(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2007/0204052 A1
`Trainin et al.
`(43) Pub. Date:
`Aug. 30, 2007
`
`US 20070204052A1
`
`(54) METHOD, APPARATUS, AND SYSTEM OF
`WIRELESS TRANSMISSION WITH FRAME
`ALIGNMENT
`
`(76) Inventors: Solomon B. Trainin, Haifa (IL); Assaf
`Kasher, Haifa (IL)
`
`Correspondence Address:
`PEARL COHEN ZEDEK LATZER, LLP
`1500 BROADWAY, 12TH FLOOR
`NEW YORK, NY 10036 (US)
`
`(21) Appl. No.:
`
`11/360,865
`
`(22) Filed:
`
`Feb. 24, 2006
`
`Publication Classification
`
`(51) Int. Cl.
`(2006.01)
`G06F 5/16
`(52) U.S. Cl. .............................................................. 709/230
`
`ABSTRACT
`(57)
`Embodiments of the present invention provide a method,
`apparatus, and system of wireless transmission with frame
`alignment. For example, a method in accordance with
`demonstrative embodiments of the invention may include
`synchronizing between a transmitter using a first modulation
`scheme, which may have multiple frame formats, and a
`receiver using a second modulation scheme, by calculating
`a transmission time that aligns an interframe space start time
`of the first and second modulation schemes. Other features
`are described and claimed.
`
`120
`
`130
`
`140
`
`STATION
`
`LEGACY STATION
`
`144
`145
`
`143
`
`A\-139
`
`149
`
`128
`
`
`
`138
`
`148
`
`100
`
`110
`
`Exhibit 1011
`Panasonic v. UNM
`IPR2024-00364
`Page 1 of 10
`
`

`

`Patent Application Publication Aug. 30, 2007 Sheet 1 of 3
`
`US 2007/0204052 A1
`
`120
`
`130
`
`140
`
`STATION
`
`LEGACY STATION
`
`128
`
`
`
`138
`
`148
`
`100
`
`Exhibit 1011
`Panasonic v. UNM
`IPR2024-00364
`Page 2 of 10
`
`

`

`Patent Application Publication Aug. 30, 2007 Sheet 2 of 3
`
`US 2007/0204052 A1
`
`
`
`082
`
`
`
`Îny
`
`CN
`CD
`
`Exhibit 1011
`Panasonic v. UNM
`IPR2024-00364
`Page 3 of 10
`
`

`

`Patent Application Publication Aug. 30, 2007 Sheet 3 of 3
`
`US 2007/0204052 A1
`
`4U 3.6U 3.6U 36U
`4U
`8U
`4U
`8U
`3U
`310
`a-RY2RY2RY2RY-R2 R2N2 N2R
`Y a
`
`320
`NA
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`DATASYM3;
`DATASYM2
`
`DATASYM2 350° 340
`
`DATASYM
`DATASYM2
`
`|
`DATASYM2
`3.6U 3.6U 3.6U
`
`DATASYM3
`DATASYM
`DATASYM2
`
`
`
`ENERGY DETECTION
`FIG. 4
`
`Exhibit 1011
`Panasonic v. UNM
`IPR2024-00364
`Page 4 of 10
`
`

`

`US 2007/0204052 A1
`
`Aug. 30, 2007
`
`METHOD, APPARATUS, AND SYSTEM OF
`WRELESS TRANSMISSION WITH FRAME
`ALIGNMENT
`
`BACKGROUND OF THE INVENTION
`0001. In some wireless local area networks (WLANs).
`different stations may transmit frames of different modula
`tions types. For example, the IEEE-Std 802.11, 1999 Edition
`(ISO/fEC 8802-11: 1999) (“802.11”) set of standards allows
`coexistence of different formats of physical layer (PHY)
`protocol data units (PPDUs), or frames, in the same fre
`quency channel. The various formats may differ, for
`example, in the respective sizes of the transmitted frames.
