(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`(19) World Intellectual Property
`Organization
`International Bureau
`
`(43) International Publication Date
`4 December 2014 (04.12.2014)
`
`WIPO!|PCT
`
`\So
`
`(10) International Publication Number
`WO 2014/193547 Al
`
`(51)
`
`International Patent Classification:
`HO4L 27/26 (2006.01)
`HO4W56/00 (2009.01)
`
`2)
`
`International Application Number:
`
`PCT/US2014/033782
`
`(81)
`
`(22)
`
`InternationalFiling Date:
`
`11 April 2014 (11.04.2014)
`
`(74)
`
`Agent: ABUMERI, Mark, M.; KNOBBE MARTENS
`OLSON & BEAR LLP, 2040 Main Street, Fourteenth
`Floor, Irvine, CA 92614 (US).
`
`Filing Language:
`
`Publication Language:
`
`Priority Data:
`61/812,136
`61/819,028
`61/847,525
`61/871,267
`61/898,809
`14/250,276
`
`15 April 2013 (15.04.2013)
`3 May 2013 (03.05.2013)
`17 July 2013 (17.07.2013)
`28 August 2013 (28.08.2013)
`1 November 2013 (01.11.2013)
`10 April 2014 (10.04.2014)
`
`English
`
`English
`
`US
`US
`US
`US
`US
`US
`
`(84)
`
`Applicant: QUALCOMM INCORPORATED [US/US];
`Attn:
`International
`Ip Administration, 5775 Morehouse
`Drive, San Diego, CA 92121-1714 (US).
`
`(25)
`
`(26)
`
`(30)
`
`(7)
`
`(72)
`
`Inventors: VERMANI, Sameer; 5775 Morehouse Drive,
`San Diego, CA 92121-1714 (US). TANDRA,Rahul; 5775
`Morehouse Drive, San Diego, CA 92121-1714 (US).
`MERLIN, Simone; 5775 Morehouse Drive, San Diego,
`CA 92121-1714 (US). SAMPATH, Hemanth; 5775 Published:
`Morehouse Drive, San Diego, CA 92121-1714 CUS).
`with international search report (Art. 213))
`
`Designated States (unless otherwise indicated, for every
`kind of national protection available): AE, AG, AL, AM,
`AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY,
`BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM,
`DO, DZ, EC, EE, EG, ES, FL GB, GD, GE, GH, GM, GT,
`HN,HR, HU,ID,IL,IN, IR, IS, JP, KE, KG, KN, KP, KR,
`KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD, ME,
`MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ,
`OM,PA, PE, PG, PH,PL, PT, QA, RO, RS, RU, RW, SA,
`SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM,
`TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM,
`ZW.
`
`Designated States (unless otherwise indicated, for every
`kind of regional protection available): ARIPO (BW, GH,
`GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, SZ, TZ,
`UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU,TJ,
`TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK,
`EE, ES, FI, FR, GB, GR, HR, HU,IE,IS, IT, LT, LU, LV,
`MC, MK, MT, NL, NO,PL, PT, RO, RS, SE, SL SK, SM,
`TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW,
`KM,ML, MR, NE, SN, TD, TG).
`
`(54) Title: APPARATUS AND METHOD USING BACKWARDS-COMPATIBLE PREAMBLE FORMATS FOR MULTIPLE
`ACCESS WLAN COMMUNICATION SYSTEM
`
`
`
`FIG. 5
`
`(57) Abstract: Systems, methods, and devices for wireless communication are disclosed herein. One aspect of the disclosure
`provides a method of transmitting to two or more wireless communication devices. The method includes transmitting a first section
`of a preamble according to a first format, the first section of the preamble containing information informing devices compatible with
`the first format to defer to the transmission, transmitting a second section of the preamble according to a second format, the second
`section of the preamble containing tone allocation information, the tone allocation information identifying two or more wireless
`communication devices; and transmitting data to the two or more wireless communication devices simultaneously, the data con -
`tained on two or more sub-bands.
`
`
`
`wo2014/193547AX|IMNIMIMTIMININNIITA(HTTTATTC
`
`HEtoneallocation downlink packet implementation 1:
`cst
`459
`2D
`cet
`26
`455
`
`
`UE-STF
`DATAL
`E-LTF (-N2)
`(user 1 tones)
`(user 1 tones}
`(foruser 1 onuser | tones)
`HESYE
`S$]
`AWE-L'LF (1-N2)
`DATA2
`re
`L-SIT (user2 tenes)|(foruser2 on uscr2 tones)(user2 tones)
`
`
`ne-siat|te-sic2|HESIGS
`{1 or more
`
`{all tones)|{all tones)| (all tones)
`HESTF
`DATA
`HE-LTF(|-N3)
`(1 sybo)) upee symbols)
`(all tones)
`"
`(user3 tones) (user 3 tenes)|(foruser3 on user3 tones)
`
`HE-STF
`HE-LTF (1-NA)
`DATA
`{user 4 tenes)
`(user 4 tones}
`s
`(foruser4 onusertones)
`Optional beamforming from kere
`cos oe
`24 bits
`24 bits
`24 or more bits
`BPSKconstellation
`
`< constellation
`BPSK orQ
`QBPSKconstellazion
`2 bits bandwidth
`‘2 bits user
`pecitic timestreams,
`16 bits user specific modulation type
`6bits Group LD (all ones for SU}
`4 bits user spcuitic codmg type
`6 dits tail (alll zcr0s)
`12 dits user specific tone «llocation
`
`
`
`
`
` 8 bits CRC
`
`
`
`
`
`

