U.S. patent application number 15/025634 was filed with the patent office on 2016-08-18 for hew communication station and method for communicating longer duration ofdm symbols using minimum bandwidth units having tone allocations.
The applicant listed for this patent is Shahrnaz AZIZI, Thomas J. KENNEY, Eldad PERAHIA. Invention is credited to Shahrnaz Azizi, Thomas J. Kenney, Eldad Perahia.
Application Number | 20160241366 15/025634 |
Document ID | / |
Family ID | 53173244 |
Filed Date | 2016-08-18 |
United States Patent
Application |
20160241366 |
Kind Code |
A1 |
Azizi; Shahrnaz ; et
al. |
August 18, 2016 |
HEW COMMUNICATION STATION AND METHOD FOR COMMUNICATING LONGER
DURATION OFDM SYMBOLS USING MINIMUM BANDWIDTH UNITS HAVING TONE
ALLOCATIONS
Abstract
Embodiments of a communication station and method for
communicating in a wireless network are generally described herein.
In some embodiments, the communication station may be to
communicate longer-duration orthogonal frequency division
multiplexed (OFDM) symbols on channel resources in accordance with
an orthogonal frequency division multiple access (OFDMA) technique.
The channel resources may comprise one or more minimum bandwidth
units with each minimum band-width unit having a predetermined
number of data subcarriers. The station may also configure the
minimum bandwidth units in accordance with one of a plurality of
subcarrier allocations for one of a plurality of interleaver
configurations for communication of the longer-duration OFDM
symbols. The longer-duration OFDM symbols may have symbols duration
that is either 2.times. or 4.times. the standard OFDM symbol
duration.
Inventors: |
Azizi; Shahrnaz; (Cupertino,
CA) ; Kenney; Thomas J.; (Portland, OR) ;
Perahia; Eldad; (Portland, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AZIZI; Shahrnaz
KENNEY; Thomas J.
PERAHIA; Eldad |
Cupertino
Port land
Portland |
CA
OR
OR |
US
US
US |
|
|
Family ID: |
53173244 |
Appl. No.: |
15/025634 |
Filed: |
September 26, 2014 |
PCT Filed: |
September 26, 2014 |
PCT NO: |
PCT/US2014/057751 |
371 Date: |
March 29, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61906059 |
Nov 19, 2013 |
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61973376 |
Apr 1, 2014 |
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61976951 |
Apr 8, 2014 |
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61986256 |
Apr 30, 2014 |
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61986250 |
Apr 30, 2014 |
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61991730 |
May 12, 2014 |
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62013869 |
Jun 18, 2014 |
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62024801 |
Jul 15, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 7/0413 20130101;
Y02D 70/122 20180101; H04W 52/0206 20130101; H04W 52/244 20130101;
H04W 72/0406 20130101; Y02D 70/449 20180101; H04L 27/2602 20130101;
H04W 74/08 20130101; H04L 1/0071 20130101; H04B 7/2615 20130101;
H04W 74/04 20130101; H04W 72/042 20130101; H04W 72/0473 20130101;
H04L 5/0094 20130101; H04L 27/3405 20130101; H04L 27/3483 20130101;
H04L 5/0098 20130101; H04L 5/001 20130101; H04W 72/0426 20130101;
H04W 74/0808 20130101; H04W 88/08 20130101; Y02D 70/1262 20180101;
H04L 5/003 20130101; H04W 84/12 20130101; H04W 88/10 20130101; Y02D
70/142 20180101; H04L 5/0035 20130101; H04L 5/0007 20130101; H04W
72/0453 20130101; H04W 74/02 20130101; H04L 5/0048 20130101; H04L
5/0053 20130101; H04L 27/261 20130101; Y02D 30/70 20200801; H04L
5/0037 20130101 |
International
Class: |
H04L 5/00 20060101
H04L005/00; H04B 7/04 20060101 H04B007/04; H04W 72/04 20060101
H04W072/04; H04B 7/26 20060101 H04B007/26 |
Claims
1-20. (canceled)
21. A high-efficiency WLAN (HEW) communication station (STA)
comprising physical layer and medium access control layer circuitry
to: communicate longer-duration orthogonal frequency division
multiplexed (OFDM) symbols on channel resources in accordance with
an orthogonal frequency division multiple access (OFDMA) technique,
the channel resources comprising one or more minimum bandwidth
units, each minimum bandwidth unit having a predetermined number of
data subcarriers; and configure the minimum bandwidth units in
accordance with one of a plurality of subcarrier allocations for
one of a plurality of interleaver configurations for communication
of the longer-duration OFDM symbols, wherein the longer-duration
OFDM symbols have symbol duration that is either 2.times. or
4.times. a standard OFDM symbol duration.
22. The communication station of claim 21 wherein the station is to
process the longer-duration OFDM symbols with a fast-Fourier
Transform (FFT), wherein for processing the longer-duration OFDM
symbols with a 256-point FFT without code-rate exclusions, the
predetermined number of data subcarriers for the minimum bandwidth
unit is to be of 48, 54 or 60 data subcarriers, and wherein for
processing the longer-duration (ADM symbols with a 128-point FFT
without code-rate exclusions, the number of data subcarriers for
the minimum bandwidth unit is to be of 28 or 30 data
subcarriers.
23. The communication of station of claim 22, wherein for
processing the longer-duration OFDM symbols with the 256-point FFT
with a code-rate exclusion of 5/6 for 256-QAM, the number of data
subcarriers for the minimum bandwidth unit is to be of 48, 50, 54,
57, 54, 56, 60 or 62 data subcarriers, and wherein for processing
the longer-duration OFDM symbols with the 128-point FFT with a
code-rate exclusion of 5/6 for 256-QAM, the number of data
subcarriers for the minimum bandwidth unit is to be of 24, 26, 28
or 30 data subcarriers.
24. The communication station of claim 23 wherein the station is
further to concurrently communicate using up to four of the minimum
bandwidth units over channels of 20 MHz or 40 MHz during a control
period in accordance with the OFDMA technique.
25. The communication station of claim 24, wherein for a minimum
bandwidth unit having 54 data subcarriers for 256-point FFT
processing, the subcarrier allocation comprises 256 total
subcarriers including: 54 data subcarriers and 3 pilot subcarriers
for each of the four minimum bandwidth units used for communicating
within either channels of 20 MHz or 40 MHz, 2-4 null-subcarriers at
DC, and 12-13 guard subcarriers at each band edge.
26. The communication station of claim 24 wherein the
physical-layer circuitry includes a block interleaver having a
depth of one OFDM symbol, the block interleaver being configurable
to interleave a block of encoded data, and wherein the interleaver
configurations comprise a number of columns and a number of rows,
the number of rows based on a number of coded bits per subcarrier
per stream.
27. The communication station of claim 26, wherein for a minimum
bandwidth unit having 54 data subcarriers for 256-point FFT
processing, the interleaver configuration has 9 columns and a
number of rows equaling 3 times a number of coded bits per single
subcarrier.
