U.S. patent application number 16/716170 was filed with the patent office on 2020-07-16 for sounding and tone block allocation for orthogonal frequency division multiple access (ofdma) in wireless local area networks.
The applicant listed for this patent is NXP USA, Inc.. Invention is credited to Liwen CHU, Hui-Ling LOU, Yakun SUN, Hongyuan ZHANG.
Application Number | 20200228379 16/716170 |
Document ID | 20200228379 / US20200228379 |
Family ID | 52021475 |
Filed Date | 2020-07-16 |
Patent Application | download [pdf] |
![](/patent/app/20200228379/US20200228379A1-20200716-D00000.png)
![](/patent/app/20200228379/US20200228379A1-20200716-D00001.png)
![](/patent/app/20200228379/US20200228379A1-20200716-D00002.png)
![](/patent/app/20200228379/US20200228379A1-20200716-D00003.png)
![](/patent/app/20200228379/US20200228379A1-20200716-D00004.png)
![](/patent/app/20200228379/US20200228379A1-20200716-D00005.png)
![](/patent/app/20200228379/US20200228379A1-20200716-D00006.png)
![](/patent/app/20200228379/US20200228379A1-20200716-D00007.png)
![](/patent/app/20200228379/US20200228379A1-20200716-D00008.png)
![](/patent/app/20200228379/US20200228379A1-20200716-D00009.png)
![](/patent/app/20200228379/US20200228379A1-20200716-D00010.png)
View All Diagrams
United States Patent
Application |
20200228379 |
Kind Code |
A1 |
ZHANG; Hongyuan ; et
al. |
July 16, 2020 |
SOUNDING AND TONE BLOCK ALLOCATION FOR ORTHOGONAL FREQUENCY
DIVISION MULTIPLE ACCESS (OFDMA) IN WIRELESS LOCAL AREA
NETWORKS
Abstract
A first communication device transmits a null data packet (NDP)
to multiple second communication devices. The NDP spans a channel
frequency bandwidth. The first communication device receives a
plurality of sounding feedback packets from the second
communication devices. Each sounding feedback packet includes one
or more signal-to-noise ratio (SNR) indicators corresponding to one
or more respective groups of orthogonal frequency division
multiplexing (OFDM) subcarriers, and the SNR indicators correspond
to reception of the NDP at the plurality of second communication
devices. Each sounding feedback packet in the plurality of sounding
feedback packets includes a respective indication of OFDM
subcarriers for which the sounding feedback packet includes SNR
information, and at least one sounding feedback packet from among
the plurality of sounding feedback packets does not include SNR
information for all OFDM subcarriers via which the NDP was
transmitted.
Inventors: |
ZHANG; Hongyuan; (Fremont,
CA) ; SUN; Yakun; (San Jose, CA) ; LOU;
Hui-Ling; (Sunnyvale, CA) ; CHU; Liwen; (San
Ramon, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NXP USA, Inc. |
Austin |
TX |
US |
|
|
Family ID: |
52021475 |
Appl. No.: |
16/716170 |
Filed: |
December 16, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
16126678 |
Sep 10, 2018 |
10511471 |
|
|
16716170 |
|
|
|
|
15295685 |
Oct 17, 2016 |
10075318 |
|
|
16126678 |
|
|
|
|
14555183 |
Nov 26, 2014 |
9473341 |
|
|
15295685 |
|
|
|
|
61938441 |
Feb 11, 2014 |
|
|
|
61909700 |
Nov 27, 2013 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/0048 20130101;
H04B 17/318 20150115; H04W 4/08 20130101; H04B 17/336 20150115;
H04W 72/0453 20130101; H04B 7/0632 20130101; H04W 84/12 20130101;
H04L 27/2646 20130101; H04L 5/0094 20130101; H04L 5/0053 20130101;
H04W 72/08 20130101; H04L 5/0037 20130101; H04W 72/082 20130101;
H04L 5/0007 20130101 |
International
Class: |
H04L 27/26 20060101
H04L027/26; H04W 4/08 20060101 H04W004/08; H04L 5/00 20060101
H04L005/00; H04W 72/08 20060101 H04W072/08; H04B 17/318 20060101
H04B017/318; H04B 17/336 20060101 H04B017/336; H04B 7/06 20060101
H04B007/06; H04W 72/04 20060101 H04W072/04 |
Claims
1. A method for simultaneously communicating with multiple
communication devices in a communication network, the method
comprising: transmitting, by a first communication device, a null
data packet (NDP) to a plurality of second communication devices,
wherein the NDP spans a channel frequency bandwidth, and wherein
the NDP is transmitted via a plurality of orthogonal frequency
division multiplexing (OFDM) subcarriers that span the channel
frequency bandwidth; receiving, at the first communication device,
a plurality of sounding feedback packets from the plurality of
second communication devices, wherein each sounding feedback packet
includes one or more signal-to-noise ratio (SNR) indicators
corresponding to one or more respective groups of OFDM subcarriers
from among the plurality of OFDM subcarriers, wherein the SNR
indicators correspond to reception of the NDP at the plurality of
second communication devices, wherein each sounding feedback packet
in the plurality of sounding feedback packets includes a respective
indication of OFDM subcarriers for which the sounding feedback
packet includes SNR information, and wherein at least one sounding
feedback packet from among the plurality of sounding feedback
packets does not include SNR information for all OFDM subcarriers
via which the NDP was transmitted; allocating, at the first
communication device, respective sets of OFDM subcarriers to second
communication devices in a group of second communication devices
for an OFDMA communication, wherein the first communication device
uses the received SNR indicators to allocate the sets of OFDM
subcarriers; and at least one of: transmitting, by the first
communication device to the group of second communication devices,
a downlink OFDMA transmission that includes respective data
directed to the second communication devices in the group, wherein
the respective data are transmitted via respective sets of OFDM
subcarriers that were allocated to the second communication devices
in the group, and receiving, at the first communication device, an
uplink OFDMA transmission from the group of second communication
devices, wherein the uplink OFDMA transmission includes respective
data from the second communication devices in the group, wherein
the respective data are transmitted via respective sets of OFDM
subcarriers that were allocated to the second communication devices
in the group.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/126,678, now U.S. Pat. No. 10,511,471,
filed Sep. 10, 2018, entitled "Sounding and Tone Block Allocation
for Orthogonal Frequency Division Multiple Access (OFDMA) in
Wireless Local Area Networks," which is a continuation of U.S.
patent application Ser. No. 15/295,685, now U.S. Pat. No.
10,075,318, filed Oct. 17, 2016, entitled "Sounding and Tone Block
Allocation for Orthogonal Frequency Multiple Access (OFDMA) in
Wireless Local Area Networks," which is a continuation of U.S.
patent application Ser. No. 14/555,183, now U.S. Pat. No.
9,473,341, filed Nov. 26, 2014, entitled "Sounding and Tone Block
Allocation for Orthogonal Frequency Multiple Access (OFDMA) in
Wireless Local Area Networks," which claims the benefit of U.S.
Provisional Patent Application Nos. 61/909,700, filed Nov. 27,
2013, and 61/938,441, filed Feb. 11, 2014, both entitled "OFDMA for
WLAN: Sounding and Tone-Block Allocation." The disclosures of all
of the applications referenced above are hereby expressly
incorporated herein by reference in their entireties.
[0002] This application is also related to U.S. patent application
Ser. No. 15/137,901, now U.S. Pat. No. 10,103,923, entitled
"Sounding and Tone Block Allocation for Orthogonal Frequency
Multiple Access (OFDMA) in Wireless Local Area Networks," which is
a divisional of U.S. patent application Ser. No. 14/555,183. U.S.
patent application Ser. No. 15/137,901 is hereby expressly
incorporated herein by reference in its entirety.
FIELD OF THE DISCLOSURE
[0003] The present disclosure relates generally to communication
networks and, more particularly, to wireless local area networks
that utilize orthogonal frequency division multiplexing (OFDM).
BACKGROUND
[0004] When operating in an infrastructure mode, wireless local
area networks (WLANs) typically include an access point (AP) and
one or more client stations. WLANs have evolved rapidly over the
past decade. Development of WLAN standards such as the Institute
for Electrical and Electronics Engineers (IEEE) 802.11a, 802.11b,
802.11g, and 802.11n Standards has improved single-user peak data
throughput. For example, the IEEE 802.11b Standard specifies a
single-user peak throughput of 11 megabits per second (Mbps), the
IEEE 802.11a and 802.11g Standards specify a single-user peak
throughput of 54 Mbps, the IEEE 802.11n Standard specifies a
single-user peak throughput of 600 Mbps, and the IEEE 802.11ac
Standard specifies a single-user peak throughput in the gigabits
per second (Gbps) range. Future standards promise to provide even
greater throughputs, such as throughputs in the tens of Gbps
range.
SUMMARY
[0005] In an embodiment, a method for simultaneously communicating
with multiple communication devices in a communication network
includes: transmitting, by a first communication device, a null
data packet (NDP) to a plurality of second communication devices,
wherein the NDP spans a channel frequency bandwidth, and wherein
the NDP is transmitted via a plurality of orthogonal frequency
division multiplexing (OFDM) subcarriers that span the channel
frequency bandwidth; and receiving, at the first communication
device, a plurality of sounding feedback packets from the plurality
of second communication devices. Each sounding feedback packet
includes one or more signal-to-noise ratio (SNR) indicators
corresponding to one or more respective groups of OFDM subcarriers
from among the plurality of OFDM subcarriers, and the SNR
indicators correspond to reception of the NDP at the plurality of
second communication devices. Each sounding feedback packet in the
plurality of sounding feedback packets includes a respective
indication of OFDM subcarriers for which the sounding feedback
packet includes SNR information, and at least one sounding feedback
packet from among the plurality of sounding feedback packets does
not include SNR information for all OFDM subcarriers via which the
NDP was transmitted. The method also includes: allocating, at the
first communication device, respective sets of OFDM subcarriers to
second communication devices in a group of second communication
devices for an OFDMA communication, wherein the first communication
device uses the received SNR indicators to allocate the sets of
OFDM subcarriers. The method further includes, at least one of: i)
transmitting, by the first communication device to the group of
second communication devices, a downlink OFDMA transmission that
includes respective data directed to the second communication
devices in the group, wherein the respective data are transmitted
via respective sets of OFDM subcarriers that were allocated to the
second communication devices in the group; and ii) receiving, at
the first communication device, an uplink OFDMA transmission from
the group of second communication devices, wherein the uplink OFDMA
transmission includes respective data from the second communication
devices in the group, wherein the respective data are transmitted
via respective sets of OFDM subcarriers that were allocated to the
second communication devices in the group.