`0002 Network stations may use a channel access mecha
`nism and a control mechanism to protect transportation of
`packets over the network, e.g., to avoid collision of frames.
`For example, a station may wait for the channel to be clear
`before transmitting the next frame. One solution may be to
`utilize a request-to-send/clear-to-send (RTS/CTS) mecha
`nism, including setting a network allocation vector (NAV) to
`reserve the wireless medium for a predetermined period of
`time. However, such a protection method may cause sig
`nificant overhead by taking up part of the available band
`width and/or power for transmission of management frames.
`In addition, a network station that is in a power-save mode
`may not receive the RTS/CTS frames.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0003. The subject matter regarded as the invention is
`particularly pointed out and distinctly claimed in the con
`cluding portion of the specification. The invention, however,
`both as to organization and method of operation, together
`with features and advantages thereof, may best be under
`stood by reference to the following detailed description
`when read with the accompanied drawings in which:
`0004 FIG. 1 is a schematic diagram of a wireless com
`munication system in accordance with some demonstrative
`embodiments of the present invention;
`0005 FIG. 2 is a schematic diagram of different frame
`formats that may be helpful in understanding some demon
`strative embodiments of the invention;
`0006 FIG. 3 is a schematic diagram of aligned frames in
`accordance with one demonstrative embodiment of the
`invention; and
`0007 FIG. 4 is a schematic diagram of aligned frames in
`accordance with another demonstrative embodiment of the
`invention.
`0008. It will be appreciated that for simplicity and clarity
`of illustration, elements shown in the figures have not
`necessarily been drawn to scale. For example, the dimen
`sions of some of the elements may be exaggerated relative
`to other elements for clarity. Further, where considered
`appropriate, reference numerals may be repeated among the
`figures to indicate corresponding or analogous elements.
`
`DETAILED DESCRIPTION OF EMBODIMENTS
`OF THE INVENTION
`0009. In the following detailed description, numerous
`specific details are set forth in order to provide a thorough
`understanding of the invention. However, it will be under
`
`stood by those of ordinary skill in the art that the present
`invention may be practiced without these specific details. In
`other instances, well-known methods, procedures, compo
`nents and circuits have not been described in detail so as not
`to obscure the present invention.
`0010 Unless specifically stated otherwise, as apparent
`from the following discussions, it is appreciated that
`throughout the specification discussions utilizing terms such
`as “processing.”"computing.”"calculating.'"determining.”
`or the like, refer to the action and/or processes of a computer
`or computing system, or similar electronic computing
`device, that manipulate and/or transform data represented as
`physical. Such as electronic, quantities within the computing
`system's registers and/or memories into other data similarly
`represented as physical quantities within the computing
`system's memories, registers or other such information
`storage, transmission or display devices.
`0011 Embodiments of the present invention may include
`an apparatus for performing the operations herein. This
`apparatus may be specially constructed for the desired
`purposes, or it may comprise a general-purpose computer
`selectively activated or reconfigured by a computer program
`stored in the computer. Such a computer program may be
`stored in a computer readable storage medium, Such as, but
`not limited to, any type of disk, including floppy disks,
`optical disks, magnetic-optical disks, read-only memories
`(ROM), compact disc read-only memories (CD-ROM), ran
`dom access memories (RAM), electrically programmable
`read-only memories (EPROM), electrically erasable and
`programmable read only memories (EEPROM), FLASH
`memory, magnetic or optical cards, or any other type of
`media Suitable for storing electronic instructions and capable
`of being coupled to a computer system bus.
`0012. It should be understood that the present invention
`may be used in a variety of applications. Although the
`present invention is not limited in this respect, the circuits
`and techniques disclosed herein may be used in many
`apparatuses Such as units of a wireless communication
`system, for example, a wireless local area network (WLAN)
`communication system and/or in any other unit and/or
`device. Units of a WLAN communication system intended
`to be included within the scope of the present invention
`include, by way of example only, modems, mobile units
`(MU), access points (AP), wireless transmitters/receivers,
`and the like.
