• ~_)
`
`IEEE P802.lla/D7.0, July 1999
`(Supplement lo IEEE Std 802.l t-1999),
`
`DRAFT Supplement to STANDARD [for]
`Information Technology-
`Telecommunications and information exchange
`between systems-
`Local and metropolitan area networks-Specific Require(cid:173)
`ments -
`Part 11: Wireless LAN Medium Access Control (MAC)
`and Physical Layer (PHY) specifications: High Speed
`Physical Layer in the 5 GHz Band
`
`Sponsor
`
`LAN/MAN Standard Committee
`of the
`IEEE Computer Society
`
`Abstract: Changes and additions to IEEE Std. 802.11 to support the new high rate Physical layer for
`operation in the 5 GHz band are provided.
`
`Copyright© 1999 by the Institute of Electrical and Electronic!) Engineers, Inc.
`345 East 4 7th Street
`New York, NY 10017, USA
`All rights reserved.
`
`This is an unapproved draft of a proposed IEEE Standard, subject to change. Permission is hereby
`granted for IEEE Standards Committee participants to reproduce this document for purposes of
`IEEE standardization activities. If this document is to be submitted to ISO or IEC, notification shall
`be given to the IEEE Copyright Administrator. Permission is also granted for member bodies and
`technical committees of ISO and IEC to reproduce this document for purposes of developing a
`national position. Other entities seeking permission to reproduce portions of this document for
`these or other uses must contact the IEEE Standards Department for the appropriate license. Use
`of information contained in the unapproved draft is at your own risk.
`
`IEEE Standards Department
`Copyright and Permissions
`445 Hoes Lane, P.O. Box 1331
`Piscataway, NJ 08855-1331, USA
`
`Copyright© 1999 IEEE. All rights reserved.
`This is an unaooroved IEEE Standards Draft. subiect to chance.
`
`l
`
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`ERIC-1005
`Ericsson v IV
`Page 1 of 90
`
`

`
`IEEE
`P802.11a/07.0, July 1999
`
`DRAFT SUPPLEMENT TO STANDARD FOR LAN/MAN PART 11: MAC & PHY SPECIFICATIONS:
`
`'
`
`Keywords: 5 GHz, High Speed, LAN, Local Area Network, OFDM, U-Nll, Wireless, Radio frequency
`
`2
`
`Copyright© 1999 IEEE. All rights reserved.
`This Is an unapproved IEEE Standards Draft. subject to change.
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`ERIC-1005 / Page 2 of 90
`
`

`
`HIGH SPEED PHYSICAL LAYER IN THE 5 GHz BAND
`
`IEEE
`P802.11a/D7.0. July 1999
`
`Introduction
`
`This standard is part of a family of standards for Local Area Networks (LANs) and this is a supplement to
`standard for Telecommunications and Infonnation Exchange Between Systems - LAN/MAN Specific
`Requirements - Part 11: Wireless Medium Access Control (MAC) and physical layer (PHY) specifications:
`High Speed Physical Layer in the 5 GHz band
`
`Participants
`
`At the time the draft of this standard was sent to sponsor ballot, the IEEE 802.11 working group had the fol(cid:173)
`lowing voting members:
`
`Vic Hayes, Chair
`Stuart J. Kerry, Vice Chair
`Al Petrick, Co-Vice Chair
`George Fishel, Secretary
`
`Bob O'Hara, Chair and editor 802.11-rev
`Allen Heberling, State-diagram editor
`Michael Fischer, State-diagram editor
`Dean M. Kawaguchi, Chair PHY group
`David Bagby, Chair MAC group
`
`Naftali Chayat, Chair Task Group a
`Hitoshi Takanashi, Editor 802.11 a
`
`John Fakatselis, Chair Task Group b
`
`Carl F. Andren, Editor 802.11 b
`
`Masaharu Mori
`Masahiro Morikura
`Richard van Nee
`Erwin R. Noble
`Tomoki Ohsawa
`Kazuhiro Okanoue
`Richard H. Paine
`Roger Pandanda
`Victoria M. Poncini
`Gregory S. Rawlins
`Stanley A. Reible
`Frits Riep
`William Roberts
`Kent G. Rollins
`
`Jeff Abramowitz
`Reza Ahy
`Keith B. Amundsen
`James R. Baker
`Kevin M. Barry
`Phil Belanger
`John Biddick
`Simon Black
`Timothy J. Blaney
`Jan Boer
`Ronald Brockmann
`Wesley Brodsky
`John H. Cafarella
`Wen-Chiang Chen
`Ken Clements
`Wim Diepstraten
`Peter Ecclesine
`Richard Eckard
`Darwin Engwer
`Greg Ennis
`Jeff Fischer
`John Fisher
`Ian Gifford
`Motohiro Gochi
`
`Tim Godfrey
`Steven D. Gray
`Jan Haagh
`Karl Hannestad
`Kei Hara
`Chris Heegard
`Robert Heile
`Juha Heiskala
`Maarten Hoeben
`Masayuki Ikeda
`Donald C. Johnson
`Tai Kaitz
`Ad Kamerman
`Mika Kasslin
`Patrick Kinney
`Steven Knudsen
`Bruce P. Kraemer
`David S. Landeta
`James S. Li
