U.S. patent number 9,271,241 [Application Number 14/304,041] was granted by the patent office on 2016-02-23 for access point and methods for distinguishing hew physical layer packets with backwards compatibility.
This patent grant is currently assigned to Intel IP Corporation. The grantee listed for this patent is Intel IP Corporation. Invention is credited to Shahrnaz Azizi, Thomas J. Kenney, Eldad Perahia.
United States Patent |
9,271,241 |
Kenney , et al. |
February 23, 2016 |
Access point and methods for distinguishing HEW physical layer
packets with backwards compatibility
Abstract
Embodiments of a system and methods for distinguishing
high-efficiency Wi-Fi (HEW) packets from legacy packets are
generally described herein. In some embodiments, an access point
may select a value for the length field of a legacy signal field
(L-SIG) that is non-divisible by three for communicating with HEW
stations and may select a value for the length field that is
divisible by three for communicating with legacy stations. In some
embodiments, the access point may select a phase rotation for
application to the BPSK modulation of at least one of the first and
second symbols of a subsequent signal field to distinguish a
high-throughput (HT) PPDU, a very-high throughput (VHT) PPDU and an
HEW PPDU.
Inventors: |
Kenney; Thomas J. (Portland,
OR), Perahia; Eldad (Portland, OR), Azizi; Shahrnaz
(Cupertino, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Intel IP Corporation |
Santa Clara |
CA |
US |
|
|
Assignee: |
Intel IP Corporation (Santa
Clara, CA)
|
Family
ID: |
53173243 |
Appl.
No.: |
14/304,041 |
Filed: |
June 13, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150139205 A1 |
May 21, 2015 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
61906059 |
Nov 19, 2013 |
|
|
|
|
61976951 |
Apr 8, 2014 |
|
|
|
|
61973376 |
Apr 1, 2014 |
|
|
|
|
61986256 |
Apr 30, 2014 |
|
|
|
|
61986250 |
Apr 30, 2014 |
|
|
|
|
61991730 |
May 12, 2014 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
52/241 (20130101); H04L 5/0053 (20130101); H04W
52/267 (20130101); H04B 7/0452 (20130101); H04W
28/06 (20130101); H04W 16/14 (20130101); H04W
52/42 (20130101); H04L 5/0091 (20130101); H04W
74/006 (20130101); H04W 52/346 (20130101); H04W
56/00 (20130101); H04W 84/12 (20130101); H04W
52/146 (20130101) |
Current International
Class: |
H04W
4/00 (20090101); H04W 52/26 (20090101); H04W
16/14 (20090101); H04W 28/06 (20090101); H04B
7/04 (20060101); H04W 52/24 (20090101); H04W
52/42 (20090101); H04W 74/00 (20090101); H04W
52/34 (20090101); H04W 84/12 (20090101); H04W
56/00 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Harper; Kevin C
Attorney, Agent or Firm: Schwegman Lundberg & Woessner,
P.A.
Parent Case Text
PRIORITY CLAIM
This application claims priority under 35 U.S.C. 119(e) to U.S.
Provisional Patent Application Ser. No. 61/906,059 filed Nov. 19,
2013 U.S. Provisional Patent Application Ser. No. 61/973,376, filed
Apr. 1, 2014, U.S. Provisional Patent Application Ser. No.
61/976,951 filed Apr. 8, 2014, U.S. Provisional Patent Application
Ser. No. 61/986,256, filed Apr. 30, 2014, U.S. Provisional Patent
Application Ser. No. 61/986,250, filed Apr. 30, 2014, and to U.S.
Provisional Patent Application Ser. No. 61/991,730, filed May 12,
2014, each of which is incorporated herein by reference in its
entirety.
Claims
What is claimed is:
1. An access point (AP) arranged for communicating with a plurality
of stations (STAs) including high-efficiency Wi-Fi (HEW) stations
and legacy stations, the access point comprising hardware
processing circuitry and physical layer (PHY) circuitry to:
configure a packet protocol data unit (PPDU) comprising a legacy
signal field (L-SIG) following legacy training fields, the L-SIG
including at least a length field and a rate field; select a value
for the length field that is not-divisible by three for
communicating with the HEW stations; and select a value for the
length field that is divisible by three for communicating with at
least some of the legacy stations.
2. The access point of claim 1 wherein the access point is further
arranged to configure the L-SIG with a valid parity bit when the
length field is selected to be divisible by three and when the
length field is selected to be non-divisible by three.
3. The access point of claim 2 wherein, the access point is further
arranged to configure the PPDU to include a subsequent signal field
following the L-SIG, the subsequent signal field having first and
second symbols that have BPSK modulation, and wherein the access
point is further arranged to select a phase rotation for
application to the BPSK modulation of at least one of the first and
second symbols of the subsequent signal field to distinguish a
high-throughput (HT) PPDU, a very-high throughput (VHT) PPDU and an
HEW PPDU.
4. The access point of claim 3 wherein for communicating with the
HEW stations, the subsequent signal field is an HEW signal field
(HEW-SIG) and the access point is arranged to apply a ninety-degree
phase rotation to the BPSK modulation of the first symbol of the
HEW-SIG and refrain from applying a ninety-degree phase rotation to
the BPSK modulation of the second symbol of the HEW-SIG.
5. The access point of claim 4 wherein for communicating with VHT
stations, the subsequent signal field is an VHT signal field
(VHT-SIG) and the access point is arranged to apply a ninety-degree
phase rotation to the BPSK modulation of the second symbol of the
VHT-SIG and refrain from applying a ninety-degree phase rotation to
the BPSK modulation of the first symbol of the VHT-SIG, wherein for
communicating with HT stations, the subsequent signal field is an
HT signal field (HT-SIG) and the access point is arranged to apply
a ninety-degree phase rotation to the BPSK modulation of both the
first symbol and the second symbol of the HT-SIG, and wherein for
communicating with non-HT stations, the access point is configured
to refrain from including the subsequent signal field following the
L-SIG.