`

`WO 2014/193547
`
`PCT/US2014/033782
`
`APPARATUS AND METHOD USING BACKWARDS-COMPATIBLE PREAMBLE
`
`FORMATS FOR MULTIPLE ACCESS WLAN COMMUNICATION SYSTEM
`
`Field
`
`BACKGROUND
`
`[0004]
`
`The present application relates generally to wireless communications, and more
`
`specifically to systems, methods, and devices to enable backward-compatible multiple
`
`access wireless communication. Certain aspects herein relate to orthogonal frequency-
`
`division multiple access (OFDMA) communications, especially in the IEEE 802.11
`
`family of wireless communication standards.
`
`Background
`
`[0002]
`
`In many telecommunication systems, communications networks are used to
`
`exchange messages among several interacting spatially-separated devices. Networks
`
`may be classified according to geographic scope, which could be, for example, a
`
`metropolitan area, a local area, or a personal area. Such networks may be designated
`
`respectively as a wide area network (WAN), metropolitan area network (MAN), local
`
`area network (LAN), or personal area network (PAN). Networks also differ according
`
`to the switching/routing technique used to interconnect the various network nodes and
`
`devices (e.g., circuit switching vs. packet switching),
`
`the type of physical media
`
`employed for transmission (e.g., wired vs. wireless), and the set of communication
`
`protocols
`
`used
`
`(e.g.,
`
`Internet protocol
`
`suite,
`
`SONET (Synchronous Optical
`
`Networking), Ethernet, etc.).
`
`[0003]
`
`Wireless networks are often preferred when the network elements are mobile
`
`and thus have dynamic connectivity needs, orif the network architecture is formed in an
`
`ad hoc, rather than fixed, topology. Wireless networks employ intangible physical
`
`media in an unguided propagation mode using electromagnetic waves in the radio,
`
`microwave, infra-red, optical, etc. frequency bands. Wireless networks advantageously
`
`facilitate user mobility and rapid field deployment when compared to fixed wired
`
`networks.
`
`