`Stanley Ling
`Michael D. Mcinnis
`Gene Miller
`Akira Miura
`Henri Moelard
`
`Copyright© 1999 IEEE. All rights reserved.
`Thi~ is ;m 11m1nnmvP.rl IEEE SllmrlRrrls DrRft. s11hiP.r.t to r.hRnOP..
`
`·'
`
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`ERIC-1005 / Page 3 of 90
`
`

`
`,
`
`IEEE
`P802.11a/D7.0, July 1999
`
`DRAFT SUPPLEMENT TO STANDARD FOR LAN/MAN PART 11: MAC & PHY SPECIFICATIONS:
`
`The following persons were on the balloting committee:
`This section is usually supplied
`by IEEE Balotting Center staff.
`
`4
`
`Copyright© 1999 IEEE. All rights reserved.
`This is an unapproved IEEE Standards Draft, subject to change.
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`ERIC-1005 / Page 4 of 90
`
`

`
`HIGH SPEED PHYSICAL LAYER IN THE 5 GHz BAND
`
`'
`
`'
`
`IEEE
`P802.11a/D7.0, July 1999
`
`Contents
`
`4.
`
`Abbreviations and acronyms ............................................................................................................... 7
`
`9. I Multirate support .......................................................................................................................... 7
`
`17.
`
`OFDM physical layer specification for the 5 GHz band ................................................................... 10
`
`17. I Introduction ................................................................................................................................ l 0
`17.l.I Scope .......................................................................................................................... 10
`17.l.2 OFDM physical layer functions ................................................................................. 10
`17 .2 OFDM PHY specific service parameter lists ............................................................................. 11
`17 .2.1
`Introduction ................. : .............................................................................................. 11
`17.2.2 TXVECTOR parameters ............................................................................................ 11
`17.2.3 R.XVECTOR parameters ........................................................................................... 12
`17 .3 OFDM physical layer convergence procedure sublayer. ........................................................... 13
`17 .3.1
`Introduction ................................................................................................................ 13
`17.3.2 Physical layer convergence procedure frame format.. ............................................... 13
`17.3.3 PLCP preamble (SYNC) ............................................................................................ 19
`17 .3.4 Signal field (SIGNAL) ............................................................................................... 20
`17.3.5 DATA field ................................................................................................................ 22
`17.3.6 Clear channel assessment (CCA) ............................................................................... 32
`17.3. 7 PLCP data modulation and modulation rate change .................................................. 32
`17.3.8 PMD Operating specifications general ...................................................................... 32
`17.3.9 PMD transmit specifications ...................................................................................... 36
`17.3.10 PMD receiver specifications ...................................................................................... 39
`17.3.11 PLCP transmit procedure ........................................................................................... 41
`17.3.12 PLCP receive procedure ............................................................................................ 43
`17.4 OFDM physical layer management entity (PLME) ................................................................... 46
`17.4. l PLME_SAP sublayer management primitives .......................................................... 46
`17.4.2 OFDM physical layer management information base ............................................... 46
