN.
[0054] Referring to FIG. 2, a transmitting signal processing unit
100 may include an encoder 110, an interleaver 120, a mapper 130,
an inverse Fourier transformer (IFT) 140, and a guard interval (GI)
inserter 150.
[0055] The encoder 110 encodes input data. For example, the encoder
100 may be a forward error correction (FEC) encoder. The FEC
encoder may include a binary convolutional code (BCC) encoder
followed by a puncturing device, or may include a low-density
parity-check (LDPC) encoder.
[0056] The transmitting signal processing unit 100 may further
include a scrambler for scrambling the input data before the
encoding to reduce the probability of long sequences of 0s or 1s.
If BCC encoding is used in the encoder, the transmitting signal
processing unit 100 may further include an encoder parser for
demultiplexing the scrambled bits among a plurality of BCC
encoders. If LDPC encoding is used in the encoder, the transmitting
signal processing unit 100 may not use the encoder parser.
[0057] The interleaver 120 interleaves the bits of each stream
output from the encoder to change an order of bits. Interleaving
may be applied only when BCC encoding is used. The mapper 130 maps
the sequence of bits output from the interleaver to constellation
points. If the LDPC encoding is used in the encoder, the mapper 130
may further perform LDPC tone mapping besides the constellation
mapping.
[0058] When the MIMO or the MU-MIMO is used, the transmitting
signal processing unit 100 may use a plurality of interleavers 120
and a plurality of mappers 130 corresponding to a number of spatial
streams Nss. In this case, the transmitting signal processing unit
100 may further include a stream parser for dividing outputs of the
BCC encoders or the LDPC encoder into blocks that are sent to
different interleavers 120 or mappers 130. The transmitting signal
processing unit 100 may further include a space-time block code
(STBC) encoder for spreading the constellation points from the NSS
spatial streams into NSTS space-time streams and a spatial mapper
for mapping the space-time streams to transmit chains. The spatial
mapper may use direct mapping, spatial expansion, or
beamforming.
[0059] The IFT 140 converts a block of the constellation points
output from the mapper 130 or the spatial mapper to a time domain
block (i.e., a symbol) by using an inverse discrete Fourier
transform (IDFT) or an inverse fast Fourier transform (IFFT). If
the STBC encoder and the spatial mapper are used, the inverse
Fourier transformer 140 may be provided for each transmit
chain.
[0060] When the MIMO or the MU-MIMO is used, the transmitting
signal processing unit 100 may insert cyclic shift diversities
(CSDs) to prevent unintentional beamforming. The CSD insertion may
occur before or after the inverse Fourier transform. The CSD may be
specified per transmit chain or may be specified per space-time
stream. Alternatively, the CSD may be applied as a part of the
spatial mapper. When the MU-MIMO is used, some blocks before the
spatial mapper may be provided for each user.
[0061] The GI inserter 150 prepends a guard interval (GI) to the
symbol. The transmitting signal processing unit 100 may optionally
perform windowing to smooth edges of each symbol after inserting
the GI. The RF transmitter 21 converts the symbols into an RF
signal and transmits the RF signal via the antenna unit 30. When
the MIMO or the MU-MIMO is used, the GI inserter 150 and the RF
transmitter 21 may be provided for each transmit chain.
[0062] FIG. 3 is a schematic block diagram of a receiving signal
processing unit according to an embodiment suitable for use in the
WLAN.
[0063] Referring to FIG. 3, a receiving signal processing unit 200
may include a GI remover 220, a Fourier transformer (FT) 230, a
demapper 240, a deinterleaver 250, and a decoder 260. An RF
receiver 22 receives an RF signal via the antenna unit 30 and
converts the RF signal into a symbol. The GI remover 220 removes
the GI from the symbol. When the MIMO or the MU-MIMO is used, the
RF receiver 22 and the GI remover 220 may be provided for each
receive chain.
[0064] The FT 230 converts the symbol (i.e., the time domain block)
into a block of the constellation points by using a discrete
Fourier transform (DFT) or a fast Fourier transform (FFT). The
Fourier transformer 230 may be provided for each receive chain.
When the MIMO or the MU-MIMO is used, the receiving signal
processing unit 200 may include a spatial demapper for converting
the Fourier transformed receiver chains to constellation points of
the space-time streams, and an STBC decoder for despreading the
constellation points from the space-time streams into the spatial
streams.
[0065] The demapper 240 demaps the constellation points output from
the Fourier transformer 230 or the STBC decoder to the bit streams.
If the LDPC encoding is used, the demapper 240 may further perform
LDPC tone demapping before the constellation demapping. The
deinterleaver 250 deinterleaves the bits of each stream output from
the demapper 240. Deinterleaving may be applied only when BCC
encoding is used.
[0066] When the MIMO or the MU-MIMO is used, the receiving signal
processing unit 200 may use a plurality of demappers 240 and a
plurality of deinterleavers 250 corresponding to the number of
spatial streams. In this case, the receiving signal processing unit
200 may further include a stream deparser for combining the streams
output from the deinterleavers 250.
[0067] The decoder 260 decodes the streams output from the
deinterleaver 250 or the stream deparser. For example, the decoder
100 may be an FEC decoder. The FEC decoder may include a BCC
decoder or an LDPC decoder. The receiving signal processing unit
200 may further include a descrambler for descrambling the decoded
data. If BCC decoding is used in the decoder, the receiving signal
processing unit 200 may further include an encoder deparser for
multiplexing the data decoded by a plurality of BCC decoders. If
LDPC decoding is used in the decoder 260, the receiving signal
processing unit 100 may not use the encoder deparser.
[0068] FIG. 4 illustrates interframe space (IFS) relationships.
[0069] Referring to FIG. 4, a data frame, a control frame, or a
management frame may be exchanged between WLAN devices. The data
frame is used for transmission of data forwarded to a higher layer.
The WLAN device transmits the data frame after performing backoff
if a distributed coordination function IFS (DIFS) has elapsed from
a time when the medium has been idle.
[0070] The management frame is used for exchanging management
information which is not forwarded to the higher layer. Subtype
frames of the management frame include a beacon frame, an
association request/response frame, a probe request/response frame,
and an authentication request/response frame. The control frame is
used for controlling access to the medium. Subtype frames of the
control frame include a request to send (RTS) frame, a clear to
send (CTS) frame, and an acknowledgement (ACK) frame. When the
control frame is not a response frame of a previous frame, the WLAN
device transmits the control frame after performing backoff when
the DIFS has elapsed. When the control frame is the response frame
of the previous frame, the WLAN device transmits the control frame
without performing backoff when a short IFS (SIFS) has elapsed. The
type and subtype of frame may be identified by a type field and a
subtype field in a frame control field.
