Proposed erts ects mechanisms
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Proposed ERTS & ECTS Mechanisms. Author: Matthew Sherman AT&T Labs - Research 180 Park Avenue Florham Park, NJ 07932 973-236-6925 [email protected] Date: May 15, 2001. History of proposal in 01/130r2. Presented (01/157r0) at March ‘01 meeting

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Proposed ERTS & ECTS Mechanisms

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Proposed erts ects mechanisms

Proposed ERTS & ECTS Mechanisms

Author:

Matthew Sherman

AT&T Labs - Research

180 Park Avenue

Florham Park, NJ 07932

973-236-6925

[email protected]

Date: May 15, 2001

Matthew Sherman, AT&T Labs - Research


History of proposal in 01 130r2

History of proposal in 01/130r2

  • Presented (01/157r0) at March ‘01 meeting

    • In straw poll was supported unanimously

  • At 802.11e-QoS level passed with 75%

    • No one spoke for or against proposal

  • At 802.11e level failed with 70%

    • No one spoke for or against proposal

  • Author refrained from speaking so as to allow more time to address EDCF and HCF proposals

  • Have received some side comments and e-mails

    • Most simply required better explanation

    • One (from Matthew Fischer) resulted in some modification of original proposal

Matthew Sherman, AT&T Labs - Research


Changes from 01 130r2 to r5

Changes from 01/130r2 to r5

  • Replaced Broadcast address with TxSup

    • See next slide

  • Removal of open issues

    • Suggest STA which can differentiate NAV set by CFP and Frame Sequence not respond CTS if Frame Sequence

    • Specification of other Extended Capabilities

    • Dropped issue on ACK / Poll response if NAV set

    • Dropped issue of RTS / CTS to gate CFP

  • Modified mapping of extended capabilities

    • Just cleaned up a bit

  • Various minor textual changes

    • Improved prose

    • Closer alignment with P802_11E-Q-D1_0.PDF

Matthew Sherman, AT&T Labs - Research


The txsup address

The TxSup Address

  • Issues with Broadcast address

    • Not sure Legacy STA will set NAV

  • 802.3 uses PAUSE address for similar purpose

    • Well known address reserved for use by 802.3

    • Multicast address

    • Not forwarded by 802.1D Compliant bridges

  • Could reuse PAUSE address for 802.11

  • Could also request new address

    • Left as open issue to use PAUSE address or new address

  • TxSup address would be used the same way as Broadcast address was used in 01/130r2

    • Broadened proposal slightly to allow TxSup with RTS

Matthew Sherman, AT&T Labs - Research


Problem addressed

Problem addressed

  • 802.11e is developing mechanisms to support QoS

  • Many situations when the ability to cause groups of STA to cease transmissions would be useful

    • Accommodate TBTT for Beacon transmission

    • Accommodate protocol enhancements / coexistence

      • HCF / Token passing schemes, Bluetooth, HIPERLAN, etc

    • Hidden terminals

    • Overlapped BSS mitigation

  • Would like technique applied to also work with Legacy STA (LSTA)

  • Would like ability to differentiate between Legacy and groups of 802.11e STA (ESTA)

Matthew Sherman, AT&T Labs - Research


Approach to problem

Approach to Problem

  • Develop method to Set NAV in a STA group

  • Develop method to Reset NAV in a STA group

    • Deferred to later 802.11 meeting

  • Use existing frame formats as much as possible

    • Enhances compatibility with LSTA

Matthew Sherman, AT&T Labs - Research


Approach to problem cont

Approach to Problem (Cont.)

  • Play with usage / interpretation of RTS & CTS

    • Later CF-End as well

  • Have ESTA use Addresses for qualifiers and signaling

    • Apply Duration field based on contents of Addresses

  • Based signaling / qualifiers on Address types

    • Unicast

    • Multicast

    • TxSup (Legacy Transmit Suppression)

  • Chose mappings that are consistent with current usage of address fields in standard

Matthew Sherman, AT&T Labs - Research


Suggested ects mechanisms

Suggested ECTS Mechanisms

  • Enhance CTS (ECTS) usage to allow setting Duration/ID field to any valid Duration value

    • Broadens context for Duration field use

  • Enhance CTS usage to allow any valid address in RA field

  • LSTA will always set NAV for duration indicated

  • Rules for Compliant ESTA will vary (See Chart)

    • Non-compliant ESTA act as LSTA

  • Allow use of PIFS with this message for preferential media access (EAP / EPC only)