[0006] In another embodiment, an apparatus for use in a
communication system comprises: a network interface device
associated with a first communication device. The network interface
device includes one or more integrated circuits (ICs) configured
to: transmit a null data packet (NDP) to a plurality of second
communication devices, wherein the NDP spans a channel frequency
bandwidth, and wherein the NDP is transmitted via a plurality of
orthogonal frequency division multiplexing (OFDM) subcarriers that
span the channel frequency bandwidth, and receive a plurality of
sounding feedback packets from the plurality of second
communication devices. Each sounding feedback packet includes one
or more signal-to-noise ratio (SNR) indicators corresponding to one
or more respective groups of OFDM subcarriers from among the
plurality of OFDM subcarriers, and the SNR indicators correspond to
reception of the NDP at the plurality of second communication
devices. Each sounding feedback packet in the plurality of sounding
feedback packets includes a respective indication of OFDM
subcarriers for which the sounding feedback packet includes SNR
information, and at least one sounding feedback packet from among
the plurality of sounding feedback packets does not include SNR
information for all OFDM subcarriers via which the NDP was
transmitted. The one or more ICs are further configured to:
allocate respective sets of OFDM subcarriers to second
communication devices in a group of second communication devices
for an OFDMA communication, wherein the first communication device
uses the received SNR indicators to allocate the sets of OFDM
subcarriers. The one or more ICs are further configured to, at
least one of: i) transmit, to the group of second communication
devices, a downlink OFDMA transmission that includes respective
data directed to the second communication devices in the group,
wherein the respective data are transmitted via respective sets of
OFDM subcarriers that were allocated to the second communication
devices in the group; and ii) receive an uplink OFDMA transmission
from the group of second communication devices, wherein the uplink
OFDMA transmission includes respective data from the second
communication devices in the group, wherein the respective data are
transmitted via respective sets of OFDM subcarriers that were
allocated to the second communication devices in the group.
[0007] In yet another embodiment, a method for communicating via
orthogonal frequency division multiple access (OFDMA) includes:
receiving, at a first communication device, a null data packet
(NDP) from a second communication device, wherein the NDP spans a
channel frequency bandwidth, and wherein the NDP is received via a
plurality of orthogonal frequency division multiplexing (OFDM)
subcarriers that span the channel frequency bandwidth; determine,
at the first communication device, one or more signal-to-noise
ratio (SNR) measurements corresponding to one or more respective
groups of OFDM subcarriers from among the plurality of OFDM
subcarriers, wherein the SNR measurements correspond to reception
of the NDP at the first communication device; and transmit, at the
first communication device, a sounding feedback packet to the
second communication device. The sounding feedback packet includes
one or more SNR indicators corresponding to the one or more SNR
measurements, and the sounding feedback packet does not include SNR
information for all OFDM subcarriers via which the NDP was
received. The sounding feedback packet includes an indication of
the OFDM subcarriers for which the sounding feedback packet
includes SNR information. The method also includes: receiving, at
the first communication device, allocation information from the
second communication device, wherein the allocation information
indicates a set of OFDM subcarriers allocated to the first
communication devices for an OFDMA communication, and wherein the
allocation information is received from the second communication
device in response to transmitting the sounding feedback packet to
the second communication device. The method further includes, at
least one of: i) receiving, at the first communication device, a
downlink OFDMA transmission from the second communication device,
wherein the downlink OFDMA transmission includes respective data
directed to the first communication devices and one or more third
communication devices, wherein the data directed to the first
communication device is transmitted via the set of OFDM subcarriers
indicated by the allocation information; and ii) transmitting, by
the first communication device, an uplink transmission as part of
an uplink OFDMA transmission from a group comprising the first
communication device and the one or more third communication
devices, wherein the uplink transmission by the first communication
device is transmitted via the set of OFDM subcarriers indicated by
the allocation information.
[0008] In yet another embodiment, an apparatus for use in a
communication system comprises: a network interface device
associated with a first communication device. The network interface
device comprising one or more integrated circuits (ICs) configured
to: receive a null data packet (NDP) from a second communication
device, wherein the NDP spans a channel frequency bandwidth, and
wherein the NDP is received via a plurality of orthogonal frequency
division multiplexing (OFDM) subcarriers that span the channel
frequency bandwidth; determine one or more signal-to-noise ratio
(SNR) measurements corresponding to one or more respective groups
of OFDM subcarriers from among the plurality of OFDM subcarriers,
wherein the SNR measurements correspond to reception of the NDP at
the first communication device; and transmit a sounding feedback
packet to the second communication device. The sounding feedback
packet includes one or more SNR indicators corresponding to the one
or more SNR measurements, and the sounding feedback packet does not
include SNR information for all OFDM subcarriers via which the NDP
was received. The sounding feedback packet includes an indication
of the OFDM subcarriers for which the sounding feedback packet
includes SNR information. The one or more ICs are further
configured to: receive allocation information from the second
communication device, wherein the allocation information indicates
a set of OFDM subcarriers allocated to the first communication
devices for an OFDMA communication, and wherein the allocation
information is received from the second communication device in
response to transmitting the sounding feedback packet to the second
communication device. The one or more ICs are further configured
to, at least one of: i) receive a downlink OFDMA transmission from
the second communication device, wherein the downlink OFDMA
transmission includes respective data directed to the first
communication devices and one or more third communication devices,
wherein the data directed to the first communication device is
transmitted via the set of OFDM subcarriers indicated by the
allocation information; and ii) transmit an uplink transmission as
part of an uplink OFDMA transmission from a group comprising the
first communication device and the one or more third communication
devices, wherein the uplink transmission by the first communication
device is transmitted via the set of OFDM subcarriers indicated by
the allocation information.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 a block diagram of an example wireless local area
network (WLAN), according to an embodiment;
[0010] FIGS. 2A, 2B, 2C, and 2D are diagrams illustrating example
orthogonal frequency division multiplexing (OFDM) sub-channel
blocks for an 80 MHz communication channel, according to an
embodiment;
[0011] FIG. 3 is a diagram of an example OFDMA data unit, according
to an embodiment.
[0012] FIG. 4A is a timing diagram of an example explicit sounding
procedure and transmission of an example OFDMA data unit formed
according to grouping and/or channel allocation determined based on
the explicit sounding procedure, according to an embodiment.
[0013] FIG. 4B is a diagram of a feedback packet that a transmitted
during the sounding procedure of FIG. 4A, according to an
embodiment.
[0014] FIG. 4C is a diagram of a feedback packet that a transmitted
during the sounding procedure of FIG. 4A, according to another
embodiment.
[0015] FIG. 5 is a timing diagram of an example implicit sounding
procedure and transmission of an example OFDMA data unit formed
according to grouping and/or channel allocation determined based
the implicit sounding procedure, according to an embodiment.
[0016] FIG. 6 is a timing diagram of an example transparent
implicit sounding procedure and transmission of an example OFDMA
data unit formed according to grouping and/or channel allocation
determined based the transparent implicit sounding procedure,
according to an embodiment.
[0017] FIG. 7 is a timing diagram illustrating a notification
procedure used by an AP to inform a plurality of client stations
that the client stations are members of a group of client stations
for OFDMA communication, according to an embodiment.
[0018] FIG. 8 is a timing diagram illustrating a notification
procedure used by an AP to inform a plurality of client stations
that the client stations are members of a group of client stations
for OFDMA communication, according to another embodiment.
[0019] FIG. 9 is a flow diagram of an example method for
simultaneously communicating with multiple communication devices in
a WLAN, according to an embodiment.
[0020] FIG. 10 is a flow diagram of an example method for
simultaneously communicating with multiple communication devices in
a WLAN, according to another embodiment.
DETAILED DESCRIPTION
[0021] In embodiments described below, a wireless network device
such as an access point (AP) of a wireless local area network
(WLAN) simultaneously transmits independent data streams to
multiple client stations and/or receives independent data streams
simultaneously transmitted by multiple client stations. In
particular, the AP transmits data for the multiple clients in
different orthogonal frequency division multiplexing (OFDM)
sub-channel blocks of an orthogonal frequency division multiple
access (OFDMA) transmission, in an embodiment. Similarly, multiple
client stations transmit data to the AP simultaneously, in
particular, each client station transmits data in a different OFDM
sub-channel block of an OFDMA transmission, in an embodiment.
[0022] In an embodiment, the AP is configured obtain, for each
client station of a plurality of client stations, one or more
quality indicators corresponding to one or more sub-channel blocks
of an OFDM channel associated with the client station. Based on the
one or more quality indicators of one or more sub-channel blocks
received from each of one or more client stations, the AP selects
client stations to be included in a group of client stations for
OFDMA communication with the client stations and/or allocates
respective sub-channel blocks to client stations in a group of
client stations for OFDMA communication with the client stations.
The AP then communicates with the client stations in a group of
client station by simultaneously transmitting data to the client
stations in the respective sub-channel blocks allocated to the
client stations and/or receiving data simultaneously transmitted by
the client stations in the respective sub-channel blocks allocated
to the client stations, in an embodiment.
[0023] FIG. 1 is a block diagram of an example wireless local area
network (WLAN) 10, according to an embodiment. An AP 14 includes a
host processor 15 coupled to a network interface 16. The network
interface 16 includes a medium access control (MAC) processing unit
18 and a physical layer (PHY) processing unit 20. The PHY
processing unit 20 includes a plurality of transceivers 21, and the
transceivers 21 are coupled to a plurality of antennas 24. Although
three transceivers 21 and three antennas 24 are illustrated in FIG.
1, the AP 14 includes different numbers (e.g., 1, 2, 4, 5, etc.) of
transceivers 21 and antennas 24 in other embodiments.
[0024] The WLAN 10 includes a plurality of client stations 25.
Although four client stations 25 are illustrated in FIG. 1, the
WLAN 10 includes different numbers (e.g., 1, 2, 3, 5, 6, etc.) of
client stations 25 in various scenarios and embodiments. Two or
more of the client stations 25 are configured to receive
corresponding data streams that are transmitted simultaneously by
the AP 14. Additionally, two or more of the client stations 25 are
configured to transmit corresponding data streams to the AP 14 such
that the AP 14 receives the data streams simultaneously.