6. The access point of claim 5 wherein for communicating with the
HEW stations and some legacy stations including HT stations and VHT
stations, the access point is arranged to select a value for the
rate field to cause the non-HT stations to defer transmissions.
7. The access point of claim 1 wherein the access point is
configured to multiply a ceiling function by three and subtract
either two or one to calculate the value for the length field for
the HEW stations, and wherein the access point is configured to
multiply the ceiling function by three and subtract three to
calculate the value for the length field for non-HEW stations.
8. The access point of claim 4 wherein for communicating with HEW
stations, the access point is further configured to: configure the
PPDU as an HEW PPDU to include a number of long-training fields
(LTFs), the number of LTFs being based on a maximum number of
streams communicated over a link; contend for a wireless medium
during a contention period to receive control of the medium for an
HEW control period; and transmit the HEW PPDU during the HEW
control period, wherein during the HEW control period, the access
point operates as a master station having exclusive use of the
wireless medium for communication of data with a plurality of
scheduled HEW stations in accordance with a non-contention based
scheduled orthogonal frequency division multiple access (OFDMA)
technique in accordance with signaling information indicated in the
HEW-SIG, wherein the scheduled OFDMA technique is one of an uplink
OFDMA technique, a downlink OFDMA technique or a multi-user
multiple-input multiple-output (MU-MIMO) technique.
9. The access point of claim 8 wherein for the HEW PPDU, each data
field is associated with either a single user (SU) link or a
multi-user (MU) link, each link configurable to provide multiple
streams of data, and wherein the links of the HEW PPDU are
configurable to have a bandwidth of one of 20 MHz, 40 MHz, 80 MHz
or 160 MHz.
10. An access point arranged for communicating with a plurality of
stations including high-efficiency Wi-Fi (HEW) stations and legacy
stations, the access point comprising hardware processing circuitry
and physical layer (PHY) circuitry to configure a packet protocol
data unit (PPDU) comprising: a legacy signal field (L-SIG)
following one or more legacy training fields; and one or more
fields following the L-SIG including a subsequent signal field, the
subsequent signal field having first and second symbols that have
BPSK modulation, wherein the access point is further arranged to
select a phase rotation for application to the BPSK modulation of
at least one of the first and second symbols of the subsequent
signal field to distinguish a high-throughput (HT) PPDU, a
very-high throughput (VHT) PPDU and an HEW PPDU.
11. The access point of claim 10 wherein for communicating with the
HEW stations, the subsequent signal field is an HEW signal field
(HEW-SIG) and the access point is arranged to apply a ninety-degree
phase rotation to the BPSK modulation of the first symbol of the
HEW-SIG and refrain from applying a ninety-degree phase rotation to
the BPSK modulation of the second symbol of the HEW-SIG.
12. The access point of claim 11 wherein for communicating with VHT
stations, the subsequent signal field is an VHT signal field
(VHT-SIG) and the access point is arranged to apply a ninety-degree
phase rotation to the BPSK modulation of the second symbol of the
VHT-SIG and refrain from applying a ninety-degree phase rotation to
the BPSK modulation of the first symbol of the VHT-SIG, wherein for
communicating with HT stations, the subsequent signal field is an
HT signal field (HT-SIG) and the access point is arranged to apply
a ninety-degree phase rotation to the BPSK modulation of both the
first symbol and the second symbol of the HT-SIG, and wherein for
communicating with non-HT stations, the access point is configured
to refrain from including the subsequent signal field following the
L-SIG.
13. A high-efficiency Wi-Fi (HEW) station arranged to distinguish
an HEW packet protocol data unit (PPDU) from a non-HEW PPDU, the
HEW station comprising hardware processing circuitry and physical
layer (PHY) circuitry configured to: receive a legacy signal field
(L-SIG) following legacy training fields, the L-SIG including at
least a length field and a rate field; determine whether a value
for the length field is divisible by three; verify a parity bit of
the L-SIG; identify the PPDU as an HEW PPDU when the value in the
length field is not divisible three and the parity bit is verified;
and identify the PPDU as a non-HEW PPDU when the value in the
length field is divisible three and the parity bit is verified.
14. The HEW station of claim 12 wherein the HEW station is further
configured to: decode subsequent fields of the PPDU when the PPDU
identified as an HEW PPDU, and refrain from decoding subsequent
fields of the PPDU when the PPDU is identified as a non-HEW
PPDU.
15. A high-efficiency Wi-Fi (HEW) station arranged to distinguish
an HEW packet protocol data unit (PPDU) from a non-HEW PPDU, the
HEW station comprising hardware processing circuitry and physical
layer (PHY) circuitry configured to: receive a legacy signal field
(L-SIG) following legacy training fields, the L-SIG including at
least a length field and a rate field; receive a subsequent signal
field, the subsequent signal field having first and second symbols
that have BPSK modulation, determine whether the PPDU is a
high-throughput (HT) PPDU, a very-high throughput (VHT) PPDU or an
HEW PPDU based on the phase rotation applied to the BPSK modulation
of at least one of the first and second symbols of the subsequent
signal field, wherein for an HEW PPDU, a ninety-degree phase
rotation is applied to the BPSK modulation of the first symbol and
no phase rotation is applied to the BPSK modulation of the second
symbol of the subsequent signal field.
16. The HEW station of claim 15 wherein when an HEW PPDU is
determined, the subsequent signal field is an HEW-SIG, and wherein
the HEW station is further configured to communicate with an HEW
master station in accordance with a scheduled OFDMA technique based
on information received in the HEW-SIG.