`0013 Devices, systems and methods incorporating
`aspects of embodiments of the invention are also suitable for
`computer communication network applications,
`for
`example, intranet and Internet applications. Embodiments of
`the invention may be implemented in conjunction with
`hardware and/or software adapted to interact with a com
`puter communication network, for example, a LAN, wide
`area network (WAN), a personal area network (PAN), or a
`global communication network, for example, the Internet.
`0014 Types of WLAN communication systems intended
`to be within the scope of the present invention include,
`although are not limited to, WLAN communication systems
`as described by “IEEE-Std 802.11, 1999 Edition (ISO/IEC
`8802-11: 1999) standard (“the 802.11 standard”), and more
`particularly in “International Standard ISO/IEC 8802
`11:1999/Amd 1:2000(E) IEEE Std 802.11a-1999 Part 11:
`Wireless LAN Medium Access Control (MAC) and Physical
`
`Exhibit 1011
`Panasonic v. UNM
`IPR2024-00364
`Page 5 of 10
`
`

`

`US 2007/0204052 A1
`
`Aug. 30, 2007
`
`Layer (PHY) specifications Amendment 1: High-speed
`Physical Layer in the 5 GHz band” (“the 802.11a standard”),
`“IEEE-Std 802.11n High throughput extension to the
`802.11” (“the 802.11n standard”), and the like.
`0.015 Although the scope of the present invention is not
`limited in this respect, the circuits and techniques disclosed
`herein may also be used in units of wireless communication
`systems, digital communication systems, satellite commu
`nication systems, and the like. Some embodiments of the
`invention may be used in conjunction with one or more types
`of wireless communication signals and/or systems, for
`example, radio frequency (RF), infra red (IR), frequency
`division multiplexing (FDM), orthogonal FDM (OFDM),
`time-division multiplexing (TDM), time-division multiple
`access (TDMA), extended TDMA (E-TDMA), general
`packet radio service (GPRS), extended GPRS, code-division
`multiple access (CDMA), wideband CDMA (WCDMA),
`CDMA2000, multi-carrier modulation (MDM), or the like.
`Embodiments of the invention may be used in various other
`apparatuses, devices, systems and/or networks.
`0016 Although the scope of the present invention is not
`limited in this respect, the system and method disclosed
`herein may be implemented in many wireless, handheld and
`portable communication devices. By way of example, wire
`less, handheld and portable communication devices may
`include wireless and cellular telephones, Smart telephones,
`personal digital assistants (PDAs), web-tablets and any
`device that may provide wireless access to a network such,
`an intranet or the internet. It should be understood that the
`present invention may be used in a variety of applications.
`0017 Part of the discussion herein may relate, for
`demonstrative purposes, to transmitting a frame, e.g., a
`physical layer (PHY) protocol data unit (PPDU). However,
`embodiments of the invention are not limited in this regard,
`and may include, for example, transmitting a signal, a
`packet, a block, a data portion, a data sequence, a data signal,
`a data packet, a preamble, a signal field, a content, an item,
`a message, or the like.
`0018 Reference is made to FIG. 1, which schematically
`illustrates a wireless communication system 100 in accor
`dance with an embodiment of the present invention. It will
`be appreciated by those skilled in the art that the simplified
`components schematically illustrated in FIG. 1 are intended
`for demonstration purposes only, and that other components
`may be required for operation of the wireless devices. Those
`of skill in the art will further note that the connection
`between components in a wireless device need not neces
`sarily be exactly as depicted in the schematic diagram.
`0019. In some demonstrative embodiments of the inven
`tion, communication system 100 may for example, a wire
`less network or a network that may include wireless com
`ponents. For example, communication system 100 may
`include or may be a wireless local area network (WLAN) in
`accordance with the 802.11 family of standards. Although
`embodiments of the invention are not limited in this respect,
`communication system 100 may include, for example, a
`basic service set (BSS) provider such as an access point (AP)
`110, as well as one or more wireless mobile units such as a
`station (STA), for example stations 120, 130, and 140.