[0071] On the other hand, a Quality of Service (QoS) STA may
transmit the frame after performing backoff when an arbitration IFS
(AIFS) for access category (AC), i.e., AIFS[AC] has elapsed. In
this case, the data frame, the management frame, or the control
frame which is not the response frame may use the AIFS [AC].
[0072] FIG. 5 is a timing drawing illustrating a frame transmission
procedure based on a CSMA (carrier sense multiple access)/CA
(collision avoidance) manner for avoiding collision between frames
in a channel.
[0073] Referring to FIG. 5, STA1 is a transmit WLAN device for
transmitting data, STA2 is a receive WLAN device for receiving the
data, and STA3 is a third WLAN device which may be located at an
area where a frame transmitted from the STA1 and/or a frame
transmitted from the STA2 can be received by the third WLAN device
STA3.
[0074] The STA1 may determine whether the channel is busy by
carrier sensing. The STA1 may determine the channel occupation
based on an energy level on the channel or correlation of signals
in the channel, or may determine the channel occupation by using a
network allocation vector (NAV) timer.
[0075] When it is determined that the channel is not in use by
other devices during DIFS (that is, the channel is idle), the STA1
may transmit an RTS frame to the STA2 after performing backoff.
Upon receiving the RTS frame, the STA2 may transmit a CTS frame as
a response of the CTS frame after a SIFS.
[0076] When the STA3 receives the RTS frame, it may set the NAV
timer for a transmission duration of subsequently transmitted
frames (for example, a duration of SIFS+CTS frame
duration+SIFS+data frame duration+SIFS+ACK frame duration) by using
duration information included in the RTS frame. When the STA3
receives the CTS frame, it may set the NAV timer for a transmission
duration of subsequently transmitted frames (for example, a
duration of SIFS+data frame duration+SIFS+ACK frame duration) by
using duration information included in the CTS frame. Upon
receiving a new frame before the NAV timer expires, the STA3 may
update the NAV timer by using duration information included in the
new frame. The STA3 does not attempt to access the channel until
the NAV timer expires.
[0077] When the STA1 receives the CTS frame from the STA2, it may
transmit a data frame to the STA2 after a SIFS elapses from a time
when the CTS frame has been completely received. Upon successfully
receiving the data frame, the STA2 may transmit an ACK frame as a
response of the data frame after a SIFS elapses.
[0078] When the NAV timer expires, the STA3 may determine whether
the channel is busy by the carrier sensing. Upon determining that
the channel is not in use by the other devices during DIFS after
the NAV timer has expired, the STA3 may attempt the channel access
after a contention window according to random backoff
operation.
[0079] Meanwhile, multi-user transmission, such as orthogonal
frequency division multiple access (OFDMA), MU-MIMO, and so on, may
be performed in the WLAN. In the below description, methods for
multi-user transmission in the WLAN will be explained.
[0080] FIG. 6 is a flow chart illustrating a method of multi-user
transmission according to an exemplary embodiment.
[0081] Referring to FIG. 6, stations STA1 to STA9 may establish a
BSS. Here, the STA1 may be an AP, and each of the STA2 to STA9 may
be a non-AP STA. The STA1 may determine stations which will
participate in multi-user transmission (S600). For example, the
STA1 may transmit a first frame including an indicator requesting
identification information (e.g., MAC address, association
identifier (AID), partial AID (PAID), etc.) of the stations
participating in multi-user transmission in a broadcast manner or a
unicast manner. The STA1 may receive second frames including
identification information of the STA2 to STA9 as responses
corresponding to the first frame. In this case, the STA1 may
determine the STA2 to STA9 which transmitted the second frames as
stations participating in multi-user transmission. Each of the
first frame and the second frames may be a management frame, a
control frame, or a data frame.
[0082] The STA1 may set the stations participating in multi-user
transmission to at least one sub-group. The STA1 may set a
sub-group ID corresponding to each sub-group for identifying
respective sub-groups, and set respective IDs for stations included
in the respective sub-groups. For example, the STA1 may set a
sub-group 1 including the STA2 to STA5, and set its sub-group ID to
`00.` Also, for the sub-group 1, the STA1 may set an ID of the STA2
to `00,` an ID of the STA3 to `01,` an ID of the STA4 to `10,` and
an ID of the STA5 to `11` Alternatively, each of the IDs of the
STA2 to STA5 may be set to AID or PAID.
[0083] Also, the STA1 may set a sub-group 2 including the STA6 to
STA9, and set its sub-group ID to `01`. Also, for the sub-group 2,
the STA1 may set an ID of the STA6 to `00,` an ID of the STAT to
`01,` an ID of the STA8 to `10,` and an ID of the STA9 to `11.`
Alternatively, each of the IDs of the STA6 to STA9 may be set to
AID or PAID. The STA1 may set at least one group including a
plurality of sub-groups, and set a group ID for identifying
respective groups. For example, the STA1 may set a group 1
including the sub-group 1 and the sub-group 2, and set an ID of the
group 1 to `00.` Here, each of `00,` `01,` `10,` and `11` may be a
binary number. According to the above-described manner, the
relation among the group ID, the sub-group ID, and the station ID
may be set as represented in the below table 1.
TABLE-US-00001 TABLE 1 Group ID Sub-group ID Station ID Group 1 00
Sub-group 1 00 STA2 00 STA3 01 STA4 10 STA5 11 Sub-group 2 01 STA6
00 STA7 01 STA8 10 STA9 11
[0084] According to the table 1, in a case that `group
ID--sub-group ID--station ID` is used for multi-user transmission,
the STA2 may be identified as `00 00 00,` and the STA7 may be
identified as `00 01 01.` Alternatively, in a case that `sub-group
ID--station ID` is used for multi-user transmission, the STA2 may
be identified as `00 00,` and the STA7 may be identified as `01
01.` The set manner of `group ID--sub-group ID--station ID` is not
restricted to the above-described manner. For example, the set
manner of `group ID--sub-group ID--station ID` may vary according
to various exemplary embodiments.
[0085] Alternatively, instead of the above-described manner (e.g.,
group--sub-group), the STA1 may set stations participating in
multi-user transmission to at least one group. As represented in
the below table 2, the STA2 to STA9 may be identified by using
`group ID--station ID.`
TABLE-US-00002 TABLE 2 Group ID Station ID Group 1 00 STA2 00 STA3
01 STA4 10 STA5 11 Group 2 01 STA6 00 STA7 01 STA8 10 STA9 11
[0086] The STA1 may generate a Physical Layer Convergence Procedure
(PLCP) protocol data unit (PPDU) to be transmitted according to
multi-user transmission manner (S610). Here, the PPDU may be
constructed as described below.