17. A method performed by an access point for communicating with a
plurality of stations including high-efficiency Wi-Fi (HEW)
stations and legacy stations, the method comprising: configuring a
packet protocol data unit (PPDU) comprising a legacy signal field
(L-SIG) following legacy training fields, the L-SIG including at
least a length field and a rate field; selecting a value for the
length field that is not-divisible by three for communicating with
the HEW stations; and either selecting a value for the length field
that is divisible by three for communicating with at least some of
the legacy stations; or selecting a phase rotation for application
to BPSK modulation of at least one of first and second symbols of a
subsequent signal field to distinguish a high-throughput (HT) PPDU,
a very-high throughput (VHT) PPDU and an HEW PPDU.
18. The method of claim 17 further comprising: configuring the PPDU
as an HEW PPDU to include a number of long-training fields (LTFs),
the number of LTFs being based on a maximum number of streams
communicated over a link; contending for a wireless medium during a
contention period to receive control of the medium for an HEW
control period; and transmitting the HEW PPDU during the HEW
control period, wherein during the HEW control period, the access
point operates as a master station having exclusive use of the
wireless medium for communication of data with a plurality of
scheduled HEW stations in accordance with a non-contention based
scheduled orthogonal frequency division multiple access (OFDMA)
technique in accordance with signaling information indicated in the
HEW-SIG, wherein the scheduled OFDMA technique is one of an uplink
OFDMA technique, a downlink OFDMA technique or a multi-user
multiple-input multiple-output (MU-MIMO) technique.
19. A non-transitory computer-readable storage medium that stores
instructions for execution by one or more processors of an access
point to perform operations for communicating with a plurality of
stations including high-efficiency Wi-Fi (HEW) stations and legacy
stations, the operations to configure the access point to:
configure a packet protocol data unit (PPDU) comprising a legacy
signal field (L-SIG) following legacy training fields, the L-SIG
including at least a length field and a rate field; select a value
for the length field that is not-divisible by three for
communicating with the HEW stations; and either select a value for
the length field that is divisible by three for communicating with
at least some of the legacy stations; or select a phase rotation
for application to BPSK modulation of at least one of first and
second symbols of a subsequent signal field to distinguish a
high-throughput (HT) PPDU, a very-high throughput (VHT) PPDU and an
HEW PPDU.
20. The non-transitory computer-readable storage medium of claim 19
wherein the operations further configure the access point to:
configure the PPDU as an HEW PPDU to include a number of
long-training fields (LTFs), the number of LTFs being based on a
maximum number of streams communicated over a link; contend for a
wireless medium during a contention period to receive control of
the medium for an HEW control period; and transmit the HEW PPDU
during the HEW control period, wherein during the HEW control
period, the access point operates as a master station having
exclusive use of the wireless medium for communication of data with
a plurality of scheduled HEW stations in accordance with a
non-contention based scheduled orthogonal frequency division
multiple access (OFDMA) technique in accordance with signaling
information indicated in the HEW-SIG, wherein the scheduled OFDMA
technique is one of an uplink OFDMA technique, a downlink OFDMA
technique or a multi-user multiple-input multiple-output (MU-MIMO)
technique.
Description
TECHNICAL FIELD
Embodiments pertain to wireless networks. Some embodiments relate
to Wi-Fi networks and networks operating in accordance with the
IEEE 802.11 standards. Some embodiments relate to high-efficiency
wireless or high-efficiency Wi-Fi (HEW) communications in
accordance with the IEEE 802.11ax draft standard.
BACKGROUND
IEEE 802.11ax (High Efficiency Wi-Fi (HEW)) is the successor to
IEEE 802.11ac standard and is intended to increase the efficiency
of wireless local-area networks (WLANs). HEW's goal is to provide
up to four-times or more the throughput of IEEE 802.11ac standard.
HEW may be particularly suitable in high-density hotspot and
cellular offloading scenarios with many devices competing for the
wireless medium may have low to moderate data rate requirements.
The Wi-Fi standards have evolved from IEEE 802.11b to IEEE
802.11g/a to IEEE 802.11n to IEEE 802.11ac and now to IEEE
802.11ax. In each evolution of these standards, there were
mechanisms to afford coexistence with the previous standard. For
HEW, the same requirement exists for coexistence with legacy
devices and systems.
Thus there are general needs for systems and methods that that
allow HEW devices to coexist with legacy devices that operate in
accordance with prior versions of the standards. There are general
needs for systems and methods that that allow HEW communications to
be distinguished from legacy communications and provide coexistence
with legacy devices and systems.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a wireless network in accordance with some
embodiments;
FIG. 2A illustrates a non-HT (high-throughput) format packet
protocol data unit (PPDU) in accordance with some embodiments;
FIG. 2B illustrates a HT mixed-format PPDU in accordance with some
embodiments;
FIG. 2C illustrates a VHT (very-high throughput) format PPDU in
accordance with some embodiments;
FIG. 2D illustrates a HEW format PPDU in accordance with some
embodiments;
FIG. 2E illustrates a HEW format PPDU for single-stream
transmissions in accordance with some embodiments;
FIG. 2F illustrates a HEW format PPDU for multi-stream
transmissions with transmit beamforming in accordance with some
alternate embodiments;
FIG. 2G illustrates a HEW format PPDU for multi-stream
transmissions without transmit beamforming in accordance with some
embodiments;
FIG. 3 illustrates signal field constellations in accordance with
some embodiments;
FIG. 4 is a procedure for configuring a PPDU for communicating with
HEW stations and legacy stations in accordance with some
embodiments; and
FIG. 5 is a block diagram of an HEW device in accordance with some
embodiments.
