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Mar 2004
Masahiro TAKAGI, Toshiba
Slide 1
doc.: IEEE 802.11-04/219r0
Submission
Requirements for MAC / PHY Simulation Interface
Masahiro [email protected]
TOSHIBA
Darren [email protected]
TREL
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 2
doc.: IEEE 802.11-04/219r0
Submission
Overview
• The PHY services provided to the 802.11 MAC are specified in Clause 12 of the 802.11 specification [1].
• Inappropriate modeling of the PHY services would affect the results of system simulations. PHY services should be properly modeled in the simulators.
• This presentation reviews the current PHY service specification and proposes the requirements for MAC / PHY interface of the simulators.
• This proposal is independent of whichever PHY abstraction method is chosen.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 3
doc.: IEEE 802.11-04/219r0
Submission
802.11 Protocol Reference Model
• The PLCP (Physical Layer Convergence Protocol) sublayer hides the PMD (Physical Medium Dependent) sublayer from the MAC, and provides PHY-independent services to the MAC through the PHY-SAP.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 4
doc.: IEEE 802.11-04/219r0
Submission
List of PHY service primitivesprimitive name flow parameter value description
PHY_TXSTART.request MAC→PHY TXVECTOR PHY depend start the transmission of an MPDU
PHY_TXSTART.confirm PHY→MAC no N.A. response to PHY_TXSTART.request
PHY_TXEND.request MAC→PHY no N.A. receive the last PHY_DATA.comfirm
PHY_TXEND.confirm PHY→MAC no N.A. response to PHY_TXEND.request
PHY_DATA.request MAC→PHY DATA X'00'-X'FF' (Octet) transfer of an octet of data
PHY_DATA.confirm PHY→MAC no N.A. confirmation of PHY_DATA.request
PHY_DATA.indication PHY→MAC DATA X'00'-X'FF' (Octet) transfer of an octet of data
PHY_RXSTART.indication PHY→MAC RXVECTOR PHY depend receive valid PLCP Header
PHY_RXEND.indication PHY→MAC RXERROR NoError/
completed a reception with or without errors FormatViolation/
CarrierLost/
UnSupportedRate
PHY_CCARESET.request MAC→PHY no N.A. the end of a NAV timer.
PHY_CCARESET.confirm PHY→MAC no N.A. response to PHY_CCARESET.request
PHY_CCA.indication PHY→MAC STATUS BUSY/IDLE report of channel state change
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 5
doc.: IEEE 802.11-04/219r0
Submission
PHY-DATA
• PHY-DATA is used when the MAC transmits or receives an octet of data to or from the PHY.
• Simulators may use a frame level data transfer model between the MAC and PHY, so this octet level data transfer behavior can be safely ignored.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 6
doc.: IEEE 802.11-04/219r0
Submission
PHY-TXSTART
• PHY-TXSTART is used when the MAC requests the PHY to transmit a frame. TXVECTOR specifies the parameters (Rate, Length, etc.) to be used in the transmission.
– TXVECTOR parameter may contain any PHY dependent information which is defined in the relevant specifications (proposal or existing standard).
• The simulator may use PHY dependent parameters in addition to Rate and Length when the MAC requests the PHY to transmit a frame.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 7
doc.: IEEE 802.11-04/219r0
Submission
PHY-TXEND
• PHY-TXEND terminates transmission prematurely.
• Simulations may safely ignore this service.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 8
doc.: IEEE 802.11-04/219r0
Submission
PHY-RXSTART
• PHY-RXSTART is used when the PHY notifies the MAC of the start of a frame reception. RXVECTOR specifies the parameters (Rate, Length, etc.) for the frame reception.– RXVECTOR parameter may contain any PHY dependent
information which is defined in the relevant specifications (proposal or existing standard).
• The simulator may use PHY dependent parameters in addition to Rate and Length when the PHY notifies the MAC of frame reception.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 9
doc.: IEEE 802.11-04/219r0
Submission
PHY-RXEND• Normal frame reception (PHY-RXEND.indication (NoError) with
correct FCS) triggers several events at the MAC.• A frame reception with errors triggers an EIFS at the MAC in the
following cases:– PHY-RXEND.indication (NoError) and FCS check fail at the MAC.– PHY-RXEND.indication (FormatViolation, CarrierLost or
UnsupportedRate) • This service is covered by the existing discussions on PHY abstraction
by the SMSC, as only a ‘Reception successful or unsuccessful’ notification is required by simulation.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 10
doc.: IEEE 802.11-04/219r0
Submission
PHY-CCA
• The MAC uses PHY-CCA to determine if the PHY carrier sense state is idle or busy.
• A simulator should consider all the PHY carrier sense methods (energy, preamble etc.) when determining the setting of PHY-CCA.
• The carrier sense sensitivity level should be appropriately adjusted according to the conditions specified in the relevant proposal or standard.
• PHY-CCA shall stay in the busy state for the frame duration once this value is determined from the information contained in the PLCP header.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 11
doc.: IEEE 802.11-04/219r0
Submission
PHY-CCARESET
• PHY-CCARESET is used when the NAV is reset.
• A simulator should set the PHY carrier sense state to idle if the NAV is reset.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 12
doc.: IEEE 802.11-04/219r0
Submission
PHY-CCA for Coexistence
• Usage models [2] include scenarios for legacy coexistence evaluation – Scenario 9 (Mixed-Mode BSS) (Mandatory)– Scenario 11 (Co-channel legacy BSS) (Mandatory)– Scenario 19 (Point-to-Point Legacy Sharing Throughput Test for
CC 15 (Mandatory) • CCA is the primary MAC deferral mechanism• If proposals include a non backwards compatible PLCP preamble and
header for HT operation, this should affect the CCA sensitivity threshold used during reception by legacy STAs [1].
• Calculation of RX power and knowledge of PLCP compatibility is part of the PHY abstraction, and therefore the state of PHY-CCA should be reported by the PHY abstraction.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 13
doc.: IEEE 802.11-04/219r0
Submission
Conclusion
• Most of the PHY services which would affect simulation results have already been considered in the SMSC.
• CCA at legacy STA should not be overlooked, since it would affect the results of mixed-mode and legacy coexistence scenarios.
• PHY-CCA needs to be determined and reported by the PHY abstraction.
Mar 2004
Masahiro TAKAGI, Toshiba
Slide 14
doc.: IEEE 802.11-04/219r0
Submission
References
• [1] IEEE Wireless LAN Edition -A compilation based on IEEE Std 802.11TM-1999 (R2003) and its amendments-
• [2] Usage Models (11-03/802r12 )