[0087] FIG. 7 is a block diagram illustrating an exemplary
embodiment of PPDU.
[0088] Referring to FIG. 7, when multi-user transmission is
performed based on MU-MIMO, the STA1 may generate the PPDU
transmitted through spatial streams SS-1, SS-2, . . . , SS-n. Here,
n is a natural number larger than 3. The PPDU may be transmitted
through frequency bandwidth 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320
MHz, etc. In the PPDU, fields subsequent to a HE-signal A
(HE-SIG-A) field may be transmitted through frequency bandwidth
smaller than 20 MHz (e.g., 2.5 MHz, 5 MHz, 10 MHz, etc.) Each of
the frequency bands FB-1, FB-2, FB-3, and FB-4 may have a frequency
bandwidth 20 MHz. Also, in the frequency bands, subcarrier spacing
may be 312.5 kHz, 156.25 kHz, or 78.125 kHz. In the present
disclosure, the PPDU transmitted through frequency bandwidth 80 HMz
will be described.
[0089] The PPDU may include a legacy preamble, a High Efficiency
(HE) preamble, and a payload. The legacy preamble may include a
Legacy-Short Training Field (L-STF), a Legacy-Long Training Field
(L-LTF), and a Legacy-Signal (L-SIG) field. The HE preamble may
include the HE-SIG-A field, a HE-STF field, at least one HE-LTF,
and HE-SIG-B field. The HE-SIG-A field may include a HE-SIG-A1
field, a HE-SIG-A2 field, etc. The HE-SIG-A field may be duplicated
in unit of 20 MHz. The number of HE-LTFs included in the HE
preamble may be determined according to the number of spatial
streams through which the PPDU is transmitted. For example, when
the PPDU is transmitted through a single spatial stream in
frequency bandwidth 20 MHz, a single HE-LTF may be included in the
HE preamble. Meanwhile, when the number of spatial streams through
which the PPDU is transmitted is 4, 4 HE-LTFs may be included in
the HE preamble. The HE-SIG-B field may include a HE-SIG-B1 field,
a HE-SIG-B2 field, etc. The structure of the HE preamble is not
restricted to the above-described example. That is, the HE preamble
may have various structures.
[0090] The HE-SIG fields (e.g., the HE-SIG-A field, the HE-SIG-B
field, etc.) may include a first identifier. The first identifier
may indicate which transmission manner is used for transmitting the
PPDU including the HE-SIG fields (or, the payload included in the
PPDU). For example, the first identifier may be set as represented
in the below table 3.
TABLE-US-00003 TABLE 3 First Identifier Transmission Manner 00
Non-MU-MIMO (SU-MIMO), non-OFDMA (OFDM) 01 MU-MIMO 10 OFDMA 11
MU-MIMO, OFDMA
[0091] According to the table 3, when the first identifier is set
to `00,` it may indicate that the PPDU is transmitted in based on
OFDM (e.g., a transmission manner except multi-user transmission
manners such as MU-MIMO and OFDMA). When the first identifier is
set to `01,` it may indicate that the PPDU is transmitted based on
MU-MIMO. When the first identifier is set to `10,` it may indicate
that the PPDU is transmitted based on OFDMA. Also, when the first
identifier is set to `11,` it may indicate that the PPDU is
transmitted based on MU-MIMO/OFDMA. Here, each of `00,` `01,` `10,`
and `11` may be a binary number. The set manner of the first
identifier is not restricted to the above-described example. That
is, the first identifier may be set in various manners. For
example, when the first identifier is set to binary number `0,` it
may indicate that the PPDU is transmitted based on non-OFDMA. When
the first identifier is set to binary number `1,` it may indicate
that the PPDU is transmitted based on OFDMA. Alternatively, in a
case that there is scheduling information for multi-user
transmission which will be described below in the HE preamble, the
scheduling information may indicate that the PPDU is transmitted
according to a transmission manner corresponding to the scheduling
information. On the contrary, when the scheduling information do
not exist in the HE preamble, it may indicate that the PPDU is
transmitted based on OFDM. Alternatively, the first identifier may
indicate that the PPDU is transmitted based on single user-single
input single output (SU-SISO) (or, SU-MIMO). According to the
transmission manner indicated by the first identifier, the length
of the HE-SIG-B field included in the HE preamble may vary. For
example, in a case that the transmission manner of the PPDU
indicated by the first identifier is SU-SISO or SU-MIMO, since
scheduling information for reception stations is not necessary, the
length of HE-SIG-B field of the HE preamble may be 0.
[0092] Meanwhile, the HE preamble may include scheduling
information for multi-user transmission, and the scheduling
information included in the HE preamble may vary according to the
transmission manner of the PPDU. Alternatively, instead of
including the scheduling information in the HE preamble, an
additional frame including the scheduling information may be
generated. In this case, the STA1 may transmit the frame including
the scheduling information, and then transmit the PPDU based on the
scheduling information. In the below description, the HE preamble
used for PPDU transmissions based on MU-MIMO, OFDMA, and
MU-MIMO/OFDMA will be described.
[0093] FIG. 8 is a block diagram illustrating scheduling
information included in HE preamble.
[0094] Referring to FIG. 8, the HE-SIG field 810 (e.g., the
HE-SIG-A field, the HE-SIG-B field, etc.) of the HE preamble used
for transmitting the PPDU based on MU-MIMO may include a sub-group
ID field 811, a resource allocation information field 812, and a
station ID list field 813. The sub-group ID field 811 may indicate
a sub-group ID according to the above-described table 1. The
resource allocation information field 812 may indicate an
allocation pattern of at least one spatial stream. The size of the
resource allocation information field 812 may vary according to the
resource allocation pattern or the number of reception stations. In
a case that the size of the resource allocation information field
812 varies, the HE preamble may include information indicating that
the size of the resource allocation information field 812 varies
and further include information indicating the size of the
scheduling information (or, the size of the resource allocation
information field 812). In this case, each of the information
indicating the size of the resource allocation information field
812 varies and the information indicating the size of the
scheduling information or the size of the resource allocation
information field 812 may be positioned prior to the field
including the scheduling information (or, the resource allocation
information field 812) in the HE preamble.