28. The communication station of claim 26, wherein the
communication station further comprises: an encoder to encode input
data prior to interleaving in accordance with one of a plurality of
code rates; and a constellation mapper to map the encoded data
after the interleaving to a QAM constellation, wherein the encoder
and mapper operate in accordance with one of a plurality of
predetermined modulation and coding scheme (MCS) combinations for
the subcarrier allocation, wherein the plurality of predetermined
MCS combinations for the subcarrier allocation are restricted to an
integer number of coded bits per OFDM symbol (Ncbps) and an integer
number of data bits per OFDM symbol (Ndbps).
29. The communication station of claim 21 wherein the
longer-duration OFDM symbols are to be selected for larger delay
spread environments, and wherein standard-duration OFDM symbols are
to be selected for smaller delay-spread environments.
30. The communication station of claim 29 wherein the
standard-duration OFDM symbols have a symbol duration that ranges
from 3.6 micro-seconds (us) including a 400 nanosecond (ns) short
guard interval to 4 us including an 800 ns guard interval, and
wherein the longer-duration OFDM symbols have a symbol duration is
one of either 2.times. or 4.times. the duration of the
standard-duration OFDM symbols.
31. The communication station of claim 21 further comprising one or
more processors and memory, and wherein the physical layer
circuitry includes a transceiver.
32. The communication station of claim 31 further comprising two
antennas coupled to the transceiver.
33. A method performed by a high-efficiency WLAN (HEW)
communication station (STA) comprising: communicating
longer-duration orthogonal frequency division multiplexed (OFDM)
symbols on channel resources in accordance with an orthogonal
frequency division multiple access (OFDMA) technique, the channel
resources comprising one or more minimum bandwidth units, each
minimum bandwidth unit having a predetermined number of data
subcarriers; and configuring the minimum bandwidth units in
accordance with one of a plurality of subcarrier allocations for
one of a plurality of interleaver configurations for communication
of the longer-duration OFDM symbols, wherein the longer-duration
OFDM symbols have symbol duration that is either 2.times. or
4.times. a standard OFDM symbol duration.
34. The method of claim 33 further comprising processing the
longer-duration OFDM symbols with a fast-Fourier Transform (FFT),
wherein for processing the longer-duration OFDM symbols with a
256-point FFT without code-rate exclusions, the predetermined
number of data subcarriers for the minimum bandwidth unit is to be
of 48, 54 or 60 data subcarriers, and wherein for processing the
longer-duration OFDM symbols with a 128-point FFT without code-rate
exclusions, the number of data subcarriers for the minimum
bandwidth unit is to be of 28 or 30 data subcarriers.
35. The method of claim 34, wherein for processing the
longer-duration OFDM symbols with the 256-point FFT with a
code-rate exclusion of 5/6 for 256-QAM, the number of data
subcarriers for the minimum bandwidth unit is to be of 48, 50, 54,
52, 54, 56, 60 or 62 data subcarriers, and wherein for processing
the longer-duration OFDM symbols with the 128-point FFT with a
code-rate exclusion of 5/6 for 256-QAM, the number of data
subcarriers for the minimum bandwidth unit is to be of 24, 26, 28
or 30 data subcarriers.
36. The method of claim 33 further comprising: selecting the
longer-duration OFDM symbols for larger delay spread environments;
and selecting the standard-duration OFDM symbols for smaller
delay-spread environments.
37. A non-transitory computer-readable storage medium that stores
instructions for execution by one or more processors to perform
operations to configure a high-efficiency WLAN (HEW) communication
station (STA) to: communicate longer-duration orthogonal frequency
division multiplexed (OFDM) symbols on channel resources in
accordance with an orthogonal frequency division multiple access
(OFDMA) technique, the channel resources comprising one or more
minimum bandwidth units, each minimum bandwidth unit having a
predetermined number of data subcarriers; and configure the minimum
bandwidth units in accordance with one of a plurality of subcarrier
allocations for one of a plurality of interleaver configurations
for communication of the longer-duration OFDM symbols; wherein the
longer-duration OFDM symbols have symbol duration that is either
2.times. or 4.times. a standard OFDM symbol duration.
38. The non-transitory computer-readable storage medium of claim
37, wherein the longer-duration OFDM symbols are processed with a
fast-Fourier Transform (FFT), wherein for processing the
longer-duration OFDM symbols with a 256-point FFT without code-rate
exclusions, the predetermined number of data subcarriers for the
minimum bandwidth unit is to be of 48, 54 or 60 data subcarriers,
and wherein for processing the longer-duration OFDM symbols with a
128-point FFT without code-rate exclusions, the number of data
subcarriers for the minimum bandwidth unit is to be of 28 or 30
data subcarriers.
39. The non-transitory computer-readable storage medium of claim
38, wherein for processing the longer-duration OFDM symbols with
the 256-point FFT with a code-rate exclusion of 5/6 for 256-QAM,
the number of data subcarriers for the minimum bandwidth unit is to
be of 48, 50, 54, 52, 54, 56, 60 or 62 data subcarriers, and
wherein for processing the longer-duration OFDM symbols with the
128-point FFT with a code-rate exclusion of 5/6 for 256-QAM, the
number of data subcarriers for the minimum bandwidth unit is to be
of 24, 26, 28 or 30 data subcarriers.
40. The non-transitory computer-readable storage medium of claim
37, wherein the longer-duration OFDM symbols are to be selected for
larger delay spread environments, and the standard-duration OFDM
symbols are to be selected for smaller delay-spread environments.
Description
PRIORITY CLAIMS
[0001] This application claims the benefit of priority to the
following United States Provisional Patent Applications:
[0002] Ser. No. 61/906,059, filed Nov. 19, 2013,
[0003] Ser. No. 61/973,376, filed Apr. 1, 2014,
[0004] Ser. No. 61/976,951, filed Apr. 8, 2014,
[0005] Ser. No. 61/986,256, filed Apr. 30, 2014,
[0006] Ser. No. 61/986,250, filed Apr. 30, 2014,
[0007] Ser. No. 61/991,730, filed May 12, 2014,
[0008] Ser. No. 62/013,869, filed Jun. 18, 2014, and
[0009] Ser. No. 62/024,801, filed Jul. 15, 2014,
which are all incorporated herein by reference in their
entireties.
TECHNICAL FIELD
[0010] Embodiments pertain to wireless networks. Some embodiments
relate to wireless local area networks (WLANs) and Wi-Fi networks
including networks operating in accordance with the IEEE 802.11
family of standards. Some embodiments relate to the High Efficiency
WLAN Study Group (HEW SG) (named DensiFi) and referred to as the
IEEE 802.11ax SG. Some embodiments relate to high-efficiency
wireless or high-efficiency WLAN (HEW) communications.
BACKGROUND
[0011] Wireless communications has been evolving toward ever
increasing data rates (e.g., from IEEE 802.11a/g to IEEE 802.11n to
IEEE 802.11 ac). In high-density deployment situations, overall
system efficiency may become more important than higher data rates.
For example, in high-density hotspot and cellular offloading
scenarios, many devices competing for the wireless medium may have
low to moderate data rate requirements (with respect to the very
high data rates of IEEE 802.11 ac). The frame structure used for
conventional and legacy IEEE 802.11 communications including
very-high throughput (VHT) communications may be less suitable for
such high-density deployment situations. A recently-formed study
group for Wi-Fi evolution referred to as the IEEE 802.11 HEW SG
(i.e., IEEE 802.11ax) is addressing these high-density deployment
scenarios.