`17.4.3 OFDM TXTIME calculation ..................................................................................... 48
`17.4.4 OFDM PHY characteristics ....................................................................................... 48
`.17.5 OFDM physical medium dependent sublayer ........................................................................... 49
`17 .5.1 Scope and field of application ................................................................................... 49
`17.5.2 Overview of service ................................................................................................... 50
`17.5.3 Overview of interactions ............................................................................................ 50
`17.5.4 Basic service and options ........................................................................................... 50
`17.5.5 PMD_SAP detailed service specification .................................................................. 51
`
`Annex A
`
`..................................................................................................................................................... 56
`
`Annex D
`
`..................................................................................................................................................... 61
`
`Annex G
`
`..................................................................................................................................................... 64
`
`#Editor's note:
`
`Clause 4, 9.1 and 17 in this supplement will be inserted into the based standard as an additional PHY speci(cid:173)
`fication for 5 GHz U-NII band.
`
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`Copyright© 1999 IEEE. All rights reserved.
`This is :m 11n:mnrnvArt IEEE Sl'tnrfarrts Or'tft. s11hiAr:I In r:h'tnaA.
`
`ERIC-1005 / Page 5 of 90
`
`

`
`IEEE
`P802.11a/07.0, July 1999
`
`DRAFT SUPPLEMENT TO STANDARD FOR LAN/MAN PART 11: MAC & PHY SPECIFICATIONS:
`
`'
`
`There are three annexes included in this supplement. Following are instructions to merge the infonnation in
`these annexes into the base document.
`
`Annex A: Section A.4.3 of this annex in the supplement shows the table of Annex A.4.3 ("JUT configura-
`tion") of the base document as it would appear after the introduction of the OFDM IUT configuration item.
`The contents of the table at "Item •CF6" and below shown in the table of Annex A.4.3 of this supplement
`should be appended to the corresponding table in Annex A.4.3 of the base document. The entire table of An-
`nex A.4.8 ("Orthogonal Frequency Division Multiplex PHY functions") should be appended to the end (i.e.,
`after subsection A.4.7) of Annex A of the base document.
`
`Annex D: This annex in the supplement contains additions to be made to Annex D ("ASN.1 encoding of the
`MAC and PHY MIB") of the base document. There are 5 subsections (numbered 1 through 5 inclusive) that
`provide instructions to merge the provided infonnation into the appropriate locations in Annex D of the base
`document.
`
`Annex G: This annex is a new annex in the standard. The purpose of Annex G is to provide an example of en-
`coding a frame for the OFDM PHY described in Clause 17, including all intermediate stages. There are 8 subsec-
`tions.
`
`6
`
`Copyright© 1999 IEEE. All rights reserved.
`This is an unapproved IEEE Standards Draft, subject to change.
`
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`ERIC-1005 / Page 6 of 90
`
`

`
`HIGH SPEED PHYSICAL LAYER IN THE 5 GHz BAND
`
`IEEE
`PB02.11a/07.0, July 1999
`
`DRAFT Supplement to STANDARD [for] Information
`Technology-
`Telecommunications and information exchange between
`systems-
`Local and metropolitan area networks-Specific Require(cid:173)
`ments -
`Part 11: Wireless LAN Medium Access Control (MAC)
`and Physical Layer (PHY) specifications: High Speed
`Physical Layer in the 5 GHz Band
`
`[This supplement is based on the current edition of IEEE Std 802.11, 1999 Edition.]
`
`NOTE- The editing instructions contained in this supplement define how to merge the material contained
`herein into the current edition of IEEE Std 802.11, 1997 Edition to form the new comprehensive standard as
`created by the addition of IEEE Std 802.1 la, 1999.