DETAILED DESCRIPTION
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.
Embodiments disclosed herein provide for coexistence of High
Efficiency Wi-Fi (HEW) devices with existing legacy Wi-Fi devices.
Legacy devices may refer to devices operating in accordance with
previous Wi-Fi standards and/or amendments such as IEEE 802.11g/a,
IEEE 802.11n or IEEE 802.11ac. HEW is a recent activity in IEEE to
evolve the Wi-Fi standard. It has several target use cases, with a
large focus on improving system efficiency in dense deployed
networks. Since it is an evolution of the previous standards and
needs to coexist with the legacy systems, a technique to identify
each transmission as either a HEW packet or a legacy packet is
needed. Additionally, it would be advantageous if the technique to
identify the HEW transmissions could at the same time defer legacy
devices. Finally, since one focus on HEW is efficiency, another
aspect is to have a mechanism which accomplishes these things
without adding any additional overhead to each transmission and
possibly reducing the overhead.
Embodiments disclosed herein provide techniques to notify HEW
devices that an HEW compliant transmission is occurring while also
deferring legacy devices and doing so with little or no additional
overhead from what is done in legacy transmissions and in some
embodiments, less overhead. Since HEW is an evolution of the
existing Wi-Fi standards, there have not been any previous
solutions to address this need.
In some embodiments, the preamble portion of the packet has been
increased and new fields added with various modulation formats so
that the new releases could be identified. Some embodiments
described herein are configured to defer legacy devices using the
legacy signal field (L-SIG) and build upon the coexistence approach
adopted in IEEE 802.11n and IEEE 802.11ac. In those systems, the
rate field of the L-SIG was fixed to a set known value and the
length was set to a length that would defer those devices beyond
the transmission of an IEEE 802.11n or an IEEE 802.11ac
transmission.
In some embodiments disclosed herein, the same fixed value in the
rate field may be used although this is not a requirement. In some
embodiments, the length field of the L-SIG may be computed
differently from what is done in an IEEE 802.11n/ac system to allow
deferral of legacy systems and identification of an HEW
transmission. These embodiments are described in more detail
below.
Following the L-SIG in an IEEE 802.11n/ac transmission are
additional SIG fields. In IEEE 802.11n/ac systems, these SIG fields
follow directly after the L-SIG and are phase rotated in order to
allow identification. In the embodiments disclosed herein, an HEW
signal field may also be used if needed and may use a modified
legacy length value allowing for several preamble designs and
potentially several payloads to support not only single user (SU)
packets to multi-user (MU) packets like multi-user multiple-input
multiple-output (MU-MIMO) or orthogonal frequency division multiple
access (OFDMA). In these embodiments that use uplink MU-MIMO or
uplink OFDMA, an access point (AP) may operate as a master station
which would have mechanisms to contend and hold the medium. Uplink
transmissions from scheduled HEW stations may immediately follow.
In those cases, the AP may signal the specific devices that are
targeted for uplink transmission the transmission parameters.
Therefore, each device that transmits in the uplink would not need
to send any additional configuration parameters and therefore does
not need an additional SIG field in the preamble during their
transmission.
Embodiments disclosed herein also allow legacy devices that missed
the initial AP transmission (e.g., when returning from a power save
mode) to detect the signal and properly defer irrespective of them
being an IEEE 802.11a, an IEEE 802.11n or an IEEE 802.11ac device.
In these embodiments, a new signal field modulation format is
disclosed in which the first symbol is set as rotated BPSK (i.e.,
rotated by 90 degrees) and then the second would be BPSK (i.e., not
rotated). These embodiments are described in more detail below.
FIG. 1 illustrates a wireless network in accordance with some
embodiments. Wireless network 100 may include a master station
(STA) 102, a plurality of HEW stations 104 (i.e., 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 some embodiments, the master station
102 may be an access point (AP), although the scope of the
embodiments is not limited in this respect.
Legacy stations 106 may include, for example, non-HT stations 108
(e.g., IEEE 802.11a/g stations), HT stations 110 (e.g., IEEE
802.11n stations), and VHT stations 112 (e.g., IEEE 802.11ac
stations). Embodiments disclosed herein allow HEW stations 104 to
distinguish transmissions (e.g., packets such as packet protocol
data units (PPDUs)) from transmissions of legacy stations 106 and
cause legacy stations 106 to at least defer their transmissions
during HEW transmissions providing backwards compatibility. In some
embodiments, the length field of the legacy signal field (L-SIG)
may be used to cause some legacy stations 106 to defer
transmissions. In some embodiments, the length field of the L-SIG
may be used to distinguish HEW PPDUs from non-HEW PPDUs. In some
embodiments, a phase rotation applied to a subsequent or additional
signal field (an HT-SIG, a VHT SIG or an HEW SIG) may be used to
distinguish HT PPDUs, VHT PPDUs and HEW PPDUs. In some embodiments,
the rate field of the L-SIG may be used to cause some legacy
stations 106 to defer transmissions and distinguish non-HT
transmissions from HT, VHT and HEW transmissions. These embodiments
are discussed in more detail below.
In accordance with embodiments, the master station 102 may include
hardware processing circuitry including physical layer (PHY) and
medium-access control layer (MAC) circuitry which 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 transmit an HEW master-sync transmission at the
beginning of the HEW control period. During the HEW control period,
the HEW stations 104 may communicate with the master station 102 in
accordance with a non-contention based multiple-access technique
(e.g., an OFDMA technique or MU-MIMO 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 multiple-access technique. During the HEW
control period, legacy stations 106 refrain from communicating and
defer their transmissions. In some embodiments, the HEW master-sync
transmission may be referred to as an HEW control and schedule
transmission.