[0012] One issue with HEW is defining an efficient communication
structure that is able to reuse at least some 802.11 ac hardware,
such as a block interleaver. Another issue with HEW is defining an
efficient communication structure that suitable for use with longer
OFDM symbol durations.
[0013] Thus, there are general needs for devices and methods that
improve overall system efficiency in wireless networks,
particularly for high-density deployment situations. There are also
general needs for devices and methods suitable for HEW
communications. There are also general needs for devices and
methods suitable for HEW communications that can communicate in
accordance with an efficient communication structure and that is
able to reuse at least some conventional hardware. There are also
general needs for devices and methods suitable for HEW
communications that can communicate in accordance with an efficient
communication structure for using OFDM symbols of a longer
duration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 illustrates a HEW network in accordance with some
embodiments;
[0015] FIG. 2 is a physical-layer block diagram of an HEW
communication station in accordance with some embodiments;
[0016] FIG. 3 illustrates an HEW device in accordance with some
embodiments; and
[0017] FIG. 4 is a procedure for communicating using minimum
bandwidth units in accordance with some embodiments.
DETAILED DESCRIPTION
[0018] The following description and the drawings sufficiently
illustrate specific embodiments to enable those skilled in the art
to practice them. Other embodiments may incorporate structural,
logical, electrical, process, and other changes. Portions and
features of some embodiments may be included in, or substituted
for, those of other embodiments. Embodiments set forth in the
claims encompass all available equivalents of those claims
[0019] Some embodiments disclosed herein provide systems and
methods for tone allocation in a HEW network. In some embodiments a
master station may allocates tones for HEW to provide a smallest
orthogonal frequency division multiple access (OFDMA) bandwidth
unit (i.e., a minimum bandwidth unit). In some embodiments, an HEW
communication station may be configured to communicate
longer-duration orthogonal-frequency division multiplexed (OFDM)
symbols on channel resources that comprise one or more minimum
bandwidth units. Each minimum bandwidth unit may have a
predetermined bandwidth and the minimum bandwidth units may be
configured in accordance with one of a plurality of subcarrier
(i.e., tone) allocations for one of a plurality of interleaver
configurations. In some embodiments, optimum subcarrier allocations
and interleaver size combinations are provided for use with the
OFDMA minimum bandwidth units for communication using
longer-duration OFDM symbols. These embodiments are discussed in
more detail below. Some embodiments disclosed herein are applicable
to communications using longer-duration OFDM symbols (e.g., larger
FFT sizes).
[0020] FIG. 1 illustrates a HEW network in accordance with some
embodiments. HEW network 100 may include a master station (STA)
102, a plurality of HEW stations 104 (HEW devices), and a plurality
of legacy stations 106 (legacy devices). The master station 102 may
be arranged to communicate with the HEW stations 104 and the legacy
stations 106 in accordance with one or more of the IEEE 802.11
standards. In accordance with some HEW embodiments, the master
station 102 and may be arranged to contend for a wireless medium
(e.g., during a contention period) to receive exclusive control of
the medium for an HEW control period (i.e., a transmission
opportunity (TXOP)). The master station 102 may, for example,
transmit a master-sync or control transmission at the beginning of
the HEW control period to indicate, among other things, which HEW
stations 104 are scheduled for communication during the HEW control
period. During the HEW control period, the scheduled HEW stations
104 may communicate with the master station 102 in accordance with
a non-contention based multiple access technique. This is unlike
conventional Wi-Fi communications in which devices communicate in
accordance with a contention-based communication technique, rather
than a non-contention based multiple access technique. During the
HEW control period, the master station 102 may communicate with HEW
stations 104 (e.g., using one or more HEW frames). During the HEW
control period, legacy stations 106 may refrain from communicating.
In some embodiments, the master-sync transmission may be referred
to as a control and schedule transmission.
[0021] In some embodiments, the multiple-access technique used
during the HEW control period may be a scheduled OFDMA technique,
although this is not a requirement. In some embodiments, the
multiple access technique may be a time-division multiple access
(TDMA) technique or a frequency division multiple access (FDMA)
technique which may be combined with OFDMA. In some embodiments,
the multiple access technique may be a space-division multiple
access (SDMA) technique including a multi-user (MU) multiple-input
multiple-output (MIMO) (MU-MIMO) technique, which may be combined
with OFDMA. These multiple-access techniques used during the HEW
control period may be configured for uplink or downlink data
communications.
[0022] The master station 102 may also communicate with legacy
stations 106 in accordance with legacy IEEE 802.11 communication
techniques (outside the control period). In some embodiments, the
master station 102 may also be configurable communicate with the
HEW stations 104 outside the HEW control period in accordance with
legacy IEEE 802.11 communication techniques, although this is not a
requirement.
[0023] In some embodiments, the HEW communications during the
control period may be configurable to have bandwidths of one of 20
MHz, 40 MHz, or 80 MHz contiguous bandwidths or an 80+80 MHz (160
MHz) non-contiguous bandwidth. In some embodiments, a 320 MHz
channel width may be used. In some embodiments, subchannel
bandwidths less than 20 MHz may also be used. In these embodiments,
each channel or subchannel of an HEW communication may be
configured for transmitting a number of spatial streams. HEW
communications during the control period may be uplink or downlink
communications.
[0024] In accordance with embodiments, an HEW station (e.g., master
station 102 or an HEW station 104) may be configured to communicate
longer-duration orthogonal frequency division multiplexed (OFDM)
symbols on channel resources in accordance with an OFDMA technique.
The channel resources may comprise one or more minimum bandwidth
units and each minimum bandwidth unit may have a predetermined
number of data subcarriers. The longer-duration OFDM symbols may
have symbol duration that is either 2.times. or 4.times. a standard
OFDM symbol duration (i.e., the symbol time (e.g., T.sub.symbol)).
The minimum bandwidth units may be configured in accordance with
one of a plurality of subcarrier allocations for one of a plurality
of interleaver configurations. These embodiments are discussed in
more detail below. Some of the embodiments disclosed herein may be
applicable to IEEE 802.11ax and HEW networks operating with a
longer OFDM symbol duration (e.g., twice (2.times.) and four times
(4.times.) the standard symbol duration).
[0025] As discussed in more detail below, an HEW station may
comprise physical layer (PHY) and medium access control (MAC) layer
circuitry. In some embodiments, the PHY circuitry may include a
block interleaver having a depth of one OFDM symbol. The block
interleaver may be configurable to interleave a block of encoded
data in accordance with any one of the plurality of interleaver
configurations. The interleaver configurations may comprise a
number of columns and a number of rows.
[0026] FIG. 2 is a physical-layer block diagram of an HEW
communication station in accordance with some embodiments. The PHY
layer circuitry 200 may be suitable for use as a portion of the
physical layer of an HEW communication station, such as master
station 102 (FIG. 1) and/or HEW communication station 104 (FIG. 1).
As illustrated in FIG. 2, the PHY layer circuitry 200 may include,
among other things, one or more encoders 208, one or more block
interleavers 214 and one or more constellation mappers 216. Each of
the encoders 208 may be configured to encode input data prior to
interleaving by the interleavers 214. Each of the constellation
mappers 216 may be configured to map interleaved data to a
constellation (e.g., a QAM constellation) after interleaving. Each
interleaver 214 may be configured to interleave a block of encoded
data in accordance with any one of the plurality of interleaver
configurations. In some embodiments, the encoders 208 may be binary
convolutional code (BCC) encoders. An FFT may be performed on the
constellation-mapped symbols provided by the constellation mappers
to generate time-domain signals for transmission.