`

`WO 2014/193547
`
`PCT/US2014/033782
`
`SUMMARY
`
`[0004]
`
`The systems, methods, and devices of the invention each have several aspects,
`
`no single one of whichis solely responsible for its desirable attributes. Without limiting
`
`the scope ofthis invention as expressed by the claims which follow, some features will
`
`now be discussed briefly. After considering this discussion, and particularly after
`
`reading the section entitled “Detailed Description” one will understand howthe features
`
`of this invention provide advantages that include efficient use of the wireless medium.
`
`[0005]
`
`One aspect of the disclosure provides a method of transmitting to two or more
`
`wireless communication devices. The method includes transmitting a first section of a
`
`preamble according to a first format,
`
`the first section of the preamble containing
`
`information informing devices compatible with the first
`
`format
`
`to defer
`
`to the
`
`transmission,
`
`transmitting a second section of the preamble according to a second
`
`format, the second section of the preamble containing tone allocation information, the
`
`tone allocation information identifying two or more wireless communication devices;
`
`and transmitting data to the
`
`two or more wireless
`
`communication devices
`
`simultaneously, the data contained on two or more sub-bands.
`
`[0006]
`
`The first section of the preamble may include a one-bit code on a Q-rail which
`
`indicates a presence of the second section of the preamble. The second section of the
`
`preamble may include a signal field using the second format, the signal field comprised
`
`of at least three orthogonal frequency-division multiplexing symbols, and wherein a
`
`third symbol of the three symbols is a rotated signal which indicates a presence of the
`
`second section of the preamble. Transmitting the second section of the preamble may
`
`include transmitting one or moretraining fields according to the second format to each
`
`of the two or more wireless communication devices, the one or more training fields each
`
`configured to be used for accurate frequency offset estimation, time synchronization,
`
`and channel estimation. The method may further include assigning one or more spatial
`
`streams to each of the two or more wireless communication devices, and wherein
`
`transmitting one or more training ficlds
`
`includes transmitting one training field
`
`according to the second format to each of the two or more wireless communication
`
`devices, the numberof training fields based on a numberof spatial streams assigned to
`
`the respective wireless communication device.
`
`The method may further include
`
`assigning one or more spatial
`
`streams
`
`to each of the two or more wireless
`
`communication devices, and wherein transmitting one or more training fields comprises
`
`2.
`
`

`

`WO 2014/193547
`
`PCT/US2014/033782
`
`transmitting a number of training fields to each of the two or more wireless
`
`communication devices, the number of training fields based on a number of spatial
`
`streams assigned to the wireless communication device which is assigned a highest
`
`numberof spatial streams. The second section of the preamble may contain information
`
`sufficient to inform devices of a tone allocation granularity of the transmission. The
`
`information sufficient
`
`to inform devices of a tone allocation granularity of the
`
`transmission may comprise a bandwidth of the transmission,
`
`from which devices
`
`compatible with the second format may determine the tone allocation granularity of the
`
`transmission.
`
`The information sufficient
`
`to inform devices of a tone allocation
`
`granularity of the transmission may comprise a code ofat least one bit in a signal field
`
`indicating the tone allocation granularity of the transmission. The tone allocation
`
`granularity may comprise an indication of the bandwidth size of each of a number of
`
`sub-bands. The second section of the preamble may further include an indication of a
`
`number of sub-bands assigned to each of the identified two or more wireless
`
`communication devices. The second section of the preamble may include a signal field
`
`according to the second format, and wherein a first symbol of the signal field is
`
`transmitted in duplicate in each of a plurality of channels and contains information
`
`identifying an entire bandwidth, and wherein a subsequent symbolof the signal field is
`
`transmitted using the entire bandwidth.
`
`[0007]
`
`One aspect of the present disclosure provides an apparatus
`
`for wireless
`
`communication. The apparatus includes a transmitter configured to transmit over a
`
`bandwidth, configured to transmit a first section of a preamble according toafirst
`
`format,
`
`the first section of the preamble containing information informing devices
`
`compatible with the first format to defer to the transmission; transmit a second section
`
`of the preamble according to a second format, the second section of the preamble
`
`contaming tone allocation information, the tone allocation information identifying two
`
`or more wireless communication devices; and transmit data to the two or more wireless
`
`communication devices simultancously, the data contained on two or more sub-bands.
`
`Thefirst section of the preamble may include a one-bit code on a Q-rail which indicates
`
`a presence of the second section of the preamble to devices compatible with the second
`
`format. The second section of the preamble may include a signalfield using the second
`
`format,
`
`the signal
`
`field comprising at
`
`least
`
`three orthogonal
`
`frequency-division
`
`multiplexing symbols, and wherein a third symbol of the three symbols is a rotated
`
`-3-
`
`