[0025] A client station 25-1 includes a host processor 26 coupled
to a network interface 27. The network interface 27 includes a MAC
processing unit 28 and a PHY processing unit 29. The PHY processing
unit 29 includes a plurality of transceivers 30, and the
transceivers 30 are coupled to a plurality of antennas 34. Although
three transceivers 30 and three antennas 34 are illustrated in FIG.
1, the client station 25-1 includes different numbers (e.g., 1, 2,
4, 5, etc.) of transceivers 30 and antennas 34 in other
embodiments.
[0026] In an embodiment, one or more of the client stations 25-2,
25-3, and 25-4 has a structure the same as or similar to the client
station 25-1. In these embodiments, the client stations 25
structured like the client station 25-1 have the same or a
different number of transceivers and antennas. For example, the
client station 25-2 has only two transceivers and two antennas (not
shown), according to an embodiment.
[0027] In an embodiment, the AP 14 is configured to transmit
different OFDM units to different client stations 25 simultaneously
by forming an OFDMA data unit that includes the different OFDM data
units modulated in respective sub-channel blocks of the OFDMA data
unit. In an embodiment, the AP 14 allocates different sub-channels
to different client stations and forms the OFDMA data unit that
includes OFDM data units directed to by modulating the different
client stations in sub-channel blocks corresponding to the
sub-channels assigned to the client stations.
[0028] FIGS. 2A, 2B, 2C and 2D are diagrams illustrating example
OFDM sub-channel blocks for an 80 MHz communication channel,
according to an embodiment. In FIG. 2A, the communication channel
is partitioned into four contiguous OFDM sub-channel blocks, each
having a bandwidth of 20 MHz. The OFDM sub-channel blocks include
independent data streams for four client stations. In FIG. 2B, the
communication channel is partitioned into two contiguous OFDM
sub-channel blocks, each having a bandwidth of 40 MHz. The OFDM
sub-channel blocks include independent data streams for two client
stations. In FIG. 2C, the communication channel is partitioned into
three contiguous OFDM sub-channel blocks. Two OFDM sub-channel
blocks each have a bandwidth of 20 MHz. The remaining OFDM
sub-channel block has a bandwidth of 40 MHz. The OFDM sub-channel
blocks include independent data streams for three client stations.
In FIG. 2D, the communication channel is partitioned into four
contiguous OFDM sub-channel blocks. Two OFDM sub-channel blocks
each have a bandwidth of 10 MHz, one OFDM sub-channel block has a
bandwidth of 20 MHz, and one sub-channel block has a bandwidth of
40 MHz. The OFDM sub-channel blocks include independent data
streams for three client stations.
[0029] Although in FIGS. 2A, 2B, 2C, and 2D the OFDM sub-channel
blocks are contiguous across the communication channel, in other
embodiments the OFDM sub-channel blocks are not contiguous across
the communication channel (i.e., there are one or more gaps between
the OFDM sub-channel blocks). In an embodiment, each gap is at
least as wide as one of the OFDM sub-channel blocks. In another
embodiment, at least one gap is less than the bandwidth of an OFDM
sub-channel block. In another embodiment, at least one gap is at
least as wide as 1 MHz. In an embodiment, different OFDM
sub-channel blocks are transmitted in different channels defined by
the IEEE 802.11a and/or 802.11n Standards. In one embodiment, the
AP includes a plurality of radios and different OFDM sub-channel
blocks are transmitted using different radios.
[0030] FIG. 3 is a diagram of an example OFDMA data unit 300,
according to an embodiment. The OFDMA data unit 300 includes a
plurality of OFDM data unit 302-1, 302-2 and 302-3. In an
embodiment, the AP 14 transmits the OFDM data units 302-1, 302-2,
302-3 to different client stations 25 via respective OFDM
sub-channels within the OFDMA data unit 300. In another embodiment,
different client stations 25 transmit respective OFDM data units
302-1, 302-2, 302-3 to the AP 14 in respective OFDM sub-channels
within the OFDMA data unit 300. In this embodiment, The AP 14
receives the OFDM data units 302-1, 302-2, 302-3 from the client
stations 25 via respective OFDM sub-channels of within the OFDMA
data unit 300, in this embodiment.
[0031] Each of the OFDM data units 302-1, 302-2, 302-3 conforms to
a communication protocol that supports OFDMA transmission, such as
the HEW communication protocol, in an embodiment. In an embodiment
in which the OFDMA data unit 300 corresponds to a downlink OFDMA
data unit, the OFDMA data unit 300 is generated by the AP 14 such
that each OFDM data unit 302 is transmitted to a respective client
station 25 via a respective sub-channel of the WLAN 10 allocated
for downlink transmission of the OFDMA data unit 300 to the client
station. Similarly, an embodiment in which the OFDMA data unit 300
corresponds to an uplink OFDMA data unit, the AP 14 receives the
OFDM data units 302 via respective sub-channels of the WLAN 10
allocated for uplink transmission of the OFDM data units 302 from
the client stations, in an embodiment. For example, the OFDM data
unit 302-1 is transmitted via a first 20 MHZ sub-channel of the
WLAN 10, the OFDM data unit 302-2 is transmitted via a second 20
MHz sub-channel of the WLAN 10, and the OFDM data unit 302-3 is
transmitted via a 40 MHz sub-channel of the WLAN 10, in the
illustrated embodiment.
[0032] In an embodiment, each of the OFDM data units 302 includes a
preamble including one or more legacy short training fields (L-STF)
304, one or more legacy long training fields (L-LTF) 306, one or
more legacy signal fields (L-SIG) 308, one or more first high
efficiency WLAN signal field (HEW-SIG-A) 310, N HEW long training
fields (HEW-LTF) and a second HEW signal field (HEW-SIGB) 314.
Additionally, each OFDM data unit 302 includes a high efficiency
WLAN data portion (HEW-DATA) 318. In an embodiment, each L-LSF
field 306, each L-LTF field 308, each L-SIG field 310 and each
HEW-SIGA field 312 occupies a smallest bandwidth supported by the
WLAN 10 (e.g., 20 MHz). In an embodiment, if an OFDM data unit 302
occupies a bandwidth that is greater than the smallest bandwidth of
the WLAN 10, then each L-LSF field 306, each L-LTF field 308, each
L-SIG field 310 and each HEW-SIGA field 312 is duplicated in each
smallest bandwidth portion of the OFDM data unit 302 (e.g., in each
20 MHz portion of the data unit 302). On the other hand, each
HEW-STF field 312, each HEW-LTF field 314, each HEW-SIGB field 316
and each HEW data portion 318 occupies an entire bandwidth of the
corresponding OFDM data unit 302, in an embodiment. For example,
the OFDM data unit 302-3 occupies 40 MHz, wherein L-LSF field 306,
the L-LTF field 308, L-SIG field 310 and HEW-SIGA fields 312 is
duplicated in the upper and the lower 20 MHz bands of the OFDM data
unit 302-3, while each of the HEW-STF field 312, each of the
HEW-LTF fields 314, each of the HEW-SIGB field 316 and each of the
HEW data portion 318 occupies the entire 40 MHz bandwidth of the
data unit 302, in the illustrated embodiment.
[0033] In an embodiment, padding is used in one or more of the OFDM
data units 302 to equalize lengths of the OFDM data units 302.
Accordingly, the length of each of the OFDM data units 302
correspond to the length of the OFDMA data unit 302, in this
embodiment. Ensuring that the OFDM data units 302 are of equal
lengths synchronizes transmission of acknowledgment frames by
client stations 25 that receive the data units 302, in an
embodiment. In an embodiment, each of one or more of the OFDM data
units 302 is an aggregate MAC service data units (A-MPDU), which is
in turn included in a PHY protocol data unit (PPDU). In an
embodiment, padding (e.g., zero-padding) within one or more of the
A-MPDUs 302 is used to equalize the lengths of the data units 302,
and to synchronize transmission of acknowledgement frames
corresponding to the OFDMA data unit 300.
[0034] In various embodiments, the AP 14 obtains, for each client
station 25 of a plurality of client stations 25, one or more
quality indicators corresponding to one or more sub-channel blocks
of the communication channel associated with the client station 25.
Examples of quality indicators that the AP 14 obtains include (i) a
respective channel response indicator corresponding to each of one
or more sub-channel blocks, (ii) a respective signal strength
indicator corresponding to each of one or more sub-channel blocks,
(ii) a respective signal to noise ratio (SNR) or signal to
interference plus noise ratio (SNIR) indicator corresponding to
each of one or more sub-channel blocks, (iv) an indicator
corresponding to a "best" sub-channel block, (v) a respective
indicator corresponding to order of preference of each of one or
more sub-channel blocks, etc., in various embodiments and/or
scenarios. Then, based on the one or more quality indicators
obtained for each client station 25 of the plurality of client
stations 25, the AP 14 selects groups of client stations 25 for
OFDMA communication with the client stations 25 and/or allocates
respective sub-channel blocks to respective client stations 25 in a
group of client stations 25 selected for OFDMA communication with
the client stations 25. The AP 14 then transmits at least one OFDMA
data unit to a group of client stations 25, wherein the OFDMA data
unit includes respective OFDM data units directed to the client
stations 25 of the group of client stations 25, in an embodiment.
The respective OFDM data units are transmitted to the client
stations 25 in respective sub-channel blocks allocated to the
client station 25, in an embodiment. Similarly, in an embodiment,
the AP 14 receives at least one OFDMA data unit from the group of
client stations 25, wherein the OFDMA data unit includes respective
OFDM data units transmitted by the client stations 25 in respective
sub-channel blocks allocated to the client station 25, in an
embodiment. To this end, the AP 14 provides, in some manner, to a
group of client stations 25 indications of the respective
sub-channel blocks allocated to the client stations 25, in an
embodiment.
[0035] In an embodiment, the AP 14 obtains the one or more quality
indicators corresponding to one or more sub-channel blocks of a
communication channel associated with a client station 25 based on
sounding of the communication channel associated with the client
station 25. For example, in an embodiment, the AP 14 explicitly
sounds a communication channel associated a client station 25 by
transmitting one or more training signals to the client stations 25
and, in response, receiving feedback from the client station 25.