`0020. In some embodiments, AP 110 and one or more of
`STA 120, 130, and 140 may communicate network traffic
`
`over a shared access medium using one or more wireless
`links, e.g., links 128, 138, and 148, respectively. Links 128,
`138, and 148 may each include a downlink and an uplink, as
`are known in the art. Although embodiments of the invention
`are not limited in this respect, the traffic that may be carried
`via links 128, 138, and 148 may include packets, frames, or
`other collections of signals and/or data, such as, e.g., media
`access controller (MAC) protocol data units (MPDUs) and/
`or physical layer (PHY) protocol data units (PPDUs), that
`may make up a transmission of wireless signals. In accor
`dance with some demonstrative embodiments of the inven
`tion, wireless communication system 100 may enable coex
`istence of different modulation schemes and/or frame
`formats, as explained in more detail below with reference to
`FIG 2.
`0021 Although embodiments of the invention are not
`limited in this respect, each of AP 110, STA 120, STA 130,
`and STA 140 may be operatively coupled with at least one
`radio frequency antenna 119, 129, 139, and 149, respec
`tively, which may include or may be an internal and/or
`external RF antenna, for example, a dipole antenna, a
`monopole antenna, an omni-directional antenna, an end-fed
`antenna, a circularly polarized antenna, a micro-strip
`antenna, a diversity antenna, or any other type of antenna
`Suitable for transmitting and/or receiving wireless commu
`nication signals, blocks, frames, transmission streams, pack
`ets, messages and/or data.
`0022. In some embodiments, AP 110 may be a dedicated
`device with additional functionality Such as, for example,
`providing a bridge to wired network infrastructure or arbi
`trating communication of stations in the WLAN. For
`example, AP 110 may facilitate communication with a wider
`network Such as, for example, the Internet or an intranet, by
`either wired or wireless communication. A BSS provider
`such as AP 110 may in some embodiments associate wireless
`devices such as, for example, STA130 with other equipment
`Such as, for example, personal computers, workstations,
`printers, and the like.
`0023. In some embodiments, AP 110 may include a
`transmitter 111 and a receiver 112 to transmit and receive
`network traffic, e.g., over wireless links 128, 138, and 148.
`In addition, AP 110 may include a physical layer (PHY) 113
`and a media access controller (MAC) 114 to control the
`operation of the transmitter and receiver. Transmitter 111
`and receiver 112 may include any components involved in
`the process of transmitting and receiving network traffic,
`respectively, including components of PHY 113 and MAC
`114. Similarly, STA 120 and STA 140 may include, respec
`tively, transmitters 121 and 141, receivers 122 and 124,
`PHYS 123 and 143, and MACs 124 and 144. It will be
`appreciated that AP 110 and STAs 120, 130 and 140 may
`include other suitable software and/or hardware elements,
`e.g., a memory, a processor, a storage unit, and the like.
`0024. Although embodiments of the invention are not
`limited in this respect, AP 110 may be able to transmit and
`receive frames using several modulation schemes and/or
`frame formats. For example, AP 110 may use a first modu
`lation scheme, e.g., a high-throughput (HT) modulation
`scheme such as a multiple-input-multiple-output (MIMO)
`orthogonal frequency division multiplexing (OFDM) modu
`lation scheme, to communicate traffic with a HT station, e.g.,
`STA 120. Although embodiments of the invention are not
`
`Exhibit 1011
`Panasonic v. UNM
`IPR2024-00364
`Page 6 of 10
`
`

`

`US 2007/0204052 A1
`
`Aug. 30, 2007
`
`limited in this respect, one or more components of AP 110
`and/or STA 120, e.g., PHY's 113 and 123 and MACs 114 and
`124, respectively, may be adapted to operate in accordance
`with the 802.11n standard or another wireless communica
`tion protocol that allows relatively high throughput, e.g., up
`to 600 megabytes per second. In accordance with embodi
`ments of the invention, the first modulation scheme may be
`used with multiple frame formats, e.g., a HT-optimal format
`and a mixed-mode format, as explained in more detail below
`with reference to FIG. 2. In some embodiments, STA 120
`and AP 110 may use different first and second frame formats
`of the same modulation scheme, e.g., the high-throughput
`modulation scheme MIMO-OFDM.