`

`WO 2014/193547
`
`PCT/US2014/033782
`
`signal which indicates the presence of the second format signal field. The transmitter
`
`may be configured to transmit
`
`the second section of the preamble, comprising
`
`transmitting one or more training fields according to the second format to each of the
`
`two or more wireless communication devices,
`
`the one or more training ficlds cach
`
`configured to be used for accurate frequency offset estimation, time synchronization,
`
`and channel estimation. The transmitter may be further configured to transmit to each
`
`of the two or more wireless communication devices on one or more spatial streams, and
`
`wherein transmitting one or more training fields according to the second format
`
`comprises transmitting a training ficld according to the second format to cach of the two
`
`or more wireless communication devices, the number of training fields based on a
`
`numberof spatial streams assigned to the respective wireless communication device.
`
`The transmitter may be further configured to transmit to each of the two or more
`
`wireless communication devices on one or more spatial
`
`streams, and wherein
`
`transmitting one or more training fields according to the second format comprises
`
`transmitting a number of training fields to each of the two or more wireless
`
`communication devices, the number of training fields based on a number of spatial
`
`streams assigned to the wireless communication device which is assigned a highest
`
`numberof spatial streams. The second section of the preamble may contain information
`
`sufficient to inform devices of a tone allocation granularity of the transmission. The
`
`second section of the preamble may include a second format signal field, and wherein a
`
`first symbol of the second format signal field is transmitted in duplicate in each of a
`
`plurality of channels and contains information identifying an entire bandwidth, and
`
`wherein a subsequent symbol of the second format signal field is transmitted using the
`
`entire bandwidth.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0008]
`
`FIG.1 illustrates a channel allocation for channels available for IEEE 802.11
`
`systems.
`
`[0009]
`
`FIG.2 illustrates a structure of a physical-layer packet (PPDU frame) which
`
`may be used in an IEEE 802.1 1a/b/g/j/p communication.
`
`[0010]
`
`FIG.3 illustrates a structure of a physical-layer packet (PPDU frame) which
`
`may be used in an IEEE 802.11n communication.
`
`

`

`WO 2014/193547
`
`PCT/US2014/033782
`
`[0011]
`
`FIG.4 illustrates a structure of a physical-layer packet (PPDU frame) which
`
`may be used in an IEEE 802.1 1ac communication.
`
`[0012]
`
`FIG. 5 illustrates an exemplary structure of a downlink physical-layer packet
`
`which may be used to enable backward-compatible multiple
`
`access wireless
`
`communications.
`
`[0013]
`
`FIG.6 illustrates an exemplary illustration of a signal which may be used to
`
`identify STAsandto allocate sub-bands to those STAs.
`FIG.7 illustrates a 2" exemplary structure of a downlink physical-layer packet
`
`[0014]
`
`which may be used to enable backward-compatible multiple
`
`access wireless
`
`communications.
`
`[0013]
`
`FIG.8 illustrates a 3"? exemplary structure of a downlink physical-layer packet
`
`which may be used to enable backward-compatible multiple
`
`access wireless
`
`communications.
`
`[0016]
`
`FIG.9 illustrates a 4" exemplary structure of a downlink physical-layer packet
`
`which may be used to enable backward-compatible multiple
`
`access wireless
`
`communications.
`
`[0017]
`
`FIG. 10 illustrates an example of a wireless communication system in which
`
`aspects of the present disclosure may be employed.
`
`[0018]
`
`FIG. 11 shows a functional block diagram of an exemplary wireless device that
`
`may be employed within the wireless communication system of FIG.1.
`
`[0019]
`
`FIG. 12 illustrates an exemplary structure of an uplink physical-layer packet
`
`which may be used to enable backward-compatible multiple
`
`access wireless
`
`communications.
`
`[0020]
`
`FIG. 13 illustrates a process flow diagram for an example method of a
`
`transmitting a high-efficiency packet to two or more wireless communication devices.
`
`[0021]
`
`FIG.14 illustrates an exemplary structure of a hybrid downlink physical-layer
`
`packet which may be used to enable backward-compatible multiple access wireless
`
`communications.
`
`[0022]
`
`[0023]
`
`[0024]
`
`[0025]
`
`[0026]
`
`FIG.15 illustrates an exemplary method of transmitting a hybrid packet.
`
`FIG.16 illustrates an exemplary method of receiving a hybrid packet.
`
`FIG.17 illustrates a packet with one example HE preamble format.
`
`FIG.18 illustrates a packet with another example HE preamble format.
`
`FIG.19 illustrates a packet with another example HE preamble format.
`
`-5-
`
`