`
`The editing instructions are shown in bold italic. Three editing instructions are used: change, delete, and
`insert. Change is used to make small corrections in existing text or tables. The editing instruction specifies
`the location of the change and describes what is being changed either by using strikedtr01tgh (to remove old
`material) or underscore (to add new material). Delete removes existing material. Insert adds new material
`without disturbing the existing material. Insertions may require renumbering. If so, renumbering instructions
`are given in the editing instruction. Editorial notes will not be carried over into future editions.
`
`Cha11ge the following paragraphs as i11dicated:
`
`4. Abbreviations and acronyms
`
`Insert the following abbreviations alphabetically in the list in 4.
`
`C-MPDU=Coded MPDU
`Gl=Guard Interval
`OFDM=Orthogonal Frequency Division Multiplexing
`U-NII=Unlicensed National Infonnation Infrastructure
`FFT=Fast Fourier Transform
`IFFT=lnverse Fast Fourier Transform
`QAM=Quadrature Amplitude Modulation
`BPSK=Binary Phase Shift Keying
`QPSK=Quadrature Phase Shift Keying
`
`9.1 Multirate support
`
`Appe11d thefollowi11g text at the end of subclause 9.6 of current edition of IEEE Std 802.11, 1997 Edition:
`
`Copyright© 1999 IEEE. All rights reserved.
`Thi!': i.• ;m 11n1=1nnrnvP.rl IEEE St;:inrfan1~ Drnft. ~11hiP.r.t tn r.h;:inaP..
`
`7
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`
`ERIC-1005 / Page 7 of 90
`
`

`
`IEEE
`P802.11a/07.0, July 1999
`
`DRAFT SUPPLEMENT TO STANDARD FOR LAN/MAN PART 11: MAC & PHY SPECIFICATIONS:
`
`'
`
`For the 5 GHz PHY, the time required to transmit a frame, for use in the Duration/ID field, is detennined
`using the PLME-TXTIME.request primitive and the PLME-TXTlME.confirrn primitive, the calculation
`method ofTXTlME duration is defined in subclause 17.4.3.
`
`10.4 PLME SAP interface
`
`Append the following text at the end of subclause 10.4 of current edition of IEEE Std 802.11, 1999 Edi-
`tion.
`
`Reniove the references to aMPDUDurationFactor from 10.4.3.1.
`
`Insert the following subclauses at the end of 10.4:
`
`10.4.6 PLME-TXTIME.request
`
`10.4.6.1 Function
`
`This primitive is a request for the PHY to calculate the time that will be required to transmit onto the wire-
`less medium a PPDU containing a specified length MPDU and using a specified format, data rate, and sig-
`~~
`
`10.4.6.2 Semantics of the service primitive
`
`The primitive provides the following parameters:
`
`PLME-TXTIME.request(TXVECTOR)
`
`The TXVECTOR represents a list of parameters that the MAC sublayer provides the local PHY entity in
`order to transmit an MPDU, as further described in 12.3.4.4 and the clause defining the local PHY entity.
`
`10.4.6.3 When generated
`
`This primitive is issued by the MAC sublayer to the PHY entity whenever the MAC sublayer needs to deter-
`mine the time required to transmit a particular MPDU.
`
`10.4.6.4 Effect of receipt
`
`The effect of receipt of this primitive by the PHY entity shall be to generate a PHY-TXTIME.confinn prim-
`itive which conveys the required transmission time.
`
`10.4.7 PLME-TXTIME.confirm
`
`10.4.7.l Function
`
`This primitive provides the time that will be required to transmit the PPDU described in the corresponding
`PLME-TXTIME.request.
`
`10.4.7.2 Semantics of the service primitive
`
`The primitive provides the following parameters:
`
`8
`
`Copyright© 1999 IEEE. All rights reserved.
`This is an unapproved IEEE Standards Draft, subject to change.