`0025. In some embodiments, one or more stations of
`WLAN 100, e.g., STA 140, may transmit and receive frames
`using a second modulation scheme, which may be different
`from the first modulation scheme used by AP 110 and/or the
`scheme used by other stations of WLAN 100. For example,
`STA 140 may use orthogonal frequency division multiplex
`ing (OFDM) in accordance with the 802.11a standard, or any
`other standard that may have a lower throughput than that of
`the first modulation scheme.
`0026. Although embodiments of the invention are not
`limited in this respect, STA 140 may be a legacy station that
`may not be able to demodulate and/or decode frames trans
`mitted in the first modulation scheme. It will be appreciated
`that AP 110 may be able to use the second modulation
`scheme to communicating traffic to a non-HT station Such as
`legacy STA 140. Additionally or alternatively, high-through
`put STA 120 may not be able to demodulate and/or decode
`frames transmitted in the first modulation scheme using a
`different frame format. However, AP 110 may still be able to
`properly receive frames transmitted by STA 140 and/or STA
`120 using the second modulation Scheme and/or frame
`format.
`0027. In some embodiments, a BSS of communication
`system 100 may include a high throughput AP, e.g., AP 110
`using the first modulation scheme such as MIMO-OFDM,
`and one or more high throughput stations, e.g., STA 120, as
`well as one or more legacy stations, e.g., STA 140 using the
`second modulation scheme, such as OFDM. Optionally, in
`Some embodiments communication system 100 may include
`a protection mechanism to prevent collision of frames. For
`example, when AP 110 transmits traffic including frames of
`the first modulation scheme, it may be necessary for stations,
`including stations adapted to use the second modulation
`scheme, to detect that the wireless medium is busy and not
`attempt to transmit. Although embodiments of the invention
`are not limited in this respect, a protection method may
`depend on an accurate estimate of the frame size and
`transmittal time, as explained in more detail below with
`reference to FIGS. 2-4.
`0028 Reference is made to FIG. 2, which schematically
`illustrates different frame formats that may be used in some
`demonstrative embodiments of the invention, and is helpful
`in understanding alignment requirements in accordance with
`embodiments of the invention. Although embodiments of
`the invention are not limited in this respect, a high-through
`put access point, e.g., AP 110, may be able to transmit and
`receive frames of multiple formats as described below.
`0029. Although embodiments of the invention are not
`limited in this respect, a wireless communication device,
`
`e.g., a station of a WLAN Such as communication system
`100, may be adapted to transmit and/or receive frames of a
`specific format, which may correspond to a certain modu
`lation scheme. The frame formats may include a headings
`and preambles portion 260 and a data portion 270. The
`headings and preambles portion 260 may include one or
`more fields, e.g., a training field and a signal field. The data
`portion 270 may include one or more data symbols.
`0030. For example, a “legacy” format 210 may corre
`spond to OFDM modulation in accordance with 802.11a,
`and a “greenfield format 220 may correspond to MIMO
`OFDM modulation in accordance with 802.11n, as is known
`in the art. Greenfield format 220 may be optimal for a HT
`station, e.g., STA 120. Legacy format 210 may include a
`legacy signal field 213 in the preamble portion 260, which
`may identify the type of modulation scheme used, and may
`include information Such as the data rate and the length of
`the Subsequent data portion 270. The legacy signal field may
`be read by a legacy station, e.g., STA 140. Similarly,
`greenfield format 220 may include a high-throughput signal
`field 223, which may not be readable by a station that is not
`adapted to use the high-throughput modulation, e.g., a
`legacy OFDM station.