`

`WO 2014/193547
`
`PCT/US2014/033782
`
`FIG.20 illustrates example bit allocation for an HE-SIG1field.
`[0027]
`
`[0028]
`
`FIG. 21 illustrates an exemplary structure of an uplink physical-layer packet
`
`which may be used to enable backward-compatible multiple
`
`access wireless
`
`communications.
`
`[0029]
`
`FIG. 22 illustrates another exemplary structure of an uplink physical-layer
`
`packet which may be used to enable backward-compatible multiple access wireless
`
`communications.
`
`[0030]
`
`[0031]
`
`[0032]
`
`[0033]
`
`FIG.23 illustrates an exemplary method of receiving a packet.
`
`FIG.24 is an exemplary uplink packet structure for an uplink HE packet.
`
`FIG.25 is exemplary uplink packet structure for an uplink HE packet.
`
`FIG. 26 is an exemplary downlink message from the AP which includes
`
`information on how many spatial streams each transmitting device may use.
`
`[0034]
`
`FIG.27 is anillustration of a tone-interleaved LTF which may be used in an UL
`
`OFDMApacket.
`
`[0035]
`
`FIG. 28 is an illustration of a sub-band interleaved LTF which may be used in
`
`an UL OFDMApacket.
`
`[0036]
`
`FIG. 29 is an exemplary LTF portion of a packet which may be transmitted in
`
`an UL OFDMApacket.
`
`[0037]
`
`FIG. 30 is an illustration of a packet with a commonSIG field prior to the HE-
`
`STFand per-user SIG field after all of the HE-LTFs.
`
`[0038]
`
`FIG.31 illustrates an exemplary method of transmitting to one or more devices
`
`in a single transmission.
`
`[0039]
`
`FIG. 32 illustrates an exemplary method of transmitting to one or more first
`
`devices with a first set of capabilities and simultaneously transmitting to one or more
`
`second devices with a secondset of capabilities.
`
`[0040]
`
`FIG.33 illustrates an exemplary method of receiving a transmission compatible
`
`with both devices with a first set of capabilities and devices with a second set of
`
`capabilitics.
`
`[0041]
`
`FIG. 34 illustrates an exemplary method of receiving a transmission, where
`
`portions of the transmission are transmitted by different wireless devices.
`
`[0042]
`
`FIG.35 illustrates various components that may be utilized in a wireless device
`
`that may be employed within the wireless communication system.
`
`