[0027] In accordance with embodiments, the encoders 208 and mappers
216 operate in accordance with one of a plurality of predetermined
modulation and coding scheme (MCS) combinations for the particular
subcarrier allocation (i.e., the tone allocation). The plurality of
predetermined MCS combinations for the subcarrier allocation may be
restricted to an integer number of coded bits per OFDM symbol
(Ncbps) and an integer number of data bits per OFDM symbol (Ndbps).
In these embodiments, the number of coded bits per OFDM symbol
(Ncbps) is an integer number and number of data bits per OFDM
symbol (Ndbps) is an integer number. The predetermined MCS
combinations and subcarrier allocations that may be used may
include modulation orders of BPSK, QPSK, 16-QAM, 64-QAM and 256-QAM
and coding rates of 1/2, 3/4, 2/3 and 5/6 provided that both the
Ncbps and the Ndbps are integers. A non-integer Ndbps may result in
a non-integer number of padding bits or the number of encoded bits
exceeding the number of OFDM symbols which may lead to a minimum of
one additional OFDM symbol comprised of only padding bits. An
integer Ndbps may guarantee that all data lengths work with no
additional padding using the 1 ln "Number of OFDM Symbols",
equation (20-32) in 802.11 2012 spec. Thus, embodiments disclosed
herein may be restricted certain MCS combinations and subcarrier
allocations. In these embodiments, the interleaver hardware
architecture configurations are within the boundaries of an IEEE
802.11 interleaver allowing reuse of the legacy 802.11 hardware
blocks for HEW.
[0028] In these embodiments, prior to interleaving, the
communication station is configured to encode the input data based
on a coding rate and subsequent to the interleaving, the
communication station may be configured to constellation map
interleaved bits to QAM constellation points based on a modulation
level. The coding rate and modulation level may be in accordance
with one of the predetermined MCS combinations for the particular
subcarrier allocation. These embodiments are described in more
detail below.
[0029] In some embodiments, each minimum bandwidth unit may be
configurable for communication of between one and four spatial
streams. In these embodiments, an SDMA or MIMO technique may be
used during the control period to communicate the spatial
streams.
[0030] Embodiments disclosed herein provide a number of data
subcarriers, number of pilot subcarriers, and the size of block
interleaver for the case of binary convolutional code (BCC) coding.
In some embodiments, the structure of the OFDMA waveform for 802.1
lax described in United States Provisional Patent Application, Ser.
No. 61/976,951, may be suitable for use, although this is not a
requirement. Some embodiments disclosed herein describe the minimum
bandwidth unit for the OFDMA waveform and describe an architecture
of the subcarrier allocation. In some embodiments, the subcarrier
allocation may be configured to reuse the IEEE 802.11 ac hardware
to create the new OFDMA structure.
[0031] As outlined above, various embodiments disclosed herein
provide a design of a smallest OFDMA bandwidth unit suitable for
IEEE 802.11 ax configured networks operating with longer symbol
duration (e.g., 2.times., 4.times. of the 1 ln/ac OFDM symbol
duration) (e.g., larger FFT sizes). These embodiments provide a
number of data subcarriers, number of pilot subcarriers, and the
size of block interleaver for the case of BCC coding. Disclosed
herein are the possible allocations that are consistent with the
IEEE 802.11ac interleave configurations. Some of the more
preferable allocations may provide reduced overhead and ease of
implementation, particularly when reuse of the IEEE 802.11 ac
architecture is considered.
[0032] The longer symbol duration may be of particular interest for
use in an outdoor environment where a more efficient cyclic prefix
(CP) can be used to overcome the longer delay spread. Other
benefits may include reduced CP overhead and a more relaxed clock
timing accuracy than in an indoor environment.
[0033] The better configurations for the block interleaver may be
based on the channel model, the MCS and other parameters, and may
be determined by system simulation. Since the intent of the
embodiments disclosed herein is to define subcarrier allocations,
an exhaustive search within boundaries was performed to arrive at
the reasonable subcarrier allocations.
[0034] Embodiments disclosed here provide for reuse, to a large
extent, existing system parameters and system blocks. This makes
the evolution less complicated and smaller through the reuse of
existing system blocks and thus hardware, and thus less expensive.
Therefore, the embodiments disclosed herein provide for reuse of
the currently defined interleaver structure (with extensions for
the narrower bandwidth), current code rates (with the ability to
modify the rate) and modulation types (with the ability to modify
the modulation size).
[0035] In an OFDMA system, the total number of subcarriers used in
the smallest bandwidth unit may be a system design parameter. From
this total subcarrier count, the OFDMA system has subcarriers that
are assigned to data (used for data), pilot (typically used for
time/frequency and channel tracking), guard (used to conform to a
spectral mask) and the subcarriers at DC and around DC (to simplify
direct conversion (DC) receiver designs). For example, in 20 MHz
802.11ac, the fixed subcarrier spacing is 312.5 kHz and thus the
total number of subcarriers is 64. Of these 64 subcarriers, 52 are
used for data, 1 for DC (i.e., nulled), 4 for pilot and the
remaining 7 are used for guard (i.e., nulled).
[0036] Embodiments disclosed herein provide subcarrier allocations
based on the set of modulation types used in previous systems
(i.e., BPSK, QPSK, 16-QAM, 64 QAM and 256 QAM). The code rates (r)
utilized in previous systems include the following set r=1/2, 3/4,
2/3 and 5/6. This set is not used for all modulation types in
previous systems, but this does include all current rates used over
the entire modulation set. To determine the valid subcarrier
allocations, the same modulation and coding assignments may be used
as done in the previous systems (e.g., IEEE 802.11a/.11n/.11ac). As
outlined above, the embodiments disclosed herein may utilize the
existing channel interleaver used in previous 802.11 systems. The
channel interleaver is defined in section 22.3.10.8 of the IEEE
Std. 802.11ac-2013, "IEEE Standard for Information
Technology-Telecommunications and information exchange between
systems--Local and metropolitan area networks--Part 11: Wireless
LAN Medium Access Control (MAC) and Physical Layer (PHY)
specifications, Amendment 4: Enhancements for Very High Throughput
for Operation in Bands below 6 GHz". In that text, the interleaver
parameters are outline in Table 22-17 "Number of Rows and columns
in the interleaver". The table is provided here for completeness
for the case of 1 to 4 spatial streams.
TABLE-US-00001 TABLE 22-17 Number of rows and columns in the
interleaver Parameter 20 MHz 40 MHz 80 MHz Ncol 13 18 26 Nrow 4
.times. N.sub.BPSCS 6 .times. N.sub.BPSCS 9 .times. N.sub.BPSCS
Nrot 11 29 58
[0037] In IEEE 802.11n, the introduction of a 40 MHz bandwidth
channel reused the existing interleaver algorithm with
modifications to the matrix size defined to write and read the
data. In IEEE 802.11 ac, with the introduction of an 80 MHz
bandwidth channel, the same interleaver algorithm was utilized.