`
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`ERIC-1005 / Page 8 of 90
`
`

`
`HIGH SPEED PHYSICAL LAYER IN THE 5 GHz BAND
`
`PLME-TXTIME.confinn(TXTIME)
`
`'
`
`IEEE
`P802.11a/D7.0. July 1999
`
`The TXTIME represents the time in microseconds required to transmit the PPDU described in the corre-
`sponding PLME-TXTIME.request. If the calculated time includes a fractional microsecond, the TXTIME
`value is rounded up to the next higher integer.
`
`10.4. 7 .3 When generated
`
`This primitive is issued by the local PHY entity in response to a PLME-TXTIME.request.
`
`10.4.7.4 Effect of receipt
`
`The receipt of this primitive provides the MAC sublayer with the PPDU transmission time.
`
`\
`
`Copyright© 1999 IEEE. All rights reserved.
`Thi<1 i.<1 Rn 11n1wnrowul IEEE SIAncfarns Dmft. s11hiP.r.l to r.hAnaP..
`
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`ERIC-1005 / Page 9 of 90
`
`

`
`• ~ ,,
`
`'---..../
`
`DRAFT SUPPLEMENT TO ST AN OARD FOR LAN/MAN PART 11: MAC & PHY SPECIFICATIONS:
`
`IEEE
`P802.11a/D7.0, July 1999
`
`17. OFDM physical layer specification for the 5 GHz band
`
`The whole clause Ii is added to the base standard as clause 17.
`
`17.1 Introduction
`
`This clause specifies the Physical Layer Entity for an Orthogonal Frequency Division Multiplexing (OFDM)
`system and the additions that have to be made to the base standard to accommodate the OFDM PHY. The
`Radio Frequency LAN system is initially aimed for the 5.15-5.25, 5.25-5.35 and 5.725-5.825 GHz U-NII
`bands as provided in the USA according to Code of Federal Regulations, Title 47, Section 15.407. The
`OFDM system provides a wireless LAN with data payload communication capabilities of 6, 9, 12, 18, 24,
`36, 48 and 54 Mbit/s. The support of transmitting and receiving at data rates of 6, 12 and 24 Mbit/s is man(cid:173)
`datory. The system uses 52 subcarriers which are modulated using Binary or Quadrature Phase Shift Keying
`(BPSK/QPSK), 16-Quadrature Amplitude Modulation (16-QAM) or 64-Quadrature Amplitude Modulation
`(64-QAM). Forward error correction coding (convolutional coding) is used with a coding rate of 1/2, 2/3 or
`3/4.
`
`17.1.1 Scope
`
`This subclause describes the physical layer services provided to the 802.11 wireless LAN MAC by the 5
`GHz (bands) OFDM system. The OFDM PHY layer consists of two protocol functions:
`
`a) A physical layer convergence function which adapts the capabilities of the physical medium depen-
`dent system to the Physical Layer service. This function is supported by the Physical Layer Conver-
`gence Procedure (PLCP) which defines a method of mapping the 802.11 PHY sublayer Service Data
`Units (PSDU) into a framing format suitable for sending and receiving user data and management
`information between two or more stations using the associated physical medium dependent system.
`b) A Physical Medium Dependent (PMD) system whose function defines the characteristics and
`method of transmitting and receiving data through a wireless medium between two or more stations
`each using the OFDM system.
`
`17.1.2 OFDM physical layer functions
`
`The 5 GHz OFDM PHY architecture is depicted in the reference model shown in Figure 11 of subclause 5.8.
`The OFDM physical layer contains three functional entities: the physical medium dependent function, the
`physical layer convergence function and the layer management function. Each of these functions is
`described in detail in the following subclauses.
`
`The OFDM Physical Layer service is provided to the Medium Access Control through the physical layer
`service primitives described in clause 12.
`
`17.1.2.1 Physical layer convergence procedure sublayer
`
`In order to allow the 802.11 MAC to operate with minimum dependence on the PMD sublayer, a physical
`layer convergence sublayer is defined. This function simplifies the physical layer service interface to the
`802.11 MAC services.