[0095] Meanwhile, the scheduling information may be included in the
HE-SIG-A field or the HE-SIG-B field among the HE-SIG fields of the
HE preamble. Here, the HE-SIG-B field may include a common filed or
a user-specific field. Among the scheduling information, common
information for reception stations may be included in the common
field of the HE-SIG-B field, and specific information for a
specific reception station may be included in the user-specific
field of the HE-SIG-B field. Alternatively, the scheduling
information may be included in the HE-SIG-A field or the HE-SIG-B
field of the HE preamble. For example, among the scheduling
information, a part of common information for reception stations
may be included in the HE-SIG-A field, and the rest of them may be
included in the common field of the HE-SIG-B field. Also, the
information used for a specific reception station may be included
in the user-specific field of the HE-SIG-B filed.
[0096] FIG. 9 is a conceptual diagram illustrating an exemplary
embodiment of an allocation pattern of spatial streams.
[0097] Referring to FIG. 9, in a case that the PPDU is transmitted
through four spatial streams SS-1, SS-2, SS-3, and SS-4, when the
resource allocation information is set to `00,` it may indicate
that each of the spatial streams SS-1, SS-2, SS-3, and SS-4 is
allocated for a different station. Also, when the resource
allocation information is set to `01,` it may indicate that two
spatial streams SS-1 and SS-2 are allocated for a station, the
spatial stream SS-3 is allocated for another station, and the
spatial stream SS-4 is allocated for the other station. Also, when
the resource allocation information is set to `10,` it may indicate
that the spatial streams SS-1 and SS-3 are allocated for a station,
the spatial stream SS-2 is allocated for another station, and the
spatial stream SS-4 is allocated for the other station. Also, when
the resource allocation information is set to `11,` it may
indicated that the spatial stream SS-1 is allocated for a station,
the spatial streams SS-2 and SS-3 are allocated for another
station, and the spatial stream SS-4 is allocated for the other
station. Here, each of `00,` `01,` `10,` and `11` may be a binary
number. The set manner of the resource allocation information and
the allocation pattern of spatial streams are not restricted to the
above-described example. That is, the resource allocation
information and the allocation pattern of spatial streams may vary
according to exemplary embodiments.
[0098] Re-referring to FIG. 8, the station ID list field 813 may
include respective IDs of the stations participating in the PPDU
transmission based on the MU-MIMO among stations included in the
sub-group indicated by the sub-group ID. Here, the station ID may
be a station ID described by referring to the table 1. For example,
when the sub-group ID is set to `00`, among the STA2 to STA5, the
station ID list field 813 may include respective IDs (e.g., 00, 01,
10, and 11) of stations participating in the PPDU transmission
based on the MU-MIMO.
[0099] According to the above description, in a case that the
scheduling information `sub-group ID field 811+resource allocation
information field 812+station ID list field 813` is set to `00 00
10110100,` it may indicate that at least one data unit (e.g., MAC
protocol data unit (MPDU) or aggregated-MPDU (A-MPDU)) for the STA4
is transmitted through the spatial stream SS-1, at least one data
unit for the STA5 is transmitted through the spatial stream SS-2,
at least one data unit for the STA3 is transmitted through the
spatial stream SS-3, and at least one data unit for the STA2 is
transmitted through the spatial stream SS-4. In other words, data
units for respective stations indicated by the first, second,
third, and fourth station IDs included in the station ID list field
813 may be transmitted through each of the spatial streams SS-1,
SS-2, SS-3, and SS-4.
[0100] In a case that the scheduling information `sub-group ID
field 811+resource allocation information field 812+station ID list
field 813` is set to `00 01 100100,` it may indicate that data
units for the STA4 are transmitted through the spatial streams SS-1
and SS-2, at least one data unit for the STA3 is transmitted
through the spatial stream SS-3, and at least one data unit for the
STA2 is transmitted through the spatial stream SS-4. Here, since
the data units for the STA4 are transmitted through two contiguous
spatial streams SS-1 and SS-2, the ID of the STA4 may be included
in the station ID list field 813 only once. That is, since the
station allocated to the spatial stream SS-1 and the station
allocated to the spatial stream SS-2 are identical, the first ID
included in the station ID list field 813 may indicate not only the
station allocated to the spatial stream SS-1 but also the station
allocated to the spatial stream SS-2. Alternatively, in this case,
the scheduling information `sub-group ID field 811+resource
allocation information field 812+station ID list field 813` may be
set to `00 01 10100100.` That is, the ID of the STA4 may not be
omitted in the station ID list field 813.
[0101] In a case that the scheduling information `sub-group ID
field 811+resource allocation information field 812+station ID list
field 813` is set to `00 10 100100,` it may indicate that data
units for the STA4 are transmitted through the spatial streams SS-1
and SS-3, at least one data unit for the STA3 is transmitted
through the spatial stream SS-2, and at least one data unit for the
STA2 is transmitted through the spatial stream SS-4. Here, since
the data units for the STA4 are transmitted through two
non-contiguous spatial streams SS-1 and SS-3, the ID of the STA4
may be included in the station ID list field 813 only once. That
is, since the station allocated to the spatial stream SS-1 and the
station allocated to the spatial stream SS-3 are identical, the
first ID included in the station ID list field 813 may indicate not
only the station allocated to the spatial stream SS-1 but also the
station allocated to the spatial stream SS-3. Alternatively, in
this case, the scheduling information `sub-group ID field
811+resource allocation information field 812+station ID list field
813` may be set to `00 10 10011000.` That is, the ID of the STA4
may not be omitted in the station ID list field 813. Alternatively,
the HE-SIG field 810 (e.g., HE-SIG-A field, HE-SIG-B field, etc.)
of the HE preamble used for transmitting PPDU based on MU-MIMO may
include a sub-group ID field 811, a N.sub.STS field (not
illustrated), and a station allocation information field (not
illustrated). Also, the HE-SIG field 810 of the HE preamble may
further include a Space-Time Block Coding (STBC) field. The
sub-group ID field may indicate a sub-group ID described by
referring to the table 1. The number of spatial streams allocated
for stations indicated by the station allocation information field
may be determined according to the values which are respectively
indicated by the N.sub.STS field and the STBC field. For example,
the number of spatial streams may be determined according to the
below table 4.
TABLE-US-00004 TABLE 4 Value indicated N.sub.STS .times. N.sub.SS
by STBC field 2 .times. 1 1 3 .times. 2 1 4 .times. 2 2 4 .times. 3
1
[0102] Alternatively, the station allocation information field may
be represented in a bitmap form. For example, each of the first,
second, third, and fourth fields included in the station allocation
information field may indicate whether a spatial stream is
allocated for the STA2, STA3, STA4, and STA5 among stations
belonging to the sub-group indicated by the sub-group ID field 811.