In accordance with some embodiments, the master-sync transmission
may include a multi-device HEW preamble arranged to signal and
identify data fields for a plurality of scheduled HEW stations 104.
The master station 102 may further be arranged to transmit (in the
downlink direction) and/or receive (in the uplink direction) one or
more of the data fields to/from the scheduled HEW stations 104
during the HEW control period. In these embodiments, the master
station 102 may include training fields in the multi-device HEW
preamble to allow each of the scheduled HEW stations 104 to perform
an initial channel estimate.
In accordance with some embodiments, an HEW station 104 may be an
IEEE 802.11ax configured station (STA) that is configured for HEW
operation. An HEW station 104 may be configured to communicate with
a master station 102 in accordance with a scheduled multiple access
technique during the HEW control period and may be configured to
receive and decode the multi-device HEW preamble of an HEW frame or
PPDU. An HEW station 104 may also be configured to decode an
indicated data field received by the master station 102 during the
HEW control period. Examples of HEW PPDUs are illustrated in FIGS.
2D through 2G discussed below.
In accordance with some embodiments, the master station 102 may be
arranged to select a number of HEW long-training fields (LTFs) to
be included in the multi-device HEW preamble of an HEW frame. The
HEW frame may comprise a plurality of links for transmission of a
plurality of data streams. The master station 102 may also transmit
the selected number of LTFs sequentially as part of the
multi-device HEW preamble. The master station 102 may also
transmit/receive a plurality of data fields sequentially to/from
each of a plurality of scheduled HEW stations 104. The data fields
may be part of the HEW frame. Each data field may correspond to one
of the links and may comprise one or more data streams. In some
embodiments, the data fields may be separate packets. The master
station 102 may also be arranged receive packets from HEW stations
104 in the uplink direction during the HEW control period.
In some embodiments, the selection of the number of LTFs to be
included in the multi-device HEW preamble may be based on a maximum
number of streams to be transmitted on a single link. In some
embodiments, the selection of the number of LTFs to be included in
the multi-device HEW preamble may be based on a scheduled HEW
station 104 with a greatest channel estimation need (e.g., the
scheduled HEW station 104 receiving the greatest number of streams
on a single link). In some embodiments, the selection of the number
of LTFs to be included in the multi-device HEW preamble may be
based on the sum of greatest number of streams on each single link
that scheduled HEW stations 104 would receive. In some embodiments,
the number of LTFs to be included in the multi-device HEW preamble
may be predetermined. In these embodiments, the number of LTFs to
be included in the multi-device HEW preamble may be based on the
maximum number of streams that can be transmitted on a single
link.
In some embodiments, the master station 102 may be arranged to
configure the multi-device HEW preamble include an HEW control
signal field (i.e., HEW SIG-B) to identify and signal each of the
data fields of the HEW frame. In these embodiments, a single HEW
preamble is included in an HEW frame, which is unlike conventional
techniques which include a preamble for each link.
FIG. 2A illustrates a non-HT format PPDU in accordance with some
embodiments. The non-HT format PPDU may be used for communicating
with non-HT stations 108 (FIG. 1), which may include stations
configured to communicate in accordance with an IEEE 802.11a or
IEEE 802.11g standard. In IEEE 802.11a/g, the packet structure
comprises a Legacy Short Training Field (L-STF) 202, a Legacy Long
Training Field (L-LTF) 204 and the L-SIG 206 which made up the
preamble. The preamble is followed by a data field 208. The L-SIG
206 provides information about the data field 208 including the
coding and modulation (rate) and the length.
FIG. 2B illustrates a HT mixed-format PPDU in accordance with some
embodiments. The HT mixed-format PPDU may be used for communicating
with HT stations 110 (FIG. 1), which may include stations
configured to communicate in accordance with an IEEE 802.11n
standard. In IEEE 802.11n, the packet structure allows the IEEE
802.11n devices to coexist with IEEE 802.11a/g devices and
therefore included the legacy preamble portion of the packet to be
used at the beginning of the transmission. The IEEE 802.11n
transmission sets the rate field of the L-SIG 206 to a fixed rate
and the length field is set to extend for the full duration of the
IEEE 802.11n packet. Following the legacy portion of the preamble,
the IEEE 802.11n preamble includes a HT-SIG 212 for the IEEE
802.11n and includes additional configuration information for those
devices. The HT-SIG 212 uses rotated binary phase-shift keying
(BPSK) in both symbols of the HT-SIG 212 so that IEEE 802.11n
devices can distinguish it from non-rotated BPSK data 208 of an
IEEE 802.11a/g transmission and allows those devices to detect the
existence of an IEEE 802.11n packet. Thus, IEEE 802.11a/g devices
are able to recognize the legacy portion of the preamble, but not
the portion following the legacy portion and may defer based on the
configuration parameters in the L-SIG 206 of the HT mixed-format
PPDU of FIG. 2B assuring coexistence.
FIG. 2C illustrates a VHT format PPDU in accordance with some
embodiments. The VHT format PPDU may be used for communicating with
VHT stations 112 (FIG. 1), which may include stations configured to
communicate in accordance with an IEEE 802.11ac standard. In
802.11ac, the packet also starts with the legacy portion of the
preamble which is then followed by a VHT-SIG 222 to provide
additional configuration parameters for the VHT data field. The
IEEE 802.11a/g devices recognize the legacy portion of the packet
but would decode the rest of the packet correctly and thus defer
from transmission for the full length based on the legacy
rate/length fields.