`
`17.1.2.2 Physical medium dependent sublayer
`
`The physical medium dependent sublayer provides a means to send and receive data between two or more
`stations. This subclause is concerned with the 5 GHz band using OFDM.
`
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`
`Copyrighl © 1999 IEEE. All righls reserved.
`This is an unapproved IEEE Standards Draft, subject to change.
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`ERIC-1005 / Page 10 of 90
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`HIGH SPEED PHYSICAL LAYER IN THE 5 GHz BAND
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`17.1.2.3 Physical layer management entity (LME)
`
`IEEE
`P802.11a/D7.0, July 1999
`
`The Physical LME performs management of the local Physical Layer Functions in conjunction with the
`MAC Management entity.
`
`17.1.2.4 Service specification method
`
`The models represented by figures and state diagrams are intended to be illustrations of the functions pro·
`vided. It is important to distinguish between a model and a real implementation. The models are optimized
`for simplicity and clarity of presentation, the actual method of implementation is left to the discretion of the
`802.11 OFDM PHY compliant developer.
`·
`
`The service of a layer or sublayer is the set of capabilities that it offers to a user in the next higher layer (or
`sublayer). Abstract services are specified here by describing the service primitives and parameters that char·
`acterize each service. This definition is independent of any particular implementation.
`
`17 .2 OFDM PHY specific service parameter lists
`
`17.2.1 Introduction
`
`The architecture of the 802.11 MAC is intended to be physical layer independent. Some physical layer
`implementations require medium management state machines running in the medium access control sub·
`layer in order to meet certain PMD requirements. These physical layer dependent MAC state machines
`reside in a sublayer defined as the MAC subLayer Management Entity (MLME). The MLME in certain
`PMD implementations may need to interact with the Physical LME (PLME) as part of the normal PHY SAP
`primitives. These interactions are defined by the Physical Layer Management Entity parameter list currently
`defined in the PHY Service Primitives as TXVECTOR and RXVECTOR. The list of these parameters and
`the values they may represent are defined in the specific physical layer specifications for each PMD. This
`subclause addresses the TXVECTOR and RXVECTOR for the OFDM PHY.
`
`17.2.~ TXVECTOR parameters
`
`following parameters are defined as part of the TXVECTOR parameter
`The
`PHY-TXSTART.request service primitive.
`
`list
`
`in
`
`the
`
`Table 76-TXVECTOR parameters
`
`Parameter
`
`Associate Primitive
`
`Value
`
`LENGTH
`
`PHY-TXSTART.request (TXVECTOR)
`
`l-4095
`
`DATATRATE
`
`PHY-TXSTART.request (TXVECTOR)
`
`SERVICE
`
`PHY-TXST ART.request (TXVECTOR)
`
`6, 9, 12, 18, 24, 36, 48 and 54
`(support of6, 12 and 24 data rates is mandatory)
`
`scrambler initialization 7 null bits + 9 reserved
`null bits
`
`TXPWR_LEVEL
`
`PHY· TXST ART.request (TXVECTOR)
`
`1-8
`
`17.2.2.1 TXVECTOR LENGTH
`
`The allowed values for the LENGTH parameter are in the range from I to 4095. This parameter is used to
`indicate the number of octets in the MPDU which the MAC is currently requesting the PHY to transmit.
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`Copyright© 1999 IEEE. All rights reserved.
`This is an unannmvAcl IEEE Stanclarrl.• Draft . .:11hiP.r.I tn r.hanoA.
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`II
`
`ERIC-1005 / Page 11 of 90
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`

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`'
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`'
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`IEEE
`P802.11a/07.0, July 1999
`
`DRAFT SUPPLEMENT TO STANDARD FOR LAN/MAN PART 11: MAC & PHY SPECIFICATIONS:
`
`This value is used by the PHY to detennine the number of octet transfers which will occur between the
`MAC and the PHY after receiving a request to start the transmission.
`
`17.2.2.2 TXVECTOR DATARATE
`
`The DATARATE parameter describes the bit rate at which the PLCP shall transmit the PSDU. Its value can
`be any of the rates as defined in Table 76. Data rates of 6, 12 and 24 shall be supported, the other rates may
`be supported.