`0031. Other frame formats and modulation schemes may
`be used. For example, a “mixed-mode” format 230 may also
`correspond to MIMO-OFDM modulation in accordance
`with 802.11n, but include both a legacy signal field 233 and
`a high-throughput signal field 234. Thus, stations using
`either a first modulation scheme, e.g., MIMO-OFDM, or a
`second modulation scheme, e.g., legacy OFDM, may be able
`to obtain information regarding the data rate and length of
`the subsequent data portion 270.
`0032. In some embodiments, the modulation scheme
`used may include a shortened guard interval (GI) in the data
`symbols of data portion 270. For example, a format 240 may
`be a short GI format corresponding to the regular GI
`greenfield format 220 and a format 250 may be a short GI
`format corresponding to the regular GI mixed-mode format
`230. Although embodiments of the invention are not limited
`in this respect, a data symbol in a regular GI format, e.g.,
`data symbol 239 of mixed-mode format 230, may have a
`length measured in 4 units, e.g., 4 microseconds, whereas a
`data symbol in a short GI format, e.g., data symbol 259 of
`short GI mixed mode-format 250, may have a length mea
`Sured in 3.6 units, e.g., 3.6, microseconds.
`0033. In accordance with the 802.11 set of standards, an
`inter frame space (IFS) may begin following the last data
`symbol in data portion 270 of a transmitted frame. Some
`demonstrative embodiments of the invention may provide a
`method to synchronize the IFS between the transmitting
`station and all receiving stations, so as to start at the same
`time. It will be appreciated that in order to calculate the IFS
`start time, it may be necessary for a receiving station to be
`able to read all relevant parameters of the received frame,
`e.g., as found in the signal field. The IFS start time may vary
`according to the modulation scheme used and the number of
`data symbols in the data portion, which may be of different
`lengths. For example, the IFS start time may depend on the
`frame format (e.g., legacy, mixed-mode, or greenfield), the
`transmission rate (e.g., as indicated in the legacy and HT
`signal fields), data length (e.g., the byte count of the data, as
`indicated in the legacy and HT signal fields), and guard
`
`Exhibit 1011
`Panasonic v. UNM
`IPR2024-00364
`Page 7 of 10
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`US 2007/0204052 A1
`
`Aug. 30, 2007
`
`interval format (e.g., regular or shortened, as indicated in the
`HT signal field). Although embodiments of the invention are
`not limited in this respect, a frame with a regular GI format
`(e.g., mixed-mode format 230 or greenfield format 220) may
`have an IFS start time 280 at a boundary that is an integer
`multiple of 4 units, whereas a short GI format (e.g., mixed
`mode format 250 or short GI greenfield format 240) may
`have an IFS start time 290 that is not located at an integer
`multiple of 4 units. Thus, in a network that includes coex
`istence of different modulation schemes and frame formats,
`e.g., a WLAN such as communication system 100, embodi
`ments of the present invention may enable alignment of the
`IFS start time between transmitted and received frames,
`thereby to prevent frame collision without resorting to a
`costly protection mechanism.
`0034) Reference is again made to FIG. 1. In accordance
`with the 802.11 set of standards, the MAC, e.g., MAC 114
`of AP 110, may perform functionality related to the data link
`layer of the open systems interconnect (OSI) model, as
`known in the art, and prepare data for transmission by the
`PHY, e.g., PHY 113. For example, the MAC functionality
`may include delimiting frames, inserting MAC headers,
`error detection and/or correction functionality, and control
`ling access to the physical medium. The PHY, e.g., PHY 113,
`may include circuitry for encoding, transmission, reception,
`and decoding of wireless signals, packets, and/or frames, as
`part of the physical layer of the OSI model. For example, the
`PHY may receive a PSDU (PHY Service Data Unit) from
`the MAC, and append physical layer dependent information,
`e.g., information relating to the modulation scheme used, in
`the preamble of the PSDU, thereby to form a PPDU (PHY
`protocol data unit) frame Suitable for transmission.