These parameters define the number of coded symbols that are stored
in the interleaver. Some embodiments disclosed herein may also
reuse the existing interleaver algorithm with new values to define
N.sub.COL and N.sub.ROW for a minimum bandwidth unit. The N.sub.ROT
operation defines a rotation of the values when more than one
spatial stream exists but does not define the interleaver size and
thus will not affect the subcarrier allocation.
[0038] As can be seen in the table above, the N.sub.ROW is a
constant times the number of coded bits per subcarrier per stream.
Thus, the interleaver physical size is a function of the MCS.
Embodiments disclosed herein may define the constant (y), used in
computing N.sub.ROW.
[0039] Using the above constraints a set of subcarrier allocations
can be attained. As mentioned above, some of these embodiments are
applicable to the longer symbol duration for the minimum bandwidth
unit that allow multiplexing of up to four users within a 20 MHz
channel bandwidth. These embodiments may be expandable to
multiplexing of more than four users by dividing the allocations
evenly to smaller allocations. For example, if multiplexing of
eight users is of interest then the tone count found for that case
of four users can be divided in each allocation evenly among two
users to provide tone count for 2.times. of four users assuming
that tone count is divisible by two. If however, the tone count is
not divisible by 2 but it is divisible by 3, then multiplexing of
3.times. of four users will be possible.
[0040] As mentioned above in 20 MHz 802.11ac, the fixed (i.e.,
standard)* subcarrier spacing is 312.5 kHz and thus the total
number of subcarrier is 64. Of these 64, 52 are used for data, 1
for DC (assumed nulled), 4 for pilot and the remaining 7 are used
for guard (assumed nulled). In accordance with embodiments, for a
2.times. and a 4.times. symbol duration, the FFT sizes may be 128
and 256, respectively. Embodiments disclosed herein may provide
from 24 to 32 subcarriers for each of four users for the data
subcarriers, which would then allow 4 to 0 null subcarriers
respectively for 4 users for 128-point FFT, and may provide from 48
to 64 subcarriers for each of four users for the data subcarriers,
which would then allow 16 to 0 null subcarriers respectively for 4
users for 256-point FFT. To determine if a configuration is
suitable for use, a set of equations may be used based on the
following set of variables defined below:
TABLE-US-00002 N.sub.SD Number of Data subcarriers N.sub.CBPS
Number of coded bits per symbol N.sub.BPSCS Number of coded bits
per single carrier N.sub.DBPS Number of data bits per symbol
N.sub.ROW Interleaver Row size, equal to y * N.sub.BPSCS r code
rate M Modulation order (1 = BPSK, 2 = QPSK, 4 = 16-QAM, 6 = 64
QAM, 8= 256-QAM and 10 = 1024-QAM With those definitions the set of
procedures and equations to determine if a configuration is valid
is outlined below: 1. Select the number of Data subcarriers to test
(N.sub.SD ) 2. Compute N.sub.CBPS = N.sub.SD * M 3. Compute
N.sub.BPSCS = N.sub.CBPS * N.sub.SD 4. Compute N.sub.ROW = y *
N.sub.BPSCS; (where y is the assigned interleaver parameter) 5.
Compute INT.sub.DIM = N.sub.ROW * N.sub.COL 6. Compute Z = N CBPS
INT DIM ##EQU00001## 7. Compute M.sub.1 = Z - .left
brkt-bot.Z.right brkt-bot. 5. Compute M.sub.2 = N.sub.DBPS - .left
brkt-bot.N.sub.DBPS.right brkt-bot. 9. Test if ((M.sub.1 = 0) &
(M.sub.2 = 0)) Then Valid, else not Thus if M.sub.1 & M.sub.2 =
0, then configuration using this code rate and modulation is
allowable, otherwise disallowed.
[0041] Assuming that all modulations can be supported as in IEEE
802.11ac for 40MHz including 64QAM and 256QAM (introduced in
802.11ac) with code rates of 3/4 and 5/6, the suitable allocations
allowed for a 256-point FFT are shown in Table 1 below and may
include:
TABLE-US-00003 TABLE I NRow NCol Nsd 2 2 48 3 2 48 4 2 48 6 2 48 8
2 48 12 2 48 24 2 48 2 3 48 4 3 48 8 3 48 16 3 48 2 4 48 3 4 48 4 4
48 6 4 48 12 4 48 2 6 48 4 6 48 8 6 48 2 8 48 3 8 48 6 8 48 2 12 48
4 12 48 3 16 48 2 24 48 3 2 54 9 2 54 27 2 54 2 3 54 3 3 54 6 3 54
9 3 54 18 3 54 3 6 54 9 6 54 2 9 54 3 9 54 6 9 54 3 18 54 2 27 54 2
2 60 3 2 60 5 2 60 6 2 60 10 2 60 15 2 60 30 2 60 2 3 60 4 3 60 5 3
60 10 3 60 20 3 60 3 4 60 5 4 60 15 4 60 2 5 60 3 5 60 4 5 60 6 5
60 12 5 60 2 6 60 5 6 60 10 6 60 2 10 60 3 10 60 6 10 60 5 12 60 2
15 60 4 15 60 3 20 60 2 30 60
[0042] Table I shows three possibilities for the number of data
tones: 48, 54 and 60 that would leave total of 64, 40, and 16 extra
subcarriers within the 20 MHz. These extra subcarriers may be used
for pilot tones per each subchannels, null at DC, and null
subcarriers as guard bands, for example in a 20 MHz channel 54 data
subcarriers, and 3 pilot tones can be assigned to each of four
users plus three nulls at DC and 13 nulls on the left guard and 12
nulls on the right guard for the total of
4.times.(54+3)+3+13+12=256 subcarriers. This example allocation is
within the current interleaver and supports all MCSs that result
with several interleaver dimensions to select from. Among choices
for interleaver dimensions, a closer to a square shape may be
preferred (e.g., N.sub.COL=6, and N.sub.ROW=9), although other
interleaver dimensions are also suitable.
[0043] In these embodiments, the master station 102 may be
configured to process the longer-duration OFDM symbols with a
fast-Fourier Transform (FFT). For processing the longer-duration
OFDM symbols with a 256-point FFT without code-rate exclusions, the
predetermined number of data subcarriers for the minimum bandwidth
unit may be limited to one of 48, 54 and 60 data subcarriers. The
interleaver configurations for these embodiments are shown in Table
I.
[0044] The suitable allocations allowed for a 128-point FFT are
shown in Table II below are:
TABLE-US-00004 TABLE II NRow NCol Nsd NRow NCol Nsd 2 2 24 3 2 30 3
2 24 5 2 30 4 2 24 15 2 30 6 2 24 2 3 30 12 2 24 5 3 30 2 3 24 10 3
30 4 3 24 2 5 30 8 3 24 3 5 30 2 4 24 6 5 30 3 4 24 5 6 30 6 4 24 3
10 30 2 6 24 2 15 30 4 6 24 3 8 24 2 12 24
[0045] In these embodiments, for processing the longer-duration
OFDM symbols with a 128-point FFT without code-rate exclusions, the
number of data subcarriers for the minimum bandwidth unit may be
limited to one of 28 and 30 data subcarriers. The interleaver
configurations for these embodiments are shown in Table II.