IEEE 802.11ac devices are also able to discern IEEE 802.11ac
packets from other legacy (IEEE 802.11a/g and IEEE 802.11n)
packets. In the discussion above regarding IEEE 802.11n, the HT-SIG
field 212 (FIG. 2B) following the L-SIG 206 is modulated using BPSK
as in the L-SIG 206, but it is rotated 90 degrees. This modulation
format may be used by an IEEE 802.11n device to detect those
packets and identify them as IEEE 802.11n packets. For IEEE
802.11ac devices to detect IEEE 802.11ac packets, the VHT-SIG 222
(FIG. 2C) is normal BPSK for the first symbol of the VHT-SIG 222
and is rotated 90 degrees for the second symbol. This allows for
the identification of IEEE 802.11ac packets by IEEE 802.11ac
devices, but demodulation of the VHT-SIG 222 may not be possible by
the IEEE 802.11n devices. In those cases the IEEE 802.11n device
will defer based on the L-SIG 206.
FIGS. 2D-2G illustrate HEW format PPDUs in accordance with various
embodiments. The HEW formats PPDU of FIGS. 2D-2G may be used for
communicating with HEW stations 104 (FIG. 1), which may include
stations configured to communicate in accordance with an IEEE
802.11x standard. In accordance with embodiments, the master
station 102 (FIG. 1) may configure a PPDU comprising a legacy
signal field (L-SIG) 206 following legacy training fields (i.e.,
L-STF 202 and L-LTF 204).
In some embodiments, the L-SIG 206 may be configured to include at
least a length field and a rate field. The master station 102 may
select a value for the length field that is non-divisible by three
for communicating with the HEW stations 104 and may select a value
for the length field that is divisible by three for communicating
with at least some legacy stations 106. In these embodiments, when
the length field is not divisible by three, at least some legacy
stations 106 (i.e., HT stations 110 and VHT stations 112) would
determine that the length field value in the L-SIG 206 is invalid
and will properly defer their transmissions. When the length field
is not divisible by three, HEW stations 104 may be configured to
identify the PPDU as an HEW PPDU and decode one or more of the
fields that follow the L-SIG 206.
In some embodiments, the master station 102 is further arranged to
configure the L-SIG 206 with a valid parity bit (i.e., the L-SIG
parity bit) when the length field is selected to be divisible by
three and when the length field is selected to be non-divisible by
three. In these embodiments, the L-SIG may always be configured
with a valid parity bit. In these embodiments, when a valid L-SIG
parity bit is indicated, the physical layer (PHY) of a device may
maintain a busy indication for the predicted duration of the PPDU.
Thus legacy stations 106 will defer for the value indicated by the
length (L_LENGTH) field in the L-SIG 206 even if the value is
invalid (i.e., not divisible by three) as long as the parity bit is
valid.
In some embodiments, the master station 102 may multiply a ceiling
function by three and subtract either two or one to calculate the
value for the length field for the HEW PPDUs. By multiplying the
ceiling function by three and then subtracting two or one assures
that the length field is not divisible by three. The master station
102 may multiply the ceiling function by three and subtract three
to calculate the value for the length field for HT and VHT PPDUs.
By multiplying the ceiling function by three and then subtracting
three assures that the length field is divisible by three. These
embodiments are discussed in more detail below.
In some embodiments, the length calculation used to populate the
L-SIG for 0.11ac packets is give as (L_LENGTH):
.function..times..times..times..times. ##EQU00001## .times.
##EQU00001.2##
In the above equations, the T variable is the time for the
respective portions of the packet and variables T.sub.SYMS,
T.sub.SYM and N.sub.SYM represent the short GI symbol interval,
symbol interval and number of symbols in a packet respectively. The
equation in the L_LENGTH calculation uses a ceiling function
multiplied by three and then three is subtracted. For any value of
TXTIME, the L_LENGTH will be divisible by three. Thus, for HEW
packets, embodiments disclosed herein may set the L_LENGTH to a
value that is not divisible by three. In some embodiments, the
expression for L_LENGTH for HEW packets may be:
.times. ##EQU00002##
This would result in a length that is one larger than before but is
not divisible by three. Doing this may be sufficient to identify
HEW packets and may allow coexistence with legacy (IEEE
802.11a/g/n/ac) devices. Legacy stations 106 would decode the
L-SIG, and defer for a time based on the L_LENGTH value regardless
of the value.
In these embodiments, no additional signaling or other metrics need
to be added in order to identify HEW packets. That is very
appealing in HEW where efficiency is a key design parameter.
Additionally, for techniques like uplink MU-MIMO and OFDMA to be
efficient a very short preamble is desirable. These embodiments are
very efficient with no overhead and provide full coexistence with
legacy systems.
In some embodiments, the master station 102 may be arranged to
configure the PPDU to include a subsequent/additional signal field
210 (e.g., HT-SIG 212, VHT-SIG 222, or HEW-SIG 232) following the
L-SIG 206. The subsequent signal field 210 may have first and
second symbols that are BPSK modulated. In these embodiments, the
master station 102 may select a phase rotation for application to
the BPSK modulation of at least one of the first and second symbols
of the subsequent signal field 210 to distinguish a HT PPDU (FIG.
2B), a VHT PPDU (FIG. 2C) and an HEW PPDU (FIGS. 2D-2G). These
embodiments are discussed in more detail below.
In some embodiments, for communicating with HEW stations 104, the
master station 102 may configure the PPDU to include a number of
long-training fields (LTFs) 234 to be included in a multi-device
HEW preamble the PPDU. The number of LTFs 234 may be based on a
maximum number of streams communicated over a link. The master
station 102 may contend for a wireless medium during a contention
period to receive control of the medium for an HEW control period
(i.e., a TXOP) and may transmit the PPDU during the HEW control
period. During the HEW control period, the master station 102 may
operate as a master station having exclusive use of the wireless
medium for communication of data with a plurality of scheduled HEW
stations 104 in accordance with a non-contention based scheduled
OFDMA technique in accordance with signaling information indicated
in an HEW signal field. The scheduled OFDMA technique may, for
example, be an uplink (UL) OFDMA technique, a downlink (DL) OFDMA
technique or an UL or DL multi-user multiple-input multiple-output
(MU-MIMO) technique.