`

`WO 2014/193547
`
`PCT/US2014/033782
`
`[0043]
`
`Various aspects of the novel systems, apparatuses, and methods are described
`
`DETAILED DESCRIPTION
`
`more fully hereinafter with reference to the accompanying drawings. The teachings
`
`disclosed may, however, be embodied in many different forms and should not be
`
`construed as limited to any specific structure or function presented throughout this
`
`disclosure. Rather, these aspects are provided so that this disclosure will be thorough
`
`and complete, and will fully convey the scope of the disclosure to those skilled in the
`
`art. Based on the teachings herein one skilled in the art should appreciate that the scope
`
`of the disclosure is intended to cover any aspect of the novel systems, apparatuses, and
`
`methods disclosed herein, whether implemented independently of or combined with any
`
`other aspect of the invention. For example, an apparatus may be implemented or a
`
`method may be practiced using any numberof the aspects set forth herein.
`
`In addition,
`
`the scope of the invention is intended to cover such an apparatus or method which is
`
`practiced using other structure, functionality, or structure and functionality in addition to
`
`or other than the various aspects of the invention set forth herein.
`
`It should be
`
`understood that any aspect disclosed herein may be embodied by one or more elements
`
`of a claim.
`
`[0044]
`
`Although particular
`
`aspects
`
`are described herein, many variations
`
`and
`
`permutations of these aspects fall within the scope of the disclosure. Although some
`
`benefits and advantages of the preferred aspects are mentioned,
`
`the scope of the
`
`disclosure is not
`
`intended to be limited to particular benefits, uses, or objectives.
`
`Rather, aspects of the disclosure are intended to be broadly applicable to different
`
`wireless technologies, system configurations, networks, and transmission protocols,
`
`some of which are illustrated by way of example in the figures and in the following
`
`description of the preferred aspects. The detailed description and drawings are merely
`
`illustrative of the disclosure rather than limiting, the scope of the disclosure being
`
`defined by the appended claims and equivalents thereof.
`
`[0045]
`
`Wircless network technologies may include various types of wireless local arca
`
`networks (WLANs). A WLAN maybe used to interconnect nearby devices together,
`
`employing widely used networking protocols. The various aspects described herein
`
`may apply to any communication standard, such as WiFi or, more generally, any
`
`member of the IEEE 802.11 family of wireless protocols. For example, the various
`
`aspects described herein may be used as part of a [IEEE 802.11 protocol, such as an
`
`-7-
`
`