When the station allocation information field is set to binary
number `1001,` it may indicate that the number of spatial streams
determined according to values indicated by the N.sub.STS field and
the STBC field is allocated for the STA2 and STA5, and spatial
streams are not allocated to the STA3 and STA4.
[0103] Meanwhile, the HE-SIG field 820 (e.g., HE-SIG-A field,
HE-SIG-B field, etc.) of the HE preamble used for transmitting PPDU
based on OFDMA may include at least one scheduling information
821-1, 821-2, . . . , 821-n. That is, in a case that the payload of
the PPDU is constituted by a plurality of time domains, scheduling
information for respective time domains may be included in the
HE-SIG field 820. For example, in a case that the payload of the
PPDU has a first time domain and a second time domain, the
scheduling information 821-1 for the first time domain and the
scheduling information 821-2 for the second time domain may be
included in the HE-SIG field 820. The HE-SIG field 820 may include
a sub-group ID field 821-1-1, a resource allocation information
field 821-1-2, and a station ID list field 821-1-3 as the
scheduling information. The sub-group ID field 821-1-1 may indicate
a sub-group ID described by referring to the table 1. The resource
allocation information field 821-1-2 may indicate an allocation
pattern of frequency bands.
[0104] The size of the resource allocation information field
821-1-2 may vary according to resource allocation patterns or the
number of reception stations. In a case that the size of the
resource allocation information field 821-1-2 is variable, the HE
preamble may include information indicating that the size of the
resource allocation information field 821-1-2 is variable, and may
further include information indicating the size of scheduling
information (or, the size of the resource allocation information
field 821-1-2). In this case, each of the information indicating
that the size of the resource allocation information field 821-1-2
is variable and the information indicating that the size of the
scheduling information (or, the size of the resource allocation
information field 821-1-2) may be positioned prior to the field
including the scheduling information (or, the resource allocation
information field 821-1-2) in the HE preamble.
[0105] Meanwhile, the scheduling information may be included in the
HE-SIG-A field or the HE-SIG-B field of the HE-SIG field in the HE
preamble. Among the scheduling information, common information for
reception stations may be included in the common field of the
HE-SIG-B field, and specific information for a specific reception
station may be included in the user-specific field of the HE-SIG-B
field. Alternatively, the scheduling information may be included in
the HE-SIG-A field and the HE-SIG-B field of the HE preamble. For
example, among the scheduling information, a part of common
information for reception stations may be included in the HE-SIG-A
field, and the rest of them may be included in the common field of
the HE-SIG-B field. Also, the information used for a specific
reception station may be included in the user-specific field of the
HE-SIG-B filed.
[0106] FIG. 10 is a conceptual diagram illustrating an exemplary
embodiment of an allocation pattern of frequency bands.
[0107] Referring to FIG. 10, in a case that a PPDU is transmitted
through four frequency bands FB-1, FB-2, FB-3, and FB-4, when the
resource allocation information is set to `00,` it may indicate
that the respective frequency bands FB-1, FB-2, FB-3, and FB-4 are
allocated for different stations. Also, when the resource
allocation information is set to `01,` it may indicate that two
frequency bands FB-1 and FB-2 are allocated for a station, the
frequency band FB-3 is allocated for another station, and the
frequency band FB-4 is allocated for the other station. When the
resource allocation information is set to `10` or `11,` it may
indicate the allocation pattern of frequency bands in the same
manner. Here, each of `00`, `01`, `10,` and `11` may be a binary
number.
[0108] In a case that a PPDU is transmitted through a frequency
bandwidth equal to or larger than 40 MHz, the allocation pattern of
frequency bands may be differently set in unit of predetermined
bandwidth (e.g., 20 MHz), and frequency resources within the
predetermined bandwidth may be allocated to at least one reception
station. For example, when a PPDU is transmitted through a
frequency band including contiguous first, second, . . . , nth
sub-frequency bands in unit of 20 MHz, each of odd-numbered
sub-frequency bands (e.g., first sub-frequency band, third
sub-frequency band, etc.) may be allocated according to a first
allocation pattern, and each of even-numbered sub-frequency bands
(e.g., second sub-frequency band, fourth sub-frequency band, etc.)
may be allocated according to a second allocation pattern. Here, n
is a natural number larger than 3.
[0109] The set manners of the resource allocation information and
the allocation patterns of frequency bands indicated by the
resource allocation manner are not restricted to the
above-described example, and they may vary according to exemplary
embodiments.
[0110] Re-referring to FIG. 8, the station ID list field 821-1-3
may include IDs of respective stations participating in the PPDU
transmission based on OFDMA among stations included in the
sub-group indicated by the sub-group ID. Here, the station IDs may
be station IDs described by referring to the table 1. For example,
when the sub-group ID is set to `00,` the station ID list field
821-1-3 may include IDs of the stations participating in the PPDU
transmission based on OFDMA (e.g., `00`, `01,` `10,` and `11`)
among the STA2 to STA5.
[0111] According to the above description, in a case that the
scheduling information `sub-group ID field 821-1-1+resource
allocation information field 821-1-2+station ID list field 821-1-3`
is set to `00 00 10110100,` it may indicate that data units for
each of the stations STA4, STA5, STA3, and STA2 are respectively
transmitted through each of the frequency bands FB-1, FB-2, FB-3,
and FB-4, similarly to the above-described case of the HE-SIG field
810. Also, in a case that the scheduling information `sub-group ID
field 821-1-1+resource allocation information field 821-1-2+station
ID list field 821-1-3` is set to `00 01 100100` (i.e., when data
units for a single station are transmitted through two frequency
bands FB-1 and FB-2), it may indicate that data units for the STA3
are transmitted through the frequency bands FB-1 and FB-2, and data
units of each of the STA3 and STA2 are respectively transmitted
through each of the frequency bands FB-3 and FB-4. Also, in a case
that the scheduling information `sub-group ID field
821-1-1+resource allocation information field 821-1-2+station ID
list field 821-1-3` is set to `00 10 100100` (i.e., when data units
for a single station are transmitted through non-contiguous
frequency bands FB-1 and FB-3), it may indicate that data units for
the STA4 are transmitted through frequency bands FB-1 and FB-3, and
data units for each of the STA3 and STA2 are transmitted through
each of the frequency bands FB-2 and FB-4, similarly to the case of
the HE-SIG field 810.