[0046] The suitable allocations for a 256-point FFT without support
of code rate 5/6 with 256 QAM are shown in Table III below (e.g.,
the exclusion that is used for 20MHz in 802.11ac):
TABLE-US-00005 TABLE III NRow NCol Nsd 2 2 48 3 2 48 4 2 48 6 2 48
8 2 48 12 2 48 24 2 48 2 3 48 4 3 48 8 3 48 16 3 48 2 4 48 3 4 48 4
4 48 6 4 48 12 4 48 2 6 48 4 6 48 8 6 48 2 8 48 3 8 48 6 8 48 2 12
48 4 12 48 3 16 48 2 24 48 5 2 50 25 2 50 2 5 50 5 5 50 10 5 50 5
10 50 2 25 50 2 2 52 13 2 52 26 2 52 13 4 52 2 13 52 4 13 52 2 26
52 3 2 54 9 2 54 27 2 54 2 3 54 3 3 54 6 3 54 9 3 54 18 3 54 3 6 54
9 6 54 2 9 54 3 9 54 6 9 54 3 18 54 2 27 54 2 2 56 4 2 56 7 2 56 14
2 56 28 2 56 2 4 56 7 4 56 14 4 56 2 7 56 4 7 56 8 7 56 7 8 56 2 14
56 4 14 56 2 28 56 29 2 58 2 29 58 2 2 60 3 2 60 5 2 60 6 2 60 10 2
60 15 2 60 30 2 60 2 3 60 4 3 60 5 3 60 10 3 60 20 3 60 3 4 60 5 4
60 15 4 60 2 5 60 3 5 60 4 5 60 6 5 60 12 5 60 2 6 60 5 6 60 10 6
60 2 10 60 3 10 60 6 10 60 5 12 60 2 15 60 4 15 60 3 20 60 2 30 60
31 2 62 2 31 62
[0047] In these embodiments, for processing the longer-duration
OFDM symbols with the 256-point FFT with a code-rate exclusion of
5/6 for 256-QAM, the number of data subcarriers for the minimum
bandwidth unit may be limited to one of 48, 50, 54, 52, 54, 56, 60
and 62 data subcarriers. The interleaver configurations for these
embodiments are shown in Table III.
[0048] The suitable allocations for a 128-point FFT without support
of code rate 5/6 with 256 QAM are shown in Table IV below (e.g.,
the exclusion that is used for 20MHz in 802.11 ac):
TABLE-US-00006 TABLE IV NRow NCol Nsd NRow NCol Nsd 2 2 24 2 2 28 3
2 24 7 2 28 4 2 24 14 2 28 6 2 24 7 4 28 12 2 24 2 7 28 2 3 24 4 7
28 4 3 24 2 14 28 8 3 24 3 2 30 2 4 24 5 2 30 3 4 24 15 2 30 6 4 24
2 3 30 2 6 24 5 3 30 4 6 24 10 3 30 3 8 24 2 5 30 2 12 24 3 5 30 13
2 26 6 5 30 2 13 26 5 6 30 3 10 30 2 15 30
[0049] In these embodiments, for processing the longer-duration
OFDM symbols with the 128-point FFT with a code-rate exclusion of
5/6 for 256-QAM, the number of data subcarriers for the minimum
bandwidth unit may be limited to one of 24, 26, 28 and 30 data
subcarriers. The interleaver configurations for these embodiments
are shown in Table IV.
[0050] In some embodiments, the master station 102 may be
configured to concurrently communicate using up to four of the
minimum bandwidth units over channels of 20 MHz or 40 MHz during a
control period in accordance with the OFDMA technique. In these
embodiments when communicating using four minimum bandwidth units
over a channel bandwidth, the master station 102 may communicate
concurrently with up to four HEW stations 104 during the control
period in accordance with an OFDMA technique. In these embodiments,
when a 2.times. longer symbol duration is used in a 20 MHz channel
bandwidth, for example, the subcarrier spacing may be reduced by a
factor of two (e.g., half of 312.5 KHz), when a 4.times. longer
symbol duration is used in a 20 MHz channel bandwidth, the
subcarrier spacing may be reduced by a factor of four. In these
embodiments, a subcarrier allocation with more guard subcarriers
may be used for closer subcarrier spacing. In some embodiments, the
station 102 may be configured to concurrently communicate using up
to four of the minimum bandwidth units of each 20 MHz portion of a
40 MHz channel, an 80MHz channel and a 160 MHz channel.
[0051] In some embodiments, for a minimum bandwidth unit having 54
data subcarriers for 256-point FFT processing, one example of a
subcarrier allocation comprises 256 total subcarriers including: 54
data subcarriers and 3 pilot subcarriers for each of the four
minimum bandwidth units used for communicating within either
channels of 20 MHz or 40 MHz, 2-4 null-subcarriers at DC, and 12-13
guard subcarriers at each band edge. For this example subcarrier
allocation, the interleaver configurations shown in Table I may be
suitable and support all current MCS configuration (i.e., without
any code-rate restrictions).
[0052] In some embodiments, for a minimum bandwidth unit having 54
data subcarriers for 256-point FFT processing, one example of a
subcarrier allocation that comprises 256 total subcarriers may
include 54 data subcarriers and 3 pilot subcarriers for each of the
four minimum bandwidth units used for communicating within either
20 MHz or 40 MHz channel bandwidth, 3 null-subcarriers at DC, 12
guard subcarriers at one band edge, and 13 guard subcarriers at the
other band edge (e.g., the left and right side), for a total of 256
subcarriers (i.e., 4.times.(54+3)+3+12+13=256. For this example
subcarrier allocation, the interleaver configurations shown in
Table I may be suitable and support all current MCS configuration
(i.e., without any code-rate restrictions). Other subcarrier
allocations may also be suitable for use.
[0053] In some embodiments, the block interleaver 214 may have a
depth of one OFDM symbol and may be configurable to interleave a
block of encoded data. The interleaver configurations may comprise
a number of columns (NCol) and a number of rows (Nrow) and the
number of rows may be based on a number of coded bits per
subcarrier per stream (N.sub.BPSCS).
[0054] In some embodiments, for a minimum bandwidth unit having 54
data subcarriers for 256-point FFT processing, an example
interleaver configuration has 9 columns and a number of rows (Nrow)
equaling 3 times a number of coded bits per single subcarrier
(N.sub.BPSCS) (i.e., a 9.times.3 interleaver configuration). In
these embodiments, the number of subcarriers (Nsd) times the
modulation order (1-BPSK, 2-QPSK, etc.) is the number coded bits
per symbol. The number of coded bits per single carrier may be
computed by multiplying by the number of streams which then sets
the interleaver size (N.sub.ROW*N.sub.COL) where N.sub.ROW is the
y*N.sub.BPSCS.
[0055] In some embodiments, the longer-duration OFDM symbols may be
selected for larger delay spread environments (e.g., outdoors), and
standard-duration OFDM symbols may be selected for smaller
delay-spread environments (e.g., indoors). In these embodiments, a
more efficient cyclic-prefix (CP) may be used to overcome the
larger delay spread and may provide other benefits such as reduced
CP overhead and relaxed clock-timing accuracy, among other things.