The feedback includes the one or more quality indicators
corresponding to one or more sub-channel blocks of the
communication channel, or includes indications of channel
characteristics that allow the AP 14 to determine the one or more
quality indicators, in various embodiments. In some embodiments,
the AP 14 obtains the one or more quality indicators corresponding
to one or more sub-channel blocks of a communication channel
associated with a client station 25 based on implicit sounding of
the communication channel. In such embodiments, the AP 14 obtains
channel characteristics of a reverse channel from a client station
25 to the AP 14 based on training signal transmitted by the client
station 25 to the AP 14. The AP 14 then determines characteristics
of the forward channel based on the characteristics of the reverse
channel by assuming channel reciprocity, and obtains the one or
more quality indicators corresponding to one or more sub-channel
blocks based on the characteristics of the forward channel, in some
embodiments. To ensure channel reciprocity, the AP 14 conducts a
suitable calibration procedure to calibrate the receive and
transmit radio frequency (RF) chains of the AP 14, in some
embodiments. In some embodiments, the AP 14 obtains the one or more
quality indicators corresponding to one or more sub-channel blocks
directly based on characteristics of the reverse channel, without
obtaining characteristics of the forward channel. For example, in
an embodiment, the AP 14 obtains signal strength, signal to noise
ratio, etc. associated with the one or more sub-channel blocks
directly based on the training signals received from the client
station 25 in the reverse communication channel.
[0036] FIG. 4A is a timing diagram of an example sounding procedure
400 and transmission of an example OFDMA data unit formed according
to grouping and/or channel allocation determined based on the
sounding procedure 400, according to an embodiment. The sounding
procedure 400 is an explicit sounding procedure in which the AP 14
transmits a sounding packet to each of a plurality of client
stations 25 and receives, from each of the plurality client
stations 25, feedback containing channel state information and/or
other indications corresponding to a forward communication channel
from the AP 14 to the client station 25.
[0037] During a time interval 402, the AP 14 transmits an
announcement frame 404 to a plurality of client stations 25 to
initiate the sounding procedure 400 with the client client stations
25. The announcement frame 404 identifies client stations 25 that
are the intended participants in the sounding procedure 400, in an
embodiment. The announcement frame 404 is a null data packet (NDP)
that omits a payload, in an embodiment. In another embodiment, the
announcement frame 404 includes a payload. In an embodiment, the
announcement frame 404 identifies client stations 25 as intended
participants in the sounding procedure 400 by including a suitable
identifier, such as at least a portion of an association identifier
(AID), corresponding to each of the client stations 25 identified
as an intended participant. In an embodiment, the announcement
frame 402 also indicates a length or a duration corresponding to
the sounding procedure 400, for example to protect the sounding
procedure 400 from transmissions by communication devices that are
not intended participants in the sounding procedure 400. In an
embodiment, each client station 25 identified by announcement frame
404 determines, based on detecting its own AID in the announcement
frame 404, that the client station 25 is an intended participant in
the sounding procedure 400. In the event that the management frame
404 does not include the AID of a particular client station 25,
that client station 25 determines that it is not an intended
participant in the sounding procedure 400 and refrains from
accessing the channel for the duration indicated by the
announcement frame 404, in an embodiment.
[0038] During a time interval 406, the AP 14 transmits a sounding
frame 408 that includes one or more training signals that allow
each client station 25 to obtain a measure of the forward
communication channel from the AP 14 to the client station 25. In
an embodiment, the sounding frame 404 is a null data packet that
includes the one or more training signals in a PHY preamble of the
data unit, and omits a payload. In another embodiment, the sounding
frame 404 includes a PHY preamble and a payload portion. In an
embodiment, each of the client station 25 identified by the
announcement frame 408 obtains, based on training information
included in the sounding frame 408, a channel description
characterizing the communication channel between the AP 14 and the
client station 25 and/or quality of one or more of the sub-channel
blocks of the communication channel between the AP 14 and the
client station 25. For example, each client station 25 obtains
channel state information (e.g., the gain, the phase, the signal to
noise ratio (SNR), etc.) characterizing the communication channel
between the AP 14 and the client station 25 over the entire
bandwidth of the communication channel, in an embodiment.
Additionally or alternatively, in an embodiment, each client
station 25 determines channel quality indicators (e.g., SNR, SNIR,
signal strength, etc.) corresponding to each sub-channel block of
the communication channel between the AP 14 and the client station
25. In some embodiments, each client station 25 identifies one or
more preferred sub-channel blocks for the client station 25, and
determines an order of preference of the identified preferred
sub-channel blocks.
[0039] During a time intervals 410, the client stations 25 transmit
respective feedback packets 414 to the AP 14. In an embodiment, a
feedback packet 414 from a particular client station 25 includes
one or more of (i) indications of one or more preferred sub-channel
blocks identified by the particular station 25, (ii) indications of
order of preference of multiple preferred sub-channel blocks
identified by the particular station 25 (iii) one or more channel
quality indicators, such as channel state information (CSI) or
other suitable channel characteristics, corresponding to each of
one or more sub-channel blocks of the communication channel between
the AP 14 and the particular client station 25, (iv) CSI or other
suitable channel description corresponding to the entire bandwidth
of the communication channel between the AP 14 and the particular
client station 25, such as CSI corresponding to each sub-carrier or
CSI corresponding to each group of sub-carriers of the
communication channel between the AP 14 and the particular client
station 25 (v) SNR corresponding to the entire bandwidth of the
communication channel between the AP 14 and the particular client
station 25, etc.
[0040] In an embodiment, a client station 25 (e.g., the client
stations 25-1) identified first in the announcement frame 402
transits its feedback packet 412-1 during a time interval that
begins upon expiration of a certain predetermined time interval,
such as a time interval corresponding to SIFS or another suitable
predetermined time interval, after completion of reception of the
sounding packet 404 by the client station 25. The AP 14 receives
the feedback packet 412-1 from the first client station 25 and
successively polls for feedback from each of the remaining client
stations 25 identified by the announcement frame 404 as
participants in the sounding procedure 400, in an embodiment. For
example, the AP successively transmits respective immediate
response request (IRR) frames 414 to each of the remaining client
stations 25 identified by the announcement frame 404 as
participants in the sounding procedure 400, in an embodiment. Each
of the remaining client stations 25 transmits its feedback packet
412 during a time interval that begins upon expiration of a certain
predetermined time interval, such as a time interval corresponding
to SIFS or another suitable time interval, after completion of
reception by the client station 25 the IRR frame 414 directed to
the client station 25, in an embodiment.
[0041] Based on the feedback packets 412 received by the AP 14
during the time interval 410, the AP 14 obtains one or more quality
indicators corresponding to one or more sub-channel blocks of the
communication channel between the AP 14 and each of the client
stations 25 that participated in the sounding procedure 400, in an
embodiment. For example, the AP 14 obtains the one more quality
indicators for a particular client station 25 directly from the
feedback packet 414 received from the particular client station 25,
in an embodiment. In another embodiment, the AP 14 determines the
one or more quality indicators for a particular client station 25
based on data included in the feedback packet 412 received from the
client station 25, such as based on CSI or other channel
description included in the feedback packet 412 received from the
client station 25. During a time interval 416, based on the quality
indicators obtained for at least some of the client stations 25,
the AP 14 selects one or more groups of client stations 25 for
OFDMA communication with the client statins 25 and/or allocates
respective sub-channel blocks to client stations 25 selected as
members of a group of client stations 25 for OFDMA communication
with the client statins 25, in an embodiment. During a time
interval 418, the AP 14 transmits an OFDMA data unit 420 to a group
of client stations 25 selected as members of a group of client
stations 25 for OFDMA communication with the client statins 25, in
an embodiment. The OFDMA data unit 420 includes respective OFDM
data units directed to the client stations 25 of the group, wherein
the respective OFDM data units are transmitted to the client
statins 25 in the respective sub-channel blocks allocated to the
client stations 25, in an embodiment.
[0042] With continues reference to FIG. 4A, in some embodiments,
sounding procedure 400 is used for the purpose of beamforming as
well as OFDMA communication. For example, in addition to generating
feedback related to quality of sub-channel blocks for OFDMA
communication, each client station 25 develops, based on the
training signals in the sounding packet 408, beamforming feedback,
and provides the beamforming feedback to the AP 14. For example,
each feedback packet 412 includes beamforming feedback in addition
to the feedback related to OFDMA communication, in an embodiment.
FIG. 4B is a diagram of a feedback packet 450 that a client station
25 is configured to transmit to the AP 14 during the sounding
procedure 400 of FIG. 4A, according to one such embodiment. In an
embodiment, the feedback packet 450 corresponds to each of the
feedback packets 412 of FIG. 4A. In an embodiment, the feedback
packet 450 is generated by a client station 25 in response to
receiving a sounding packet transmitted by the AP 14 to the client
station 25. For example, the PHY processing unit 29 of the client
station 25-1 is configured to generate feedback packets such as the
feedback packet 450, in an embodiment.
[0043] The feedback packet 450 includes a MIMO control field 452, a
beamforming feedback portion 454 and an OFDMA feedback portion 456.
The beamforming feedback portion 452 includes an average SNR
subfield 458, a beamforming feedback sub-field 460 and a per-tone
SNR sub-field 462. The beamforming feedback sub-field 460 includes
some form of beamforming feedback generated at the client station
25 based on a sounding packet transmitted by the AP 14 to the
client station 25, in various embodiments. For example, in an
embodiment, the beamforming feedback sub-field 460 includes
compressed steering feedback. For example, the beamforming feedback
sub-field 460 includes compressed steering feedback for multi-user
(MU) multiple input multiple output (MIMO) as defined in the IEEE
802,11 ac standard. In another embodiment, the beamforming feedback
sub-field 460 includes another suitable form of beamforming
feedback, such as channel estimate feedback or uncompressed
steering matrix feedback, for example. In an embodiment, each of
the average SNR subfield 458, the beamforming feedback sub-field
460 and the per-tone SNR sub-field 462 includes feedback that
covers the entire bandwidth of the communication channel. In an
embodiment, each of the average SNR subfield 458, the beamforming
feedback sub-field 460 and the per-tone SNR sub-field 462 includes
feedback that covers the bandwidth of the sounding packet based on
which the beamforming feedback was generated by the client station
25.