`
`17.2.2.3 TXVECTOR SERVICE
`
`The SERVICE parameter consists of 7 null bits used for the scrambler initialization and 9 null bits reserved
`for future use.
`
`17.2.2.4 TXVECTOR TXPWR_LEVEL
`
`The allowed value for the TXPWR_LEVEL parameter are in the range from l to 8. This parameter is used to
`indicate, which of the available TxPowerLevel attributes defined in the MIB shall be used for the_ current
`transmission.
`
`17.2.3 RXVECTOR parameters
`
`The following parameters listed in Table 77 are defined as part of the RXVECTOR parameter list in the
`PHY -RXST ART. indicate service primitive.
`
`Table 77-RXVECTOR Parameters
`
`Parameter
`
`Associate Primitive
`
`Value
`
`LENGTH
`
`RSSI
`
`DAT ARA TE
`
`SERVICE
`
`PHY-RXSTART.indicate
`
`1-4095
`
`PHY-RXSTART.indicate
`(RXVECTOR)
`
`PHY-RXSTART.request
`(RX VECTOR)
`
`0- RSSI Max
`
`6, 9, 12, 18, 24, 36, 48 and 54
`
`PHY-RXST ART .request
`(RXVECTOR)
`
`null
`
`17.2.3.1 RXVECTOR LENGTH
`
`The allowed values for the LENGTH parameter are in the range from I to 4095. This parameter is used to
`indicate the value contained in the LENGTH field which the PLCP has received in the PLCP Header. The
`MAC and PLCP will use this value to determine the number of octet transfers that will occur between the
`two sublayers during the transfer of the received PSDU.
`
`17.2.3.2 RXVECTOR RSSI
`
`The allowed values for the Receive Signal Strength Indicator (RSSI) parameter are in the range from 0
`through RSSI Max. This parameter is a measure by the PHY sublayer of the energy observed at the antenna
`used to receive the current PPDU. RSSI shall be measured during the reception of the PLCP Preamble. RSSJ
`
`12
`
`Copyright© 1999 IEEE. All rights reserved.
`This is an unapproved IEEE Standards Draft, subject to change.
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`ERIC-1005 / Page 12 of 90
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`

`
`HIGH SPEED PHYSICAL LAYER IN THE 5 GHz BAND
`
`IEEE
`P802.11a/D7.0, July 1999
`
`is intended to be used in a relative manner and it shall be a monotonically increasing function of the received
`power.
`
`17.2.3.3 DATARATE
`
`DA TARA TE shall represent the data rate at which the current PPDU was received. The allowed values of the
`DATARATE are 6, 9, 12, 18, 24, 36, 48 or 54.
`
`17.2.3.4 SERVICE
`
`The SERVICE field shall be null.
`
`17.3 OFDM physical layer convergence procedure sublayer
`
`17.3.1 Introduction
`
`This subclause provides a convergence procedure in which PSDUs are converted to and from PPDUs. Dur(cid:173)
`ing transmission, the PSDU shall be provided with a PLCP preamble and header to create the PPDU. At the
`receiver, the PLCP preamble and the header are processed to aid in demodulation and delivery of the PSDU.
`
`17.3.2 Physical layer convergence procedure frame format
`
`Figure 107 shows the format for the PPDU including the OFDM PLCP preamble, the OFDM PLCP header,
`PSDU, the tail bits and pad bits. The PLCP header contains the following fields: LENGTH, RATE, a
`reserved bit, an even parity bit and the SERVICE field. In terms of modulation, the LENGTH, the RATE, the
`reserved bit and the parity bit (with 6 "zero" tail bits appended) constitute a separate single OFDM symbol,
`denoted SIGNAL, which is transmitted with the most robust combination of BPSK modulation and coding
`rate of R=l/2. The SERVICE field of the PLCP header and the PSDU (with 6 "zero" tail bits and pad bits
`appended), denoted as DAT A, are transmitted at the data rate described in the RATE field and may constitute
`multiple OFDM symbols. The tail bits in the SIGNAL symbol enable decoding of the RATE and the
`LENGTH fields immediately after the reception of the tail bits. The RA TE and the LENGTH are required
`for decoding the DAT A part of the packet. In addition, the CCA mechanism can be augmented by predicting
`the duration of the packet from the contents of the RATE and the LENGTH fields, even if the data rate is not
`supported by the station. Each of these fields is described in detail in subclause 17.3.3, 17.3.4 and 17.3.5.