[0112] Meanwhile, in the transmission based on OFDMA, data for
different stations may be multiplexed and transmitted in time
domain.
[0113] FIG. 11 is a block diagram illustrating an exemplary
embodiment of a payload included in a PPDU.
[0114] Referring to FIG. 11, the PPDU payload may include a first
time domain and a second time domain. The length of the first time
domain may be identical to or different from the length of the
second time domain. The lengths of data units for respective
frequency bands FB-1, FB-2, FB-3, and FB-4 may be different in each
of the time domains. In the first time domain, a frequency band
allocation pattern may be indicated by the resource allocation
information `00` described by referring to FIG. 10. Also, in the
second time domain, a frequency band allocation pattern may be
indicated by the resource allocation information `01` described by
referring to FIG. 10. The HE-SIG field 820 may include a first
scheduling information field 821-1 including scheduling information
for the first time domain, and a second scheduling information
field 821-2 including scheduling information for the second time
domain. The first scheduling information field 821-1 may be set to
`00 00 10110100` and the second scheduling information field 821-2
may be set to `00 01 100100.`
[0115] Re-referring to FIG. 8, the HE-SIG field 830 (e.g., HE-SIG-A
field, HE-SIG-B field, etc.) of the HE preamble used for the PPDU
transmission based on MU-MIMO/OFDMA may include a group ID field
831, a first resource allocation information field 832, a sub-group
ID list field 833, and at least one SS scheduling information field
834-1, 834-2, . . . , 834-n, as scheduling information.
Alternatively, the scheduling information may be included in the
HE-SIG-A field or the HE-SIG-B field in the HE-SIG field of the HE
preamble. Among the scheduling information, common information for
reception stations may be included in a common field of the
HE-SIG-B field, and information for a specific reception station
may be included in a user-specific field of the HE-SIG-B filed.
Alternatively, the scheduling information may be included in the
HE-SIG-A field and the HE-SIG-B field in the HE-SIG field of the HE
preamble. For example, among the scheduling information, a part of
common information for reception stations may be included in the
HE-SIG-A field, and the rest of them may be included in the common
field of the HE-SIG-B field. Also, the information used for a
specific reception station may be included in the user-specific
field of the HE-SIG-B filed.
[0116] The group ID field 831 may indicate a group ID described by
referring to the table 1. The first resource allocation information
field 832 may indicate a resource allocation pattern of spatial
streams identically to the above-described resource allocation
information field 812 of the HE-SIG field 810. The size of the
first resource allocation information field 832 may vary according
to the resource allocation pattern or the number of reception
stations. In a case that the size of the first resource allocation
information field 832 is variable, the HE preamble may include
information indicating that the size of the first resource
allocation field 832 is variable and may further information
indicating the size of the scheduling information (or, the size of
the first resource allocation information field 832). In this case,
each of the information indicating that the size of the first
resource allocation information field 832 is variable and the
information indicating the size of the scheduling information (or,
the size of the first resource allocation information field 832)
may be positioned prior to the field including the scheduling
information (or, the first resource allocation information field
832) in the HE preamble.
[0117] The sub-group ID list field 833 may include respective IDs
of the sub-groups participating in the PPDU transmission based on
MU-MIMO among sub-groups included in the group indicated by the
group ID. Here, the sub-group ID may be a sub-group ID described by
referring to the table 1.
[0118] Each of the SS scheduling information fields 834-1, 834-2, .
. . , 834-n may indicate scheduling information of each PPDU
transmitted through the corresponding spatial stream. For example,
a SS-1 scheduling information field 834-1 may indicate scheduling
information of a PPDU transmitted through the spatial stream SS-1.
The number of the SS scheduling information fields 834-1, 834-2, .
. . , 834-n may correspond to the number of spatial streams through
which PPDUs are transmitted. For example, when PPDUs are
transmitted through four spatial streams, the HE-SIG field 830 may
include four SS scheduling information fields 834-1, 834-2, 834-3,
and 834-4.
[0119] Each of the SS scheduling fields 834-1, 834-2, . . . , 834-n
may include at least one scheduling information fields (e.g.,
834-1-1, 834-1-2, . . . , 834-1-n). That is, when the PPDU payload
includes multiple time domains, scheduling information for each of
the multiple time domains may be included in the SS scheduling
information fields 834-1, 834-2, . . . , 834-n. For example, when
the PPDU payload includes the first time domain and the second time
domain, scheduling information 834-1-1 for the first time domain
and scheduling information 834-1-2 for the second time domain may
be included in the SS-1 scheduling information field 834-1.
[0120] The first scheduling information field 834-1-1 may include a
sub-group ID field 834-1-1-1, a second resource allocation
information field 834-1-1-2, and a station ID list field 834-1-1-3.
The sub-group ID field 834-1-1-1 may indicate a sub-group ID
described by referring to the table 1. The second resource
allocation information field 834-1-1-2 may indicate an allocation
pattern of frequency bands, identically to the above-described
resource allocation information field 821-1-2 of the HE-SIG field
820. The size of the second resource allocation information field
834-1-1-2 may vary according to the resource allocation pattern or
the number of reception stations. In a case that the size of the
second resource allocation information field 834-1-1-2 is variable,
the HE preamble may include information indicating that the size of
the second resource allocation information field 834-1-1-2 is
variable and may further information indicating the size of the
scheduling information (or, the size of the second resource
allocation information field 834-1-1-2). In this case, each of the
information indicating that the size of the second resource
allocation information field 834-1-1-2 is variable and the
information indicating the size of the scheduling information (or,
the size of the second resource allocation information field
834-1-1-2) may be positioned prior to the field including the
scheduling information (or, the second resource allocation
information field 834-1-1-2) in the HE preamble.
[0121] The station ID list field 834-1-1-3 may include respective
IDs of the stations participating in the PPDU transmission based on
the OFDMA among stations included in the sub-group indicated by the
sub-group ID. Here, the station ID may be a station ID described by
referring to the table 1. That is, `sub-group ID field
834-1-1-1+second resource allocation information field
834-1-1-2+station ID list field 834-1-1-3` may act the same role as
that of `sub-group ID list field 821-1-1+resource allocation
information field 821-1-2+station ID list field 821-1-3` included
in the above-described HE-SIG field 820.
[0122] Re-referring to FIG. 7, the HE-SIG-B field may include
information needed for reception of the corresponding payload. The
HE-SIG-B field may include different information for each of the
frequency bands FB-1, FB-2, FB-3, and FB-4. Also, the HE-SIG-B
field may include a second indicator on whether the corresponding
payload includes multiple time domains (or, whether data for
different stations are multiplexed and transmitted in time domain).