[0044] The OFDMA feedback portion 456 includes OFDMA feedback as
described above with respect to FIG. 4A, in an embodiment. For
example, the OFDMA portion 456 includes one or more of (i)
indications of one or more preferred sub-channel blocks identified
by the client station 25 based on the sounding frame transmitted by
the AP 14 to the client station 25, (ii) indications of order of
preference of multiple preferred sub-channel blocks identified by
the particular station 25 based on the sounding frame based on the
sounding frame transmitted by the AP 14 to the client station 25
(iii) one or more channel quality indicators, such as CSI or other
suitable channel quality indicators, corresponding to each of one
or more sub-channel blocks of the communication channel between the
AP 14 and the client station 25, (iv) CSI corresponding to the
entire bandwidth of the communication channel between the AP 14 and
the client station 25, such as CSI corresponding to each
sub-carrier or CSI corresponding to each group of sub-carriers of
the communication channel between the AP 14 and the client station
25, and (v) SNR corresponding to the entire bandwidth of the
communication channel between the AP 14 and the particular client
station 25.
[0045] In an embodiment, the feedback packet 450 omits one or more
of the average SNR subfield 458, the beamforming feedback sub-field
460 and the per-tone SNR sub-field 460. In an embodiment, the
feedback packet 450 omits the entire beamforming feedback portion
452. For example, the feedback packet 450 omits the entire
beamforming feedback portion 452 in an embodiment in which the AP
14 includes a single transmit antenna and/or if the AP 14 is not
configured to perform beamforming or is not configured to perform
multi-user beamforming.
[0046] In some embodiments, at least a portion of OFDMA feedback is
included in the MIMO control field 452 of the feedback packet 540.
For example, indications of one or more preferred sub-channel
blocks are included in the MIMO control field 452. In some such
embodiments, the feedback packet 450 omits the OFDMA feedback
portion 454.
[0047] FIG. 4C is a diagram of a feedback packet 470 that a client
station 25 is configured to transmit to the AP 14 during the
sounding procedure 400 of FIG. 4A, according to another embodiment.
In an embodiment, the feedback packet 470 corresponds to a feedback
packet 412 of FIG. 4A. The feedback packet 470 is generally the
same as the feedback packet 450, except that a beamforming portion
470 includes a beamforming feedback portion 474 that covers a
bandwidth that corresponds to the one or more sub-channel blocks
indicated by the OFDMA feedback portion 456.
[0048] FIG. 5 is a timing diagram of an example sounding procedure
500 and transmission of an example OFDMA data unit formed according
to grouping and/or channel allocation determined based the sounding
procedure 500, according to an embodiment. The sounding procedure
500 is an implicit sounding procedure in which the AP 14 requests
transmission of one or more training signals from each client
station 25 of a plurality of client stations 25. The AP 14 receives
the requested one or more training signals from each of the
plurality of client stations 25, and obtains, for each of the
client stations 25, one or more quality indicators corresponding to
one or more sub-channel blocks of the communication channel
associated with the client station 25,in an embodiment.
[0049] Referring to FIG. 5, during a time interval 502, the AP 14
sequentially transmits respective control frames 504 to each of a
plurality of client stations 25. Each control frame 504 is directed
to a particular client station 25 and includes a request for
transmission of one or more training signals by the client station
25. In response to receiving the respective control frames 504, the
client stations 25 transmit respective sounding frames 506 to the
AP 14. Each sounding frame 506 includes one or more training
signals, in an embodiment. For example, each sounding frame 504
includes one or more training fields in a preamble portion of the
sounding frame 504. In an embodiment, each sounding frame 504 is an
NDP that omits a payload. In another embodiment, each sounding
frame 504 includes a payload. Each client station 25 transmits its
sounding frame 506 upon expiration of a certain predetermined time
period, such as a time period corresponding to SIFS or another
predetermined time period, after completion of reception of the
corresponding control frame 504 by the client station 25, in an
embodiment.
[0050] The AP 14 receives a sounding frame 504 from a client
station 25 and obtains, based on the sounding frame 504, one or
more quality indicators corresponding to one or more sub-channel
blocks of the communication channel between the AP and the client
station 25. For example, the AP 14 obtains, based on the sounding
packet 504, an estimate of the reverse communication channel from
the client station 25 to the AP 14, in an embodiment. The estimate
of the reverse channel can be represented, for example, in a matrix
format as a two-dimensional channel matrix H that specifies, in
each element, a channel gain parameter for a spatial stream defined
by a transmit antenna of the client station 25 and a receive
antenna of the AP 14. In an embodiment, the AP 14 determines an
estimate of the forward communication channel from the AP 14 to the
client station 25 based on the reverse communication channel from
the client station by assuming channel reciprocity. For example,
the AP 14 obtains an estimate of the forward channel by transposing
the channel matrix H obtained for the reverse channel. The AP 14
then obtains respective quality indicators corresponding to one or
more sub-channel blocks of the commination channel based on the
forward channel estimate corresponding to the channel. In an
embodiment the AP 14 obtains a reverse and forward channel estimate
corresponding to each OFDM tone of the communication channel or a
subset of OFDM tones, such as each second OFDM tone, each 4.sup.th
OFDM tone, or any other suitable subset of OFDM tones of the
communication channel. The AP 14 then obtains the quality
indicators corresponding to each sub-channel blocks of the
communication channel based on channel estimates corresponding to
OFDM tones included in the sub-channel block, in an embodiment.
[0051] In another embodiment, the AP 14 obtains, from training data
included in the sounding packet 504, a measure indicative of
quality of the reverse communication channel, such a measure of
signal strength, signal to noise ratio, etc. associated with the
communication channel. In an embodiment, the AP 14 obtains such
measure for each sub-carrier or each group of sub-carriers of the
communication channel, and obtains the channel quality indicators
corresponding to one or more sub-channel blocks based on the
measure of the reverse communication channel. In an embodiment, the
AP 14 selects one or more "best" or "preferred" sub-channel blocks
for each of the stations 25. In an embodiment, the AP 14 ranks one
or more sub-channel blocks in order of preference for each of the
client stations 25. Examples of quality indicators that the AP 14
obtains for one or more sub-channel blocks include one or more of
(i) a respective channel response indicator corresponding to each
of one or more sub-channel blocks, (ii) a respective signal
strength indicator corresponding to each of one or more channel
blocks, (ii) a respective SNR or SNIR indicator corresponding to
each of one or more sub-channel blocks, (iv) an indicator
corresponding to a "best" sub-channel block, (v) a respective
indicator corresponding to order of preference of each of one or
more sub-channel blocks.
[0052] During a time interval 508, based on the quality indicators
obtained based on the sounding procedure 500, the AP 14 selects one
or more groups of client stations 25 for OFDMA communication with
the client statins 25 and/or allocates respective sub-channel
blocks to client stations 25 selected as members of a group of
client stations 25 for OFDMA communication with the client statins
25. During a time interval 510, the AP 14 transmits an OFDMA data
unit 512 to a group of client stations 25 selected as members of a
group of client stations 25 for OFDMA communication with the client
statins 25. The OFDMA data unit 512 includes respective OFDM data
units directed to the client stations 25 of the group, wherein the
respective OFDM data units are transmitted to the client statins 25
in the respective sub-channel blocks allocated to the client
stations 25, in an embodiment.
[0053] In some embodiments, the implicit sounding procedure 500 is
conducted by the AP 14 for the purpose of beamforming as well as
for OFDMA group selection and/or sub-channel block allocation. For
example, the AP 14 is configured to determine a transmit
beamsteering matrix for use in transmitting to one or more client
stations 25 based on the sounding packets 506 received from the one
or more client stations 25, in an embodiment.
[0054] FIG. 6 is a timing diagram of an example sounding procedure
600 and transmission of an example OFDMA data unit formed according
to grouping and/or channel allocation determined based the sounding
procedure 600, according to an embodiment. The sounding procedure
600 is a transparent implicit sounding procedure in which the AP 14
obtains one or more quality indicators corresponding to one or more
sub-channel blocks of a communication channel associated with a
client station 25 based on one or more "regular" data units
received from the client station 25.
[0055] In an embodiment, during a time interval 602, the AP 14
receives a plurality of regular data units 604 from a plurality of
client stations 25. Each regular data unit 604 includes one or more
training signals (e.g. in a preamble portion of the regular data
unit) that allow the AP 14 at least practically characterize the
reverse channel from a corresponding client station 25 to the AP
14.
[0056] As used herein, a regular data unit is a non-sounding data
unit used in any procedure other than channel sounding, e.g., data
exchange, modulation and coding scheme (MCS) feedback, etc. In an
embodiment, each regular data unit 604 is a communication frame, a
data packet, etc. In an embodiment, the regular data units 604 are
generally not sounding physical layer convergence procedure (PLCP)
protocol data unit (PPDU) or null data packets (NDP) used
specifically for sounding. In some embodiments, the regular data
units 604 do not include respective indications that the data units
604 are for sounding a communication channel (while data units used
for sounding communication channels include such an indication).
Further, in some embodiments, the regular data units 604 include
explicit respective indications that the data units 604 are not for
sounding the communication channel. Still further, in some
embodiments, the regular data units 604 are not transmitted in
response to a request to transmit a sounding packet. A client
stations 25 transmits a regular data unit 604 for a purpose
unrelated to sounding the communication channel. For example, in an
embodiment, a regular data unit 604 is a data packet that includes
a data payload. The implicit channel sounding procedure is
therefore transparent to the client stations 25.
[0057] In some embodiments, a client station 25 transmits a data
unit 604 using multiple spatial streams, and the data unit 604
accordingly includes information (e.g., training fields in the
physical layer (PHY) preamble) that can be used to obtain channel
characteristics of the reverse channel from the client station 25
to the AP 14. For example, the data unit 604 can include a payload
transmitted over three spatial streams and, accordingly, three
training fields in the PHY preamble to enable the AP 14 to properly
process the payload.
[0058] In an embodiment, the AP 14 obtains, based on training
information included in the regular data unit 604, channel state
information (CSI) that describes one or more characteristics of
each spatial stream associated with the reverse channel (e.g.,
gain, phase, SNR, etc.). The CSI can be represented, for example,
in a matrix format as a two-dimensional channel matrix H that
specifies, in each element, a channel gain parameter for a spatial
stream defined by the corresponding transmit antenna and a receive
antenna. To generate an estimate of the forward channel, in an
embodiment, the AP 14 calculates the transpose of the matrix that
describes the reverse channel. In doing so, the AP 14 assumes that
the MIMO channel between the AP 14 and the client station 25 is
symmetrical so that the forward channel and the reverse channel can
be considered to be reciprocal.