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`Copyright© 1999 IEEE. All rights reserved.
`Thl<; is Rn 11n11nnrnvP.c1 IEEE St1mc1Rrc1s DrRft. s11hiAr.t tn r.hRnoP..
`
`ERIC-1005 / Page 13 of 90
`
`

`
`IEEE
`P802.11a/D7.0, July 1999
`
`DRAFT SUPPLEMENT TO STANDARD FOR LAN/MAN PART 11: MAC & PHY SPECIFICATIONS:
`
`'
`
`PLCP Header
`
`RATE Reserved LENGTH Parity Tail
`4 bits
`1 bit
`12 bits
`1 bit
`6 bits
`.......
`
`SERVICE
`16 bits
`
`PSDU
`
`Tail Pad bits
`6 bits
`
`.......
`
`.......
`
`...._
`
`.......
`
`"t
`
`Coded/OFDM
`(BPSK, r=l/2)
`
`Coded/OFDM
`(RATE is indicated in SIGNAL)
`
`,~----~~~-t1---1~--~~~~~~~~~~~~~ .....
`
`PLCP preamble
`12 symbols
`
`SIGNAL
`One OFDM s mbol
`
`DATA
`variable number of OFDM s mbols
`
`Figure 107-PPDU frame format
`
`17.3.2.1 Overview of the PPDU encoding process
`
`The encoding process is composed of many steps, involving large amount of details to be described fully.
`The following overview intends to facilitate the understanding of the details described in the sequel.
`
`I) Produce the PLCP preamble field, composed of 10 repetitions of"short training sequence" (used for AGC
`convergence, diversity selection, timing acquisition and coarse frequency acquisition in the receiver) and of
`two repetitions of a "long training sequence" (used for channel estimation and fine frequency acquisition in
`the receiver), preceded by a Guard Interval. Refer to subclause 17.3.3 for details.
`
`2) Produce the PLCP Header field from the RATE, LENGTH and SERVICE fields of the TXVECTOR, by
`filling the appropriate bit fields. The RA TE and LENGTH fields of the PLCP Header are encoded by a con-
`volutional code at rate of R=l/2, and are subsequently mapped onto a single BPSK encoded OFDM symbol,
`denoted as SIGNAL symbol. In order to facilitate a reliable and timely detection of the RATE and LENGTH
`fields, 6 "zero" tail bits are inserted into the PLCP header. The encoding of the SIGNAL field into an OFDM
`symbol follows the same steps of convolutional encoding, interleaving, BPSK modulation, pilot insertion,
`Fourier transform and prepending a Guard Interval, as described subsequently for data transmission at 6
`Mbit/s. The contents of the SIGNAL field is not scrambled. Refer to subclause 17.3.4 for details.
`
`3) Calculate from RA TE field of the TXVECTOR the number of data bits per OFDM symbol (N DBPs), the
`coding rate (R), the number of bits in each OFDM subcarrier (NnPSd and the number of coded bits per
`OFDM symbol (Ncops)· Refer to 17.3.2.2 for details.
`
`4) Take the PSDU and append it to the SERVICE field of the TXVECTOR. Extend the resulting bit string
`with "zero" bits, at least 6 bits, so that the resulting length will be a multiple of NDBPS· The resulting bit
`string constitutes the DATA part of the packet. Refer to subclause 17 .3.5.3 for details.
`
`5) Initiate the scrambler with a pseudorandom non-zero seed, genera