For example, when the second indicator is set to `0,` it may
indicate that the corresponding payload includes a single time
domain, and when the second indicator is set to `1,` it may
indicate that the corresponding payload includes multiple time
domains (e.g., time domains illustrated in FIG. 11).
[0123] Also, the HE-SIG-B field may include a third indicator on
whether the corresponding payload includes data units belonging to
different access categories (e.g. AC_VO, AC_VI, AC_BE, and AC_BK).
For example, when the third indicator is set to `0,` it may
indicate that the corresponding payload includes at least one data
unit belonging to a single access category (AC), and when the third
indicator is set to `1,` it may indicate that the corresponding
payload includes data units belonging to different access
categories. Here, the HE-SIG-B field may further include a traffic
ID (TID) list field. The TID list field may include TIDs for access
categories to which each of data units included in the payload
belongs.
[0124] Also, the HE-SIG-B field may further include a fourth
indicator on whether the corresponding payload includes data units
having different frame formats (e.g., control frame, management
frame, and data frame). For example, when the fourth indicator is
set to `0,` it may indicate that the payload includes data units
belonging to a single frame format, and when the fourth indicator
is set to `1,` it may indicate that the payload includes data units
belonging to different frame formats. Here, the HE-SIG-B field may
further include a frame format ID list field. The frame format ID
list field may include frame format IDs for respective data units
included in the payload. For example, in a case that frame format
IDs `00,` `01,` and `10` respectively indicate a control frame, a
management frame, and a data frame, when the frame format ID is set
to `0010,` it may indicate that the payload includes a data unit
having a control frame format and a data unit having a data frame
format.
[0125] The payload including data units belonging to different
access categories or data units having different MAC frame formats
may have the following structure.
[0126] FIG. 12 is a block diagram illustrating another exemplary
embodiment of a payload included in a PPDU.
[0127] Referring to FIG. 12, the payload may include A-MPDUs
belonging to different access categories or A-MPDUs having
different MAC frame formats. For example, the payload may include
A-MPDU subframes 1210-1 and 1210-2 belonging to AC_VO (or, having a
data frame format), a Null subframe 1220, A-MPDU subframes 1230-1
and 1230-2 belonging to AC_BE (or, having a control frame format),
and a pad field 1240. The Null subframe 1220 may be located between
A-MPDUs belonging to different access categories (or, between
A-MPDUs having different frame formats). At least one Null subframe
1220 may be included in the payload, and each of the multiple Null
subframes may have the same information.
[0128] The Null subframe 1220 may include a reserved field 1221, an
End-of-AC (EOA) field (or, End-of-Type (EOT) field) 1222, a length
field 1223, a cyclic redundancy check (CRC) field 1224, and a
delimiter signature field 1225. The EOA field 1222 may indicate
that an AC to which the A-MPDU subframes 1230-1 and 1230-2
subsequent to the Null subframe 1220 belong is different from an AC
to which the A-MPUD subframes 1210-1 and 1210-2 prior to the Null
subframe 1220 belong. That is, the EOA field 1222 may indicate an
end of A-MPDU subframes 1210-1 and 1210-2 belonging to AC_VO.
Alternatively, the EOT field 1222 may indicate that a frame format
of the A-MPDU subframes 1230-1 and 1230-2 subsequent to the Null
subframe 1220 is different from a frame format of the A-MPUD
subframes 1210-1 and 1210-2 prior to the Null subframe 1220. That
is, the EOT field 1222 may indicate an end of A-MPDU subframes
1210-1 and 1210-2 having a data frame format. The length field 1223
may indicate the length of a MPDU included in the Null subframe
1220, and may be set to `0.`
[0129] Re-referring to FIG. 7, the HE-SIG-B field may include
modulation and coding scheme (MCS) index information and length
information for the corresponding payload. The length information
may indicate a length from an end point (or, a start point of the
payload) of the HE-SIG-B field to an end point of a data unit
included in the payload (e.g., a start point of the pad field).
When the payload include a plurality of time domains, the HE-SIG-B
field may include MSC index information and length information for
each of the plurality of time domains. For example, in the case of
the PPDU payload illustrated in FIG. 11, the HE-SIG-B field may
include a HE-SIG-B1 field for the first time domain and a HE-SIG-B2
field for the second time domain. The HE-SIG-B1 field may include
MCS index information and length information for the first time
domain. Here, the length information may indicate a length from a
start point of the payload (or, an end point of the HE-SIG-B1
field) to an end point of the data unit belonging to the first time
domain. The HE-SIG-B2 field may include MCS index information and
length information for the second time domain. Here, the length
information may indicate a length from a start point of the second
time domain to an end point of the data unit belonging to the
second time domain.
[0130] Also, in a case that the payload includes data units
belonging to different access categories (or, data units having
different MAC frame formats), the HE-SIG-B field may include MCS
index information and length information for each of the multiple
data units. Here, the length information may be included in a
header of the payload. For example, in the payload of the PPDU
illustrated in FIG. 12, the HE-SIG-B field may include a HE-SIG-B1
field for A-MPDU subframes 1210-1 and 1210-2 belonging to AC_VO
(or, A-MPDU subframes having a data frame format) and a HE-SIG B2
field for A-MPDU subframes 1230-1 and 1230-2 belonging to AC_BE
(or, A-MPDU subframes having a control frame format). The HE-SIG-B1
field may include MCS index information and length information of
the A-MPDU subframes 1210-1 and 1210-2. Here, the length
information may indicate a length from a start point of the payload
(or, an end point of the HE-SIG-B1 field) to an end point of the
A-MPDU subframe 1210-2 (e.g., a start point of the Null subframe
1220). The HE-SIG-B2 field may include MCS index information and
length information for the A-MPDU subframe 1230-1 and 1230-2. Here,
the length information may indicate a length from a start point of
the A-MPDU subframe 1230-1 (e.g., an end point of the Null subframe
1220) to an end point of the A-MPDU subframe 1230-2.
[0131] Re-referring to FIG. 6, the STA1 may transmit the PPDU
generated in the above-described manner based on multi-user
transmission (S602). In a case that the PPDU is transmitted based
on MU-MIMO, the STA1 may transmit the PPDU to one of the STA2 to
STA5 through the spatial stream SS-1, and transmit the PPDU to one
of the STA6 to STA9 through the spatial stream SS-2. In a case that
the PPDU is transmitted based on OFDMA, the STA1 may transmit the
PPDU to the STA2 to STA9. In a case that the PPDU is transmitted
based on MU-MIMO/OFDMA, the STA1 may transmit the PPDU to the STA2
to STA9 in the OFDMA through the spatial stream SS-1, and transmit
the PPDU to the STA2 to STA9 in the OFDMA through the spatial
stream SS-2.