The standard-duration OFDM symbols may have a symbol duration that
ranges from 3.6 micro-seconds (us) including a 400 nanosecond (ns)
short guard interval (e.g., for a 40 MHz channel) to 4 us including
an 800 ns guard interval (e.g., for a 20 MHz channel). The
longer-duration OFDM symbols may have a symbol duration is one of
either 2.times. or 4.times. the duration of the standard-duration
OFDM symbols.
[0056] FIG. 3 illustrates an HEW device in accordance with some
embodiments. HEW device 300 may be an HEW compliant device that may
be arranged to communicate with one or more other HEW devices, such
as HEW stations and/or a master station, as well as communicate
with legacy devices. HEW device 300 may be suitable for operating
as master station or an HEW station. In accordance with
embodiments, HEW device 300 may include, among other things,
physical layer (PHY) circuitry 302 and medium-access control layer
circuitry (MAC) 304. PHY 302 and MAC 304 may be HEW compliant
layers and may also be compliant with one or more legacy IEEE
802.11 standards. PHY 302 may be arranged to transmit HEW frames.
HEW device 300 may also include other processing circuitry 306 and
memory 308 configured to perform the various operations described
herein.
[0057] In accordance with some embodiments, the MAC 304 may be
arranged to contend for a wireless medium during a contention
period to receive control of the medium for the HEW control period
and configure an HEW frame. The PHY 302 may be arranged to transmit
the HEW frame as discussed above. The PHY 302 may also be arranged
to receive an HEW frame from HEW stations. MAC 304 may also be
arranged to perform transmitting and receiving operations through
the PHY 302. The PHY 302 may include circuitry for
modulation/demodulation, upconversion and/or downconversion,
filtering, amplification, etc. In some embodiments, the processing
circuitry 306 may include one or more processors. In some
embodiments, two or more antennas may be coupled to the physical
layer circuitry arranged for sending and receiving signals
including transmission of the HEW frame. The memory 308 may be
store information for configuring the processing circuitry 306 to
perform operations for configuring and transmitting HEW frames and
performing the various operations described herein.
[0058] In some embodiments, the HEW device 300 may be configured to
communicate using OFDM communication signals over a multicarrier
communication channel. In some embodiments, HEW device 300 may be
configured to receive signals in accordance with specific
communication standards, such as the Institute of Electrical and
Electronics Engineers (IEEE) standards including IEEE 802.11-2012,
802.11n-2009 and/or 802.11ac-2013 standards and/or proposed
specifications for WLANs including proposed HEW standards, although
the scope of the invention is not limited in this respect as they
may also be suitable to transmit and/or receive communications in
accordance with other techniques and standards. In some other
embodiments, HEW device 300 may be configured to receive signals
that were transmitted using one or more other modulation techniques
such as spread spectrum modulation (e.g., direct sequence code
division multiple access (DS-CDMA) and/or frequency hopping code
division multiple access (FH-CDMA)), time-division multiplexing
(TDM) modulation, and/or frequency-division multiplexing (FDM)
modulation, although the scope of the embodiments is not limited in
this respect.
[0059] In some embodiments, HEW device 300 may be part of a
portable wireless communication device, such as a personal digital
assistant (PDA), a laptop or portable computer with wireless
communication capability, a web tablet, a wireless telephone or
smartphone, a wireless headset, a pager, an instant messaging
device, a digital camera, an access point, a television, a medical
device (e.g., a heart rate monitor, a blood pressure monitor,
etc.), or other device that may receive and/or transmit information
wirelessly. In some embodiments, HEW device 300 may include one or
more of a keyboard, a display, a non-volatile memory port, multiple
antennas, a graphics processor, an application processor, speakers,
and other mobile device elements. The display may be an LCD screen
including a touch screen.
[0060] The antennas 301 of HEW device 300 may comprise one or more
directional or omnidirectional antennas, including, for example,
dipole antennas, monopole antennas, patch antennas, loop antennas,
microstrip antennas or other types of antennas suitable for
transmission of RF signals. In some multiple-input multiple-output
(MIMO) embodiments, the antennas 301 may be effectively separated
to take advantage of spatial diversity and the different channel
characteristics that may result between each of antennas and the
antennas of a transmitting station.
[0061] Although HEW device 300 is illustrated as having several
separate functional elements, one or more of the functional
elements may be combined and may be implemented by combinations of
software-configured elements, such as processing elements including
digital signal processors (DSPs), and/or other hardware elements.
For example, some elements may comprise one or more
microprocessors, DSPs, field-programmable gate arrays (FPGAs),
application specific integrated circuits (ASICs), radio-frequency
integrated circuits (RFICs) and combinations of various hardware
and logic circuitry for performing at least the functions described
herein. In some embodiments, the functional elements of HEW device
300 may refer to one or more processes operating on one or more
processing elements.
[0062] Embodiments may be implemented in one or a combination of
hardware, firmware and software. Embodiments may also be
implemented as instructions stored on a computer-readable storage
device, which may be read and executed by at least one processor to
perform the operations described herein. A computer-readable
storage device may include any non-transitory mechanism for storing
information in a form readable by a machine (e.g., a computer). For
example, a computer-readable storage device may include read-only
memory (ROM), random-access memory (RAM), magnetic disk storage
media, optical storage media, flash-memory devices, and other
storage devices and media. Some embodiments may include one or more
processors and may be configured with instructions stored on a
computer-readable storage device.
[0063] FIG. 4 is a procedure for communicating longer-duration OFDM
symbols using minimum bandwidth units in accordance with some
embodiments. Procedure 400 may be performed by an HEW device, such
as HEW station 104 or an HEW master device or station 102.
[0064] Operation 402 comprises configuring a block interleaver to
interleave blocks of encoded input data in accordance with one of a
plurality interleaver configurations determined for a subcarrier
allocation of a minimum bandwidth unit for longer-duration OFDM
symbols.
[0065] Operation 404 comprises processing symbols with either a
128-point FFT or a 256-point FFT to generate time-domain OFDMA
waveforms. For processing the longer-duration OFDM symbols with a
256-point FFT without code-rate exclusions, the predetermined
number of data subcarriers for the minimum bandwidth unit may be
limited to one of 48, 54 and 60 data subcarriers. For processing
the longer-duration OFDM symbols with a 128-point FFT without
code-rate exclusions, the number of data subcarriers for the
minimum bandwidth unit may be limited to one of 28 and 30 data
subcarriers. For processing the longer-duration OFDM symbols with
the 256-point FFT with a code-rate exclusion of 5/6 for 256-QAM,
the number of data subcarriers for the minimum bandwidth unit may
be limited to one of 48, 50, 54, 52, 54, 56, 60 and 62 data
subcarriers. For processing the longer-duration OFDM symbols with
the 128-point FFT with a code-rate exclusion of 5/6 for 256-QAM,
the number of data subcarriers for the minimum bandwidth unit may
be limited to one of 24, 26, 28 and 30 data subcarriers
[0066] Operation 406 comprises communicating the longer-duration
OFDM symbols (in the form of the time-domain OFDMA waveforms) on
channel resources comprising one or more minimum bandwidth units in
accordance with non-contention based communication technique. In
some embodiments, the longer-duration OFDM symbols may be
communicated during a control period (e.g., a TXOP) in accordance
with MU-MIMO technique.