`

`WO 2014/193547
`
`PCT/US2014/033782
`
`802.11 protocol which supports orthogonal
`
`frequency-division multiple access
`
`(OFDMA) communications.
`
`[0046]
`
`It may be beneficial to allow multiple devices, such as STAs, to communicate
`
`with an AP at the same time. For example, this may allow multiple STAsto receive a
`
`response from the AP in less time, and to be able to transmit and receive data from the
`
`AP with less delay. This may also allow an AP to communicate with a larger numberof
`
`devices overall, and may also make bandwidth usage moreefficient. By using multiple
`
`access communications,
`
`the AP may be able to multiplex OFDM symbols to, for
`
`example, fourdevices at once over an 80 MHz bandwidth, where cach device utilizes 20
`
`MHz bandwidth. Thus, multiple access may be beneficial in some aspects, as it may
`
`allow the AP to make moreefficient use of the spectrum available to it.
`
`[0047]
`
`It has been proposed to implement such multiple access protocols in an OFDM
`
`system such as the 802.11 family by assigning different subcarriers (or tones) of
`
`symbols transmitted between the AP and the STAsto different STAs.
`
`In this way, an
`
`AP could communicate with multiple STA’s with a single transmitted OFDM symbol,
`
`where different tones of the symbol were decoded and processed by different STA’s,
`
`thus allowing simultaneous data transfer to multiple STA’s.
`
`These systems are
`
`sometimes referred to as OFDMA systems.
`
`[0048]
`
`Such a tone allocation scheme is referred to herein as a “high-efficiency”
`
`(HE) system, and data packets transmitted in such a multiple tone allocation system may
`
`referred to as high-efficiency (HE) packets. Various structures of such packets,
`
`including backward compatible preamble fields are described in detail below.
`
`[0049]
`
`Various aspects of the novel systems, apparatuses, and methods are
`
`described more fully hereinafter with reference to the accompanying drawings. This
`
`disclosure may, however, be embodied in many different forms and should not be
`
`construed as limited to any specific structure or function presented throughout this
`
`disclosure. Rather, these aspects are provided so that this disclosure will be thorough
`
`and complete, and will fully convey the scope of the disclosure to those skilled in the
`
`art. Based on the teachings herein one skilled in the art should appreciate that the scope
`
`of the disclosure is intended to cover any aspect of the novel systems, apparatuses, and
`
`methods disclosed herein, whether implemented independently of, or combined with,
`
`any other aspect of the invention. For example, an apparatus may be implemented or a
`
`method may be practiced using any number of the aspects sct forth herein.
`
`In addition,
`
`-8-
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`the scope of the invention is intended to cover such an apparatus or method which is
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`practiced using other structure, functionality, or structure and functionality in addition to
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`or other than the various aspects of the invention set forth herein.
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`It should be
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`understood that any aspect disclosed herein may be embodied by one or more elements
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`of a claim.
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`[0050]
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`Although particular aspects are described herein, many variations and
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`permutations of these aspects fall within the scope of the disclosure. Although some
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`benefits and advantages of the preferred aspects are mentioned,
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`the scope of the
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`disclosure is not
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`intended to be limited to particular benefits, uses, or objectives.
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`Rather, aspects of the disclosure are intended to be broadly applicable to different
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`wireless technologies, system configurations, networks, and transmission protocols,
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`some of whichare illustrated by way of example in the figures and in the following
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`description of the preferred aspects. The detailed description and drawings are merely
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`illustrative of the disclosure rather than limiting, the scope of the disclosure being
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`defined by the appended claims and equivalents thereof.
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`[0051]
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`Popular wireless network technologies may include various types of wireless
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`local area networks (WLANs). A WLAN may be used to interconnect nearby devices
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`together, employing widely used networking protocols. The various aspects described
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`herein may apply to any communication standard, such as a wireless protocol.
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`[0052]
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`In some aspects, wireless signals may be transmitted according to an 802.11
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`protocol. In some implementations, a WLAN includes various devices which are the
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`components that access the wireless network. For example, there may be two types of
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`devices: access points (APs) and clients (also referred to as stations, or STAs).
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`In
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`general, an AP mayserve as a hub orbase station for the WLAN and an STA serves as
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`a user of the WLAN. For example, an STA may be a laptop computer, a personal
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`digital assistant (PDA), a mobile phone,etc.
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`In an example, an STA connects to an AP
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`via a WiFi compliant wireless link to obtain general connectivity to the Internet or to
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`other wide area networks. In some implementations an STA mayalso be used as an AP.
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`[0053]
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`An access point (AP) may also comprise, be implemented as, or known as a
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`base station, wireless access point, access nodeor similar terminology.
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`[0054]
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`A station “STA” may also comprise, be implemented as, or known as an
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`access terminal (AT), a subscriber station, a subscriber unit, a mobile station, a remote
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`station, a remote terminal, a user terminal, a user agent, a user device, user equipment,
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`or some other terminology. Accordingly, one or more aspects taught herein may be
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`incorporated into a phone (e.g., a cellular phone or smartphone), a computer (e.g., a
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`laptop), a portable communication device, a headset, a portable computing device(e.g.,
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`a personal data assistant), an entertainment device (c.g., a music or video device, or a
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`satellite radio), a gaming device or system, a global positioning system device, or any
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`other suitable device that is configured for network communication via a wireless
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`medium.
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`[0055]
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`As discussed above, certain of the devices described herein may implement an
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`802.11 standard, for example. Such devices, whether used as an STA or AP or other