[0132] Meanwhile, upon receiving the PPDU, reception stations
(e.g., the STA2 to STA9) may obtain the legacy preamble and the HE
preamble of the PPDU, and obtain the first indicator included in
the HE-SIG-A field of the HE preamble. Since the first indicator
indicates a transmission manner described in the table 2, the
reception stations may identify a transmission manner of the
corresponding PPDU by using the first indicator. Since scheduling
information is varied according to the transmission manner of the
PPDU, the reception stations predict which scheduling information
is transmitted. For example, when the reception station identifies
that the PPDU is transmitted based on MU-MIMO, the reception
station may predict that the `sub-group ID field 811+resource
allocation information field 812+station ID list field 813`
illustrated in FIG. 8 is transmitted as scheduling information, and
the reception station may identify a resource (e.g., spatial
stream) through which its data can be received. The reception
station may obtain information needed for receiving a data unit
(e.g., MCS index information, length information, etc.) by
receiving the HE-SIG-B field related to the identified resource,
and receive and decode the data unit based on the obtained
information.
[0133] Also, when the reception station identifies that the PPDU is
transmitted based on OFDMA, the reception station may predict that
the `at least one scheduling information field 821-1, 821-2, . . .
, 821-n` illustrated in FIG. 8 is transmitted as scheduling
information, and the reception station may identify a resource
(e.g., frequency and time) through which its data can be received
by receiving the scheduling information. The reception station may
obtain information needed for receiving a data unit (e.g., MCS
index information, length information, etc.) by receiving the
HE-SIG-B field related to the identified resource, and receive and
decode the data unit based on the obtained information.
[0134] Also, when the reception station identifies that the PPDU is
transmitted based on MU-MIMO/OFDMA, the reception station may
predict that the `group ID field 831+first resource allocation
information field 832+sub-group ID list field 833+at least one SS
scheduling information field 834-1, 834-2, . . . , 834-n`
illustrated in FIG. 8 is transmitted as scheduling information, and
the reception station may identify a resource (e.g., spatial
stream, time, frequency) through which its data can be received.
The reception station may obtain information needed for receiving a
data unit (e.g., MCS index information, length information, etc.)
by receiving the HE-SIG-B field related to the identified resource,
and receive and decode the data unit based on the obtained
information.
[0135] For example, when the first scheduling information field
821-1 and the second scheduling information field 821-2 are
respectively set to `00 00 10110100` and `00 01 100100,` the STA4
may receive and decode at least one data unit transmitted through
the first frequency band FB-1 in the first time domain, and receive
and decode data units transmitted through the frequency bands FB-1
and FB-2 in the second time domain. Meanwhile, the STA4 may receive
a pilot signal transmitted through the frequency band FB-2 in the
first time domain, and decode the data unit based on the pilot
signal. That is, when the length of the data unit received in the
first time domain is longer than a predetermined length, error of
channel estimation based on the HE-STF, the HE-LTF, and so on may
be increased. In this case, the STA4 can perform channel estimation
(e.g., phase-tracking) by receiving the pilot signal transmitted
through the first frequency band FB-1 in the first time domain
before it receives the data transmitted through the second
frequency band FB-2 in the second time domain.
[0136] When the reception station successfully receives the data,
in response to the data, the reception station may transmit a
response frame (e.g. an acknowledgement (ACK) frame) to the STA1
(S603, S604). The response frame may be transmitted in various
manners. For example, according to the above-described FIG. 11,
when the first scheduling information field 821-1 and the second
scheduling information field 821-2 are respectively set to `00 00
10110100` and `00 01 100100,` each of the STA4, STA5, STA3, and
STA2 may transmit a response frame to the STA1 in a third time
domain (not illustrated), as a response corresponding to the data
unit received in the first time domain. In this case, each of the
STA4, STA5, STA3, and STA2 may transmit the response frame to the
STA1 in one or more manners including OFDMA, code division multiple
access (CDMA), sequential transmission manner, etc. Here, when the
sequential transmission manner is used, the STA4, STA5, STA3, and
STA2 may sequentially transmit their response frames to the STA1 in
the third time domain. The interval between the response frames
transmitted by the STA4, STA5, STA3, and STA2 may be a SIFS. The
third time domain may be a time domain after a SIFS from an end of
the PPDU transmitted from the STA1, or may be indicated by the
STA1. For example, the STA1 may indicate information on a resource
allocated for the third time domain by transmitting a first request
frame after the PPDU transmission, and request a transmission of
the response frame in the third time domain as the response of the
data unit. The first request frame may be a frame performing
function of a block ACK request (BAR) frame, a beamforming poll
frame, etc.
[0137] Also, each of the STA4, STA3, and STA2 may transmit a
response frame for the data unit received in the second time domain
to the STA1 in a fourth time domain (not illustrated). Identically
to the above-described transmission manner of the response frame in
the third time domain, the STA4, STA3, and STA2 may transmit the
response frames to the STA1. Here, the fourth time domain may be
indicated by the above-described first request frame, or indicated
by a second request frame transmitted by the STA1 after the third
time domain.
[0138] Also, the response frames for the data units transmitted in
the first time domain and the second time domain may be aggregated
into a single response frame, and the single response frame is
transmitted. For example, the response frames for the data units
transmitted to the STA4 through the first frequency band FB-1 in
the first time domain and the second time domain may be aggregated
into a single response frame, and the single response frame may be
transmitted to the STA1 in the third time domain. Also, the
response frames for the data units transmitted respectively to the
STA3 and STA4 through the second frequency band FB-2 in the first
time domain and the second time domain may be aggregated into a
single response frame, and the single response frame may be
transmitted to the STA1 in the third time domain. Also, the
response frames for the data units transmitted through the
frequency bands FB-3 and FB-4 may be transmitted to the STA1 in the
third time domain in the manner identical to the above-described
manner.
[0139] Meanwhile, when the STA1 receives the response frames
respectively from the STA2 to STA9, the STA1 may determine that the
data is successfully received at the corresponding station.
[0140] While the example embodiments of the present disclosure and
their advantages have been described in detail, it should be
understood that various changes, substitutions and alterations may
be made herein without departing from the scope of the
disclosure.
* * * * *