Matthew Sherman, AT&T Labs - Research


Map of new capabilities cts

Map of New Capabilities (CTS)

Matthew Sherman, AT&T Labs - Research


Suggested erts mechanism

Suggested ERTS Mechanism

  • Enhance RTS (ERTS) usage to allow setting Duration/ID field to any valid Duration

    • Broadens context for Duration field use

  • Enhance RTS usage to allow group addresses in TA field

  • LSTA will always set NAV for duration indicated

  • Compliant ESTA do not set NAV if not in group

    • Non-compliant ESTA act as LSTA

  • ESTA forward CTS if addressed in RA

  • Allow use of PIFS with this message for preferential media access (EAP / EPC only)

Matthew Sherman, AT&T Labs - Research


Map of new capabilities rts

Map of New Capabilities (RTS)

Matthew Sherman, AT&T Labs - Research


What enhancements accomplish

What Enhancements Accomplish

  • If no LSTA

    • Can set NAV independently in any group of ESTA

    • Some ability to control remote groups via RTS/CTS relay

    • Since can have “Group” of one, can set for single ESTA as well

  • If LSTA are present

    • Must treat as special case

    • Always part of addressed group

Matthew Sherman, AT&T Labs - Research


Comments on mechanisms

Comments on Mechanisms

  • No new frame formats required

  • Fully backward-compatible

  • Additional RTS mappings possible

    • Open to other mappings

    • Open to partial acceptance of mappings

  • Implementation of mechanisms are optional

    • Indicating support of mapping mandatory in ESTA

  • Duration field in other frame types could also be used to reserve channel

    • RTS/CTS seemed most appropriate

Matthew Sherman, AT&T Labs - Research


Comments specific to overlapped bss

Comments specific to Overlapped BSS

  • Goal of new mappings is to allow suppression of groups of terminals in overlap

  • Technique assumes ability to assign STAs to groups

    • Currently those techniques are considered beyond 802.11

    • Techniques are identified in 802.1

  • Best if applied with ability to solicit interference info from STA

    • Which other STA are heard at what power level

    • Mechanisms being developed using Generic Action Frame

    • Existing proposed elements may need to be enhanced

  • IAPP protocol may provide some support for multicast and interference reporting

Matthew Sherman, AT&T Labs - Research


Proposed erts ects mechanisms

Example Applications of

New Mechanisms

Matthew Sherman, AT&T Labs - Research


Example ects usage reduction of tbtt overrun

Legacy Tx

Suppressed

RA=TxSup

Prior TX

ECTS

ETx1

ETx2

ETxN

B

TBTT

NAV Set by Legacy STA

PIFS

Example ECTS UsageReduction of TBTT Overrun*

* Assumes ESTA knows not to overrun TBTT

ETxX are transmissions by ESTA

Matthew Sherman, AT&T Labs - Research


Example ects usage sharing with unknown protocol

RA=Senders Address

Unsolicited Tx Suppressed

Prior Tx

ECTS

Unknown or Foreign Protocol

NAV Set by all STA

Duration Expires

(NAV Resets)

PIFS

Example ECTS UsageSharing with Unknown Protocol

Matthew Sherman, AT&T Labs - Research


Example usage bss overlap

RA=Group 12

Tx to/from ESTA in overlap

BSS1 Group 12 Suppressed

BSS1

Tx12

Tx12

ECTS

Tx1

Tx1

RA=Group 21

BSS2 Group 21 Suppressed

Tx to/from ESTA in overlap

BSS2

ECTS

Tx2

Tx2

Tx21

Tx21

Legend:

Group 12 - ESTA in BSS1 that interfere with BSS2

Group 21 - ESTA in BS21 that interfere with BSS1

Tx12 - Transmissions from any BSS 1 STA

Tx21 - Transmissions from any BSS 2 STA

Tx1 - Transmission from BSS 1 STA not in overlap

Tx2 - Transmission from BSS 2 STA not in overlap

Example Usage - BSS Overlap*

* Multicast addresses for groups 1 and 2 need not be assigned

(Never necessary to suppress groups 1 or 2)

Matthew Sherman, AT&T Labs - Research


Example usage hidden sta suppression

TA=Group A

RA=RSTA

RA=Group A

Hidden STA suppressed

ERTS

ECTS

ERTS

ECTS

Hidden Node

Suppressed

Continued

Suppression

Example UsageHidden STA Suppression*

* Assumes Hidden ESTA is only STA in group to begin with (Group A)

Matthew Sherman, AT&T Labs - Research


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