[0059] In some embodiments, a regular data unit 604 received from a
client station 25 in some cases includes fewer training fields than
spatial dimensions associated with the communication channel
associated with the client station 25. In an embodiment, the AP 14
obtains a measure partially characterizing the communication
channel, and obtains the one or more quality indicators
corresponding to one or more sub-channel blocks of the
communication channel based on the measure partially characterizing
the communication channel. In some embodiment, the AP 14 does not
use every regular data unit received from a client station 25 to
obtain characteristics of the communication channel between the AP
14 and the client station 24. For example, the AP 14 selects
regular data units based on which to obtain characteristics of the
communication channel according to one or more suitable selection
criteria. For example, the AP 14 selects regular data units
transmitted by a client station 25 using all spatial dimensions
associated with the communication channel between the AP 14 and the
client station 25, in an embodiment.
[0060] In an embodiment the AP 14 obtains, based on one or more
data units 604, characteristics of a communication channel
corresponding to each OFDM tone of the communication channel or a
subset of OFDM tones, such as each second OFDM tone, each 4.sup.th
OFDM tone, or any other suitable subset of OFDM tones of the
communication channel. The AP 14 then obtains the quality
indicators corresponding to each sub-channel blocks of the
communication channel based on channel estimates corresponding to
OFDM tones included in the sub-channel block, in an embodiment.
[0061] During a time interval 606, based on the quality indicators
obtained based on the sounding procedure 600, the AP 14 selects one
or more groups of client stations 25 for OFDMA communication with
the client statins 25 and/or allocates respective sub-channel
blocks to client stations 25 selected as members of a group of
client stations 25 for OFDMA communication with the client statins
25. During a time interval 608, the AP 14 transmits an OFDMA data
unit 610 to a group of client stations 25. The OFDMA data unit 610
includes respective OFDM data units directed to the client stations
25 of the group, wherein the respective OFDM data units are
transmitted to the client statins 25 in the respective sub-channel
blocks allocated to the client stations 25, in an embodiment.
[0062] In some embodiments, the transparent implicit sounding
procedure 600 is conducted by the AP 14 for the purpose of
beamforming as well as for OFDMA group selection and/or sub-channel
block allocation. For example, the AP 14 is configured to determine
a transmit beamsteering matrix for use in transmitting to one or
more client stations 25 based on training data included on the data
units 604 received from the client stations 25, in an
embodiment.
[0063] In various embodiments, prior to transmitting an OFDMA data
unit to a group of client stations 25, the AP 14 informs, or
notifies, the client stations 25 that the client stations 25 are
members of a group of client stations 25 for OFDMA communication
with the client stations 25. FIG. 7 is a timing diagram
illustrating a notification procedure 700 used by the AP 14 to
inform a plurality of client stations 25 that the client stations
25 are members of a group of client stations 25 for OFDMA
communication, according to an embodiment. The AP 14 transmits a
group management frame 702 to a plurality of client stations 25.
The group management frame 702 informs the plurality of client
statins 25 that the client stations 25 are members of a group for
OFDMA communication with the client stations 25. In an embodiment,
the group management frame 702 includes a group number field and a
plurality of station identification fields. Each station
identification field includes an identifier, such as, for example,
an association identifier (AID) or a partial AID, associated with a
particular client station 25. Each client station 25 that receives
the group management frame determines whether that client station
25 is a member of the group identified by the group number
indicated in the group management frame 702, in an embodiment. For
example, a client station 25 that receives the group management
frame 704 determines that the client station 25 is a member of the
group indicated by the management frame 702 by detecting its own
AID or partial AID in one of the station identification field
included in the management frame 702. In an embodiment, the client
station 25 further determines its position within the group based
on placement of its AID relative to placement of the other AIDS
within the management frame 702.
[0064] During a time interval 704, the client stations 25
identified by the group management group 702 transmit respective
acknowledgement frame 706 to the AP 14. In an embodiment, the
client station 25 identified first in the group management frame
702 transits its acknowledgement frame 706-1 during a time interval
that begins upon expiration of a certain predetermined time
interval, such as a time interval corresponding to SIFS or another
suitable predetermined time interval, after completion of reception
of the group management frame 704 by the client station 25. The AP
14 receives the acknowledgement frame 706-1 from the first client
station 25 and successively polls for acknowledgement frames from
each of the remaining client stations 25 identified by the group
management frame 704, in an embodiment. For example, the AP 14
successively transmits respective poll frames 708 to each of the
remaining client stations 25 of the group of client stations 25.
Each of the remaining client stations 25 transmits its
acknowledgement frame 706 during a time interval that begins upon
expiration of a certain predetermined time interval, such as a time
interval corresponding to SIFS or another suitable time interval,
after completion of reception by the client station 25 of the poll
frame 708 directed to the client station 25, in an embodiment.
After receiving the respective acknowledgement frames 708 from the
client stations 25, the AP 14 transmits one or more OFDMA data
units to the group of client stations 25, in an embodiment. To
indicate to the client stations that an OFDMA data unit is directed
to the group of client stations, the AP 14 includes, in the OFDMA
data, the group ID provided to the client stations 25 by the group
management frame 802, in an embodiment.
[0065] FIG. 8 is a timing diagram illustrating a notification
procedure 800 used by the AP 14 to inform a plurality of client
stations 25 that the client stations 25 are members of a group of
client stations for OFDMA communication, according to another
embodiment. The procedure 800 is similar to the procedure 700 of
FIG. 7, except that in the notification procedure 800, the AP 14
transits a respective group announcement frame 802 to each client
station 25 included in the group. In an embodiment, each management
frame 802 is substantially the same as the group management frame
702 of FIG. 7. In an embodiment, a client station 25 that receives
the group management frame 802 directed to the group of client
stations 25 determines that the client station 25 belongs to the
group of client stations 25 based on its own AID in the group
management frame 802. In an embodiment, the client station 25
further determines its position within the group based on placement
of its AID relative to placement of the other AIDs within the
management frame 802. After receiving management frame 802 directed
to a client station 25, the client station 25 transmits an
acknowledgement frame 804 to the AP 14. In an embodiment, each
client station 25 transmits an acknowledgment frame 804 during a
time interval that begins upon expiration of a certain
predetermined time interval, such as a time interval corresponding
to SIFS or another suitable time interval, after completion of
reception by the client station 25 of the group management frame
802 directed to the client station 25, in an embodiment. After
receiving the respective acknowledgement frames 804 from the client
stations 25, the AP 14 transmits one or more OFDMA data units to
the group of client stations 25, in an embodiment.
[0066] In various embodiments, the AP 14 employs static allocation,
semi-static allocation or dynamic allocation to allocate respective
sub-channel blocks to client stations 25 in a group for OFDMA
communication with the client station 25. In an embodiment in which
the AP 14 employs static allocation, the AP 14 allocates respective
sub-channel blocks to client stations 25 in a group of client
stations 25 for OFDMA communication with the client station 25 when
the AP 14 forms the group, of client stations 25, and the
sub-channel block allocation to the client stations 25 persists for
the life of the group. In an embodiment, the AP 14 indicates to the
client stations 25 that belong to a group using a group management
frame that notifies the client stations 25 of their membership in
the group. For example, the group management frame 702 of FIG. 7
identifies a group of client stations 25, and also includes
indications of respective sub-channel blocks allocated to each of
the identified client stations 25. Similarly, each group management
frame 802 of FIG. 8 includes indications of respective sub-channel
blocks allocated to each of the identified client stations 25
identified by the group management frame 802, in an embodiment.
[0067] In an embodiment in which the AP 14 employs semi-static
sub-channel block allocation, allocation of the sub-channel blocks
to client stations 25 in a group can change during the life of the
group. For example, the AP 14 periodically obtains, for each of the
client stations 25 in a group, one or more quality indicators
corresponding to one or more sub-channel blocks of the channel
associated with the client stations 25 in the group, and determines
a suitable sub-channel block allocation to the client stations of
the group each time new quality indicators are obtained for the
client stations 25 in the group. For example, the AP 14 utilizes
the sounding procedure 400 of FIG. 4A, the sounding procedure 500
of FIG. 5, the sounding procedure 500 of FIG. 6, or another
suitable channel sounding procedure to periodically obtain quality
indicators corresponding to one or more sub-channel blocks of the
channel associated with the client stations 25 in the group, and
performs sub-channel block allocation based on quality indicators
obtained based on the sounding procedure. In an embodiment, the AP
transmits one or more group management frames to the client
stations 25 in a group to inform the client stations 25 of new
sub-channel blocks allocated to the client stations 25 each time
the AP 14 completes a sounding procedure and allocates sub-channel
blocks allocated to the client stations 25 based on the sounding
procedure.
[0068] In an embodiment in which the AP 14 employs dynamic
sub-channel block allocation, the AP 14 allocates sub-channel
blocks to client station 25 in a group on packet-per-packet basis,
for example prior to transmission of each OFDMA data unit to the
client stations of the group. In an embodiment in which the AP 14
employs dynamic sub-channel block allocation the AP 14 indicates to
the client statins 25 in a group the sub-channel blocks allocated
to the client stations 25 for a particular OFDMA transmission to
the client stations 25 by including the indications in a preamble
of the OFDMA transmission. For example, in an embodiment, the
sub-channel block allocation indications are included in a signal
field of the OFDMA transmission. With reference to FIG. 3, the
sub-channel block allocation indications are included in the
HEW-SIGA fields 310, in an example embodiment. In an embodiment,
the signal field of the OFDMA transmission includes a group number
subfield that identifies a group of client stations 25, and
respective sub-channel allocation subfields corresponding to the
client stations 25 of the identified group. In an embodiment, the
sub-channel allocation subfields in the signal field are provided
in the order corresponding to client station position within the
group, wherein the client station position corresponds to the
client station position determined by each client station 25 based
on a group management frame previously received by the client
station 25. When receiving an OFDMA transmission directed to a
group of client stations 25, each client station 25 that is a
member of the group determines, based on the sub-channel allocation
subfield corresponding to the client station 25 in the signal field
of the OFDMA transmission, which sub-channel block within the OFDM
transmission is allocated to the client station 25, in an
embodiment.