[0067] In an example, a high-efficiency WLAN (HEW) communication
station (STA) comprising physical layer and medium access control
layer circuitry is configured to: communicate longer-duration
orthogonal frequency division multiplexed (OFDM) symbols on channel
resources in accordance with an orthogonal frequency division
multiple access (OFDMA) technique, the channel resources comprising
one or more minimum bandwidth units, each minimum bandwidth unit
having a predetermined number of data subcarriers; and configure
the minimum bandwidth units in accordance with one of a plurality
of subcarrier allocations for one of a plurality of interleaver
configurations for communication of the longer-duration OFDM
symbols. The longer-duration OFDM symbols have symbol duration that
is either 2.times. or 4.times. a standard OFDM symbol duration.
[0068] In another example, the station is configured to process the
longer-duration OFDM symbols with a fast-Fourier Transform (FFT).
For processing the longer-duration OFDM symbols with a 256-point
FFT without code-rate exclusions, the predetermined number of data
subcarriers for the minimum bandwidth unit is to be of 48, 54 or 60
data subcarriers. For processing the longer-duration OFDM symbols
with a 128-point FFT without code-rate exclusions, the number of
data subcarriers for the minimum bandwidth unit is to be of 28 or
30 data subcarriers. For processing the longer-duration OFDM
symbols with the 256-point FFT with a code-rate exclusion of 5/6
for 256-QAM, the number of data subcarriers for the minimum
bandwidth unit is to be of 48, 50, 54, 52, 54, 56, 60 or 62 data
subcarriers. For processing the longer-duration OFDM symbols with
the 128-point FFT with a code-rate exclusion of 5/6 for 256-QAM,
the number of data subcarriers for the minimum bandwidth unit is to
be of 24, 26, 28 or 30 data subcarriers.
[0069] In another example, the station is further configured to
concurrently communicate using up to four of the minimum bandwidth
units over channels of 20 MHz or 40 MHz during a control period in
accordance with the OFDMA technique.
[0070] In another example, for a minimum bandwidth unit having 54
data subcarriers for 256-point FFT processing, the subcarrier
allocation comprises 256 total subcarriers including: 54 data
subcarriers and 3 pilot subcarriers for each of the four minimum
bandwidth units used for communicating within either channels of 20
MHz or 40 MHz, 2-4 null-subcarriers at DC, and 12-13 guard
subcarriers at each band edge.
[0071] In another example, the PHY circuitry includes a block
interleaver having a depth of one OFDM symbol. The block
interleaver may be configurable to interleave a block of encoded
data, and the interleaver configurations may comprise a number of
columns and a number of rows, the number of rows based on a number
of coded bits per subcarrier per stream.
[0072] In another example, for a minimum bandwidth unit having 54
data subcarriers for 256-point FFT processing, the interleaver
configuration has 9 columns and a number of rows equaling 3 times a
number of coded bits per single subcarrier.
[0073] In another example, the communication station further
comprises: an encoder configured to encode input data prior to
interleaving in accordance with one of a plurality of code rates;
and a constellation mapper to map the encoded data after the
interleaving to a QAM constellation. The encoder and mapper operate
in accordance with one of a plurality of predetermined modulation
and coding scheme (MCS) combinations for the subcarrier allocation.
The plurality of predetermined MCS combinations for the subcarrier
allocation are restricted to an integer number of coded bits per
OFDM symbol (Ncbps) and an integer number of data bits per OFDM
symbol (Ndbps).
[0074] In another example, the longer-duration OFDM symbols are to
be selected for larger delay spread environments, and
standard-duration OFDM symbols are to be selected for smaller
delay-spread environments.
[0075] In another example, the standard-duration OFDM symbols have
a symbol duration that ranges from 3.6 micro-seconds (us) including
a 400 nanosecond (ns) short guard interval to 4 us including an 800
ns guard interval, and the longer-duration OFDM symbols have a
symbol duration is one of either 2.times. or 4.times. the duration
of the standard-duration OFDM symbols.
[0076] In another example, the communication station further
comprises one or more processors and memory, and the physical layer
circuitry includes a transceiver.
[0077] In another example, the communication station further
comprises two antennas coupled to the transceiver.
[0078] In another example, a method performed by a high-efficiency
WLAN (HEW) communication station (STA) comprises: communicating
longer-duration orthogonal frequency division multiplexed (OFDM)
symbols on channel resources in accordance with an orthogonal
frequency division multiple access (OFDMA) technique, the channel
resources comprising one or more minimum bandwidth units, each
minimum bandwidth unit having a predetermined number of data
subcarriers; and configuring the minimum bandwidth units in
accordance with one of a plurality of subcarrier allocations for
one of a plurality of interleaver configurations for communication
of the longer-duration OFDM symbols. The longer-duration OFDM
symbols have symbol duration that is either 2.times. or 4.times. a
standard OFDM symbol duration.
[0079] In another example, the method further comprises processing
the longer-duration OFDM symbols with a fast-Fourier Transform
(FFT). For processing the longer-duration OFDM symbols with a
256-point FFT without code-rate exclusions, the predetermined
number of data subcarriers for the minimum bandwidth unit is to be
of 48, 54 or 60 data subcarriers. For processing the
longer-duration OFDM symbols with a 128-point FFT without code-rate
exclusions, the number of data subcarriers for the minimum
bandwidth unit is to be of 28 or 30 data subcarriers.
[0080] In another example, for processing the longer-duration OFDM
symbols with the 256-point FFT with a code-rate exclusion of 5/6
for 256-QAM, the number of data subcarriers for the minimum
bandwidth unit is to be of 48, 50, 54, 52, 54, 56, 60 or 62 data
subcarriers, and for processing the longer-duration OFDM symbols
with the 128-point FFT with a code-rate exclusion of 5/6 for
256-QAM, the number of data subcarriers for the minimum bandwidth
unit is to be of 24, 26, 28 or 30 data subcarriers.
[0081] In another example, the method comprises selecting the
longer-duration OFDM symbols for larger delay spread environments,
and selecting the standard-duration OFDM symbols for smaller
delay-spread environments.
[0082] In another example, a non-transitory computer-readable
storage medium stores instructions for execution by one or more
processors to perform operations to configure a high-efficiency
WLAN (HEW) communication station (STA) to: communicate
longer-duration orthogonal frequency division multiplexed (OFDM)
symbols on channel resources in accordance with an orthogonal
frequency division multiple access (OFDMA) technique, the channel
resources comprising one or more minimum bandwidth units, each
minimum bandwidth unit having a predetermined number of data
subcarriers; and configure the minimum bandwidth units in
accordance with one of a plurality of subcarrier allocations for
one of a plurality of interleaver configurations for communication
of the longer-duration OFDM symbols. The longer-duration OFDM
symbols have symbol duration that is either 2.times. or 4.times. a
standard OFDM symbol duration.
[0083] The Abstract is provided to comply with 37 C.F.R. Section
1.72(b) requiring an abstract that will allow the reader to
ascertain the nature and gist of the technical disclosure. It is
submitted with the understanding that it will not be used to limit
or interpret the scope or meaning of the claims. The following
claims are hereby incorporated into the detailed description, with
each claim standing on its own as a separate embodiment.
* * * * *