In some embodiments, for an HEW PPDU, each data field may be
associated with either a single user (SU) link or a multi-user (MU)
link and each link may be configurable to provide multiple streams
of data. The links of the HEW PPDU may be configurable to have a
bandwidth of one of 20 MHz, 40 MHz, 80 MHz or 160 MHz.
FIG. 2E illustrates a HEW format PPDU for single-stream
transmissions in accordance with some embodiments. In these
embodiments, all signaling information for transmission of a single
stream over a link may be included within the HEW-SIG 232
eliminating the need for one or more HEW LTFs and an HEW SIG B
field. The multi-stream HEW format PPDU of FIG. 2D, on the other
hand includes a number of LTFs 234 based on a maximum number of
streams communicated over a link and an HEW SIG-B field.
FIG. 2F illustrates a HEW format PPDU for multi-stream
transmissions with transmit beamforming in accordance with some
embodiments. In these embodiments, the signaling information from
the HEW-SIG-B field may be included within the HEW-SIG 232
eliminating the need for a second signal field (e.g., an HEW SIG B
field). In these embodiments, the number of HEW LTFs 234 may be
based on a maximum number of streams communicated over the link and
an HEW STF 233 may be included for transmit beamforming.
FIG. 2G illustrates a HEW format PPDU for multi-stream
transmissions without transmit beamforming in accordance with some
embodiments. In these embodiments, the signaling information from
the HEW-SIG-B field may be included within the HEW-SIG 232
eliminating the need for a second signal field (e.g., an HEW SIG B
field). In these embodiments, the number of HEW LTFs 234 may be
based on a maximum number of streams communicated over the link and
an HEW STF may not be needed since transmit beamforming is not
performed.
FIG. 3 illustrates signal field constellations in accordance with
some embodiments. As illustrated in FIG. 3, the L-SIG 206 for
non-HT stations 108, for HT stations 110, for VHT stations 112 and
for HEW stations 104 is illustrated with conventional BPSK
modulation (i.e., no phase rotation is applied). As further
illustrated in FIG. 3, a selected phase rotation for application to
the BPSK modulation of the first and second symbols of the
subsequent signal field 210 is shown.
In accordance with embodiments, for communicating with the HEW
stations 104, the subsequent signal field 210 may be an HEW signal
field (HEW-SIG) 232 (FIGS. 2D-2G) and the master station 102 may
apply a ninety-degree phase rotation to the BPSK modulation of the
first symbol 332A of the HEW-SIG 232 (i.e., rotated BPSK) and may
refrain from applying a ninety-degree phase rotation to the BPSK
modulation of the second symbol 332B of the HEW-SIG 232.
Accordingly, for an HEW-PPDU, the first symbol 332A of the HEW-SIG
232 is rotated BPSK and the second symbol 332B is conventional
(i.e., non-rotated) BPSK.
For communicating with VHT stations 112, the subsequent signal
field 210 may be an VHT signal field (VHT-SIG) 222 (FIG. 2C) and
the master station 102 may refrain from applying a ninety-degree
phase rotation to the BPSK modulation of the first symbol 322A of
the VHT-SIG 222 and may apply a ninety-degree phase rotation to the
BPSK modulation of the second symbol 322B of the VHT-SIG 222.
Accordingly, for a VHT-PPDU, the first symbol 322A of the VHT-SIG
222 is conventional BPSK and the second symbol 322B is rotated
BPSK.
For communicating with HT stations 110, the subsequent signal field
210 may be an HT signal field (HT-SIG) 212 (FIG. 2B) and the master
station 102 may apply a ninety-degree phase rotation to the BPSK
modulation of both the first symbol 312A and the second symbol 312B
of the HT-SIG 222. Accordingly, for a HT PPDU, both symbols of the
HT-SIG 222 are rotated BPSK.
For communicating with non-HT stations 108, the access point may
refrain from including the subsequent signal field 210 following
the L-SIG 206. The data field 208 of a non-HT PPDU may have
conventional (non-phase rotated) modulation (e.g., BPSK to 64QAM)
applied for all symbols allowing a non-HT PPDU to be identified and
distinguished from other HT, VHT and HEW PPDUs.
In accordance with some embodiments, the phase rotation of the
symbols in the subsequent signal field 210 may be used to
distinguish an HEW PPDU from a non-HEW PPDU, such as a HT PPDU or a
VHT PPDU. In these embodiments, it may not be necessary to use the
length field of the L-SIG 206 to distinguish an HEW PPDU from a
non-HEW PPDU and the length field may be set to a value that is
divisible by three, although the scope of the embodiments is not
limited in this respect. In some embodiments, the length field may
also be used to distinguish an HEW PPDU from a non-HEW PPDU, such
as a HT PPDU or a VHT PPDU.
In some embodiments, for communicating with the HEW stations 104
and some legacy stations 106 including HT stations 110 and VHT
stations 112, the master station 102 may select a value for the
rate field to cause the non-HT stations 108 to defer transmissions.
In these embodiments, the non-HT stations 108 may correctly decode
the L-SIG 206 but may be unable to correctly decode the remainder
of the PPDU based on the indicated rate (or the cyclic-redundancy
check (CRC) may fail) causing these stations to ignore the PPDU but
defer based on the length indicated in the length field of the
L-SIG 206. In these embodiments, a predetermined value (e.g., 5 or
6) may be selected for the rate field which may cause the non-HT
stations 108 to defer their transmissions because of their
inability to decode the subsequent fields.