[0069] In some embodiments, client stations 25, rather than AP 14,
conduct channel sounding to obtain one or more quality indicators
corresponding to one or more sub-channel blocks of the
communication channel associated with the client stations 25, and
provide indications of one or more preferred sub-channel blocks to
the AP 14. In an embodiment, the client stations 25 conduct
explicit channel sounding similar to the sounding procedure 400
described above with respect to FIG. 4A, and obtain characteristics
of the communication channels between the AP 14 and the client
stations 25 based on explicitly sounding the communication
channels. For example, a client station 25 initiates a sounding
procedure with AP 14 by transmitting a sounding packet the same as
or similar to the sounding packet 408 to the AP 14. The AP 14
provides feedback to the client station 25, such as via a feedback
packet the same as or similar to one of the feedback packets 412.
The client station 25 obtains one or more quality indicators
corresponding to one or more sub-channel blocks of the
communication channel based on the feedback received from the AP
14, and identifies one or more sub-channel blocks preferred by the
client station 25 to be used for OFDMA communication with client
station 25. In an embodiment, the client station 25 identifies
multiple sub-channel blocks preferred by the client station 25 to
be used for OFDMA communication with the client station 25, and
ranks the multiple sub-channel blocks in order of preference. The
client station 25 then provides indications of the one or more
preferred sub-channel blocks, and, if determined, indications of
the order of preference of the sub-channel blocks, to the AP
14.
[0070] In another embodiment, a client station 25 conducts an
implicit channel sounding procedure with the AP 14, similar to the
sounding procedure 500 described above with respect to FIG. 5, and
obtains quality indications corresponding to one or more
sub-channel blocks of the communication channel based on the
implicit sounding procedure. For example, the client station 25
transmits a request to the AP 14 requesting training signals to be
transmitted by the AP 14. In response to the request, the AP 14
transmits a sounding packet to the client station 25. The client
station 25 obtains characteristics of the communication channel
based on the received sounding frame, selects one or more preferred
sub-channel blocks, and, in some embodiments, ranks selected
multiple sub-channel blocks in order of preference. The client
station 25 then provides indications of the one or more selected
sub-channel blocks and, if determined, rankings corresponding to
order of preference of the one or more sub-channel blocks to the AP
14. Similarly, in an embodiment, a client station 25 conducts a
transparent implicit sounding procedure, similar to the transparent
implicit sounding procedure 600 described above with respect to
FIG. 6. For example, the client station 25 obtains characteristics
of the channel between the client station 25 and the AP 14 based on
one or more regular data units received from the AP 14, selects one
or more preferred sub-channel blocks based on the transparent
implicit sounding procedure, and provides indications of the one or
more preferred sub-channel blocks, and, in some embodiments,
indications of the order of preference of the sub-channel blocks,
to the AP 14.
[0071] The AP 14 obtains respective indications of preferred
sub-channel blocks and/or indications of order of preference of the
sub-channel blocks, from each of a plurality of client stations 25.
Based on the respective indications obtained from the plurality of
client stations 25, the AP 14 selects a group of client stations 25
for OFDMA communication and/or allocates respective sub-channel
blocks to respective client stations 25 that are members of a group
for OFDMA communication, in various embodiments.
[0072] FIG. 9 is a flow diagram of an example method 900 for
simultaneously communicating with multiple communication devices in
a WLAN, according to an embodiment. In an embodiment, the method
900 is implemented by an AP in the WLAN, according to an
embodiment. With reference to FIG. 1, the method 900 is implemented
by the AP 14. For example, the method 900 is implemented by the MAC
processing unit 18 and/or by the PHY processing unit 20 of the AP
14, in an embodiment. In other embodiments, the method 900 is
implemented by other components of the AP 14, or is implemented by
a suitable communication device other than the AP 14.
[0073] At block 902, one or more quality indicators are obtained
for each client station of a plurality of client stations. The one
or more quality indicators obtained for a client station correspond
to respective one more such channel blocks of an OFDM communication
channel associated with the client station. At block 904, a group
of client stations for OFDMA communication is selected based on the
quality indicators obtained for at least some of the client
stations at block 902. At block 906 an OFDMA data unit is
transmitted to the group of client stations selected at block 902.
Each of the OFDMA data units includes respective OFDM data units
transmitted to the client stations of the group. The respective
OFDM data units are transmitted to the communication devices in
respective sub-channel blocks allocated to the communication
devices.
[0074] FIG. 10 is a flow diagram of an example method 100 for
simultaneously communicating with multiple communication devices in
a WLAN, according to an embodiment. In an embodiment, the method
1000 is implemented by an AP in the WLAN, according to an
embodiment. With reference to FIG. 1, the method 900 is implemented
by the AP 14. For example, the method 1000 is implemented by the
MAC processing unit 18 and/or by the PHY processing unit 20 of the
AP 14, in an embodiment. In other embodiments, the method 1000 is
implemented by other components of the AP 14, or is implemented by
a suitable communication device other than the AP 14.
[0075] At block 1002, one or more quality indicators are obtained
for each client station in a group of client stations for OFDMA
communication. The one or more quality indicators obtained for a
client station correspond to respective one more such channel
blocks of an OFDM communication channel associated with the client
station. At block 1004, respective sub-channel blocks are allocated
to the two or more client stations of the group. The respective
sub-channel blocks are allocated based on the quality indicators
obtained at block 1002 for at least some of the two or more client
stations of the group. At block 1006, an OFDMA data unit is
transmitted to the group of client stations. Each of the OFDMA data
units includes respective OFDM data units transmitted to the client
stations of the group. The respective OFDM data units are
transmitted to the client stations in respective sub-channel blocks
allocated to the client stations at block 1004.
[0076] In an embodiment, a method for simultaneously communicating
with multiple communication devices in a communication network
includes obtaining, at a first communication device for each second
communication device of a plurality of second communication
devices, one or more quality indicators corresponding to one or
more sub-channel blocks of an orthogonal frequency division
multiplexing (OFDM) communication channel associated with the
second communication device. The method also includes selecting, at
the first communication device based on the quality indicators
obtained for each of at least some of the second communication
devices, a group of second communication devices for orthogonal
frequency division multiple access (OFDMA) communication, wherein
the group includes two or more second communication devices of the
plurality of second communication devices. The method additionally
includes transmitting, from the first communication device to the
group of second communication devices, at least one OFDMA data unit
that includes respective OFDM data units directed to the two or
more second communication devices of the group, wherein the
respective OFDM data units are transmitted in respective
sub-channel blocks allocated to the two or more second
communication devices of the group.
[0077] In other embodiments, the method includes any suitable
combination of one or more of the following features.
[0078] Obtaining, at the first communication device for each second
communication device of the plurality of second communication
devices, one or more quality indicators corresponding to one or
more sub-channel blocks of OFDM communication channel associated
with the second communication device comprises transmitting a
sounding packet from the first communication device to the
plurality of second communication devices, receiving, at the first
communication device, a plurality of respective feedback packets
from the plurality of second communication devices, wherein the
feedback packets include feedback generated based on the sounding
packet, and obtaining the one or more quality indicators for each
second communication device based on the feedback packet received
from the second communication device.
[0079] Obtaining, at the first communication device for each second
communication device of the plurality of second communication
devices, one or more quality indicators corresponding to one or
more sub-channel blocks of the OFDM communication channel
associated with the second communication device comprises
transmitting a request frame from the first communication device to
the plurality of second communication devices, wherein the request
frame requests the second communication devices to transmit
respective sounding frames to the first communication device,
receiving, at the first communication device, respective sounding
packets transmitted by the second communication devices in response
to the requests frame, and obtaining the one or more quality
indicators for each second communication device based on the
sounding packet received from the second communication device.
[0080] Obtaining, at the first communication device for each second
communication device of the plurality of second communication
devices, one or more quality indicators corresponding to one or
more sub-channel blocks of the OFDM communication channel
associated with the second communication device comprises
receiving, at the first communication device, respective
non-sounding data units transmitted by the second communication
devices for purposes other than sounding the OFDM communication
channels associated with the second communication devices, and
obtaining the one or more quality indicators for each second
communication device based on the non-sounding packet received from
the second communication device.
[0081] Obtaining, at the first communication device for each second
communication device of the plurality of second communication
devices, one or more quality indicators corresponding to one or
more sub-channel blocks of the OFDM communication channel
associated with the second communication device comprises
obtaining, for each second communication device one or both of (i)
indications of one or more preferred sub-channel blocks for the
second communication device and (ii) indications of order of
preference of multiple preferred sub-channel blocks for the second
communication device.
[0082] The method further includes, prior to transmitting the at
least one OFDMA data unit to the group of second communication
devices, transmitting a group management frame to indicate to the
second communication devices of the group that the second
communication devices are members of the group.
[0083] The method further includes allocating, based on the quality
indicators obtained for the two or more second communication
devices of the group, the respective sub-channel blocks to the two
or more second communication devices of the group.
[0084] The method further includes after transmitting the at least
one OFDMA data unit to the group of second communication devices,
obtaining, for each of the second communication devices of the
group, one or more new quality indicators corresponding to one or
more sub-channel blocks of the OFDM communication channel
associated with the second communication device, allocating
respective sub-channel blocks to the second communication devices
of the group based on the new quality indicators, and transmitting
at least one additional OFDMA data unit that includes respective
OFDM data units directed to the two or more second communication
devices of the group, wherein the respective OFDM data units are
transmitted in respective sub-channel blocks allocated to the two
or more second communication devices based on the new quality
indicators.
[0085] In another embodiment, an apparatus for use in a
communication system comprises a network interface configured to
obtain, for each of a plurality of communication devices, one or
more quality indicators corresponding to one or more sub-channel
blocks of an orthogonal frequency division multiplexing (OFDM)
communication channel associated with the communication device. The
network interface is further configured to select, based on the
quality indicators obtained for each of at least some communication
devices of the plurality of communication devices, a group of
communication devices for orthogonal frequency division multiple
access (OFDMA) communication, wherein the group includes two or
more communication devices of the plurality of communication
devices. The network interface is additionally configured to
transmit, to the group of communication devices, at least one OFDMA
data unit that includes respective OFDM data units directed to the
two or more communication devices of the group, wherein the
respective OFDM data units are transmitted in respective
sub-channel blocks allocated to the two or more communication
devices of the group.