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`device, may be used for smart metering or in a smart grid network. Such devices may
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`provide sensor applications or be used in home automation. The devices may instead or
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`in addition be used in a healthcare context, for example for personal healthcare. They
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`may also be used for surveillance, to enable extended-range Internet connectivity (e.g.,
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`for use with hotspots), or to implement machine-to-machine communications.
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`[0056]
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`FIG.1 illustrates a channel allocation for channels available for 802.11 systems.
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`Various [EEE 802.11 systems support a numberofdifferent sizes of channels, such as 5,
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`10, 20, 40, 80, and 160 MHz channels. For example, and 802.1 lac device may support
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`20, 40, and 80 MHz channel bandwidth reception and transmission. A larger channel
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`may comprise two adjacent smaller channels. For example, an 80 MHz channel may
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`comprise two adjacent 40 MHz channels.
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`In the currently implemented IEEE 802.11
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`systems, a 20 MHz channel contains 64 subcarriers, separated from each other by 312.5
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`kHz. Of these subcarriers, a smaller number may be used for carrying data. For
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`example, a 20 MHz channel may contain transmitting subcarriers numbered -1 to -28
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`and | to 28, or 56 subcarriers. Some of these carriers may also be used to transmit pilot
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`signals. Over the years, the [EEE 802.11 standard has evolved through several versions.
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`Older versions include the 1la/g and 11n versions. The most recently released is the
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`802.1 lac version.
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`[0057]
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`FIGs, 2, 3, and 4 illustrates data packet formats for several currently cxisting
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`JEEE 802.11 standards. Turning first to Figure 2, a packet format for IEEE 802.1 1a,
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`11b, and 11g is illustrated. This frame includes a short training field 22, a long training
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`field 24, and a signal field 26. The training fields do not transmit data, but they allow
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`synchronization between the AP and the receiving STAs for decoding the data in the
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`data field 28.
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`[0058]
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`The signal field 26 delivers information from the AP to the STA’s about the
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`nature of the packet being delivered.
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`In IEEE 802.1 1a/b/g devices, this signal field has
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`a length of 24 bits, and is transmitted as a single OFDM symbol at a 6 Mb/srate using
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`BPSK modulation and a code rate of 4%. The information in the SIG ficld 26 includes 4
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`bits describing the modulation scheme of the data in the packet (e.g. BPSK, 16QAM,
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`64QAM,etc.), and 12 bits for the packet length. This information is used by a STA to
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`decode the data in the packet when the packet is intended for the STA. When a packet
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`is not intended for a particular STA, the STA will defer any communication attempts
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`during the time period defined in the length field of the SIG symbol 26, and may, to
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`save power, enter a sleep mode during the packet period of up to about 5.5 msec.
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`[0059]
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`As features have been added to IEEE 802.11, changes to the format of the SIG
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`fields in data packets were developed to provide additional information to STAs. Figure
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`3 shows the packet structure for the TEEE 802.11n packet. The 11n addition to the
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`JEEE.802.11 standard added MIMO functionality to TIEEE.802.11 compatible devices.
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`To provide backward compatibility for systems containing both IEEE 802.11a/b/g
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`devices and IEEE 802.11n devices, the data packet for IEEE 802.11n systems also
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`includes the STF, LTF, and SIG fields of these earlier systems, noted as L-STF 22, L-
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`LTF 24, and L-SIG 26 with a prefix L to denote that they are “legacy” fields. To
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`provide the needed information to STA’s in an IEEE 802.11n environment,
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`two
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`additional signal symbols 140 and 142 were added to the IEEE 802.11n data packet.
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`In
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`contrast with the SIG field and L-SIG field 26, however, these signal fields used rotated
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`BPSK modulation (also referred to as QBPSK modulation). When a legacy device
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`configured to operate with IEEE 802.11a/b/g receives such a packet, it will receive and
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`decode the L-SIG field 26 as a normal
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`l1la/b/g packet. However, as the device
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`continued decoding additional bits, they will not be decoded successfully because the
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`format of the data packet after the L-SIG field 26 is different from the format of an
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`lla/b/g packet, and the CRC check performed by the device during this process will
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`fail. This causes these legacy devices to stop processing the packet, but still defer any
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`further operations until a time period has passed defined by the length field in the
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`initially decoded L-SIG. In contrast, new devices compatible with IEEE 802.11n would
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`sense the rotated modulation in the HT-SIG fields, and process the packet as an 802.11n
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`packet. Furthermore, an 11n device can tell that a packet is intended for an 11la/b/g
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`device because if it senses any modulation other than QBPSK in the symbol following
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`the L-SIG 26, it will ignore it as an 1la/b/g packet. After the HT-SIG1 and SIG2
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`symbols, additional training fields suitable for MIMO communication are provided,
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`followed by the data 28.
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`[0060]
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`FIG. 4 illustrates a frame format for the currently existing [EEE 802.1lac
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`standard, which added multi-user MIMO functional