FIG. 4 is a procedure for configuring a PPDU for communicating with
HEW stations and legacy stations in accordance with some
embodiments. Procedure 400 may be performed by an access point,
such as master station 102 (FIG. 1), for communicating with HEW
stations 104 (FIG. 1) as well as legacy stations 106 (FIG. 1).
In operation 402, a PPDU is configured to include one or more
legacy training fields and a legacy signal field (L-SIG) 206
following the legacy training fields.
In operation 404, the L-SIG 206 is configured to include at least a
length field.
In operation 406, a value for the length field that is not
divisible by three is selected for communicating with the HEW
stations 104.
In operation 408, a value for the length field that is divisible by
three is selected for communicating with at least some legacy
stations 106.
In operation 410, the PPDU is configured to include an additional
signal field following the L-SIG 206.
In operation 412, a phase rotation is selected for application to
the BPSK modulation of at least one of the first and second symbols
of the additional signal field to distinguish a HT PPDU, a VHT PPDU
and an HEW PPDU.
In some embodiments, operation 412 may be optional as the value
selected for the length field in operations 406 and 408 may be used
to distinguish HEW from non-HEW PPDUs. In some alternate
embodiments, the value for the length field that is divisible by
three is selected for communicating with all stations and the phase
rotation of the symbols of the additional signal field may be used
to distinguish a HT PPDU, a VHT PPDU and an HEW PPDU.
FIG. 5 illustrates an HEW device in accordance with some
embodiments. HEW device 500 may be an HEW compliant device that may
be arranged to communicate with one or more other HEW devices, such
as HEW stations 104 (FIG. 1) or master station 102 (FIG. 1) as well
as communicate with legacy stations 106 (FIG. 1). HEW device 500
may be suitable for operating as master station 102 (FIG. 1) or an
HEW station 104 (FIG. 1). In accordance with embodiments, HEW
device 500 may include, among other things, physical layer (PHY)
circuitry 502 and medium-access control layer circuitry (MAC) 504.
PHY 502 and MAC 504 may be HEW compliant layers and may also be
compliant with one or more legacy IEEE 802.11 standards. MAC 504
may be arranged to configure PPDUs in accordance with one or more
of FIGS. 2A-2G and PHY 502 may be arranged to transmit and receive
PPDUs, among other things. HEW device 500 may also include other
hardware processing circuitry 506 and memory 508 configured to
perform the various operations described herein.
In accordance with some embodiments, when operating as an HEW
station 104, the HEW device 500 may be arranged to distinguish an
HEW PPDU from a non-HEW PPDU based at least in part on a value in a
length field in the L-SIG 206 (FIGS. 2A-2G). In these embodiments,
the HEW device 500 may be configured to receive L-SIG 206 following
legacy training fields (i.e., L-STF 202 and L-LTF 204). The L-SIG
206 may include the length field and a rate field. The HEW device
500 may determine whether a value for the length field is divisible
by three and verify a parity bit of the L-SIG. The HEW device 500
may identify the PPDU as an HEW PPDU when the value in the length
field is not divisible three and the parity bit is verified, and
may identify the PPDU as a non-HEW PPDU (e.g., a VHT PPDU or HT
PPDU) when the value in the length field is divisible three and the
parity bit is verified. In some embodiments, the HEW device 500 may
also be configured to decode subsequent fields of the PPDU when
identified as an HEW PPDU and refrain from decoding subsequent
fields of the PPDU when the PPDU is identified as a non-HEW
PPDU.
In some embodiments, when operating as an HEW station 104, the HEW
device 500 may be arranged to distinguish an HEW PPDU from a
non-HEW PPDU based on the phase rotation of symbols of a subsequent
signal field. In these embodiments, the HEW device 500 may be
configured to receive an L-SIG 206 and receive a subsequent signal
field 210 (HT-SIG 212, VHT-SIG 222, or HEW-SIG 232). The subsequent
signal field 210 may have first and second symbols that are BPSK
modulated. In these embodiments, the HEW device 500 may determine
whether the PPDU is a HT PPDU, a VHT PPDU or an HEW PPDU based on
the phase rotation applied to the BPSK modulation of at least one
of the first and second symbols of the subsequent signal field 210.
For an HEW PPDU, a ninety-degree phase rotation may have been
applied to the BPSK modulation of the first symbol 332A and no
phase rotation would have been applied to the BPSK modulation of
the second symbol 332B of the subsequent signal field 210.
In accordance with some embodiments, the MAC 504 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 PPDU (e.g., FIG. 2D). The PHY 502 may be arranged to transmit
the HEW PPDU as discussed above. The PHY 502 may include circuitry
for modulation/demodulation, upconversion/downconversion,
filtering, amplification, etc. In some embodiments, the hardware
processing circuitry 506 may include one or more processors. In
some embodiments, two or more antennas may be coupled to the PHY
502 and arranged for sending and receiving signals including
transmission of the HEW packets. The memory 508 may be store
information for configuring the other circuitry to perform
operations for configuring and transmitting HEW packets and
performing the various operations described herein.
In some embodiments, the HEW device 500 may be configured to
communicate using OFDM communication signals over a multicarrier
communication channel. In some embodiments, HEW device 500 may be
configured to communicate in accordance with one or more specific
communication standards, such as the Institute of Electrical and
Electronics Engineers (IEEE) standards including IEEE 802.11-2012,
802.11n-2009, 802.11ac-2013, 802.11ax standards and/or proposed
specifications for WLANs, 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 embodiments, the HEW device 500 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, the HEW device 500 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.
The antennas of the HEW device 500 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 MIMO embodiments, the antennas
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.
Although the HEW device 500 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 the HEW
device 500 may refer to one or more processes operating on one or
more processing elements.
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.
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.
* * * * *