[0086] In other embodiments, the apparatus further includes any
suitable combination of one or more of the following features.
[0087] The network interface is configured to transmit a sounding
packet from the first communication device to the plurality of
communication devices, receive a plurality of respective feedback
packets from the plurality of communication devices, wherein the
feedback packets include feedback generated based on the sounding
packet, and obtain the one or more quality indicators for each
communication device based on the feedback packet received from the
communication device.
[0088] The network interface is configured to transmit a request
frame from the first communication device to the plurality of
communication devices, wherein the request frame requests the
communication devices to transmit respective sounding frames,
receive respective sounding packets transmitted by the
communication devices in response to the request frame, and obtain
the one or more quality indicators for each communication device
based on the sounding packet received from the communication
device.
[0089] The network interface is configured to receive respective
non-sounding data units transmitted by the communication devices
for purposes other than sounding the OFDM communication channels
associated with the communication devices, and obtain the one or
more quality indicators for each communication device based on the
non-sounding packet received from the communication device.
[0090] The network interface is configured to obtain the one or
more quality indicators for each communication device by obtaining
one or both of (i) indications of one or more preferred sub-channel
blocks for the communication device and (ii) indications of order
of preference of multiple preferred sub-channel blocks for the
communication device.
[0091] The network interface is further configured to, prior to
transmitting the at least one OFDMA data unit to the group of
communication devices, transmit a group management frame to
indicate to the communication devices of the group that the
communication devices are members of the group.
[0092] The network interface is further configured to allocate,
based on the quality indicators obtained for the two or more
communication devices of the group, the respective sub-channel
blocks to the two or more communication devices of the group.
[0093] The network interface is further configured to after
transmitting the at least one OFDMA data unit to the group of
communication devices, obtain, for each of the communication
devices of the group, one or more new quality indicators
corresponding to one or more sub-channel blocks of the OFDM
communication channel associated with the communication device,
allocate respective sub-channel blocks to the communication devices
of the group based on the new quality indicators, and transmit at
least one additional OFDMA data unit that includes respective OFDM
data units directed to the two or more communication devices of the
group, wherein the respective OFDM data units are transmitted in
respective sub-channel blocks allocated to the two or more
communication devices based on the new quality indicators.
[0094] In yet another embodiment, a method for simultaneously
communicating with multiple communication devices in a
communication network includes obtaining, at a first communication
device for each of two or more second communication devices in a
group of second communication devices for orthogonal frequency
division multiple access (OFDMA) communication, one or more quality
indicators corresponding to one or more sub-channel blocks of an
orthogonal frequency division multiplexing (OFDM) communication
channel associated with the second communication device. The method
also includes allocating, based on the quality indicators obtained
for each of at least some of the two or more second communication
devices of the group, respective sub-channel blocks to respective
second communication devices of the group. The method additionally
includes transmitting at least one orthogonal frequency division
multiple access (OFDMA) data unit that includes respective OFDM
data units directed to the two or more communication devices of the
group, wherein the respective OFDM data units are transmitted in
respective sub-channel blocks allocated to the two or more
communication devices of group.
[0095] In other embodiments, the method includes any suitable
combination of one or more of the following features.
[0096] Obtaining, at the first communication device for each of two
or more second communication devices in a group of second
communication devices for OFDMA communication, one or more quality
indicators corresponding to one or more sub-channel blocks of the
OFDM communication channel associated with the second communication
device comprises transmitting a sounding packet from the first
communication device to the two or more second communication
devices, receiving, at the first communication device, a plurality
of respective feedback packets from the two or more second
communication devices, wherein the feedback packets include
feedback generated based on the sounding packet, and obtaining the
one or more quality indicators for each second communication device
based on the feedback packet received from the second communication
device.
[0097] Obtaining, at the first communication device for each of two
or more second communication devices in a group of second
communication devices for OFDMA communication, one or more quality
indicators corresponding to one or more sub-channel blocks of the
OFDM communication channel associated with the second communication
device comprises transmitting a request frame from the first
communication device to the two or more second communication
devices, wherein the request frame requests the second
communication devices to transmit respective sounding frames to the
first communication device, receiving, at the first communication
device, respective sounding packets transmitted by the two or more
second communication devices in response to the requests frame, and
obtaining the one or more quality indicators for each second
communication device based on the sounding packet received from the
second communication device.
[0098] Obtaining, at the first communication device for each of two
or more second communication devices in a group of second
communication devices for OFDMA communication, one or more quality
indicators corresponding to one or more sub-channel blocks of the
OFDM communication channel associated with the second communication
device comprises receiving, at the first communication device,
respective non-sounding data units transmitted by the two or more
second communication devices for purposes other than sounding the
OFDM communication channels associated with the second
communication devices, and obtaining the one or more quality
indicators for each second communication device based on the
non-sounding packet received from the second communication
device.
[0099] Obtaining, at the first communication device for each of two
or more second communication devices in a group of second
communication devices for OFDMA communication, one or more quality
indicators corresponding to one or more sub-channel blocks of the
OFDM communication channel associated with the second communication
device comprises obtaining, for each second communication device
one or both of (i) indications of one or more preferred sub-channel
blocks for the second communication device and (ii) indications of
order of preference of multiple preferred sub-channel blocks for
the second communication device.
[0100] The method further includes after transmitting the at least
one OFDMA data unit to the group of second communication devices,
obtaining, for each of the second communication devices of the
group, one or more new quality indicators corresponding to one or
more sub-channel blocks of the OFDM communication channel
associated with the second communication device, allocating
respective sub-channel blocks to the second communication devices
of the group based on the new quality indicators, and transmitting
at least one additional OFDMA data unit that includes respective
OFDM data units directed to the two or more second communication
devices of the group, wherein the respective OFDM data units are
transmitted in respective sub-channel blocks allocated to the two
or more second communication devices based on the new quality
indicators.
[0101] In still another embodiment, an apparatus for use in a
communication system comprises a network interface configured to
obtain, for each of two or more communication devices in a group of
communication devices for orthogonal frequency division multiple
access (OFDMA) communication, one or more quality indicators
corresponding to one or more sub-channel blocks of an orthogonal
frequency division multiplexing (OFDM) communication channel
associated with the communication device. The network interface is
additionally configured to allocate, based on the quality
indicators obtained for each of at least some of the two or more
communication devices of the two or more communication devices,
respective sub-channel blocks to respective communication devices
of the group. The network interface is further configured to
transmit at least one orthogonal frequency division multiple access
(OFDMA) data unit that includes respective OFDM data units directed
to the two or more communication devices of the group, wherein the
respective OFDM data units are transmitted in respective
sub-channel blocks allocated to the two or more communication
devices of group.
[0102] In other embodiments, the apparatus further includes any
suitable combination of one or more of the following features.
[0103] The network interface is configured to transmit a sounding
packet to the two or more communication devices, receive a
plurality of respective feedback packets from the two or more
communication devices, wherein the feedback packets include
feedback generated based on the sounding packet, and obtain the one
or more quality indicators for each communication device based on
the feedback packet received from the communication device.
[0104] The network interface is configured to transmit a request
frame to the two or more communication devices, wherein the request
frame requests the communication devices to transmit respective
sounding frames, receive respective sounding packets transmitted by
the two or more communication devices in response to the requests
frame, and obtain the one or more quality indicators for each
communication device based on the sounding packet received from the
communication device.
[0105] The network interface is configured to receive respective
non-sounding data units transmitted by the two or more
communication devices for purposes other than sounding the OFDM
communication channels associated with the communication devices,
and obtain the one or more quality indicators for each
communication device based on the non-sounding packet received from
the communication device.
[0106] The network interface is configured to obtain the one or
more quality indicators for each communication device by obtaining
one or both of (i) indications of one or more preferred sub-channel
blocks for the communication device and (ii) indications of order
of preference of multiple preferred sub-channel blocks for the
communication device.
[0107] The network interface is further configured to after
transmitting the at least one OFDMA data unit to the group of
communication devices, obtain, for each of the communication
devices of the group, one or more new quality indicators
corresponding to one or more sub-channel blocks of the OFDM
communication channel associated with the communication device,
allocate respective sub-channel blocks to the communication devices
of the group based on the new quality indicators, and transmit at
least one additional OFDMA data unit that includes respective OFDM
data units directed to the two or more communication devices of the
group, wherein the respective OFDM data units are transmitted in
respective sub-channel blocks allocated to the two or more
communication devices based on the new quality indicators.
[0108] At least some of the various blocks, operations, and
techniques described above may be implemented utilizing hardware, a
processor executing firmware instructions, a processor executing
software instructions, or any combination thereof. When implemented
utilizing a processor executing software or firmware instructions,
the software or firmware instructions may be stored in any computer
readable memory such as on a magnetic disk, an optical disk, or
other storage medium, in a RAM or ROM or flash memory, processor,
hard disk drive, optical disk drive, tape drive, etc. Likewise, the
software or firmware instructions may be delivered to a user or a
system via any known or desired delivery method including, for
example, on a computer readable disk or other transportable
computer storage mechanism or via communication media.
Communication media typically embodies computer readable
instructions, data structures, program modules or other data in a
modulated data signal such as a carrier wave or other transport
mechanism. The term "modulated data signal" means a signal that has
one or more of its characteristics set or changed in such a manner
as to encode information in the signal. By way of example, and not
limitation, communication media includes wired media such as a
wired network or direct-wired connection, and wireless media such
as acoustic, radio frequency, infrared and other wireless media.
Thus, the software or firmware instructions may be delivered to a
user or a system via a communication channel such as a telephone
line, a DSL line, a cable television line, a fiber optics line, a
wireless communication channel, the Internet, etc. (which are
viewed as being the same as or interchangeable with providing such
software via a transportable storage medium). The software or
firmware instructions may include machine readable instructions
that, when executed by the processor, cause the processor to
perform various acts.
[0109] When implemented in hardware, the hardware may comprise one
or more of discrete components, an integrated circuit, an
application-specific integrated circuit (ASIC), etc.
[0110] While the present invention has been described with
reference to specific examples, which are intended to be
illustrative only and not to be limiting of the invention, changes,
additions and/or deletions may be made to the disclosed embodiments
without departing from the scope of the invention.
* * * * *