`0035) An interface 115 between MAC 114 and PHY 113
`may use primitives, as known in the art, to communicate
`information between the PHY and the MAC. For example,
`a PHY-CCA.indicate primitive, which may hold a value of
`either busy or idle, may be communicated from the PHY to
`the MAC. Although embodiments of the invention are not
`limited in this respect, the PHY may include a carrier sense
`function to sense the physical (wireless) medium when the
`station is not actively transmitting or receiving. For
`example, the PHY may generate a clear channel assessment
`(CCA) based on a detected energy level. Based on the
`indication from the PHY, the MAC may decide when to send
`a frame for transmission. For example, the MAC may delay
`transmission for a time period corresponding to the IFS,
`which may begin after receiving a PHY-CCA.indicate(idle)
`primitive from the PHY.
`0.036
`Reference is now made to FIG. 3, which schemati
`cally illustrates alignment between a transmitted frame 310
`and a received frame 320 in accordance with one demon
`strative embodiment of the invention. For example, frames
`
`310 and 320 may be of a short GI format, e.g., the mixed
`mode short GI format 250 illustrated in FIG. 2.
`0037. During transmission, the PHY of the transmitting
`station, e.g., PHY 113 of AP 110, may calculate a transmis
`sion time 330 such that the start of the IFS time may be
`aligned with the IFS start time calculated by the PHY of the
`receiving station, e.g., PHY 123 of STA 120 and/or PHY 143
`of STA 140. For example, the receiving PHY may calculate
`the IFS start time according to the information in the signal
`field of the received frame, e.g., legacy signal field 323 or
`high-throughput signal field 324 of received frame 320.
`0038. It will be appreciated that the receiving PHY may
`be adapted to align to the legacy GI format and may thus
`calculate the IFS start time as is known in the art, e.g., at a
`4 unit boundary such as time 340. Thus, in order to align the
`IFS start time, in some embodiments the transmitting PHY
`may calculate the transmission time 330 to similarly end at
`the 4 unit boundary 340, which may belonger than the actual
`end of transmission at time 350. Such an alignment may
`enable synchronization between stations of different modu
`lation schemes.
`0039. Although embodiments of the invention are not
`limited in this respect, transmission time 330 may be cal
`culated using the following equation:
`
`TXTIME = TLEG. PREAMBLE +
`TLEGSIGNAL + THT PREAMABLE + THT SIGNAL +
`
`(Equation 1)
`
`TREG SYM? Ceiling TSGISYM (TREG SYMXNSYM
`9
`9
`
`wherein:
`0040 TLE PREAMBLE is the duration of the legacy
`preamble, e.g., training fields 311 and 312;
`0041) TLEc scNAL is the duration of the legacy signal
`field, e.g., signal field 313:
`0042 THT PREAMBLE is the duration of the HT pre
`amble, e.g., training fields 315 and 316;
`0043) TT scNA is the duration of the HT signal
`field, e.g., signal field 314;
`0044) To s
`is the time required to transmit a data
`symbol having a regular guard interval;
`0045 Tss is the time required to transmit a data
`symbol having a shortened guard interval; and
`0046 Ns is the total number of data symbols in the
`data portion, which may be calculated according to the
`following formula:
`
`8. length +16+ 6. NES
`inSTBC X ceiling
`NSYM = {
`mSTBC NDBPS
`Naybits f NcBPS
`
`When BCC is used
`
`When LDPC is used
`
`(Formula 1)
`
`Exhibit 1011
`Panasonic v. UNM
`IPR2024-00364
`Page 8 of 10
`
`

`

`US 2007/0204052 A1
`
`Aug. 30, 2007
`
`0047 Detailed definitions of the parameters appearing in
`Formula 1 may be found, for example, in section 4 of “Joint
`Proposal: High throughput extension to the 802.11 Standard:
`PHY” which is part of the IEEE 802.11 TGn Joint Proposal
`Technical Specification, dated Jan. 13, 2006. For example:
`0048 length is the number of octets in the data portion
`of the PPDU;
`0049 ms
`is equal to 2 when space time block code
`(STBC) is used, and otherwise 1:
`0050 Ns is the number of encoders used, e.g., 1 or 2:
`0051 Nes is the number of data bits per symbol; and
`0.052 Nes is the number of code bits per symbol.
`0053 Reference is now made to FIG. 4, which schemati
`cally illustrates alignment between a transmitted frame 410
`and received frames 420 and 430 in accordance with another
`demonstrative embodiment of the invention. For example,
`frames 410, 420, and 430 may be of a short GI format, e.g.,
`the short GI greenfield format 240 illustrated in FIG. 2.
`0054 During transmission, the transmitting PHY, e.g.,
`PHY 113 of AP 110, may calculate a transmission time 440
`such that the start of the IFS time may be aligned with the
`IFS start time calculated by the receiving PHY of the
`receiving station, e.g., PHY 123 of STA 120 and/or PHY 143
`of STA 140.
`0055 For example, frame 420 may be received by a
`high-throughput station, e.g., STA 120, which may be
`adapted to use the first modulation scheme that may also be
`used by the transmitting PHY. In such a case, the receiving
`PHY, e.g., PHY 123, may calculate the IFS start time
`according to the information in the high-throughput signal
`field 423 of received frame 420 and may, for example, send
`a PHY-CCA.indicate(idle) primitive at the end of the last
`received data symbol of the frame. In accordance with
`embodiments of the invention, the calculated transmission
`time 440 may be synchronized with the IFS start time 450
`after the last received data symbol, which may not be at a
`4-unit boundary.
`0056.
`In another example, frame 430 may be received by
`a legacy station, e.g., STA 140, which may be adapted to use
`a second modulation scheme that may be different from the
`scheme used by the transmitting PHY. In such a case, the
`receiving PHY, e.g., PHY 143, may not be able to read the
`high-throughput signal field 433 of received frame 430.
`Thus, in some embodiments, the receiving PHY may use a
`carrier sense function to detect that the wireless medium is
`busy based on a detected energy level. As indicated in FIG.
`4, an energy detection period 460 may be aligned with the
`transmission time 440 and IFS start time 450.
`0057. In yet another example, the receiving PHY, e.g.,
`PHY 123 of high-throughput station 120, may be able to
`read-the high-throughput signal field 433, yet not be able to
`demodulate/decode the received frame 430. For example,
`PHY 123 may be adapted to use a regular guard interval
`greenfield format, while the transmitted frame 410 is of a
`short GI greenfield format. In such a case, PHY 123 may
`also use energy detection 460 to align the IFS start time 450
`with the calculated transmission time 440.
`
`(Equation 2)
`
`0058 Although embodiments of the invention are not
`limited in this respect, transmission time 330 may be cal
`culated using the following equation:
`TXTIME=THT PREAMBLE+THT sIGNAL+TscL syMX
`NSYM
`wherein:
`0059) THT PREAMBLE is the duration of the HT pre
`amble, e.g., training fields 411, 412, and 414:
`0060 TT scNAL is the duration of the HT signal
`field, e.g., signal field 413;
`0061 Tis is the time required to transmit a data
`symbol having a regular guard interval;
`0062) Tse sm is the time required to transmit a data
`symbol having a shortened guard interval; and
`0063 Ns is the total number of data symbols in the
`data portion, which may be calculated according For
`mula 1, as detailed above.
`0064 Embodiments of the present invention may be
`implemented by Software, hardware, or by any combination
`of software and/or hardware as may be suitable for specific
`applications or in accordance with specific design require
`ments. Embodiments of the present invention may include
`units and Sub-units, which may be separate of each other or
`combined together, in whole or in part, and may be imple
`mented using specific, multi-purpose or general processors,
`or devices as are known in the art. Some embodiments of the
`present invention may include buffers, registers, storage
`un